Journal of the American Concrete Institute, Vol. 17, No. 6

P, <357^5/46

J O U R N A L

of the

AMERICAN CONCRETE INSTITUTE

(A C I PROCEEDINGS Vol. 4 2 )

V o l. 17 June 1946 No. 6

CONTENTS

Papers and Reports...5 6 5 -7 2 0

A sph altic O il-L a te x Joint-Sealing Compound. ...B R Y A N T W . P O C O C K 565 Petrography of Concrete A g g re g a te ...

...ROGER RHOADES and R. C M IE LE N Z 581 Entrained A ir in Concrete: A Symposium... 601

E ntrained A i r — A Factor in the D esign of Concrete M ix e s ...W . A . C O R D O N 6 0 5 Recent’Experiences w ith lA ir-E n tra in in g lP o rtla n d lC em e n C C o n cre te in the Northeastern States

...L. E. A N D R E W S 621 Experiences with A ir-E n tra in in g Cem ent in C e n tra l-M ix e d C onc re te ...

A L E X A N D E R FOSTER, J r . 6 2 5 Studies of Concrete C ontaining E ntrained A i r ...

...S T A N T O N W A L K E R a n d D E L M A R L . B L O E M 6 2 9 H o m o g e n e ity of A ir-E n tra in in g C o n c re te ... H E N R Y L . K E N N E D Y 641 M e th o d s of Entraining A i r in Concrete...E. W . SCRIPTURE, J r . 6 4 5 Effect of A i r Entrainm ent on Stone Sand C oncrete...A . T. G O L D B E C K 6 4 9 A M e th o d for Direct M e asurem ent of Entrained A ir in Concrete ...

... W . H . K LE IN a n d S T A N T O N W A L K E R 6 5 7 A u to m atic Dispensing E quipm ent for A ir-E n tra in in g A g e n ts ... R. R. K A U F M A N 6 6 9 M e c h a n ic a l Dispensing Devices’ for ¡A ir-E n train in g A g e n ts ...E. M . BRICKETT 6 7 3 A Simple A c cu ra te M e th o d for D e te rm ininglE ntra ined A i r in Fresh Concrete.

... S. W . B E N H A M 6 7 7 Effect of Use of Blended Cements and V in s o l R esin-Treated Cements on D u ra b ility of Concrete

... W . F. K E L L E R M A N N 681 A ir-E n tra in in g Concrete— P ennsylvania D epartm ent of H ig h w a y s W . H . H E R M A N 6 8 9 Portland -R osend ale Cement Blends G iv e H ig h Frost Resistance...B. H . W A I T 6 9 7

The Repair of Concrete: A n Introduction...RODERICK B. Y O U N G 701 Behavior of Concrete Structures Under A tom ic Bombing— E. H . PRAEGER 709 Job Problems and P ractice... 7 2 1 -7 2 4 W hat Kind of Cement Stucco ?... 721 Setting H eavy M achinery on Concrete Bases...R. R. K A U F M A N 721 Current Reviews... 7 2 5 -7 3 2 N ew s L etter... 1 -1 2

S Y M P O S IU M O N E N T R A IN E D A IR IN C O N C R E T E • Member­

ship A pp licatio ns Increase • W ho’s W ho • N a v y Seeks Former Sea- bees • H onor Roll • New Members • Joseph L . Duffy • Conde B.

M cCullough • W illiam Johnson Henderson •

to p r o v i d e a c o m r a d e s h i p in f i n d i n g th e b e s t w a y s to d o c o n c r e t e w o r k o f a l l k in d s a n d in s p r e a d i n g t h a t k n o w l e d g e

A D D R E S S i 7 4 0 0 S E C O N D B O U L E V A R D , D E T R O I T 2 , M I C H .

S1 .50 per copy

Extra copies to members S I .0 0

DISCUSSION

Discussion dosed s«. JL •«

Concrete Construction in the N ational Forests—C liffo rd A . Betts

Lap ped Bar Splices in Concrete Beams—Ralph W . Kluge and E dw ard C . Tuma Tests of Prestressed Concrete Pipes Containing A Steel Cylinder— C ulbertson W . Ross Field Use of Cement Containing V insol Resin—C harles E, W u e rp e l

N ov. J L 45 M aintenance and Repair of Concrete Bridges on the O rego n H igh w ay System

G . S. Paxson

A n Investigation of the Strength of W elded Stirrups in Reinforced Concrete Beams O reste M o re tto

Jan . J l. 46 Shrinkage Stresses in Concrete—G e ra ld Pickett

Floating Block Theory in Structural A n a ly sis—Stanley U. Benscoter

Shrinkage and Plastic Flow of Pre-Sfressed Concrete—H o w a rd R. Staley and Dean Peabody, Jr.

Proposed Minimum Standard Requirements for Precast Concrete Floor Units— A C I Committee 711

Proposed Recommended Practice for the Construction of Concrete Farm Silos— A C I Committee 714

Feb. Jl. '46 M aintenance of H eavy Concrete Structures— Minnesota Power & Ligh t Com pany Practice

Clay C. Boswell and A lb e r t C. Giesecke

Two Special Methods of Restoring and Strengthening M asonry Structures—J. W . K elly and B. D. Keatts

Laboratory Studies of Concrete Containing A ir-Entraining Adm ixtures—- Charles E. W u e rp e l

Shrinkage Stresses in Concrete— (Part 2)—G e ra ld Pickett

Discussion closes A ugust 1 5, 1 9 4 6

N ov. Jl. '45 Should Portland Cement Be D ispersed?— T. C. Powers

A p r . J l. '46 Announcement of Proposed M anual of Standard Practice for D etailing Reinforced C o n ­ crete Structures—Reported by A C I Committee 315 (Discussion p e rio d w ill p ro b a b ly be - extended)

M aintenance and Repair of Portland Cement Concrete Pavement—A . A . A n d e rson Curing Concrete with Sealing Compounds—R. F. Blanks, H . S. M eissner and L. H . T uthill Radiant H eating by Reinforced Concrete—John R. N ichols

The Expansion Test as a Measure of A lk a li-A g g re g a te Reaction—R. F. Blanks and H S M eissner

