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6-1-1945 Rammed Earth for Farm Buildings R.L. Patty

L.W. Minium

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Recommended Citation Patty, R.L. and Minium, L.W., "Rammed Earth Walls for Farm Buildings" (1945). Bulletins. Paper 277. http://openprairie.sdstate.edu/agexperimentsta_bulletins/277

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Agricultural Engineering Department AGRICULTURAL EXPERIMENT STA no N' 'SOUTH DAKOTA STATE COLLEGE' Brookings," South Dakota Third Edition This is the third edition of Experiment Station Bulletin 277. It is slightly revised, Most of the material on protective coverings for rammed earth walls, which was former­ ly included in this bulletin, has been re­ moved since it is now included in Experi­ ment Station Bulletin 336 entitled "Paints and Plasters for Rammed Earth Walls" pub­ lished in 1940.

Explanation of Cover Cut The South Dakota Poultry Built with Walls of Rammed Earth. The house was built on the State College Poultry Farm in 1932 and stuccoed in 1934. Both walls and stucco still are standing sat­ isfactorily and without any maintenance or repair cost. The crack in the stucco at the front corner was caused by extending the stucco from the to the founda­ tion without leaving a joint. The two have a different coefficient of expansion. It cost $19.50 to stucco this house. The material cost $7.50 and the labor $12.00. Table of Contents PAGE In trod ucti on ------_____ 5 Other Types of Earth Walls Compared______------5 Insulating and Quality of Rammed Earth Walls ------6 Methods Used for Testing and Walls ______.______8 Test Blocks and Beams______------·______3 Testing the Soil for Moisture______------9 Testing the Blocks for Strength in Compression ------______9 Used for Standard in Tests______------·_____ 10 Mechanical Analysis of Soil Samples ______------______11 Relation of Content, Moisture, and Shrinkage in Soils for Rammed Earth Work ------· _____ 11 Moisture and Sand______------·______11 Moisture and Strength______------_____ 1? Sand and Strength______12 Moisture and Shrinkage------. ______------____ 12 Sand and Shrinkage·------·______------13 The Unit Weight of Soils in Rammed Earth______··---- 14 Optimum Moisture in Soil for Weather Resistance______15 Kind of Soil Best Adapted to Rammed Earth ______16 A Simple Test of Soil for Rammed Earth Work______17 Effect of Reramming Soil in Pise' Construction______18 Effectof Freezing Weather upon Rammed Earth Construction Work______18 Care and Mixing of the Soil for Rammed Earth Work______18 Screening the Soil for Rammed Earth Work______-----"------18 Effectof Depth of Block upon the Strength in Compression______20 Resistance of Rammed Earth Walls to Weathering______20 Protective Outside Coverings for Pise' Walls ______22 Stucco ------22 Less Expensive Plasters______------23 Paints ------______23 Inside Wall Coverings______. ______2 4 Weight, Shape and Type of Hand Rammers ______24 Intensity of the Tamping Stroke______26 Size of Aggregate in Soil for Rammed Earth Construction and Its Effectupon the Compressive Strength ______------28 Effect of Adding Lime______------... -----· 29 Effectof Mixing Fiber with Rammed Earth upon Its Strength in Compression 30 Rate of Drying Out of Rammed Earth as Affected by an Adm'xture of Fiber Such as Straw______------31 Reinforcing in Rammed Earth Construction ______33 Foundations for Rammed Earth Walls ______------______35 Waterproofing the Tops of Foundations------______37 Forms for Pise' Walls______37 Oiling the Forms ______------· ------·______40 Leveling the Forms------40 Building a Rammed Earth Poultry House ______40 The Soil Used··------·------·------4 2 Building the Wall______------·______4 3 Filling the Forms______------·------______4 3 Protecting the Walls During Construction------_____ 44 Repair and Retouching of the Walls______------· 46 Rammed Earth Blocks for Building Walls ______48 Size and Shape of the Blocks______48 Mortar Used for Laying up Wall of Rammed Earth Blocks------·------49 Forms for Making Rammed Earth Blocks______50 Walls of Block Compared to Monolithic Vvalls ______50 Thorough Distribution of Moisture Through the Soil Adds to the Quality of the Rammed Earth W alL ______53 Comparison of a Puddled Earth or with a Rammed Moist Earth--In Compressive Strength______5 3 A Cinder Admixture StudY------__ 56 A Few Brief Building Specifications______57 Summary and Comments ------··------59 A List of Reference Books and Literature on Pise' Construction______63 Rammed Earth Walls for Farm Buildings By RALPH L. PATTY and L. W. MrnrnM1

Department of Agricultural Engineering State College Experiment Station, Brookings, S. D.

Introduction

Rammed earth walls are made by ·ram­ were in use 25 0 years after completion. It ming ordinary moist earth into forms. The was introduced into by the Romans walls are rammed in place directly upon the and later adopted in ." building and in sections. The Buildings of these walls have been used in forms are similar to those used for concrete the also to a limited extent. Ac­ construction except that they must be much cording to California Experiment Station stronger and heavier. The ·ramming may be Bulletin No. 47 2 by J. D. Long, some of the done either by hand or by mechanical settlers of our early colonies built of this ma­ power. In reading this bulletin it will be terial. One two-story rammed earth resi­ very helpful if the table of contents is con­ dence now in use in Washington, D. C., is sulted for the subjects. said to have been erected in 17 73, and a The purpose of this experimental study of "' modern residence was built of this material "pise construction was to secure definite in Washington within the past few years by and reliable information with which we Dr. H.B. Humphrey. could answer the many inquiries concerning it that were coming to the South Dakota Other Types of Earth Walls Compared. Agricultural Experiment Station. The wide There are several types of earth wall con­ range of soil types over the state of South struction besides the pise' or rammed earth Dakota made it impossible to make reliable with which this study deals. walls, as recommendations as to its use for this con­ the term is generally understood and de­ struction without a careful and detailed fined, are made of a wet mixture of study of South Dakota soils, and of soils in earth or mud. Adobe walls should not be general, for this purpose. This is a progress confused with rammed earth as they are· report. quite different, the adobe being mud-like Earth construction for building walls is while the pise' walls are rammed moist not a new idea. In fact, it is ages old. Build-· earth. The most common adobe construction ings were built of earth centuries ago in Eu­ is with blocks. The mud is pressed and mold- rope, and while the methods used differed ed into large usually 18 inches long widely, some of this construction was of by 12 inches wide by 4 inches thick. These rammed earth.It is claimed that it was used are often reinforced with straw, and after by the early Romans and was introduced they are molded they are set out to dry. When they are properly cured they are laid into F�ance by them. The following para­ graph 1s taken from Farmers' Bulletin No. into a wall in the same way as concrete 15 00 by M. C. Betts and T. A.H. Miller. blocks. Adobe or mud walls are also made "Pise' de terre (pronounced pee-zay duh 1�r. Minium has been with the Soil Conservation Service _ _ smce 1934. The authors particularly wish to acknowledge talfe), which means rammed earth in the cooperat10n of Professor H. M. Crothers Dean of Engi­ French, is an ancient type of construction. neering, and of Associate Professor Leo Puh� of the Agron­ omy Department, Professor W. E. Poley and Prof. W. C. The writings of Pliny state that watch tow­ Tully of the Poultry Husbandry Department, and Dr. K. W. Franke of the Chemistry Experiment Station, South Dakota ers of this material constructed byHannibal State College. 6 Bulfrtin277, Revised, Smuh Dakota Experiment Station by packing the wet mud into forms, making utor of asphalt emulsion oil used for stabiliz­ a monolithic wall. In most of these walls ing soils. It is called "Bitudobe" and is a straw or other binder material has been gen­ stabilized adobe . Asphalt emulsion is erally used. There are other variations in the used for the stabilizer and is mixed with the use of earth for wall construction that are of puddled soil or mud as the bricks are made. less importance and perhaps less practical. The bricks are generally made smaller than In the South Western states the adobe brick the common adobies, being about 12 by 12 are used extensively. Mexican laborers are by 4 inches. These bricks are moisture resis­ generally more or less experienced in mak­ tant and much superior to the common ing these brick and the work can be done adobies. The Station has worked with these when farm work is slack. The authors be­ bricks to quite an extent but has published lieve the rammed earth wall may be better nothing on it. Their use is more practical adapted to the North Central section of the when they can be made at a factory, as they United St.ates because of inexperience in were found very difficult to make without making adobe brick, and because of a great special mechanical equipment. deal of experience in building of concrete Two other types of earth walls were used and the use of forms in making monolithic extensively in Europe in early days. They walls. The monolithic wall is also entirely were called "chalk" and "" walls. They resistant to the infiltration of cold air in were very thick, solid walls made of mud winter. It is also stronger and more stable. and st-raw. They were tedious to build be­ The rammed earth wall is a "once over, all cause each layer of mud placed on the wall over" method. It saves two or three han­ had to dry out before the next layer could dlings of the soil and also saves the mortar be laid. for laying the bricks. In a warm of Insulating and Air Conditioning Quality even temperature, mud is fairly satisfactory of Rammed Earth Walls. One very impor­ for the mortar used to lay the bricks, but for tant reason for this experimental study is the more northern whei"e loosening of the mortar joints would result in a cold need for insulated walls for housing live­ stock and poultry in climates subject to cold wall, the monolithic or one-piece wall should weather in the winter season. Moisture and be preferable. The heavy forms used for frost accumulate on the inside surface of rammed earth construction are not built all cold side walls in such a climate. The great­ the way around the foundation of the build­ est damage from this frost accumulation ing as for pouring concrete. One or two sec­ tions of form only are required. The wall is comes when the weather moderates. The thawing of the frost from the walls makes rammed a section at a time, and after one section is rammed the form is then moved the building damp and creates a condition ahead and another section is rammed. that is unhealthful for livestock and partic­ ularly bad for poultry. Rammed earth walls The soil used for ·rammed earth walls is ate excellent insulating material and have not wet and in no way approaches mud. proved very satisfactory in the control of Generally the soil that is excavated for the moisture and frost. A poultry house was basement of a house will be too moist for built with rammed earth walls and straw making the best walls. Soil that will make a loft on the College Poultry Farm2 for the mud ball is too wet. It should have only purpose of comparing frost deposit and in­ enough moisture in it to mold nicely when side temperatures with several other . it is pressed in the hand. Clean soil of this moisture content is easy to handle and During the first part of the 193 2 winter makes a wall that will not check badly, one season the weather was abnormally cold and that is smooth and resistant to shock, a good the temperature dropped to 18 degrees be­ insulator and a surface that does not bake. low zero. A thorough inspection of the in­ A recent development in earth wall ma­ side walls during this period revealed no terials has been made by a leading distrib- 2See page 48. Rammed Earth Walls For Farm Buildings J trace of frost on the inside walls of the ram­ Rammed earth construction lends itself med earth house, while in the other houses well to construction of simple buildings the frost deposit varied from light to heavy. with comparatively low sidewalls and few Later in the season the temperature dropped wall openings. A building such as average­ to 30 degrees below zero and the frost de­ sized farm poultry houses can be built above posit on the rammed earth walls was almost the foundation in 10 days to two weeks' time as heavy as on the walls of other houses of by an experienced crew of three men. If the frame construction with average insulation. labor must all be hired there will be little, if All of these houses had straw lofts except any, saving in the cost of the walls over one, and in this house the frost condition those built from lumber or building tile. was more than twice as bad as in the ram­ The advantage of rammed earth construc­ med earth house. The frost did not make the tion must be in utilizing labor for which lit­ inside of the rammed earth house damp tle or no cash need be paid and in securing as it did the others. The wall absorbed the an exceedingly warm and dry sidewall for moisture very readily as the frost melted the poultry house. For more elaborate build­ and when the air later became dry this mois­ ings of more than one story the work is ture was returned to the air. The rammed more tedious, forms and frames for open­ earth wall was only 12 inches thick. ings require more time, and if the labor is It was a desire on the part of the Experi­ hired the cost is apt to be fully as great if not ment Station to find an inexpensive and sat­ greater for rammed earth construction than isfactory wall for the farm poultry house for other materials. However, this study has that made this study of economic impor­ verified former claims made by investiga­ tance. A cooperative study of this poultry tors and enthusiasts for rammed earth con­ house is being carried on at the present time struction that most excellent homes and by the Agricultural Engineering depart­ buildings can be built of earth if desired. ment and the Poultry Husbandry depart­ Although under normal conditions the cost ment. of elaborate buildings of rammed earth may

FIG. 1. A SMALL RAMMED EARTH BUILDING USED FOR EXPERIMENT AL PURPOSES One writer suggests that it would be a good idea for one who is planning to build rammed earth walls to build a small building first in order to become accustomed to the soil and to the handling of the forms. The authors do not believe this is necessary, but a small building such as a smokehouse or garage would be a good one to build if it is desired to follow this suggestion. 8 Bulletin 277, Revised, SouthDakota Experiment Station be as high as ordinary uninsulated frame dred dollars at the present price. The Cali­ houses, the walls, if kept well st uccoed, fornia Experiment St at ion4 report s that with should la st indefinitely and be especially the mechanical rammer a const ructi on speed 3 valuable for modern air condit ioning . of 7 cubic feet per man hour was se cured. 4 One aut hor recommends that before With hand ramming , a speed of 2 cubic feet st art ing on an elaborate building of rammed per man hour would be about as much as eart h it would be well first to build a small could be expected of an experienced crew of simple st ruct ure and thereby become famil­ iar withth e use of the forms and the charac­ men. In building the walls of the poultry terist ics of the soi l. Such a building might house at the South Dakot a Experiment St a­ be a small smokehouse or a farm poultry tion the speed averaged one and one- half house. cubic feet per man hour. St udent labor was Mechanical rammers may be used in the used ent irely for this work, however, and const ruct ing of ra mmed eart h walls. Their the work was not only done int ermittent ly use will cut down the labor hours for this but new men had to be broken in.

work but the cost of a complet e compressed 3Coffin-Humphrey, "Lower Cost Buildings." air out fit for ramming will cost several hun - 4J. D. Long-California Experiment Station Bulletin No. 472.

Methods Used for Testing Soil and Walls The purpose of these st udies was to learn tempts have been made to overcome this the str uct ural charact eristi cs of soils favor­ diffi culty in the test pieces and some results able to rammed eart h const ruct ion, to det er­ have shown improvement but nothing en­ mine the opt imum and sand rat io and tirely sat isfact ory. Work is st ill being done the opt imum moist ure content for both on this problem. Samples of soils from all st rength and weathering resist ance in ram­ parts of South Dakot a were analyz ed and med eart h walls. Furt her st udies were made on protect ive coverings, on the effect of add­ test ed both for st rength and for resist ance to ing fiber to the soil, on rnmmers and the weathering . These soi ls were taken from 18 proper ramming of soil int o the forms, on count ies of the st at e and covered the ext reme rei nforcing for wall opening s and corners, territories.5 and on the best pract ices in building walls Test Blocks and Beams. All early test of this mat erial. Finally, the st udy of the blocks were cubical in shape and were 9 by cost and economy of rammed earth walls and their relat ive insulat ing value in the 9 by approximat ely 9 inches. They were cont ro l of frost deposit when used fo r hous­ about as heavy as can be convenientl y han­ ing livestock, was made. dled, weig hing from 45 to 60 pounds when first made, depending upon the amount of The st rength test s in compression were sand in the soil. They were rammed in made to det ermine the relat ive value of cer­ forms and with hand rammers. They were tain soil charact erist ics or building pract ices, handled on board trays 12 inches square.6 and not because it s st rength for farm build­ ing walls was quest ioned. Walls made from The test beams were made for the rein­ soils showing the lowest st rength are amply forcing st udy and were 36 by 12 by approxi­ st rong to carry the compression load in mat ely 7 % inches in dept h. They weighed walls. Alt hough there is a tendency for from 25 0 to 26 0 pounds and were handled planes of cleavage to develop bet ween the on slat trays approximately 10 inches by 48 layers of eart h as they are rammed in test inches. blocks and beams, they di d not prove to be a 5Sce Resistance of Rammed Earth Walls to Weathering, p. 20. fact or of import ance in walls. Various at- 6Cylindrical test blocks· were used later in the study. Rammed Earth Wa lls For Farm Buildings 9

FIG. 2. TESTING RAMMED EARTH BEAMS USED IN THE REINFORCING STUDY The beams were 36 inches long, 12 inches wide and 7 % inches high. The reinforcing materials were placed one and one-half inches from the bottom of the beam. The span used in the test was 24 inches and force was applied at the top, midway between the two contact points. The Olsen testing was used.

