TECHUICAL lUFORiaTION ON BUILDING MJLTERIA13

TIBI/I- 56

FOR USE -IN THE DESIGN OF LOT7-COST HOUSING

THE NATIONAL BUREAU OF STANDARDS

URTIIED STATEE DEPARTMENT OF COMMERCE

WASHINGTON, D. 0.

DecemLer 2, 193 7

PLASTIC CAULKING AND POINTING MATERIALS

Part II

I nve sti^aticns

A discussion of the corrmosition, uses, and service requirements

of ulastic caulking and uointing materials anpears in TIBM- 24, as issued in August, 1936. Since that time additional studies have "been

made under the direction of D. W. Hessler on the performance of various proprietary materials in actual service, in exposure tests, and

"by laboratory tests. In this work particular attention was given to

determining the reliability of laboratory tests as an indication of

service value. The laboratory methods used in testing samples for

numerous government buildings have been described in a paper entitled,

"A Test Procedure for Plastic Caulking Materials" , uublishec’ in the

PrcceC'dings of the American Societv for Testing Materials, Vol. 33.

Part II, uage 521. 1935* A brief suramarv of the results of such tests

on 15 brands of the more widely used caulking materials is given in

the following table:

1
SUMMARY OF TEST RESULTS FOR

FIVE SUOCESSIVE YEARS*

1 932 1 ^33 1 954 1 935 1 936

Brand NO. TESTED

PERCENT

PASSING

NO. TESTED

percent

PASS 1 NG

NO. testedPERCENT

PASS 1 NG

NO. TESTED

PERCENT

PASS 1 NG

NO. TESTED

PERCENT

PASSING

PASS 1 NG

AVERAGE

A 3 100 2 100 1 100 8 87 9 67

(percent'

91

B 0 0 9 78 3 67 2 50 1 100 74

C 9 67 12 67 6 83 10 60 20 45 64

D 10 60 13 23 10 60 20 55 18 67 53

E 42 8 1 44 75 31 29 32 44 18 28 5 1

F 6 17 19 32 5 80 40 52 41 68 50

g 32 12 30 87 18 61 27 41 43 35 47

H 17 7 1 12 25 3 67 19 16 28 36 43

1 19 32 13 54 4 25 8 63 7 30 4 1

J 8 63 10 70 8 25 3 33 4 4 38

K 3 0 13 31 7 7 1 3 67 6 17 37

L 2 0 8 25 4 50 7 0 12 50 25

M 4 50 6 53 4- 0 21 19 13 15 23

N 5 80 3 0 4 0 3 0 1 0 16

0 19 10 13 15 6 0 16 13 20 10 10

*|N THIS rating, samples SHOWING ONLY A SLIGHT

stain on marble or slight slumping IN A LIMESTONE GROOVE WERE CONS 1 DERED AS . passing these tests.

2
Th5 large n'urn'ber of faili:res shown for most "brands indicate that factory nrocesses are not usually controlled sufficiently to insure uniform ner- formance. Hence, it is not logical to specify such m.aterials "by "brand alone.

Unsystematic fluctuations in most "brands suggest that different consignments

of raw materials may vary sufficiently to account for the lack of uniformi'ey

in the finished products. Certain phases of the investigation have nrogres^ed

sufficiently to give results of interest. These are descri"bed as follows:

EXPOSURE TE STS

Limestone Staining Test Sue cimen s; These studies were made urimarily

for the purpose of determining whether test methods give accurate indications

of service values, and. whether simpler tests can "be employed. Specimens used

for slump and staining tests on all sanroles tested during the past six years

have heen exposed to the weather for o"bser vat ions. A"bout 2000 of these are now "being studied. Specim.ens showing shrinkage or cra.cking sufficient to indicate that the Joint is no longer waterti^t, are rated as failing, and the

exposure period noted. This method of rating has its shortcomings: first,

"because one cannot always "be sure of the watertightness of a Joint from ex- ternal appearances; and second, a Joint free from stresses or movements gives

too little information on what the materials might do if su"bjected to strain, as in actual service.

Several of these specimens were tested with water to determine the dependa"bility of the visual rating, and the indications were that a"bout 75/^ of

these ratings were correct. It was found that Joints sometimes aoueared to

"be faulty on account of senaration of the caulking from the stone near the

exposed face when they were still in good condition at a greater depth. After testing these Joints with water at room temperatures, they were nut in

storage for a few hours at 32° E, tested, then chilled overnight at lO'^E,.

and again tested. The 'results showed only one of twenty- three specimens with

an increased leakage at the lower temperatures.

Visual ratings on ?33 snecimens, compared with results of the usual

tests, seem to show that the strain test and staining test on limestone give

indications of service values, A suimmary of these studies is given as follows:

(1) Samples passing the strain test and showing a di:ra"bility of more

than three years =

(2) Samples failing on the strain test "but showing a dura"bility of more

than three years :: 20

(3) Samples failing on strain test and staining limestone, "but showing

a dura"bility of more than three years = Si).

In computing the results under (3) "both primmed and unprimed Joints of

each sample were considered, i.e., if either the primed or unprimed Joints

indicated a dura"bility of three years, the sample was counted as one giving

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better service than the usnal tests would predict.

