TECHNICAL INFORMATION ON BUILDING MATERIALS

FOR USE IN THE DESIGN- OF L0W-C03T HOUSING

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THE NATIONAL BUREAU OF STANDARDS

UNITED STATES DEPARTMENT OF COI£!ERCE

WASHINGTON, D. C.

November 1, 1937

WATER-TIGHTNESS OF 1KPAN5I0IT JOINT HATER I ALS

IN OOI'TC RETB R06?~'C0N3TRudTI o¥l

The information contained in this paper was obtained from the results of tests

conducted by D. ¥. Wessler, on 36 proprietary joint fillers, representative of 13

types of plastic and metal expansion joint materials, as applied to the problems of

concrete roof and parapet construction. The tests included accelerated weathering;

low temperature ; high temperature.; cycles of low temperature, soaking in water, and

high temperature; and outdoor exposure. Special forms of sheet metal joints were

tested for resistance to cycles of compression and tension only; that is, fatigue.

The plastic materials investigated, included: rubber latex; p remolded tvpes

(sponge rubber, etc.); bitumens; plastic bi turnons ; rubber in flux; and oil mastics.

The rubber latex typo is a recent development, still in the experimental stage

Each sample consisted of three separate parcels; (l) a white paste of creamy con- sistency , (2) a fine powder resembling an aluminous cement, (3) a mixture of parcel

No. 2 with granulated cork. Numbers 1 and g wore mixed for costing the surface to

bo joined. After this coating had hardened, a mixture of 1 and 3 was used to fill

the joint. 'Zee material hardens rather slowly, especially on the interior, and son siderablo shrinkage occurs. The hardened mass b as the properties of rub or uu

bonds well with concrete.

Another special type is the Grand joint, int endec, for a specific purpose. It

consists of a cement-asbestos board grooved on each face to receive a bead of caulk

ing material. This expansion gasket is intended for use in vertical joints of copings , cornices, belt courses, etc. The gasket is made the same shape as the vertical cross section of the course of stone in which it is to be usee . The grooves

parallel the edges, forming a closed fi.rure somewhat smaller than the cross section

of the rnasc.iry unit joint. The bead of caulking material is placed in the grooves

with a caulking gun just before each stone- is set. This type of joint filler con

bo used only during construction of the building. The ad v..: it age is th. t having the

joint thoroughly scaled and the caulking deep • in tho joint, the plastic is not

forced to tho surface by high temperatures. This should prove more dur.xlo than
caulking compound applied in the usual way.

An extruded rubber type is made about 1/4 inch wider than the joint and

forced in after the concrete has hardened. The elasticity of the rubber is

depended upon to maintain a firm contact with the materials joined.

The sheet metal joints examined were evidently developed for concrete

road construction, but were subjected to such tests as are of interest in

connection with roof slab use.

METHODS OF TESTING

(a) Weather omet

o

r Test s; A determination of the resistance of materials

to the effects of alternating water spray, and light and heat from a carbon

arc lamp. This is an accelerated weathering tost. Results wore determined

by appearance and changes in plasticity (penetrometer test).

(o) Concrete Joint Exp a nsion: Two concrete blocks, controlled in lateral

motion by bolts and nuts, were constructed. A small reservoir was made in

the tops of the blocks to permit the joints to be tested for water-tightness.

Three specimens of each sample were used in the following tests: exposure on the roof; cold storage; hot storage; and temperature and moisture cycle.

(c ) Compressive Te sts; The specimens of premolded joint materials were

tested in compression by means of a 100,000 pound mechanical testing machine,

operated at a speed of 0. Oh-inch per minute. Fifty percent deformations of

the thickness of the sample were made and the rate cf recovery studied after

compression.

(d) Absorpt ion Tes ts; The specimens were oven-dried for 24 hours at a temperature of 50°C. After removal from the oven the samples were cooled and

weighed, then immersed in water. After 24 hours in the water, they were re- moved, surface-dried with a damp towel and immediately weighed. The gain in

weight times 100, divided by the dry weight , gave the percentage of absorption.

(e ) Fatigue Te sts ; The only materials subjected to the fatigue tesb,

which consisted of repeating; the cycle of contraction and expansion of the

joint, were those of the metallic type.

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Me at her omet or Tos t; 'The two samples started to blister and crack during

the first 24 hours of exposure. After 6 weeks one sample was so badly shrunken

and cracked that the tost was discontinued. Another sample was removed in a similar condition after 9 weeks, but was still somewhat pliable at the bottom

(l-inch below the surface exposed to light).

