Recycling Concrete and Masonry

information - I . I

. ~~~VIRONMENTAL Recycling Concrete and COUNCIL of-CONCRETE. ORGANIZATIONS Masonry. : 1 5420 Old Orchard Road Skokie, Illinois Old concrete and masonry that have alternative for new road, street, and highway “reached the end of the road” can be recycled construction. As early as 1987,more than 1000 , 60077-I 083 and bsed not only as aggregate for r&w con- lane miles of portland cement concrete pave- 800 994-ECCO (3226) crete, but also for a number of other applica- ment had been recycled into new pavemeht. FAX (847) 966-8389 tions in construction. In the U.S. there are no Concrete recycling to produce structural longer any barriers to the use of recycled con- grade concrete for non-ptiement uses is tech- crete as aggregate in new concrete. Since 1982 nically feasible, with certain precautions. For the ASTM definition of coarse aggregate has example, it is generally accepted that when -included crushed hydraulic cement concrete, natural sand is used, up to 30% of natural and the definition of manufactured sand crushed aggregate can be replaced with coarse includes crushed concrete fines. Similarly, the recycled aggregate without significantly U.S. Army Corps of Engineers and the affectink any of the mechanical properties of Federal Highway Administration encourage the concrete.2 w the use of recycled concrete as aggregate in their specifications and guides.’ Advantages of Recycling The technology of concrete recycling is well established in the U.S. Recycling of port- Environmental considerations. In this time of . land cement concrete, as well as asphaltic con- increasing attention to the environmental crete, has been shown to be a cost-effective impact of construction and sustainable devel- opment, por‘tland cement concrete has much to offer: (1) it is resource efficient-minimiz- ing depletion of our natural resources; (2) it is inert-making it an ideal medium in which to recycle waste or industrial byproducts, such as fly ash; (3) it is energy efficient-in a cra- dle-to-grave study on the impact of energy expended in all phases of production, concrete ‘was superior to wood and steel; (4) it is’ durable-continuing to gain strength with ~ time; and finally (5) it is recyclable-fresh concrete is used on an as-needed basis (whatever is left over can be reused or reclaimed as aggregate), and old hardened concrete can be recycled and used as aggregate in new concrete or as fill and pavement base material.

_____~ -. -____ Econ,omic factors. Recycling concrete is an attractive option for governmental agenciesand - Bird’s eye view of a concrete recycling plant and stockpile. / contractors alike. Most municipalities impose tight env~ronmental controls over opening of Conventional concrete. Concrete manufactured new aggregate sources. In many areas, zoning from portland cement, water, and a combina- requirements and public rancor—’’not in my tion of fine and coarse aggregate; the fine aggre- backyard sensibilities-limit the possibility or, gate is usually natural sand, and the coarse increase the cost of starting new. quarries. For aggregate is usually gravel or cmshed stone. demolition contractors landfill space is scarce, Also referred to as original concrete, old con- especially in urban areas. Some landfills may crete, and demolished concrete. \ not accept construction materials, and disposal of old concrete and masonry is costly. Also, Ciushed concrete. Concrete made with ASTM ‘ dumping fees will most likely rise as construc- C150 portland cements, AS~ C595 port@d- tion debris increases and the number of acces- pozzolan cements or portland blast-furnace slag sible landfills decreases. Furthermore, the cost cement, natural or manufactured sand, or a com- dnd transport distances of conventional aggre- bination thereof, and coarse aggregates such as gates could continue to increase as sources na~ral graveI, crushed gravel, crushed stone, air- grow scarce. With re+cled aggregates there is cooled blast-f&nace sla& or a combination there- potential for cost savings in hauling. It is not of. Crushed concrete made with other materials I unusual for contractors to haul conventional is beyond the scope of this publication. aggregates 50 to 70 miles on projects, and ~aul Original aggregates, Conventional fine and distances greater than 200 miles are not coarse aggregates from which original concrete is uncQmmon.+ produced. The fine aggregate is usually natur~ or manufactured sand; the coarse aggregate is Applications for Reqcled . “ usually gravel or crushed stone. Original aggre- Concrete and Masonry ‘ gates may also be referred to as virgin or conventional aggregates. Recycled concrete is being used to produce aggregates for (1) many types of general Original mortar, A hardened mixture of ‘ bulk fills; (2) base or fill for drainage struc- cement, water, and fine, aggregate,’10iJ% of tures; (3) pavement subbases; (4) soil-cement which passes the 3/8-in. sieve, in the original pavement bases; (5) lean-concrete or econo- concrete, Some original mortar is usually crete bases; (6) bituminous concrete; and (7) attached to particles of original aggregate in new concrete for pavements shoulders, medi- recycled concrete aggregates, an barriers, sidewalks, curbs and gutters, ‘Recycled-aggregate concrete. Concrete manu- building and bridge foundations, and even factured from recycled aggregates or a combi- structural grade concrete. nation of recycled and conventional aggre- Crtished brick rubble maybe used as an gates such as sand, gravel, or crushed stone. aggregate for lightweight concrete, and Also referred to as new concrete. ‘ ‘ crushed masonry aggregate from various types of demolition debris can be used in the Recycled concrete aggregates. Fine and coarse precast concrete industry perhaps in con- aggregates Produced. by crushing of original crete block. Common brick from demolition comcrete. Also maybe referred to as recycled ‘ projects in the Chicago area is cleaned and aggregates. Fine recycled aggregate may also , palletized on-site and shipped to the South be referred to as crushed concrete fines. for use in expensive homes. Crushed masonry aggregate has been used for unbended Recycled concrete. Hardened concrete that has pavement bases, and in some regions of the been processed for reuse, usually as aggregate. U.S. it-is a popular landscaping rock. Crushed concrete block and brick have been Waste concrete, Concrete debris from demol- “ used experimentally as aggregate for grout- ished pavements and structures, leftover ing new concrete masonry walls.3 ready mixed concrete, rejected ready fnixed concr$e, and r,ejected precast or precast/ pre- stressed concrete products. RecyclingDemolished Concrete Demolition of Old Concrete and ‘ Removal of Steel Terminology Recycled concrete is simply old concrete To avoid confusion, the following termi- that has been demolished and removed from nology, will be used in this publication: pavements, bridges, foundations, or buildings r .

