Studies of Stone-Setting Mortars

United States Department of Commerce

National Bureau of Standards

Building Materials and Structures Report 139
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UNITED STATES DEPARTiMENT OF COMMERCE • Sinclair Weeks, Secretary NATIONAL BUREAU OF STANDARDS • A. V. Astin, Dirtctor

Studies of Stone-Setting Mortars

Daniel W. Kessler and Ross E. Anderson

Building Materials and Structures Report 139

Issued November 23, 1953

For sale by the Superintendent of Documents, U. S. Government Printing Office Washington 25, D. C. - Price 20 cents
I

I

I
Forewoi^d

Stone masoniy structures sometimes exhibit defects such as spalHng at mortar joints, separation of mortar from stone in vertical joints, discoloration,

and efflorescence. These are often attributed to the mortar. To determine

the extent to which mortars are responsible for undesired performance in stone masomy and to serve as a guide in the selection of suitable mortars, laboratory

tests on several types applied to the more common varieties of building stone were conducted. This report covers the results of these tests and includes a discussion of the relation of various properties of mortar to its performance.

A. Y. AsTix, Director.
Contents

Page- Foreword III

1. Introduction 1 2. Materials 1 2.1. Mortar ingredients 1 2.2. Mortars 2

2.3. Stones used in bond tests 3

3. Bond tests 3

3.1. Specimens : 3

3.2. Apparatus and procedure 4

3.3. Results and discussion 4

4. Linear dimensional changes 11

4.1. iNIortar specimens 11

4.2. Apparatus and test procedure II

4.3. Results of tests 11

5. Volume shrinkage 13

5.1. Mortars and specimens 13

5.2. Test procedure 13

5.3. Results of tests 13

6. Discussion of volume changes 14

7. Resistance to freezing and thawing 17

7.1. Specimens and test procedure 17

7.2. Results of tests 17

7.3. Discussion of results 17

8. Effect of different curing conditions 17

9. Relation of mortar to performance of masonry 18

9.1. Spalling of stone at mortar joints 18

9.2. Ejfflorescence and discoloration 19

9.3. Calcareous vein formations 19

9.4. Shrinkage cracks 21

9.5. Surface scaling 21

10. Summary and conclusions 22

11. References , 23.
Studies of Stone-Setting Mortars

Daniel W. Kessler and Ross E. Anderson

Several mortars were studied for bonding strengths to four types of stone, dimensional

changes under three conditions of storage, and frost resistance. Higher bonding strength was obtained for mortars to fine-grained stones than to coarse-grained stones. Indications were found that mortars shrink more in a vertical direction than horizontally. If shrinkage

cracks form in the specimen, the measurements will be too low. Tests on mortars cast and

cured in contact with porous materials gave higher strengths and lower absorptions than were

obtained on specimens cured in nonabsorptive molds. Ground limestone was found to be a

satisfactory plasticizing agent. Some studies were made of mortars in structures and certain recommendations are made for selecting mortars for use in stone masonry.

1. Introduction

\Vlien the stone-exposure test wall ^ was being

planned, considerable thought was given to the

selection of mortars. One objective was to study

discolorations on stone with respect to type of

setting mortar. Since lime mortars and portlandcement mortars were under consideration, it was decided to set one-half of the wall in straight

lime mortar and the other half in portlandcement mortar with ground limestone as a plasticizer. Little information was available on the

performance of mortars containing ground limestone, and it was decided to make a study of

j such mixtures in comparison with mixtures without

i limestone.

' Observations on the performance of materials

in structures have indicated some of the troubles

in stone masonry are: (1) Bond failure, especially

in vertical joints; (2) spalling of the stone at the

joints; (3) discolorations of the stone; (4) crack

formations due to calcareous growths starting

where lime solutions evaporate through small

openings.

As pointed out by Pearson [1],^ there are many

properties of mortars which are important, but

the writers considered that bonding strength,

shrmkage, and durability were of most concern. There is little published information on bonding

strength of mortars to stone, and most of the

studies on shrinkage have been confined to linear

changes that occur after the mortars have set. The curing conditions in masonry are considerably

different from those commonly used in the laboratory so a few comparisons of test results for

I both conditions of curing were made.

Such considerations led to a series of experiments to develop data on the following points:

(1) The bonding strength of various mortars to the more common types of stone; (2) comparison

of the bonding strength of mortars in specimens

made to simulate the conditions in horizontal

1 National Bureau of Standards Building Materials and Structures Report BMS 125.

2 Figures in brackets indicate the literature references at the end of this paper.

and vertical joints; (3) the relative merits of two plasticizing agents, hydrated lime and ground

limestone; (4) the physical properties of mortars

cured under conditions similar to those in masonry

as compared to those cured under standard

laboratory conditions; (5) the total shrinkage of

mortars in contact with porous materials; (6)

the extent of volume changes in mortars under

various conditions; (7) the frost resistance of

various mCrtar mixtures.

Published data on shrinkage of cement products

show a wide range in results obtained by different

investigators for similar mixtures and results obtained in this study were considerably higher

than many vahies previously reported. Carlson [2] has developed a theory of the mechanics of early

shrinkage, which may explain some of the variable

results. According to his theory, shrinkage

cracks form in the cement paste surrounding

aggregate particles because the compressibility

of the particles is less than the shrinkage of the

paste. Such shrinkage is not determined by the

usual measurements because it does not change the

overall dimensions of specimens. Some experiments were made on clay specimens to demonstrate the effect of pronounced cracking on shrinkage measurements.

Shrinkage measurements were made under

conditions that were intended to give some

indication of the total contractions that may occur

in masomy joints and hence the results are considerably higher than many reported for the usual

laboratory storage conditions. It is doubtful

if these results are as high as actual shrinkages

that occur in vertical joints, filled by pouring in a grout, as is frequently done in setting large

ashlar blocks.

2. Materials

2.1. Mortar Ingredients

Seven brands of portland cement, including 5 gray and 2 white cements, 2 masonry cements, 1 natural cement, and a high-calcium hydrated lime were used in various mortars. Ground limestone

1
passing a No. 100 sieve was used in a few mixtures

as a plasticizer. In most mixes, Potomac River

sand passing a No. 8 sieve was used. Percentages

retained on the Nos. 16, 30, 50, and 100 sieves were 12, 20, 49, and 95, respectively. In one group of bond test specimens, crushed marble

graded between sieves Nos. 20 and 100 was used,

and the silica sand, described in section 8, was

used in a few mortars for experiments on different

curing conditions.

In the tables and graphs the cements are designated by letters which are included in statements

of proportions of the mortars. The various ce- ments are designated as follows: Portland cements. Brands: A, port land, type I; B, white Portland, regular; C, white portland, air entraining; D, portland, type I; E, portland, type

II; F, portland, type II; G, portland, type I. Masonry cements. Brands: H, buff masomy

with water repellant; I, portland with limestone

addition.

Natural cement. Brand: J, dark gray natural.

For hydrated lime and ground limestone, the

symbols (HL) and (Ls) have been used, respectively, to designate these admixtures.

2.2. Mortars

The mortars used in various tests are listed in

table 1. The mortar ingredients were proportioned by

volume on the basis of the following weights per

cubic foot: portland cement, 94 lb; masonry ce- ment, 70 lb; natural cement, 80 lb; hydrated lime,

40 lb; ground limestone, 80 lb; silica sand, 97 lb; and crushed marble, 92 lb. The amount of water

for each mix was determined bv flow-table tests (ASTM C230-49T). A flow of 120 was judged

to be similar to that commonly used by stone

setters and this flow was used for all mixtures.

The water-cement ratios of the mortars are shown

in table 1. The specimens for compressive strength, absorption, and bulk density were 2-in. cubes made

and cured 28 days in accordance with ASTM

designation C91-44.

Table 1. Mortar designations and test values

Designations

Proportions by volume W/C 2 by

weight

Test values ^

Mortar No. Cement

brand ' Compressive

strength

.Absorption

48 hr by

weight Bulk density

1:3 cement-sand mi.xtures

1 A

B

CD

E

FH

IJ

1(A) :3 0.65

.66 .63

.59 .66

.66 .86

.63 .78

psi % glcm '

2 _ 3 1(B):3 1(C);3

4. 080 9.7 1.96

4 1(D):3

5

6

78

9

1(E):3

1(F):3 1(H):3

1(I):3.-. 1(J):3

2, 960 3,370 380

1, 150

120

7.6

9.3 12.7

11.7 13.6

2.02

1.98

1.66

1. 77

1.68

Cement, lime, and sand mixtmes

10 A

B

C

FG

E

F

FF

1(A):0.1(HL):3 0.60

.69

.67

.67

.67

. 71

. 71 .74

.79

1112.. _ _. 1314

15

16

17

18

1(B):0.1(HL):3

1(C):0.1(HL):3

1(F):0.1(HL):3 1(G):0.1(HL):3

1(E):0.4(HL):3

1(F):0.4(HL):3 1(F):0.5(HL):3 1(F):1(HL):3

4, 260 3.500

3,530

3, 690

4, 760 3,840

3. 820

9.6

8. 7

9. 2 9.8

9.3 9.6

8.5

1.96

1.91 1.98

1.89

1.99

1.97

1.96

Cement, ground-limestone, and sand mixtures

19

20 F

F

FF

l(F):0.5(Ls):3

l(F):0.6(Ls):2.4 0.70

. 60 .70

. 69

4.420 8.8 2.00

21 l(F):1.2{Ls):2:4 22 l(F):2(Ls):2 4, 380 9.1 1.98

Portland and masonry or natural-cement mixture

23. D&H

E&H

F&H

F&J G&J

l(D):l(H):6 0. 65

. 70

. 73 .69

.65

24 1(E):1(H):6 _ 2526

27

1(F):1(H):6

1(F):1(J):6 l(G):l(J):6

1, 600 1.460

11.3

10. 6 1.761. 81

' The cements are described in section 2.2. s Two-inch cubes were made and tested for compression in aciordance with

2 The ratios of weights or water to cement, termed W/C, were based on the .\STM Designation C91-44T. .Absorption and bulk density were deter- weights of Portland, masonry, or natural cement used in the various mixtures. mined in accordance with .ASTM Designation C97-47. When 2 cements were used in 1 mortar the value of C was the sum of the 2 weights.

