MMMII1
The program of research on building materials and structures carried on by the

National Bureau of Standards was undertaken with the assistance of the Central

Housing Committee, an informal organization of governmental agencies concerned

with housing construction and finance, which is cooperating in the investigations through a committee of principal technicians.

CENTRAL HOUSING COMMITTEE

ON RESEARCH, DESIGN, AND CONSTRUCTION

A. C. Shire, Chairman. Howard P. Vermilya, Vice Chairman.

United States Housing Authority. Federal Housing Administration.

Sterling R. March, Secretary.

Mary F. Taylor, Assistant Secretary.

Pierre Blouke, John F. Donovan,

Federal Home Loan Bank Board. Farm Security Administration.

Hugh L. Dryden, George W. Trayer,

National Bureau of Standards. Forest Service (F. P. Laboratory)

Louis A. Simon, Rollo H. Britten,

Public Buildings Administration. Public Health Service.

Luther M. Leisenring, George E. Knox,

Construction Division (War). Yards and Docks (Navy).

Edward A. Poynton, William R. Talbott,

Office of Indian Affairs. Veterans' Administration.

Wallace Ashby,

Bureau of Agricultural Chemistry and Engineering.

NATIONAL BUREAU OF STANDARDS

STAFF COMMITTEE ON ADMINISTRATION AND COORDINATION

Hugh L. Dryden, Chairman.

Mechanics and Sound.

Phaon H. Bates, Gustav E. F. Lundell,

Clay and Silicate Products. Chemistry.

Hobart C. Dickinson, Addams S. McAllister,

Heat and Power. Codes and Specifications.

Warren E. Emley, Henry S. Rawdon,

Organic and Fibrous Materials. Metallurgy.

The Forest Products Laboratory of the Forest Service is cooperating with both

committees on investigations of wood constructions.

[For list of BMS publications and directions for purchasing, see cover page III.]
UNITED ST ATES DEPARTMENT OF COMMERCE • Jesse H. Jones, Secretary

NATIONAL BUREAU OF STANDARDS • Lyman J. Briggs, Director

BUILDING MATERIALS

and STRUCTURES

REPORT BMS78

Structural, Heat-Transfer, and Water-Permeability Properties

of Five Earth-Wall Constructions

by

HERBERT L. WHITTEMORE, AMBROSE H. STANG,

ELBERT HUBBELL, and RICHARD S. DILL

ISSUED OCTOBER 1, 1941

The National Bureau of Standards is a fact-finding organization;

it does not "approve" any particular material or method of construction. The technical findings in this series of reports are to be construed accordingly.

UNITED STATES GOVERNMENT PRINTING OFFICE • WASHINGTON • I 94 I

FOR SALE BY THE SUPERINTENDENT OF DOCUMENTS, WASHINGTON, D. C. • PRICE 20 CENTS
Foreword

Interest has been expressed from time to time in the use of earth as a building material for the construction of houses as evidenced by numerous articles in popular

periodicals, and a considerable number of houses have been budt of this material. There

has, however, been a lack of technical information on the structural, thermal, and

water-permeability properties of such constructions. In order that no material be overlooked which might contribute to the development

of low-cost housing, specimens of earth walls as described in this report were constructed

in cooperation with The Office of Indian Affairs and the National Youth Administration.

The structural, heat-transfer, and water-permeability properties were determined by

methods simulating conditions to which the walls would be subjected in actual service.

The same methods have previously been used to determine the properties of masonry

and wood constructions (BMS5, BMS7, BMS25).

The National Bureau of Standards does not "approve" a construction, nor does it express an opinion as to its merits for reasons given in reports BMSl and BMS2. The

technical facts presented in this series provide the basic data from which architects

and engineers can determine whether a construction will meet definite performance

requirements.

This report is not to be construed as a general indorsement of earth constructions;

it aims to present the technical information without regard to whether the results are advantageous or disadvantageous. Because ' of the special nature of this building

material, there has been included in this report general information on methods of design

and construction prepared by the group of consultants referred to in the report. The

National Bureau of Standards has had no actual experience in the construction of earth

houses and has no information on the subject for distribution other than that contained

in this report.

Lyman J. Briggs, Director.

[ii]
Errata to accompany National Bureau of Standards Building

Materials and Structures Report BMS7S, Structural, Heat-Transfer,

and Water-Permeability Properties of Five Earth-Wall Constructions

Page 10, left column, after second line insert:

"The proportion of cement was g percent "by

weight of dry-earth mixture, approximately 6.5

percent by damp weight."

Page 21-22, delete paragrpah reading:

"Unless stated otherwise, the compressive

load was applied to the inside face (the face

nearer the load line)."

Structural, Heat-Transfer, and Water-Permeability Properties of

Five Earth-Wall Constructions

by HERBERT L. WHITTEMORE, AMBROSE H. STANG, ELBERT HUBBELL and

RICHARD S. DILL

CONTENTS

Foreword

I. Introduction.

II. Materials Earth

Cement

Lime

Sand

Mortar

Bituminous stabilizer.

Page

ii24

4

4

44

4

5

III. Specimens 5

1.

3.

IV.

Adobe-block walls 5

(a) General information 5

(b) Manufacture of block 6

(c) Control 6

(d) Construction of wall 6 Bitudobe-block walls 7

(a) General information 7

(b) Manufacture of block 8

(c) Control 8

(d) Construction of wall 8 Monolithic terracrete walls 8

(a) General information 8

(b) Construction of wall 10

(c) Control 12

4. Terracrete-block walls 12

(a) General information 12

(b) Manufacture of block 12

(c) Control 13

(d) Construction of wall 14

5. Rammed-earth walls 14

(a) General information 14

(b) Construction of wall 15

(c) Control 15 Structural properties 16

1 . Adobe-block wall DB 17

(a) Description 17

(b) Compressive load 18

(c) Transverse load- _ 19 Concentrated load 19 Impact load 20 Racking load 20

(d)

(e)

(f) 2. Bitudobe wall £>C_ 20

(a) Description 20

(b) Compressive load 21

(c) Transverse load 23

(d) Concentrated load 26

(e) Impact load 26

(f) Racking load 28

Page

28

IV. Structural properties—Continued.

3. Monolithic terracrete walls DD..

(a) Description 28

(b) Compressive load 28

(c) Transverse load 29

(d) Concentrated load 29

(e) Impact load 29

(f) Racking load 30

4. Terracrete-block wall DE 30

(a) Description 30

(b) Compressive load 32

(c) Transverse load 34

(d) Concentrated load 34

(e) Impact load : 34

(f) Racking load 34

5. Rammed-earth wall DF 35

(a) Description 35

(b) Compressive load 36

(c) Transverse load 37

(d) Concentrated load 38

(e) Impact load 39

(f) Racking load 41

V. Heat-transfer properties,, 41

1. Specimens 41

2. Heat-transfer test equipment 41

3. Heat-transfer test procedure 42

4. Heat-transfer test results 43

VI. Water-permeability properties 43

1. Specimens 43

2. Water-permeability test procedure. 44

3. Water-permeability test results- _ 44

4. Conclusions 45

VII. Additional comments 46

1. Types of construction 46

(a) Wattle and daub 46

(b) Sod houses 47

(c) Mud walling. _ 47

(d) Poured earth 47

(e) Monolithic adobe 47

(f) Adobe block. _ 47

(g) Rammed-earth 48

2. Selection of earth 48

3. Construction equipment 48

4. Protection against moisture 48

5. Construction details 49

VIII. Selected references 54

[1]
ABSTRA< 'T For the program on the investigation of low-cost house constructions, specimens representing adobe,

bitudobe, monolithic terracrete, terracrete-block, and

rammed-earth walls were constructed with the cooper- ation of The Office of Indian Affairs and the National

Youth Administration. These specimens were subjected to structural, heat-transfer, and water-permeability tests. Sixty structural specimens were subjected to compressive, transverse, concentrated, impact, and racking

loads. The transverse, concentrated, and impact loads were applied to once face. The loads simulated those

to which elements of a house are subjected in actual

service. The deformations under load and the sets after the

load was removed were measured for each increment

of load. Five heat-transfer specimens were subjected to a temperature differential that might occur in actual

service. Five water-permeability specimens were tested under conditions that simulated exposure to a heavy,

wind-driven rain.