Testing the Soil for Moistur e. Th e mois­ in the blocks at any time , the blocks we re ture te sts of soils we re made in du plicate . weighed imme diate ly after they were made Me asures of the soil we re take n fr om six and whe n the moisture conte nt of the soil different points in the pile and placed in a was known. By re weigh ing a block at a small sample pile wh ich was then mixe d later date the moisture content cou ld be and quartered. Fr om th is soil, du plicate figured fr om th e loss in the we ight of the sample s of 40 0 to 500 gr ams each we re bl ock. Th is was done in the following man­ placed in soil pans. Th ese we re we ighed ne r: Th e we igh t of the ne w block mu lti­ and place d in an electr ic dispatch ove n, plied by the moisture conte nt of the soil wh ere they dr ie d ou t to constant we igh t at fr om wh ich it was made , in pe r ce nt, gave a te mper ature of appr oximate ly 220 de grees th e we igh t of water in the block in pounds. F. The sample s we re th en reweighed and the loss of moisture figured. The pe r ce nt of After the block had dr ie d ou t it was re­ moisture was the n de termined by dividing we ighed and the loss of we igh t in pou nds the loss of moisture by the ne t we igh t of the ( wh ich was ne ce ssar ily the we igh t of the we t sample of soil. The aver age of the du pli­ moisture lost) was su btr acte d fr om the cate figure s was used for the true moisture pou nds of water or iginally in the block. pe rcentage . Th is gave th e we igh t of the moisture, in pou nds, th at was le ft in the block, and Testing the Blocks for St re ngth in Com­ dividing th is figure by the we igh t of the dr y pre ssion. All te st blocks th at we re te sted for block gave the moisture content of the dr y strength in compression we re stored in the block in pe r ce nt. The blocks we re handled rese ar ch labor ator y in a te mper ature arou nd at all time s on a small boar d tr ay 12 inches 70 de gree s F. until th e moisture conte nt sq uare and of known we igh t, so th at no was reduced to almost a constant figure . loss of we igh t cou ld result in handling. The Th is moisture conte nt average d be low th ree blocks we re made in the form of cu be s pe r ce nt at the time they we re br oken. In 9x9x9 inches. It was not always possible to or de r to de termine the moisture contained ge t the de pth of the blocks exactly nine 10 Bulletin 277, Revised, South Dakota Experiment Station

FIG. 3. TESTING THE RAMMED EARTH BLOCKS FOR COMPRESSIVE STRENGTH The blocks were crushed in a Riehle testing machine when their strength in compression was desired. This block shows a typical failure, indicating a sound block or one without any special flaw or weakness. It failed under a load (ultimate load) of 36,000 pounds or 18 tons, which is about an average strength for South Dakota soils. The dimensions of the block are 9x9x9 inches. Four hundred of these test pieces have been broken so far in the study. inches and when this van at10n was su f­ Exper imental Soil No. 1, Ex per imental Soil ficientl y gr eat, corr ection was made for it. No. 2, and Ex per imental Soil No. 3. Ex per i­ The blocks wer e cr ushed in a Riehle test ing mental Soil No. 1 was a black clay soil ob­ machine.7 tained in a val ley one-hal f mile nor th of the Since the bottoms of the blocks wer e per ­ Ex per iment Station. It is composed of 89.6 fectl y squ ar e and level , they wer e seated per cent silt and clay and only 10.4 per cent upon a one- fourth inch fiber pad for the of sand, most of which is fine.Ex per imental test. A sand cu shion leveli ng the top of the Soil No. 2 was a yellow clay soil fou nd bl ock and covered with a second fiber pad in the su bsoil under all of the higher gr ou nd was used on the top of the block. The upon which the col lege campu s is located. It str ength figures ar e su rprisingly unifor m aver ages only 62.5 per cent clay and silt and for these test pieces of su ch mater ial. Sim­ contains 37.5 per cent of total sand ranging il ar test blocks of a ser ies seldom var ied in size from par ticles that ar e just retained mor e than thr ee or four per cent and an upon a ver y fine scr een of 20 0 mesh to the aver age of thr ee or four blocks has usually lineal inch, up to one inch in size. Ex per i­ pr oved a reliable and satisfactor y figure. mental SoilNo. 3 was a dar ker yellow sandy The manner of testing the test beams is clay soil fou nd in a cef' tain local ar ea near descr ibed under the par agr aph on "Rein­ the campanil e on the State College campu s. for cing in Rammed Ear th Construction," This soil is ver y high in total sand and gr av­ and a picture of the test is shown in Fig. 2. el content, containing onl y 25 .2 per cent ot clay and silt with a total sand or aggr egate Soils Used for Standard in Tes ts. Thr ee content of 74. 8 per cent. The aggr egate is standar d soil s wer e used for making test ver y well gr adu ated in size, var ying all the pieces when a standar d base soil was needed way fr om the 20 0-mesh size up to two inch­ for comparing the effect of cer tain condi­ es. This soil made one of the five best walls tions or pr actices. They wer e designated as 7See Fig. 3. Rammed Earth Walls For Farm Buildings 11 in the yard; all have stood satisfactorily as from the finest particles that were retained bare walls for 15 years and were built from on the 20 0-mesh screen up to the largest soil without any addition of sand. pebbles, will often be referred to in the ta­ Mec hanical Analysi s of Soi l Sam ples. In bles and in this bulletin as "sand." All soil particles that passed thr ough the 20 0-mesh analyzing the soils, at first no attempt was screen were considered silt and clay. made to separate or study the silt and clay materials. The analyses were made in the NOTE: Since 1934 a different method of followi ng manner: Duplicate samples of ap­ analyzing soils has been used. It is known as proximately 500 gms. were thoroughly dried the hydrometer method of analysis, and in the electric dispatch oven until reduced to with this method the silt is separated from constant weight. They were then weighed the clay so that the total sand, total clay, and and passed through the following sized total silt in a soil are determined. The soil screens in order: three-fourths inch, one- half sample must be taken very carefully so that inch, and one- fo urth inch. The sample was it will be exactly representative of the soil then screened through the one-eighth inch, that will be used in the walls. Prospective the 10 0 -mesh ( 10 0 mesh to the lineal inch), builders may obtain instructions for secur­ and the 20 0 -mesh screens under a stream of ing and sending in samples to the laboratory water. The sand retained on these screens for analysis by addr essing the Agricultural was then dried and each size was carefully Experiment Station, State College, Brook­ weighed. For simplicity the total aggregate, ings, South Dakota.

Table 1. Mechanical Analysis of Three Base Soils Used in Experimental Blocks and Beams Analysis with 200-Mesh Sieve

Sand Number Total silt Y4 in. Yi in. Yi in. Total of samples and clay 200 to 100 100 to Ys in. to Ys in. to Y4 in. screen aggregate Soil Color averaged per cent mesh screen mesh screen mesh screen mesh screen and above per cent Experimental Soil No. 1 ______Black 4 89.641 4.514 5.76 .085 10.36 Experimental Soil No. 2 ______L. Y cl low 4 62.44 8.799 25.354 1.918 1.662 .826 37.56 Experimental Soil No. 3 ______D. Yellow 4 25.18 4.690 41.870 9.390 7.200 11.670 74.82

Relation of Sand Content, Moisture, and Shrinkage in Soils For Rammed Earth '\V ork The first study made was for the purpose pressive strength in a Riehle testing machine of finding out the effectof sand content and and the results are given in Table 2. moisture, in the soil used, upon therammed Moistu re and Sand. This study disclosed earth wall. Thirty- nine test blocks were several relationships between the amount made for this study with the idea of observ­ of moisture in the soil and the properties of ing them and later of testing them for com­ the rammed earth. It was found that the op­ pressive strength. Five different amounts of timum moisture for ramming varied in in­ sand were used in this series of blocks and verse proportion to the amount of sand in the moisture was varied from high to low in soil, as the sand in the soil was increased the three graduated amounts within the bond­ required moisture decreased. This is due to ing range. The blocks were closely observed the fact that soil that is made up of small as they dried out and the shrinkage was particles ( silt and clay) has a much greater measured. After the blocks had dried to surface area for moisture than soil contain­ constant weight they were tested for com- ing coarser particles of sand and gravel with 12 Bulletin277, Revi sed, South Dakota Experiment Station the silt and clay . A sandy soil co ntai ni ng rammed earth varies in inve rse pro po rtion only seven or ei ght per cent moi sture wo uld to the amount of sand in the soil, but there is be satisfactory while a clay soil wi th this per no do ubt of thi s pro po rtion for hi gher cent of mo isture wo uld be altogether to o amo unts of sand. It is hi ghly pro bable that, dry to ram. It wo uld require 16 to 18 per in general, soi ls co ntai ning 30 per cent or cent of moi sture to bring this soil up to the more of sand decreas e in strength in invers e opti mum mo isture for ramming. Bank- run ratio and po ssi bly thi s ratio might carry all sand and gravel alo ne wi ll be qui te wet the way through if the weakening effects of when co ntaini ng only three or fo ur per cent cracking and checki ng in the blo cks co ntai n­ of mo isture. ing little sand co uld be avoided. However, Moistur e and Strength. The amo unt of strength is seco ndary in importance. All mo i sture in the soil when it is rammed has a walls wi ll have ample strength. Sand in the deci ded effectupo n the strength of rammed soil makes them durable. Thi s is of firs t earth in co mpres sion. When too dry , all soi ls importance. seem to lo se strength markedly , and in mo st Moisture and Shrink age. The study leaves cas es soils that are to o wet show a lo w no do ubt abo ut the relationshipof mo isture strength. Thi s is parti cularly evident with and shri nkage. Regardless of the soil and its sandier soils and it is pro bable that thi s may characteris ti cs, the amo unt of shrinkage va­ be due to the larger amo unt of space lef t in ri es in di rect ratio with the amount of mo is­ the blo ck af ter the mo i stm· e has evaporated. ture in the soil at the ti me it was rammed, Such a blo ck seems much les s dense and the i.e., provided the mo isture is suffici ent to pres ent status of the study , purely from the bo nd the soil parti cles we ll. Thi s fact is also strength standpoint, indicates that i11 shown in Table 2. Altho ugh the shrink­ rammed earth co nstruction density may be age may no t be very great in the sandi er soi l, as important a facto r fo r strength as itis in it will increase wi th the increased mo isture. co ncrete. Wi th the les s sandy soils shri nkage is no t Sand and Strength. The res ults have no t only a very seri ous and undes irable facto r as yet shown defini tely that the strength of in rammed earth co nstruction but may be a

Table 2. Relation of Moisture, Strength and Shrinkage in Rammed Earth Test Blocks*

Sand Oto 5 per cent Sand IO to 20 per cent Sand 25 to 35 per cent Sand 42 to 53 per cent Sand 55 and above

Per cent moisture Strength com- Strength com- Strength com­ Strength com- Strength com- content Per cent pression lbs. Per cent pression lbs. Per cent pression lbs. Per cent pression lbs. Per cent pression lbs. in soil shrinkage per sq. in. shrinkage per sq. in. shrinkage per sq. in. shrinkage per sq. in. shrinkage per sq. in. 6 .14 147.7 7 .18 226.1 191.5 8 141.4 .00 198.5 9 .80 464.1 .91 404.1 .68 292.3 10 1.33 374.3 .66 626.0 .662 609.5 .00 246.0 11 .42 273. 1.72 439.0 .66 531.6 .50 509.0 .15 205.8 12 .40 877.St 1.85 605. 1.35 523.5 1.19 381.0 .33 441.0t 13 1.66 400. 1.51 493. 1.30 353.0 14 2.43 576.5 .86 352.5 15 2.8 385. 16 2.01 522. 2.04 511.0t 17 3.16 344.5 18 2.23 692.0t 1.00 270. "Later findings show that some of the variations in strength in this table were due to a difference in the age of the test piece when broken. tFigures that fall out of line for the strength curve. NOTE: As the sand content increases the shrinkage decreases. As the sand content increases above 35 per cent the strength decreases. As the moisture increases the shrinkage increases. Rammed Earth Walls For Farm Buildings 13

.. •

.______RELATION OF SAND CONTENT-

TO 5HRINKAGE I "" iN RAMMED EARTH '��, '� -.. f' '� "� f"'r--....,_ �i--,... �r-

JL0. t 0. 2 0. 3-0; �O. 50. 60. 10. Per-cent or Sancl In Soil. FIG. 4. AS THE SAND INCREASES IN THE SOIL USED FOR RAMMED EARTH THE SHRINKAGE IN THE WALL DECREASES This curve is developed from the average shrinkage of test pieces used in compiling Table 2.

limit ing fact or. In these soils a comp arat ive­ tent. In this connect ion it is int eresting to ly large amount of moisture is need ed to not e that in a long wall there will be some make them wet enough to bond and this shrinkage, however, and that the amo unt of means a high shrinkage and large shrinkage shrinkage that will be exp ect ed can be fig­ cracks and checks.8 These chec ks ap pear to ured . In ord er to figureit , it is first necess ary red uc e the res istance of the soil to weat her­ to determine the shrinkage coefficient of a cert ain soil by testing. For instanc e, if it is ing, caus ing them to crumble away when found that a test bloc k of a cert ain soil the surfac e is expos ed to the weat her. This shrinks .5 per cent, then for every 10 0 inches may not be in direct prop ort ion but ap par­ in the lengt h of the wall there will be a ently it generally is. shrinkage of one-half inch. This may be largely taken up or abs orbed in many hair­ Sand and Shrink age. Sand in the soil re­ like cracks or there may be a larger one or duces shrinkage of rammed eart h in direct two, or the joint bet ween the sections of the prop ort ion by red uc ing the amount of mois ­ wall as they were rammed may pull apart ture that is required in the soil at the time slight ly to take up this shrinkage. The it is rammed. Soils cont aining 50 per cent or shrinkage of the bloc ks has been diffic ult to more of sand do not shrink enough to caus e measure as acc urat ely as des ired. cracking or chec king of the wall to any ex - 8See Fig. 5. 14 Bulletin277, Revised, South Dakota Experiment Station

FIG. 5. A PISE' WALL FROM SOIL IN WHICH THERE WAS TOO MUCH CLAY The checks and cracks shown in this wall section were caused by shrinkage forces and are typical of heavy clay soils in which there is very little sand. This soil contained only 11 per cent of sand by weight, and the 89 per cent was silt and clay. This soil is unfit to use because of high shrinkage. The addition of sand will not make a favorable soil from one originally containing 30 per cent or more of pure clay.

For practical pu rpose s the re su lts of the shr inkage and in increasing the re sistance study of this re lationship for sand, moistu re , to we athe ring. In Table 2, p. 12, the re su lts and shrinkage show that the optimu m mois­ that are shown not only include the 39 tu re shou ld be used for be st strength and blocks made espe cially for this study, bu t we athe ring. Althou gh this optimu m mois­ include some ad ditional blocks that are of tu re varies with the amou nt of sand in the widely diffe re nt characte r, thu s ad ding con­ soil, it is easy to de term:ne it by practical tests described in a following paragraph, and siderable value to the re su lts shown. Prac­ with a little experience a me re hand ling of tically every stre ngth figure and the corre­ the soil is su fficie nt. Sand in the soil re duces spond ing shrinkage figu re for a ce rtain the compre ssive stre ngth of the soil some­ moistu re and within the range of sand, are what, bu t it is ve ry valu able in re ducing ave rage s of se ve ral diffe re nt blocks.

The Unit Weight of Soils in Rall_lmed Earth

By unit we ight is me ant the we ight of the of unit we ight and the sand conte nt in the soil pe r cu bic foot, and in this study it was soil. The three base soils used in all ou r ex­ usually figu re d for all te st pie ce s afte r they pe rime ntal work we re chose n be cau se the y we re thorou ghly drie d ou t. Howe ve r, the re pre se nted three widely diffe re nt soils. In figu re s shown for unit we ight in the ne xt total sand conte nt the y vary almost in a di­ table are for te st pie ce s that we re ne wly re ct proportion and the ir unit we ight varies made and contained all of the original mois­ acc ord ingly. The figu re s shown in Table 3 tu re.It is inte re sting to note the re lationship are ave raged from 12 blocks of each soi l. Rammed Earth Walls For Farm Buildings 15

FIG. 6. AN EXCELLENT SOIL FOR RAMMED EARTH WALLS This wall was made from soil that is almost perfect for rammed earth construction. It is made from Experi­ mental Soil No. 3* and has stood for nearly fifteenyears. This is the south side of the wall, however, and the north side is somewhat roughened from driving rains from the north. This soil contained 74.8 per cent of sand by weight, and the shrinkage for it was almost negligible.

"'See Table I. Table 3. The Relation of Sand Content to Unit Weight

Experimental Soil Experimental Soil Experimental Soil No. 1 sand conteat No. 2 sand content o. 3 sand content Soil 10.36% 37.56% 74.82% Unit lb. per cu. ft. lb. per cu. ft. lb. per cu. ft. Weight 119.4 128.38 138.87

Optimum Moisture in Soil for Weather Resistance One or two exper iences in the stu dy su g­ wall was slightly too wet, having 11.58 per gested that a higher moisture content in the cent moisture. The fourth wall was made soil than is needed for maximu m str ength ver y wet-in fact, just as wet as it was pos­ might be desir able for resisting weather . sible to ·ram it. The moisture content was This fact is qu ite satisfactor ily dispr oved by 14 .0 1 per cent. the following tr ial. A composite sample of The average soil was used in the� e walls an aver age soil containing 35.7 per cent total becau se they wou ld show the effects of sand was selected and used for making four weather ing mor e qu ickly. Like all weat her­ rammed ear th walls. These walls wer e bu ilt ing walls, the su rface was unpr otected. exactly alike except for moisture content. They wer e given the same location in the Four year s after the walls wer e bu ilt the yar d and wer e made by the same wor kmen, resu lts wer e shown ver y definitely in these car e being used to ram the same. The fir st walls. The fir st wal l made fr om the too-dry wall was rammed ver y dr y, having only 6.59 soil was ver y definitely the poor est wall. The per cent moisture in the soil. The second second wall, having the optimu m moisture wall was rammed with 9.10 per cent mois­ content, was ju st slightly bet ter than th e tu re, which is the optimu m moisture in this thir d wall. The fourth wall, which was soil for str ength in compr ession. The third rammed extremely wet, was definitely poor- lti Bulletin277, Revised, South Dakota Experiment Station

FIG. 7. ADDING MOISTURE TO SOIL FOR RAMMED EARTH WORK Water is added to the soil from a garden sprinkler as the soil is turned. The picture is taken inside the research laboratory of the department of Agricultural Engineering, South Dakota Agricultural Experiment Station.

er than the second and third, but much bet­ too-dry wall. Later work has shown the im­ ter than the first.The important thing was, portance of having the moisture high the too-wet wall was much better than the enough, rather than having it too low.