2
2.3. Stones Used in Bond Tests

In making bond test specimens, the four types

of natural stone listed in table 2 were used in slab form as follows: Limestone from Rockwood,

Ala. ; sandstone from Amherst, Ohio ; marble from

Danby, Vt.; granite from three sources. The limestone was of the oolitic variety, of medium texture, and contained about 98 percent

of calcium carbonate. The sandstone was of medium texture, rather high porosity, and contained

approximate!}' 97 percent of silica. The marble was of medium texture and was typical of the

white building grades. Its composition was about

99 percent of calcite. The granites varied from

medium to coarse and all were of the biotite

variety. It should be noted that textures in the

different types of stone are relative to each other

only within a particular type. For instance,

medium-textured gi'anites are much coarser grained

than medium-textured marbles, sandstones, and

limestones. The range in gi-ain sizes for the

stones used was appi-oximately as follows: Limestone, 0.25 to 1 mm; sandstone, 0.1 to ().!) mm;

marble, 0.2 to 0.6 mm; and gi'anites, ] to 10 mm.

Tlie surface finish on the limestone, sandstone,

and marble was the same, and was obtained by

grinding with No. 60 abrasive grain. This gave

practically the same finish as that called sandrubbed finish in the stone trade. The surfaces on the granite slabs vai'ied fi-om fine pointed to coarse hammered. These surfaces were on the

])locks when received from finishing phmts and

were l)elieved to be more typical of bed-joint

faces commonly used in granite ashlar masoniy

than could have been obtained by grinding. In

all cases, the two granite slabs forming one bond

specimen were cut from the same block and had

tlie same kind of finish in contact with the mortar.

Physical properties of the various stones used

in making bond test specimens are shown in

table 2.

TabIjE 2. Physical properties of stones used in bond tests

Stone Type Compressive

strength Modulus o! rupture

Tensile

strength

Absorption

48 hr by

weight

Initial rate of absorption i Unit weight

1 Limestone

psi 7.400

8, 600

12, 200

24, 900

20, 500

19, 000

psi

1, 020

psi 360 %

4.7

5.8

0. 10 .29

. 14

. 10

g/niin 9.8

18.0

0.2

.3.3

.3

145

135

170 164

169

167

2 Sandstone ...

3 Marble 1,550 700

4 Granite . 5 _ do

6 do

' Grams of water absorbed in 1 min when a 30-in.2 face of a dry .specimen is standing in water to a depth of W in., ASTM Designation C67-44.

3. Bond Tests

3,1. Specimens

Bond test specimens were made with }i-'m.

Ijmortar joints between slabs of stone. The stone

'slabs were 4 by 6 in. on the face, and thicknesses

varied from 1 to 2 in. Before the joints were made

the stone slabs were soaked in water for 30 min,

freed of surface water, and dried in air for 10

min. The joints were made in a special rack

shown in figure 1 . In making specimens to simulate the conditions in horizontal joints, the lower

slab was first clamped as shown in the lower part

of figure I. A square metal rim 4 by 4 in. inside

and /8 in. deep was centered over the lower stone

Fkiure 1. Rack used in preparing bond lest speci mens.

3
and filled level full of mortar. The rim was then

removed, after which the top slab was centered

above, in crossed position, and forced down until

it came in contact with two metal strips on the

rack, which gaged the joint thickness to in. Specimens made to simulate vertical masonry

joints were made in another part of the rack shown

in the upper portion of figure 1. On one slab

four K-in. metal cubes were sealed for thickness

spacers and also to prevent the slabs from being

drawn together by sln-inkage of the mortar. Tavo

slabs were clamped together on the spacers in the

position shown. The lower edge and two sides were closed by wooden strips coated with grease on the joint faces. As a precautionary measure,

these slabs were fastened together with very

strong rubber bands that were left on until the

specimens were stored. The mortar in the vertical joints was tamped in tlu'ee layers with a metal

bar }i in. thick. Specimens for comparing the

strength in horizontal and vertical joints were made in groups of six, all from one batch of mortar.

Specimens for comparing the strength in the two

types of joints were made mostly of limestone but

a few were of sandstone and marble. As soon as a group was completed (about 30 min) the speci- mens were undamped from the rack and placed on shelves in a room in which the temperature

varied from 68° to 72° F and relative humidity

from 45 to 65 percent.

At ages of 1, 5, 11, 18, and 25 days, the speci- mens were immersed for 15 min in water. Strength tests were made at 28 days.

3.2, Apparatus and Procedure

Tests were made with a hand-operated apparatus which consisted of a loading device shown in

figure 2, and a pendulum-type scale with a capacity of 1,400 lb and a sensitivity of 1 lb at all loads. Specimens were supported on knife edges

of the rocker type and the supporting edges made

contact with the ends of the stone slabs about K

in. from the edges of the joints. A special tool was made for transmitting the loads. This consisted of two metal edges 4% in. apart, rigidly

attached to a connector as shown. Between the

tool and the loading mechanism was a spherical seat for accurate adjustment. Loads were applied at a rate of approximately 100 Ib/min.

3.3. Results and Discussion

The results of bond tests are shown in tables 3

to 6, along with results of compression tests, absorption, and bidk density determinations on

mortar cubes. Figures 3, 4, 5, and 6 show various

types of breaks. In these figures the letters L,

S, M, and G, denote limestone, sandstone, marble,

and granite, respectively. Numerals following

these letters denote different specimens, the slab

Figure 2. Hand-operated machine used in determining

bonding strength of mortars to stone.

with the mark being one part and that directly

above, its companion. It will be noted in some

cases, that the mortar pulled out numerous par- ' tides of stone and in one sandstone specimen

(S4, fig. 4) the break was entirely in the stone. In some instances the ends of the stone slabs were | broken off before the bond failed. The data in

tables 3 to 6 show the average bonding strengths

for groups, usually of three specimens. When one

or more specimens of a group failed by breakage

of the stone before the bond was ruptured, the

averages for such groups were obtained by using

the highest bonding stress developed in the speci- mens that did not break the bond, along with the

actual bond value of the remaining specimens.

Such averages are somewhat lower than the actual

bonding value. A few specimens failed by breaking partly or entirely in the mortar due to the

tensile strength of the mortar being lower than the

bonding strength. This type of failure is shown

in figure 3 by specimen 12.

1

i
I'iGURK o. Li incstoiie bond speci^nens after test showing types of failures. Each numbered slab and the one immediately above formed the original test specimen.

258566—53 2 5

Figure 5. Marble bond specimens after test showing types of failures. Each numbered slab and the one immediately above formed the original specimen.

Table 3. Remilts of teds on morlar.s for hondimj slrcruilh to iimfislone

Mortar No.

13. 13.

16.

16.

17.

17.

11.

11. U.

14.

14.. 12. 12.

12.

16.

16.

19. 19.

19. 22.

22.

25..

25..

26..

26..

Mortar mi.xtures

Dry ingredients

1(F):3do

do

1(B):3do

do

1(I):3do

1(H) :3 do

1(J):3do... 1(F):0.1(HL):3. do

1(F):0.4(HL):3. do

1(F):0.5(HL):3. do

1(B):0.1(HL):3. do

do

1(G):0.1(HL):3. do

1(C):0.1(HL):3. do

do

1(F):0.4(HL):3. do

l{F):0.5(Ls):3.. do. do

l(F):2(Ls):2.... do

1(F):1(H):6....

do..

1(F):1(J):6 ..-.do

W/C I

0. 66

.66

.66

.66 .66

.66

.63

.78

.78

.67

.67

.71 .71

.74 .74

.69

.69 .69

.67

.67

.67 .67

.67

.71

.71 .70

.70

.70

Bond tests on limestone

Type of

joint 2

H

VH

H

V

H

H

V

H

V

H

VH

V

H

V

H

V

H

V

H

H

V

H

V

H

H

V

H

VH

H

V

H

V

H

V

Average

tensile strength

psi

60

36

70

52

36

58

33

33

27

27

2122

47

515654

7270

6038

5038

50

62

4167

69

66

47

5162

7145

3129

36

30

Type of break for specimen 3

alO....

a2, bl.

al, bl. b2

bl4....

bl4.... a3a5

al2.... a5

al6..-. al5

a7, b7.

al2 a2

a3, bl-.

alO, 2b.

a4, bl..

a4

al4 al2

a2

all a3

ea5

a2

a3, b2--

a3, b3..

al, b2-

.

al2.... a5

all....

al, b2.

al, bl.

blbl4

bl3

a5a5

alO

a5, blO.

0al5 a8

a2

a4..

a5.. al5.

0... a5..

a2.. al2.

a3

al, b2.

al, bl.

a4, bias

all....

al, bl.

al, b2.

bl.. bl3. bl3.

a3... a4... c

al4. al5.

a3..

alO.

al.. a4..

a6, b2.

c

all.

al..

a4

al

al, b2.

Tests on mortar cubes

Compressive

strength

psi

3,700

4,080

1, 150

380

120

3, 650

4, 090

3, 820

4,260

3, 690

3, 500

3,880

4, 420

4, 380

1,600

1, 470

Absorption

48 hr by

weight

%

9.9

9.7

11.7

12.7

13.6

9.8

10.0

8.5

9.6

11.3

10.9

Bulk

density

g/cm 3

1.97

1.96

1.77

1.66

1. 68

1. 96

1.95

1. 96

1. 96

1.89

1.91

2. 00

2. 00

1.98

1.76

1. 78

1 Water-cement weight ratio.

2 H signifies horizontal joint; V, vertical joint.

3 Types of failures in the bond tests: "a" signifies that part of the stone was

pulled out by the mortar as in figure 5, M^ and M<; "b" sit;nifics failure of

jthe mortar in tension as in figures 3 and 12; "c" signifies ooiiipli'tc failure of

[the stone as in figure 4, S', or by breaking ends of slabs. Numerals following khe letters "a" or "b" denote the number of square inches of failm e of the type

designated by the letters. When one or more specimens of a group failed without breaking the bond, the average values in the table were obtained by using the highest bonding stress developed by such specimens and are somewhat lower than the actual bond strength. When no notes are made

on the type of failure, it w ill be understood that the breaks in that group of specimens were entirely bond failures.

Table 4. Results of tests on mortars for bond to sandstone

Mortar No.

Mortar mixtures Bond tests on sandstone Tests on mortar cubes

Dry ingredients W/C Type of joint

Average

tensile strength

Type of break for specimens ' Compressive strength

Absorption 48 hr by weight

Bulk

density

1 2 3

6 1(F):3 0.66

.67

.67

. 71 .69

H

H

V

H

H

psi

76

66

70

6352

a5 . c3 a3. .. psi3, 300

3, 580

"i'.Yoo"

1,390

%

8.8

8.8

g/cm 3

2. 00

13 1(F):0.1(HL):3 c. c c . . 1.99

13 do

16.. 1(F):0,4(HL):3 aiO-^-'--" c... . ... allV.l'."'/. 9.7

10.4

1. 96

26 1(F):1(J):6 a4 a4 a3 1.84

footnote 3 of table 1. Table 5. Results of tests on mortars for bond to marble

Mortar No.

