DEVELOPMENT OF CERAMIC USES FOR

NEPHELINE SYENITE TAILINGS

DISSERTATION

Presented In Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University

By

Robert Charles Wilson, B. A., M.Sc.

The Ohio State University 1958

Approved by

Adviser Department of Ceramic Engineering PREFACE

The author wishes to express gratitude to his adviser,

Dr. J. 0. Everhart, for his help and advice. He also wishes

to thank Dr. C. J. Koenig for his suggestions and guidance

throughout his graduate career.

The author is indebted to the American Nepheline

Limited, sponsors of the research program of which this investigation is a part.

ii TO MY FATHER AND MOTHER AND

MOST ESPECIALLY MY WIFE

Hi TABLE OF CONTENTS

Pago

INTRODUCTION 1

USE OF NEPHELINE SYENITE TAILINGS lu VlTnlFIED CLa Y p i p e b o d i e s

Introduction 4 Raviow of Literature 6 Procedure 8 Results 9 Discussion 26 Conclusions 28

USE OF NEPHELINE SYENITE TAILINGS IN VITRIFIED CLAY PIPE GLAZES

Introduction 29 Review of Literature 32 Fusibility Tests 34 Cone 3 to 4 Glazes 39 Cone 04 to 03 Glazes 52 Conclusions 58

APPENDIX 64

REFERENCES 66

AUTOEIOGRAPHY 68

iv LIST OF TABLES

Number Title Page

1 Chemical Analyses of Body Materials 10

2 Screen Analyses of the Various Grinds of Nepheline Syenite Tailings 11

3 Body Compositicus and Physical Properties for Body A 12

4 Body Compositions and Physical Properties for Body B 15

5 Body Compositions and Physical Properties for Body C 17

6 Body Compositions and Physical Properties for Body D 13

7 Body Compositions and Physical Properties for Body E 2 Q

8 Body Compositions and Physical Properties for Body F 22

9 Body Compositions and Physical Properties for Body G 23

10 Body Compositions and Physical Properties for Body H 25

11 Chemical Analyses of Glaze Materials 3 5

12 Compositions Evaluated for Fusibility by the Inclined Plane Flux Block Test Method 37

13 Molecular Formulae of Cone 4 Glazes 42

14 Batch Formulae of Cone 4 Glazes 43 15 The Effect of Glazes Studied on the Flexural Strength of a Cone 4 Vitrified Clay Pipe Body 44

16 Molecular Formulae of Cone 04 Glazes 53

v LIST OF TABLES (Continued)

Number Title Page

17 Batch Formulae of Cone 04 Glazes 54

18 The Effect of Glazes Studied on the Flexural Strength of a Cone 04 Vitrified Clay Pipe Body 55

vi LIST OF ILLUSTRATIONS

Figure Subject Page

I Thermal expansion curves for body A. Body AC, no additive; body A 6 , 6 per cent addition of coarse-ground nepheline syenite tailings. 59

II Triaxial diagram for the pellet fusion study of B-200 nepheline syenite - talc - Gerstley Borate. 60

III Per cent Flexural Strength changes imparted by cone 4 glazes for firings 1 through V. 61

IV Per cent Flexural Strength changes Imparted by cone 4 glazes for firings VI through X. 62

V Per cent Flexural Strength changes Imparted by cone 04 glazes. 63

vll INTRODUCTION

Nepheline syenite is an igneous rock, resembling granite in texture, hardness, and general appearancef1 )•

The chief* mineral constituents of the rock are albite

{ soda feldspar ), mocrocline ( potash feldspar ), and nepheline. The mineral nepheline is higher in alkali and alumina, and lower in silica than either albite or microcline.

The mineral nepheline, instead of albite, crystal­ lizes from the magma as a result of an insufficient amount of silica to form albite. The fact that it is " hungry " for silica, so to speak, enhances Its vitrifying activity in ceramic bodies.

The fluxing action of nepheline syenite is unique because of the presence of the mineral nepheline.

Nepheline, mineralogically, is a sodium aluminum silicate which contains, in the natural mineral, an appreciable amount of potash. An artifically prepared nepheline Is a pure sodium aluminum silicate with the formula f^O'A^O^*

2SIQ2 * The natural nepheline containing potash has the formula K2 0 »3 Na2 0 *4Al2 0 3 *9 SI0 2 . Natural nepheline has a hardness in the Moh's scale of 5.5 to 6 , specific gravity

2.55 to 2.65 and indices of refraction of 1.538 and 1.542.

Research and subsequent commercial utilization

1 2 have shown not only that nepheline syenite can be used as a substitute for potash feldspar but that It is superior to feldspar in many respects{2 ).

Extensive deposits of nepheline syenite occur In

Canada, Russia, and India. In the United States, deposits of nepheline syenite are located in Arkansas, Montana,

New Hampshire, New Jersey, and Virginia. Some excellent deposits are located at Blue Mountain, Ontario, and in the vicinity of Bancroft, Ontario, Canada. The Bancroft deposits are higher in nepheline content than the former.

The Blue Mountain deposit is a long ridge rising to an elevation of about 350 feet above the surrounding country.

The rock of the Blue Mountain central alkaline Intrusive is fine grained, light colored, and of granite-like texture.

The solidified mass consists predominantly of the minerals albite, nepheline, and microcline in order of abundance(3).

These minerals account for approximately 95 per cent of the rock.

Although this deposit Is somewhat variable mineral- ogically, the chemical composition is uniform. When the iron, mostly in the form of magnetite, is removed during processing, a remarkably uniform product is obtained(4,5).

Geological surveys have disclosed many million tons of nepheline syenite in the Blue Mountain deposit(6 ).

Diamond drilling in the area where mining is now being carried out Indicates a block of about ten million tons.

In refining nepheline syenite, it has been found

Impracticable to remove the iron from a certain percentage of the rock. Approximately 75 per cent of the ore fed to the processing mill at Nephton, Ontario, is recovered as a low iron content material. This material has found appli­ cation in many branches of ceramics; namely, as a vitrifying agent in whltewares and as a source of alumina in glasses, glazes, and porcelain enamels. The remaining 25 per cent of the ore has about the same chemical composition as the lower Iron content product but contains higher amounts of iron oxides. The high iron content ore is efficiently separated from the lower iron content ore by high intensity magnetic separators.

Recently there has been an increased interest by vitrified clay pipe manufacturers in using additives to improve the finished physical and working properties of their pipe bodies, and in developing ceramic glazes to replace salt glazes for their ware. Developments of the use of the higher iron content nepheline syenite ore

( nepheline syenite tailings ) in the aforementioned applications have been the aim of this study. USE OP NEPHELINE SYENITE TAILINGS

IN VITRIFIED CLAY PIPE BODIES

Introduction

The manufacturers of vitrified clay pipe have shown an increased interest in adding low cost additives to their fire clay and shale bodies. Some of the principal improvements sought when experimenting with additives in pipe production are lower absorption to inhibit percolation, higher initial pipe strength and less deterioration in strengths during yard storage, longer firing ranges, and reduced air checking due in part to free silica. The additive investigated here was ground nepheline syenite tailings•

In the processing of nepheline syenite, the high iron- bearing product is separated from the low iron-bearing product by high intensity magnetic separators. For efficient high-intensity separation, it is necessary to remove the dust from the head feed to the magnetic separators.

Until recent years, the dust varied somewhat in fineness and in iron content. Processing the dust through Sweco screens and Eriez-type magnetic separators now yields a minus 1 0 0 -mesh product with five tenths per cent iron oxide. This product, however, is still not as fine as desired in a body flux. Previous work with nepheline 4 5

syenite as an additive to structural clay bodies has been

with this type of material.

This study dealt with the minus 30-mesh tailings from

the high-intensity separators. These tailings were ground

to various degrees of fineness and contained from 2 to 3

per cent of iron oxide.

From the standpoint of costs, there are two stipu­

lations which must be met oy materials added to the clays

and shales used in making vitrified clay pipe: the activity

of the material must be great so that small additions will

suffice; and the cost of the material must be low. The

ground tailings are a low-cost commodity that can be

shipped at a low freight rate because of the relatively high iron content. Information was therefore desired to

establish the effect of several percentages of iron oxide and fineness of grind on the fluxing characteristics of

nepheline syenite in pipe bodies. Careful consideration was given to the selection of representative pipe bodies. Review of Literature

Nepheline syenite has found application in all

branches of ceramics. In whitewares, advantage is taken of

the low fusion characteristics of nepheline syenite to

lower firing temperatures of the various products. This

permits savings in fuel, in refractories, and In kiln

furniture, and provides a wider color palette for single

fire production.

In 1939, Chilcote and Koenig{7) Investigated the

influence of small additions of the previously described

dust by-product, and combinations of this by-product with

dolomite, on the physical properties of fire clay and shale

brick. It was found that the addition of small amounts

lowered the absorption and increased the fired shrinkage

and flexural strength.

Realizing that some vitrified clay pipe bodies fall

to develop a sufficiently low absorption even when fired to

the maximum safe temperature, Everhart(8 ) investigated the

effect of 17 fluxing materials on such bodies. By using

the dust nepheline syenite by-product, he found that with

two to five per cent additions, acceptable absorptions and

strengths were obtained at definitely lower temperatures without accompanying reductions in the upper firing limit.