Concrete at A d v an ce Bases—I. S. Rasmusson

Discussion closes Septem ber 1, 1 9 4 6

A sp h altic O il-L a te x Joint-Sealing Compound—Bryant W . Pocock June J l. 46 Petrography of Concrete A g g re g a te —Roger Rhoades and R. C . M ie le n z

— continued on inside Back Cover

Vol. 17—No. 6 June 1946 (Proceedings Vol. 42)

J O U R N A L

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JO U R N A L

is e d ite d by the Secretary o f the Publications Committee under the d irectio n o f the Committee

ROBERT F. BLANKS

Chairm an

H A R R IS O N F. G O N N E R M A N

(e x -o ffic io )

R. D. BRADBURY R A Y M O N D E. D A V IS

HERBERT J GILKEY

A . T. G OLDBECK FRANK H . J A C K S O N

W . H . KLEIN S T A N T O N WALKER RODERICK B. Y O U N G

H A R V E Y WHIPPLE

Secretary

It is the p o lic y o f the A m e ric a n Concrete Institute to encourage p a rticip a tio n b y its members and others in the work of extending the k n o w le d g e of concrete and reinforced concrete as a basis for im proved products a n d structures.

To this end the Board of D irection has assigned to the Publications C om m ittee the responsibility of selecting for p u b lica tio n such papers, com m ittee reports, discussions and other contributions or parts of such contribu­

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tute objectives within space requirements consistent with bu d g e t lim itations.

A M E R IC A N C O N C R E T E IN STITU TE

N E W C E N TE R B U IL D IN G D E TR O IT 2 , M I C H I G A N

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Title 42-22 — a p art o f PROCEEDINGS, A M E R IC A N CONCRETE INSTITUTE V o l. 42

J O U R N A L

o f the

A M E R I C A N C O N C R E T E I N S T I T U T E

(c o p y rig h te d )

V o l. 17 N o. 6 7 4 0 0 S E C O N D B O U L E V A R D , D E TR O IT 2 , M I C H I G A N June 19 46

A s p h a ltic O il-L a te x Jo int-S ealing C o m p o u n d *

By BRYANT W . P O C O C K f S Y N O P S I S

The development of asphaltic oil-latex compounds for use in sealing expansion joints in concrete pavem ents is discussed. Laboratory tests devised by the M ichigan S tate H ighway D epartm ent for evaluating these seals are described and results of field installations in M ichigan are reported. T entative M ichigan specifications for this type of seal are given.

INTRODUCTION

The historical background of asphalt-rubber compounds for highway purposes was characterized by th e development in England and the N etherlands of various m ixtures of latex w ith bitum inous substances.

These m ixtures retained certain properties of the p aren t m aterials, notably the elasticity of the rubber and the adhesion, cohesion and ductility of the bitum en.

While these experiments were being conducted in Europe, th e design of expansion joints for concrete pavem ents was undergoing its initial de­

velopm ent in this country. American highway officials, recognizing the need for an effective sealing compound for use in excluding m oisture and foreign bodies from expansion joints, tried tars, pitches, asphalts and m any other substances. For some time, asphalt was held to be the best m aterial available for use as a joint-sealing compound.

Asphalt, however, had certain disadvantages which soon became apparent. F or one thing, expansion joint seals made of asphalt tended to flow a t higher sum m er tem peratures. Conversely, they became brittle in w inter and lost most of their ductility, cohesion and adhesion to concrete.

I t was only n atu ral th a t American highway engineers should become interested in the progress of European experim entation with rubber and

* S u b m itte d to th e I n s tit u te , J u n e 18, 1945.

tR e s e a r c h C h e m is t, M ich ig an S ta te H ig h w a y D e p a r tm e n t.

(56 5 )

asphalt m ixtures in the hope of devising a joint-sealing com pound of superior quality. As early as 1935, the sta te of California used a m a­

terial consisting essentially of about 70 per cent SC-4 asphaltic oil and 30 per cent rubber latex as a seal on about 680 linear feet of expansion joints on the heavily traveled highway between Lebec and G rapevine in Kern C ounty (1)*. These joints, spaced a t 100-foot intervals, were sealed im m ediately after the concrete surface was com pleted. When inspected in 1939, after 4 years of service, th e rubber com pound join ts were in tact and in good condition.

S tanton (2) reported early experiences (1936) of th e California Division of Highways w ith the new m aterial, indicating the necessity of choosing a good asphaltic oil and basing its selection on high d uctility a t low tem peratures. S tanton pointed ou t th e deleterious effects of m oisture in securing a good bond and showed how to convert the sealing com­

pound into a crack filler by cutting th e oil w ith gasoline before adding th e latex.

B y M arch, 1934, Woolf and R unner (3) had set up a procedure for testing various types of “resilient expansion jo in t fillers” in th e lab­

oratory. Among the nine types of fillers investigated were com pounds of asphalt and rubber w ith particles of vulcanized rubber.

Encouraged b y the results in California, th e neighboring sta te of Oregon experim ented w ith a seal m ade up of 30 p a rts of 60 per cent rubber latex and 70 p arts of 150-200 penetration asphalt. The m ixture was poured hot and the seal allowed to come w ithin 34 inch of th e pave­

m ent level. The ho t m aterial was covered w ith rubber grindings to complete th e seal and filling of the joint.

Im pressed by th e work in California and Oregon, engineers in M ass­

achusetts and Oklahoma began experim enting w ith sim ilar com pounds.

A form ula was developed in Oklahoma for a joint seal using th e following m ix tu re:

M aterial P a rts by weight

SC-4 5.475

38 per cent Latex 2.431

Lime 0.0553

Cresol Soap Solution 0.0444

Paraffin 0.0395

T he soap solution used in th e form ula was a p ro prietary m aterial of th e b ra n d nam e “ K rem ulso.” Experience in Oklahom a prior to 1939 (4) indicated th a t good joint seals are readily obtained w ith th e above mix if th e following precautions are taken: 1) thorough cleaning of th e con­

crete sides of th e jo in t; 2) accurate proportioning of m aterials; 3) un i­

* T h e n u m b e rs in p a re n th e s e s refer to th e b ib lio g ra p h y a p p e n d e d h e re to .