Mortar mixtures Bond tests on marble Tests on mortar cubes

Dry ingredients W/C Type of joint

Average

tensile strength

Type of break for specimens ' Compres-

.sive strength

Absorption 48 hr by weight

Bulk

density

1 2 3

6 UF):3 0. 66

.67

.67

. 71 .69

H

H

V

H

H

psi

5570

666540

c a4. C-. .. psi 3,310

3,510 "3, 880

"

1,300

%

8.8

8.9

g/cm^

2.00

13 1(F):0.1(HL);3 a7 - alO c. 2.00

13 do a8 alO alO

16 1(F):0.4(HL):3 c c... . .. al3 8.9

10.8

2. 00 26 l(F):l(J):6 al al al. 1.80

1 See footnote 3 of table 1.

9
Table 6. Results of tests on mortars for bond to granite

Mortar No.

Mortar mixtures Bond tests on granite Tests on mortar cubes

Dry ingredients W/C Type of joint

Average

tensile strength

Type of break for specimens ' Compressive strength

Absorption 48 hr by weight Bulk

density

1 2 3

6 1(F):3 0. f6

.67

.71 .69

H

H

H

H

PS! 4133

5220

psi 3,180

3, 400 3.700

1,700

%

9.6

9.2

9. 7 10.2

(/Icm 3 1.96 1.97

1.96

1.87

1.3 1(F):0.1(HL):3

IR 1(F):0.4(HL):3 al 26 1(F):1(.I):6

' See footnote 3 of table 1.

When stone particles over a considerable area

are pulled out by the mortar, one might assume

that the tensile strength of the stone was lower

than the bonding value of the mortar. Tests on

marble and limestone, however, show that their

tensile values are several times higher than any of

the stresses developed in these tests. It seems more likely that some of the stone particles were

loosened in cutting, or by some unknown physical

action at the interface.

The various types of breaks that occurred in

the bond tests are described in tables 3 to 6 by means of symbols and footnotes. These may be

used to evaluate the averages in column 4. Although the number of tests on sandstone,

marble, and granite is pi-obably too limited to justify definite conclusions in regard to comparative bond strengths, there are enough results to indicate that the strength of bond to granite is lower than that of the other three types. This is surprising in view of the fact that the surfaces of

the granite blocks were comparatively rough.

The bond between mortars and sandstone or marble appears to be considerably higher than for limestone. Such results camiot be ascribed to porosity or rates of absorption of the stones. Studies by Palmer and Parsons [3] on bonding

3 The data presented by Palmer and Parsons [3] have been considered as proving that brick units of very low rates of absorption (1 g or less per min)

givi' n'latively low strength of bond in tension in brick-mortar assemblages

con]|ian'(l with brick of 22 g rate of absorption. Field observations and

subsi;'<iuent tests have caused these relations to be questioned. The following tabulation of heretofore unpublished data has been made iiv:iiliible through

the courtesy of .T. W. McBurney: These data represent 'tiniLili nf bond of brick-mortar assemblages in tension (crossed brick) ami in ^hi ;ir (3-brick assemblages) laid in l:i:3 cement-lime-sand mortar. In these tests the

bricks were placed on the bed joints within 10 sec of spreading the (bed)

joints. Each value tor strength of bond in tension or in shear is the average

of 14 tests made at the age of 28 days.

Initial rate Average Average

Brick Xo. of absorp- tensile shearing

tion strength strength

Olmin psi psi

1 Q.5 78 305

2 2.0 297

3 8.0 107 303

6 21 27 126

7 23 42 184

8 33 60 178

9 33 33 140

strength of mortars to brick indicate that bricks

absorbing about 20 g of water per min when laid

flat (4- by 8-in. face) in }i in. of water give higher

bonding strengths than bricks of either higher or lower absorption rates. ^ The absorption values of

the stones used in these tests determined on the same basis were as follows: Limestone, 9.8; sandstone, 18; marble, 0.2; and granite, 0.3 g. There

seems to be some correlation between grain size

and bonding strength in that the finest-grained

materials showed high values and the coarse- grained materials, low values. This might be

interpreted to mean that the highest bond is along

the grain boundaries.

Because of the uncontrollable variables mentioned above, it is impossible to reach definite

conclusions from this limited series of tests in

regard to mortars. Because there is little available information on bonding strength of mortars

to stone, a few tentative statements based on the

results obtained from the limestone specimens

may be desirable.

Two 1 : 3 mixtures of portland cement and sand

gave considerably less bonding strength in vertical

joints than in horizontal joints, whereas three

similar mixtures gave practically the same bonding strength in both types of joints. In four

Certain of these tests in tension were repeated with the difference that

the time of placing the second brick on the mortar joint was delayed for 30,

60, and 120 seconds, respectively. The results were as follows:

Brick No.

Initial rate of absorption

Strength of bond in tension

10 sec 30 sec 60 sec 120 sec

qjmin psi psi psi psi

1 0.5 78 89 78 89

3 8.0 107 71 70 78 9 33 33 57 34 *6

* Two out of 7 assemblages had zero bond. Note that brick 3 was lowered from 107 to 71 psi by the 30-sec delay in

laying. Variations in brick 1 for all tests and brick 3 for all except the 10-see time are not considered significant. Brick 9 withstood delay up to 1 min,

but a 2-mm delay practically destroyed the bond. The data in general confirm the conclusion that good bond strength can be obtained from units of very low rates of absorption.

10
mortars (Nos. 11, 12, 13, 14) containing a small

addition of hydrated lime, the bonding values were variable with two showing lower strength in the vertical joints. All mixtures containing addi-

' tions of 0.4 or 0.5 part of either the lime or ground

; limestone gave practicall}? the same strength in

both types of joints. The unusual mixture 1:2

(Ls):2 gave remarkably high bonding strength

in the horizontal joints but was considerably

weaker in the vertical joints. Masonry cements

and the natural cement showed relatively low

bonding strength, and in some specimens the

' mortars broke in tension. Half-and-half mixtures

of masonry cements with portland cement in 1:3

. mortars showed only slightly higher bonding

strength than when only the masonry cements

were used in such mixtures.

It can be inferred from these results that mortars

appearing to have good working qualities are more reliable in vertical joints than are the straight

portland-cement mortars. The mortars should

not stiffen so rapidly that it cannot adjust itself

; to the early shrinkage horizontally.

4. Linear Dimensional Changes

ij 4.1. Mortar Specimens

; The mortars used for determining linear changes

I are listed in table 1 and also in figure 7.

: One specimen 24 by 4 by 2.5 in. deep was made

of each mixture. The batches were too large to be

mixed strictly in accordance with ASTM Method

C91-44 so they were divided into two equal parts,

and mixed simidtaneously by two men. After the

' specified manipulation the two parts were comI bined and worked for 1 min more by one man.

I The mold consisted of a metal rim and a plaster

I of paris base. The base slab was 2 in. longer and

2 in. wider than the metal part. The metal rim

ij had hinges on two sides so it could be removed

without damaging the specimen. On one side of the rim were two notches that served as a guide

for a device used in setting the reference pins in

^ the mortar while plastic.

|l Before the mixture was placed in the mold, one

{ thickness of blotting paper was dipped in water,

|i freed of excess water by shaking, and laid on the

plaster slab. The metal rim of the mold was

I then centered over the slab and blotter, after

which the mortar was scooped in, tamped in

three layers, and leveled. The same plaster slab was used for all specimens, but it had time to dry

i at least 2 days in the laboratory between specimens.

!j The reference plugs were cut into 1-in. lengths

il from a K-in. square brass bar. One end was then

j polished and marked with a cross; the other end

j: was pointed. Guide brackets with square holes

iat

one end were clamped into position and the

I reference plugs forced through the holes into the

! mortar. The tops of the plugs were left projecting slightly above the surface of the specimen.

4.2. Apparatus and Test Procedure

The measuring device consisted of two iiiicroiii- eter microscopes mounted 51 cm (20 in.) iipni t on

a horizontal shaft that could l)e rotated tlu'onali, an angle of 45 degrees, A graduated invar l)ar was mounted parallel to the shaft and fai- enough

forward to avoid interference with the line of

sight when taking readings on the plugs. The

microscopes were first focused on the scale of the

invar bar and the shaft then revolved until tiic plugs came into line. The reference marks were

then brought into focus with leveling screws und(>r

the specimen. The micrometers read to 1 micron,

and an experienced operator could (lu])]icate

readings to 2 or 3 microns.

The time required for filling the mold, setting

the plugs, and focusing required about 15 min.

The original length measurement was taken as soon as possible but the time varied from 15 to 20 min after the mixing was completed. The

length changed rapidly during the first 4 to 6 hr

and the readings were made frequently. Thereafter, the changes were small, and intervals

between readings were extended.

The temperature of the room during the investigation varied from 70° to 80° F and the relative

humidity from 20 to 80 percent. At the end of

24 hr the mold was removed and the specimen

kept moist by burlap dipping in water at either

side. Curing in this manner was continued for

28 days, except that it was necessary to remove

the burlap during periods of measurement.

At the end of the damp-curing period the speci- mens were carefully measured and transfei'red to dry storage in the same room. Readings were made at intervals over a period of 3 months during

dry storage, and then the specimens were immersed

nearly to the top face in water and measured

periodically.

4.3. Results of Tests

Length changes after the first 5 days in each

stoi'age condition were so small that the curves in

figure 7 were drawn only for the initial periods.

The maximum observed change for each test is stated on the graphs.

The basis for computing percentage changes

for damp curing was the original length between

reference points set in the plastic mortars about

15 min after mixing. The length at the end of

damp curing was used as the starting point for dry-storage measurements, and the length at the

end of dry storage was used as the starting point

for moisture-expansion measurement (table 7). It Avill be seen that the portland-cement mixtures (Nos. 1 , 2, 3, and 4) did most of their shrinking

in the first 6 hrs. Additions of lime or ground

limestone resulted in extending the period over which rapid shrinkage occurred, as well as result- ing in higher total shrinkage. A mortar in which

11
Moisture expansion Wai. during 7 doys^ rir<n 1 1

I —

.