This indicated a considerable lengthening of the maturing range. At the same firing temperature, sizable reductions in absorptions and Increases in flexural strengths were obtained.

Many other flux materials besides nepheline syenite have been investigated as additives to structural clay bodies. In one of the most recent articles concerned with additives t: structural clay coHos, Knlzek{9) describes the use of volcanic materials In building brick. He found that certain unfavorable characteristics of an alluvial surface clay (e.g., drying cracks, low density, and low mechanical strength ) could be corrected by adding varying amounts of volcanic scoria and pumice. Procedure

Prior to mixing, the fire clay or fire clay - shale mixtures were reduced in size to minus 14-mesh. In preparing a body, the materials were dry-mixed in a

Simpson laboratory mixer; water was then added and the materials were wet-mixed. The body was then extruded using a Fate-Root-Heath laboratory pug mill under a vacuum of

26 inches* Test bars seven inches in length and three quarters of an inch in diameter were used for all physical tests except thermal expansion for which the test specimens were eight inches in length and one-half inch in diameter*

The test specimens for the different bodies were placed with alternate arrangement in sand on silicon carbide slabs. They were fired in a down-draft gas-fired periodic kiln on a 20- to 24- hour heating schedule with a one hour soak at the required temperature; the kiln then was allowed to cool by its own radiation to room temperature.

The shrinkage values were calculated on the wet length basis. The absorption(lO), modulus of rupture(11), and thermal expanslon(1 2 ) values were obtained according to standard procedures.

8 Results

This study presents the results for five typical vitrified clay pipe bodies. The chemical compositions of the various bodies and of nepheline syenite tailings are given in Table 1. The screen analyses of the various grinds of nepheline syenite tailings are given In Table 2.

Body A

Body A was a mixture of 50 per cent Clarion shale and 50 per cent of a blend of Tionesta, Bedford, and

Brookville fire clays. Such a body is normally fired at cone 4. Body compositions and physical properties are given in Table 3.

The dry shrinkage of Body A was not appreciably affected by the addition of the coarse-ground tailings.

Generally, the firing shrinkage varied inversely as the absorption. The firing shrinkages Increased with successive additions of the ground tailings over the range from cone 01 to cone 6 . Absorptions for the bodies fluxed with coarse- ground tailings were lower than for the control body for each firing. Approximately the same absorption was attained in the body fluxed with 6 per cent coarse-ground tailings at nearly a four-cone lower firing than the control body.

The body fluxed with 3 per cent nepheline syenite

9 TABLE 1

Chemical Analyses or Body Materials

Nepheline Bodies Chemical Syenite Tailings A, C, G B DE F, H

S102 57.0 56.4 72.0 50.3 61.4 58.4

A1j>03 23.5 23.0 17.5 28.0 2 2 . 2 17.6

Pe2 0 3 2.7 5.0 1.3 5.2 2.5 5.2

Ti0 2 - - 1.4 1.2 1.4 1.5 1.4

CaO 1.2 0.5 0 . 1 0.4 0.4 2.3

MgO 0.9 0,5 0.5 1.2 0.5 2. 1

KgO 4.7 2.5 0.5 2.3 1.7 2.7

Na20 8.9 0.4 1.0 Trace 0 . 2 0.9

so3 - - 0. 2 0. 1 Trace Trace Trace

Hg0 at 1Q5°C Trace 2.4 0.4 1.1 2.2 1.9

Loss on Ignition 1. 2 7.7 5.4 10.7 7.7 7.5

100.1 100.0 100.0 100.6 100.3 100.0

o 11

TABLE 2

Screen Analyses of the Various Grinds of Nepheline Syenite Tailings

Percent Cumulative

Screen No. Test Grinds Commercial Grinds

Coarse Pine Grade B-200 Grade 1000

On 65 0 . 1 2 - - 0.03

100 0.36 0.09 0 . 1 0

150 0.91 0.19 0.32

2 0 0 1.79 0.30 0.74

270 4.05 0.53 1.69

325 8.50 1.35 4.69 Trace through 325 91.50 98.65 95.31 99.99 12

TABIm, 3

Body Compositions and Physical Properties for Body A

Body

AC A3 A 6

Body Compositions (% dry basis)

Clarion Shale 50.0 48.5 47.0 Tionesta, Bedford, and Brookville Fire Clays 50.0 48.5 47.0 Coarse-ground nepheline syenite tailings 0 . 0 3.0 6.0

LOO.O 1 0 0 . 0 1 0 0 . 0

Physical Properties

Shrinkage (% wet basis) Dry 4.8 4.4 4.8 Firing cone 01 5.7 5.8 6.1 25 5.8 6.1 6.5 45 6.2 6. 2 6.6 66 6.6 6.8 6.8

Absorption {%) cone 015 4.7 3.6 2 . 6 25 3.4 2 . 6 1.3 45 2 . 0 0 . 6 0.1 0.5 Nil Nil

Modulus of Rupture (psi) cone 0 1 ^ 4400 5400 5620 25 6000 6100 7200 6300 7400 7800 4 1 6 ° 7500 6700 7000 13 tailings had the same absorption as the control body at a two-cone lower firing. On the basis of absorption data, the fluxed bodies had longer maturing ranges than the control body* Flexural strengths of the bodies fluxed with the ground tailings were appreciably higher than those of the control body over the range from cone 01 to cone 4.

Although the absorption values continued to decrease at the cone 6 firing, the bodies containing nepheline syenite had passed their optimum flexural strengths*

Thermal expansion data for Body A fired to four different cones are given in Figure 1* The effect of the

6 per cent addition of ground tailings on the thermal expansion characteristics was more in evidence at the lower than at the higher firings. At cone 01 the control body had a significantly lower thermal expansion and a greater digression in the vicinity of the alpha-beta quartz inversion than the body with the 6 per cent addition.

The reduction in the amount of free quartz in the body with the 6 per cent addition was due to the absence of free quartz in the nepheline syenite, and to the solution by the nepheline syenite of the quartz introduced by the shale and fire clays* Nepheline, being incompatible with quartz, is more active in dissolving quartz than are the feldspar minerals, albite, and microcline* 14

The maximum thermal expansion for both the control bod; and the body containing 6 per cent ground tailings occurred at cone 2. The Increased thermal expansion provided by the ground tailings favors attainment of compression ceramic glazes. Compression glazes are desired to prevent crazed ware and to improve the flexural strength of the ware.

Body 3

Body B was composed entirely of Lower Kittanning No. 5 fire clay. This body is normally fired at cone 4. Body compositions and physical properties are given in Table 4.

In general, dry shrinkage tended to decrease, and firing shrinkage tended to increase with increasing additions of the coarse-*ground tailings. Absorptions were lower for the bodies containing the coarse-ground tailings than for the control body. On the basis of this data, a 6 per cent addition of the ground tailings permitted about a three- cone lower firing. Flexural strengths were noticeably greater for the bodies containing the tailings than for the control body over the firing range studied.

Body C

Body C and Body A { 50 per cent Clarion shale and 50 per cent of a blend of Tionesta, Bedford, and Brookville fire clays ) were from the same source but were obtained at different times. Body conqposltions and physical properties 15

TABLE 4

Body Compositions and Physical Properties for Body B

Body

BC B3 B6

Body Compositions {% dry basis)

Lower Kittanning No. 5 Fire Clay 1 0 0 . 0 97.0 94.0 Coarse-ground nepheline syenite tailings 0 . 0 3.0 6.0

1 0 0 . 0 1 0 0 . 0 1 0 0 . 0

Physical Properties

Shrinkage (> wet basis) Dry 4.8 4.5 4.4 Firing cone 2° 2 . 2 2.7 3.3 45 2.9 3.5 3.3 65 5.4 5.4 3.5

Absorption (%) cone 2 & 6.8 6.3 5.0 45 6.0 5.9 3.7 6 s 3.4 2.9 2.3

Modulus of Rupture (psi) cone 2 5 3200 3300 3800 45 3800 4100 4300 65 4600 4900 5200 16 are given in Table 5. The previous results showed that a

6 per cent addition provided significantly better results than a 3 per cent addition. Bearing in mind the importance of minimizing costs, a 5 per cent addition of the fine- ground tailings was selected for study ( see Table 2 ).

The addition of the fine-ground tailings decreased the dry shrinkage and increased the firing shrinkage of

Body C. The 5 per cent addition provided enough fluxing action to appreciaoly lower the absorptions over the firing range studied. The modulus of rupture value for the body containing 5 per cent fine-ground tailings was 20 to 30 per cent higher than the control body.

It Is interesting to note that the body with the 5 per cent addition evidenced about the same flexural strength at cone 02 as did the control body at cone 6 and that the absorption of the body with this addition at cone 02 was the same as that of the control body at cone 3-4.

Body D

Body D was composed of 40 per cent Huckleberry fire clay and 60 per cent of the shale occurring directly above it in the geological horizon. This body is normally fired at cone 3. Body compositions and physical properties are given in Table 6 .