Since a large percentage of the sneciraens are apnarently still in good

condition, it is not .nossihle to reach definite conclusions concerning the

relation between the . usual, laboratory tests and durability. Trom the analysis, of 538 exposure specimens, it annears that 8 ^ of the materials rejected by the strain test and staining test on limestone would give reasonably

good service in joints where the caulking material is not subjected to strain.

The strain test is a measure of adhesiveness as well as extensibility.

The staining test determines the resistance of the caulking to loss of oil

by capillary suction of the masonry. In general, it may be said that loss

of oil, reduces the ulasticity of the caulking material in nroportion to the

amount of oil lost. . Adhesiveness and cohesiveness may likewise be affected;

hence, the two tests- are related. The staining test on marble often causes rejections of samnles which pass all other tests. However, a sample may

cause a large amount of staining on marble without causing much change in

plasticity. This result is attributable t'' the low pore space in marble, since a small amount of oil will fill the uores of a considerable volume

of marble.

Twelve percent of the samples failed to pass a copper corrosion test,

but of this number Pl"^ would have been rejected by failing to nass one or more of the other tests. Of the number rejected by the copper test alone

(less than 2 ^. of the total) nearly 60'^ shewed satisfactory durability values.

Trcm the foregoing, it would seem that both the staining test on marble

and the copper corrosion test could be dispensed with so far as quality

tests are concerned. There caulking is to be used on marble the staining

test should be made, since oil stains on marble are unsightly and difficult • to remove.

The copper corrosion test might be of value in cases where facilities

are not available for making the strain test, because samples that fail on copper usually fail on the strain test. Since many samples pass the copper

test, and still do not have proner bonding nroperties, plasticity, or cohesiveness, it is not logical to renlace the strain test by the couper corrosion test.

Strain Test Specimens ; As the above described exoosure tests gave no information on how well the caulking materials adjust themselves, to structural m.cvements, test's were initiated about two years ago in which strain

test specimens are being exnosed to the weather. These tests include limestone, marble , slate , and five grades of brick. Groove joints are included

in these exoosures with the caulking in contact with concrete, steel, and

wood.

In this part of the research, strain tests are made on specimens afterstanding thirty days in the laboratory, and after weather exposure of thirty

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1
days, and one year, respectively. The insnfficient nurnher of these tests

completed does not- justify conclusions, hut certain statements in regard to

apparent trends may he of interest.

Tests on limestone generall37- showed no differences between results for

specimens stored thirty days in the laboratory, and those exposed to the

weather for the same length of time. But, for specimens exposed one year,

the performance was, in most cases, less satisfactory. Theories have been

advanced that caulking materials perform more satisfac torily and are more

durable on dense masonry materials than on the more norous varieties. These

tests do not confirm that belief throughout, although the results on marble

and slate are, in most cases, better than those on limestone. The tests on brick, however, seem, to indicate that norosity may not be very inroortant be- cause several excellent results on joints between bricks were obtained where

the absorption of the brick was two or even three times that of the limestone.

Since no appreciable oil penetration into the bricks was noticeable, it is

assumed that lower capillary suction in brick m.ay account for the differences

in performance.

Oil and Volatile Matter Losses: Shrinkage of the caulking materials in

contact with masonry materials usually occurs and is believed to be mainly/’

the result of oil loss. Since most of the materials contain some volatile

oils, this loss also contributes to shrinkage. Such shrinkage ca,uses reduction of plasticity and hence, reduces the effectiveness of the mass.

Measurements of oil and volatile matter losses have been made on various

samples of caulking materials to determine their quality. Such determinations are being made in conjunction with exposure tests. If a sufficient degree of correlation is found, it may be possible to simplify test methods and

reduce the time of testing.

Inspections ; Several buildings were insnected during 1936-1937. for the

nurnose of determdning the performance of plastic caulking materials in

actual service. Examinations were usually made from the exterior, and in

some cases it was not possible to view the materials at close range. Statements in regard to the condition of materials may not alwa.vs do them justice,

or faults may be overlooked at a distancd of several feet. Except for the

fact that caulking materials are shown under actual service conditions, and

in contact with a greater variety of other materials, it is believevd that the

information obtained by inspection was not as satisfactory as that obtained by

examining test specimens after exposure.

Where caulking materials are used around wood frames, they are nearly

always covered by the staff bead and hence, not visible.

I Summary ; The physical tests now in use have been described and a resume

of tests on samples from several of the larger producers is listed. Considering the variations of samples of any one producer which pass the test for

successive years, one may conclude thad. none of these products should be ac- cepted without testing, as dess ’than half of the samples of m.ost brands ac- tually pass the tests.

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A study of groove, joints, in limestone exposed to the weather for

periods of from three to six years has "been made, for the' purpose of gaining

some information on how well the laboratory tests nredict actual service

values. Although the means of judging the exoos-ure results is "by external'

appearance, which is not entirely .satisfactory, and the joints are not subject to appreciable deformations, as in service, it is believed that some information of value was obtained. These studies have indicated that the

tests now being used, do give valuable information on durability. It seem.s that certain tests are unduly severe in that they reject some materials

which would give good service. However, before any change is made it is desirable to gain more information on the behavior of weathered joints under

strain.

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