1

Dry storoqe shrinkage _y

Mai.dunnq 90doys« 0.057%

Max

and don

during 3

p storot 2doyS'

e shrink 0,165%

Mi)(,l (A):OI }

Moisture e»ponsion '

' MOK during lldays=0 024%^

Dry storage slnrinkoge

' Max during 84dayS" 0.073%

Mix. l(D):| H):6

Setting ond domp storage shrinkage/' Mox. during 29doys= 0 126%

0.09

0. 10

O.OS

0

0.05

0. 10

Mix. I. (A): 3

Dry storage shrinkage Mox, during 87 days- 033% —1

1 1 1 hSetttng ond damp storoge shrinkage Mox during 29days = 0 124%

1

I

1 —

,

Moisture exponsion

Mox. during 7davs 0.038%

O

Dry storage shr Mcx durina 5Fnkoqe

davs. 0.050%

Setting ond do

Vlax in 3

np store 2doys«

ge shri 01 72%

^kage

Mix. KB): 3

Mix. 1(H) 3

Setting and damp storage shrinkog Mox during27days=C.I45% "\

1 I I Moisture exponsion Mox during I2days» 0.018%"' u 1 1 1

Dry storage s^rlnkoge

Max._during 84doys=0046%

Settint Ma during mp storo 26doys

ge shrin 0374oge

Mix.l(F):0.6(Ls):2.4

Moist Ma

ure exp(

. during 3 days10.009% An

Dry St Moorogfl sh

X during

rinkoge 57 days • 0080^ \-

V

Seltin Ma

1 and do

}Ldurin( mp storo 28days

ga shrirli 0 271

age

Mix.l G):l(J )-6

10 20 30 40 50 SO 70 80 90 100 110 ;20 Tims in hours the cementing material was a lialf-and-lialf mixtm-e of Portland and masonry cement (No. 23)

gave a lower total shrinkage than three of the

straight portland-cement mixtures, whereas a mixtme of portland and natural cements in similar

proportions (No. 27) showed a relatively high

o 0.05 ot 010

C»

« 0.15 o

o 0.20

1 1 1

Moisture exponsion

"

r^lox in8do^s= 0030%

Dry storage Mox during hnnkage 56doys. 0.050%

SetMing ond

ax. durirdomp stc g 30 do

rage si ;s» 0 2

rinkoge

O

Mix.l (C):3

ot;

VIox. dunno 84 days- O 044%

Setting and domp storoge shrinkoge qI p Max durgiq 31 doys- 0.153^ ,~

Moisture Moxdiexponsion ' ring 8 days- 0 02 2 %~^

!)ry stor Mox. ge shr

during 9

nkoge Odoys> 0.073% O— c

Selling Mox.d

ond don- uring 2

p storot rdoys-C

e shrink 165%oge

Mix.l (D):3 30 40 50 60 70 Time in hours

Figure 7. Curves showing 'percentage-length changes of mortars during first 5 days of damp curing, dry storage, and total immersion in water. The maximum changes that occurred during the periods of test under the

three conditions are shown in parentheses. The basis for computing per- centage changes for damp curing was the length between reference points

set in the plastic mortar about 15 min after mixing. The starting point

for dry-storage shrinkage was the length at the end of damp curing and

that for moisture expansion was the length at the end of dry storage.

total shrinkage. Mortar 3, in which an air- entraining cement was used, gave the highest

shrinkage of any of the straight portland-cement

mixtures. Two separate batches of mortar 4

showed considerable difference in total shrinkage.

Apparently some slight difference in the propor12
Table 7. Maximum shrinkage for two storage conditions and 7-day expansion in water Table 8, Shrinkage of mortars by volume method

Mortar

No.

1.2.

3.4_

4-10

23

7-20

27

2122

Mortar mixture

1(A):3 _ 1(B):3

1(C):3 1(D):3 1(D):3

1(A):0.1(HL):3..- 1(D):1(H):6

1(H):3

l(F):0.6(Ls):2.4... 1(G):1(J):6

l(F):1.2(Ls):2.4._. l(F):2(Ls):2

ShrinkageAfter 28 days of damp

curing %

0.124 .172

.227

. 153

. 165 .165 .126

.145

.374

.271 .402

After 90 days of dry

storage %

0.033

.050

.0.50 .044

.073 .057

.073

.092

.046

.080

.064

.048

Total

shrinkafter 4 months

%

0.157

.222

.277

. 197

.2.38 .222

. 199 .237 .420

. .351 .466

. 535

Expansion

after

7 days

in water

%

0. 026

.0.38 .030

.028 .022

.028

.024 .023

.018 .009

.029

.037

tions, manipulation, or surrounding conditions

during mixing and molding caused the different

performance because it became apparent during

the first few hours of the test.

5. Volume Shrinkage

5.1. Mortars and Specimens

Table 8 presents data on the total volume

change of various mortars with respect to their

initial volumes at the time they were molded.

Most of the mortar specimens were cast from the same batches used in making bars for linearshrinkage measurements.

The mold was made from a seamless brass tube

2.5-in. inside and 3.0-in. outside diameter. A

length of 2.75 in. was used, and this was turned

in a lathe to an inside diameter of 2.5 in. at one end and 2.75 in. at the other. The outside was

then turned to give a uniform thickness of the

sides of 0.04 in. The mold was made in this

shape to facilitate the removal of specimens.

The inner surface and ends were carefully gi'ound

with fine abrasives. The volume was obtained

by setting the mold, small end down, upon a ground-glass plate and filling it with distilled water. A second gi-ound-glass plate was used on

top to determine the amount of water needed for complete filling. The weight of water divided

by its density gave the volume of the mold, which was later used as the basis for computing volume

changes of the specimens.

In molding specimens, one thiclmess of dry

blotting paper was laid on a glass base plate and

covered with one thicloiess of wet, fine-textured

filter paper. The mold was then set on top of the

papers, large end down, and filled with mortar by

tamping in thi-ee equal layers. The top was then

carefully leveled off and covered ^vith a glass

plate. It was necessary to leave the specimens in

the molds for about a week, duiing which time

they were covered with glass jars and stored in

the same room as the bars for linear measurements.

Mortar

No. Mortar mixture Age

Total volume

of .shrink- age

Onethird of volume

shrink- age

Linear

test values

4 months

14 _.. 410

13

1(I3):3 1(D):3

l(F)-0 l(HL)-3

Weeks

5

10

912

15

717

14

4

Percent

1.08

.84

.78 1.35

. 81 L23

1..35 1.44 4.20

Percent

0..36 .28

.26

.45

. 27

.41 .45

.48 1.40

Percent

0. 1.57 .197

.2.38 .222

18 l(I1):Um:6.... . ](K)l(lll.);:i .199

22IN

L'll.M J Nr;[l, ci'mcrit. .535

After a week or more of curing at 75° ±5° F,

the specimen was removed from the mold. Some

specimens were easy to remove, and others had to be forced out. In most cases, there were several

bubble holes in the sides, which had to be carefully filled with neat cement and smoothed. After

filling the bubble holes the specimen was cured for

2 days in a damp cabinet.

5.2. Test Procedure

The only apparatus required for determining

volumes of specimens is a sensitive balance of

1-kg capacity and accessories for weighing speci- mens in water. The equipment and procedure for

weighing sijecimens in water is the same as described in ASTM Standard Method C97~47 for

determining bulk specific gravity. Having determined the weight of a soaked specimen in the

usual way and then its weight suspended in

water, the volume can be computed by the formula

Volume

of specimen after

d

in which

11^1 =wet weight in air soaking 48 hr,

IF2= weight of wet specimen and hanger

suspended in water,

6 =weight of hanger in water,

f/= density of water at observed temperature. The determined volume subtracted from the

volume of the mold is the volume shrinkage at time

of observation.

The first volume determination of each specimen was made as soon as the specimen was completed

and soaked for 48 hr, but usually this time was

about 10 days after the mortar was mixed. The

specimen was stored in a desiccator between times

of subsequent measurements.

5.3. Results of Tests

The results of tests by the volume method on

nine mixtures are shown in table 8. Five of these were taken from the batches mixed for linear

shrinkage. Because volume shrinkage is nominallv three times that of linear measurements, the

13
volume measurements given in table 8 have been

divided by three to simplify comparisons.

The balance used to determine volume changes was sensitive to 0.01 g, and 10 successive volume

measurements on 1 specimen during a period of

3 days showed a standard deviation of 0.017. These volume determinations increased about 0.05

percent from the first to the last observation,

which was probably due to moisture expansion of the specimens. The reproducibility of results is believed to be about 1 part in 20,000.

It was thought that the volume test specimen,

because of less constraint by friction on the mold,

would be less apt to form shrinkage cracks than

the long specimens used for linear measurements.

The measurements in the linear test were probably

affected considerably by the fact that shrinkage

undoubtedly occurred during the first 15 or 20

min while the reference plugs were being set and

the microscopes focused. This early shi'inkage

could not be determined by that method. By

contrast, the volume method determines total

contraction from the time the mixture is placed in

the mold, including slump.

Although the volume method has certain advantages in that simple specimens and apparatus can be used, the necessary filling of surface voids

caused by air bubbles is an exacting and timeconsuming task. Furthermore, the results are

vitiated to some extent by moisture expansion

while the specimens are soaking in water before

each determination. This could be overcome by

weighing the specimens in mercury instead of

water, and the accuracy of measurements would be

increased considerably.

6. Discussion of Volume Changes

Differences in curing conditions for the moitar

specimens tested for linear shrinkage and volume

shrinkage prevent an. absolute comparison of results obtained by the two methods. It is evident from the curves in figure 7 that the

greatest shrinkage occurs during the initial hardening period and that drying shrinkage of the

hardened specimens continues slowly for a considerable length of time. The maximum values

obtained by the two methods afford approximate

comparisons if tlie volume shrinkage is corrected

for moisture expansion during the 2 days of soaking

before the volumes were determined. Such comparisons on identical mixtures indicate that onethird of the volume shrinkages average about 40

percent higher than those obtained by direct linear

methods. The rapid shiinkage during the first 2 hr indicated by the curves in figure 7 shows that an appreciable amount of shrinkage must have

occurred before the first reading of the microscopes

could be made. If a correction for this were made, some of the differences would be ehminated.

Probably the greatest difference is due to a large

amount of the shrinkage being in a vertical direction. Vertical shrinkage is not ordinarily measured by the hnear method.

For like conditions of curing it is probable that

the two methods would give comparable results if by some means the early shrinkage could be

included in the linear measurements, and the

volume determinations were corrected for moisture

expansion caused by immersion in water. In order to illustrate the effect of shrinkage on measurements between reference points when

cracking occurs, two clay specimens were made.

A kaolin of low wet strength and a ball clay of

high wet strength were used. Each clay was mixed with sufficient water to secure a consistency

judged to be the same as that of a stone-setting

mortar. Two shallow pans were filled with the

mixtures and the top surfaces leveled with the

tops of the pans. Several reference pins were set

in each pan with a specially made gage, so that

they were in line both longitudinally and transversely. The clays were allowed to dry in the

laboratorv for a week, then placed in an oven at 110° C for 2 days.

In figure 8, the top surfaces of the cla3'^s are shown with the pins encircled in ink. The lines at one edge of the pans indicate the original

position of the transverse rows of pins. The

high-strength clay, shown in the larger pan, contracted without cracking and some of the pins

moved slightly out of line. The low-strength clay

cracked, and there was little movement of the

pins; however, in the second transverse row from

the right, the middle pin moved considerably out

of line. It appears that shrinkage divided the

clay into sections, which shrank as units.