The addition of 5 per cent of the fine-ground tailings did not appreciably affect the firing shrinkage, but the 17

TABLE 5

Body Compositions and Physical Properties for Body C

Body

CC C5

Body Compositions {ji dry basis)

Clarion Shale 50.0 47.5 Tionesta, Bedford, and Brookville Fire Clays 50.0 47.5 Fine-ground nepheline syenite tailings 0 . 0 5,0

1 0 0 . 0 1 0 0 . 0

Physical Properties

Shrinkage (% wet basis) Dry 5.9 4.3 Firing cone 02 4.4 5.0 4.9 5.5 6 5 5.9 5.6

Absorption {%) c cone 02 5.7 3.7 2? 4.9 2.4 65 1.4 0.4

Modulus of Rupture (psi) cone 0 2 ^ 3800 5000 2 *> 4900 6000 6 5200 6300 18

TABLE 6

Body Compositions and Physical Proparties for Body D

Body

DC D5

Body Compositions (%) dry basis)

Huckleberry Pire Clay 40.0 38.0 Shale 60.0 57.0 Pine-ground nepheline syenite tailings 0 . 0 5.0

1 0 0 . 0 1 0 0 . 0

Physical Properties

Shrinkage (% wet basis) Dry ~ 4.5 5.1 Firing cone 01° 5.6 5.6 5.8 5.8 2i45 5.9 6 . 0 6 & 5.8 5.4

Absorption (%) cone 0 1 b 2 . 2 0 . 6 2c 0.9 0.4 0.4 Nil 65 0.4 0 . 2

Modulus of Rupture (psi) cone 0 1 b 5700 6200 2 5 6700 7100 45 7400 7800 65 5700 5700 19 absorption was lower. On the basis of absorption and

strength, the maturing range was materially lengthened by

the addition. The flexural strength os Body D at the several firings were improved by the addition. Both the

control body and the body containing fine-ground tailings evidenced overfiring at cone 6 , as indicated by loss in strength.

Equivalent absorption was obtained three cones lower.

Body E

Lower Kittanning No. 5 fire clay was used in this body, and the normal firing is cone 6 . body compositions and physical properties are given in Table 7.

There was a slight lowering of the dry shrinkage when 5 per cent of fine-ground nepheline syenite tailings was added to 3ody E. The firing shrinkage increased slightly when ground tailings was added to the body.

Absorptions were lowered by the ground tailings and indicated a two-cone lower maturing temperature. The body fluxed with

5 per cent nepheline syenite tailings evidenced a substantial

increase in modulus of rupture over the control body.

Body F

This body consisted of two parts of a weathered

Queenston shale ( Canadian geological identification ) and one part of Lower Kit canning No. 5 fire clay, as indicated 20

TABLE 7

Body Compositions and Physical Properties for Body E

Body

EC E5

Body Compositions (% dry basis)

Lower Kittanning No. 5 Fire Clay 1 0 0 . 0 95.0 Fine-ground nepheline syenite tailings 0 . 0 5.0

1 0 0 . 0 1 0 0 . 0

Physical Properties

Shrinkage (;£ wet basis) Dry 6.5 6.4 Firing cone 4*? 2.9 3.3 6 3.1 3.4 8 & 3.6 3.9

Absorption {%) cone 4° 6.7 5.2 6 5 5.7 4.3 8 5 3.3 1 . 1

Modulus of Rupture (psi) cone 4° 5000 5800 5300 6t 6000 8 5 6000 6600 in Table 8 . The body is fired at cone 04, which is

considerably lower than the temperatures used for the

previously described pipe bodies. This body has a com­

paratively short firing range. Since it was doubtful whether significant fluxing action would be derived from

the fine-ground tailings at a temperature this low, a body was included which contained 2 per cent of the very finely ground grade 1 0 0 0 nepheline syenite supplementing 5 per cent of the fine-ground tailings. At cone 04, no improve­ ment was derived from these additions. At cone 02, fired strengths were increased, particularly in the case of the body which contained the very finely ground nepheline syenite. Absorptions were also slightly lowered at this firing by the additions.

Body G

Body G and Body C were obtained from the same source.

In this case, the influence of 5 per cent of grade B-200 nepheline syenite ( commercial grade nepheline syenite tailings ) was studied ( Table 9 )•

In general, the addition of B-200 nepheline syenite decreased the dry shrinkage and increased the firing shrinkage of the body. Over the firing range studied, the absorptions were lowered by the fluxing action of the B-200 nepheline syenite. The modulus of rupture values for the body containing 5 per cent B-200 nepheline syenite were 20 22

TABLE 8

Body Compositions and Physical Proparties for Body F

Body

PC F5 P10 P52

Body Compositions {% dry basis)

Quaenston Shale (weathered) 6 6 . 0 63.5 60.0 62.0 Lower Kittanning No. 5 Pire Clay 34.0 31.5 30.0 33.0 Pine-ground nepheline syenite tailings 0 . 0 5.0 1 0 . 0 5.0 Commercial grade 1000 nepheline syenite 0 . 0 0 . 0 0 . 0 2 . 0

1 0 0 . 0 1 0 0 . 0 1 0 0 . 0 1 0 0 . 0

Physical Properties

Shrinkage wet basis) Dry 4.7 4.7 4.7 4.9 Firing cone 04° 4.2 4.1 3.9 4.2 0 2 6 4.5 4.8 4.9 5.0 0 1 6 5.0 5.3 5.3 5.3

Absorption (%) cone 04s 5.8 6 .0 6.4 5.9 0 2 6 4.0 3.7 3.9 3.4 0 1 6 3.6 3.4 3.3 2.9

Modulus of Rupture (psi) cone 04^ 3800 3900 3700 3800 0 2 ® 4000 4500 4400 4700 0 1 ® 4200 4200 4500 4000 TABLE 9

Body Compositions and Physical Properties for Body G

Body

GO G5

Body Compositions (% dry basis)

Clarion Shale 50,0 47.5 Tionesta, Bedford, and Brookville Fire Clays 50.0 47.5 Commercial grad© B-200 nepheline syenite 0 . 0 5.0

1 0 0 . 0 1 0 0 . 0

Physical Properties

Shrinkage wet basis) Dry 6 5.4 4.3 Firing cone 1 5.1 5.4 43 5.6 5.8 6^ 6.1 5.9

Absorption (%) cone lb 4.4 2.3 4 3 2 . 0 0 . 6 62 0 . 8 Nil

Modulus of Rupture (psi) cone 1 ® 4400 5400 4 3 5100 6200 6 2 5300 6600 24

to 30 per cent higher than for the control body when fired at the same temperature.

Body H

Body H was from the same source as Body F* In the case of Body H, the influence of B-200 nepheline syenite was studied ( Table 10 ). As was the case in Body P with fine- ground tailings, the addition of 5 per cent grade B-200 nepheline syenite did not appreciably improve the physical properties of this body at its normal firing temperature of cone 04. 25

TABLE 10

Body Compositions and Physical Properties for Body H

Body

HC H5

Body Compositions (%> dry basis)

Queenston Shale (weathered) 6 6 . 0 63.5 Lower Kittanning No. 5 Fire Clay 34.0 31.5 Commercial grade B-200 nepheline syenite 0 . 0 5.0

1 0 0 . 0 1 0 0 . 0

Physical Properties

Shrinkage (% wet basis) Cry 4.7 4.7 Firing Cone 042 3.9 3.9 0 2 6 4.2 4.6

Absorption (%) cone 042 5.6 6.2 0 2 6 4.4 3.9

Modulus of Rupture (psl) cone 04^ 3750 3700 0 2 6 4150 4400 Discussion

When bodies were fired below cone 02, additions of nepheline syenite tailings influenced chiefly the unfired physical properties of the body, such as dry shrinkage and extrusion characteristics. Laminations In extruding some bodies were avoided by the non-plastic syenite additions.

Thus the addition of the ground tailings in the role of a grog that does not entail thermal expansion irregularities in quartz inversion range is worthy of consideration.

At firings above cone 02, the fluxing action of ground tailings was clearly apparent. Lower absorptions or possible reductions in firing temperatures, improved flexural strengths, and longer firing ranges were obtained by 5 per cent additions. In the case of red-firing shales or clays, only a slight darkening of the color was Imparted by the additions. In the case of light-firing fire clays, darker colors resulted. Heretofore a coarser-grained nepheline syenite product { 1 0 0 -mesh ), not as fine and having a lower iron content than the ground tailings studied here, has found limited industrial applications in floor-paver and quarry tile bodies. The ground tailings provide more fluxing action than the coarse product because of the greater fineness and increased iron oxide content.

26 27

Commercial production of vitrified clay pipe using a body containing 5 per cent of the ground tailings ( grade

B-200 nepheline syenite ), and firing to cone 3, has con­ firmed the laboratory results regarding lower absorption and increased flexural strength derived from the addition.

A large reduction also was noted in the number of cracked pipe when the body containing the additive was used instead of the normal body. The reduction in the number of cracked pipe may possibly be related to several factors: a slightly lower dry shrinkage and resultant drying strains because of the non-plastic addition, a reduction in the amount of free quartz present in the body owing to the absence of free quartz in grade E-200 nepheline syenite, and a reduction in the amount of free quartz in the body introduced from the shale or fire clay as a result of solution of the quartz by the additive during firing. Conclusions

When firing at cone 02 and above, the additions of ground nepheline syenite tailings to fire clay and shale bodies provide lower absorptions, improved flexural strengths, and longer maturing ranges.