I. INTRODUCTION

The use of earth for construction arose from

the necessity of utilizing materials at hand in a simple and direct manner. Buildings were constructed of earth by the Indian peoples of the

Southwest, who made crude adobe block and

developed methods of construction and a type of

architecture particularly suited to their needs.

With the arrival of the Spaniards, the use of

adobe became more general. Later rammedearth structures appeared along the Atlantic

Coast, and still later sod houses were built on

the plains of the Midwest by the pioneer homesteaders. The possibility that earth walls might contribute to the solution of the low-cost housing

problem led the Bureau to include this type of

construction in the BMS program on low cost house constructions. Although articles appearing from time to time in popular periodicals

have pointed out advantages of earth walls for

houses, there is a definite need for technical

information on the structural, thermal, and

water-permeability properties of such constructions. Thomas Hibben, who built rammed-earth

houses in Birmingham, Ala., under the Farm

Security Administration, offered to build test specimens with the aid of the District of Columbia National Youth Administration. The Office of Indian Affairs cooperated by assigning Elbert Hubbell, instructor of rammed earth, to supervise the construction of the specimens.

To outline a program on earth walls, experts

in the Federal Service and elsewhere were in- vited to a conference at the National Bureau

of Standards on January 3, 1940. Attending

this conference were

Thomas Hibben, National Youth Administration. Elbert Hubbell, The Office of Indian Affairs. Comdr. C. S. Stephenson, Bureau of Medicine and

Surgery, Navy Department.

T. A. H. Miller, Bureau of Agricultural Chemistry

and Engineering.

Francis Macdonald, Consulting engineer. D. E. Parsons, National Bureau of Standards.

C. C. Fishburn, National Bureau of Standards.

H. L. Whittemore, National Bureau of Standards.

A. H. Stang, National Bureau of Standards.

G. W. Shaw, National Bureau of Standards. Comdr. C. S. Stephenson (MC), U. S. Navy,

when a consultant in the Health Safety Division of the Tennessee Valley Authority, recom- mended rammed-earth houses as an economical means of improving health conditions of the

people of the Tennessee Valley. T. A. H. Miller made available for this study

extensive data on earth buildings, based on

surveys covering a period of years. Francis Macdonald has erected rammedearth houses and has investigated the properties of mixtures of earth and portlancl cement. His handbook, "Terracrete," describes proce- dures for constructing houses of this material.

All these experts served as consultants, co- operating in the planning of the program, the

conduct of the tests, and the preparation of the

report.

In addition to those present at the conference, Wallace Ashby, U. S. Department of Agriculture, who has been actively interested in the

possibilities and development of earth constructions, particularly weather-resistant coatings,

contributed valuable comments and suggestions.

Albert L. Miller, Director of the District of Columbia National Youth Administration, furnished educational-project workers to assist in building the specimens.

Many earth constructions were considered at the conference. Those selected for this program—adobe, bitudobe, monolithic terracrete, terracrete block, and rammed earth—repre- sented the earth constructions which have been

used for houses.

The earth used was a mixture containing 50

percent of clay loam and 50 percent of sand-

[2]
gravel with moisture content between 10 and 12

percent. Analysis of the mixture showed it to consist of 42 percent fine sand, 19 percent coarse

sand, 22 percent silt, 17 percent clay, and 8

percent colloids. Three kinds of tests were applied to speci- mens of each type of construction : structural,

heat transfer, and water permeability. For

the structural tests, specimens were subjected

to compressive, transverse, concentrated, impact, and racking loads, all simulating the

loads which walls of an occupied house en- counter in actual use. The deflection and set under each increment

of load were measured because the suitability

of a wall construction depends not only on its resistance to deformation when loads are applied, but also on its ability to return to its original size and shape when the loads are removed.

The weights of all five constructions were

nearly the same, ranging from 120 lb/ft3

for the bitudobe to 137 lb/ft 3 for the terra- crete block. The monolithic terracrete and

rammed-earth walls were 14 in. thick, the

block walls approximately 12 in. thick. The

adobe, bitudobe, and rammed-earth walls car- ried compressive loads up to 100 lb/in.2

; the

terracrete walls were much stronger, carrying

compressive loads up to 800 lb/in.2

, both under

eccentric loading. All of the walls withstood

transverse loads, such as are produced by the

wind, of 54 lb/ft2 or more. The performance

under impact was better than that of many

types of masonry walls, and like masonry walls

the earth walls resisted concentrated loads ex- tremely well, except near sharp corners. The

racking strengths of the adobe, bitudobe, and

rammed-earth walls were of the order of 2,000

to 3,000 lb/ft, while those of the terracrete walls were greater than 6,250 lb/ft. These

values may be compared with 2,000 lb/ft for

conventional frame construction, and 3,000 to 4,000 lb/ft for tile or cement-block construction. From the point of view of the structural

properties, all five forms of earth construction

are quite satisfactory for one- and two-story

houses, provided the work is done by persons

who have had some training and the composition and moisture content of the earth used are

controlled within suitable limits. For the heat-transfer tests, specimens were

subjected to a temperature differential that is often found in the Northern United States. The rate of transfer through earth walls is about the same as that through ordinary concrete walls of the same thickness. It is probable that the heat transfer depends on very

many variables, but the results at present

available indicate no great insulating value for

12- and 14-in. earth walls as compared with

ordinary uninsulated walls. Earth walls have

high heat capacity, which aids in reducing

fluctuations of temperature and in maintaining

a more uniform temperature. In summer, the

temperature inside an earth house does not rise to as high values as houses having walls of

lower heat capacity, but the average temperature over a long time is not affected. Earth

walls are, of course, fireproof.

For the water-permeability tests the exposed

face of a specimen was subjected to a thin film

of running water and an air pressure of 10

lb/ft 2 above atmospheric. The amount of

water applied was about 15 gal per hr per linear

ft of wall. Earth walls must be protected against the

erosion of driving rains. In the water-permeability test, an unprotected rammed-earth

wall was worn away to a depth of % in. in 40

min. Water did not penetrate the wall in this

time. The unprotected terracrete walls were

considerably better as regards erosion. The

block walls were quickly penetrated through the

mortar joints. Plain adobe was eroded to a depth of 1% in. in 40 min of exposure. The

Bureau has made no special study of protective

coatings for earth walls, but a large amount of

work has been done at the Agricultural Experiment Station of South Dakota State College.

In many climates, protection can be secured by

using an overhang on the roof. Members of the staff of the National Bureau

of Standards have had no personal experience

in the construction of complete houses of earth.

Some instruction is required and the moisture

must be held within definite limits. The fol- lowing sections II to VI, inclusive, give the

technical details of the tests and the results.

[3]
Section VII presents an account of the various

types of earth construction which have been

used; a discussion of the selection of earth;

methods of construction, including typical details; and methods of protection against the

harmful effects of moisture. This section is based on information supplied by the group of

consultants previously mentioned.

II. MATERIALS

1. Earth

A preliminary investigation indicated that a mixture of clay loam and sand-gravel, 50 per- cent of each by loose volume, would be suitable

for all test constructions. This mixture is designated "earth" in this report.

Clay loam and sand-gravel were obtained

from the Washington National Airport, south

of Washington, D. C. The sieve analysis of the clay loam, sandgravel, and earth is given in table 1 ; the hydrometer analysis in table 2 ; and the physical

constants in table 3. The hydrometer analyses

and the physical constants were determined by

the Public Roads Administration in accordance

with Standard Specifications for Highway Material and Methods of Sampling and Testing

(1938) of the American Association of State

Highway Officials.

Table 1.Sieve analysis of the earth

Table 3.

Physical constants of the earth

[Material passing IT. S. Standard Sieve No. 40]

Passing, by weight

TJ. S. Standard Sieve Clay loam Sandgravel Eartli

Hin

Percent

1009998

(IS 90

76

08

Percent

10') 99

79

.19 39

6

5

Percent

Kill Kill 92

«468

4136

% in No. 4 No. 10 No. 40 No. 140 No. 200

Table 2.

Hydrometer analysis of the earth

Particle size

Distribution, by weight

Clay loam Sandgravel Earth

Sand:

2 to 0.42 mm

Percent

2 37

33

28

16

Percent

43

49

4

4

1

Percent

1942

22

17

8

0.42 to 0.05 mm

Silt Clay___

Colloids.

Physical constant

Liquid limit

Plasticity index Shrinkage limit Shrinkage ratio Centrifuge moisture equivalent

Field moisture equivalent

Values 1

Clay loam

No.