ASPHALTIC OIL-LATEX JOINT-SEALING C O M P O U N D 567

form ity of control of mixing, tem perature and consistency of each batch;

4) pouring of a uniform flush joint (seal); 5) delay of shouldering opera­

tions for one week after pouring of joints and 6) the exercise of care th a t joints are n o t poured a t tem peratures below 40 F.

As progress in the developm ent of bitum en-rubber m aterials in the U nited States came to th e atten tio n of highway engineers, various proprietary or commercial preparations appeared on th e American m arket, some of which showed considerable promise, and a few of which gave good results in actual service. Nevertheless, research continued in highway departm ents and other laboratories (5-9) on problems asso­

ciated w ith the developm ent of latex-bitum inous types of joint-sealing compounds having superior properties.

The M ichigan S tate Highway D epartm ent concerned itself a t an early date with these investigations and undertook the developm ent of a bitum inous-rubber sealing compound suitable for use on expansion joints in M ichigan climates (10). In December, 1936, project 36 G-4 was authorized by the A dm inistration for the investigation and develop­

m ent of new joint sealers, notably types using norm al latex and road oil.

W hereas considerable success has attended this project during its eight- year life, th e investigation is by no means closed. A t the present tim e consideration is being given to the use of synthetic latices as substitutes for norm al latex.

D E V E L O P M E N T O F C O M P O U N D S IN M IC H IG A N

Michigan investigations of joint-sealing compounds were first p atterned very closely after those of California insofar as m aterials and properties were concerned. However, th e scope of the project was soon enlarged to take into consideration m any significant factors relative to the be­

havior of these compounds, including properties, m aterials, adm ixtures, preparation and handling of the compounds in th e field.

I t was early determ ined th a t a m ixture of latex, lime and road oil of th e SC-4 type A.A.I. (1940 designation) gave the best results. In this mix prevulcanized, specially stabilized latex of 58.8 per cent concen­

tratio n of solids produced a very tough, elastic sealer, which set up rapidly. The w orkability of this mix was im proved by adding paraffin and varying th e percentage of lime. Paraffin also increased the tough­

ness of the set mix, b u t it tended to lower adhesion and increase “ graini­

ness.” Its use, therefore, was discontinued. L ittle success was ob­

tained w ith powdered rubbers, probably because of their relatively larger particle size and th e consequent slowness with which these m a­

terials disperse in road oil. Adhesion and ductility were gravely im­

paired by the addition of such inert fillers as bentonite (colloidal alum i­

num silicate), fine sawdust, diatom aceous silica, Fuller’s earth and cotton

in percentages sufficiently high to appreciably prom ote toughness and, therefore, were n o t given fu rth er consideration.

The sealing com pound has been found to undergo a steady, prolonged vulcanization over a period of years, resulting in th e progressive h ard en ­ ing observed in mixes several m onths after pouring. A ttem p ts to con­

trol vulcanization b y developing a vulcanizing agent of optim um ac tiv ity included investigations using sulfur flowers and sulfur m ono­

chloride. Results indicated organic sulfur to be more satisfactory as a vulcanizing agent th a n inorganic sulfur. The problem was com plicated by the necessity of m aintaining suitable w orkability for pouring.

According to the work of H. L. Fisher (11), all vulcanizing agents are either oxidizing agents or require the presence of oxidizing agents. If this view is accepted, th e presence of sulfur in the oxidizing group is not necessary, for the fundaniental reaction is one of oxidation-reduetion.

There are m an y substances besides sulfur capable of giving rise to such a reaction. Several were tried out, such as piperidine pentam ethylene dithioearbam ate, 50 per cent aqueous sodium m ercaptobenzothiazole, zinc oxide and casein.

In general, it was found th a t although the use of these vulcanizing agents produced laboratory mixes whose properties when set were highly desirable, th e q u an tity of vulcanizing m aterial required was so critical th a t a variation of about 1 per cent would determ ine th e difference between excellent w orkabihty and no workability.

The relative failure of sponge rubber to extrude under pressure, its com parative toughness when well vulcanized, and th e economic feasi­

bility of using 50 per cent air in th e mix prom pted an investigation of th e possibility of producing voids in th e sealing com pound, and of th e influence of such voids upon its properties.

The m ethod used em ployed th e chemical reaction which occurs be­

tw een sodium hydroxide and powdered alum inum , during which mole­

cular hydrogen gas is lib era te d : .

2 A l + 6 N aO H — 2 Na^AlO^ + 3 Hi

I t was found th a t a mix with delayed volume expansion and satis­

factory w orkabihty could be produced, b u t th a t here again th e q u an ­ tities of m aterials used were too critical for operations in th e field. T he properties of the resulting compound were too susceptible to very slight alterations in th e technique of m anufacture.

A satisfactory joint-sealing compound was finally developed in which prevulcanized latex was substituted for norm al latex. T his m aterial adhered satisfactorily to concrete, rem ained ductile and displayed low susceptibility over a wide range of tem peratures. I t possessed satis­

factory w orkabihty for pouring. Specifications for this seal are given a t the end of th e text.

ASPHALTIC OIL-LATEX JOINT-SEALING C O M P O U N D 569

The mixing and application of the compounded joint m aterial in the field presented a trying problem. Various mechanical devices were tried w ith th e object of mixing and pouring th e compound in one or two operations. Any such m ethod was found unsatisfactory, because the ra te of set could no t be effectively controlled. Finally, it was found th a t th e asphaltic oil and latex could be satisfactorily combined in small batches (3 gal.) by either mixing by hand or by a small m echanical agitator. After proper blending of th e m aterials th e com pound could then be readily transferred to a standard pouring pot for subsequent filling of the joint opening.