Thermal expansions of a fire clay and shale body are significantly increased by additions of ground tailings; the effect is greater at the lower than at the higher firing temperature. The ground tailings also helps to reduce the free-quartz content in the bodies.

When firing below cone 02, the additions of ground nepheline syenite tailings to fire clays and shales effects the unfired properties, by acting in the role of a refractory grog.

28 USE OP NEPHELINE SYENITE TAILINGS

IN VITRIFIED CLAY PIPE GLAZES

Introduction

Glazes applied to vitrified clay pipe bodies are of two kinds, "salt" and "ceramic.11 The use of salt glaze is predominant throughout the industry. The method of pro­ ducing the salt glaze consists, briefly, in placing the ware in the kiln and vaporizing common salt on the kiln fired during the latter part of the firing process* The salt glaze cannot be applied successfully to all clays, because they must be able to withstand a firing temperature sufficiently high to produce the reaction between the salt vapor and silica of the clay. Practice indicates that this firing temperature should be at least cone 1 , a temperature at which some clays become overfired, as indicated by bloating and by deforming under load of the kiln setting.

A "ceramic glaze" is composed of suitable ceramic materials In the proper proportions to form the "batch" or

"glaze mix," which is usually ground wet to form a free- flowing glaze slip* The slip is usually applied to the freshly formed ware or to the dry ware by spraying or dipping. The ware is fired in the kiln to the temperature at which both body and glaze mature* Ceramic glazes may be applied to those clays capable of taking a salt glaze and

29 30

to many clays which do not salt glaze readily.

The ceramic glaze has certain advantages over a salt

glaze, and there is a growing tendency among vitrified

clay pipe manufacturers to replace the salt glaze with a

ceramic glaze. Some of the most prominent advantages of a

ceramic glaze follow: (1) A ceramic glaze can be developed

that will be under compression on the body, whereas a salt

glaze is generally ir tension. Glazes under compression

improve strength and also prevent crazing. (g) A properly

designed ceramic glaze provides a more durable ware surface

than that produced by salt glazing. The typical salt glaze

is known to deteriorate in usage. (3) With tunnel kilns

becoming more widely used in the vitrified clay pipe

industry, producers prefer not to use salt glazes in these kilns. Salt vapors are deterlmental to kiln refractories and, in addition to the cost entailed, production quotas

suffer when tunnel kilns are shut down to replace refracto­

ries. The salt fumes are frequently obnoxious and corrosion

of exposed metal is a problem.

One disadvantage of ceramic glazes is higher cost.

Another drawback would occur in the event that a given

ceramic glaze developed appreciable amounts of glass at too low a temperature, thus inhibiting the removal of carbona­

ceous material from the body. It is important to develop a ceramic glaze that will provide all of the advantages and 31 still be relatively lov in cost* Since a white or color­ less glaze is not required, the cost of the glaze materials can be substantially reduced by use of materials not generally suitable for whiteware glazes, such as high iron fluxes and clays*

This study was concerned with the development of a satisfactory vitrified clay pipe glaze using low-cost nepheline syenite tailings ( commercial grade B-200 ) as its cheif fluxing constituent. The same clay that is used in the manufacture of the pipe was also used as a glaze ingredi­ ent. By using these two low-cost materials as a substantial part of the glaze, the glaze cost is materially reduced. Review of Literature

Although many reports are available on ceramic glazes used in various ceramic industries, there are relatively few reports concerned with ceramic glazes on vitrified clay pipe bodies. In 1951, PIotnikov(13) reported a glaze mix with the following percentage composition: 67.5 clay, 9 calcined manganese dioxide, 13.5 chalk, and 10 silicate rock, ground to 5 per cent on 270-mesh, maturing at cone 1.

He also stated that the glaze slip could be stored for a long time without harmful effects. Zaitseva(14), In 1952, prepared a glaze frit with the per cent composition of 45 to

47 silica, 9 to 11 alumina, 12 to 17 ferric oxide, 7 to 9 calcium oxide, 1 to 2 magnesium oxide, 0.5 to 1 sulfur trioxide, and 16 to 18 sodium oxide. Casein was added to this frit to improve adhesion. The glaze matured at cone 03 and had a dull brown color. This glaze should be fired in a reducing atmosphere. The latest literature on ceramic glazes for vitrified clay pipe bodies was presented by

Knizek(15). He used volcanic scoria and a pumice to develop low-cost glazes for pipe. These materials melted satis­ factorily at cone 6 but developed mat textures. Crystalli­ zation of plagloclase feldspar in the pumice, and magnetite and orthorhomblc pyroxenes in the scoria were found to be causes of mat textures. Suitable additions of feldspar,

32 33

alluvial clay, or both, corrected the tendency of the

materials to devitrify. Small amounts of litharge or borax

controlled the fusibility of the glazes. Many satisfactory

compositions were developed. The best of these increased

the modulus of rupture of a standard vitrified clay pipe

body by more than 40 per cent. These glazes maturing at

cone 6 would appear to be unsuitable for the average North

American pipe manufacturer, since the majority fire in the

range of cone 04 to cone 4.

Several references relating to nepheline syenite, talc,

colemanite, and diatomaceous earth were helpful in this

study. Lynch and Allen(16) found that a low-melting mixture

occurs in the nepheline syenite — talc system. The defor­

mation temperature of a mixture of 85 per cent nepheline

syenite — 15 per cent talc was the lowest in the system; namely, cone 3. french(17) and later Merritt(18) developed

various high alkali glazes ( maturing at cone 04 to cone 02 ), using colemanite as a flux. Stull and Johnson(19) developed a number of raw glazes for structural clay products based on the use of shales and surface clays. The fusibility of

the glazes was controlled by additions of whiting, galena, colemanite, or lead silicate frit. Balsham(20) also was successful in using colemanite as a glaze material.

Russell and Rowland(21) found superior glaze fit for glazes that contained diatomaceous earth as a source of silica in place of conventional Potter's flint. Fusibility Testa of Various Materials with

Nepheline Syenite Tailings

Frior to mixing actual glazes to be applied on body specimens it was felt that simple fusion tests of various mixtures with nepheline syenite would be helpful in indicating the probability of attaining maturity in glaze development. The chemical compositions of all the raw materials in this study are given in Table 11.

In the first phase of the fusion tests, pressed pellets one-half inch in diameter by one-quarter inch in height were prepared from compositions which had been dry mixed for one-half hour in ball mills. The selected compositions of the B-200 nepheline syenite -- talc --

Gerstley Borate triaxial are shown in Figure II. In selecting the compositions to be tested, knowledge of the nepheline syenite — talc eutectic was utilized. One pellet of each composition was fired in a globar electric kiln to cone 03, cone 01, and cone 6 , respectively. In each firing, mixtures 4, 8 , and 12 ( 30% Gerstley Borate ) were completely puddled, whereas mixture 9 ( zero per cent

Gerstley Borate ) was the most refractory mixture. Twenty per cent additions of Gerstley Borate to the nepheline syenite — talc combinations provided low temperature glasses in this range.

34 35

Table 11

Chemical Analyses of Glaze Materials

Nepheline Gerstley Frits Pipe Bodies Chemical Syenite lilC Dor«u6 Kaolin Grade B-200 (1 ) (2 ) cone 04 cone 4

sio8 58.2 56.6 9.5 34.9 33.6 58.4 56.4 45.5

tio2 ------1.4 1.4 0.1

a1 2°3 23.6 1.1 1.1 - - 1.6 17.6 23.0 37.5

----- b 2°3 33.0 21.9

- - Cr2 03 - - - - M tm ------

Pe2°3 1.6 0.3 0.3 - - * 5.2 5.0 0.9

BaO ------

CaO 0.9 7.0 15.9 - - - - 2.3 0.5 Trace

IrlgO 0.7 30.4 3.5 - - - - 2.1 0.5 Trace

PbO 4^ * - - - - 43.1 64.9 ------

ZnO ------

Na20 9.4 - - 4.9 - - - - 0.9 0.4 0.4

KgO 4.7 2.7 2.5 1.3 Loss on Ignition 1.0 4.6 31.8 - - 9.4 10.1 13.7

100.1 100.0 100.0 99.9 100.1 100.0 99.8 99.4 Silica ■ Kaolin BaC03 CaCOj Cr203 Fe2°3 ZnO Diatomaceous Potter1s -325M Flour

45.5 89.4 99.9 99.9 99.3

------0.1 ------

37.5 4.1 - - -- 0.6 ------• - ** • ------

«■ ------— — - - 99.9 - - -

99.9 m am 1.5 - - - - 0.2 0.9 ------

------77.6 - -

- - - - 0.2 Trace - - 56.0 - -

w — Trace 0.7 — ~

* m v m

99.9 - -

0.4 m m 0.8 1.3

- - 13.7 23,4 44.0 ------3.3 - - - -

99.9 99.9 99.9 100.0 99.9 99.4 100.0 100.0 99.9 100.1 36

In the next phase of this preliminary fusion study, the inclined plane flux block test(2 2 ) was used in lieu of the pellet tests, with the intent of obtaining infor­ mation regarding the viscosity of the mixes at these temperatures. At this stage, an arbitrarily selected addition of 20 per cent of a comnercial fire clay - shale pipo body was included. A 3 per cent addition of red ferric oxide was included to act both as a flux and as a colorant to approximate the color of a typical salt glaze.