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Outdoor Exposure ; Samples gave satisfactory extension values after

12 weeks, one sample giving a maximum value of 3/3-inch. Only one bond

failure occurred in the 6 tests made.

Lou Temper atur

e

: One sample cracked within the joint filler, causing a failure at 0.06-inch extension. Samples showed good bond properties.

High Tempe rature ; Results were consistent, giving extension of l/8-inch

before failure.

Cycles of Heat , Odd and Mo is ture : Samples gave extension values of over 0. 2-inch. Failure was usually in the joint material itself, but one failure occurred in the bond.

PR.3T0LDHD TYPE

Went hc-r one

t

~ r To st; Out of 12 samples, the only materials of this class

which showed any serious effects from exposure were two sponge rubber samples.

One shrank, warped and became very hard. The other showed a similar effect,

but to a much less degree. Rubber-bound cork and extruded rubber also suffered

some hardening effects. The premolded asphalts showed surface hardening, but

this was not considered serious. Cork samples were not visibly affected, although there was an appreciable weight loss.

- Outdoor Exposure: At the end of the exposure period, 4 of these types

leaked without extension, and the extruded rubber was the only one that gave

an extension value as high as 0. 2-inch. Tests at the end of 6 weeks without

extension showed that most of the specimens were water-tight. One asphalttype and one fiber-typo joint split in the extension tests.

Low Temp era ture : One fiber-type, one asphalt-type and the extruded rubber

sample gave fairly satisfactory performance in this test. Failures were mostly

in the bond, but one asphalt sample and two fiber samples split during the ex- tension of the joints.

High Temperature : Extensions in the fiber, asphalt and extruded rubber

samples gave values of more than 0.1-inch before failure. The results of this

type seem to depend largely on the strength of the bond with the concrete.

Cycles of Heat, Cold and Moistur e: Two samples gave extension values of over l/s-irich. The others ranged from zero to 0. 06-inch. Practically all of

the failures were in the bond.

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Weather ometer Test ? Six samples of bituminous materials for hot application were subjected to this test. None was materially injured, but all

formed hard skins on the exposed surface, which prevented a reading on the

penetrometer. As a class, these samples were affected less than other types

in this test.

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Out door Expo sure: All samples were found to be water-tight at the end

of 6 weeks. At the end of 12 weeks all were tested by extension to failure,

the highest average value for one sample being 0. 13-inch and the lowest 0.03-

inch.

how Temperature: This test produced a rather hard and brittle condition.

The highest extension before failure was 0.08-inch. Two failed in the bond and

three cracked in the joint filler.

H i "h Temperatur e ; All samples were very soft. With one exception, extensions of 3/8-inch without failure were obtained.

Cycles of

' Heat, C old and Moi skare : Three samples were difficult to keep

in the joints. Two others shrank excessively and leaked without extension.

Five samples gave high extension values at the end of the test.

PLASTIC BITUMENS

Weather

o

meter Test: Seven samples of cut-back bitumens with fillers

(intended for cold application) were included in this test. All except one sample showed a very marked change in plasticity and this one developed a hard

film on the exposed surface. After a short time, six of the samples developed

brittleness

.

Outdoor Exposure: Test results were variable, two showed leaks without

extension and only one showed a high extension value. Two failed by shrinkage

and cracking. Failures indicated that the materials were generally lacking in

adhesive properties.

low Tern per atur

e

: All of these materials gave fairly satisfactory performances in this test. Four gave extension values of more than 3/8-inch.

Two failed in bond under comparatively low temperatures.

H igh Temperature : Difficulties were experienced in keeping some of these

materials in the joints at high temperature. One became rather hard and another

suffered from loss 0? oil. Two showed high extension values, while the other

four ranged from zero to about l/8-inch.

Cy c 1 e s of Heat

,

C

0

Id and tfnis tur

e

: He suits on four of the seven samples were rather unsatisfactory. Two of these leaked without extension of the

joint. Only one sample gave consistently high extension values.

j’’ HUB5HH IN FLUX.

Weather cmet er Te 3 1 ; One sample was tested. After 6 mouths exposure a thin crust was formed on the surface, but otherwise there was no apparent

change. The weight loss was very small.

Outdoor Exposure ; The thin consistency of this material caused excessive

losses around the gaskets (used to hold the material in the joint). The

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specimens maintained water-tight joints to the end of the test and gave ex- tension values of 3/8-inch.