F IE L D P R O JE C T S S E A L E D W IT H A S P H A L T - L A T E X C O M P O U N D

By 1940, sufficient experim ental work had been done by the D ep art­

m ent to w arran t the use of the asphalt-latex sealing compound on regular concrete pavem ent projects. The task of mixing the compound and sealing th e joints became th e responsibility of th e contractor and his personnel. Expansion joints containing one-inch bitum inous premolded fiber boards were sealed on two complete projects w ith asphalt-latex joint-sealing com pound before the supply of rubber latex was stopped by th e W ar Production Board. These projects include the design section of th e M ichigan T est Road, projects 18-20 C3 and 67-37 C4 on M-115 between US 10 and M 66 northw est of Farwell, Michigan, and the G rand R apids-E ast B elt construction project F41-34 C6 on US 131 by­

pass south of US 16.

M ichigan Test Road

The joints on the M ichigan T est R oad were sealed in the sum m er and fall of 1940, using sealing compounds m ade with both norm al latex and prevulcanized latex for com parative study. The mixing equipm ent and m ethod of pouring th e joints are illustrated in Fig. l a and lb . P reparation of the joints prior to pouring was done in accordance w ith accepted practice for any type of joint-sealing m aterial. In general, th e operation was done in th e following m anner:

The asphaltic oil was heated to approxim ately 90 C. in ta r kettle (A),

Fig. la. To mix a batch of asphalt-latex m aterial, a q u an tity of hot asphaltic oil was drained into mixing drum (B) and lime added and

mixed into the asphaltic oil. The correct am ount of latex was allowed to flow slowly from container (C) into container (B) while constantly stirring to thoroughly blend the ingredients. The finished m ixture was then transferred from (B) into pouring can for subsequent sealing of th e joints as illustrated in Fig. lb.

Com pounds made w ith both norm al and prevulcanized latex have given excellent service during the first five years w ithout any m ain­

tenance whatsoever. However, present conditions indicate th a t the

Fig. 1a. (left)— Equipment used in preparing asphalt-latex joint sealing compound.

A — S tandard ta r k e ttle ; B— 5 g a l. m ixing drum ; C — 5 g a l. can to hold la te x .

Fig. 1b. (right)— Pouring asphalt-latex joint sealing compound. (N ote rubbery consist­

ency of the material.)

Fig. 2a. (left)— Joint seal containing normal latex after A)4, years in service. N ote partial failure in cohesion which appeared after 3 years in service. This phenomenon takes p lace in cold weather and disappears during summer months. Photograph taken M arch 2 1 ,1 9 4 5 . Fig. 2b. (center)— Joint seal material containing normal latex after 4 p j years in service.

Note consistency of material during warm weather. Photograph taken A ugust 1 5 ,1 9 4 4 . Fig. 2c. (right)— Joint seal containing pre-vulcanized latex. N ote that this material does not fail in cohesion during cold weather and possesses better durability qualities than those of the joint seal with unvulcanized latex. Photograph taken M arch 21, 1945.

ASPHALTIC OIL-LATEX JOINT-SEALING C O M P O U N D 571

Fig. 3a. (left)— Joint seal containing pre-vulcanized latex. Joint sealed O ctober, 1941.

Photograph taken O ctober 19, 1944.

Fig. 3b. (center)— Joint seal containing pre-vulcanized latex. Note unusual width of joint and perfect bond of joint seal material to concrete. Same joint as illustrated in

" a " . Photograph taken O ctober 1 9 ,1 9 4 4 .

Fig. 3c. (right)— Plasticity of the joint seal material illustrated in " a " after 3 years in service.

Temperature 50 F. Photograph taken O ctober 19, 1944.

prevulcanized latex produces a more durable compound. Fig. 2a, 2b and 2c illustrate the general condition of th e m aterial in th e spring of 1944 and 1945. The compounds have retained their excellent bonding and plastic characteristics. I t has been observed th a t a t some points th e joint seal has cracked or has lost some of its cohesive properties during th e w inter season although th e m aterial has rem ained plastic. In the sum m er these cracks disappear and th e m aterial appears to have con­

siderable life. This phenomenon is more common in th e compound m ade w ith norm al latex and evidently this is th e first stage in th e ultim ate failure of the joint-sealing compound. I t m ay be possible to correct this weakness where it first appears by an application of some appropriate treatm en t. This is being studied.

G rand Rapids— East Belt

This project was constructed the following year, 1941, by a different contractor, b u t the joints were sealed in the m anner described above, except th a t prevulcanized latex was used in preparing th e seals. The general condition of th e joints after 3 years is illustrated in Fig. 3a, 3b and 3c.

Q uantity and cost per joint

In the case of a norm al expansion joint of l-inch opening, the con­

crete slab being 22 feet wide and th e depth of sealer being % inch, the to tal volume of sealer used in each joint would be 198 cu. in. This would be equivalent to 0.857 gal. To allow for waste, a q u an tity of 1 gal. of com pound per joint seems to be a reasonable am ount for estim ate purposes.

Based on 1940 prices of m aterials in large quantities (50-gal. drum s for road oil, 10-gal. drum s for latex and 50-lb. lots for lime), a specific

grav ity of 0.981 for road oil, a specific grav ity of 0.949 for prevulcanized latex, and a specific gravity of 0.97 for th e final product, th e following m aterial costs can be stated for th e oil-latex jo in t sealer:

S E A L I N G O F J O IN T S W IT H A S P H A L T - L A T E X C O M P O U N D

Experience in M ichigan has shown th a t asphalt-latex joint-sealing compounds m ade and applied in accordance w ith th e following practices are the m ost satisfactory.

Preparation of the joint

As stated in the 1942 specifications of th e M ichigan S ta te H ighw ay D epartm ent, th e tops of expansion joints and all edged jo in ts m u st be sealed as soon as the curing agent is rem oved and before an y traffic is perm itted on th e pavem ent. Jo in t openings m u st be thoroughly cleaned, all contact faces wire brushed, and surfaces m u st be d rj1- when th e seal is poured. Any m em brane curing m aterial rem aining afte r wire brushing would be alm ost certain to afford a good bond for th e asph alt- latex compound.

Preparation of the asphalt-latex compound

A ta n k of a t least 25 gal. capacity m u st be provided for h eatin g th e oil (Fig. la ). The mixing ta n k should be of 5 to 10 gal. an d a stirring device m ust be used which will produce a hom ogeneous m ixture of uniform consistency.