The mixtures were blunged with water for three hours, screened through a 65-mesh sieve, and dried at 220°F for at least four hours. The mixes were then ground to minus

65-mesh in a mortar and pestle. Ten gram portions were used in the flux blocks. Firings were conducted in a globar electric kiln on a four-hour heating schedule to cone 04. Compositions are given in Table 12.

The Initial mixture (P-l), evaluated by the incline plane flux block test method, was based on the triaxial study of nepheline syenite, talc, and Gerstley Borate, and modified with the clay and red ferric oxide additions as described above.

Other trials in this series were as follows:

Zinc Oxide Modifications (P-l, P-2, and P-3).—

The glass flow increased with increasing additions of zinc oxide. There was an abrupt increase in the fluidity of the TABLE 12

Compositions Evaluated for Fusibility by the Inclined Plane Flux Block Test Method

Mix Material PI P2 P3 P4 P5 P 6 P7 P8 P9 P10

Nepheline Syenite Grade B-200 48.5 47.5 47.0 42.5 38.0 34.0 42.5 38.0 42.5 47.0

Talc 8.5 8.5 8 . 0 7.5 7.0 6.0 7.5 7.0 7.5 8 . 0

Gerstley Borate 2 0 . 0 2 0 . 0 2 0 . 0 2 0.0 2 0 . 0 2 0 . 0 2 0 . 0 2 0 . 0 15.0 1 0 . 0

3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 Pe2°3 3.0

ZnO - - 1.0 2 .0 2. 0 2 .0 2 . 0 2 . 0 2 .0 2. 0 2.0

Diatomaceous earth 5.0 1 0 . 0 15.0 - - - - 1 0 . 0 1 0 . 0

Potters Silica 5.0 1 0 . 0 - - - -

Cone 4 Pipe Body 2 0 . 0 2 0 . 0 2 0 . 0 2 0 . 0 2 0 . 0 2 0 . 0 2 0 . 0 2 0 . 0 2 0 . 0 2 0 . 0

100*0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 38

glass when a 2 per cent addition was used over that provided by the 1 per cent addition. The possibility remains

that an amount of zinc oxide in excess of 2 per cent would

be helpful in achieving greater fluidity.

Diatomaceous Barth Modifications (P-3, P-4, P-5, and

P-6 ).-- The fluidity of the glass gradually decreased with

increasing replacement oJ the nepheline syenite — talc portion of the mix with diatomaceous earth. For the higher

temperature range, additions of diatomaceous earth appear desirable.

Potter1 s Flint Modifications (P-4, P-5, P-7, and P-Q).

Equivalent amounts of Potter*s flint increase the viscosity of a glass more than does diatomaceous earth. Undoubtedly, differences in particle size and composition ( Table 11 ) are contributing factors to this occurrence. Diatomaceous earth has approximately 2 per cent on 325-mesh, whereas

200-mesh Potter's flint has a residue of approximately 9 per cent on 325-mesh.

Gerstley Borate Modifications (P-5, P-9, and P-10).

The glass viscosity decreased with increasing additions of

Gerstley Borate at the expense of the nepheline syenite — talc eutectic portion of the mix. There was a pronounced increase in fluidity of the glass with 20 per cent Gerstley

Borate over the glass with only 15 per cent Gerstley Borate. Glazes Maturing In the Cone 3 to 4 Range

Procedure

In developing a vitrified clay pipe glaze based In the ground tailings, many combinations of materials could be evaluated. In order not to limit appreciably the scope, detailed systematic studies of combinations of materials were not conducted. After evaluating the results from each firing, careful consideration was given to the next logical direction to pursue, bearing in mind the importance of attaining a satisfactory low cost glaze In a reasonable time period.

A commercial pipe body which consists of 50 per cent

Clarion shale and 50 per cent of a mixture of Bedford,

TIonesta, and Brookville fire clays was selected for this study. Extruded bars seven inches in length by three- quarters of an inch in diameter were used as test specimen.

In the case of the more promising glazes, 4-Inch diameter pipe was obtained from the plant and cut to test specimens five inches long.

Having costs in mind, the early mixing of the glazes was accomplished by blunging rather than by wet ball milling.

One thousand gram batches of each glaze were prepared by blunging for four hours and screening through a 65-mesh sieve.

On the following day, the glazes were adjusted to specific

39 40 gravities ( 1.2 - 1.3 ) suitable for application of the glaze by spraying techniques. To facilitate uniform appli­ cation of the glaze, the test specimens were set in an upright position on a mechanically rotated ( 78 rpm )

■»* potter*s wheel. Each specimen was glazed for fifteen seconds. This provided a fired glaze thickness of approxi­ mately three mils.

Some of the glazes, as later Indicated in the tables and script, were ball milled for eight hours.

The glazed specimens were dried at room temperature and held overnight at 22Q°F in a drier. Refractory blocks appropriately holed to support the glazed bars in a vertical position were used in setting the kiln. Firings were carried out in a down-draft gas-fired periodic kiln, on a

20- to 24-hour heating up schedule with a one-hour soak at the required temperature, after which the kiln was allowed to cool to room temperature.

The glazes were visually examined for appearance, crazing, etc. The influence of the glaze in increasing or decreasing the strength of the bar specimens compared with that of unglazed bars was used as an indication of the compression or tension of the given glaze. Flexural strength values represent an average of ten tests(1 0 ).

The chemical compositions of the raw materials used are given in Table 11. The molecular and batch formulae of the glazes are given in Tables 13 and 14, respectively. 41

Reaulta

Eight aeries of glazes were investigated. The test

data are given in Table 15 and in Figures III and IV.

Discussion of results is presented in terms of a given firing, as earlier discussed and since In some cases a glaze was repeated lor direct comparative purposes or for further confirmation of results.

Firing I_ ( Cone 42 ).-- The series A glazes were based on findings from the flux block tests. The first glaze of this series contained no diatomaceous earth, and the remaining glazes contained this finely divided silica in increasing Increments of b per cent. This was done es­ sentially at the expense of the nepheline syenite — talc eutectic portion of the glaze, but also by lowering the shale - fire clay content in 1 per cent stages. These glazes all appeared to be matured and had a brown color.

No initial crazing was apparent where the glaze was of proper thickness, but it was noted where the glaze was heavy. All glazes of this first series ( A-l thru A-5 ) substantially lowered the flexural strength of the body.

The strengths appeared to decrease with an increase in the alumina — silica ratio. The best glaze of this series was quite poor from the glaze compression standpoint. It lowered the flexural strength of the body 24 per cent so that the results were only a little better than a typical salt glaze. 42

TABLE 13

Molecular Formulae of Cone 4 Glazes

Series A Series B

1 2 3 4 5 1 2 3

BaO ------

CaO .248 .255 .261 .268 .277 .277 .278 .2 SC

KNaO .380 .370 .360 .354 .345 .341 .339 .332 MgO .291 .291 .292 .287 .286 .287 .285 .296 PbO ------_ _ - - m m ZnO .081 .084 .087 .092 .096 .096 .098 .096 ai2 03 .520 .500 .495 .484 .476 .475 .420 • 36' .305 .320 B2°3 .333 .347 .365 .375 .366 .37]

- - - - CrS°S - - w a .099 e'e2 ° i .102 .107 .110 .113 .102 .110 aor S102 2.43 2.62 2.83 3.04 3.30 3.36 3.34 3.26 2o3 :Sio2 1/4.6 1/5.2 1/5.7 1/6.3 1/6.9 1/7.1 1/8 . 0 1/8.1 Series C Series D Series £ Series

1 2 3 1 2 3 1 2 F-l 1, 1A, &

... _

------.103 .202 - -

.203 .203 .205 .254 .303 .303 .310 .301 .280 .400

.281 .245 .247 .196 .148 .146 .150 .146 .346 .250

.204 .205 .160 .250 .253 .249 .233 .248 .278 .250

.200 .250 .300 .196 .200 .202 .103 m - - - -

.100 .100 .088 .101 .100 .101 .103 .102 .098 .100

.378 .374 .375 .267 .268 .253 .248 .250 .460 .300

.323 .400 .485 .321 .325 .330 .337 .327 ,372 .343

.108 .104 .106 .107 .110 .108 .110 .102 .105 .155

3.40 3.37 3.41 2.45 2.44 2.53 2,54 2.52 3.50 3.65

1/9.0 1/9.0 1/9.1 1/9.2 1/9.1 1/10 1/10.2 1/10 1/7.6 1/12 . E Series G Series H Series M ' ~ - 2 F-l 1, 1A, & IB 2 3 i 2 1 2 3 4

.202 - - - - .150 .150 ------.550 .680

.301 .280 .400 .250 .250 .400 .400 .430 .440 .150 .022

.146 .346 .250 .250 .250 .250 .250 ,400 .405 .244 .272

• 248 .278 .250 .250 .250 .250 .250 .170 .155 .056 .024 m m

.102 .098 .100 .100 .100 .100 .100 .337 .354 .246 .313 .250 .460 .300 .303 .330 .303 .305 .350 .345 .670 .700 .220 - - .327 .372 .343 .346 - .