Kind of Soil Best Adapted to Rammed Earth Construction Contrary to the prevailing opinion, heavy larger pebbles, and so on. The soil men­ clay soils and soils often referred to as tioned above, having 74.8 per cent of sand in "gumbo" are the poorest kind for rammed it, contained sand that was exceedingly well ea·rth construction. graduated. It is the Experimental Soil No. 3, The most satisfactory soil for rammed and the mechanical analysis of it is given in earth construction will have a considerable Table 1. This soil has the highest unit amount of sand in it, ranging from 40 per weight of any soil that has yet been found, cent to 75 per cent, with the optimum averaging 138.87 pounds per cubic foot after amount around 75 per cent. This will vary being rammed. with soils of differentanalyses. The best test wall in the yard is made from soil having Few natural soils containing less than 30 74.8 per cent of sand in it.9 The study has per cent of sand were found satisfactory for proved quite definitely that the sand or ag­ rammed earth construction, and 35 to 50 per gregate, when as high as 70 per cent is used, cent was much better. Many agricultural will have a somewhat greater strength in soils will be found to fall in the group con­ walls if it is well graduated from the fine taining 30 to 50 per cent of sand and will be particles up to the larger pebbles, with a ma­ found satisfactory. Sand can be added to a jority of the finer aggregate. When there is 9Sand as used in this report includes all the hard aggregate such a graduation. of aggregate the finest that will not pass through the 200-mesh screen or will not particles fitin between the larger sizes and float off when the soil is washed in a pan. Some of the pebbles may be almost as large as the fist, while the finest the larger sizes fitinto the spaces of the still grains will just be retained on the 200-mesh screen. Rammed Earth Wa lls For Farm Buildings 17 soil slightly deficientin sand with very little bare wall, and 70 to 75 per cent is apt to be trouble. In fact, if the sand is convenient, it more weather res is tant. Soils of medium can be added on the mixing board with quality can be used satis factorily when stuc­ scarcel y any additional labor, and it is advis­ coed over bonding wire but the addition of able if at all pos sible. Very few soils with sand will make it high quality and is rec­ les s than 50 per cent of sand will stand as a ommended.

A Simple Test of Soil for Rammed Earth Work . In spite of the fact that there is a wide down so the cup is entirely full. Place the soil range of soils that can be used succes s fully in a wash bas in or other flat pan and cover for rammed earth work when stuccoed, a with water, then stir with the hand and pour good soil will require a little les s care in off the dirty water. Fill the pan with clean ramming and, still more important, will water and repeat this operation until all the stand longer in case the stucco is neglected fin e silt and clay partic les are floated off. It after the building becomes old. As stated above, such a soil will have betw een 50 per will only take a few minutes until all the silt cent and 80 per cent of sand in its structure. and clay are gone and the water will remain A simple tes t can be made to determine clear. What is left in the pan will be clean roughly whether a soil falls in the clas s of sand and some of it will be very fine. Dry the good soils or not. Take an average sample of sand and measure it in a meas uring cup. If the soil in a flat pan and dry it in a hot oven there is a full cup of sand there is app roxi­ for three or four hours . A wash bas in will mately 30 per cent of sand by weight in the answer perfectly fo·r this purpos e. The soil, and it is apt to be fairly good for amount of soil should be more than a quart. rammed earth work. If there is more than a Next, pulverize the soil fairly well so it will cup of sand and not more than three cupfuls not have many lumps in it. Pebbles of all it should be an excellent soil for the work. sizes should be left in the sample. Fill a Laboratory analys is of soils is urged before quart cup with the dry soil and settle it bui lding .

FIG. 8. AN EXPERIMENTAL WALL OF HEAVY CLAY OR "GUMBO" SOIL This wall section shows extreme checking and cracking of an earth wall due to a very low sand content of the soil used. At the right is the surface of the same wall several months later. The cracks settle together to quite an extent after the moisture leaves, but the wall crumbles away. 18 Bulletin277, Revised, South Dakota Experiment Station Effectof Reramming Soil in Pise' Construction Soil that has once been rammed int o a and the soil was used again in making an­ st ruct ure can be broken up and used again ot her block wit hin a few hours. The second if desired . A trial was made of this by ram- block was test ed in the same machine and it s ming a test block of Experiment al Soil No. 1. st rengt h was slight ly higher than that of the The block was test ed for st rengt h in the original block, due, no doubt, toth e anxiety compression machine, being test ed to de­ of the operat or to do a careful job of ram­ st ruct ion. Aft er it was broken the pieces ming. Only a slight amount of moist ure was were broken up on the concret e Boor of the lost from the first block due toth e remixing test ing laborat ory by means of the rammers process.

Effect of Freezing Weather upon Rammed Earth Construction Work Construct ion work can be carried on in ture at 18 degrees F. and zero temperat ures any reaso nable weather as long as the soil is followed wit hin a few days. The tempera­ not frozen and the temperat ure does not fall ture of the soil used in this wall was above too much below freezing. However, it is ad ­ 60 degrees F. when the wall was rammed , visable to avoid freezing weat her when pos­ however, because the soil had been kept in­ sible. During the fall of 19 30 a large wall sid e. Th is wall came out in excellent sect ion was being built at int ermittent int er­ cond it ion. vals throughout the month of November A small weat hering wall rammed late in and up unt il Christ mas time. Alt hough the the fall of 19 32 was caught by an ext remely weather was generally mild , the tempera­ cold temperat ure that last ed for several days. ture fell somewhat below freezing on sever ­ This wall appears to have been injured by al occasions, and with no evid ent injury to freezing as two large sect ions of it seem to the wall. In January of 19 33 a small weat h­ have been moved out of line withth e rest of ering wall was rammed with the te mpera- the surface by the act ion of frost .

Care and Mixing of the Soil for Rammed Earth Work Care of the soil for rammed eart h work is are used for each bat ch and a measured of greatest import ance. The work can be amount of wat er is ad ded each time. In this done in almost any kind of weat her if the way there is no guess work, and it is impor­ soil is kept dry. Soil that is too dry can easily tant to have the moist ure cont ent reasonably be correct ed by sprinkling the pile with uniform. water and turning it carefully on the mix­ Sc reening the Soil for Rammed Earth ing board . It is better to doth is the day be­ Work. It is not necessary to screen the soil fore it is used , as the moist ure will help to dist ribut e it self in the pile during the night . that is to be rammed unless there is some A temporary shed as shown in Fig. 9 is al­ special reason for it. If there were large most a necessit y if no ot her cover is hand y. pieces of tree roots it would be desirable to Sheet ing lumber to be used for the roof of screen them out, or if the soil cont ained the build ing can be used in making this hard dry clod s it would be necessary to shelt er. Another way to ad d moist ure to soil screen them out . A st one as large as a hen' s that has become only slight ly too dry und er egg would do. no damage in the wall if there the shelt er is to pile a load or two out side were not too many of them. All of the ex­ where it will get the rains. A few shovels of periment al soil used in making test blocks this damp soil with each bat ch shoveled on and test beams in the laboratory is screened . to the mixing board will secure the correct A concret e mixer was found sat isfact ory for moist ure. In ad ding moist ure it will always mixing the soil when the moist ure was near­ save time if a cert ain number of shov elfuls ly right . Rammed Earth Walls For Farm Buildings 19

FIG. 9. A SHELTER FOR PROTECTING THE SOIL USED FOR RAMMED EARTH WORK In a shelter like this the soil can be kept dry enough to work at all times. A heavy rain on unprotected soil will make it too wet to use for days and even for weeks. If a shelter is not available a canvas or other protection is necessary. The lumber used in building this shelter was all used in the roof and plate construction after the walls were finished.

FIG. 10. THE MIXING BOARD FOR THE SOIL A mixing board is very convenient for turning the soil when moisture must be added or when two or more differentkinds of soil are mixed for use. The board is almost necessary when the ground is muddy. It is approx­ imately six by ten feet. 20 Bulletin277, Revised, South Dakota Experiment Station Effectof Depth of Block upon the Strength in Compression Since it was found practically impossible strength varied inv ersely as the depth of to make the test blo cks ex actly the same the test piece. The four thinne st blocks were depth or height, it was necessary to make too strong for the 10 0,000 pound testing ma­ corrections for the blocks when this differ­ chine. The blocks hav ing a depth of 4.4 ence was appreciable. In order to det ermine inches av eraged 662 pounds per square inch, the ex act ratio of the depth of the test piece those hav ing a depth of 6.67 inche s av er­ to its com pressiv e strength so as to deter­ mine the correction coe fficient, a series of aged 334 , while those hav ing a depth of 8.9 blocks was made varying the depth of the inches av eraged only 19 1.5 pounds per blocks in graduated amounts. Since the square inch. Ex perimental Soil No. 3 was standard test blocks were rammed in four used. It is a very sandy soi l and is not a layers, each being a trifl e ov er two inches in strong soil comparativ ely, but in this series thic kness, one series of blocks was made the blocks were all low in strength ev en for only one layer in depth, av eraging 2.24 inch­ this soil as the blocks were still green. The es. A second series of blocks was made two figure s are sum marized in Table 4 below. layers in depth, av eraging 4.4 inches. A third The correction coefficient as figured from series of three layers av eraged 6.675 inches, this test is 5.3 pound s per square inch for while a fourth series of the standard four each tenth of an inch the test piece may vary layers av eraged 8.9 inches in depth. The abov e, or below, nine inches in depth.

Table 4. Effect of Depth of Test Block upon the Strength in Compression

Depth of Av. ultimate Compressive Moisture Moisture Weight cf No. of blocks blocks (av.) breaking strength in lbs. Age when content content blocks in lbs. of each tested in inches load in lbs. per sq. inch broken (days) when made when broken (average) 4 2.24 1,234.+ 35 7.92% 0.33% 15 4 4.40 51,625 662. 35 7.92 % U.45% 30 4 6.67 27,050 334. 35 7.92% 0.85% -f5 4 8.90 15 ,515 191.5 35 7.92% l.32% 62 �These blocks stood more than 100,000 pcunds, which was the limit of the testing machine used.

Resistance of Rammed Earth Walls to Weathering In determining the resistance of a soil to then edged with sheet steel strip s with the weather action, small test walls were built of low e£ edge of the strips proj ecting an inch each different soil to be tested. These walls below the plank, and this tr ouble was elim­ are 12 inches thick, 36 inches long and ap­ inated. It was not intended to protect the prox imately 30 inches high. They are cov­ walls from direct rain action, but a peaked ered on top with a flat roof that proj ects 1Yi roof with the same proj ection wo uld be inches on all sides. This type of roof was more practica l 2nd more satisfactory for this found unsatisfa ctory as the water in time of purpose. The walls were buil t on concre te heav y rain is apt to flow back underneath foun dation s, with exactly the same width as this ov erhang and dow n the face of the bare the walls, ex tend in g 12 inches below and 6 wall. When this happens, grav e damage is inch es abov e grade. When the walls were done as the flowing water cuts the earth sur­ built some of the foundations were cov ered face like a knif e. Qua rter round was used to with water-proofing materials and others prev ent the water from flowing underneath, were lef t untreated for the purpose of com­ but with a h@ av y wind there was still some parison. Ninety walls have been built up to inj ury from this source. The cov ers were this time in this weathe ring series. Corrected Rammed Earth Walls For Farm Buildings 21

FIG. 11. A CORNER OF THE RAMMED EARTH EXPERIMENTAL YARD AT THE SOUTH DAKOTA EXPERIMENT ST A TION AT BROOKINGS, SOUTH DAKOTA This shows the type of small weathering wall used in the study. The roofs or covers as shown were not satisfactory, as heavy rains caused the water to run back under the roof projection and down the face of the wall in some instances. This cut the wall like a knife. A peaked roof would be better than the type shown. One hundred and thirty of these experimental walls have been built up to the present time.

FIG. 12. FORM USED FOR MAKING RAMMED EARTH WEATHERING TEST WALLS The tremendous side thrust exerted by the soil while being rammed may be realized by noting the 2x4 inch struts on this form. 22 Bulletin 277, Revised, South Dakota Experiment Station walls have been built w see if an addition of only pr ot ects the wall sur face against or di­ sand, or of clay, or an adj ustment in mois­ na ry wea ther ing, but pr otects it against tur e content would impr ove the or iginal flowing water which might str ike in an wall. For each wall made fro m a differ ent emer gency, or in the case of an old roof that type of soil a corrected wall has been built in had been neglected. the testing yard. For this same reason it is highly desir able The study to date indicates that pr ote ctive that the tops of walls be pr otected under and cover ings for rammed ear th walls ar e highly ar ound the plate with a thick layer of rich desir able if not absolutely necessar y in this mor tar . This mor tar woul d also region, for any excep t the most favorable 10 serve to level up the plate on the top of the walls. The best walls may be slightly wall. In the case of pl aster or stucco on the roughened on the nor th side fr om dr iving outside surface, this sho uld be delayed unti l rains, and most of the medi um soils begin the wall has dr ied out. to cr umble slightly within thr ee years' time. A covering of some effective mater ial such lONew walls weather more rapidly. After one or two years the walls made from favorable soils become very resistant as a cover ing of cement plaster or stucco not and are affected very little by the hard driving rains.

Protective Outside Coverings for Pise' Walls Since the subject of pr otective cover ings is cov er ings pr oved entir ely satisfactor y for in­ thor oughly repor ted in South Dakota Ex­ ter ior sur faces. per iment Station Bulletin 336 entitled Stucco: For exter ior sur faces Portland ce­ "Paints and Plaster s for Rammed Ear th ment stuccoeshave pr oved entir ely satisfac­ Walls, " most of the repor t on these mater ials tor y for rammed earth walls. The same included in the fir st and second edit ion of bonding wir es that ar e used for fr ame walls bulletin 27 7 has been omitted in this edi­ have been used. These include stucco wir e tion. Cover ings that were found satisfac­ metal lath and other expanded metals. The tor y on exter ior walls wer e few, while most wir e is nailed dir ectly into the wall in such a

FIG. 13. THIS GARDEN WALL OF RAMMED EARTH WAS BUILT IN 1934 AND WAS STUCCOED IN 193; The soil used in the wall is only medium in quality and, hence, must have a protective covering. The picture was taken before stuccoing. The wall is an experimental wall and today carries 28 panels on which differentmethods of bonding the stucco to earth walls are being tried. Rammed Earth Wa lls For Farm Buildings 23

FIG. 14. WETTING DOWN A RAMMED EARTH WALL BEFORE PLASTERING Before plastering the earth wall, it is wet down so that the moisture will not be drawn from the plaster. A garden sprinkler or hose could be used in place of this small spray machine.

manner as to stretch the wire and carry the stucco. Ordinary thickness is better as the ex­ weight of the stucco. The strips of wire must pansion forces will be less. Two coats only be lapped and wired together firmlyaccord­ were used in the experimental work. This ing to ordinary specifications for stucco method of bonding with nails only is not ad­ work. The wire should be nailed with lOd vised for important work such as dwelling and 16d nails spaced approximately 12 inch­ houses. es apart and at random. This method of se­ curing the bonding wire proved most satis­ Less Expensive Plasters: vV ork has been factory of many methods that were tested. done with many new and less expensive plasters for use on low cost buildings. This In studying ways of reducing costs on work is reported in bulletin 336. Two of small farm buildings, several methods of se­ these plasters that have stood satisfactorily curing the stucco without the use of bonding are dagga-cement plaster and asphalt emul­ wire were tested. Results show that for low sion plaster. In the firstone a dagga plaster is stabilized by adding 10 per cent of Port­ walls with occasional openings the bonding land cement by volume; the second one is wire can be omitted if the nailing is careful­ stabilized by adding asphalt emulsion at ly done. The method used was as follows: the rate of one gallon of asphalt emulsion to After the wall surface was swept down and 100 pounds of dry dagga mixture. Dagga sprayed with water the scratch coat (first plaster is a mixture of medium sandy clay coat) of stucco was applied. Following the and sand in a ratio of one part of the clay soil stucco man immediately, a man drove nails to two parts of plaster sand. Including the through this fresh stucco into the wall. The sand in the clay, the actual ratio of clay is ap­ wall was then allowed to stand for three proximately one to three. days to three weeks and the second coat of stucco was applied. A third or finishcoat can Paints: Of the actual paints that have be used if desired or this second coat can be been tested for exterior surfaces, none have sand finishedwith a carpet float.No attempt proved sufficiently dependable for general should be made to apply extra thick coats of recommendation. On high quality walls 24 Bulletin 277, Revised, South Dakota ExperimentStation

FIG. 15. AN EXPERIMENTAL WALL FOR PAINTS AND PAINTING METHODS This garden wall is divided into 28 experimental paint panels. The paints were applied at differentperiods, in different weight and number of coats, and over different primirrg coats. Different soils were also used, varying from excellent to very poor in quality.

good quality lead- oil paints will stand for lik e th is roug hened surface for dwelling per iods up to five or six year s but some of houses. In case builder s ag ree with th e ar t­ th ese failed later after repainting . Casein ists , paints ma y be used on walls with high paints applied in 19 39 ar e standing satisfac­ quality soils. In case it is desired to ch ang e a tor ily after six year s. Wh en paints fail on painted sur face to one of stucco, th e paint ear th walls th e surface is roug hened. Ar ti sts coat must be entirely removed.