The shrinkage of the high-strength clay longitudinally was 11 percent as obtained by over-all measurements or measurements between the pins.

Similar measurements on the other specimen

indicated only 0.59-percent shrinkage. However, when the width of cracks, measured between

pins, was added to the amount the pins moved,

the result indicated a shrinkage of 5.0 percent.

Vertical shriid^age in the larger specimen was

measured by placing a straightedge on the top

of the pan and measuring from it to the surface

of the clay. The top surface was concave and

lowest at the center because of constraint by the

sides and ends of the pan. Several measurements

along the centerline indicated an average vertical

shrinkage of 22 percent. An estimate of vertical

shrinkage in the low-strength clay could not be

obtained because most of the sections between

cracks warped upward at the edges.

It is not likely that the difference in shrinkage

vertically and horizontally is the same for mortars and clays, but evidence was found that much

of the shrinkage in mortar is vertical. In speci- mens made for volume shrinkage the mortar

slumped noticeably below the top of the mold.

Most of the specimens were difficult to remove

from the mold, which indicated only slight horizontal shrinkage. This was further demonstrated

14
J

G

0

O

e

o

o

o

Figure 8. Shrinkage of clay specimens {top surfaces). The smaller specimen was made of a Delaware kaolin, the other of a Kentucky ball clay. The pans were filled flush with the top and the pins (encircled) were set in line with the lines at the edges of the pans. In drying, the kaolin cracked and the pins moved very little. The ball clay shrank as a unit and the

pins moved consistently. The movement of the pins in the kailin indicates a shrinkage of less than 1 percent, whereas for the ball clay a shrinkage of 11 percent

is indicated.

by setting- some of the specimens in water neai-ly to the top while still in the mold. There was no

capillary rise of water between the specimens and

mold. One specimen required a load of 400 lb to force it out of the mold, which indicated that

it was bonded to the metal.

Linear changes in cement products often called

•"volume change," have been measured chiefly

by two methods. One of these involves setting

reference marks in specimens as soon as the mixture is placed in a form and using micrometer

microscopes to read the changes. This method

was used by Pearson [4], Scholer and Dawley

[5], and by the present authors. For this method,

the specimens are always molded in a horizontal

position, and no indication of vertical shrinkage

is obtained. The horizontal movement of the

reference points is accurately obtained, but the

results ma}^ be in error if cracks form between the

points or if shrinkage occurs before the first reading is made. A more common method is to set metal plugs or glass plates in the ends of speci- mens when being molded and to start measure- ments after the cement has hardened sufficiently

to permit removal of the specimen from the form.

This method disregards the shrinkage that occurs during the first 24 hr or longer. According to Scholer and Dawley [5], there is no shrinkage

during this period if watertight forms are used

and evaporation is prevented. A variation of the

last procedure has been used by Palmer and Parsons [3], who measured the length of the mold

and used this as the original length from which

to compute later shiinkage. They obtained

high shrinkage values as compared to those

commonly reported for 1:3 mortars made of portland cement, masonry cement, or lime. Rogers

and Blaine [6] employed a method in which

1- by 1- by 8-in. specimens were molded in 6-gang

vertical molds with glass plates on top and bottom

of each specimen. As soon as the top plates were in position the mold was set under a battery

of dial gages, which gave the amount of shrinkage

at any desired time. Their measurements on 1:3 mortars in which the cementing material was

Portland cement, portland cement and lime,

natural cement, portland and natural cement,

or straight lime gave a large range of values.

In each group the maximum values were near

0.50 percent, with some minimum values below

0.20 percent. The large range might be caused

by crack formations between the points of

measurement in some of the specimens. The

small cross section of the specimens and friction

between the mortar and sicles of the molds may

have constrained shrinkage.

Carlson [2] has studied shrinkage with particular

reference to the effect of internal cracking. He

advances the theory that all cement mixtures

would shrink as much as neat cement if they were

not constrained by aggregate particles. The compressibility of quartz and most other types of

rocks is very small; the cement paste surrounding

each sand particle is, therefore, in tension due to shrinkage. The result is that fine cracks are formed in the paste between the fine aggregate

grains. Much of this shrinkage is not indicated

by ordinary methods of measurement. Carlson

made a specimen with rubber aggregate instead

of sand or gravel and found that it contracted

about eight times as much as ordinary mixtures.

Some studies made at the National Bureau of

Standards on crack formations in terrazzo have

a bearing on Carlson's theorv. Terrazzo is made

15
FifiURE y. T(:'nii::ii ^ iircimens. A and B were made of marble chips and a finely ground cement, whereas 0 was made of marble chips and a coarser cement. Specimen D was made of a

fiiirl y ornund pement and rubber aggregate. A and B cracked extensively, whereas C did not form visible cracks. D cracked moderately near the outer edge

FiouRK 10. Shrinkage cracks in cement surround aggregate

particles of low compi esstbitity. Each specimen is a J-^-in. cylinder of neat cement enclosing one fragment

of marble.

of 1 part Portland cement and 2 parts marble

chips. In figure 9, A and B show two specimens,

made with a finely ground cement, which cracked

extensively. Specimen C was made with a coarser cement, and it has relatively few cracks. Specimen D was made with a finely ground cement and

a rather hard rubber aggregate. No cracks are

visible in the center area, but some developed in

the outer part, possibly clue to difi^erential drying.

All the specimens shown in figure 9 were dampcured under identical conditions.

Each specimen sliown in figure 10 was made

with a single marble chip and portland cement

molded into a K-in. cylinder and damp-cured for

2 weeks. All of these cracked badly. This is not surprising because the linear shrinkage of

neat cement, as determined by the volume method,

is 1.4 percent. In a mortar the sand particles are surrounded by neat cement, and it seems

inevitable that fine cracks will form in great

16
numbers, although they may be too small to be

visible.

7/ Resistance to Freezing and Thawing

7.1. Specimens and Test Procedure

The mortar bars used for determining linear

shrinkage were cut into prisms 2.5 by 2.5 by 2 in. after the sluinlvage tests were completed. In

order to adapt these blocks to accurate volume

determinations, the bubble holes showing on the

surface were filled with neat cement.

The dry weights, absorptions, and volumes of

two specimens of each mortar were determined

before the freezing tests were started. These

were frozen at —15° C (free to drain in still air)

and thawed in water at room temperature. Two

cycles were made each day, and the specimens were in the freezing chamber at least 6 hr for each freezing. During the night or over holidays

they were in the freezing chamber much longer.

In the early stages of this test, the specimens were tested for volume changes after each 20

cycles, but when it was found that changes were

taking place very slowly the periods between

volume tests were extended. After 940 cycles

had failed to produce any marked deterioration, a final examination was made and the test dis- continued.

Sonic methods of determining changes in modulus of elasticity during the test could not be

used because the specimens were too small.

7.2. Results of Tests

Volimie changes, final strengths, and visual

changes are reported in table 9. Absorption and

weight changes were not of sufficient magnitude to justify conclusions, and these values are not

tabulated. During the progress of these tests,

it was foimd that the wet weights of specimens

increased considerably, as is common in freezing

tests on many other porous materials. At the

end of the test these specimens were dried m an oven at 115° C for 10 days, and over half of them

still weighed more than indicated by their original

dry weights. One possible reason for this is that

water forced into fine capillaries could not be

driven off at ordinary drying tempcu-atures.

Further hydration of the cement may have ac- counted for some of the weight increase.

The original strengths of these mortar specimens were not determined, hence the values given in

table 9 afford no basis for judging strength losses due to freezing. They are stated merely to show

that the mortars did not suffer severe deterioration

in the freezing test. Some of these can be <-om- pared with the results of compression tests made on

specimens cast in metal molds and reported in

table 1. These do not, however, afford reliable

comparisons because specimens made in porous

molds give higher test values, as reported in

section 8.

7.3. Discussion of Results

All the mortars in this test showed excellent

frost resistance, and the small differences indicated

by the results are not conclusive. The high

resistance to frost deterioration may have been

due to the specimens being made in porous molds,

which probably reduced the water-cement ratios

of the specimens.

Judged b}^ the decreases in volume and the final strengths, it may be assiuned that the 1 : 3 mixture

made with portland cement D and a similar

mixture made with masonry cement H were the

least resistant. Other 1 : 3 mixtures indicated

satisfactory results. The mixtures containing

ground limestone or hydrated lime gave indications of good frost resistance. This may- be

accounted for, in part, by the increased air

entrainment caused by the addition of fine materials.

8. Effect of Different Curing Conditions

In some of the early tests of this investigation

it was noted that specimens molded and cured in

contact with porous materials indicated that such

conditions were favorable to the mortars. This was interpreted to mean that the extraction of

Table 9. Results of tests and observations on specimens after 940 cycles of freezing and tha wing

Mortar No.

22

21. 20

13.

4_. 4..

24.

1.. 27.

2..

3..

7..

Mortar mixture

l(F):2(Ls);2.._.

l(F):1.2(Ls):2.4

l(F):0.6(Ls):2.4 1(F);0.1(HL):3. 1(D) :3 1(0:3

l(E):l(H):6-_.

1(A) :3 l(G):l(J):6 1(B):3

1(C):3 1(H) :3

Decrease

in volume

ml

0. 54 .42

.38

.31 .86

.77

.46

.24

.16

.24

.46

1.05

Compressive

strength

after freezing

pst

10, 050 11,060

11, 230

8, 140 3,540

3, 200

5, 220

6, 970 4,970

8,380

6,370

3,190

Appeai'ance

Cracks

None— _ do

dodo __ do

do

do _ do

do

do - do

do

Edges

Sharp..

do.. do.

do-.

do.. Rough.

do.. do..

do.. do..

do.. do..

Remarks

Slight spalling.

Slight spalling.

Slight crumbling.

IT
excess water from the mortars, while still plastic, was desirable and that mortars may perform in

masonry better than might be expected when

judged hy results of laboratory tests. It was

decided to experiment on specimens made and

cured imder conditions simulating those in masonry

and also those in the usual laboratory tests for more definite comparisons.

Molds were made of limestone used for the sides

and bottom to simulate the masonry condition

and of wood to simidate the laboratory condition.

Both types were designed for casting thin speci- mens on edge, so that each specimen woidd be

surrounded by a 1-in. thickness of porous or impermeable material.

The limestone chosen for making the molds was

the same as that used in the bond test specimens

and described in section 2.-3. The wood molds

were greased inside to make them impermeable.

The mortar mixtures were of the same proportions as used in the bond tests, but some of the

ingredients differed. New samples of cements E

and F and sand from a different source were used.