_ . — « — ■* • .033 .069

.110 .110 .030 .155 .140 .014 ,102 .105 .155 .110 .107 3.60 3.62 3.86 4.30 2.18 3.13 ,52 3.50 3.65 3 .50 3.67 1/9 1 / 1 0 l o 1/7.6 1 / 1 2 1/11.6 1/11.1 1/12 1/ 1 2 1/11.5 1/12 43

T A B L E 14

Batch Formulae of Cone 4 Glazea

Series A Sex

1 2 3 4 5 1

Nephellne Syenite Grade B-200 47.0 43.5 40.0 36.6 33.2 32.6 32

Talc 8 . 0 7.5 7.0 6.4 5.8 5.8 e

Geratley Borate 2 0 . 0 2 0 . 0 2 0 . 0 2 0 . 0 2 0 . 0 19.9 2C

Frit No* 1 -

Cone 4 Pipe Body 2 0 . 0 19.0 18.0 17.0 16.0 15.2 9

K a o l i n -

BaCC>3 -

C a C O ^ -

Cl*2°3 - 3.0 f'e2°3 3.0 3.0 3.0 3.0 3.2 3

ZnO 2 . 0 2 . 0 2 . 0 2 . 0 2 . 0 2 . 0 2

Dlatomaceoua Silica - - 5.0 1 0 . 0 15.0 2 0 . 0 21.4 25

-325M Silica -

Silica Flour -

1 0 0 . 0 1 0 0 . 0 1 0 0 . 0 1 0 0 . 0 1 0 0 . 0 1 0 0 . 1 1 0 0 leries B Series C Series D Series £ Ser

o 2 3 1 2 3 1 •j 3 1 2 F-l 1 1A IB

33.8 35.3 36.9 29.6 28.5 30.1 22.3 22.3 18.2 13.7 33.2 23.5 23.5 23.5

6.0 6.3 5.6 5.5 3.8 9.1 9.2 9.2 7.4 6.9 5,8 5.4 5.4 5.4

2 0 . 6 2 1 . 6 10.7 20.9 20.0 19.0 19.0 19.0

- - - - 26.8 32.2 37.2 32.6 32.1 32.1 16.0

9.1 1.7 16.0 9.3 9.3 9.3

- - - - 1.1 4.4 4.3 2.1 6.5 6.5 8 . 0 1 0.6

6.1 11.9

------3.9 3.8 3.9 6.3 7.8 7.8 5.0 2.0 - - 3.8 3.8 3.8

3.3 3.5 3.6 3.5 3.4 4.6 5.0 5.0 5.0 4.6 3.0 3.8 3.8 3.8

2.1 2 . 2 2.1 2.0 1.9 2.6 2.5 2.5 2.5 2.5 2.0 2.1 2.1 2.1

25.3 29.6 20.0 18.9 16.9 12.6 14.7 - - m m ------

------*■ ------14.7 21.1 27.0 2 0 . 0 33.1 3 3 .1 -----

3 3 .1

100.2 100.2 100.0 99.9 99.9 100.0 100.1 100.1 100.0 100.1100.0 100.0100.0 100.0 rles JS Series G Series H Series M

2 F-l 1 1A IB 2 3 1 2 1 2 3 4

Z 13.7 33.2 23.5 23.5 23.5 23.1 33.0 23.2 22.9 31.6 30.0 30.0 35.5

I 6.9 5.8 5.4 5.4 5.4 5.4 7.9 5.4 5.3

7 20.9 20.0 19.0 19.0 19.0 18.7 - - 18.7 16.5 32.8 31.0 14.0 - -

) m . - 16.0 9.3 9.3 9.3 9.1 5.5 9*3 9.2

) 10.6

** ■■ L 11.9 ------7.5 8.2 - - - - 30,0 35.5

) 2.0 - - 3.8 3.8 3.8 - - 5.4 3.8 3.7

» 1.3 2.5

> 4.6 3.0 3,8 3.8 3.8 3.7 3.9 3.7 3.7 - - 4.7 6.0 - -

► 2.5 2.0 2.1 2.1 2.1 2.0 2.2 2.1 2. 0

■» a mm m ■ ------m • - - 35.6

a* «k 27.0 2 0 . 0 33,1 33.1 mm mm 30.8 33.9 - - - - 33.7 20.0 29.0

33.1 - - 0 mm 32.6 32.2

1 0 0 .1 1 0 0 . 0 1 0 0 .0100.0 1 0 0 . 0 100.3 100.0 100.1 10 0 . 0 100.0 99.4 100.0 100.0 44

TABLE 15

The Effect of Glazes Studied on the Flexural

Strength of a Cone 4 Vitrified Clay Pipe Body

Firing GJa ze Modulus of Rupture Percent Strength Number Number psi Change#

I A-l 3300 -34 A - 2 3600 -29 A - 3 3700 -26 A-4 37 50 -26 A - 5 33 50 -24 Bisque 5100

II 3-1 39 50 -27 5-2 4000 -26 5-3 4500 -17 M-l crawled M-2 3350 -38 Bisque 5400

III C-l 4050 -23 C-2 4500 -14 C-3 4750 - S Bisque 5250

IV D-l 4250 -18 D-2 4500 -13 D-3 6100 ♦ 17 Bisque 5200

V D-3 6450 ♦24 E-l 5300 ♦ 2 E-2 3600 -31 M-3 3370 -35 M-4 3450 -34 Bisque 5200

VI D-3 6800 ♦31 Bisque 5200

VII A-5 4400 -18 F-l 5800 ♦ 7 G-l 6600 ♦ 2 2 Bisque 5400 45

TABLE 15 (continued)

Firing Glaze Modulus of Rupture Percent Strength Number Number psi Change*

VIII G-l 6650 124 G-2 4800 -10 G-3 4150 -22 3isque 5350

IX G-l 6150 f 21 Bisque 5100

X G-l 5800 ♦ 16 G-1A 6300 *26 G-1B 5610 ♦ 12 II-1 5260 ♦ 5 K-2 5570 rll Bisque 5000

* The percent strength change is determined as the difference between glost and bisque divided by the bisque. A positive figure denotes gain in strength and vice versa for a negative figure. 46

Firing II ( Cone 4^ ). Since maturity was not a

problem in the series A glazes, and. the glaze with the highest silica content was the best in regard to com­ pression, the series B glazes were compounded to evaluate

the influence of decreasing the alumina and increasing the

silica. These provided alumina— silica ratios of 1:7.1,

1:3.0, and 1:9.9. Increasing the silica to these higher

levels by use of diatomaceous earth progressively increased

the difficulty of bulkiness of the glaze slips. These three glazes matured and had appearances similar to the A series

glazes, but the best ( B-3 ) still lowered the flexural

strength of the body 17 per cent.

Glaze M-l was a formulation given in the literature,

except that diatomaceous earth was used instead of Potter*s flint. This glaze crawled severely on this body. When

Potter's flint ( iM-2 ) and an addition of 4.7 per cent red

ferric oxide were used, the crawling was minimized.

However, the glaze reduced the strength of the bars by 38 per cent.

Firing III ( Cone 4^- ).— In view of the apparent difficulty In obtaining a satisfactory low-cost raw glaze,

series C utilized a lead-boro-silicate frit, and kaolin was

substituted for the pipe body. For this firing, the flexural strengths of all the glazes ( C-l to C-3 ) evi­ denced a decrease from the control. The least decrease in flexural strength was noted with glaze C-3, which contained 47 the highest amount of frit.

Firing 17 ( Cone 42 ).— This firing included glazes based on glaze C-3. Two variaoles were studied. The alkali content was reduced and on the basis of previous experience, the superfine diatomaceous earth was directly replaced by minus 325-mesh flint. The reduction of the alkali content did not improve tho flexural strength of the body. A marked improvement from a decrease of 15 per cent to an increase of 17 per cent in flexural strength was noted when minus 325-mesh flint was substituted on a weight basis for diatomaceous earth.

Firing V ( Cone 4 ^ ).— Although glaze D-3 improved the flexural strength and had good gloss and texture, the cost of a fritted glaze would be unfavorable to its wide utilization. This firing Included glaze D-3, series K glazes, and two glazes based on eutectic mixes. Series E glazes substituted barium carbonate and Gerstley Borate for the lead frit. Glaze D-3 again evidenced a substantial improvement in flexural strength ( 24 per cent increase ).

However, although glaze E-l provided a 2 per cent increase in strength, the other glazes of this series proved detri­ mental to the body.

Firing VI ( Cone 4^ )— Firing VI was a large-scale test firing of glaze D-3. Again the flexural strength showed marked Improvement ( 31 per cent increase ). 48

Firing VII ( Cone 4 ^).— Having obtained a fritted

glaze which evidenced good compression on the cone 4 fire clay - shale body, efforts were again directed to obtaining a satisfactory glaze having a lower batch cost than glaze

D-3.