,.. \

,“,

—

COMPRESSION CRUSHERS

CONEi JAW “ .

Broken, Concrete Feed Breaking Cone Plates / 1 . \ ,/

Jaw Break Swing, Jaw ‘ Plate . , Cr ,. Concretf7 I 1+ -.. . / E 0 JEiW -’ Discharge stationary ‘!!7$I , + ‘ L Jaw Break Eccentric “. , ,Plate Flotation Crushed Concrete Discharge > “IMPACT CRUSHERS !

VERTICAL HORIZONTAL ._ Broken Cqncrete Primary Break Plate ‘ Feed Impact Secondary Rotor/ lmpellors “Break “ti Plate . .

I + . + .,

\ Crushed Crushed ‘ Concrete Concrete ‘ Crushed Discharge “ Discharge Concrete ~ ‘ .’ ‘ Discharge ,. . . ,.

Three basic types of stone crfishers. Note that impact crushers maybe designed to operate vertically or horizontally. . / and crushed into various sizes for reuse. aggregate.size is set. In North America, 61% of ’ Reinforcing.steel and other embedded items, recyclerz use jaw crushers for primary crushing, if any, must be removed, and care must be and 43% use cone crushers for secondary crush- taken to prevent contamination by dirt or ing.5 Recyclers often prefer a jaw crusher 7, other wasted building materials, such as plas- because it can handle large pieces of concrete; a ter or gypsum, or asphalt from pavements, cone crusher, on the other hand, can handle _ u which can be troublesome. It is advantageous fragments no bigger than 8 in. if old concrete can be freed from foreign mat- ter before demolition begins. Yield. The yield of coarse aggregate from a recy- In the early days of recycling there was cling operation depends on the type of concrete some concern regarding the removal of rein- being recycled. Yield losses for “clean” con- forcing steel bars and welded wire mesh from crete-plain concrete pavement, sidewalks, concrete. However, it has proven to be fairly curbs and gutters-are negligible. Crushing easy to separate steel from original concrete operations typically yield about 75% coarse through the ingenuity of demolition contrac’ aggregate and 25% fine aggregate. However, a 1 tors and innovations in breaking, removal, lower yield of recycled coarse aggregate should crushing, and screening equipment. be expected when the gradation requirements Recordsof the history of an old concrete call for a smaller top size. building, bridge, or pavement-such as those , detailing quality and composition-are vale- Noise an8 dtlst. Crushing and screening opera- A able documents,. if available. Such records may tions in a recycling plant are always accompa- indicate the strengths and mixture designs of, nied by noise: vibrations, and dust. Also, there the original concrete, and this information are aesthetic concerns and the intrusion of .’ I would-be useful in determining the recycling trucking into areas where it may be undesirable. potential of the concrete. Consequently, when locating a recycling plant, environmental considerations and legal require- Production of Recycled Aggregates ments must be carefully studied and necessary counter-measures taken. Nonetheless, concerns Plants for production of recycled con- about noise and dust problems when crushing. crete aggregates are not much different from concrete in mobile plants in urban areas have L-0, plants engaged in the production’of conven- been exaggerated. tional crushed stone aggregates. The National Stone Association (NSA) and its member Removing contaminants. Clean concrete can- companies recognize and accept the recycling not always be supplied by a demolition con- of many construction waste materials, such tractor. Concrete rubble often includes conta- as portland cement concrete, when it is cost minants such as-admixtures, asphalt, chlo- I effective. NSA believes recycling (1) con- rides, cladding, soil and clay balls, glass, gyp- . serves natural resources, (2) is good for the sum board, hardboard, iron, joint sealants, environment, (3) can be good business, and s (4) is expected to grow? _ I Crushing aggregates. The same basic equipment used to process virgin aggregates also is’ used to crush, size, and stockpile recycled concrete aggregates.