The following steps are followed in com pounding:

a. H eat oil to tem perature of betw een 85 and 95 C.

b. M easure correct q u a n tity of lime.

c. M easure correct q u a n tity of oil.

d. M easure correct q u a n tity of latex.

e. P our correct q u an tity of h o t oil into mixing tan k . f. Add correct q u an tity of lime to oil in mixing tan k . g. S tir lime into oil rapidly u n til thoroughly dispersed.

h. Continue to stir while adding approxim ately one-half of th e correct q u an tity of latex to the mixing tan k. C ontinue to stir u n til thoroughly blended.

i. Continue stirring while adding balance of latex u n til mix is homogeneous and of desirable thickness.

No more com pound should be m ade th a n can be poured before it becomes too thick for handling. Stirring can be done b y h an d or m e­

chanically. A 1-gal. container w ith a handle on one side and a spout on the other has been found suitable for pouring. In general, it m ay be

(a) Per l b ..

(b) Per g a l.

(c) P er joint

$0.0842

$0.68

$0.68

ASPHALTIC OIL-LATEX JO INT-SEALING C O M P O U N D 573

said th a t 5 gal. of com pound m ay be prepared a t one tim e and still rem ain sufficiently workable for th e operator to pour th e- entire am ount.

Com pound or oil can be removed from equipm ent w ith kerosene or other organic solvent. Traces of latex can be flushed- out w ith w ater when wet or removed by m echanical stripping when dry.

L A B O R A T O R Y TESTS

C ertain ten tativ e laboratory tests have been developed by th e M ichi­

gan S tate Highway D epartm ent for evaluating and com paring various properties of joint seals (10). The properties studied for which tests were devised included ductility (cohesion), adhesion and flow properties

(viscosity).

Ductility and adhesion

A stan dard asphalt ductility m achine was employed, using specially constructed steel forms. (Fig. 4a). These forms functioned to grip regular m ortar briquettes which were molded w ith a brass strip im bedded through their centers in such a way th a t they left the molds in sym m etri­

cal halves, each half presenting a working surface of one square inch cross section.

Preparation of the Briquettes. A cement m ortar consisting of tw o parts n atu ra l sand to one p a rt portland cement w ith sufficient w ater for a troweling consistency is prepared. This m ixture is placed in gang molds of the type used in m aking A.S.T.M . tensile strength briquettes. A m etal brass divider is placed in the center of the mold so as to divide the briquette into two sym m etrical halves of one square inch working

Fig. 4.— Ductility and A dhesion Test: a. (left)— Specimen in place ready for test;

b. (right)— M o ld assembled prior to pouring in joint seal.

Fig. 5a. (left)— Viscometer used to study flow properties of joint sealer.

Fig. 5b. (center)— Flow cells used with viscometer.

Fig. 5c. (right)— Flow cell assembled and ready for determining viscosity of joint seal.

surface area each (Fig. 4b). Specimens no t having perpendicular faces are rejected.

T he b riquettes are cured in th e m oist room for one week, th en allowed to air dry before use. The faces are ground on a glass p late prior to use w ith G rade F C arborundum powder to remove irregularities and laitance m aterial after which th ey are washed and surface dried.

Preparation of the Sealer. A m ercury am algam ated brass m old con­

sisting of tw o side pieces, b ottom plate, and three “ C ” clam ps is attach ed to opposite briq u ette halves so th a t a 1 cu. in. space betw een th e faces can be filled w ith th e sealing com pound to be tested. (Fig. 4b). T he compound is heated to its application tem p eratu re, stirred and poured into th e 1 cu. in. space a little higher th a n th e u p p er surface of the briquette.

Method of Conducting the Test. A fter th e sealing com pound has been poured, th e specimens are allowed to stan d over n ig h t an d excess com­

pound over 1 cu. in. is trim m ed off w ith a h o t knife. T he clam ps are removed and th e side pieces and b o tto m p late are disassem bled. T he specimens are placed in a refrigerator to prevent deform ation.

A stand ard ductility m achine is adap ted for operation a t th e ra te of 1 in. per hr. by use of necessary speed reductions. T he glycerine b a th used for low -tem perature m easurem ents is m aintained a t 0 F. b y suitable additions of crushed dry ice and adequate stirring. Specim ens are placed in th e b a th a half hour before testing. Fig. 4a shows th e specimen in place and ready to be tested.

The distance th e specimen can be draw n in inches before failure in bond (adhesion) or in ductility (cohesion) is recorded, and th e ty p e of failure is noted.

ASPHALTIC OIL-LATEX JOINT-SEALING C O M P O U N D 575

Viscosity

The constant tem perature b a th of a K opper’s viscom eter was used in developing a te st for the rheological properties of joint-sealing compounds, as shown in Fig. 5a. Special flow cells were designed (Fig. 5b) em­

bodying th e use of semi-ball ground-glass joints and clamps, which were furnished b y th e Scientific Glass Com pany. The te st was based on a m ethod proposed by Bingham and Stephens (14), m aking use of the form ula of P itm an and Troxler (15):

PRH

T) = —---

4 h L

where t? = viscosity in poises

P = pressure applied in dynes per cm.2 L = length of column of seal, cm.

t = tim e of flow, sec.

h = length of extrusion in cm. in tim e t R = radius of tube in cm.

Viscosities were plotted on the standard A.S.T.M . chart, on which th e double log of viscosity versus th e log of th e absolute tem perature is a straight line function. The slope of this line is called th e susceptibility of the m aterial, and represents th e degree to which its viscosity is affected by tem perature. This value is also referred to in th e literature as viscosity index.

Pouring of Sealing Compound into Flow Cell. T he com pound is heated to application tem perature, melted, mixed to hom ogeneity and poured into the flow cell (Fig. 5b). The specimen is allowed to stand over night.

Assembly of Flow Cell. The cylinder is rem oved from th e am alga­

m ated plate, th e u n it is assembled in a horizontal position as in Fig. 5c, and special clamps are placed in position to hold th e glass joints in place.

M illim eter scales are placed a t th e rear and front of th e tube.