The sand all passed a No. 8 sieve, and the per- centages retained on the Nos. 16, 30, and 50

sieves were 19, 38, 57, and 95, respectively. This

sand contained more cfuartz grains, which were somewhat coarser and more angidar than those of Potomac River sand.

The five mortar mixtures listed in table 10 were made and molded into specimens 4 by 5 by 1 in. The 4-in. dimension was vertical, and the mortars were tamped in 3 layers. Half of each mixture was placed in one type of mold and half in the

other. The molds were left open for 2 hr and

then covered with damp burlap, which was soaked once each day. Both t^^pes of specimens were

thus cured in the molds for 1 month.

The specimens were first tested for flexural strength, then the two ends of each were cut into

pieces 3 in. square for absorption and bulk density

tests. Finally, 1-in. cores were cut and tested for compressive sti-ength.

Results of all tests are shown in table 10, which

also shows the number of tests that were averaged

for each propei'ty. The results consistently sliow

that specimens made in porous molds were of

superior quality. Such curing seems to be more

favorable to the masonry cements than to portland

cements.

9. Relation of Mortar to Performance

of Masonry

Some of the undesirable performances of stone

masonry are often attributed to the setting mortar.

It is proposed to discuss some of these in relation

to laboratory results and observations on structures. Evidently much can be learned from studies on existing structures that show that errors have been made in selecting or combining materials. Laboratory research cannot feasibly reproduce all of the conditions in masonry or the time

factor. It is not to be inferred that the followingstatements are proved facts, but if they lead to further discussions and records of exper'iences

from others, some good purpose may be served.

9,1. Spalling of Stone at Mortar Joints

Stone blocks sometimes spall at the mortar

joints. The spalls are usually thin and feather

out 2 or 3 in. away from the joints. The spalls

usually occur at vertical joints in ashlar masonry.

They appear to be shear failures due to temperature stresses. A common explanation suggested

for such trouble is that the mortar was too strong.

Stonework erected in cold weather could be

expected to develop temperature stresses in

vertical joints in summer. A computation based on a temperature rise of 80 deg F indicates that

stones of the usual thermal expansion and elasticity values could not be stressed more than 1,500

psi in compression, if the joints are well filled with

mortar. Most building stones have compressive

strengths, as determined by standard tests, of more than 5,000 psi.

In tests for compressive strength, the ends of

specimens are placed in direct contact with the

metal plates of the testing machine. Under such

conditions, friction between the metol and stone

Table 10. Comparison of curing conditions in wood molds and limestone molds

Mortar

No. Mortar mi.xturo

Compressive strength ' Modulus of rupture 2 Absorption s Bulk density s

Type of mold

Ratio < Type of mold

Ratio < Type of moldRatio < Type of mold

Ratio * Wood Stone Wood Stone Wood Stone Wood Stone

198

15

7

5

l(F):0.5(Ls):3

1(1) .-3 1(E):0.4(HL):3

1(H):3 1(E) :3

]>si

4, 360

1, 140

4, 760

580 2,960

psi

6, 770

2, 450

6, 850

1,040

6, 140

1.55

2. 16 1.44 1.80

2. 07

psi

1,377 624

1,473 303

1, 065

psi 1,742 972

1. 840

521

1, 638

1. 26

1.56

1. 25

1. 72 1.54

%

8.60

9. 85 9.30

11.25

7. 62

%

6.98

7. 89

8. 01

6. 55

5. 61

0. 81 .80

.86

.58

. 74

2. 014

1.860

1.986

1.745

2. 021

2.080

1.894 2.044

1. 789 2.049

1.03

1.02

1.03

1.02

1. 01

1 Each value is the average of either 6 or 7 individual test i Ratio of the test value of the specimens made in stone mold to that of the

2 Each value is the average of 3 tests. specimens made in wood mold.

3 Each value is the average of 2 tests. 18 '
is sufficient to prevent lateral expansion at the

ends of specimens, and spalling; is restrained.

However, if some pliable material, such as lead

or several thicknesses of blotting paper, is insei-ted between the specimen and the metal plates, l)oth

spalling and final failure will occur at lower loads

than in the standard test. A similar stress condition probably exists at the contact between stone and mortar in vertical

joints because the thermal coefficient of expansion

of mortar is greater than that of stone. "When the

temperature rises and causes compressive stresses

at the joints, the mortar also expands perpendicular to the face of the masonry at a greater I'ate than that of the stone. Such a condition is probably more favorable to spalling than that in

the compression test where pliable materials are used between the stone and metal.

Some engineers have emphasized the desirability

of making mortars less rigid. Although the E

values of mortars can be varied considerably, it is

I necessary to make the mortar rather weak in order

to obtain a value below 2,000,000. The mortar

j joints in ashlar masonry make up such a small

portion of the wall that little is gained in this way,

i| and weak mortars are not apt to have sufficient

I resistance to weathering. A more logical course is

1 to make the mortar sufficiently strong for weather

' resistance and take proper measures to thoroughl}^

I fill the vertical joints. It is a common practice to set blocks in ashlar

masonry on a leveled bed of mortar and fill the

vertical joints later. The edge of the vertical joint

is stopped with a hemp rope, and a grout is poured

j in until the space appears to be ffiled. This method

I may not completely fill the joint, and in any case

' high shrinkage of the mortar will occur because

of the large excess of water. Pointing usually takes

care of leakage whether the joint is thoroughly

filled or not, but it may bring about a condition

favorable to spalling, especially if strong mortar

is used. The pointing mortar should not be

stronger than the setting mortar.

Occasionally, spalls at the edges of stone blocks can be accounted for by defects in the stone or by

injury in the fabrication process. When spalls occur directly opposite each other on either side

of the same joint, it is logical to assume that the

trouble was due to overstressing of the stone.

9.2. Efflorescence and Discolorations

Some of the water-soluble salts causing efflores- cence ma}^ come from the mortar, but in most

cases more come from other materials in the wall. The salts exist in small amounts and have to be

leached to the surface by water percolating through

the masonry. The most feasible means of prevention is to stop the entrance of large amounts of

1 water. Absorption from the face is not likely to be sufficient to cause appreciable efflorescence,

unless there are open joints. Efflorescence on

: stone masonry is usually localized in ai'eas where

considerable water finds entrance because of faulty

drainage or other causes. The capillary rise of

moisture from the ground is a (common cause of

efflorescence in buildings without grade waterproofing.

Discolorations, occuri'ing mainly on new buildings, are usuallv leached out of the walls in the same way as efflorescence salts. Frequently, the

two troubles go hand in hand, and apparently the

salts causing efflorescence aid in bringing out the

discolorations. Probably there are many sources

of the discoloring matter, but the most common is believed to be the stone. Bi'own stains occurring on sedimentary rocks are usually caused by or- ganic matter, such as can be carried into stone ledges near the surface of the ground from decayed

vegetation. The position of the stains on masonry

is often near the mortar joints, and for this reason

it is commonly believed that the staining matter

is from the mortar. The alkalinity imparted to the percolating water by the cement in mortars is involved in the transfer of the organic stains from

the interior of the masonry to tVie surface [7,8]. Cements of low iron content called "nonstaining

cements" have appeared on the market. Since

the staining matter is not iron, as formerly believed,

the value of such cements depends largely upon

their low alkali content. Some specifications for

stone-setting mortars place a limit on alkalinity

of the cements. The use of "nonstaining cements"

for the setting mortar will not prevent discolorations if a large amount of normal cement has been

used in the backing wall unless an effective water

barrier between the facing and backing is provided.

A considerable amount of water passing through

the masonry is necessary to bring out conspicuous

discolorations, and proper precautions taken

during the construction of walls will usually

prevent such troubles. The tops of unfinished

walls should be covered during rains to prevent

saturation of the masonry. A simple expedient

that is believed to be helpful is to provide freciuent

weep holes in the facing. These should be in the

vertical joints so they can be sloped upward from

front to back.

9.3. Calcareous Vein Formations

In damp locations where considerable water

finds egress through small cracks, there are apt to be vein formations such as illustrated in figures 1

1

and 12. Because these veins are mainly cal- careous, it seems likely that thev result from

calcium hydroxide dissolved from the cement and

deposited where the water evaporates. When

this hydrate is exposed to the air, it takes up

carbon dioxide and changes to calcium carbonate.

Frequently, such formations fill the original crack

and continue to grow into adjacent masomy

materials. Figures 11, A, and 11, B, show manv

cracks opposite each other in blocks of marble on

either side of vertical mortar joints. Apparently,

the cracks in which the veins originally started

19
Figure 12. Calcareous vein formations in brick masonry similar to those in figure 11. The extensive migration of the formations is probably due to a large amotmt of free lime in the mortar joints and considerable water seepage. 20
j were cracks in the mortar. It has been denionstrated in the hiboratory on a small scale that

I these growths can form in mortar cracks and

continue into marble slabs, surrounded by the

i mortar, to start cracks.

I Such vein formations are also found in other

kinds of masonry. Figure 12 shows a brick wall

Anth extensive cracks filled with calcareous

growths. They are of common occurrence in concrete pavements, steps, and various other

\ structures. There is a sufficient amount of lime

\ in the cementing materials to form abundant

growths if a considerable amount of water passes

' thi'ough the masomy. The solubility of hydrated

lime is only about 1 part in 600 parts of water,

hence the growths progress slowly but may become

apparent within a few years.

9.4. Shrinkage Cracks

High shrinlvage may cause cracks either between

: the stone and mortar, in the mortar, or across the

I joints. A mortar having a slmnl?;age of 0.2 percent

shoidd, theoretically, separate from the stone in

j vertical joints.* However, the results obtained in

j tests for bonding strength on a mortar of 0.5-

I percent shrinkage for specimens simulating the

' conditions in vertical joints were satisfactory,

! and no separations from the stone occurred.

' The reason is believed to be that the mortar was

I sufficiently slow-setting and plastic to enable it to

1 adjust itself to the major shrinlcage that occurs

I before the mortar sets. In the part of the experi-

,1 mental wall where a 1: 3 lime mortar was used, it

I was necessarv to wedge up each stone to prevent

'I settling. The shrinkage of this mortar was not

I determined, but it was probably at least 0.5 percent. Under such conditions, it might be

,! expected that the mortar would shrink away from

'{ the stone in both horizontal and vertical joints.

I So far as could be determined by observations

1 tliis did not occur to any appreciable extent.

'\ Possibly the adhesion of the mortar in the plastic

1. state was sufficient to maintain the bond and

I cause voids within the mass. Such effects have

I been frequently noted in plastic calking com-

\ pounds where contact with the sides of joints was

maintained but cavities formed within the plastic

itself. Such compounds often shrinlv 20 percent

or more by volume.