29

1016.0

1.8

21

19

gravel

No.

Earth

No.

22

514.9

1.9 17

18

» Standard Specification for Highway Materials and Methods of Sampling and Testing (1938) of the American Association of State High- way Officials.

b NP, nonplastie.

2. Cement

The cement was Medusa Cement Co. "Medusa" brand portland cement donated by the

Portland Cement Association, Chicago, 111. The cement complied with Federal Specification SS^C-191a for soundness, fineness, time

of set, and tensile strength.

3. Lime

The lime was lime putty made by slaking

Standard Lime & Stone Co. "Washington"

brand powdered quicklime. The putty con- tained 40 to 45 percent dry hydrate by weight,

4. Sand

The sand for mortar was Potomac River

building sand. The sieve analysis is given in

table 4.

Table 4.Sieve analysis of sand in mortar for adobe,

bitudobe, and terracrete-bloclc walls

IT. S. Standard Sieve No. Passing, by weight

8 Percent100 16 88

30 53 50 11 100 2

5. Mortar

The mortar proportions were, by weight, 1 part of portland cement, 0.43 part of hydrated

lime, and 5.1 parts of dry sand; by volume, 1 part of portland cement, 1 part of hydrated

line, and 6 parts of loose, damp sand, assuming

that cement weighs 94 lb/ft 3 and dry hydrated

lime 40 lb/ft3 and that 80 lb of dry sand is

[4]
equivalent to 1 ft3 of loose, damp sand. The

materials for each batch were measured by

weight and mixed for not less than 2 min. in a batch mixer having a capacity of % ft3

. The amount of water added was adjusted to the satisfaction of the mason. A sample of the mortar was taken for each

wall specimen, the flow and the water retention were determined in accordance with Federal

Specification SS-C-181b, and six 2-in. cubes were made. Three cubes were stored in water

at 70° F and three in air near the wall. The

compressive strength of each cube was determined on the day the corresponding Avail specimen was tested. The physical properties of

the mortar are given in table 5.

Table 5.

Physical properties of mortar for adobe,

bitudobe, and terracrete-block walls

Type of wall

Structural symbol

Average moisture content

Consis- tency

as used a

Water

reten- tion »

Compressive

strength b

Air

storage Waterstorage

Adobe- ... DB

Percent

22

21

21

Percent

100

91 108

Percent

80

7880

lb/in.' 610 860

710

lb/in.'970

1, 120 950 Bitudobe DC.

Terraerete block . Average _ DE

21 100 79 730 1,010

a Determined in accordance with Federal Specification SS-C-181b.

b Determined on the day the corresponding wall specimen was tested

(age 28 days).

6. Bituminous Stabilizer

The American Bitumuls Co., Baltimore, Md..

cooperated by donating the bituminous stabilizer, by determining the earth and stabilizer

proportions, and by supplying photographs for

figures 70, 71, and 72. K. N. Cundall and W. K.

Smith assisted in making bitudobe block by

commercial-production methods.

The properties of the stabilizer, determined

by the Paint Section of the National Bureau of

Standards, are given in table 6.

Table 6.Properties of bituminous stabilizer

Property Value

Viscosity _ . .seconds

Miscibility

73 Satisfactory

0.

1

.2

.74

59

Demulsibility - percent Mixing test do Dehydration at 100° F _ _. do

Residue at 163° C do

The viscosity, miscibility with water, and demulsibility were determined according to ASTM

D244-34T, Methods of Testing Emulsified

Asphalt. The mixing test, dehydration at 100°

F, and residue at 163° C were made in accord- ance with Bureau of Yards and Docks, Navy

Department, Specification 8983. American Bitumuls Co., "Bitumuls."

III. SPECIMENS

The test specimens were built at the National

Bureau of Standards with the cooperation of

The Office of Indian Affairs and the National

Youth Administration. The same "earth,"

with or without admixtures of portland cement

or emulsified asphalt, was used in all five types

of construction selected for this study. The

range of moisture, proportions of admixture,

and test results given in this report apply to

this particular earth only.

1. Adobe-Block Walls

(a) General Information

Of the five types, the adobe-block wall is the one most widely known in the United States. Adobe block constitute a reliable building material in the Southwest, where the arid climate

is favorable to their use. Adobe construction

is common around Las Cruces, N. Mex., but even

in that area some form of exterior covering is necessary for permanent structures. Although it is customary to make the block

from suitable earth located adjacent to the

building site, some communities take all the

earth needed for this purpose from a single pit

of satisfactory material. For adobe-block

manufacture the earth should have a not too high clay content, should be easily molded when

mixed to the proper consistency, should dry

without appreciable cracking or warping, and

should produce brick of a strength sufficient for

the structural needs of the wall in which it is to be used. Straw mixed with the earth may

reduce excessive cracking.

To mix adobe satisfactorily, a method that

will pulverize the earth and distribute the

water uniformly is essential. The earths used in adobe construction should

not be confused with the heavy clays and silty

loams sometimes termed "adobe."

[5]
(b) Manufacture of Block

For the block used in these tests the adobe

mixture was agitated for 3 min. in a rotatingdrum concrete mixer (capacity 6 ft3

) shown

in figure 1, then placed in the molds shown in figure 2. The molds were made of yellow pine

2 %2 by 5 in., S4S (surfaced four sides). The

moisture content of the mixture was from 16

to 20 percent of the weight of the dry earth.

To provide a rough surface and to facilitate the drying of the block, the molds were placed

on carpet or burlap. Three full-sized blocks were molded simultaneously in one mold and

four half-sized blocks in another mold.

The adobe was thoroughly kneaded in the

mold, especially at the corners. Insufficient

kneading resulted in cavities in the lower sur- face of the block. To reduce cracking, the

upper surface of the block was smoothed flush with the mold, as shown in figure 3. Upon

removal of the mold, the upper surface of the

block was concave (to about % 6 in, J as shown

in figures 3 and 4. When the blocks could be handled without

breaking, they were turned on edge to hasten

drying. The dry blocks were stacked as shown

in figure 5. (c) Control

The essential control for adobe block is the

total moisture of the mixture. The allowable

limits are from 16 to 20 percent, by dry

weight. If the moisture is less than 16 percent, the mixture will be too stiff and will

adhere to the form; lifting the form off will

make the upper surface of the block excessively concave and will crack the lower surface. If

the moisture is greater than 20 percent, the

mixture will be too thin, and the block will

slump excessively when the form is removed

also there will be shrinkage cracks in the dried

block.

(d) Construction of Wall

The specimens were built on structural steel channels. The bed joints were formed by de- positing only enough mortar for one block at a time and were built up higher near the wall

faces than at the center. The cupped faces of

the block were laid down and the plane faces,

bottom of the block as cast, were laid up, as

[6]
shown in figure 6. The block were moved into

alinement after placing on the mortar beds, but

not much pressure could be applied on the top

surfaces without breaking them. Bearing of

the block on the bed joints was principally along

the edges of the block, and the interior portions

of the bed joints were not completely filled.

already in place and by heavily buttering the

vertical edges of this block. The next block was then placed on the bed joint and shoved

horizontally into position. Filling of the upper

portion of the joint was completed by slushing

in mortar from above. The average thickness

of the head joints was 0.95 in.

MOLD FOR. HALF BLOCK

MOLD FOR. WHOLE BLOCK

Figuee 2.

Block molds.

Full and half size. The average thickness of the bed joints was

0.51 in. at the face of the wall and 0.82 in. near

the center. The head joints were made by placing a thick

coating of mortar against the face of a block

2. Bitudobe-Block Walls

( a ) General InformaHon

Bitudobe block are similar to adobe block,

except that they contain an admixture of bi405609°—41 2
tuminous stabilizer and they must be made of

earth that is free of alkaline salts. For

bitudobe buildings it may be desirable and convenient to use a commercially prepared

stabilizer.

Figure 3.

Finishing adobe block.

It is difficult properly to mix earth, water,

and stabilizer in a pit. They should be mixed

in a pug mill. Other types of mixers can be

used only if the ingredients are accurately proportioned and if, after mixing, there remain

no unbroken clods of earth.

Many houses in the Southwest are built of

bitudobe block: and these units hare been recognized in some of the building codes of that

region. Unlike adobe, bitudobe walls are durable when exposed to driving rains.