Test Procedure. The flow cell u n it and scales are placed in th e constant tem perature b ath and left for 30 m inutes. T he vacuum hose is attach ed to one end of the cell, th e other end being left open to the atm osphere unless more pressure is required to obtain flow. The tim e of flow from the Yi cm. m ark to th e 1 cm. m ark is recorded, as well as th e pressure indicated on the m anom eter.

Practical application of laboratory tests

The foregoing laboratory tests were conducted on joint-sealing m a­

terials of th e following ty p e s :

Types 1 and 6. P roprietary brands of asphalt-rubber joint-sealing compound of the hot-pour type.

Type 2. Commercial joint seal of th e asphalt type.

Type 3. Experim ental asphalt-rubber com pound n o t com m ercially available.

Type I+. Seal m ade of 30 per cent prevulcanized latex and 70 per cent SC-6 asphaltic oil.

Type 5. Seal m ade of 30 per cent norm al latex and 70 per cent SC-6 asphaltic oil.

The above seals were so m ade as to be free of extraneous w ater, coal ta r and other ta r products, pressure still residua, pitches, or o ther pro­

ducts of decomposition. M anufacturing specifications for ty p e 2 were such as to preclude heating the bitum inous m aterial above 700 F. or exposing it to pressures appreciably above atm ospheric, an d to assure th a t the finished product possess characteristics w ithin th e following lim its:

1. Specific g ravity a t 77 F. 1-22 to 1.30

2. F lash point, Cleveland open cup N o t less th a n 350 F.

3. M elting point, ring and ball 122 F to 135 F.

4. P enetration a t 77 F., 100 gm., 5 sec. 40 to 50

5. D u ctility a t 77 F. N o t less th a n 30 cm.

6. Loss a t 325 F., 50 gm., 5 hrs. N o t m ore th a n 3.0 (a) P enetration a t 77 F ., per cent

100 gm., 5 sec. N o t less th a n 20 7. (a) B itum en sol. in CS² 62 to 75 per cent

(b) Ash on ignition 20 to 32 per cent

(c) Difference betw een 100 per cent N o t less th a n 4 and sum of (a) + (b) per cent

R esults of the adhesion and cohesion (ductility) studies on th e above m aterials are shown graphically in Fig. 6. All specimens w7ere draw n in th e ductility b a th a t a ra te of 1 in. per hr. A t this low ra te of drawing, all specimens gave good results a t room tem peratu re. As a m a tte r of interest and for comparison a 24 penetration asp h alt was included in this group of tests. This m aterial failed a t a distance of 0.125 in. In Fig. 6, distance draw n is plotted against tem p eratu re of the b ath , th e lowest tem perature being O F . A t 0 F., seals No. 4 and 5 wren t to th e lim it of th e te st (2 in.), whereas seal No. 1 wren t 0.625 in. before failure and b o th No. 2 and No. 3 failed in adhesion and cohesion a t 0.125 in.

In carrying out adhesion and cohesion studies, i t was found virtually impossible to get good adhesion to th e m o rtar b riq u ettes when th e la tte r were cold and dam p. This fact suggests th e significance of cold, dam p w eather during joint sealing operations and th e practical im portance of developing a m eans of elim inating or m inim izing its deleterious effect on adhesion of joint-sealing m aterials to th e slab. No such m eans has y e t

ASPHALTIC OIL-LATEX JOINT-SEALING C O M P O U N D 577

Fig. 6.— Effect of temperature on adhesion and cohesion.

been found satisfactory other th an straightforw ard cleaning and drying of the joint surfaces.

Flow rate properties of the five types of joint seal as m easured by the apparatus described above are plotted in Fig. 7.

C U R R E N T S P E C IF IC A T IO N S F O R A S P H A L T - L A T E X J O IN T S E A L

The following additional specifications are given by the M ichigan S tate Highway D ep artm en t:

The vulcanized latex shall be an aqueous dispersion of rubber particles in an ammoniacal solution, having a rubber solids content not less th an 58 per cent. I t shall be kept in sealed containers to prevent evaporation of the emulsifying agent. The vulcanized latex shall be protected from tem peratures less th an 40 F. and greater th an 100 F.

VISCOSITYpoises

T P y V P R O F E R I IES

P R O P R I E T / R Y T V P E S l

A S P H A L T » T E » T Y P I Ï

3" 25” y ? 4Ô1 50* 60s

T E MP E R AT O R E ---C E N T I G R A D E

Fig. 7.— Flow properties of joint sealers.

ASPHALTIC OIL-LATEX JOINT-SEALING C O M P O U N D 579

The asphaltic oil shall be homogeneous, shall not foam when heated to th e required tem perature and shall conform to th e following require­

m ents :

M inim um M axim um

Specific gravity, 25/25 C. 1.0

W ater, per cent by volume 0 .5

Flash point, Cleveland open cup, deg. C. 120

Loss on heating a t 163 C., 50 gm., 5 hr., per cent 6

Viscosity, Saybolt Furol, a t 60 C. 350 600

Solubility in carbon tetrachloride, per cent 99.5

Oliensis spot test Neg.

Residue of 100 penetration:

P er cent residue 70

D uctility, 25 C., cm. 100

D uctility, 4 C., cm. 7

Sulfur content, per cent 2 4

H ydrated lime shall conform to the requirem ents for M ason’s h ydrated lime in the 1942 specifications for H ydrated Lime for S tru ctu ral Purposes, A.S.T.M . Designation C 6.

The proportions by weight of the m ixture shall be:

Lime, Ca{OH)i 2 p arts

Vulcanized Latex 30 p arts

Asphaltic Oil 70 parts

Compounds m ade in accordance w ith the above procedures have given satisfactory performance in M ichigan over a period of 4 years.

AC KNO W LEDGM ENTS

The w riter is indebted to Messrs. George A. Mansfield and Thaddeus Wolczynski, formerly of th e M ichigan S tate Highway Research Labora­

to ry staff, for their early researches on im p o rtan t fundam ental and practical aspects of asphalt-latex joint-sealing compounds.

BIBLIOGRAPHY

1. Anderson, Andrew P.: “Some Experiences w ith Expansion Jo in ts in Concrete Pavem ents,” Public Roads,Vol. 21, No. 3, M ay, 1940.