Inside Wall Coverings Probably any satisfactor y cover ing for same way as for stucco on exter ior walls of oth er sur faces can be used on inter ior walls low cost building s. Th e only two failures of rammed earth. Th ey can be app lied di­ with insi de wall cover ing s th at have oc­ rectly to th e earth surface. Both oii paints curred have been with a special wood fiber and cold water paints have been successfully plaster and wh itewash-a cold water paint. used. All or dinar y- plast er s wer e found en­ Murescoes ar e quite satisfactor y. Th ey, as tirely satisfactor y. Th e scr at ch coat of plas­ well as oil paints, wer e applied over a glue ter sh ould be nailed with lOd nails in th e sizing or linseed oil sizing coat.

Weight, Shape and Type of Hand Rammers After three year s' exper ience in th e use of 18 pounds. Th e face of th e rammer will be hand rammer s of var ious sh apes, sizes and per fectly smo oth an d Bat, and th e weigh t of weights, th e favor ed rammer was one with a th e rammer will be fr om 1.5 pounds to 2 cast ir on or steel head cubical in sh ape and pounds for each squar e inch of th e rammer appr oximately 3 inch es in dimension each face. Th is rammer will be well balanced way. Th e sh aft of th is rammer will be of with a sh aft easy to grasp and hold and one one-inch galvanized ir on water pipe and ap­ th at will quickly wear to a ver y smooth sur ­ pr oximately 5 feet 6 inch es long . Th e total face. Th e inch pipe may be . thr eaded and weight of th is rammer will var y fr om 13 to scr ewed into a plate made fr om a pipe flange Rammed Earth Walls For Farm Buildings 25

FIG. 16. A COLLECTION OF HAND RAMMERS USED IN BUILDING RAMMED EARTH WALLS The square, flat-faced rammer, weighing from 15 to '18 pounds, is preferred by the workmen. The shaft is made from one inch galvanized pipe. The rammer head shown in the foreground has a beveled face, the sides making an angle of 30 degrees with the horizontal. Workmen did not like to use this rammer and test pieces made with it were not as strong in compression as those made from the flat-faced rammer.* •see Table 5. 26 Bulletin277, Revised, South Dakota Experiment Station tha t is, in turn, fa stened to the iron block by shapes of ra mmer fa ces were used. One11 means of screw bolts , or the pipe ma y be ha s a sharp fa ce in which the sides makean bra zed or welded to the hea d. Welding the angle of 45 ° with the horizonta l, one ha s a shaft to the head will be best when the ma te­ fa irly sharp fa ce in which the sides makean ria ls are suita ble, as the fla nges will fa il after angle of 30 ° with the horizonta l, and the long use. The squa re ra mmer is fa vored be­ third ha s a flat fa ce. Five test block s were ca use corners and edges of the form ca n be ma de with ea ch ra mmer and tes ted to fa il­ better ·rea ched with it and the flat ra mmer is ure in a compres sion ma chine. An identical not only fa vored by the work ma n but test soil, test Soil No. 2, ha ving a tota l sand con­ pieces ma de with the flat-faced ra mmer ha ve tent of 37 .5 per cent, wa s used and the mois ­ shown a grea ter avera ge strength in com­ ture content wa s kept uniform. The block s pres s10 n. ma de with the flat ra mmer were strongest, thos e with the 30 ° ra mmer avera ged next in In order to compa re the effectivenes s o± stren gth, and those with the 45 ° ra mmer the flat-faced ra mmer with those ha ving showed the least strength. Thes e re su lts are sharp fa ces , a ca reful tes t wa s ma de. Three shown in Ta ble 5.12

Table 5. Comparative Strength of Test Blocks Rammed with Different Shaped Rammers (Compressive Strength)

Ultimate load Compressive Age when Total sand Number of test blocks in strength lbs. broken content of blocks Shape of rammer face compression (average) per sq. inch (in days) (per cent) of each broken Sharp-faced rammer Sides 45 ° with horizontal ______28,457 351.3 40 37.2 5 Sharp-faced rammer Sides 30° with horizontal ______40,219 496.5 40 37.2 5 Flat-faced rammer ------44,107 544.5 40 37.2 5 The beveled rammer heads used and described in the early work with rammed earth proved both unsatisfactory and unnecessary.

Intensity of the Tamping Stroke A study wa s ma de to determine the effect fewer number would ha ve been suffici ent of the intens ity of the ra mming strok e upon for the ha rder stroke s. For the light strokes the compres sive strength of ra mmed ea rth. the ra mmer wa s ·ra ised about four inches Tes t block s were ma de in the standa rd form. and no exertion used in making the strok e. Five block s were ma de using light strokes, For me dium strok es the ra mmer wa s ra ised five were ma de us ing medium strokes, and about six inches and very little pres sure wa s five were ma de using hea vy strokes. A sup­ applied. For the hea vy strok es the ra mmer ply of soil wa s ca refully prepa red for thes e wa s ra is ed about 12 inches and all the force block s conta ining 38 .22 per cent of tota l pos s ible applied with the strok e. As shown sa nd and 61.78 per cent of silt and clay by in Ta ble 6, the compres sive strength of the weight. This is very nea rly an avera ge soil blocks va ried di rectly with the inten s ity of and contained 9 per cent of mois ture when ta mping and wa s decidedly in fa vor of us ed. This moisture wa s perha ps slightly under the optimum amount. The block s 11See Figs. 16 anc.l 17. 12Jt is true that with flat-faced rammers the planes of cleav­ were ra mmed in four la yers of eq ua l weight, age between layers of earth in the walls arc quite apparent ma king the weight of the finishedbloc k s al­ and the shearing strength is probably less than if wedge­ shaped ram;ners arc used, yet the strength in compression most identica l. The depth of the finished was greater and the stability was found definitely adequate. No trace or suspicion of failure has developed in any of block s va ried invers ely with the intens ity of the more than 1,000 feet of walls that have been built dur­ ing the past 15 years either in straight experimental walls the ta mping stroke used in ma king them or in buildings. One experimental building has been, con­ ( see Ta ble 6). Approximat ely 100 strok es structed with a roof truss that throws a maximum roof thrust upon the rammed earth walls. The walls are stand­ were used in ta mping ea ch la yer, although a ing perfectly after ten years. � � � � t �s. !� 1§,_ �...... �-, � !" f � �\i

� 28 Bulletin 277,Revi sed, South Dakota Experiment Station Table 6. Effect of Intensity of Tamping Stroke upon Strength of Rammed Earth Number of Av. ultimate Compressive Weight ·o·f Unit Moisture Age when blocks of Intensity breaking strength lbs. Depth of blocks blocks when weight when broken each tested of stroke load in pounds per sq. in. when made (av.) made (av.) per cu. ft.' broken (av.) (days)

5 LIGHT 7,506 92.7 11.14 in. 56 tt . 108 2.1% 44 5 MEDIUM 15,320 189.1 9.97 in. 56 tt . 125 2.7% 44 5 HEAVY 36,280 393.4 8.94 in. 56 tt . 135 2.9% 44 Walls rammed with medium intensity have proved definitely satisfactory in the 15 years of study.

the heavy tamping. The fivelightly tamped wall will also be greater for the heavier blocks averaged 92.7 pounds per square inch tamping, and especially so if no protective in compression. The five medium tamped covering is used. On the other hand the blocks averaged 189.1 pounds per square more lightly tamped wall would be the best inch, while the five heavily tamped blocks insulator. averaged 393.4 pounds per square inch. Ex­ The strength of the blocks ran quite uni­ tremely heavy strokes are not necessary for formly for each group, seldom varying rammed earth construction, although it might show a slight increase in the strength more than 10 per cent from the average fig­ of the wall, but this study indicates that ure. One exception was with one of the some little pressure is needed on the rammer blocks made with a medium tamping especially near the beginning and at the end stroke. This block tested only 82.90 pounds, of the tamping of a new layer. If pressure is which was only half the average strength not used the bottom of the layer will not be and probably due to some unnoticed defect. compressed sufficiently. It is entirely prob­ It was averaged in with the rest as it would able that the weathering resistance of the affectthe average figure but slightly.

Size of Aggregate in Soil for Rammed Earth Constructionand Its Effectupon the Compressive Strength The fact that a considerable amount of gate having less surface area reduced the aggregate is desirable in soil for rammed moisture more than the smaller sizes, as earth work led to this study to determine shown in Table 7. the effectof different sizes of aggregrate in Two differentseries of blocks were made rammed earth walls. Experimental Soil No. for this study. In the firstseries, made more 1 was used for the base soil. It originally con­ than a year earlier than the second, only tained 10.4 per cent of fine aggregate. This three differentsizes of aggregate were used. base soil was mixed with sufficientmoisture Thirty-five per cent (by weight) of aggre­ to bring the moisture content up to 16.01 gate was added to the 10 per cent already in per cent. The aggregate that was added was the base soil in each instance, bringing the then moistened before it was mixed with the · total up to 45 per cent. Four standard sized soil for ramming into the form. In having test blocks, each 9x9x9 inches high ( approxi­ the base or bonding soil at the same mois­ mately), were made for each different sized ture content and in moistening the aggre­ aggregate, viz., four with aggregate rang­ gate before mixing, it was believed that the ing in size from O to one-eighth inch, four results would be most comparable. This ac­ with aggregate ranging in size from one­ counts for the decidedly higher moisture eighth to one-fourth inch, and four with ag­ content in the check blocks because the ad­ gregate ranging in size from one-fourth dition of aggregate reduces the moisture inch to one-half inch. The figures are given co�tent decidedly. The larger sized aggre- in Table 7 along with the figures from the Rammed Earth Walls For Farm Buildings 29 more complete similar series for the purpose aggregate came third in strength and the of showing the similarity in results. others came in the fotlowing order: one-half The second series of blocks for this study to three-fourths inch, one-fourth to one-half was made in the same way using the same inch, and three-fourths to one and one-half base soil. In the second series 35 per cent of inches. The only variation in the curve was in the size one-half to three-fourths inch aggregate was added as in the first seriesand going above the one-fourth to one-half inch two additional sizes of aggregate were in­ size in strength, although these two were cluded. The blocks were tested to destruc­ very nearly the same. The figures bring out tion in a Riehle testing machine, described the unquestioned fact that aggregate in earlier in the bulletin. Owing to thi.:: nature rammed earth soils up to one-fourth inch in of the surface of the test blocks it was impos­ size and in quantities up to 45 per cent will sible to read the point of incipient failure increase the compressive strength of the with sufficientaccuracy, so the ultimate load structures. It also clearly shows that aggre­ only is given. Space will not permit showing gate larger than one-fourth inch in size, al­ the strength figurefor each individual block though desirable in reasonable quantities, but they showed a surprising uniformity of will decrease the strength of rammed earth strength for each series, varying only slight­ structures when used in quantities as high as ly from the average figure. The soil having 35 per cent.13 the one-eighth to one-fourth inch sized ag­ 13Aithough the size of aggregate affects the compressive gregate showed the greatest strength. The O strength of pise' walls it seems to have no effect upon the to one-eighth inch size was second in weather resistance. Very fine sandy soils have proved highly resistant to weathering. Their strength is entirely sufficient strength. The check blocks with no added for walls of reasonable height.

Table 7. E1Iectof Size of Aggregate in Soil_ on Compressive Strength of Rammed Earth Average Compressive Number of Weight Moisture Moisture Total Size ultimate strength blocks of of blocks content content aggregate Age when of aggregate breaking in lbs. each tested -lbs. av. when made when broken in soil broken (days) added (35%) load in lbs. per sq. in. First Series 4 56.2 12.89% 3.88% 45% 54 O in. to Ys in. 28,956 359 4 55.8 12.45% 4.06% 45% 54 Ys in. to X in. 31,428 388 4 55.7 13.31 % 4.28% 45% 53 X in. to Yz in. 26,804 330 Second Series 4 43.6 16.01 % 6.21% 45% 60 None 23,757 293 4 • 54.6 12.04% 3.38% 45% 60 O in. to Ys in. 25,345 313 4 53.8 . 11.51 % 3.43% 45% 60 Ys in. to X in. 27,010 333 4 54.2 11.22% 3.82% 45% 60 X in. to Yz in. 17,452 216 I 4 54.8 10.8 % 4.01% 45% 55 Yz in. to % in. 18,547 229 .11 4 54.7 11.81 % 4.28% 45% 60 % in. to 1 Yz in. 13,370 165

Effec.tof Adding Lime #I A brief study was made to determine the fully weighed amount of lime was added to effect of lime on rammed earth. Pure hy­ give each series of test blocks the following drated lime was used and mixed with a care­ percentage of added lime: Three blocks fully prepared soil made up of 62.5 per cent with 1 % of lime, three blocks with 2% of silt and clay, 37.5 per cent total sand and lime, three blocks with 3% of lime, three with 10 per cent moisture. To the lime was blocks with 4% of lime, three blocks with added just enough moisture to give it the 5% of lime, three blocks with 10% of lime, same apparent moisture as the soil. A care- and three blocks containing no lime for 30 Bulletin 277, Revis2d, South D::rkotaExperiment Station checks . The blocks were rammed in four chin e. Th e blocks were tes ted to failure in a layers. Fourteen pounds of the mixture was Riehle machine to determin e the effectof the weighed for each layer of the blocks and the added lime on the compress ive strength of final blocks averaged approximately 56 rammed earth. The operators used in ram­ pounds each. The tes t blocks were rammed min g the blocks were interchanged when on November 26 and Decembe r 3, 19 32, and each layer was partly rammed, thereby elim­ broken on January 7, about five weeks later. in atin g any chance for a variable from this During this interval they were stored in the factor. The strength curve was not quite uni­ res earch laboratory under a temperature of forrn , as the table shows , but there is no approximately 70° F. where the moisture doubt that the lime weakened the tes t was reduced to an average of slightly over 3 blocks , as the check blocks which contain ed per cent, as shown in Table 8. The added no lime were decidedl y stronger. It is proba­ lime had the effect of causing the corners ble that the increment be tween the amounts and edges of the blocks to crumble slightly of li me added should have been greater._ and seemingly in direct proportion to the Slight correction s were made for difference amoun t of lime added. This effect was so in the depth of blocks, which in no case pronounced as to make the blocks delicate to chan ged the order of the resulting strength handle, especially when they were removed figures. The res ults are summarized in from the trays and placed in the testing ma- Table 8.

Table 8. The Effect of Adding Lime Upon the Strength of Rammed Earth Test Blocks (Dimensions of Blocks 9 in. x 9 in. x 9 in.) Number Amount Average ultimate Compressive of blocks of lime added breaking strength in Moisture Moisture of each tested in per cent load in pounds lbs. per sq. in. Kind of soil used when made when broken 3 None 42,500 524 Silt and Clay 61.78% 10% 2.1% total Sand 38.22% 3 1% 32,260 404 10% 2.6% 3 2% 27,250 356 10% 3.7% 3 3% 34,460 436 10% 3.4% 3 4% 33,340 435 10% 3.9% 3 5% 28,590 377 10% 2.0% 3 10% 30,760 405 10% 3.1%

Effectof Mixing Fiber with Rammed Earth upon Its Strength in Comprrssion A total of 28 test pieces was .made for this blocks were made in the same manner using study. Experimental Soil No. 214 was used oat straw, and four were made us ing the for the base soil and the blocks were of gras s sod. This series of blocks was then re­ standard size- 9x9x9 inches. Corrections peated using approximately one-half the were made for slight differences in depth of amount of the same fibrous materials in the blocks. These 'Corrections made no differ­ soil. Eight check blocks were made contain ­ ence in the comparative order of res ults. Three differentkinds of fiberwere added to ing no fiber and compared to the above thes e blocks , viz. , Bax straw, oat straw, and blocks in compress ive strength. The blocks gras s roots. A series of three blocks was contain ing the maximum fiber gave the made to which the Bax straw was added. greatest stren gth, or 438 pounds per square The straw was cut -q p roughly in to len gths inch. Thos e containing one- half of the maxi­ of about fiveinch es. All the straw that could mum fiber came next in strength wi th an be mixed into the soil without havin g it average of 37 0 pounds per square inch, form in bunches was incorporated. Three 14See Table 1. Rammed Earth Walls For FarmBuildings 31 Table 9. Effect of Mixing Fiber with Rammed Earth Upon Its Strength in Compression (Dimensions of Blocks 9 in. x 9 in. x 9 in.)

Compressive Moisture strength Number of blocks when made Moisture when Age Amount in pounds of each tested Kind of soil used average broken average when broken of fiber added per sq. in. 3 Silt and Clay 61.7% 8.93% 3.60% 46 da. Maximum Total Sand 37.2% Oat Straw 485 Maximum 3 8.93% 2.04% 46

while the check blocks containing no fiber might be used and if no covering was used showed the least strength with 325 pounds it would probably cause more rapid weath­ per square inch. All factors such as ram­ ering of the wall surface. This findingagrees ming, moisture content and base soil were with the following statement made by Long closely controlled. This study would indi­ of California in Exp. Sta. Bulletin No. 472 cate that there is some increased strength to -"With an alluvial loam soil, an admixture be expected from adding fiber to the soil in of approximately one-fifthpart of straw by rammed earth work. In most cases there loose volume gave an increased strength should be no need for it, however, and the amounting to 80 per cent in small speci­ fiber spoils the smoothness of the wall. It mens." This is being studied. The data are would interfere with some coverings that summarized in Table 9, above.