(b) Manufacture of Block

The materials for the bitudobe block were mixed in a pug mill having a capacity of 3 ft 3

,

illustrated in figure 7. The amount of bi- tuminous stabilizer was 5.6 percent of the

weight of the dry earth. This is equivalent to

0.328 gal per block, or 0.662 gal/ft 3 of dry

earth.

The added water constituted 16 to 20 percent

by weight of the dry earth. The bitudobe

blocks were molded and dried in much the same manner as the adobe blocks. Just before beingturned on edge to complete the drying, the top

and bottom surfaces of the block as cast were

scored. The scoring is shown in figure 8 and

the method of laying in figure 9.

(c) Control

The essential controls for bitudobe block are

the total moisture of the mixture and the

amount of bituminous stabilizer. The moisture was controlled in the same way as for the adobe.

To obtain the proper amount of stabilizer per

block, the number of blocks per batch was determined by preliminary molding.

((/) Construction of Wall

The test walls were built in the same manner

as the adobe specimens. The bed joints were furrowed and were built up higher near the wall

faces than in the center. The block were laid

cupped side down. Mortar for the bed joints was placed for one block at a time. The block were moved into alinement, after being placed on the mortar bed. Bearing on the beds was

principally near the edges of the block and the

bed joints at the center of the block were not

always rilled with mortar. The average thick- ness of the bed joints was 0.39 in. at the faces

of the wall and 0.71 in. at the center. Head joints varied considerably in thickness

because of irregularities in block dimensions.

Face joints were struck.

Since the block were water repellent and

absorbed little water from the mortar, they were more difficult to lay than were adobe block and

the mortar joints set slowly. Less water was

needed in the mortar batches for bitudobe walls

than in the mortar for adobe.

3. Moxolithic Terrackete "Walls

(a) General Information

Terracrete. consisting of damp earth having

an admixture of portland cement as a stabilizer,

[S]
Figure 4.

Removal of adobe molds.

Half-sized block.

Figure 5.Stacked adobe blocks. [9]
was used in the construction of both monolithic

and block specimens.

Utilization of terracrete for wall construction

Figure 6.Construction of adobe-block wall.

is a recent development, but considerable re- search has been devoted to portland-cementstabilized earth for light -traffic highways by the

Portland Cement Association.

Resistance to weathering of terracrete mixtures may be determined by subjecting speci- mens to cycles of freezing and thawing and

wetting and drying.

The optimum moisture for the maximum

compacted density of the materials used in

these walls also was determined by the Port- land Cement Association. If the moisture

content is less than 10 percent, the terracrete cannot be properly compacted and the wall

surface will be granular and friable. If the

moisture content is greater than 12 percent,

the terracrete will adhere to the tamps and

"flow'' under blows. Therefore the allowable

limits of moisture are 10 percent and 12 per- cent by dry weight of the mixture; the optimum is 11.2 percent.

(b) Construction of Wall

The materials for the specimens were mixed

in a pug mill, shown in figure 10, and when

the water was uniformly distributed the terra- crete was ready for compacting in the forms.

The wall forms are shown in figure 11 : thev

Figure 7.Production of bitudobe mixture.

[10]
consisted of a starting form, which rested on

the steel-channel supports of the wall, and a continuation form, which was vised after the

starting form was removed. In general, the

forms consisted of side panels, B (fig. 11) ; end gates, O; tie bolts, D and E\ and alinement blocks, F. The tamps used to compact the terracrete in

the forms consisted of a steel plate 3i/2 m314- to 4-in. layer of loose terracrete was dis- tributed on the supporting channel and compacted by blows from the tamps dropping 4

to 6 in. The ramming of the first course is shown in figure 12. The top layer was then

scored to a depth of y2

in. in a checkered

design. Successive layers of terracrete were

placed in the form in this manner until the

wall was completed to within 4 in. of the top

V\/HOLE CLOCK

Figure 8.

Bitiulol>e block.

Full and half size, showing scoring.

square and y2 in - thick, welded to the end of

a 2-in. pipe 8 in. long. A 1-in. pipe 4 ft 0 in. long was connected to the 2-in. pipe by a re- ducer. Dry sand was poured into the tamp

until the weight was 15 lb. It is advisable to develop the procedure of erecting monolithic

earth walls before attempting the construction

of a building.

After the starting form was assembled, a

of the form. Each layer was about 2 in. thick. The starting form was then dismantled

and the continuation form was assembled in

position. Construction of the wall was re- sumed, and each layer of terracrete was tamped

and scored as before. After completion, the

walls were sprayed with water once a day for

3 days, and the holes in the wall left by the tie bolts were pointed with cement mortar.

[11]
4S\;2i

^

it

Figured.—Construction of bitudobe-Uock wall

(c) Control

The essential controls for monolithic terra

crete are total moisture of the terracrete mixture, the quantity of portland cement, and the

density of the compacted specimens. Samples

of the mixture were taken periodically, dried over a gas flame, the moisture content computed, and the correct amount of water added

to the subsequent batches.

4. Terracrete-Block Walls

(a) General Information

One distinct advantage of block over monolithic construction is that any defective unit

may be discarded. When the large forms are removed from a section of monolithic wall, defective portions can be taken out and replaced

only with difficulty.

The hydraulic press is an effective means of

compacting terracrete block and makes commercial production possible.

(b) Manufacture of Block

Terracrete blocks for the test specimens were made from a mixture like that used in the monoHSIuwHEBMflHmlHIHH Figure 10.

Production of terracrete mixture.

[12]
lithic terracrete specimens. The blocks were compacted in a hydraulic press, shown in figure

13, which consisted of a pump driven by a 3-hp

gasoline engine, a piston-and-cylinder assembly,

and a mold. Oil in the cylinder was compressed

to a maximum pressure of 1,200 lb/in. 2

. One

top was then securely closed, and a load was

applied to the loose mixture until the maximum

oil pressure was reached and immediately re- leased. Half blocks were made by inserting a %-in. steel separator in the mold dividing the

10%-in. dimension into equal parts.

Figure 11.

Equipment for construction of walls DD and DF.

A, tamp ; B, side panel ; C, end gate ; D and E, tie bolts ; F, alinement block;

face of the mold was mounted on the piston rod

;

the opposite face was attached to the frame of

the press. The side, top, and bottom faces of

the mold were not attached to the end faces but were free to move in the direction of motion of

the piston, so that both ends of the block could

be compacted to nearly the same density.

With only the top open, the mold was filled level full with loose terracrete mixture. The

The blocks were stacked four high and covered

with wet burlap for 3 days.

K. W. Shell, of the Portland Cement Association, assisted in the molding of the terra- crete blocks.

(c) Control

The methods of control were the same for

the terracrete blocks as for the monolithic

[13]
terracrete except that the blocks were used to determine the density of the compacted terracrete mixture.

(d) Construction of Wall

In erecting the specimen walls the bed joints were furrowed and were built up higher near

the wall faces than in the center and only

ment, the filling of the head joints was completed by slushing in mortar from above. It was difficult to completely fill the 8- by 12-in. head joints by slushing; and after demolition

of the walls, portions of the interior faces of some of the blocks were devoid of adhering

mortar, indicating that some of the head joints

had not been completely filled.

Figuee 12.Construction of walls DD and BE.

First course. G, vertical tie bolts.

sufficient mortar for one block at a time was

placed in the bed joints. The blocks were

lifted into the wall by hand or with a brick

tong and were moved into alinement by heavy

blows from a mason's hammer. The head

joints were made by plastering mortar against

the face of a block already in place and by

heavily buttering the vertical edges of this

block. After hammering the block into alineThe average joint thickness was 0.64 in. for

the bed joints and 0.48 in. for the head joints

5. Eammed-Earth Walls

(a) General Information

The mixture for rammed earth ("earth" and

water) was pulverized by turning the moistened

earth with shovels. The moisture was 11.2 percent by dry weight of the earth.

[14]
There has been some construction of rammed- earth houses throughout the country; several

buildings, including a large church near Sumter, S. C, built between 1820 and 1854, are still in good condition. A rammed-earth house near Washington, D. C, was erected 160 years ago

;

and other structures have been built more

recently.

a rammed-earth wall should not be friable and

should have adequate resistance to weathering.

In general, satisfactory earth will have a high

percentage of sand, preferably uniformly

graded from fine to coarse, and a low percentage

of clay.

Earth and water were mixed to a brushing

consistency (dagga plaster) and applied to the

Figure 13.