2. Stanton, Jr., Thos. E .: “Laboratory Develops an Im proved Jo in t Filler,”

California Highways and Public Works,Vol. 14, No. 9, pp. 14-17, September, 1936.

3. Woolf, D. 0 ., and Runner, D. G .: “L aboratory T est of Resilient Expansion Joint Fillers,” Public Roads, Vol. 15, pp. 17-25, M arch, 1934.

4. Reid, Carl: Oklahoma State Highway Commission: “A sphalt-Latex Jo in t S eal,”

Highway Research Abstracts,July, 1939.

5. “New Jo in t Filler for Concrete Pavem ent,” Canadian Engineer, Vo. 44, p. 241, February 13, 1923.

6. Bragg, J. G.: “Poured C onstruction Joints for Concrete P av em en ts,” E n ­ gineering News-Record,Vol. 91, p. 687, O ctober 25, 1923.

7. Thoms, R. E .: “Dowels and Jo in t Fillers for Concrete P avem ents,” Engineering News-Record, pp. 318-319, F ebruary 25, 1935.

8. “L atex in R oad Use,” Rubber Age,39; 221, June, 1936.

9. “Sponge R ubber Expansion Jo in t F iller,” Rubber Age,42; 186, D ecem ber, 1937.

10. Mansfield, George A., and Wolczynski, Thaddeus, D ep artm en tal R eports on Jo in t Seal Investigation: “Field S tudy of Jo in t Seals,” Septem ber 12, 1939; “P ositive Sealing of Expansion Joints in Concrete P av em en t,” O ctober 1, 1939; “R ep o rt on L aboratory E valuation of Field T ested Jo in t Seals,” M arch 1942. M ichigan S ta te H ighway D epartm ent.

11. Fisher, H. L.: “Vulcanization of R ubber,” India Rubber World,p. 38, M arch 1, 1940.

12. Gehman, S. D., and Field, J. E . : “ Colloidal S tructure of R ubber in Solution,”

Industrial and Engineering Chemistry,Vol. 32, N o. 2, p. 282, F ebruary, 1940.

13. W are, John C.: The Chemistry of the Colloidal State, p. 246, Jo h n W iley &

Sons, Inc., 1930.

14. Bingham and Stephens: “T he A lternating Stress M ethod for M easurem ent of th e Consistency of Very Stiff M aterials,” Physics,Vol. 5, pp. 217-20, August, 1934.

15. P itm an and Troxler, Physics,Vol. 5, p. 222, August, 1934.

r T o f a c ilit a t e s e le c tiv e d is tr ib u tio n , separate prints o f th is t i t l e ( 4 2 - 2 3 ) a r e c u rre n tly ~ l a v a il a b le fro m A C I a t 2 5 c e n ts e a c h — q u a n tify q u o ta tio n s o n re q u e s t. Discussion L o f th is p a p e r (c o p ie s in t r ip lic a t e ) s h o u ld re a c h th e In s titu te n o t la t e r th a n S e p t. 1, 1 9 4 6 J

Title 42-23 — a p art of PROCEEDINGS, A M E R IC A N CONCRETE INSTITUTE V o l. 42

J O U R N A L

o f the

A M E R I C A N C O N C R E T E I N S T I T U T E

( c o p y r ig h te d )

V o l. 17 N o. 6 74 0 0 S E C O N D BO U LE V A R D , DETROIT 2, M IC H IG A N June 1946

P e tro g rap h y of Concrete A g g r e g a te *

By ROGER RHOADES and R. C. M IE L E N Z f

M e m b e rs A m e ric a n C o n c r e te In s titu te

S Y N O P S I S

Serviceability of a concrete aggregate depends upon the m anner in which it joins w ith cement to determ ine the quality of concrete. Yet, standard acceptance tests do not measure properties which are directly responsible for performance of aggregates enclosed in concrete; new methods of aggregate investigation are needed. Experience shows th a t petrographic study can supply valuable inform ation on a routine basis, and th at, wherever possible, ordinary acceptance tests should be supple­

m ented by exam ination by a petrographer fam ilar also w ith problems of concrete. The significant properties of aggregates are discussed, and methods of petrographic study of aggregates are described.

An extensive bibliography is appended and referenced in the tex t for the benefit of readers, especially petrographers, wishing to explore further the concepts treated only briefly in this paper.

IN T R O D U C T IO N

Serviceability of concrete aggregates depends upon the strength and durability of the union which th ey establish with portland cement.

S tandard acceptance tests, currently applied independently to aggre­

gate and to cement, do no t perm it satisfactory prediction of the quality of concrete. Such tests of aggregates m ay determ ine properties which make “good” or “ poor” rock, b u t they contribute little to an in ter­

pretation of th e rock’s concrete-making properties. F or exam ple,' tests on crushed quartz reveal how strong, im permeable, and durable it is, b u t they fail to indicate th a t it m ay nevertheless be an inferior aggregate.

D urability or lack of durability, strength or weakness, or any other property of aggregate should concern the concrete engineer only to the extent th a t the property affects concrete. A t this late date, service histories remain the only wholly reliable criteria of suitability. Conse-

*R ec eiv ed b y th e I n s tit u te , J a n . 29, 1946.

tC h ie f G eo lo g ist a n d P e tro g ra p h e r, resp ectiv ely , B u re a u of R e c la m a tio n , D e n v e r, C o lo ra d o . (581)

quently, a reorientation of acceptance testing is necessary; practicab le ^ tests m ust be designed which will determ ine the properties affecting quality of concrete. These properties are reviewed in this papei.

P roperties of aggregates comprise 1) those of the individual particles, and 2) those characterizing th e entire assemblage. T he latter, which comprise gradation, m oisture content, and bulk weight are easily de­

term ined and will no t be considered here. P roperties of • in dividual aggregate particles originate in th eir m ineralogic com positions, tex­

tures, and structures. These are petrographic properties, and th ey m ay be determ ined by petrographic m ethods. P etro g rap h y has long been used in aggregate selection b u t its use should be extended.