Rate of Drying Out of Rammed Earth as Affected byan Admixture of Fiber Such as Straw Observation of test pieces of clay soils in layers is lost, causing this portion to shrink I which straw and other fibrous materials first. If the moisture was lost from the cen­ I had been incorporated seemed to show less ter of the block or wall at the same rate as cracking and checking as they dried out. for the surface, the cause for cracking would The logical reason for this seemed to be be removed. that the straw extending from the center to This study was made to determine if an the outside of the blocks carried the mois­ admixture of straw in pise' walls would aid ture from the center of the block more rap­ in leading the moisture from the center to idly than for those containing no straw. the outside of the wall and thereby reduce Heavy clay soils crack and check on the sur­ surface cracks and, if so, at what rate as com­ face because the moisture from the outside pared to walls with no straw. As is shown in 32 Bulletin277, Revised, South Dakota Experiment Station Table 10 and by the curves in Fig. 18 to exceed six inches. The test blocks were all the results indicate definitely that the straw made on the same day and the moisture used does _not reduce surface cracks by aiding the in the clay was just slightly above optimum. escape of moisture from the center of the The blocks were weighed immediately as wall. It has no appreciable effect upon the they were taken from the form and placed rate of drying out or moisture loss from the on an air-dried board tray of known weight. wall. They were then held at constant room tem­ In the plan for this study three clay soils perature and weighed at the intervals shown were selected and three test pieces were in the table. They were handled on trays, and tray and all was weighed each time to made in each case, from which the average avoid the loss of any of the material. The of the three pieces is recorded in the table loss of moisture only is recorded in the table and curve. Soil No. 1 is fairly heavy, black for purpose of simplification and the loss is clay soil containing 40.4 per cent total clay recorded in pounds. The moisture loss ran colloids. The Pierre clay is a very heavy uniformly with each individual test block gray clay soil containing 50 per cent total and the very slight difference in the rate of clay colloids. Soil No. 2 is a medium yellow, moisture loss was as apt to be in favor of the sandy clay containing 37.3 per cent total clay check block as with the block containing the colloids. Three "check" blocks were straw admixture. Since this study indicates rammed from each soil without any admix­ that moisture loss is not affected by the ture and three blocks were rammed from straw, and since it is quite evident that an each soil to which was added all the straw admixture of straw does reduce cracking, it that could be thoroughly incorporated into is therefore logical to assume that the straw it. The amount was approximately 130 takes up or absorbs a considerable amount pounds of straw to 1000 pounds of soil. Oat of the shrinkage stresses due to its mechan­ straw was used and it was cut in lengths not ical cushioning effect.

Table 10. Summary Sheet for Data and Curve on Rate of Drying Out as Affectedby Fiber Admixtures

Soil No. 1 medium clay* loss of Pierre clay-very heavy* loss of Soil No. 2 light clay* loss of weight in lbs. to date- col. 1 weight in lbs. to date-col. 1 weight in lbs. to date-col. 1

Av. of 3 blocks Av. of 3 blocks Av. of 3 blocks Av. of 3 blocks Av. of 3 blocks Av. of 3 blocks Date weighed with straw without straw with straw without straw with straw without straw Feb. 24, '34 (Date (Date (Date (Date (Date (Date Rammed) Rammed) Rammed) Rammed) Rammed) Rammed) Feb. 27 2.12 2.01 1.58 1.75 1.94 2.02 Mar. 3 3.35 3.45 2.77 2.96 3.15 3.11 Mar. 5 3.95 4.07 3.34 3.50 3.57 3.55 Mar. 8 4.47 4.64 3.81 3.97 3.98 3.88 Mar.11 4.87 4.98 HO 4.30 4.23 4.14 Mar. 20 5.73 5.78 4.92 5.03 4.80 4.60 Mar. 23 5.95 6.02 5.10 5.20 4.92 4.74 Mar. 26 6.15 6.21 5.24 5.35 5.02 4.81 April 1 6.31 6.41 5.42 5.25 5.10 4.94 April 9 6.60 6.61 5.57 5.62 5.23 5.04 April 18 6.79 6.81 5.73 5.80 5.32 5.16

• A description of these three soils is given above .

• Rammed Earth Wa lls For Farm Buildings 33 Reinforcing in Rammed Earth·Construction For the purpose of comparing the value of bottom of the finished beam. They were differentkinds of reinforcing materials that rammed in the bottom of the form that was might be used in rammed earth construc­ built for rnakin g the small weathering tion, 51 short beams were made, using walls.15 A concrete floor furnished the bot­ eight different reinforcing materials. Seven tom of . this form. The reinforcing was of these beams were defective or broken in placed in the following manner: The soil for the making or hauling and were thrown out the first or bottom layer of the beam was of the test. Three of these were the ones in first weighed out. Enough of this soil was which the use of boards was attempted. The then shoveled into the form to make a layer test beams were 36 inches loflg, 12 inches of loose soil two and one-half inches deep. wide and 7 % inches in depth. They were This soil was then leveled off and the rein­ rammed from Experimental Soil No. 2, forcing laid on top and pressed down slight­ having a total sand content of 37.5 per cent ly. The remainder of the soil for the layer and a moisture content averaging 10 per was then shoveled in and the layer rammed. cent when the beams were made. The beams The other two layers 'were then rammed on were rammed in three horizontal layers or top of this one, giying a total depth of 7 % laminations with the reinforcing material inches for the beam. Two forms were used embedded in the bottom layer at approxi­ and two beams w_t:;re rammed at the same mately one and one-half inches from the 15See Fig. 12.

8. No. I 5oi l (/) 7 .&...r CD 11 __) ___.= r-::== 6. � Pierre Clay _- i::;; � ' 7-- ... _L:"p I ' :,r � -- -- I- "' ...-t::::::: -- -r �-'! :r: 5. � v-::... �..11 -· v \.!) /... --,.,..,.-- No:.-. 2.-- Soil�--..,..., � u..14 / r � �,/ s ./.., ,. - z3 '� R.ATE OF ORVI N G OUT lf) 2. //; Cl) ,r f ORR AMMED [ARTH 0 /J . AF FECTED BV FIBER ADMIXTURES. - _J l r AsI I I I I I I I I I I I I I I I I I 0 5 10 15 20 Z5 30 35 -10 "'15 50 55. DRYING PERIOD IN DAYS. Legend: Broken llnes ..Blocks wirhfi loer. Solid lines_ Blocks without fi ber. FIG. 18. THE ADDITION OF STRAW TO WALLS OF PUDDLED EARTH DOES NOT AFFECT THE RATE OF MOISTURE LOSS FROM THE WALL The 9x9x9 inch test pieces of three different soils dried out at the same rate regardless of the admixture of straw. Note the close proximity of broken and solid lines in the curves for each soil. 34 Bulletin 277, Revised, South Dakota Experiment Station time. This allowed for the interchange of reinforcing. The second trial was made with workmen on each layer in order th at any fiv e beams for each kind of reinforcing ex­ diff erence due to the ramming facto r. wo ul d cept that the beams with barbed wire with be reduced to a minimum. The first trial straight ends were not repeated. The second was made wi th th ree be ams for each kind of trial che cked very closely with the first one

Table 11. A Comparison of Reinforcing in Rammed Earth Beams (All beams 7 % in. x 12 in. x 36. in.)

Ultimte MaxilllUID tlo. or Kind Breaking Moment Average Bealll gt Load in in foot Moisture Teeted Reinforcing llumer 9t Placing Pounds, Pounds, When Average Average llroken

8 None '14t> 370 4.32 � 3611 - 3211 !+"- i' llrl&l. IAth , 458 229 3.S9 � ' � � I I I I I I • 11 + 3 Barbed .'fire I I I I I I 643 321.5 3.3 I• ,..JI

I I I I I I � j 9 'I Barbed Wire I I I I 978 489 4.5 �· I I ·. .3 ( l 7 1"' iO\Uld 1091 542.7 s.01 Rods'• � .� �

I I es t" Round 1156 548 4.28 Rode I I I 5 i" Round l 1'1'57 878.S 3.9" Rods � ., � � I I Boards Laid Flat r<:�·<1

No results were obtained on the beams reinforced with boards owing to the fact that difficulty was experi­ enced in keeping the beams intact for testing.

NOTE: As a result of the work with reinforcing at this Station it was concluded that the use of lintels is much more efficient for reinforcing over openings. They should be made of beams the same as for brick walls. Corner reinforcing with boards as mentioned in early writing will reduce the stability of the wall rather than increase it. If corners are to be reinforced, steel reinforcing rods are recommended. In continuous walls no reinforcing has been used in corners at the Station and no sign of failure has been experienced. When two earth walls join, reinforcing rods are recommended. Rammed Earth Walls For Farm Buildings 35 throughout, and the results of both trials strength figures desired were for compara­ are combined and recorded together in the tive strength only, the weight of the be ams table. The be ams averaged 25 6 pounds each, was not included in the figures for the in weight, when they were rammed and maximum moment. Two kinds of reinforc­ they were handled on narrow slat trays ap­ ing materials that were tri ed decreased the proximately four feet long by ten inches strength of the beams materially. The beams wide. with metal lath showed an average maxi­ They were broken in an Olsen testing ma­ mum moment of 229 foot pounds, while the three strands of barbed wire with straight chine as shown in Fig. 2. They were sup­ ends gave an average figure of 321.5 foot ported on two pieces of two-inch pipe which pounds as compared to 37 0 foot pounds for were placed exactly 24 inches on center, the check beams in which no reinforcing making the bearing points exactly two feet was used. All the other kinds of reinforc­ apart, and making the span two feet. A ing, except the boards, increased the strength third short pipe , was laid on the top of the of the beams materially and the �trength beam exactly midway between the supports, varied as follows: Three strands of barbed and the pressure was applied at this mid­ wire with ends hooked, 489 foot pounds; po int until th e beam failed. An attempt was three one- fourth inch round rods with ends made to read the incipient load but fine hooked, 542.7 foot pounds; three one-fourth checks that are often already present in inch round rods with ends straight, 548 earth beams made this figure somewhat un­ foot pounds; three one-half inch round rods certain and no figur e is recorded in the table with ends hooked, 878.5 foot pounds. Hook­ for it. For the check beams in which there ing the ends of the barbed wire increased the was no reinforcing, there was very little de­ strength, while in the case of the rods there flection as the load was applied until the was no advantage shown. The figures are point of rupture was reached and the beams summarized in Table 11 and the arrange­ broke rather squarely across. For the rein­ ment of the reinforcing is also show n. Ex­ forced beams ther e was a very noticeable perimental Soil No. 2 was used in making be nding of the beam before failure. In most these beams and a mechanical anal ysis of cases the defl ection was suffi cient to shear this soil is given in Table 1. The boards the layers of earth apart at the planes of which have been mentioned in early writ­ cleavage which occur between each succes­ ings on this subject not only reduced the sive layer of the beam as it is made . Since strength by the greatest amount but in most the beams were supported in the test at a cases caused the beams to crack and fail be­ point six inches from the ends and since the fore the test.

Foundations for Rammed Earth Walls The study has shown the necessity of prevent capillary moisture from entering it solid masonry foundations for rammed from below. The wall is heavy, weighing on earth walls. If moisture soaks into the wall an average of 120 pounds per cubic foot, and th e physical structure of the soil changes. the foundation must be strong. The founda­ Results are sho wn in Fig. 38 , p. 58. The wall tion must also be as wide at the top as the will tend to expand and soften in much the thickness of the wall. All foundations used same manner as a hard clod of dirt will sof­ have been of concrete and have been found ten after a rain except, �f course, very much very satisfactory. Since rammed earth walls more slowly. A foundation is necessary to are 12 to 24 inches in thickness, and since 36 Bulletin277, Revis2d, South Dakota Experiment Station the foundations should be the same thick­ practice should be followed. Steel reinforc­ ness, such foundations will be expensive to ing rods are also recommended in the foot­ build. It has been generally recommended ings for such buildings. Thick foundations that foundations in frost areas extend below of such depth would be almost prohibitive the frost line for rammed earth walls. For in cost for small farm buildings. Tests were dwelling houses and Jarge buildings this made to determine how deep a foundation

EART H WA LL

II ·------1 2--

:

J,, Steel = Reinforc1nq I

FIG. 19. A TYPE OF CONCRETE FOUNDATION BEING TRIED OUT UNDER LIGHT PISE' WALLS Since the top of the foundation must be as wide as the earth wall, a saving of concrete can be made by reducing the thickness of the foundation between the top and the footing. For walls over 8 ft. in height the full width should be carried down from the top of the foundation more than 6 inches. This distance should increase slightly with the height of the wall. Rammed Earth Walls For Farm Buildings 37 of concrete is necessary in this region. An­ are evident, even in the untreated shallow other test was made for reducing the cost of foundations. In order to make this compari­ foundations fur light buildings by using an son, some of the weathering wall founda­ 8 inch foundation widened at the bottom tions were treated on top with asphalt while for a footing and widened again at the grade others were left unprotected. Certain sec­ line to the thickness of the wall. The plan is tions of foundations were treated also, while shown in Fig. 19 and no absolutely definite other sections were left untreated. While the conclusions have been drawn as to its prac­ study thus far has shown no sign of capil­ ticability. However, no disadvantages are lary moisture coming up through a con­ evident as yet.16 Foundations should extend crete foundation of a reasonably good mix­ 12 inches above the ground. ture, the cost of a waterproofing coat of Waterproofing the Tops of Foundations. heavy asphalt or tar is slight and the practice There is no question but that the rammed is a good safety measure. This is especially earth wall must be protected from capillary true in case of poor drainage. In the case of moisture which might enter the wall from a heavy building where a deep foundation below. In the study an attempt was made·to of a rich mixture of concrete is used there compare methods of waterproofing the tops would be no danger from capillary moisture of foundations, but so far no moisture effects and no need for waterproofing.

Forms for Pise' Walls Forms for rammed earth wall construc­ oil to prevent the lumber from drying and tion should not be made of material less than warping. Furthermore, whenever the forms 1 Yz inches thick. Two-inch planed lumber are not in use, particular care should be is satisfactory. Since only one form of such taken to see that they are standing or lying dimensions as shown in Fig. 20 is necessary in such a way that they will not warp. That for making a complete building, the ex­ is, if they are left leaning against a wall the pense is not excessive. The form shown in top part of the form should be touching the Fig. 20 was still in use after 13 years of ser­ wall its entire length. If the forms are al­ vice and has been used for building walls lowed to become warped, it is extremely dif­ equivalent to six or eight poultry houses. It ficult to level them onto a wall. is in good condition today. Those who have Linseed oil is a good oil to put on the built forms for rammed earth work have forms immediately after they are made, and found a ready rental for them. this may be followed by a coat of ordinary Forms used at this Station are made of paint on the outside, if de_sired. Used crank­ tongue and grooved plank, but it is not ab­ case oil that has been drained from a tractor solutely necessary. However, it is necessary is satisfactory for the inside if two or three that the planks be straight and not warped coats are applied. so that they will fit together and make a straight side wall for the form. It is also true The outward thrust caused by ramming a that the forms will last longer and remain wall is tremendous, making it necessary to in better condition if tongue and grooved use heavy stiffeners or struts on each side of plank are used. Tongue and grooved plank the forms.17 These removable struts should can be secured from the lumber yard by or­ not be more than 30 inches apart and should dering ahead of time or may be obtained be from 4x4 inch stock. Struts made from from a sash and door factory. It is important 3x4 inch stock were tried but were not that these side walls be straight and true or strong enough to hold, so 4x4 inch pieces much trouble will be encountered when try­ were used and gave good service. ing to level the forms so as to obtain a 16The type of foundation shown in Fig. 19 hali proved entire­ ly satisfactory. It has been used under three buildings, with straight wall. As soon as the forms are fin­ walls up to JO feet in height. ished they should be given a coat of linseed 1 •See Figs. 20 and 21. 38 Bulletin 277, Revised, South Dakota Experiment Station

� 26":=:::1..n.- 20needed f fo rm bolts with 3'' of thread on each end Top view �f winq nut showing upset end for threads "O) 2�� ----2.0needed a:) Side view�9·-+J of a£' wm9 nut

• ...... _.L.t b05 It �� 7r k fo r comer l Th ree of each si. ze zneed ed

TO P VIEW OF RAMMED E.ARTH J"x-4"clea ts for

holes ff FIG. 20. PLAN FOR A LARGE FORM FOR RAMMED EARTH WALLS A drawing of the large forms for rammed earth which were used in building the rammed earth poultry house, showing dimensions of the form for making a wall 12 inches thick. It also shows the dimensions of form bolts and wing nuts. The nailing cleats are not shown in the "top view." Rammed Earth Walls For Farm Buildings 39

..rf I

�B2 ,, 3: \o

.• f-;;!--'-==----.,,:::--c'::--i .;;" 1----="----.--"-,-C=---'� .