Hydraulic press for terracrete Mocks.

(b) Construction of Wall

The method of constructing the rammedearth specimens was like that used for the

monolithic terracrete walls.

Earth to be suitable for rammed-earth walls

should pulverize without unbroken clods. When rammed, the initial strength should be

sufficient to prevent damage during construction; the final strength should be adequate for

the particular building. There should be a minimum shrinkage of the earth while curing

to prevent cracks in the wall. The surface of

faces of the structural- and water-permeabilitytest specimens.

(c) Control

The essential control in building rammedearth walls is the total moisture content of the

mixture.

The optimum moisture content was 11.2 per- cent by dry weight. The allowable limits were

10 percent and 12 percent. Samples were taken

periodically, dried over a gas flame, the moisture content computed, and the correct amount

of water added to the subsequent batches. If

405609° —41 : [15]
the moisture were less than 10 percent, the mixture could not be properly compacted, also the

wall surface would be granular and friable, If

the moisture content were greater than 12 percent, the mixture adhered to the tamps and

"flowed" under the blows.

IV. STRUCTURAL PROPERTIES

Except as indicated, the specimens were tested

in accordance with report BMS2, which report

also gives the requirements for the specimens

and describes the presentation of the results of

the tests, particularly the load-deformation

graphs.

For the structural-property tests the constructions were assigned symbols in accordance with

table 7, and 60 specimens were assigned the

designations given in table 8.

Table 7.

Construction symbols for structural tests

Type of wall

Structural symbol Admixture Eemarks

Adobe block BB None Hand molded. Do. Hand rammed.

Machine pressed. Hand rammed.

Bitudobe block. . „. Terracrete, monolithic. Terracrete block Rammed earth,

monolithic.

DC

DD

BE

Emulsified asphalt.

Portland cement

do BF None

Table 8.

Specimen designations for structural tests, walls DB, DC, DD, DE, and DF

Specimen designation

CI, C2, CS.

Tl, T2, TS.

PI, P2, PS11,12, 13.-- Rl, R2, R8-

Load"

Compressive.

Transverse ... Concentrated. Impact"

Racking

Load applied

Upper end. Either face. Do.

Do. Near upper end.

"The impact and concentrated loads were applied to the same speci- mens, the impact load first. For the transverse and impact loads, only

three specimens were built for each load, be- cause the specimens were symmetrical about a

vertical plane midway between the faces; hence

the results for transverse and impact loads applied to one face should be identical with those

obtained by applying loads to the opposite face. The concentrated loads were applied to one face

only for the same reason. Under the compressive load the shortening was measured over the entire length of the specimen by compressometers attached to the steel plates through which the load was applied ; not

to the specimen itself, as described in BMS2.

The lateral deflections under compressive

loads were measured with a deflectometer of

fixed gage length, which consisted of a light

(duralumin) tubular frame having a leg at one end and a hinged plate at the other. The deflectometer in a vertical position was attached near the upper end of the specimen by clamping

the hinged plate to either face. The gage

length (distance between the points of support) was 7 ft. 6 in. A dial micrometer was mounted

on the frame at midlength, with the spindle in contact with the face of the specimen.

The dial was graduated to 0.001 in. and readings were recorded to the nearest division.

There ayere two deflect ometers, one near each

edge of the specimen. This method of measure- ment was used instead of the taut-wire mirrorscale method described in BMS2.

For the transverse and impact loads the

specimens were vertical. The lateral deflec- tions under transverse load were measured in

the same way as for the compressive load.

The indentation under concentrated load and

the set after the load was removed were measured, instead of the set only as described in

BMS2. The apparatus is shown in figure 14. The load was measured by means of a ring

dynamometer and was applied through the

beam, A, to which a steel disk, B, was rigidly

attached. Two dials, one of which is shown

at C7

, were supported by a crossbar, D, also

fastened to the beam. Each spindle was 8 in. from the center of the disk. The micrometers were graduated to 0.001 in., and readings were recorded to the nearest division. The

initial reading (average of the micrometer

readings) was observed under no load. A

load was applied to the disk, and the average

of the micrometer readings minus the initial reading was taken as the depth of the indentation under load. The set after the load was

removed was determined similarly.

The deformations under racking loads were measured with a right-angle deformeter, consisting of a steel channel and a steel angle

braced to form a rigid connection. In use

the channel of the deformeter rested along the

top of the specimen, with the steel angle ex- tending downward in the plane of the speci- men. Two pins passed snugly through holes

[16]
iii the channel into the top of the specimen.

A dial micrometer was attached to the steel angle. The spindle of the micrometer was in contact with the edges of the specimen. The

gage length (distance from the top of the

specimen to the spindle of the micrometer) was 6 ft 8 in. The micrometer was graduated

in 0.001 in., and readings were recorded to the

nearest tenth of a division. This deformeter

The full-sized blocks were ll l1/io by 15*4 by

41 % G in. and weighed 53 lb as laid. The halfsized blocks were 11% 6 by 7%6 by 4 1 % 6 in. and weighed 25 lb as laid. They are shown in

figure 15. The moisture content of the blocks, as laid, was 1.5 percent by dry weight. The

modulus of rupture, flatwise, on a span of 14

in. was 42 lb/in2

. The compressive strength,

flatwise, of the full -sized blocks was 500

Figure 14.

Apparatus for concentrated-load test. A, load beam ; B, steel disk ; C, dial micrometer ; D, crossbar.

was used instead of the taut-wire mirror-scale

method described in BMS2.

For the compressive tests the speed of the

movable head of the testing machine was adjusted to 0.044 in./min.

The tests were begun February 19, 1940,

and completed June 21, 1940.

1. Adobe-Block Waul ])B

(a) Description

Wall construction DB was plain adobe block

laid in cement-lime mortar. The block and

mortar were exposed on both faces.

lb/in.2 and of the half-sized blocks 265 lb/in2. The compressive strength of these blocks was

greater the greater the loaded area. An attempt was made to determine the moisture absorption of the block in accordance

with ASTM C67-37, Standard Methods of

Testing Brick.1 This was not accomplished,

because the loss of weight from erosion was

greater than the gain in weight from moisture

absorption.

Two cylinders, 4 in. in diameter and 4 in.

1 Am. Soc. Testing Materials Supplement to Book of ASTM

Standards, p. 7S-S2 (1937).

[17]
high, were made of adobe for each specimen.

The compressive strengths of the cylinders are given in table 9. Four-foot adobe-block wall specimens.—The

4-ft wall specimens were 20 courses high, except DB-T2 and T3, which were 21 courses. The specimens shown in figure 16 (20 courses high) were 8 ft 2y2 in. high, 4 ft 0% 6 in. wide, and 11 1 %6 in- thick. The texture of the

adobe walls is shown in figure 17.

WHOLE BLOCK

Figure 15.Adobe block.

Full and half size.

Table 9.- -Compressive strength of adobe cylinders for wall DB

[The. compressive strength of the cylinders was determined by the Masonry Construction Section of the National Bureau of Standards on

the day the corresponding wall specimens were tested]

Specimen Compressive

strength » Specimen Compressive

strength »

CI

lb/in. ' 198 230

200

198

188 213

223

If (Pf) b Iblin:- 203

208

183

185

175

C2 13 (P3) b C3 Rl

Tl Rf

Tt R3

TS

II (PI) b Average 200

=» Each value represents the average of 2 cylinders.

b The impact and concentrated loads were applied to the same speci- mens, the impact load first.

Eight-foot adobe-block wall specimens.—The

8-ft wall specimens shown in figure 18 were

similar to the 4-ft specimens. The specimens were 8 ft 5% in. high, 7 ft 11% 6 m- wide, and

11% in. thick. There were 21 courses in each

specimen.

(b) Compressive! Load

Specimen DB-C;2 under compressive load is shown in figure 19. The results of the compressive tests on specimens DB-C1, C%, and OS

are shown in table 10 and figures 20 and 21. The shortenings and sets in figure 20 are

[18]
computed for a height of 8 ft. The gage

length of the compressometers was 8 ft 2y2

in. Under the maximum load vertical cracks

appeared in the edges of specimens Cl and 03

In specimen 77 at a load of 37. G lb/ft2 there was failure of the bond in a bed joint

between the loading rollers, and in specimens

TB and T3 at 48.6 lb/ft 2. Greater loads inFigure 16.