Low Temperature : This material was slightly stiffer at the low temperatures, hut did not fail at 3/8-inch. extension.

High Temperature : The material was difficult to confine at high temperature, but gave a high extension value.

Cycles of Heat, Cold and Moistur e: Showed uniformly high extension values,

with no failures at 3/ 8- inch.

OIL MASTICS

V/oathoroneter Test ; Four materials were tested; two were rather soft, one somewhat stiffer (a gun grade), and the fourth quite stiff (a knife grade). This

latter became hard on the surface during the first 15 days. Even after 3 months

exposure, however, with the surface of some of the samples becoming hard and

brittle, they remained plastic below the hard film.

Out door Exposvr a ; The soft materials gave- good performance. The gun grade

showed a weak bond, while the knife grade gave fairly satisfactory extension

values

.

Low Tem p e r at ur c ; Three samples were satisfactory, while one failed at a low extension.

High Temporata-.ro ; The gun grade sample gave a low extension value. The

others ranged from 0.09 to 0.33-inch.

Cycles of Heat, Cola ana Moisture: Of the two soft grades, all samples

gave high extension values except one, which leaked without extension because

of excessive shrinkage. The knife gr ..do sample f ilod in bond under an extension of slightly more than l/8-incb , while the stiff gun grade material gave

less satisfactory results.

FA' ’I CITS TEST'S

Three samples of prefabricated sheet metal joints wore submitted and

tested. The joints were made by casting the samples in concrete blocks and

subjecting them to cycles of contraction nd '"expansion until the motel

cricked. The results of the test on 8 samples , for joint movements from

0.25 to 0. 46-inch, were as follows:
Nesigna- Move- No. of

tion ment cycles

Mg 0.440 258

.440 285

M2 .450 202

.450 205

MS .250 458

.375 +34

M3 .375 78

Mg .460 46

Mp .370 327

.370 478

Mi .350 750

M-j .412 234

1 .412 484

Nature of failure

Crack started at center.

Failure

.

Crack started at center.

Fa i lure.

No apparent change.

Cracked at center.

Cracked at center.

Cracked at center.

Cracked where metal enters concrete.

No change, test ended.

Cracked where metal enters concrete.

Cracked where metal enters concrete.

Cracked at top of bellows.

CONCLUSIONS

1. The rubber latex expansion joint materials gave good bonding and

extension values but indicated unsatisfactory durability.

2. The fiber boards impregnated with bituminous materials wore variable

in their behavior. Some of the experimental joints leaked without extension

and a few gave extension values over 1 /3-inoh.

3. The premolded asphalt joints gave results simil .r to those of the

fiber boards. The origins 1 shrinkage of the concrete in hardening is likely

to break the bond. Such materials showed little clastic recovery, and the

tightness of the joints at low temperatures depended upon the bonding properties. In large structural members , the shrinkage of the concrete may cause failure of the joints.

4. The sponge rubber samples gave somewhat more consistent results than

the fiber and asphalt boards, but the extension values were all rather low.

The durability of these materials, when exposed to light, was not very satisfactory.

5. Tests on cork joints showed extension values as high as 0.08-inch,

but the results were not very consistent. Inspection of materials in service

showed that water-tight joints were not obtained when concrete wa s po\ired next

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to the cork. Precompressed cork fitted into the joint after the concrete hardens,

may give better results. The sample of rubber bound cork gave results similar to

those cf the res in bound corks, except that it was affected by more exposure to

light.

6. The sample of extruded rubber gave extension values from 0.11 to 0.23-

inch. Protection from sunlight is recommended.

7. The bituminous materials intended for hot application gave high extension

values when warm , but at cooler temperatures these values were rather low. At

12°P, the highest extension value was 0. OS-inch.

8. most samples of plastic bitumens usually gave ample extension values

at both high and low temperatures, but in the weather exposure, cycle, and weather one ter tests, the performance of some were not very satisfactory. Better

durability may be expected from such materials where they are protected from

sunlight

.

9. 'The sample of rubber and asphalt composition gave s t is factory extension values in all tests and was little affected by light exposures. Special

precautions should be taken to prevent the material flowing from the joint.

10. The oil mastics gave somewlv t more consistent results than the bituminous mastics and seemed to deteriorate less when subject to light exposure

.

Better durability may be expected from such materials where the concrete is

treated with a suitable primer.

11. Sheet metal joints are considered the most suitable type for roof

construction, but the designs used in concrete roads could be modified to give

lOxiger service in roofs.

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