.,,·.; 4 >-' II ii! ..D ..> i j ., f-- . 21- ---j �.� ,.. 3:IL.!: ,:, �-Zt,--...j '::'�� .... > � Fj ,· .I.. ·1· ·1· ·,· ·. 1 ���". � (�·10,� .,�;,,v�.P"it � .� F � Dt lat· .... � 1 ., Q. � .. :;.; FIG. 21. A PLAN FOR A HINGED FORM FOR LARGE WALLS This form has a gas pipe hinge for building corners having any angle. Otherwise it is similar to the regular form shown in Fig. 20. The bolt lengths shown are for a 14-inch wall and can also be used for a thickness of 16 inches. For thicker walls longer bolts would be necessary. (Designed by H. DeLong.) 40 Bulletin 277,Rev ised, South Dakota Experiment Station To in sure makin g a straight wall it is nec­ essary to use two in ch material for the side s. es sary to use space rs be tween the outside Oilin g the Forms . The oil on the in side of an d in side walls of the form as shown in Fig. the form se ems to work off in to the dirt 20 . To pre ven t sharp corners on buildin gs, while rammin g, makin g it necessary to re­ a 2 in ch diagon al strip was place d on the in­ oil the in side. Use d crankcase oil is satisfac­ side corner of the form an d nailed to on e of tory for this purpose . A light coverin g of oil the in side walls of the form. This makes a is all that is necessary un le ss the soil use d is two in ch be ve l on the corners of all un usually we t. We t soil will stick to the buildin gs. for ms more than dry soils. The stops18 or ends of the form are mov­ Leveling the Forms. In orde r to se cure a able to an y poin t in the form an d the y must straight wall it is necessary to le vel an d also be made of plank. The stop is place d in­ plumb the side walls each time the form is side the end of the form or at wi ndow or se t up. Some time s both side s of the form door openings to form an end to th e se ction will not be plumb or paralle l to each othe r, of wall be in g ramme d. A 2x4 in ch strip ta­ so it is be st to clamp the form to the foun da­ pe re d off should be fastened to the in side of tion or pre ce din g se ction of ramme d earth, the stop so as to form a groove in the end of then le ve l the ouside form wall usin g the the se ction an d thus provide a be tte r bon d space rs to locate the in side wall. The bottom with the next se ction of wall. It is also neces­ form bolts re st on the foun dation or pre ce d­ sary to nail cle ats in side the form to hold the in g se ction of wall to hold the we ight of the stops at an y de sire d place in the form. form. The se bolts may be re move d by Some spe cial me ans must be provide d for poun din g the m, usin g a Yz in ch rod for a fastening the corners on the outside walls of pun ch after the se ction is fin ishe d. the form. A satisfactory me thod use d at this Station is shown in Fig. 20. A 2x8 in ch The form should be se t in place as shown plan k with on e edge planed down to an in Fig. 22, with the form bolts loose . The an gle of 45 ° was bolted to the en d of one struts, space rs, an d stops should be in place . side wall. A 2x4 in ch pie ce with three notch­ Then by usin g a carpenter's le ve l, plumb the es cut at 45 ° an gles was bolted to the end of outs ide wall on each side of the corner. This the othe r side wall. This arran ge me nt all ows may be do ne by eithe r liftin g the corne r for three bolts to cross the corner of the slightly or by liftin g on e end or the othe r as form an d for three bolts paralle l with on e the case may be . When the corner is le ve l, side. This de sign is ve ry similar to othe r de­ tighten the bottom form bolts next to the sign s but is slightly simple r than so me oth­ corner. Also tighten the uppe r bolts with ers. It also allows a srr1 all adjustmen t at the spacers in place . corne r when le ve lin g th e -forms by tighten­ Then take the le ve l to each end in turn in g or loosening the bolts exte ndin g across an d plumb up the end an d clamp it solidly the corner. to the wall. After the corner an d both ends The ove r- all le ngth of the form is almost are plumb, the form bolts alon g each side eleven feet. If it is de sire d to make a build­ may be tightened. Care must be taken not to in g in which in side dimen sion s arc le ss than put an y se ve re side thrust on to the form the le ngth of the in side wall of the form, it un til afte r two or three laye rs are ramme d in will be necessary to shorten the form. How­ th e bo ttom to he lp hold it in place . ever, re gardle ss of the le ngth, it will be nee- 1ssee Fig. 20.

Building a Rammed Earth Poultry House This poultry house was built in farm size , (No. 311) of the "South Dakota Poultry be in g 16 feet wide by 32 fe et lon g an d hav­ House ," havin g a two-thi rds pitch or combi­ in g 12 in ch walls all aroun d. The house nation roof an d a straw loft. A few slight face d the south an d was built afte r the plan changes we re made in plan 31 1 for the Rammed Earth WallsFor Farm Buildings 41 rammed earth walls. The south side wall ing by raising the lower sash. This eliminat­ was made seven feet high and the north wall ed the extra openings in the south side wall fivefeet, and the baffie-board shutter venti­ that would otherwise have been required. lators shown in the south side wall of plan Since the top of the foundation must neces­ 311 were made to fitint o the window open- sarily be the width of the wall, the founda-

FIG. 22. RAMMED EARTH WALL FORMS LEVELED AND CLAMPED TO THE CONCRETE FOUNDATION A. The outside of the form showing the heavy 4x4 inch struts, also the form bolts and wing nuts which hold the struts against the form. Handles as shown on the forms are very convenient when handling and resetting.

B. The inside of the form showing the lx8 inch boards which are fastened to the form with screws. These cleats hold the sections together after the form bolts and struts are removed. At the right the wall-stop is shown just back of the form bolts. Temporary cleats are nailed to the inside of the form on this side of the wall stop or "end gate" to prevent its pushing out. 42 Bulletin 277, Revised, South Dakota Experiment Station

FIG. 23. A LARGE CORNER SECTION COMPLETED Thi� shows the first completed corner section of a rammed earth wall in process of construction. The end groove Is shown at each en� �f the sect10�. When the adjacent sections are built these grooves will be filled and thus make a weather proof Jomt. At the nght background is the shelter for protecting the soil from rains. tion was spread at the top and bo ttom' and a tory tests were made of the mat erials or of savr. ng rn . co ncret e was made.19 A concret e the mo isture in the soil since it was desirable � ixt ure of l _:2Yz :5 was used and the eight that the co nstruct ion wo rk be do ne under mch fo undation was light ly reinfo rced with pract ical condit ions . The proper moisture in three-eight hs inch steel rods at the top and the soil was judged by the hand and by the bo ttom as a safet y meas ure. � ay it wor� ed under the rammer. In judg­ The house :v as built in the spring of 19 32, bet ween Apn l 15 and June 6. The building mg the m01 sture a handful of the soil was of the walls, window and door frames and squeezed toget her and dropped on a hard the fitting of the plat es was do ne by st�dent Boor. It should stick toget her and mo ld in labor at int ermittent int ervals ( mo st of the the hand but when dro pped on the Boor it wo rk was done on week-ends ), and pract ical should break apart in small pieces when the met hods such as would be used in act ual moisture is right . If it is too wet it will not construct io n were fo llowed. ram down into a hard mas s. A general idea The Soil Used . Three kinds of soil were of the amount of sand in ea ch kind of soil used in the walls: The black top soil that being mixed was found by the pract ical test came out of the foundat ion trench; a yellow des cribed heretofore, and the total sand in clay lo am soil similar to Experimental Soil the final mixt ure proba bly averaged close to No. 2, taken fro m a basement excavation in 45 per cent . This was no t the opt imum amount of sand. In fact it was rat her low t�e cit y; and a third, yellow clay loam wit h a d, as expect ed, the shrinkage jo int s wer� � light ly mo re sand in it. The so ils were piled � m the shelt er so that they could be readily wi der than had been experienced in the _ ot her large walls where the soil used co n­ m� xed ?n the mixing board, and they were mi xed m the proport io n that would afford a tained a larger amount of sand. The shrink­ satis factory mo isture cont ent , as some of age jo int s were very easily filled lat er, wit h cement mort ar. them were dri� r than others. The mixing of these three s01ls was do ne by co unt ing the 19Three additional buildings of rammed earth have now been built. In addition, more than 1000 feet of wall for experi­ shovels of soil from each pile. No labora- mental panels has been built. Rammed Earth Walls For Farm Buildings 43

FIG. 24. SHOWING THE SETTING OF A SMALL WINDOW FRAME This picture shows the window frame set in place as the pise' wall is rammed around it. The frame is of 2x12 inch material and the 2x3 inch strips are shown nailed onto the sides next to the wall. An earth wall was then rammed around these strips to make the joint wind proof. A heavy temporary brace of 2-inch material is shown set inside the window frame about eight inches from the bottom. This brace is very necessary and was raised when the sections above were built. When the soil is rammed above the frame vertical braces are installed in a similar way.

Building the Wall. Two forms wer e used mixed on the boar d, moved in a wheelbar­ on these walls par t of the time, since they row and shoveled into the forms by one wer e available, although one lar ge for m is man, while two or thr ee other men did the sufficient for a cr ew of thr ee or even four tamping. Car e was used to have the soil men to wor k. The for ms wer e fir st set up at mixed sufficiently to get the mois ture the corners and rammed as full as des ired. content unifor m thr oughout. The window They wer e then str aightened out, moved fr ames, door fr ame and lower plate wer e all along the foundation and set up for a second made from 2x12 inch plank, making them section of wall and continued ar ound the almos t as wide as the wall. This was done foundation at this height. fo r the added pr otection but it costs quite a It is ver y impor tant to keep the for ms littl e mor e than 2x8 inch mater ial. The 2x8 level and plumb at all times and to finis h the inch mater ial could be us ed in all places ex· top of the section as level as pos s ible as the cep t for the door fr ames. One other advan­ lower bolts of the formre st on the top of the tag e in us ing the 2xl 2 inch fr ames, however, wall in placing them for the next course is that the walls wer e rammed with the win­ above. dow fr ames in place, ther eby getting a Fi lli ng the Forms. The forms wer e fir st tighter fit. The frame was us ed for the end painted on the inside with a coat of us ed of the for m and the ear th rammed right up cr ankcase oil as alr eady des cribed. About against it. A 2x3 inch strip was fir st nailed four inches of loose soil was then shoveled on to the outside of the window fr ame, so into them and leveled oft , after which it was that this would make a weather pr oof joint rammed until per fectly solid, and the pr oc­ ar ound the fr ame when the soil was rammed ess repeated. If the soil does not ram until ar ound it. This thr ee inch strip should be ta­ perfectly har d, the mois ture is not quite per ed to two inches at the outer edge so that right. It is pr obably too wet. The soil was the shrinking for ce will not pull it away 44 Bulletin 277, Revised, South Dakota Experiment Station from the frame to which it is nailed. The attack it, and as expected they worke d on it shrinking of the wall in some cases left open in two or three places suffi ciently to justify joints of one- fourth to one-half inch. These the recommen dation for the practice of plas­ were filledand pointed up with mortar. The tering. At one point a small hole has been mortar was mixed 1 to 4 ( 1part of cement to picked in the wall to a depth of more than 4 parts of finesand) and was mixed very dry two inches. The ba nd of plaster extended 30 so it would not shrink. inches above the floor and at the ends and In ramming the soi l over the window and ba ck of the roo sting alcove. Straight edge door frames an extra plank extending one stri ps were tacked around the wall at the de­ foot in to the wall at each end was used for a sir ed height for a gauge and a plasterer did lintel.20 The reinforcing stucl y indicates that the enti re work in less than three hours' reinforced concrete lintels would be more time. The wall was lightly wet down with a satisfactory for reinforcing here, and that spray of wate r just before plastering. In con­ the practice would be a good one for wide structing the gable ends it was not consid­ openin gs. In ramming over door and win­ ered safe to ram the wall on a sla nt or with dow frames it is necessary to set vertical false the pitch of the roof, because with hard ram­ posts or planks into the frame opening until ming the soil breaks down to the lower level. The end was therefore rammed in horizon­ the wall above is entirely finished.After the 22 wall is finished, ordinary window frames tal sections, leaving a notched effect and were set into this rough frame for the 12- these notches were filled with concrete as light, 10xl 2 inch pane, double hung win­ the roof was framed. For poultry house con­ dows. As the top course of wall was being struction the notches might be made larger, built, long anchor bolts were embedded for thereby requi ring fewer settings of the form. bolting down the plate. These bolts were The author urges the use of rammed earth five-eighths inch bolts 15 inches long with a or of rammed earth blocks for the gable end large flat anchor washer two inches wide by of the buildings. If frame con struction is six inches long and one-fourth inch thi ck. used it will have a much shorter life than The an chor washer was, of course, embed­ the rest of the wall. ded at the bolt head at a depth of 12 inches in Protecting the Walls Durin g Con struc­ the rammd earth, leaving two or three inch­ ti on. During con struction the tops of the es of the threaded end exten ding through the earth walls were carefully protected against wall for securing the 2x12 inch plate on top. rain. During the night and when work was Anchoring the plate is very important in not in progress they were kept covered with rammed earth construction and extr a large a material that would turn the water and roun d washers were used under the nut on prevent its flowing down the surface. Strips top of the plate for this reason. The plate of two- ply roofing were used and made ex­ was of double two inch thickness. The cellent material for this purpose. Sisalkraft un der plate was 2x12 inches and the top paper is also very satisfactory for this pur­ plate was 2x4 inches. The under plate only pose and is chea_r:: er. Th e strips were of such was bolted down and the 2x4 inch top plate lengths that they could be handled by two placed at the outside was securely nailed to men, and a light piece of lumbe r tacked it. The top of the wall was leveled with a along each edge of the strip helped hold it in thick layer of Portland cement mortar under place against the wind. When work was de­ the firstplate. The roof, concrete floor , straw layed so long that the lower section had be­ loft an d inside equipment were put in as for come dry, the top of the wall was sprinkled any frame house. The inside earth wall was plastered where the bi rds were able to reach :·osee Fig. 25. 21This plaster should have contained one-fourth part of cem­ it. Pure Portland cement plaster in the pro­ mix and 3Yzparts of sand to I part of Portland cement. It should have been put on in two coats and the first coat portion of one part of cement to three of should be nailed to the wall with !Od nails immediately 21 after applying. The second coat should follow in a day or sand was used. Two places were left un ­ two. plastered to see how badly the birds might �2See Fig. 25. Rammed Earth Walls For Farm Buildings 45

FIG. 25. THE FINISHED WALLS OF THE RAMMED EARTH POULTRY HOUSE This is an inside view of the poultry house walls, showing one end. Since the gable end of the walls cannot be rammed very satisfactorily on the slant, or with the pitch of the roof, the end wall was notched as shown. The notches were filled with concrete between the frieze board and a form board placed inside as the roof was framed. The 2x12 inch plank over the heavy window frame was satisfactory as a lintel for a light wall. The opening at the peak above the window is for a small shutter ventilator.

FIG. 26. PROTECTING THE TOP OF RAMMED EARTH WALLS DURING CONSTRUCTION The tops of rammed earth walls must be protected from rain at all times while the work is not in progress. Rain falling on the top of a pise' wall tends to soften it and when the rain flows down the side of the wall deep grooves will be cut. Strips of prepared roofing, when available, make an excellent protection. Sisalkraft paper was also found very satisfactory. Light boards tacked along the edge of the strip hold it in place and protect it against the wind. This picture also shows the joints in the wall between the sections as they were built. At the lower center may be seen a wooden block embedded in the wall for a nailing tie. Few of these are needed. 46 Bulletin 277,Revised, South Dakota Experiment Station

FIG. 27. PROTECTING THE TOP OF RAMMED EARTH WALLS DURING CONSTRUCTION

Sisalkraft paper or old strips of prepared roofing are good for the purpose. The lower edge should stand away from the wall. Note the 2x6-inch vertical braces set inside the plank window frame to reinforce it while the wall was being rammed above it.

with water before starti ng to bu ild the sec­ ment mortar which remained entirely firm. tion above. As the walls shri nk ( and the amou nt of An experience in bu ilding this pou ltry shrinkage wi ll depend upon the amou nt of hou se indicates the damage that can be ex­ sand in the soil used) the joints in th e wall pected from heavy rains when proper pro­ will open slightly. These joints were easily tection is not provided. On the day the roof and quickly filled with cement mortar. After was framed and the roof sheeting was b� ing the forms were removed the bolt holes lai d an exceptionally heavy downpou r of th rou gh the wall were left. These bolt holes rai n came. The roof was in just the ri ght were fi lled by tampi ng them fu ll of the same stage of constru cti on to carry the greater cement mortar. A small V-shaped trou gh part of the water down to the wall bu t not abou t ei ght inches long and three inches over the eaves. Thi s cau sed the water to Bow hi gh was used for feeding the mortar into down the wall su rface at many points) where the holes as the tamping was done with a deep grooves were cu t. The damage was the rou nd woode n rod. greatest arou nd the window frames, where The eaves of the rammed earth hou se are considerable repair was requ ired. no wider than ordi narily used, having a hor­ Repai r and Ret ouching of th e Walls. The izontal proj ection of 12 inches. The walls are repair of damaged places in the wall was standing perfectly after 13 years. A blu e­ easily and qu ickly made . In repairing the print plan, No. 312, for this rammed earth deep grooves in the wall a few 8d nails were pou ltry hou se is available. More complete first driven in the bottom of the grooves, not instru ctions for bu ilding a rammed earth closer than two or three inches, leavi ng the pou ltry hou se, inclu ding stu ccoing, are given heads of the nails protru de one-hal f inch. in Sou th Dakota Extension Circu lar No. The cavity was then filled with very dry ce- 362. Rammed Earth Walls For Farm Buildings 47

FIG. 28. REPAIRING HOLES IN A RAMMED EARTH WALL Repairing holes or other defects in a rammed earth wall is easily and quickly done with Portland cement mortar. Such a repair is shown in the above picture. The mortar is made by mixing one part of cement with four parts of sand and making a rather stiff dry mortar. The surface should be moist before applying the mortar. An extra safety measure is to drive a few old nails in the bottom of the hole to be repaired, leaving the heads stick up about one-half inch. 48 Bulletin 277, Revised, South Dakota Experiment Station

FIG. 29. THE SOUTH DAKOTA POULTRY HOUSE BEFORE PAINTING THE WALLS The picture of this experimental house was taken just as it was finished and before it was covered. The spots in the walls that were injured by a heavy rain during construction, were easily and quickly repaired wtih Portland cement mortar. When the walls are left bare, outside window ledges should be provided with metal strips two inches wide extending below the ledge to force the water to drip from the edge instead of flowing down the face of the earth wall. Protection at the corners is most important. A picture of this house is shown on the cover.