Crushers.The two basic types of crushers are compression crushers and impact crushers. Most, recycling plants have both brimary and secondary crushers, however, some plants produce aggregates by primary crushing only. In plants with both levels of crushing, the primary crusher normally reduces the material down to about 3 / 4 in. The material then passes through two screens that separate the aggregate into sizes, greater than and less than 3 / 8 Recycled concrete aggregate looks like in. The larger material is fed to the secondary crushed stone. crusher where the maximum desired coarse .~ - --. * lightweight brick and concrete, paper, plaster, plastics, rubber, steel reinforcement, tile, vinyl, wood, and roofing materials of variouskinds. Contaminants are mostly a concern when recycled aggregates are to be used in new concrete. Dust and fines that cling to the large coarse aggregate particles are of little conse- quence in recycled aggregate concrete, and washing is not required. Contaminants usually are of no concern in base aggregateapplications, except in caseswhere the recycled aggregatewill be used in an unstabi- Stockpile of broken concrete ready for lized permeable base.In such instances,drain crushing. water may wash dust and fine material off the aggregate.This leachate can settle on filter fabric original concrete can be expected to pass the . or drainpipes before reaching drainage outlets, same tests required of conventional aggregates. clogging pipes, binding filter fabric, and ultimate- ly causing system failure. However, washing the Gradation. Reasonably well-graded coarserecy- recycled aggregatescan correct this problem. cled aggregatescan be produced with a jaw - crusher. With proper crusher and screen selec- Soil and day balls. Soil and clay balls can be espe- tion, a plant can meet ASTM and American cially troublesome. Tests show that introduction Association of State Highway and Transportation of excessive clay int0.a concrete mixture increases Officials (AASHTO) gradation specifications. water demand and reduces strength. Clay balls With adjustments a crushing plant can produce can causepopouts if located near a slab surface. any desired gradahon. Accordingly, specifiers Some recycling contractors use a l-in. scalping should call for the same gradation rangesfor \ screen ahead of the primary crusher to remove I recycled concrete coarse aggregate as they would soil and clay balls from broken concrete. How- for conventional aggregates. ’ ’ ever, this step may not be necessaryif care is ’ ’ taken by the loader operator to exclude soil or Particle shape. Recycled concrete aggregate is base material while removing old concrete in similar to crushed rock in particle shape. contact with the ground-foundations, floors, Demolished plain and reinforced concrete can be pavements, walks, curbs and gutters, etc. crushed-in various types of crushers to provide recycled aggregate with an acceptableparticle. Limits. In standard specifications for recycled , shape,but the type of crushing equipment influ- aggregates,there should be maximum allowable encesthe gradation and other characteristicsof limits on contaminants, such as asphalt, gypsum, crushed concrete fines. Usually the fine material ’ organic substances(wood, textile fabric, paper, will be more angular, with a higher rate of ’ joint sealants,paints, etc.), soil, chlorides, and absorption and a lower specific gravity-qualities ’ glass. Limits are suggested for various contami- not conducive to making workable conctete mix- nants, usually by volume or weight percentage tures. Becauseof this, some researchersdo not of the recycled aggregate:(1) asphalt-l% by vol- recommend the use of fine recycled aggregates ume; (2) gypsum--O.5% by weight of S03; (3) for the production of new concrete.While many organic substances-&l5% by weight; (4) soil- contractors use some recycled fines in Iheir con- seelimits in ASTM C 33, Speujkh’onfor Concrete ‘aete mix designs-usually about 10% to 20% by Aggtptes; (5) chlorides--see limits in AC1 