It will be recalled that the glazes in series A and B matured at cone 3-4 but were under tension on this body.

Also, the use of large percentages of the finely divided diatomaceous earth may result in too low specific gravity of the slip. Glaze F-l was prepared by the direct sub­ stitution of minus 325-mesh flint for the diatomaceous earth in glaze A-5. This substitution increased the silica content, primarily at the expense of the alumina content, but partially because the minus 325-mesh flint does not have an ignition loss, whereas diatomaceous earth has a 3.3 per cent loss. Glaze F-l provided a strength increase of

7 per cent, whereas glaze A-5, in this firing, lowered the strength 18 per cent. Indications are that a slight increase in the silica content of glaze F-l would provide a good compression glaze.

Glaze G-l was based on a low melting mixture of B-200 nepheline syenite - talc - Gerstley Borate. It Is higher In calcium oxide and silica, and lower in alkalies and alumina than glaze F-l. This glaze provided a strength increase of

22 per cent in this firing. 49

Firing VIII { Cone 4^ ).— Glaze G-l was repeated and again provided a substantial strength increase. Glaze G-2 was the same as G-l except that 0.15 equivalents of barium oxide replaces a like amount of calcium oxide in the G-l formula. This glaze caused a loss in strength of the body.

Glaze G-3 was like G-2 except that the boric oxide was deleted. This glaze crawled and also lowered the strength of the body.

Firing IX ( Cone 45 ).-- This firing was a large scale test of glaze G-l, which was applied both on oars and on sections of 4-inch diameter pipe. The bars glazed with G-l showed an improvement in strength of 21 per cent above that of the unglazed bars. The texture and color of the bars were good. The glaze applied to the insides of the 4-inch pipe possessed about the same color as the bars. However, the glaze on the outside of the pipe evidenced a variable green- brown color, which may be due to the influence of soluble salts on the outside of the pipe. While the surfaces were probably amply smooth for this application, the larger surface areas of the pipe compared with the test bars made it evident that improvements in smoothness of glaze surface would be desirable.

The 4-inch pipe sections were autoclaved in accordance with ASTM Procedure C-126-55T. After completion of this test, they were subjected to 175 psi autoclaving, which was 50

25 psl higher than the ASTM procedure.

Glaze G-l passed this rather severe test without signs

of crazing and suffered only slight loss in gloss, whereas

a typical salt glazed specimen lost practically all of its

glaze.

Firing X ( Cone 4^ ).— Modifications of glaze G-l, which were Intended to correct the difficulty of variable color on the outside of the pipe and also to improve the

surface smoothness of the glaze, were evaluated in this firing. To avoid color variability, small additions of chromic oxide were tried. Some of the glazes were ball milled to improve smoothness.

Glaze G-1A was of the same composition as glaze G-l but was ball milled eight hours instead of blunging for four hours. In glaze G-1B, a 180-me3h si-ica flour contain­ ing 0.15 per cent of red ferric oxide was used as a replace­ ment for the minus 325-mesh flint in glaze G-1A. Glaze H-l and H-2 contained small percentages of chromic oxide to provide a more uniform color. All glazes in this firing, except glaze G-l, were prepared by ball milling for eight hours. All glazes exhibited an improvement in flexural strength over the unglazed body. Glazes H-l and H-2 showed the color and degree of maturity specified by a leading vitrified clay pipe manufacturer. The smoothest textured glaze was G-1A, which was ball milled and contained the minus 325-mesh flint#

The 4-inch pipe glazed with H-l were autoclaved in accordance with ASTM Procedure C-126-55T. No crazing or loss in gloss was in evidence. Glazes Maturing In the Cone 04 to 03 Range

Procedure

The body selected for these test glazes comprised a

mixture of two parts of Queenston shale and one part of

Lower Kittanning No. 5 fire clay. The techniques used for

body and glaze preparation were like those used for the

higher fired glazes earlier described, although as indicated

in Table 18, all of these glazes were ball milled for from

8-16 hours, in lieu of blunging. Tests were conducted

only on bar3 and not with 4-inch pipe.

The molecular formulae ana batch formulae are given

in Tables 16 and 17, respectively. Flexural strength data

are shown in Figure V.

Results

Firing 1^ ( Cone 03^ ) Glaze N-l was the same as G-l

in the previous series except that the red ferric oxide was

increased from 0.10 to 0.16 equivalents. It was prepared

by wet ball milling for sixteen hours instead of mixing by

blunging. This glaze applied on bars had a smooth surface

texture and good brown color. Bars with this glaze were 10 per cent stronger than the unglazed body, indicating fairly

good compression. If variable color develops in using this

glaze on pipe, it seems logical to try introducing about 1

52 TABLE 16

Molecular Formulas of Cone 04 Glazes

Glaze

N1 N2 N3 N4 N5 N6 N7 N8

CaO .40 .40 .40 .40 .20 .30 .30 .35

KNaO .25 .25 .25 .25 .25 .25 .25 .25

MgO .25 .25 .25 .25 .25 .25 .25 .25

PbO ------.20 .10 .10 .05

ZnO .10 .10 .10 .10 .10 .10 .10 .10

.28 .27 .24 .32 .31 .26 .26 Al2°3 .26

.33 .36 .43 .35 - - - - .32 .32

.16 .16 .16 .16 .15 .15 .15 115 PeS°3

S102 3.55 3.58 3.53 2.59 3.50 3.50 3.35 3.35

AlgOj * SlOg 1/ 1 2 . 6 1/13 1/13 1/ 1 0 . 6 1/11 1/11 1/ 1 2 . 6 1/ 1 2 . 6

O) TABLE 17

Batch Formulae of Cone 04 Glazes

Glaze

N1 N2 N3 In 4 N5 N 6 N7 N8

Nepheline Syenite, Grade B-200 23.4 '21.6 20.5 29.0 32.2 33.2 22. S 23.2

Talc 5.4 4.9 4.7 6.7 7.7 7.2 5.2 5.3

Gerstley Borate 18.8 2 1 . 0 23.3 23.4 - - - - 18.4 18.7

Frit No. 2 ------18.4 9.5 3.6 4.4

CaCOj 3.8 2.7 2.2 4.7 3.9 6.8 1.2 2.5

5.7 5.6 5.7 Fe2°3 5.8 5.6 7.2 5.9 6.1 ZnO 2.1 2.0 2.0 2.6 2.2 2 .2 2 . 0 2.1

-325M Silica 32.6 32.2 31.9 23.6 25.5 29.4 28.0 29.8

Cone 04 Pipe Body 9.4 9.5 9.9 2 . 6 4.2 4.8 8 . 2 8.5

101.5 99.8 100.1 100.0 100.0 99 .9 1 0 0 . 1 1 0 0 . 2 cn *>• TABLE 18

The Effect of Glazes Studied on the Flexural Strength of a Cone 04 Vitrified Clay Pipe Body

Firing Bisque n Physical Data yj laze Number Control

I Cone 03^ HI N2 N3 N4 Modulus of Rupture, psl 5400 5900 5750 4760 5560 % strength change* — 10 6 -12 3 Time of ball-milling, hr. — 16 16 16 16

II Cone 031 N5 N6 N7 N8 Modulus of Rupture, psi 5410 6440 6400 6450 6500 % strength change* — 20 19 20 21 Time of ball-milling, hr. -- 16 16 16 16

III Cone 03^ N i - e Nl-12 Nl-16 Modulus of Rupture, psi 5380 5500 5700 6530 % strength change* -- 2 5 22 Time of ball-milling, hr. — 8 12 16

The per cent strength change is determined as the difference between glost and bisque divided by the bisque. A positive figure denotes gain in strength and vice versa for a negative figure.

tn Cn 56 per cent of chromic oxide, which was found to reduce color variability in the cone 5 - 4 glazes.

Glazes N-l through N-3 show the effect of increasing the boric oxide equivalents from 0.33 (N-l) to 0.38 (N-2) to 0.43 (N-3). It will be noted that increasing the boric oxide content beyond that contained in glaze G-l increases the thermal expansion of this type glaze as indicated by the strength of the glazed bars.

Glaze N-4 is Doth lowor in alumina and silica than N-l and has a lower silica to alumina ratio. Bars with glaze

N-4 evidenced a slight Increase in strength over the unglazed bars.

Firing II ( Cone 031).— Glazes N-5 through N-8 encompassed the use of a lead silicate frit. In glazes N-5 and N-6 , 0.20 and 0.10 equivalents of lead oxide, respectively, replaced like equivalents of calcium oxide In the N-l formula. No boric oxide was used in glazes N-5 and

N-6 . These glazes were matt type, but under compression as indicated by good strength increases.

Glazes N-7 and N-8 were like glaze N-l except 0.10 and

0.05 equivalents of calcium oxide were, respectively, replaced by lead oxide. These were high gloss glazes and substantially increased the strength of the body.