'I

* The relation between stress, strain, and modulus of elasticity of an elasti- cally deformed body is, S=Ee, where S is the force per unit of area, E the modulus of elasticity, and e is the unit deformation. B for most mortars

is at least 2,000,000 psi. Assume that the shrinkage of an unrestrained mortar

is 0.2 percent. In a vertical joint, if the adjoining stones do not move, and if the mortar adheres to the stone and remains intact, its unit deformation e, upon drjing, must be 0.002. Substitution of these values of E and e in the above equation results in a value for stress of 4,000 psi. Neither the tensile strength nor the bonding strength of the mortar to the stone is sufficient to withstand such a stress. It is apparent, therefore, that where such a joint remained intact, some deformation must have occurred while the mortar was plastic.

9.5. Surface Scaling

A phase of weathering that catiscs rapid surface

deterioration of stone and other masonry materials

results from crystallization of waterborne salts within the pores. The common source of the salts have been discussed in section 9.2. Aside from

water-soluble salts originally in the masonry material, it is recognized that chemical reactions sometimes result in the formation of other salts that

give trouble.

Efflorescence is commonly referred to as a for- mation of the salts on the surface where water

solutions evaporate. Some of the salt crystals may

form in the pores of masonry near the surface.

The crystal growth in the pores produces stresses on the walls of pores sufficient to force off flakes of the stone. This type of decay can usually be

readily distinguished from others by its appearance. Usually the masonry materials are not

appreciably injured except near the surface, but

if the conditions bringing about the action persist,

the scaling may continue to flake oil" one layer

after another until a considerable depth is reached.

For this, a large amount of water has to enter the

masonry, and there must be a considerable supply

of the salts. When there is a continual soaking of some part

of the masomy, it is sometimes noted that scaling

is not uniformly distributed over the dampened

area. Different materials or even different parts

of one material may disintegrate and others show

little or no effects. A case has been cited by

Schaffer [9] where limestone and sandstone were

used in alternating courses and scaling was confined mainly to the sandstone. For such selective

decay he mentions the possibility that the sandstone may have a higher capillary "pull" than the

limestone, which enabled it to draw most of the

salts away from the mortar joints. The same

authority illustrates selective decay by what he

calls soft beds in some kinds of stone, which cause

the stone to scale more rapidly in certain zones than others. Such performance has been noted

for some stones in this country, but such stones,

in the original condition, seem to be of quite uniform hardness. In the exposure test wall some of

the very hard stones have undergone pronounced

scaling within a period of 4 years, whereas adjoining stones of various textures and densities have

remained in perfect condition. Such results indi- cate that the capillary forces in some materials are strong and enable the materials to draw water

solutions from adjacent materials.

Ordinarily one would not expect that a sufficient amount of salts would be present in thin mortar

joints to cause scaling of adjoining stones. One

sandstone building can be cited where bands of scaling have formed in the stone bordering the

joints. This stone is very fine-grained and is known to have rather high capillaiy suction. In

li 21
this case the indications are that the sahs were drawn from the mortar.

The rates of drying after the materials have been

soaked may also have some significance in relation

to the movements of salt solutions in a masonry

wall. Twelve mortar mixtures were subjected to

this test, and the results are given in table 11. The specimens were soaked by complete immersion in water for 24 hr, weighed, and exposed to

air on all faces. The air temperatures varied

between 75° and 85° F, and the relative humidity

varied between 45 and 60 percent. The results are believed to be comparative for the mortars

involved because they were all exposed at the same

time and same location.

Evidently these mortars all dried slowly in comparison to the drying rates for most building

stones. Most of the specimens retained 70 per- cent or more of the water for 24 hr. Sixteen limestones tested in the same way indicated much

higher drying rates. The average loss of total

water content was 25 percent in 6 hr and 75 per- cent in 24 hr. After 24 hr none of the specimens

retained more than 45 percent of the water. In this investigation a few studies were made to determine differences in pore structure in certain stones and a few mortars. One test (test A in table 11) consisted in measuring the rate of absorption during 1 min when only one face of the

specimen was in contact with water, then after

drjdng, measuring the 1-min absorption when all but one face was in water (test B). Under such

conditions, one might expect that the absorption

in test B would be greater in proportion to the

areas in contact with water. For tlie oolitic lime- stones used in this test the absorption ratios were

near the area ratios, but with the mortars this was not the case. When the area ratios for mortar

specimens were more than 4:1 the absorption

ratios were frequently less than 2.5:1. This seems

to indicate that when a specimen is absorbing onh'

from the bottom, air displaced by the water can

escape fairly readily from the sides, but when the

bottom and sides are submerged there is less opportunity for the air to escape and absorption

is delated. The test is simple and is believed to give information on pore structure. Although

there is an appreciable dift'erence between the

various mortars, as shown by the ratios, the re- sults indicate that mortars generally have fewer

connecting pores than the more commonly used

limestones have.

10. Summary and Conclusions

1 . Several mortar mixtures in which the cementing material was portland cement, masonry ce- ' ment, natural cement, or combinations or portland

with natural or masonry cement were studied.

Lime or ground limestone was combined with

several portland-cement mixtures.

2. Bonding strengths of 33 mortars to natural stone were studied. The bonding strengths to fine-grained stones were considerably higher than

to coarse-grained stones. Sixteen mortars were

tested for bonding strength in limestone joints

simulating the conditions in both horizontal and

vertical masonry joints. Eleven of these gave

practically the same strength in both types of

joints, and the other five averaged 60 and 40 psi,

respectively, for the horizontal and vertical joints.

In 1 : 3 mortars of masonry cements or 1:3 mortars in which the cementing material was a half- and-half mixture of masonry and portland cements,

the bonding strengths were rather low. The

results indicate that 1 : 3 mortars of portland

cement are apt to give variable bonding values in

vertical joints. The addition of 40- or 50-percent

hydrated lime by volume of portland cement or

like amounts of ground limestone, to straightcement mortars seems to improve the uniformity

of bonding strengths in horizontal and vertical

joints.

Table 11. Absorption rates and drying rates of mortars

Drying rates of saturated specimens

Absorption rates Mortar Xo. Mortar mixture Water retained

Test A 2 Test B ' B/A after 6 hr after 24 hr

g 9 % %

22 l(F):2(Ls):2 0.68 1. 44 2.

1

87 80

21 l(F):1.2(Ls):2.4 .31 .71 2.3 91 84

19 l(F):0.5(Ls):2 .32 .78 2.4 92 86

13 1(F):0.1(HL):3 .22 .56 2.4 92 89

4 1(D):3 1.08 2.29 2.

1

85 42

4 1(D):3 1.00 2. 39 2.4 88 43

24 1(E):1(H):6 . 19 .48 2.5 82 75

1 1(A) :3 .14 .52 3.7 89 83

27 1(G):1(J):3 . 19 .48 2.5 86 76

2 1(B):3 .22 .46 2.

1

85 80

3 1(C):3 .22 .50 2.3 89 84

7_. 1(H) :3 .42 1.23 2.9 78 52

1 One minute absorption in grams.

2 Area in contact with water in test A = 6.25 in-

' Area in contact with water in test B = 26.2.5 in 2.

22
3. A study of methods for determining shrinkage of cement mixtures indicates that many of the

"

j pubUshed vahies does not inchide the shrinkage

M that occurs while the mortars are plastic. MorI tars, when placed in contact with porous materials,

^ 1 shrink rapidly during the first few hours, and most

test methods do not measure this early shrinkage.

Linear methods do not indicate localized contrac-

'

' tions that cause cracks between points of reference, nor do they indicate vertical slu'inkage. Cracks

between points of measurement may divide the

specimen into sections that shrink as units. The

cement paste surrounding rigid aggregate particles,

such as the sand in mortars, inevitably cracks

because the slirinkage of the paste is much greater

I than the compressibility of the aggregate.

,

' Shrinkage measurements were made by two

I I methods with the object of finding the total shrinkage of mortars from the time they were placed in

I (j' the molds. Linear values determined by a comI

' parator method ranged from 0.157 to 0.535 percent,

whereas a method for determining volume shrink-

(j age usually gave considerably higher values. Experiments with clay mixtures indicated that crack

formations in specimens cause results of measui-ements to be too low and that shrinkage in the vertical direction, while the mixture is still plastic, is much higher than in a horizontal direction.

The addition of 0.4 or 0.5 percent of hydrated

'I lime or ground limestone to 1:3 portland-cement

I mortars greatly increases the shrinkage, but the

I improved working qualities imparted by such addi-

! tions enables the mixtures to adjust themselves to high initial shrinkage and give good bondingstrength in vertical masonry joints,

j 4. Tests on mortar specimens molded in contact

; with porous materials indicated higher strengths

and lower absorptions than those obtained on

specimens made and cured by standard laboratory

I methods.

I

5. Freezing and lhawing tests on 12 mortal's,

foi- which the specimens had been molded an(l

cured in contact with porous materials, indicated

satisfactory resistance values for all of tlie mixtures.

6. Some of the more common troubles in stone masonry, frequently attributed to unwise selec- tion of mortars, have been (Uscussed. A few of the usual weatheiing processes in masonry struc- tures have been described and cnlcareous vein

formations illustrated.

11. References

[1] J. C. Pearson, Properties and problems of niasonr\-

cements, Proc. Am. Concrete Inst. 28, 349 (1932).

[2] Roy W. Carlson, Drying shrinlvage of concrete, Am.

See. Testing Materials, Proc. 38, part II, 419 (1938).

[3] L. A. Palmer and D. A. Parsons, A stndy of the properties of mortars and bricks and their relation to bond, BS J. Research 12, 609 (1934) RP683.

[4] J. C. Pearson, Shrinkage of portland cement mortars,

Proc. Am. Concrete Inst. 17, 133 (1921).

[5] C. H. Scholer and E. R. Dawley, Volume change of concrete. Am. Soc. Testing Materials 30, part II, 751 (1930).

[6] Jesse S. Rodgers and Raymond L. Blaine, Investigations of commercial masonry cenents, .J. Research

NBS 13, 811 (1934) RP746."

[7] D. W. Kessler and W. H. Sligh, Physical properties

of the principal commercial limestones used for building construction in the United States, Techn.

Pap. BS 21, 497 (1927) T349.

[8] F. O. Anderegg and H. C. Peffer, Indiana limestone

1. Efflorescense and staining, Engineering Experiment Station Bui. No. 33, Purdue University (1928).

[9] R. J. Schaffer, The weathering of natural building

stones. Special Report No. 18, Dept. of Scientific and Industrial Research (His Majesty's Stationery

Office, London, 1931).

[10] Anon., Measurement of capillary forces in building

stones, Report of the Building Research Board,

Dept. of Science and Industrial Research, p. 12

(His Majesty's Stationery Office, London, 1928).