318, weight of the total fine aggregate-others have Building CodeRequirements for R&forced Concrete; used 100%recycled fine and coarseaggregates and (6) glass--none should be tolerated, since successfully. conventional glass can cause alkali-silica reaction, as well as cracking and popouts in concrete. Texture. When old concrete is crushed, some of + the original aggregate particles split; jaw crushers Characteristics of Recycled Abegates produce a smaller proportion of split particles than impact crushers. Typically 30% to 60% by The crushing characteristics of hardened volume of old mortar will adhere to recycled ‘L concrete are similar to those of natural rock and coarse aggregate particles, depending on the are not significantly affected by the grade or aggregate size. More old mortar is attached to the . quality of the original concrete. Recycled aggre: smaller size fractions of coarseaggregate. From gatesproduced from all but the poorest quality 20% to 65% by volume of old cement paste will adhere to recycled fine aggregate particles, with pass these requirements. Typical abrasion losses the finer material containing the mm-t old paste. for recycled aggregates range from 20% to 45%, As previously noted, crushed concrete fines tend The up,per limit for pavement aggregates is to be somewhat coarser and more angular than ,.50~o.A good service record-5 years or more- desirable. But gradation of the recycled fines, and with a similar recycled aggregate concrete, hardiness and workability of the concrete made under the same service and exposure condi- with them, can be improved by the addition of tions, will satisfy some specifications. . / fine natural blending sand. w Sulfate soundness. Research on use of the Specific gravity. Because of the large amount of sodium sulfate or magnesium sulfate test old mortar and cement paste adhering to recy- (ASTM C 88) for determining the soundness cled aggregates, their specific gravity (relative (resistance to weathering) of concrete made density) will be 5% to 10% lower than that of the from recycled aggregates is misleading. U.S. virgin aggregates in old concrete, Typical values results conflict with those from other coun- of specific gravity of recycled aggregates range tries. Accordingly resistance to weathering of between 2.2 and 2.5 in the saturated surface dry a recycled concrete aggregate usually is con- condition. sidered acceptable without running the sulfate ~ soundness test if the recycled concrete was Absorption. The water absorption of recycled durable in its previous life. concrete aggregates is much higher than that of the virgin aggregates in old concrete due tq the Alkali-silica reactivity (ASR). An investigation large amounts of old mortar and cement paite was made.,into precautions needed to prevent ‘ -” @ached to recycled aggregates. Absorption val- expansive ASR when ASR-affected concrete is ues typically range from 20/.to 6°Afor coarse recycled as coarse aggregate in new concrete! It recycled aggregate~s Absorption rates for was determined that potential for ASR in new crushed concrete fines range from 4% to 8Yo?Pre- conc~te was affected by old concrete’s original soaking of recycled aggregates is sometimes rec- alkali level and extent of expansion, and the onynended to help maintain’ uniformity of remaining potential reactivity of the recycled I absorption during concrete production. ag~gate. Also, the alkali content of new concrete had a significant effect on subsequent expansion Abrasion loss. The abrasion resistance of aggre- due to ASR. The use of a low-lime ASTM Class gate is important in concrete pavements and F fly ash greatly Educed expatwion due to ASR floor slabs. It is measured by use of the Los in new concrete, This research demonstrated Angeles (LA) abrasion test (ASTM C 131 or C that with appropriate selection ~f cernentitious 535). Recycled aggregates produced from all but materials, even recycled concrete containing the poorest quality coficrete can be expected to highly reactive aggregate cube used safely.