Four-foot wall specimen, adobe and Mtudobe block.

near the inside face (the face nearer the load

line) above midheight. Cracks appeared similarly in specimen C<2 under a load of 12.0 kips/ft. At 13.7 kips/ft the inside face cracked

vertically near one edge. Under the maximum load many additional cracks were observed.

(c) Transverse Load

The results of the transverse tests are given

in table 10 and figure 22 for specimens DB-T1,

TV, and T3.

creased the width of the bond cracks in

the face not loaded. Under the maximum

load on T3 the blocks spallecl on the loaded

face between the loading rollers.

(<7) Concentrated Load

The results of the concentrated tests are given in table 10 and in figure 23. The concentrated loads were applied to the center of an adobe block. The set after a load

of 1.000 lb had been applied was 0.049 in. in

[19]
specimen Pi, 0.076 in. in P£, and 0.109 in. in

PS. No other effect was observed.

(e) Impact Load

The results of the impact tests of specimens

DB-Il, 12, and 13 are shown in table 10 and

figure 24. The impact loads were applied to the center

of the specimen, the sandbag striking the adobe

blocks. There was failure of the bond in a bed joint at midheight at a drop of 2.5 ft

2. Bitudobe-Block Wall DC

(a) Description

Wall DC was bitudobe block laid in cement - lime mortar. The blocks were earth with an

admixture of bituminous stabilizer. The block

and mortar were exposed on both faces. The full-sized bitudobe blocks were 11% 6 by 15y8 by 4% 6 in. and weighed 51 lb. as

laid. The half-sized blocks were lli/o by 7%

by 4y2 in. and weighed 26 lb. as laid. They

are shown in figures 8 and 9.

Figure 17.Texture of wall DB, adobe block.

in specimens II and 12 and of 1.5 ft in 13. At a drop of 10 ft on specimen II there also was a bond crack in a bed joint one course above the initial bond crack.

(/) Racking Load

The results of the racking tests on wall

specimens DB-Rl, R2, and R3 are shown in

table 10 and in figure 25. Under the maximum load each specimen

cracked diagonally from the loading plate to the stop through the blocks and mortar joints.

The price of this construction in Washington, D. C, as of July 1937, was $0.26/ft2

.

The moisture content of the blocks as laid was 2.3 percent by dry weight. The modulus

of rupture, flatwise, on a span of 14 in., was

42 lb./in.2 The compressive strength of the

full-sized block, flatwise, was 630 lb./in. 2 and

of the half-sized block 365 lb./in2

. The compressive strength of these blocks was greater

the greater the loaded area. The moisture absorption, determined in ac- cordance with ASTM C67-37, was 0.8 percent

by weight.

Two cylinders of bitudobe, 4 in. in diameter

and 4 in. high, were made for each specimen.

The compressive strengths of the bitudobe

cylinders are given in table 11.

[20]
Four-foot bitudobe wall specimens.—The

4-ft wall specimens shown in figure 16 were

8 ft 5% in. high, 4 ft 0 in. wide, and 11% in. thick. Each specimen was 21 courses high.

The texture of the wall is shown in figure 26.

(b) Compressive Load

The results of the compressive tests for wall

specimens DC-Cl, 0%, and 03 are shown in table 10 and in figures 27 and 28.

Figure 18.

Eight-foot wall specimen, adobe and bitudobe block.

Eight-foot hitudobe wall specimens.—The

8-ft wall specimens shown in figure 18 were 8 ft 5H/16 in. high, 7 ft 11"^ 6 in. wide, and 113,4

in. thick. Each specimen was 21 courses high

and was similar to the 4-ft specimens.

The shortenings and sets given in figure 27

are computed for a height of 8 ft. The gage

length of the compressometers was 8 ft 5 n/( 6 in.Unless stated otherwise, the compressive

[21]
load was applied to the inside face (the face nearer the load line).

Under a load of 11.00 kips/ft on specimen

DC-Cl there was a vertical crack in the course second from the top. At 11.72 kips/ft a verFigure 19.

Wall specimen DB-C2 under compressive

load. A, compressoineter ; B, deflectoineter.

tical crack near one edge extended through

the head joints and blocks from midheight to the top of the wall. In specimen G2 there was a vertical crack through several courses near midheight under a load of 10.00 kips/ft.

At 10.25 kips/ft there was a vertical crack in

I

I

0

12

10

Z

1 T«D»

7°

/ma

1

<Xf o

1m

1 J

m

1 coo J

lX

•uCO) U

u

OB 0 .05 JO J5

s/ior/en/ng /'n.^8ft Figure 20.

Compressive load on toall DB.

Load-f hortening (open circles) and load-set (solid circles) results for specimens DB-Cl, C2, and C3. Load applied 3.94

in. (one-third the thickness) from one face, kips per foot of actual width of specimen. The loads are in

O .05 JO J5

/ofera/ def/ecf/on fn. Figure 21.

Compressive load on wall DB.

Load-lateral deflection (open circles) and load-lateral set

(solid circles) results for specimens DB-Cl, G2, and C3. Load

applied 3.94 in. (one-third the thickness) from one face, loads are in kips per foot of actual width of specimen,

deflections and sets are for a gage length of 7 ft. 6 ir gage length of the deflectometers.

The The

the

[22]
Table 10.

Structural properties of earth walls DB, DC, DD, DE, and DF

Type of wall

Structural symbol

"Weight

Load

Compressive a Transverse; span 7 ft 6 in. Concentrated b Impact; c span 7 ft 6 in. Racking

Speci- men

Maxi- mum

load

Speci- men

Maxi- mum

load

Speci- men

Maxi- mum

load

lb

1, 000

• 1, 000

• 1. 000

Speci- men

Maxi- mum

height

of drop

Speci- men

Maxi- mum

load

Adobe block DB

Ibjft 2

121

lb/ft 3

124 (CI 13. 6113. 94

14. 56

Tl.. ..

lljjff 2 60. 0 56.9 60.0

PI 11

ft

' 10.0

' 10.0

' 10.0

Rl

1\ I JJX/Jf

2. 49 2.73 2.60 \C2 .. T2.. P2 R2

[cs TS-. IS. RS

14.03 59.0 • 1,000 '10.0 2. 61

Bitudobe block . ._ DC 117 120 \Cl 11.87

10. 87

11. 13

Tl.. 82.0 80.0

76.7

PI • 1, 000

616

• 1,000

11... I 111 1) 5.0 4.5

Rl 3.20

2.80

2.81 \C2 T2.. P2.. 12. R2

Average.-

(CS... T3-. PS. _ IS.. .. RS

11.29 79.6 2. 94

Terracrete, monolithic DD 157 135 \C1 97

' 110

110

Tl 63.9

90.0

159. 2

PI • 1. 000

« 1,000 •1.000

11. '10.0

5.5 4.0

Rl '6.25

'6.25

'6. 25 \C2 T2 P2 12 R2

Average

(CS TS PS IS RS.

106 104.0 • 1.000 '6. 25

Trrracrete block DE 134 137 \C1 119124 108

Tl 100 102

135

PI •1,000

•1,000

•1,000

11 9.0

7.5 4.5

Rl

ice T2 P2. 12. R2 '6.28

'4.80 Average

[cs... TS PS IS RS

117 112 •1,000 7 1) Rammed earth, monolithic DF 152 130 \ci.._. 17. 12

13. 07

12. 25

Tl 54. 1 67.0

57. 1

Pi • 1. 000

• 1,000

• 1.000

11 7.0

7.5 8.0

Rl 1.85 1.62

2. 00 IC2 T2 P2.. 12 R2

Average

(CS TS PS IS R3

14. 15 59. 4 « 1, 000 7. 5 1.82

a Compressive loads were applied H the thickness of the wall from 1 face,

b Diameter of load disk is 1 in.

• The sandbag weighs 00 lb. d A kip is 1,000 lb.

• Test discontinued; specimen undamaged.

' Test discontinued; specimen damaged.

Table 11.Compressive strength of bitudobe cylinders

for ivall DC

The compressive strength of the cylinders was determined by the Masonry Construction Section of the National Bureau of Standards on

the day the corresponding wall specimens were tested]

Specimen Compressive

strength * Specimen Compressive

strength a

CI

lb/in. 2 248

305

293 328

315

3'.3 2:5

12 (PS) b lb/in.' 298

270

304

283 269

CS 13(P3)b

CS Rl

Tl.. R?