[11] Anon., Measurement of capillary forces in porous

materials, NBS Technical News Bui. No. 271 (Nov.

1938).

1!

23

U. S. GOVERNMENT PR 1 NTl NG'OFFICE t '! 9 53
1
BUILDING MATERIALS AND STRUCTURES REPORTS

[Continued from cover page ii] BMS32 Structural Properties of Two Brick-Concrete-Block Wall Constructions and a Concrete- Block Wall Construction Sponsored by the National Concrete Masonry Association. 15^ BMS33 Plastic Calking Materials * BMS34 Performance Test of Floor Coverings for Use in Low-Cost Housing: Part 1 15i

BMS35 Stability of Sheathing Papers as Determined by Accelerated Aging * BMS3t) Structural Properties of Wood-Frame Wall, Partition, Floor, and Roof Constructions

With "Red Stripe" Lath Sponsored by The Weston Paper and Manufacturing Co-_ 10^ BMS37 Structural Properties of "Palisade Homes" Constructions for Walls, Partitions, and

Floors, Sponsored by Palisade Homes * BMS38 Structural Properties of Two "Dunstone" Wall Constructions Sponsored by the W. E. Dunn Manufacturing Co 10^ BMS39 Structural Properties of a Wall Construction of "Pfeifer Units" Sponsored by the Wisconsin Units Co 10^ BMS40 Structural Properties of a Wall Construction of "Knap Concrete Wall Units" Sponsored

by Knap America, Inc * BMS41 Efifect of Heating and Cooling on the Permeability of Masonry Walls * BMS42 Structural Properties of Wood-Frame Wall and Partition Construction with "Celotex"

Insulating Boards Sponsored by The Celotex Corporation * BMS43 Performance Test of Floor Coverings for Use in Low-Cost Housing: Part 2 * BMS44 Surface Treatment of Steel Prior to Painting * BMS45 Air Infiltration Through Windows 15^ BMS46 Structural Properties of "Seott-Bilt"„Prefabricated Sheet-Steel Construction for Walls,

Floors, and Roofs Sponsored by The Globe-Wernicke Co * BMS47 Structural Properties of Prefabricated Wood-Frame Constructions for Walls, Partitions, and Floors Sponsored by American Houses, Inc 20^ BMS48 Structural Properties of "Precision-Built" Frame Wall and Partition Constructions

Sponsored by the Homasote Co 15(S BMS49 MetalUc Roofing for Low-Cost House Construction 20^ BMS50 Stability of Fiber Building Boards as Determined by Accelerated Aging * BIMS51 Structural Properties of ' Tilecrete Type A" Floor Construction Sponsored by the

Tilecrete Co 10^5 BMSo2 Effect of Ceiling Insulation Upon Summer Comfort 15^ BMS53 Structural Properties of a Masonry Wall Construction of "Munlock Dry Wall Brick"

Sponsored by the Munlock Engineering Co 10^ BMS54 Effect of Soot on the Rating of an Oil-Fired Heating Boiler 10^ BMS55 Effects of Wetting and Drying on the Permeability of Masonry Walls * BMS56 A Survey of Humidities in Residences * BMS57 Roofing in the United States—Results of a Questionnaire * BMS58 Strength of Soft-Soldered Joints in Copper Tubing . 10^ BMS59 Properties of Adhesives for Floor Coverings * BMS60 Strength, Absorption, and Resistance to Laboratory Freezing and Thawing of Building

Bricks Produced in the United States 300 BMS61 Structural Properties of Two Nonreinforced Monolithic Concrete Wall Constructions. _ * BMS62 Structural Properties of a Precast Joist Concrete Floor Construction Sponsored by the Portland Cement Association 15(S BMS63 Moisture Condensation in Building Walls 15^ BMS64 Solar Heating of Various Surfaces * BMS65 Methods of Estimating Loads in Plumbing Systems 15jJ BMS66 Plumbing Manual 350 BMS67 Structural Properties of "Mu-Steel" Prefabricated Sheet-Steel Constructions for Walls,

Partitions, Floors, and Roofs, Sponsored by Herman A. Mugler 150 BMS68 Performance Test for Floor Coverings for Use in Low-Cost Housing: Part 3 200 BMS69 Stability of Fiber Sheathing Boards as Determined by Accelerated Aging , 100 BMS70 Asphalt-Prepared RoU Roofings and Shingles 200 BMS71 Fire Tests of Wood- and Metal-Framed Partitions * BMS72 Structural Properties of "Precision-Built, Jr." Prefabricated Wood-Frame Wall Construction Sponsored by the Homasote Co * BMS73 Indentation Characteristics of Floor Coverings 100 BMS74 Structural and Heat-Transfer Properties of "U. S. S. Panelbilt" Prefabricated SheetSteel Constructions for Walls, Partitions, and Roofs Sponsored by the Tennessee

Coal, Iron & Railroad Co 200 BMS75 Survey of Roofing Materials in the North Central States 150 BMS76 Effect of Outdoor Exposure on the Water PermeabiUty of Masonry Walls * BMS77 Properties and Performance of Fiber Tile Boards * BMS78 Structural, Heat-Transfer, and Water-Permeability Properties of Five Earth-Wall

Constructions 250 BMS79 Water-Distributing Systems for Buildings ^ 200 BMS80 Performance Test of Floor Coverings for Use in Low-Cost Housing: Part 4 150 BMS81 Field Inspectors' Check List for Building Constructions (cloth cover, 5 x TJr^ inches) 300

•Out of print.

[List continued on cover page iv]
BUILDING MATERIALS AND STRUCTUEES REPORTS

[Continued from cover page iii] BMS82 Water Permeability of Walls Built of Masonry Units 25^

BMS83 Strength of Sleeve Joints in Copper Tubing Made With Various Lead-Base Solders 15^ BMS84 Survey of Roofing Materials in the South Central States 15^ BMS85 Dimensional Changes of Floor Coverings With Changes in Relative Humidity and

Temperature * BMS86 Structural, Heat-Transfer, and Water-Permeability Properties of "Speedbrik" Wall

Construction Sponsored by the General Shale Products Corporation 15i

BMS87 A Method for Developing Specifications for Building Construction—Report of Subcommittee on Specifications of the Central Housing Comn[uttee on Research,

Design, and Construction 20^ BMS88 Recommended Building Code Requirements for New Dwelling Construction With

Special Reference to War Housing * BMS89 Structural Properties of "Precision-Built, Jr," (Second Construction) Prefabricated

Wood-Frame Wall Construction Sponsored by the Homasote Co 15^ BMS90 Structural Properties of "PHC" Prefabricated Wood-Frame Constructions for Walls,

Floors, and Roofs Sponsored by the PHC Housing Corporation 15^ BMS91 A Glossary of Housing Terms * BMS92 Fire-Resistance Classifications of Building Constructions 35(5 BMS93 Accumulation of Moisture in Walls of Frame Construction During Winter Exposure.. * BMS94 Water Permeability and Weathering Resistance of Stucco-Faced, Gunite-Faced, and

"Knap Concrete-Unit" Walls * BMS95 Tests of Cement-Water Paints and Other Waterproofings for Unit-Masonry Walls 25^ BMS96 Properties of a Porous Concrete of Cement and Uniform-Sized Gravel 10^ BMS97 Experimental Dry-Wall Construction With Fiber Insulating Board * BMS98 Physical Properties of Terrazzo Aggregates * BMS99 Structural and Heat-Transfer Properties of "Multiple Box-Girder Plywood Panels" for Walls, Floors, and Roofs 15^ BMSlOO Relative Slipperiness of Floor and Deck Surfaces * BMSlOl Strength and Resistance to Corrosion of Ties for Cavity Walls • BMS102 Painting Steel 10^ • BMS103 Measurements of Heat Losses From Slab Floors 15^ BMS104 Structural Properties of Prefabricated Plywood Lightweight Constructions for Walls,

Partitions, Floors, and Roofs Sponsored by the Douglas Fir Plywood Association. . * BMS105 Paint Manual with particular reference to Federal Specifications $1. 25 BMS106 Laboratory Observations of Condensation in Wall Specimens 10^ BMS107 Building Code Requirements for New Dwelling Construction * BMS108 Temperature Distribution in a Test Bungalow With Various Heating Devices 15f5 BMS109 Strength of Houses: Application of Engineering Principles to Structural Design $1. 50 BMSllO Paints for Exterior Masonry Walls 20^ BMSlll Performance of a Coal-Fired Boiler Converted to Oil 15^ BMS112 Properties of Some Lightweight-Aggregate Concretes With and Without an Air- Entraining Admixture lOjf BMS113 Fire Resistance of Structural Clay Tile Partitions 15jJ BMS114 Temperature in a Test Bungalow With Some Radiant and Jacketed Space Heaters 25^ BMS115 A Study of a Baseboard Convector Heating System in a Test Bungalow 20^ BMS116 Preparation and Revision of Building Codes 15(iS BMS117 Fire Resistance of Walls of Lightweight Aggregate Concrete Masonry Units 20^ BMS118 Stack Venting of Plumbing Fixtures 15^ BMS119 Wet Venting of Plumbing Fixtures 200 BMS120 Fire Resistance of Walls of Gravel-Aggregate Concrete Masonry Units 15^ BMS121 Investigation of Failures of White-Coat Plasters 25)6 BMS122 Physical Properties of Some Samples of Asbestos-Cement Siding 15^ BMS123 Fire Tests of Wood-Framed Walls and Partitions With Asbestos-Cement Facings 150 BMS124 Fire Tests of Steel Columns Protected With Siliceous Aggregate Concrete 150 BMS125 Stone Exposure Test Wall 300 BMS126 The Self-Siphonage of Fixture Traps 200 BMS127 Effect of Aging on the Soundness of Regularly Hydrated Dolomitic Lime Putties 150 BMS128 Atmospheric Exposure Tests of Nailed Sheet Metal Building Materials 200 BMS129 Fire Endurance of Shutters for Moving-Stairway Openings 100 BMS130 Methods and Equipment for Testing Printed-Enamel Felt-Base Floor Covering 150 BMS131 Fire Tests of Gunite Slabs and Partitions 150 BMS132 Capacities of Plumbing Stacks in Buildings 200 BMS133 Live Loads on Floors in Buildings 200 BMS134 Fire Resistance of Concrete Floors 150 BMS135 Fire Tests of Steel Columns Encased With Gypsum Lath and Plaster --- 150 BMS136 Properties of Cavity Walls 150 BMS137 Influence of the Wash From Bronze on the Weathering of Marble 150

BMS138 Effect of Edge Insulation Upon Temperature and Condensation on Concrete-Slab

Floors 200

BMS139 Studies of Stone-Setting Mortars 200

*Out of print.