., ‘ Table 1. Some ty icd mncrete mix designs fr6 . .

Wisconsin s DOT ib per cu yd ,- Cement (Type 1) .:472 ; 480 400 ~Fly ash (Type C) 83’ “110 130 Water 255 265 230 Recycled CA 1630 ‘ 1815 , .1650 “ , Virgin CA . — — ~Recyci,ed FA ,, .— Vir~in FA, 1200 Admixtures: . ~r enlrained S’yes ‘ yes Water reducer no no

*Adapted from Refer&nces 6 arrd 7. —

, .

~‘Characteristics of Fresh Recycied- concrete contains recycled coarse aggregate Aggregate Concrete and natural sand. A water-cement ratio adjustment will have to be made if a trial . Mixture design.’The same principles used to mix design shows that compressive strength design concrete mixtures with conventional is lower than initially assumed. . aggregates-sand, gravel, or crushed ston+- should be followed when using recycled aggre- Cement content. The calculated cement content gates. ,Trial mixtures are required to determine for recycled-aggregate concrete will be some- proper proportions and to check new concrete~s what higher than the cement content for a com- quality. Table 1 shows a few typicaJ concrete mix parable conventional concrete because of the , designs. higher free water requirements of recycled con- Because of the high absorption of recycled crete mixtures. At least .5?!.eXtra cement would . aggregates, some deviation in trial batch be required in mixtures using coarse recycled weights will likely be necessary. The concrete aggregates and virgin fines; at least 15% extra , mix design engineer must be vigilant in deter- would be needed if both coarse and fine recy- t mining the necessary quantity of mixing water cled aggregates were used. In any case, com- when recycled aggregates are used, and espe- pressive strength may be increased by using a cially when the @xture includes fine recycled ,~gher cement content and/or replacing some aggregates. of the recycled aggregate ~ith conventional aggregate. ~ Mixing water and zuor!ability.Because of the rela- tively high absorption of recycled aggregates as Density and air content, New concrete will have + compared to conventional aggregates, more a lower density because of the large amount of rhixing water and a higher starting slump may old mortar and cement paste adhering to recy- be necessary This is particularly true for aggre- cled aggregates. The density of new concrete gates that are dry before batching, Experience may be from 5y0 to 15y0lower than that of con- shows that recycled aggregates continue to trol concretes made with-conventional aggre- - absorb water after mixing in a ,batch plant. This gates. The natural (entrapped) air content of can cause a 1?ss of slurnp and workability after recycled-aggregate concrete may be a little fixing is completed. To offset this, recycled higher than that of corresponding’concretes aggregates—like structural lightweight aggre- made with conventional aggregates. An air- gates+an be pre-wetted in stockpiles with a entraining admixture is generally used in the sprinkling system. ,mix design if freeze-thaw @rability is required.

Water-cement ratio. At the initial design &tage, it Fine-coake aggregate ratio. For economy and . . . may be assumed that the water-cement ratio cohesion of fresh concrete, a number of for required compressive strength will be the researchers have found that the optimum same for recycled concrete as it would be for ratio of fine to coarse aggregate is,about the conventional concrete, provided the recycled samf for recycled-aggregate concrete’ as for conventional concrete. Still other researchers Coefficient of variation, The coefficient of varia- have concluded that crushed concrete fines tion for compressive strength of recycled- , should not be used in producing new concrete aggregate concrete was not much different because of problems in accurately determining from that of conventional concrete w,hen recy-, their water absorption, free water content, and cled aggregate of uniform quality-usually saturated surface dry density. While some from the same source—was used throughout concrete specifiers agree, others have found it production. This was confirmed by several I beneficial to use 10% to 30% recycled-fines as different laboratory investigations. However, “a weight percentage of the total fine aggregate higher coefficients, of variation can be expect- in the mixture (Table 1). This is not to imply ed if ready mix suppliers produce recycled- that 100% recycled fines cafiot be used suc- aggregate concrete with aggregates from a ‘ c~ssftilly in concrete. Highway pavements uti- variety of ~ources—building rubble, pave- lizing 100% recycled fine and coars~ aggregate ments, curbs and gutters, etc. Large standard have performed well in Texas.’, deviations and high coefficients of variation ~. should be avoided because they make it more Other characteristics. There are other’ character- diffjcult and more expensive to meet the sta- istics of fresh recycled-aggregate concrete too tistical compliance criteria in today’s concrete numerous to discuss in this brief publication, codes and specifications. Namely, the higher such as: batchin~ mixing, and transporting; ~ the standard deviation, the higher the required placirg compacting finishing, and curing; and average compressive strength of concrete use,d plalitic shrinkage cracking. For infor&ation on to select mixture proportions—and the higher ~. these, see References 2,6,7, and 9. the required cement content.