T2 RS. TS

11 (PI) Average.. . .

>> 290

• Each value represents the average of 2 cylinders.

b The impact and concentrated loads were applied to the same speci- mens, the impact load first.

one edge of the specimen near the top through

one block. Under a load of 10.75 kips/ft two

courses just above midheight crushed at a cor- ner of the specimen. Under a load of 10.00

kips/ft on specimen C3, vertical cracks were

observed in head joints above midheight. At

10.91 kips/ft one corner began to crush near

the top. Under the maximum load on each

specimen, additional cracks appeared and there was more crushing.

(c) Transverse Load

Wall specimen DC-T2 under transverse load

is shown in figure 29. The results for speci- mens DC'-Tl, T2, and T3 are shown in table

10 and figure 30. In specimen DC-Tl a bond crack appeared on the face not loaded near midheight at a load of 70 lb/ft2

, and at a load of 80 lb/ft2 the specimen ruptured transversely along this

crack. Under the maximum load this crack

Avas 1 in. wide. In specimen T2 at a load of

60 lb/ft2 transverse cracks were observed in

three bed joints at midheight on the face

loaded. Under the maximum load specimen

T2 ruptured transversely between the loading

rollers; specimen T3 ruptured transversely

under a loading roller.

405609° il 4 [23]
59s

60

SO

30

^ 20

I

I0{

0'

1 • • •

/

0 0

1-0

J*/ TPc //

t-k—0- I

;;

1-

OB 0 02 0.4 06 0.8 w

def/ecf/on /'n. Figure 22.

Transverse load on wall DB.

Load-deflection (open circles) and load-set (solid circles) results for specimens DB-T1, T2, and T3 on the span 7 ft. 6 in.

02 OA 0.6

def/ecf/or? /a

Figure 24.Impact load on wall DB.

Height of drop-deflection (open circles) and height of dropset (solid circles) results for specimens DB-I1, 12, and 13 on

the span 7 ft. G in.

torn

200

—

1 % c?—

//

p

• c 0

-•—

/ •-ao )

• II —•<

OC/-€

L

/ J

T

OB

Figure 23.-

.04 .08 J2

indentation in, -Concentrated load on wall DB.

Load-indentation (open circles) and load-set (solid circles) results for specimens DB—Pl, P,i, and PS.

.02 .04

deformation

.06

/n.>,/3ff

Figure 25.

Racking load on wall OB.

Load-deformation (open circles) and load-set (solid circles) results for specimens DB-R1, R2, and RJ. The loads are in kips per foot of actual width of specimen.

[24]
Figure 26.

Texture of wall DC, bititdobe brick.

oc

0 OJ 02 /afera/ def/ecf/or? m. shortening /n./dff Figure 28.

Compressive load on wall DC.

Load-lateral deflection (open circles) and load-lateral set Figure 27.

Compressive load on ivall DC. (solid circles) results for specimens DG-Ci, C2, and Cs. The

Load-shortening (open circles) and load-set (solid circles) load was applied 3.92 in. (one-third the thickness) from one

results for specimens DC-Gl, C2, and C3. The load was applied face. The loads are in kips per foot of actual width of

3.92 in. (one-third the thickness) from one face. The loads specimen. The deflections and sets are for a gage length of

are in kips per foot of actual width of specimen. 7 ft. 6 in., the gage length of the deflect onieter.

[25]
Figure 29.

Wall specimen DC-T2 under transverse load.

(d) Concentrated Load

The results of the concentrated tests on

specimens DC-Pi, P2, and PS are shown in

table 10 and in figure 31. After a load of 1,000 lb had been applied,

the set in specimen DC-Pi was 0.121 in. and

in PS 0.056 in. Under the maximum load on

specimen P2 the loading disk punched into a cavity in the block.

(e) Impact Load

The results of the impact tests on specimens

DC-I1, 12, and IS are given in table 10 and

in figure 32. In specimen DC-I1 after a drop of 8.5 ft there was a failure of the bond in a bed joint

at midheight on the face not struck; in specimen 12, after a drop of 4.0 ft; and in IS,

after a drop of 2.0 ft. After the maximum

[26]
60

60

40

$ 20

0*>

/

• ' * •

-O-OO///o

o

—o

•capo //

i

t

D

A0 0/ 02 O.J

c/ef/ecf/on /n

Figure 30.

Transverse load on wall DC.

Load-deflection (open circles) and load-set (solid circles) results for specimens DG-T1, T2, and TS on the span 7 ft. 6 in.

fO

d

v

\

4

0*

•

• e

< 0

0

• o

>

-• o-

• 0 o

» m

/ cd—/-/

o

/ // /

/ /

0

0

•Of—o \l

if DC 0 02 0.4 0.6 c/ef/ecf/on /'n Figure 32.

Impact load on wall DC.

Height of drop-deflection (open circles) and height of dropset (solid circles) results for specimens DC—11, 12, and 13 on

the span 7 ft. 0 in.

1

soo

200

0

•

«CK

O 1

)

e-

*0 r

•0

•0

/

/

-CD

D

7Of 0 I

DC 0 .05 JO J5

me/enfa//on /n. Figure 31.

Concentrated load on wall DC.

Load-indentation (open circles) and load-set (solid circles) results for specimens DC-PI, P2, and PS.

3.5

30

V 25

f

^ 1.5 %

b 1.0

0.5

0

< 0

0 /

0

• • • o /—o

o

/

7 O

—o

77

t—

DC 0 .02 .04 .06 .03

cfeformaf/on /'n./Sf7

Figitre 33.Racking load on wall DC.

Load-deformation (open circles) and load-set (solid circles) results for specimens DC—R1, R2, and RS. The loads are in kips per foot of actual width of specimen.

[27]
height of drop on each specimen, the crack

in the bed joints extended through the wall.

(/) Racking Load

The results of the racking tests on speci- mens DC-Rl, R%, and RS are shown in table

10 and figure 33. In specimen DC-Rl at a load of 2.00 kips/ft

there was a crack in a bed joint near the top

of the wall and extending the full width. In

specimens R2 and R3 at loads of 2.59 and 1.12 kips/ft, respectively, diagonal cracks appeared

in the blocks near the center of the wall.

Under the maximum load on each specimen

there was a crack through the blocks and mortar joints diagonally from the loading plate

to the stop.

The price of this construction in Washington, D. C, as of July 1937, was $0.33/ft2

.

3. Monolithic Teeracrete Wall DD

(a) Description

Wall DD was a monolithic terracrete construction rammed by hand into wood forms.

The terracrete was earth with an admixture of

Portland cement as a stabilizer. The terracrete was exposed on both faces. One cylinder of terracrete, 8 in. in diam. and

8 in. high, was rammed for each specimen.

The compressive strengths of the cylinders are given in table 12.

Table 12.

Compressive strength of terracrete cylinders for wall DD

[The compressive strength of the cylinders was determined by the Masonry Construction Section of the National Bureau of Standards on the day the corresponding wall specimens were tested]

Specimen Compressive

strength Specimen Compressive

strength

CI

lb/in.'

1, 220

I, 280

1, 140 820

880

940 990

Jt (P2)*

Ib/in.i 680

880

1, 140 920

1, 160

C2 13 (PS)» CS Rl_. Tl m

T% R3

TS - 11 (PI)' Average 1,000

» The impact and concentrated loads were applied to the same speci- mens, the impact load first.

Four-foot monolithic terracrete wall speci- mens.—The 4-ft specimens shown in figure 34 were 8 ft 3 in. high, 4 ft 0% 6 in. wide, and

1 ft 2 in. thick.

The texture of the walls is shown in fig- ure 35. Eight-foot monolithic terracrete wall speci- mens.—The 8-ft wall specimens shown in figure

36 were similar to the 4-ft specimens. They

were 8 ft 3% 6 in. high, 8 ft 0%6 in. wide, and

1 ft 1% in. thick.

Figure 34.

Four-foot monolithic wall specimen.

(b) Compressive Load

The results for the compressive tests on DD-Cl, C@, and CS are shown in table 10

and in figures 37 and 38. The shortenings and sets given in figure 37 are computed for a height of 8 ft. The gage

length of the compressometers was 8 ft 3% in. In specimen DD-Cl a transverse crack ap-

[28]
peared on the inside face (the face nearer the

load line) near the top and one edge of the

specimen at a load of 88.0 kips/ft. Under a load of 97.4 kips/ft the inside face crushed

and spallecl along transverse lines near the top.