Rammed Earth Blocks for Building Walls Rammed ear th building blocks have been of blocks and since that time two inside made and laid into walls in the same man­ walls have been built of them. The blocks ner as for clay or cement building blocks. wer e ade 12 inches wide, by 18 inches Rammed ear th blocks ar e made fr om the long, by 6 inche s deep. They weighed 80 same ki nd of soi l as is used for building the pounds on the aver age. Half blocks wer e monoli thic or solid wall. The same test for rammed for cor ner s and openings. These quali ty of the soi l is used. A sandy soil that blocks wer e la id Bat in the wall, making a 12 is low in total clay colloids will be favor able. inch thickness, and each block laid up ap­ A heavy clay soil will be unfit to use and proximately 120 square inches or seven­ soils ranging in between these two will be eighths of a foot of wall. They wer e found medium in quality. As definitely repor ted ver y heavy to handle in laying, and the siz e in Experi ment Station Bulletin No. 298 , of the for m has be en changed to make these medium soils must be pr otected with a de­ blocks 15 Yz inche s long ( 16 inches with the pendable cover ing. mor tar joint) and with the same width and Siz e and Shape of the Blocks. The fir st depth. This len gth is the same as for most bui ldi ng blocks of rammed ear th wer e made cement blocks that ar e made today. The in 193 3. Two small weather ing walls wer e blo cks could be made in any desir ed size. built of these blocks dur ing the summer. In The advantage in the lar ger block is that the winter of 193 3-34 sever al hundred of the less mortar is requir ed for laying them in blocks wer e made and stor ed away. In the the wall and the fewer mor tar joints offer fall of 1935 a lar ge section of wall ( see Fig. less oppor tunity for the infiltr ation of cold 33), in an experimental building, was built air . Thicker walls would be war mer in wi n- Rammed Earth Walls For Farm Buildings 49 ter and cooler in summer and if thicker determined. As a result of these .findings and walls of this type were made, an 8 inch by 8 knowing the physical characteristics of inch by 16 Yz inch block might be the best dagga plaster intimately, we concluded that size to make and use in building a double a mixture of dagga plaster and IO per cent by wall. The blocks were rammed by hand. volume of Portland cement would make a They were rammed in three layers and with good mortar. We tried it and it has proved the , same ·rammers and intensity as for the so satisfactory we have used no other up to monolithic wall. Mechanical rammers have this time. It bonds with earth even better been used and found exceedingly efficient than common cement mortars and works in making blocks. Two special tools, work­ nicely under the trowel. Its chief merit, of ing somewhat like ice tongs, were designed course, is its low cost. and used in lifting and handling blocks. The complete mixture for this mortar is: Green blocks can be handled immediately Two measures of plaster sand, one measure after being removed from the form but they should be cured for 30 to 60 days before lay­ of sandy clay, and one-third measure of ing into the wall. Portland cement. In mixing with shovels the followi ng ratio is used: Six shovels of Mortar Used for Laying up Wall of sand, three shovels of sandy clay, and one Rammed Earth Blo cks. The mortar used for shovel of Portland cement. laying up walls of these blocks was dagga plaster plus 10 per cent of Portland cement. This same mortar is being tested as a plas­ A few years ago a report was made of some ter covering for pise' walls and after nearly experimental work that was done by the Bu­ eight years' exposure is in almost perfect reau of Agricultural Engineering in Wash­ condition. St riking colors may be sec ured in ington, D. C. In this study varying amounts this plaster from various colored clays. The of Portland cement were added to soils for sandy clay soil contained 46 per cent sand. A mortar and the effectsof the admixture were trial batch of the mortar is advised before

FIG. 30. A FULL-SIZED BUILDING BLOCK OF PISE' AND A HALF-BLOCK OF THE SAME MATERIAL Earth walls made of building block will not be as durable or as weather proof as the solid walls. They are more convenient to use in building gables and inside partitions. Whole blocks of this size will weigh about 75 lbs. on the average after they have dried out. The common floor rammer on the left is sometimes used for going over the loose layer of soil in the foi-m for the first time. It is used more in the wall forms than for build- · ing blocks. The rammer on the right is used for most of the ramming. 50 Bulletin 277, Revised, South Dakota Experiment Station

FIG. 31. A FORM FOR MAKING BUILDING BLOCKS OF RAMMED EARTH This form has a heavy plank bottom and is lined throughout with light galvanized iron. The form is open and this side is dropped down for taking out the blocks. When a concrete floor is available the bottomless form shown in Fig. 32 is handier to use. The blocks in the background are test pieces and were not made in this form.

han d. If che cks appe ar as it drie s, more san d Such forms must be he avily buil t an d easily is ne eded. an d quickly re le ase d for re movin g the bl ocks. They we re lined with light gal van ­ Forms for Making Rammed Earth ize d iron, as shown in the pl an. This elimi­ Block s. Two diffe ren t mol ds or forms we re nate s the nee d for oil in g the forms an d de signed an d buil t for making buil din g works satisfactorily . Furthe r improve me nt bl ocks. Each form had a capacity of four is needed in simpl ify ing the bracing an d in full-sized bl ocks ( se e Figs. 31 an d 32). On e re ducin g the time re quired for re leasin g the of the se forms was made with a pl ank bot­ fin ishe d bl ocks. With the present forms the tom while the othe r is bottomless and must speed of makin g bl ocks with two me n work­ be use d on a sol id con cre te floor. The bot­ in g at a form is 3 bl ocks pe r man hour for tomless form was pre fe rre d by the worke rs. hand work.

Walls of Block Compared to Monolithic Walls For rigid cl imates whe re a we athe r- proof the stan dpoin t of te mpe rature control an d wa ll is of importan ce , the mon ol ithic wall for fire- proof qual itie s the ir advan tages has an advan tage ove r the bl ock wall. In woul d be practically the same . For high durabil ity the mon ol ithic wall has al so walls or high gables the use of bl ocks has shown some advantage . Al though the mor­ shown some advan tage in con struction tar de scribed above has proved ve ry much spee d. supe rior to the mud mortars use d in adobe walls in the past, it will not last through a For buil din g low walls the con struction ce ntury or more of time, as is cl aimed for the spee d will be conside rably in favor of the mon ol ithic walls of earl y history. The life of mon ol ithic rammed earth wall al though no most walls of bl ock or brick materials is tests have be en made toobt ain accurate com­ limite d to the life of the mortar joints. From parative figure s. The buil ding of the bl ock Rammed Earth Walls For Farm Buildings 51

FIG. 32. A FORM WITHOUT A BOTTOM FOR MAKING BUILDING BLOCKS This form is tipped up to show that it has no bottom . It is lighter and easier to handle. Only the ends are lined with metal in this form . A detailed plan for making a similar form is shown in Fig. 34. The blocks in the background are not building blocks.

FIG. 33. A MACHINE SHED WITH RAMMED EARTH WALLS AND A SECTION OF WALL BUILT OF BLOCKS This building is 26 by 72 feet in size. It contaim a section of wall built from blocks. The side and end not showing are covered with paint panels, many of them of trar.sparent paints. This end is covered with dagga plaster and a few narrow panels of plaster are shown at the extreme rear. The roof truss for this building is designed to throw a fairly heavy roof thrust against the walls of the building. The building was two years old when the picture was taken. The gable end of frame construction is not good practice. It should be of a mate­ rial as durable and as �arm as the rest of the wall. 52 Bulletin 277, Revised, South Dakota Experiment Station

Edge

END VIEW TOP VIEW

FIG. 34. PLANS FOR MAKING A FORM FOR BUILDING BLOCKS OF RAMMED EARTH This form is 9 ft. 8 Yz in. long over-all, and has a capacity of five whole blocks and one-half block. Half blocks will be used in about this ratio in building walls. The whole blocks will be 12 inches by 15 Yz inches by 6 inches thick.

walls may seem more rapid because the being a "once over, all over" process. The work is divided into two periods of time, new form for making rammed earth blocks the making of the blocks, and the building will be 9'-8%" long and provides for mak­ of the wall. However, the material is han­ ing five whole blocks and one half block dled several times more in building of each time it is filled. A detailed plan for blocks-the building of the monolithic wall building this form is shown in Fig. 34. Rammed Earth Walls For Farm Buildings 53 Thorough Distribution of Moisture Through the Soil Adds to the Quality of the Rammed Earth Wall General observation in building of mixed. Perhaps the best way to avoid this rammed earth indicates an advantage in situation is to wet down the pile of soil using a soil that is uniformly moist through­ under the shelter occasionally or to wet out. When a soil has been allowed to be­ down and mix the batch on the mixing come very dry under the shelter it is difficult board a week or more before it is to be used to moisten it satisfactorily for immediate and pile it up. In this way the moisture will use. Experience indicates that a better qual­ ity wall will be secured if the moisture is have time to spread through the pile before thoroughly and unifor ml y distributed it is necessary to use it. The use of a tarpau­ throughout the soil when it is rammed. Soil lin for covering the soil aids in keeping it in that is very dry will contain small hard clods good condition. The ideal way is to use it as even after it has been wet down and well it is freshly dug up.

Comparison of a Puddled Earth or Mud with a Rammed Moist Earth-In Compressive Strength In order to study the strength of earth as a the study. These are described on page 10 , as it is affected by the and the sieve analysis for them is given in manner of handling and placing it in the Table 1. No. 1 soil is a black clay soil wall, a series of test pieces was made in the containing very little sand. Soil No. 2 is a laboratory during the second week of Sep­ medium sandy clay soil; while soil No. 3 is a tember, 1937. Three base soils were used in very sandy soil containing very little clay.

FIG. 35. PICTURES OF TEST PIECES OF "PUDDLED EARTH" AND "RAMMED MOIST" SERIES One-third of the test pieces used in the strength study reported in Table 12 are shown in this picture. The cylindrical pieces are eight inches in diameter and were made in heights of 4, 6, and 9 inches. The steel mold used in making them and shown in the foreground is 8 by ·16 inches. Test pieces are now made in this manner. 54 Bulletin 277, Revised, South Dakota Experiment Station Two met hods were compar ed: The on e in checking the results of a former st udy. Four which the soil was mix ed wit h wat er to like pieces of each soi l an d for each dept h form a mud an d with an admixture of an d kin d wer e made, makin g a total of 72 st raw, as eart h is used in cob , chal k, an d test pieces in al l. The soil for the "puddled ad obe con st ruct ion ; the ot her in which the eart h" pieces was taken from the same pile soil is only moist an d rammed in to pl ace as as for the "rammed moist " pieces. The eart h for pise' or rammed eart h. was first thoroughly puddled an d mix ed The test pieces were made in a cylin drical with st raw in a mort ar box. It was then st eel mold 8 in ches in diamet er by 16 in ches placed in the st eel mol d an d rammed into high ( see Fig. 35). The test pieces were pla ce wit h the en d of a 2 by 4 in ch wood made in three different dept hs. These rammer. The moist eart h was rammed in the dept hs were 4 in ches, 6 in ches an d 9 in ches, same mold with an 18- poun d st eel han d an d for such slight variat ion s in dept h as un ­ rammer an d care was used in rammin g to avoidabl y result ed in making them, correc­ see that the pieces were rammed wit h aver­ tion s an d the true st ren gt h are shown in age in tensit y. The cylindri cal han d rammer Col. 10 , Tab le 12. The prin ci pal reason for sho wn in Fig. 16 was used. The in tention usin g test pie<:es of different dept h was to was to ram the test pieces wit h the average try out this new mold for test ing eart h ma­ in tensit y that is used in building rammed terials, an d a secon dary reason was for eart h wal ls. Ea rlier st udy has shown that the

, __ STRENGTH Or PUDDLED EAR.i H COMPARE D -- To 90Q== STRE NGTH Or EAETH RAMMED Mo1ST- =:

800 � IN CoMPR.E.5�toij. ,__ 70 0 ;:? !i rt 1--�.-��L-l ...... _.,__,__,__.__. B =·�·:, 600 .:.:r; {f; El--+--1--+--+--��}il--+--+--+--� 500 tt {�{ .-400 l� ·;_:.;· 300 fl}:.:��� -!�--1-+--+-+-+-4-1!··�-+--+--+--+-� ��� �i� 200 ]} �il1---1---1---1--� l 0 0 },\j iit.. : :'"� lll---1---1---1--� . 0 0 �:,;�;... ;-.. �f No. l So1L No.2 So, L No.3 SotL Leqencl i Pudd led Earth Soil No l Contaitied I0.36 (o5,mct Soil No.2 37.56 /o " ; RIArnmed Moi8t Soll No 3 74.82 1. .,

FIG. 36. PUDDLED EARTH WALLS DO NOT HAVE THE STRENGTH OF RAMMED MOIST WALLS For all different types of soil and the different depths of test pieces the "puddled earth" showed a compressive strength only 43.2 per cent as great as the "rammed moist" pieces. Rammed Earth Walls For Farm Buildings 55 strength of rammed earth walls will vary broken. They were, of course, thoroughly air materially with the intensi ty of ramming as dried, containing from one per cent to two reported in Table 6 of this. bulletin. As and one- half per cent of moisture when each test piece was taken from the mold it broken. The cylindrical tes t pieces with a was weighed and measured and place d on a diameter of 8 inches furnished a bearing shelf in the research laboratory, where the surf ace of 50.27 square inches on top. Col­ entire series was stored in a temperature of umn 9 in Table 12 gives the ultimate 65 to 70° F. until the time of testing. This strength of the cylindrical test piece of this period of time covered almost exactly six cross- section and Column 10 shows the ulti­ months. Straw was added to the puddled mate strength in pounds per square inch of pieces at the rate of 122 pounds for each bearing surf ace. The depth of the test pieces 1, 000 pounds of earth. This is the amount is shown in Column 11 and the decisive in­ recommended for adobe brick by Prof. H. verse ratio of strength to depth of test piece C. Schwalen of the University of Arizona, checks with the former work on this sub­ who., has done experimental work with this ject as recorded in Table 4, page 20 . In type of earth building material. that test which was made for the purpose of The straw was cut in lengths not to ex­ obtaining a correct coefficient for depth of ceed six inches because of the relativel y test piece, the No. 3 base soil only was used. small test pieces. The age of these 72 test The comparison between the two studies pieces was just six months when they were must be made in "s�rength per square inch"

Table 12. A Comparison of Strength in Compression of Earth Building Material When Puddled as a Mud and When Rammed as a Moist Earth

10 11 Strength Number Weight Weight of Loss of Loss of Puddled Ultimate in lbs. of like of pieces pieces when moisture moisture Age Kind mud or strength in per sq. in. Depth of pieces when made broken in lbs. in per cent when of soil rammed compression corrected pieces tested av. of 4 av. of 4 av. of 4 av. of 4 broken (base soils) moist av. of 4 for depth (approx.)

13.62 lbs. 11.36 lbs. 2.27 16.6% 6 mo . 1':o. I rammed 45,040 lbs. 896. 4. in. 16.44 lbs. 14.71 lbs. 1.73 10.5'10 6 mo . No. 2 rammed 50,768 lbs. 1015. 4. in. 16.06 lbs. 14.86 lbs. l.2Q 7.S;'o 6 mo. No. 3 rammed 50,785 lbs. 1010. 4. in. Av. rammed 48,864 lbs. 973.7 4. Ill.

19.94 lbs. 16.85 lbs. 3.09 15.5;'o 6 mo. No. I rammed 34,187 lbs. 676. 6. in. 24.12 lbs. 21.69 lbs. 2.52 10.4% 6 mo. No. 2 rammed 47 ,180 lbs. 936. 6. in. 24.80 lbs. 22.73 lbs. 2.08 8.4% 6 mo. No. 3 rammed 38,062 lbs. 757. 6. in . Av. rammed 39,810 lbs. 790. 6. in.

30.00 lbs. 25.16 lbs. 4.83 ]6.l;' 0 6 mo. No. I rammed 18,000 lbs. 361. 9. Ill. 35.80 lbs. 32.06 lbs. 3.75 10.5;� 6 mo. No. 2 rammed 31,022 lbs. 617. 9. in. 37.40 lbs. 34.44 lbs. 2.94 7.8% 6 mo . No. 3 rammed 25,077 lbs. 499. 9. in. Av. rammed 24,699 lbs. 492.4 9. in.

13.25 lbs. 9.14 lbs. 4. 11 31.0;'0 6 mo. No. I puddled 17,012 lbs. 341. 4. in. 15.62 lbs. 12.48 lbs. 3.15 20.2% 6 mo. No. 2 puddled 25,252 lbs. 519. 4. in. 16.25 lbs. 14.06 lbs. 2.19 13.5% 6 mo. No. 3 puddled 18,380 lbs. 369. 4. in. Av. puddled 20,215 lbs. 410. 4. in.

18.80 lbs. 13.37 lbs. 5.44 28.9'10 6 mo. No. I puddled 12,375 lbs. 243. 6. in . 22.37 lbs. 18.44 lbs. 3.93 13.2;'0 6 mo. No. 2 puddled 21,255 lbs. 428. 6. in. 24.50 lbs. 20.89 lbs. 3.61 14.7% 6 mo. No. 3 puddled 14,IOO lbs. 280. 6. in. Av. puddled 15,910 lbs. 317. 6. in.