Characteristics of Hardened -Tensilemyiflexund strength. Con~rete’s tensile Recycled-Aggregate’Concrete and flextiral strengths are important when desi&ing structures and pavements. M. C. b Before reviewing the influences that recy~ Won, a researcher at the Texas DOT, found that cled aggregates may have on the characteris- for the same water-cement ratid, replacing vir- tics of hardenedtconcrete, it would be appro- gin fines (natural sand) with crushed con&ete priate to mention as a general principle that fines did not Changetensilh strength. When up to 30’%of the conventional aggregate in using re~cled coarse aggregate, the flexural concrete may be replaced by recycl~d aggre- strengthmqy be slightly lower than a similar gate without significantly affecting the mixture using conventional aggregates, On ihe mechanical properties of the new concrete. other hand, using crushed concrete fines may This, may be the simplest, most economical, ‘reduce fle~ural strengti by 10% to 20%. and least controversial way of getting wider use of recycled aggregates in new concrete. Shear, bond, and fatigue ,strength. One researcher “. found that when new. concrete was made with Strength. Not only compressive strength, but recycled aggregates from aged concrete ,pave- also tensile, shear, fatigue, bond, and variabili- ments, fatigue characteristics of the new concrete . . ty of strength are important mechanical’ ~rop- were the same as for concrete made with virgin erties of any hardened concrete, including ‘aggregates, Another researcher discov&ed that recycled-aggregate concrete. the bond strength between reinforcing steel mid recycled-aggregate concrete was the same as that Compressive strength. The compressive strength of conventional concrete under both static ,md of recycled-aggregate concrete can be equal to fatigue loading when recycled coarse ag~egate or higher than that of the original concrete if and natural sand were used. Shear strength the recycled-aggregate concrete is made with appears to follow a s!imilw,pattern. Good flexural the same or a lower water-cement ratio than fatigue strength in recycled-aggregate concrete the original concrete. More commonly, com- can be attributed to a superior bond between pressive strength of recycled-aggregate con- cement mortar and paste in new concrete and crete will be .5yoto 10% lower than that of a recycled-aggregate particles, corresponding concrete made with conventional aggregates. Some minor strength loss Modulus of elastici~. M.C. Won found that will likely occur when crushed cbncrete fines the use of both coarse and fine recycled’ aggre- are substituted for natural sand, b,ecause sand gates significantly reduced the modulus of : particles have greater strength (Table 2), elasticity of new concrete. Values from lsyo to . 40~o lower can be explained by the “mortar / effect.” Mortar has a lower modulus than vir- Other characteristics. There are other character- gin coarse aggregate, and since recycled-aggre- istics of hardened recycled-aggregate concrete gate concrete has a higher volumetric propor- too numerous to discuss in this.brief publication of mortar than conventional concrete, a tion,‘such as admixtures in old concrete (chlo- ’ loweimodulus of elasticity should be expected. ‘rides, for example), plastic shrinkage cracking, . / ‘id abrasion resistance, and thermal coefficient of Durability. Durability is the capacity of con- expansion. Readers may consult References2,6, crete to resist weathering action, chemical 7, and 9 for information on these. * attack, abrasion, and other conditions of service. Some of the factors important to the durability of recycled-aggregate concrete are Recycling Demolished permeability, carbonation, freeze-thaw resis- Masonry tance, and sulfate resistance. In North America the recycling of demol- Permeability and carbonation. Permeability and ished concrete has advanced far beyond that of carbonation appear to be somewhat higher for demolished masonry. Concrete rubble from high- recycled-aggregate concrete when compared ways, streets,bridges, parking lots, walks, drives, to conventional concrete at the same water- curbs, gutters, and other civil engineering works cement ratio. This may increAse the risk of cor- contains few materials other than steel and con- rosion of reinforcing steel in recycled-aggre- crete. On the other hand, building demolition gate concrete, but any risk can be offset by rubble contains many building material-on- using a lower water-cement ,ratio, adequate ventional, structural lightweight, and cellular curing, and an admixture-such as fly ash, concretes;brick; concrete masonry units (block); ground slag, or &\ica fume. natural stone; portland cement mortar, plaster, stucco, and terrazzo; gypsum, plaster; ceramic Freeze-thaw durability (frost resistance). Recycle& . mate?ials;roofing tiles and shingles; glass; aggregate concrete is resistant to freeze-thaw wood; paper; plastic; asphalt; and metals. Some . cycles. In fact, research has shown anincrease of these materials are contaminants in concrete. in freeze-thaw resistance of recycled-aggregate So the recjrcling of building rubble presents a ,- concrete compared with concrete made with much greater challenge, but it can and is being some conventional aggregates. Surprisingly, done all over the world. there is even evidence that repeated recycling of recycled-aggregate concrete further Crushed Masonry Aggregate improves frbst resistance. Most of the present knowledge of recy- ’ Sulfate resistance. The resistance of recycled- cling masonry rubble dates back to post- aggregate concrete to sulfates (found in sea water) is about the same or slightly inferior to that of conventional concrete. Sulfate resistance generally improves with proper proppr- tioning and the use of fly ash, ground slag, or silica fume.