P E T R O G R A P H IC P R O P E R T IE S O F A G G R E G A T E

P roperties of aggregate are num erous and complex, and th ey originate in several ways. T he original n atu re of the rock m ay control its con­

crete-m aking qualities. Thus, rocks containing gypsum are always som ew hat soluble, opaline m aterials react chem ically w ith alkaline solutions, and shales are usually soft and absorptive. Conversely, m any properties are n o t directly related to th e rock ty p e b u t were induced by w eathering, solution, saturation, or encru station by ground w aters, by fracturing and jointing related to th e geologic history of th e region, or by some other n a tu ra l alteration. Thus, granites m ay be either h ard or disintegrated, and sandstones m ay be either friable or tig h tly cem ented, w ith resulting variations in stren g th and porosity. Therefore, p etro ­ graphic stu d y of concrete aggregates m ust be dual: 1) properties in­

herent to the rock m ust be in terp reted in relation to 2) th e n a tu ra l alteratio n which it m ay have experienced.

The m ost im p o rta n t properties of concrete aggregate are discussed below. I t m ust be noted th a t these properties are com m only in depend­

en t of rock ty p e since rocks of any given ty p e m ay have w idely different concrete-m aking qualities. Effects of secondary alteration s, of which w eathering is th e m ost common, are im p o rta n t only insofar as th e essen­

tia l properties of th e aggregate are changed; where significant, th e possible effects of w eathering are in d icated .

Chem ical reactivity

Few, if any, rocks or m inerals are chem ically in e rt while enclosed in P ortland cem ent. T here are four m ain ways th a t an aggregate m ay be chemically deleterious. F irst, it m ay contain w ater-soluble co n stitu ­ ents which can be leached, w ith a tte n d a n t loss of stren g th an d increase in porosity. Leached m aterial m ay form unsightly efflorescence or in ­ directly lead to surface scaling(u ■ v- 56h Second, soluble constituents or products of oxidation m ay re ta rd or m odify norm al h y d ratio n of cem ent.

* N u m b e rs in p a re n th e s e s refer to b ib lio g ra p h y a t e n d of te x t.

PETROGRAPHY OF CONCRETE AGGREGATE 583 Fig. 1— Pop-outs and staining of concrete produced by oxidation of pyrite in particles of coarse aggregate.

Thus, oxidation of pyrite (FeS2) in the aggregate resulted in pop-outs, local disintegration, and unsightly staining of th e concrete a t a dam in Cal­

if ornia^12) (Fig. 1).* Similar effects have been described by L itehiser(13).

Also in this category is the deleterious action of the m ineral alunite (K 2A Ię,(OH)i² (SO ^i) in m ortar b ars(14). In one m onth the bars ex­

panded significantly, cracked, and warped, probably as th e result of sulfate a tta c k on the cement, since secondary calcium sulfoalum inate was ab undantly produced. Similar effects m ight be expected from other aggregates containing soluble sulfates(15). Gypsum {CaS0^.2H20 ) in ex­

cessive am ounts is deleterious to concrete^16’ pp- 188- 194h

T hird, certain aggregates are attacked by high-alkali cements^9’ 17h T he reactions lead to internal expansion, external cracking, and de­

creased elasticity and strength (Fig. 2 and 3). Rocks and m inerals known to be susceptible to this kind of reaction are: opal; m any vol­

canic rocks of acid to interm ediate composition (high to m edium silica content); glass (artificial or natural, excluding the basic types such as basaltic glass) ; chalcedonie rocks (including m any cherts and flints) ; some phyllites; and trid y m ite ® 10’12’14'17'18'19-20'21' ^ A m éliorants are being sought b u t a t present, where such rocks m ust be used, specifica­

tion of low-alkali cem ent is im perative. L im itation of alkali content to below 0.6 per cent (N a20 + K 20, expressed as soda-equivalents) has avoided or significantly retarded deterioration, even though the aggre­

gates are highly reactive® 20'24).

F ourth, certain common m inerals (e.g., zeolites) are capable of base- exchange. In this process, alkalies in these m inerals are exchanged for calcium in solutions perm eating th e concrete®. Released alkalies m ay th en a tta c k susceptible aggregate particles, and efflorescence m ay form on or near the surface of the concrete. Studies by th e B ureau of

* H o w e v er, p y r ite in a g g re g a te is n o t alw a y s su sc e p tib le to s u c h d ec o m p o sitio n ; m a n y co n c re te p a v e ­ m e n ts in a n d a b o u t C o lo ra d o S p rin g s, C o lo ra d o , c o n ta in p y ritife ro u s ag g re g a te s w h ich sh o w n o sig n s of a l te r a t io n a f t e r 19 y e a rs of serv ic e.

R eclam ation and others suggest th a t such base exchange, involving a granodioritic aggregate, m ay account for efflorescence and surface scal­

ing of concrete on the dow nstream face of a thin dam in southern C ali- forniaiI2). T ests conducted in th e B ureau of R eclam ation laboratories indicate th a t m ost n a tu ra l aggregates will ex tract calcium from alkaline solutions. Rengade, Lhopitalier, and de F on tm ag n e(23) and, m ore re­

cently, H ansen(is:> have shown th a t some n atu ra l aggregates release iVa20 and K ',0 when em bedded in cement.

Porosity, permeability, and absorption

Pore characteristics of aggregate are im p o rtan t controls of chemical and physical stability, and th ey strongly influence th e bond w ith cement.

Pore characteristics significantly affect th e stren g th of an y m aterial, and th ey determ ine absorption and perm eability. As a result, th e y control both d urability u nd er freezing and thaw ing conditions, an d ra te of chemi­

cal alteration. Three characters of pores determ ine physical an d chemical stab ility of aggregate. T hey are 1) absolute pore volum e, 2) size of the pores, and 3) th eir continuity. These characters are reflections of the

Fig. 2— Typ ical a p ­ pearance of field con­

crete severely affected by reaction between aggregate and high- alkali cement. The concrete is 6Y2 years old.

F ig . 3— P h o to m ic r o ­ graph of concrete from Parker Dam , showing microfractures produced as a result of reaction between a particle of rhyolite and alkalies in cement.