28.75 lbs. 20.50 lbs. 8.27 28.7% 6 mo. No. I puddled 11,710 lbs. 233. 9. in . 33.12 lbs. 27.84 lbs. 5.28 15.9% 6 mo. No. 2 puddled 15,450 lbs. 307. 9. in. 34.81 lbs. 30.28 lbs. 4.53 13.0% 6 mo. No. 3 puddled 10,657 lbs. 204. 9. in . Av. puddled 12,606 lbs. 248. 9. in. 56 Bulletin 277, Revised, South Dakota Experiment Station for the two tables, since the test piec es were averaged only 43.2 per cent as great as the of different size and shape. Another fac tor "rammed mo ist" pieces. An interesting enters into the comparison also, due to the ratj o is shown between the loss of moisture differenc e in age of the test piec es as given in the "rammed moist" piec es and the "pud­ in eac h of the tables. dled earth" piec es, as compared to the The results of this study show a dec ided strength of the two materials. The loss in advantage in the strength of earth material strength of the puddled material is no doubt when rammed as a moist earth over the largely due to the honeyc ombed struc ture of same earth material when puddled as mud. the material after the moisture has left it. A The compressive strength of all "puddled similar loss in strength is found in a con­ earth" test piec es, inc luding the three differ­ crete struc ture that is made from a very wet ent types of soil and the different depths, or fluid mix ture.

A Cinder Admixture Study A study is underway to determine the ef­ the mix tures. The cinders caused the mix ­ fec t of adding soft coal cinders to soils that ture to ram slightly quic ker but not quite as are low in sand and somewhat high in clay solid as the sand admix ture. The cinders colloids. As shown in Ex periment Station used were from eastern mine-run coal Bulletin 298 , the addition of sand to soils burned under boilers in a power plant. A that are low in sand content improves the portion of the fine ash was sc reened out of quality of the soil and the resistanc e of the the cinders used in this test, as the perc ent­ rammed earth wall to weathering. Sandy age of fine ash seemed to be higher than soil also rams solid more quickly. A series of average. The sieve analysis of the cinders test piec es was made using base soils No. 1 used showed 79.5 per cent retained on a one­ and No. 2. Both of these soils are improved fourth inc h sc reen, 7.5 per cent retained on a by an addition of sand. To these soils equal one- eighth or No. 8 sc reen, 9.4 per cent was amounts of sand and cinders have been retained on a No. 50 sc reen, and 3.83 per added to two series of test piec es whic h to­ cent passed through the No. 50 sc reen. gether with the chec k piec es will be broken at a late date. (See nex t column. ) This is for NOTE: Sinc e the above report was made comparing the effec t of cinders and sand as in the 1938 edition of this bulletin, final re­ an admix ture, upon the strength and physi­ sults have been sec ured on the cinder- ad­ cal struc ture of the rammed earth piec es. To mix ture study as follows: date two small weathering walls have been The cinders proved to be fully equal to built using cinders as an admix ture. In one sand in stabilizing rammed earth walls. of these walls one part of cinders by volume, They reduc ed both the shrinkage of the tq two parts of No. 2 base soil, was used. In walls and the weathering ac tion on them the other wall one part of cinders was used fully equal to admix tures of sand. The to one part of the same soil. The wall s were strength, in compression, was reduc ed by built for the purpose of comparing their 10 .8 per cent below that of the sand admix­ weather resistanc e. We already have chec k ture but it is still muc h more than ample. walls of this soil in the yard which will be In the early years of st udy it was thought satisfac tory for comparison. that the str ength of rammed earth walls Two conc lusions have been drawn from would be of paramount importance. This the making of th e test piec es. The cinders prov ed tobe untr ue. Resist anc e towe ather­ whic h contained a considerable amount of in g was found to be paramou.nt . Any soil hard burned clinkers definitelyinc rea sed the mixture with favorab le resist ance towe ath­ transverse strength of the material. A sec­ ering will have more than ample st rength ond conc lusion was evident from ramming when rammed . Rammed Earth Walls For Farm Buildings 57 A Few Brief Building Specifications Sandy clay or sandy lo am so ils are mo st ly plan on stuccoing earth walls , ho wever. favorab le of all soils for pi se' or rammed The minimum thicknes s fo r any rammed earth walls. Heavy clay so ils are unfi t fo r earth wall should be 12 inches . The thick­ use . So ils co ntaini ng 18 to 24 per cent to tal nes s should no t be les s than one and one­ clay co lloids may be expected to stand fo r half inches fo r each footof wall height. Fo r many years as a bare earth wall. So ils co n­ dwelli ng ho us es the minimum thicknes s fo r taining 24 to 39 per cent to tal clay co llo ids the lo wer wall should be 18 inches, and 20 or are medium soi ls . They will be perfectly sat­ 22 inches wo uld be better. The extra thick­ isfactory fo r rammed earth walls but will re­ nes s is reco mmended fo r ins ulating advan­ quire a pro tective co vering fo r the exterior tage rather than fo r strength. surface. All of these soi ls will be improved Fo otings fo r the co ncrete fo undation fo r by the addition of sand and many will be earth walls should be ample fo r carrying a improved to a poi nt wh ere they will stand heavy lo ad. They should vary in width from as bare earth walls . Bui lders should general- one and one- fo urth to one and one- half

PLAT E._z\ 12":m Mortar To �vel Top \) � ,• 14 ANCHOR.BOLT ·: a.:WA SH Ell. f�:;-};-;_:_:J .;��-f��-:.· '}·.:�". M

zo"

BASE MENT SIPE �AM MED [AR.TH

·-·i�i{ ,i· ____ t&tfi'.1 ,, s·1 OOTING K4i�f3��' i !f;i/d\) 1--- 22"--I CON C RE:TE BASE MENTWALL Jo1sT SuPPOR.T.S Fo � P1si WA LL. FIG. 37. A SUGGESTED FOOTING AND FOUNDATION PLAN FOR RAMMED EARTH WALLS

While the study is particularly concerned with poultry houses and livestock-building walls, a suggested plan for foundations and joist supports for dwelling house construction is shown above. House plans for brick or other masonry walls would be quite satisfactory for building of rammed earth. 58 Bull:!tin277, Revis:1d, South Dakota Experiment Station

FIG. 38. A FAILURE OF RAMMED EARTH WALLS USED BELOW GROUND Rammed earth cannot be used below ground for building foundations. The rammed earth walls on the in­ side ot this small experimental root cellar have caved and failed completely. Waterproofing used next to the soil on several panels helped only a very little. The walls were finished in October, 1938, and the walls failed completely in March, 1941. The exterior walls above ground were c9vered with stucco.

times the thickness of the wall, depending "Pre-cast tile beam Boors" lend them­ upo n the height of the wall and the bearing selves well to fire-proof co nstruction in strength of the so il. rammed earth structures. They may be used The top of the fo undation must be of the fo r Bat ro of co nstructio n as well as fo r same v.-idth as the thickness of the wall. Boo rs. This fu ll thickness must ex tend fo r a dis­ Rammed earth blo cks are practical fo r tance of one- half the thickness of the wall partition co nstruction where fireproo fing is belo w the to p, when the special type fo un­ important. Twelve-inch partitions will be dation is used. satisfacto ry fo r dwelling ho use co nstruction. Plank plates sho uld be anchored to the Ordinary frame partition co nst ruction can earth wall by bo lts that are embedded in the be used very satisfactorily in rammed earth wall to a depth equal to the thickness of the buildings. The great advantage of this ma­ wall at the plate. The bo lt sho uld carry an terial is in the outside walls, where its insu­ anchor washer or plate one- fo urth inch thick lating value is mo st effective. and one square inch in area fo r each inch in If thin walls are used it is no t advisable to thickness of the wall. leave them unfinished and ex po sed to a ho t Sills or plates fo r carrying joists on a drying sun fo r lo ng perio ds. To o rapid dry­ rammed earth wall may be of pl ank or of ing of the side ex po sed to the sun may cause co ncerte. In no case sho uld the ends of the the wall to warp slightly. One lo ng section joists rest directly on the earth wall. Fo r of twelve-inch wall left standing throughout no rmal Boor lo ads the ledge fo r carrying the the summer was pulled out of line at the plate and jo ist ends sho uld be no t less than to p by two or three inches in a lengt h of 40 six inches ( see Fig. 37). feet. Rammed Earth Walls For Farm Buildings 59

FIG. 39. A SMALL DWELLING HOUSE BUILT WITH RAMMED EARTH WALLS IN PENNSYLVANIA This attractive little house was built by the Pennsylvania Housing and Town Planning Association of Phila­ delphia. Rammed earth construction lends itself to simple low wails with few window openings. Old Spanish , which is popular in California, calls for a low, rambling, single-story house with few windows and a comparatively flat roof. Note the excellent proportions of this house. Window recesses on the outside add to the building and identify the earth wall. Special window ledge construction must be provided for carrying the water off the outer edge of the ledge.

If it is neces sary to leave unfinished wall out and the mois ture should be adde d to the sections stand for more than three or four dry soil some time be fore it is used. This weeks in hot drying weather before ins tall­ give s the mois ture time to spread through ing the roof, some sort of shade or covering the dry particles. The period of standing in would be advis able. · the pile should not be les s than ove rnight, The tops of unfinished walls must be pro­ and a longer period is better. tect ed against rain at all time s during con­ structi on. Fig. 26 shows methods of tacking Good concrete foundations were neces­ l tough building paper ove r the top of the sary without exception for walls of rammed walls for this purpos e. The lower edge s of earth. The y should extend 12 inches above this paper mus t be he ld away from the wall ground. Shallow foundations were satisfac­ to direct the flowing wate r away from the tory under low poultry hous e walls whe n wall face. reinforced at top and bottom as shown in When ve ry dry soil is being used for Fig. 19. All dwelling house found ations building, the dry clods should be screened should extend below the fros t line .

Summary and Comments Ramme d earth or pise' walls are excellent for the greatest benefits, as the ir ins ulating in ins ulating quality, making an exceeding- quality increas es directly with the thicknes s ly warm wall in cold we ather and a cool wall of the earth wall. In addition to being a in hot summer. They should be made thick good ins ulator, rammed earth walls are ex- 60 Bulletin 277, Revised, South Dakota Experiment Station

FIG. 40. A MINNESOTA DWELLING HOUSE OF RAMMED EARTH This house was built near McGregor, Minnesota, by Mamie B. Nelson in 1938. Just the walls of the main house are built of rammed earth. The entry and porch are of frame construction. This is an example of a con­ ventional roof used with pise' walls in an attractive setting of birch timber. tremely stable. They are also fire proof, hou se shown on the cover of this bu lletin du rable, and weather proof. Rammed earth averaged, in a three-year temperatu re stu dy, is probab ly the most nearly weather proof of 5.9° F. warmer in early morning than a any wall material used today, having insu lat­ well-bu ilt frame hou se of the same size, ing qu alities, and du e to this fact, it lends dimensions and design. This was for the itself well to modern air conditioning.How­ five coldest months of the year. ever, the pu rpose of the Experiment Station The speed of bu ilding the solid rammed in stu dying this material for wall constru c­ earth wall will vary from 1 Yz to 2 cubic feet tion was not for dwelling hou se constru c­ of wall per man hou r depending upon the tion bu t for the benefit of the pou ltryman experience of the crew in planning the work and stockman. We are interested in the and changing the forms. Mechanical ram­ weather-proof properties of rammed earth mers, driven by compressed air, rammed as walls rather than their low cost. high as 7 cubic feet per hou r. Rammed earth walls are not temporary A sandy or comparativ ely li ght sandy soil in any sense. They are the most permanent is a favorable soil for building ear th walls, of walls. They are somewhat tediou s to and a heav y clay soil is unfit for use. An bu ild and when the wall is finished the rest av er age or mediu m quali ty so il will no t of the bu ilding shou ld be well bu ilt and stand satisfactori ly as a bare wall but must tightly fitted so that the valu e of the insu­ be pr otec ted with a covering of som e mate­ lated walls will not be lost. Perhaps the :nost ri al such as stucco. valu ab le use of these walls is for the pou ltry It is the sand in the wall that resists the house, th e constru ction of which is ou tlined driving rains. Up to the present time no en­ in Extension Circu lar 362. The pou ltry tirely dependable ou tside covering except Rammed Earth Wa lls For Farm Buildings 61 plasters has been proved, although ordinary Rammed earth block walls will not be as good quality linseed oil paints have stood weather proof as the solid wall. Building for five years on very sandy earth walls. with them may be more convenient for some who like to divide the building time Screening the soil for rammed earth con­ into the two periods: making the blocks, and struction is necessary only when dry clods laying them in the wall. Building the solid are found in it or when it contains undesir­ wall is a "once over, all over" method and able trash. It is difficult to moisten the drv the total building time will be less for this clods to their center for ramming and ther�­ type. Blocks are more convenient to use in fore best to screen them out. high work such as the high gable ends of a Adding Portland cement to very sandy building, and for partition walls. soils and especially finesandy soils decidedly An experienced crew will build a mono­ increased the stre ngth. Adding cement to lithic rammed earth wall in less time than is soils low in sand increased the strength very required for them to make adobe brick and little, if any. then lay the bric k into a wall. Adding hydrated lime to the soil reduced Hand rammers for building walls are the strength materially and made the mate­ readily made in the local welding shop. If rial cru mbly. It did not reduce the resistance mad<: according to the suggestions, they will to weathering. be durable and well balanced. Window ledges should be made to direct The mechanical air rammer was used for the flow of water directly from their outer edge to the ground. Ordinary window building the last large poultry house on the ledges will carry the flow of water back un­ College Poultry Farm. It not only did sat­ derneath to the surface of the wall. The isfactory work but reduced the building only trouble experienced with pise' walls time materially. Two air hammers could be from driving rains was at this point, where used off the same large compressor and thus even the best walls were damaged. reduce the ramming time proportionately.

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FIG. 41. PROTECTION FOR AN OUTSIDE WINDOW LEDGE A close-up view of an outside window ledge in a rammed earth poultry house wall. Note the metal strip nailed around the edge to force the water from heavy rains to drop from the outer edge. Without the metal strip this water will run back under the ledge and flow down the face of the wall. Bare walls will suffer damage from this water. 62 Bulletin 277, Revised, South Dakota Experiment Station Orga nic ma tter in ordi na ry top-soil will not injure the quality of earth wa lls exc ept in ca ses where Portla nd ce ment is used as a stabilizer. Top-soil containing an unus ual amount of orga nic ma tter should not be used.

FIG. 43. AIR COMPRESSOR AND AIR HAMMER EQUIPMENT FOR RAMMING EARTH WALLS This mechanical rammer has been used in recent years of the work and has been found very satisfac­ tory. It is conventional equipment except the square­ faced aluminum rammer-head, which was substi­ tuted for the conventional head that came with the floor hammer. This equipment was purchased in 1936 at a cost of around $500, including flexible cord for connecting up with electric power line and other miscellaneous items. The use of mechanical equipment speeds up the work of building rammed earth walls and reduces the cost materially. The floorhammer and air hose cost $110. The air compressor, tank and motor rails cost $218.83 and the secondhand, 2-horse electric motor cost $85. The air compressor has a capacity of 16.3 cu. ft. of air per minute. This is the minimum size recommended for driving a single hammer. FIG. 42. AN AIR HAMMER AT WORK PACK­ ING THE SOIL IN THE FORMS FOR A RAMMED EARTH WALL This is a small compressed air floor-rammer. The man at the left is working the air hammer. The air is conveyed to the air hammer through a large flexi­ ble hose which is shown. The flexible electric cord connecting the electric motor with the power line is shown in the foreground. The connection is seen just above the switch box on top of the compressed air tank. This compressor proved to be too small for the purpose. The compressor shown in Fig. 43 is the minimum size recommended for this work.

The only change ma de in the conventiona l air floor ra mmer wa s to ha ve a square alu­ mi num ra mmer head substituted for the cyli ndrica l steel hea d. Either ga s engi ne or electric power can be used to dri ve the com­ pres sor. Ea rth wa lls are not rec ommended in loca ­ ti ons where they would be inunda ted from flood wa ter. Coars e aggrega te is of no adva nta ge in ra mmed ea rth wa lls. It decreases the strength if too much is present. Ital so inter­ feres wi th nailing of stucco wire. Rammed Earth Walls Fo1' Farm Buildings 63 A List of Reference Books and Literature on Pise' Construction NOTE: Rather than to quote extensively A book, "Cottage Building in Cob, Pise, earlier work that has been done on pise' de Chalk and Clay," by Clough Williams­ terre construction, the authors wish to list Ellis. Distributed by Charles Scribners Sons, the following references dealing with the New York City. subject. Single copies of the bulletins listed can usually be obtained free of charge, while A booklet, "Lower Cost Buildings," by the books can be obtained at a very reason­ E. W. Coffin and H. B. Humphrey, The able cost. Publicity Corporation, 22 Thames St., New York City. No longer available. Farmers' Bulletin No. 1500, "Rammed A booklet, "Modern Pise' Buildings," by Earth Walls for Buildings," United States Karl J. Ellington, Port Angeles, Wash. Department of Agriculture. A booklet, "Special Report No. 5," Build­ Bulletin No. 472, California Agricultural ing Research Board, London, England. No Experiment Station, Berkeley, California. longer available.

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