Drying shrinkage and creep. The drying shrinkage and creep of recycled-aggregateconcrete is higher by 40% to 80% than that of a corresponding conventional concrete.This is due to the large amount of old mortar and cement paste attached to recycled aggregates.Reinforced concrete ele- ments constructed’of recycled-aggregateconcrete appear to be no more prone to shrinkage cracking than conventional concrete becausehigh shrinkage and creep tend to cancel each other jut. Comparatively lower values of drying Crushing train in action. With this cost-effective proprietary system, known as -shrinkage are reported for new concretesusing Paradigm, concrete pavement can be removed, crushed, and deposited back recycled coarseaggregate and natural sand; com- on the subgrade for use as new base material-all in one operation. The need paratively higher values exist when both fine for costly trucking and a recycling center is eliminated. and coarseaggregate are recycled. , ,

World War II experiences in Germany and the A Bright Future . UK, and more recent recycling in the ~ Netherlands. The term “masonry rubble” is Market researchers using 1998 statistics \ collective for a variety of mineral building and phone surveys found over 1000 concrete . materials resulting from the demolition of recycling plants in operation in the United btiildings and structures. Masonry rubble may States producing more than 100 million tons of . include conventional concrete and concrete concrete aggregates per year.’4This survey, con- blo~k, clay brick, sand-lime brick, lightweight sidered conservative, and other state-of-the-art concrete and block of various types, and nat- reports point to a bright future for recycling of ural stone. Also, depending upon the geo- demolished concrete and masonry. graphical Iocation”of the demolition site, one ‘ might find portland cement mortar and plaster (stucco), and burnt clay products, such as roohng tile, in masonry rubble. There is no question that crushed masonry rubble is a useful material; in Germany ‘ crushed brick aggregate is used in lightweight ~ concrete for moderate weather exposures. However, there could be a risk of undesirable expansion if the crushed brick contains signifi- 4 cant sulfate, which could come from the brick itself of from contamination by gypsum plas- “ ter. Results of a study by the U.S. Army Engineer Waterways Experitient Station noted that “Inorganic, nonmetallic residues from \ demolition of buildings maybe recycled for use as concrete aggregate if the sulfate content is controlled to prevent deleterious expansion “ due to sulfate reaction~’ I Recycled Masonry Is Coming ‘

The National Concrete Masomy association (NCMA) and others are looking into ways of recycling concrete masonry prod- ., ( ucts.” Rashwan and AbouRizk evaluated the technical, economical, and environmental viability of recyclitig concrete block and brick into grout for filling the cores in block walls,]’ Berg and Neal investigated the viability of miinici- pal solid waste bottom ash (MSWEA) as aggregate for concrete masonry units (CMU). Practical CMU mixtures were developed using a blend of MS~A, sand, and fly ash; test results proved the units could meet ASTM C 90 load bearing requirements.’3 \ For more information on recycling of demolished masonry, see Part Two of ‘ Reference 2. The authors of this section, Drs. R. R. Schulz and Ch. F. Hendricks, drew heavi- ly ‘from experience and documentation from the post-war years in Germany and the , Netherlands. While Schulz and Hendricks clearlY noted that other parameters apply today the earlier work remains interestin~ and @ some instances is still applicable with ‘ regard to recycling~emolished masonry as aggregate in new concrete. ,,,