Firing III ( Cone 03^ ) In this firing, a large scale test was made with glaze N-l. Reduced ball milling 57 times, twelve hours in the case of Nl- 1 2 and eight hours in the case of Nl-8 , were studied. The gloss and flexural strength improved with increases in milling time. Glaze

Nl-16 milled for sixteen hours provided a 22 per cent increase in strength. Conclusions

Non-frittad and fritted compressive glazes for vitrified clay pipe application maturing in the cone 4 and cone 04 ranges were developed. The non-fritted glazes were based on a low fusion mixture of nepheline syenite - talc - Gerstley Borate modified with additions of zinc oxide, flint, local clay, red ferric oxide, and chromic oxide additions. Small percentage additions of chromic oxide were helpful in stabilizing the colors and simulating the appearance of a typical salt glaze.

Lead-boro-silicate and lead silicate frits were used in the fritted glaze formulations. For both the cone 4 and cone 04 glazes, the fritted glazes evidenced the highest increase in flexural strengths: glaze D-3 for the cone 4 glaze and glaze N-8 for the cone 04 glaze.

58 % % L inear T hermal E x r a n s io n iue I. Figure Thermal Thermal a ^ d it.iv e j body A6, f per cent a d d itio n ' f coarse-ground coarse-ground f ' n itio d d a cent per f A6, body j e it.iv d ^ a ehln syenie tailngs. s g lin i a t ite n e y s nepheline Cone Cone xaso cre fr oyA r?ody no AC, A. body for curves expansion Or C e n o C 9 4 e n o 6 B -200 Ne p h e l in e Sy e n it e

vZw

50% B-200 Ne p h e u n e Sy e n it e 50% B-200 Ne p h e l in e Sy e n it e + 50% Ta l c + 50% Ge r s t l e y Bo r a t e

Figure IT. Triaxial diagram for the oellet rusion rtuciy of ^-20C nepheline syenite — talc — /er stley aorat,e. 61

Fwnq Cone G la z e ai y//////////////// AZ 77////////////, I 4* A3 77//////////// A4 7ZZ7Z//////Z A5 IV77////////

Bl U/////////7//

B3 777777. MSC.2 V/////////////////,

Cl \//////////s III 4 1 C2 C3 7777,7

01 V///////s IV 4 * 02 V///7/ D3 V7/////A

03 7//////////A El 3 V 4 * E2 777//////////// MISC. 3 v/y////////////// MtSC.4 V///////////////,

■ ■ « * ■ ■ « -40 -30 -20 -10 0 +10 + 20 + 30

% Str e n g th Ch a n g e

Figure III. Per cent "lexural 3t,ren-th changes im p 'i’t e i :»y coffe I, -^lizes 'o rfi rin ^ e I th ro u ~ 6 V. 62

R w n o C o n e Gl a z e VI D3 Tzzzzzzzzzzzm

AS VII FI 01 7

01 Tzzzzzzzzm VIII 4 02 v z m 03

IX 4 3 01 Tzzzzzzzm

01 Tzzzzm Yzzzzzzzzm x 4 010 Tzzm HI H t 7ZZ7A

-40 -30 -20 -10 •f K) <*>20 *30

% S t r c n o t h C h a n o e y i '" r e IV . Per f'e n t F le x u ra l S tre r-'th char ;es Imparted Fy rone it rinses for firings VI thro a h X. 63

Fm n g Cone Gl a z e n i V////7 M2 77/ 1 03' N3 7777777

7~ ^ N4 ^ /

M3 7777777777/7.

NO 777777777 II 031 NT 77/777777777;

MS 7777777/77/77;

M I-8 a IN 03* NIH2 777 MI-18 7777777777777A i i i -10 0 +K> >20

% St r e n g t h Chanqe Figure V. Per cent Flexural Strenrth changes imi>arted b y cone OL glazes. APPENDIX

The Physical Properties of Grade 3-200 Nepheline Syenite

Chemical Analysis

SI02 58.2$

Al2 03 23.6

*'*2° 3 1.6 CaO 0.9

I-IgO 0.7

Na2 0 9.4

4.7 K2 ° Ignition Less 1.0

100.1

Sieve Analysis

0.03$ on 70 mesh

0 .10/6 on 10 0 mesh

0.32$ on 140 mesh

0.74.6 on 200 me 3h

1.69$ on 270 mesh

4.69$ on 325 mesh

Empirical Molecular Formula 0.644 NagO

0.212 KgO 0.978 A1P0* 4.11 SI02 0.067 CaO 0.042 FegOg 0.076 MgO 65

.Molecular Weight 426.6 pH Determination { Glass Electrode Method ).

Distilled Water ------6.40

1 - hour ( 5 solid to 60 liquid )------9.75

24 - hour ( 5 solid to 60 liquid )------9.50

Pyrometric Cone Equivalent cone 3-4 fusibility 1.4Rcm at cone Q3 fused color Murky brown at cone 8 3

Fused 200-mesh hesidue Brown at cone 5^ 66

REFERENCES

1. Koenig, C. J., Literature Abstracts of Ceramic Appli­ cations of Nepheline Syenite" Milo" State”Tinlv. Studies. Eng. Exp. Sta, SuTTl No. 16^, pp 63 (Jan. 1958).

2 . Koenig, C. J., Nepheline Syenite in Ceramic Ware, Ohio State Univ. Studies. Eng. Exp. Sta. Bull. No. 103, pp 74 (Nov. 1939).

5. Keith, M. L., Petrology of the Alkaline Intrusive at Blue mountain, Ontario, bull. Geoi. Soc. Amer. 50 (12 Part'I) 1795-1826 (1939).

4. Mather, J. J., and Maidment, H., Milling and Process Methods of American Nepheline Llmltecl, Can. Mining Met. Bull. No." 54 3 ~ 397-404 (1957 ) .

6 . Spence, H. S., Nepheline Syenite from Ontario, Am. Inst. Mining Met. Eng. Tech. Publ. No. 951, pp 9, (1938). 6. Deeth, H. R., Nepheline Syenite at Blue Mountain, Mining Eng. £ 1241-1244 (1957).

7. Chilcote, J. H., and Koenig, C. J., Use of Nepheline Syenite in Heavy Clay Products, J. Can. Ceram. Soc. 3 53-59' '(1939).

P. Everhart, J. 0., Use of Auxiliary Fluxes to Improve Structural Clay Bodies, Arm. Ceram. Soc• Bull. 36 268-271 (1957).

9. Enizek, I. 0., Use of Volcanic Materials in Manufacture of Building Brick, Ain. Ceram. Soc. Bull. 35 $63-36? ( 1 6 5 6 ) . ------—

10. American Society x'or Testing .materials Designation: C 373-55T, Am. Soc. Testing Materials, Standards. Pt. Ill, B18-320 (1955).

11. American Society for Testing Materials Designation: C 369-55T, Am. Soc. Testing Materials. Standard. Pt. Ill, 310-311 (1955).

12. American Society for Testing Materials Designation: C 372-55T, Am. Soc. Testing materials. Standard. Pt. Ill, 805-807 (1955). 67

13. Plotnikov, L. A., Low-Melting nlaze X or Sewer Pipe, SteKlo i Reran. 8_ 18-19 (1951); Ceram. AbstrT f7) 121o (1951J.

14. Zaitseva, m. I., Ceramic Sewer Pipe 1‘rom Low-melting Clay and Leadlree Glaze, Steklo i iveram. £ 12-13 (1952); Ceram.' Aostr". (10} 176d (1953).

15. Knizek, I. 0., Developnent of Sewer Pipe Glazes from Volcanic Aa to rials, An! Ceram. Soc. dull'l 35 399-40T 0.956) . 16. Lynch, S. 0., and Allen, A. A., dephellne Syenite - Talc ..lxtnres as a Flux In Low-temperature Vitrified oodles, J. An. Ceran. Soc. 33 117-120 (1950).

1 7 . French, 11. Id ., Colenanlte as a Glaze .Material, J. An. Ceram. Soc. 14 739-741 ( 1931 j .

Id. llerritt, C. >V., haw Leadloss Glazes at Low Tempera Lure, Am. Ceram. Soc, Lull. 14 1 0 4 -1 0 6 ('lbSo") .

19. Stull, R. T., and Johnson, P. V., Low Coat Glazes Tor Structural Clay Proauct3 , Aat. our. Standards fuTsTTT Circ. C 436, Aar. 6, lu4£.

20. .salshan, L., Colei.mmlte as a dlaze material, Ceram. Ind. ol 100-104 (1948).

21. Russell, Jr. R., and Rowlands, R. R., Glaze Investi­ gations: I. Lffect ol Various Silicas In Typical Glazes, J. Am. Ceram. Soc. 36 1-11 (1953).

22. Andrews, A. 1., Lnamel3 , The Garrard Press, p 331 (1949) . AUTOBIOGRAPHY

I, Robert Charles Wilson, was corn November S, 1927 in Buffalo, New York. I received my secondary education at South Park High School in Buffalo, New York. My undergraduate training was in the field of inorganic chemistry at the University of Buffalo, which granted me the Bachelor of Arts degree in 1950. p’rom The Ohio State

University, I received the master of Science degree in

1952. I was employed as a Ceramic Engineer with Lenox,

Inc., from ly52 to 1955. In 1955, I received an appoint­ ment as a Research Associate at the engineering Experiment

Station of The Ohio State University. I held this position for three years, specializing in Ceramic Engineering, while completing the requirements for the degree Doctor of

Philosophy.

68