t, Refereiices““ ,. . . ,. ‘ I 1: lZe@J@ Portland Cement Concrete, DP-47-85, Demonstratio~ProjectProgram, F@deral ‘ Highway A%stration, Washington,D:C., 1935. .- ,,. !“ ,.. 2. T.’C.HariserLllecyclhtg”o~ibolished Qwcn?temdMaso@-RILEM Report 6, Ii &l?N-Spon, , . bdon, 1992: .“ .. 8 . / 3,”Build@gCofttra@orsSocietyof}apan,pmpo$ed S@idUrdjbrLLw~fRecycle;.Aggrega&and (English-ver~ion”puMishedin J~e 1981). ~‘ ‘ ,, ‘ “ RecijcledAggreg@e bncrek 1977 ,. ., * ~.JamesWarne~’’NS+RecyclihgPiltion Paper,”Reuse and Recycling-ofConcrete,ConExpo93, ‘ $eninarhandout K-1arid L-l), Milwaukee, March 24,1993. ,, ..— ‘5. WilliamTurley %%at Does It C@to Retycl#Cori@e~e&Asphrdti”C&D.DebrisRecycling, \ Chkigo, April 1994, page42tl-23. “: ““ , . . - , - . . .- ,. ,, $:W*ti A. Yr@sov “[email protected] Cenient ,Con*te Pavements;!’NC* Synthe5is0~ Hi@.@iyPrucfiee15%National Cooperative Hi@way Resgar~ PTogtam,T\insptirtation , , Re3e@i Board,-NationalR%@ Gtu%il, WBShi@tOn,D:C., December 1989,. “ ,.., 7. “Recyc@j ConcretePavernentX%crete Pg&g Tednzobgyj.T3-014P;Arner@mConcrete ,,, , , Favemt@A%@iation, SkokiejIlliriois,1993...... 8. Da~d %irk, The’& of&~cied-dntieA~gatez@rn [email protected]~i~ngAlkali-$ili& - Reactivity,Reswth and “Developmentfkdleti-~114, Portland [email protected],Skolde, ...> -, ,– Mirlois,1996, , ,. .’ . 9. M. C. WOn;UseOfCtushe@Coru&t&r@&egate~&izi@n&t Cm&te, ResearchS@tion, ., \ Ccms~ction Di@sion,TexasDe@hnentof Trarkpor&ion, Austk”%ex&s,1999. . ‘‘ ‘ / . . 10.Aiti~. Buekj“RecycledCone@@~Source of ~@~a*/.ACll@’m@~:bticm Concrete Instibte;13e&oi~l’day 1977,pages 212-219. ,.. ..,. .. ~. ,.. 11:Erast Bori$soff,WhitePap& @@ifigCoiicrefe M&on@%&c&Green, Natiofi+,Condrete ~ ., Masonry Association,fierkd@Vi@ntaj W93,” L- -.. ,. ,, -. 12.M. Sha@ Rashwan %dSin@@li@@R@c, “Teili@cal;_Economi@and E@@mnept~, Vi@ilityOfMaqGrout’Mad&~g@@e~~ asoq~.Pr~~~$ of th&”$swe~tli@i@dia .Mas6@ ~posituk;.~chfaikr I@k@it$ Ha@JZ6q_@@io,:J.~e -I!!5; pages961:971. 1’ .. 13.‘tic R’Beq#cl JokAiNe~j-~C~~@t#-fi~@~{_@ Rq@@@ ~~apal S+d-, \ Wasfe30t@m AsN~CIMat@@J@.~;:heticti_@_ti@te @tiii@l%@h, July-Augu’st l@%,pages470i7?. “-:_ “‘: -‘. .. ‘.. .:: ~~ , : “ ‘. ., , -., . ______1 14.@k A.J@igg@_”EM@ketll@@@ I@t@d Q@@ @s@iat@i SkQl@,Jll@ois,to - . W+a6t~@l@,-@i6~C~D Deb@@@cLn$Chbg6; l@-~’@v-~ @r@umieatiQn),May 19,1998: -t : .,

, , ,

,’.

\ .

@ f999 by the Environmental Council of Concrete Organizations (

The Environmental Cotmcil of Concrete Organizations is a coalition dedicated to promoting the environmental benefits of concrete and its role in safe and sustainable construction. ,, ECCO member~ are companies, organizations, and individuals affiliated with the concrete industry. Together, they are committed to devdoping and disseminating information on the environmental benefits of concrete and concrete products. EV 22