In specimen 02 at a load of 106 kips/ft there

Figure 35.

Texture of wail DD, monolithic

terracrete.

A, one course ; B, one layer.

was spalling along a transverse line above

midheight near one edge, and at 110 kips/ft

additional spalling on the inside face near

midheight. At the maximum load on speci- mens 01 and 02 there was more crushing and

spalling. In specimen C3 there was local crushing of one edge on the inside face at a

load of 109 kips/ft. Under the maximum load

there was crushing of the edges above midheight.

(<?) Transverse Load

The results of the transverse tests on speci- mens DD-Tl, T2, and T3 are shown in table

10 and in figure 39. Under a load of 48.6 lb/ft2 on specimen

DD-T1 there was a transverse crack between

two courses on the face not loaded, just above

the upper loading roller. In specimen T2

under a load of 62.3 lb/ft2 a transverse crack

appeared between layers at midheight on the

face not loaded. In specimen T3, at a load of

110 lb/ft2 there was a transverse crack between

layers at midheight in the face not loaded.

At a load of 120 lb/ft2 a second crack between

courses appeared in the same face and ex- tended through the specimen at a load of 140

lb/ft2

. Under the maximum load on each

specimen these cracks widened.

(d) Concentrated Load

The results of the concentrated tests on

specimens DD—Pl, P2, and P3 are shown in table 10 and in figure 40. After a load of 1,000 lb had been applied,

the set in specimens DD-Pl and P3 was 0.004

in., and in P2, 0.011 in.

(e) Impact Load

Specimen DD 13 during the impact test is shown in figure 41. The results of the impact

loads on wall specimens DD-I1, 12, and 13 are given in table 10 and in figure 42. There was no failure of specimen DD-Il;

after the 10-ft drop the set was 0.008 in. A

transverse crack appeared at midheight in

speciment 12 between layers on the face not

struck, and after a drop of 4.5 ft specimen 12

ruptured transversely between two courses. At maximum height of drop the specimen

completely separated. In specimen 13 a trans- verse crack between two courses was observed on the face not struck after a drop of 1.0 ft. At a drop of 2.0 ft this crack extended through

the wall, and at the maximum drop there was

no bond between the two pieces of wall.

[29]
(/) Racking Load

The results of the racking tests on wall

specimens DD-Rl, R@, and R3 are shown in

table 10 and in figure 43. After a load of 6.25 kips/ft had been applied, the set in specimens DD-Rl and R3 was

4. Terracrete-Block Waix DE

[a) Description

Wall DE was of machine-pressed terracrete

blocks. The blocks were laid with cement -

Figure 36.

Eight-foot monolithic wait specimen.

0.006 in./8 ft and in R2 was 0.004 in./8 ft. Xo other effects were observed.

The price of this construction in Washington, D. C, as of July 1937, was $0.42/ft2

.

lime mortar. The block and mortar were ex- posed on both faces. The full-sized terracrete blocks were 11%

by 10^4 by 8% in. and weighed 82 lb as laid;

[30]
80

60

Si 40

$ 20

0^

//

/

I1

1 ,

i 1 m Jd—

I 1

It

a

DO

160

140

\ /20

X

a/ o,2

shorfen/'ng

0.3

m./dff

• 0

• O

• o o

o»

—o

<b-f-—on

o

o

Off

Figure 37.

Compressive load on wall DD.

Load-shortening (open circles) and load-set (solid circles) results for specimens DD-C1, 02, and OS. The load was applied

4.66 in. (one-third the thickness) from one face. The loads are in kips per foot of actual width of specimen.

0 0,2 0.4- 0,6

def/ecf/on /n. Figure 39.

Transverse load on wall DD.

Load-deflection (open circles) and load-set (solid circles) results for specimens DD-Tl, T2, and T3 on the span 7 ft. 6 in.

60

(0s t

CO

I

40

I

S 20

< / /

\J

5 /

t—• (C/-I

1 / —<o/-o /

//

Jj

0D 0 0/ 0,2 O.J /a/era/ def/ection /n —

,

Figure 38.

Compressive load on wall DD.

Load-lateral deflection (open circles) and load-lateral set

(solid circles) results for specimens DD-Gl, 02, and 03. The

load was applied 4.66 in. (one-third the thickness) from one

face. The loads are in kips per foot of actual width of speci- men. The deflections and sets are for a gage length of 7 ft. 6 in., the gage length of the deflectometer.

.02 .04 .06

/ndentation /n. Figure 40.

Concentrated load on xoall DD.

Load-indentation (open circles) and load-set (solid circles) for specimens DD-Pl, P2, and P3.

[31]
the half-sized blocks were 11% by 4% by 8%

in. and weighed 39 lb as laid. Both were

pressed parallel to the 11% in. dimension.

The full-sized and half-sized blocks are shown

in figure 44. The moisture content of the blocks as laid was 6.3 percent by dry weight. The modulus

of rupture on the span of 10 in. (depth 10y±

in. and width 8% in.) was 180 lb/in2

. The

were 8 ft 3 in. high, 3 ft 1134 in. wide, and

11% in. thick. Each specimen was 11 courses high. The texture of the Avails is shown in figure 46. Eight-foot terracrete-block wall specimens.—

The 8-ft Avail specimens shown in figure 47

Avere similar to the 4-ft specimens. They were

8 ft 314 in. high, 7 ft 11% in. wide, and 1V- X/1&

in. thick.

Figure 41.

Watt specimen DD-I3 during the impact test. modulus of rupture on the span of 8 in. (depth

83/8in. and width 11% in.) was 250 lb/in2

. The compressive strength of the full-sized

blocks Avas 1,570 lb/in2

. The compressive load was applied to the 11% by lO^-in. faces

(horizontal when laid). The moisture absorption determined in accordance with ASTM

C67-37 was 7.6 percent by weight.

Four-foot terracrete-block wall specimens.—

The 4-ft Avail specimens shown in figure 45

(b) Compressive Load

The results of the compressive tests on Avail specimens DE-Cl, C2, and C3 are shown in table 10 and figures 48 and 49. The shortenings and sets given in figure 48

are computed for a height of 8 ft. The gage

length of the compressometers was 8 ft 3% in. In specimen Cl one edge on the inside face

(the face nearer the load line) began to crush

[32]
8

2

0 o.Z 0.4 0.6 def/ecf/on /n. Figure 42.

Impact load on watt DD.

Height of drop-deflection (open circles) and height of dropset (solid circles) results for specimens DD-I1, 12, and 13 on

the span 7 ft 6 in.

.02 .04

c/eformof/on

.06

/n./dff

Figure 43.Racking load on wall DD.

Load-deformation (open circles) and load-set (solid circles) results for specimens DD-R1, R2, and R3. The loads are in kips per foot of actual width of specimen.

near the top at a load of 116 kips/ft. Under

the maximum load the specimen collapsed suddenly. In specimen C2 under a load of 120

kips/ft vertical cracks appeared in several

vertical mortar joints on the inside face near one edge of the specimen; under ;i load of 123

kips/ft there was crushing of the bed joints

WHOLE BLOCK

Figure 44.

Terracrete olock.

Full and half size.

near the top on the inside face; under a load

of 124 kips/ft the edge on the inside face

crushed near the top of the specimen. In

specimen 03 a load of 105 kips/ft caused spalling at a vertical joint on the inside face near

the top; at 108 kips/ft one edge began to crush on the inside face above midheight. Under

the maximum load on specimens C£ and C3

the effects already mentioned were more pronounced.

[33]
(c) Transverse Load

The results of the transverse tests on wall

specimens DE-T1, T2, and T3 are shown in

table 10 and in figure 50.

Figure 45.Four-foot icall specimen. DE, terracrete

block. Under the maximum load on each specimen

the bond between the blocks and the mortar

ruptured between the loading rollers.

(d) Concentrated Load

Wall specimen DE-PS under concentrated

load is shown in figure 14. The results for

the concentrated tests on specimens DE-PI,

P2, and P3 are shown in table 10 and figure 51. After a load of 1.000 lb the set in specimens

DE-PI and P2 was 0.007 in.; and in P3,

0.000 in.

(e) Impact Load

The results of the impact tests on wall speci- mens DE-I1, 12, and 13 are shown in table 10

and in figure 52. In specimen DE-Il a transverse bond crack

appeared near midheight in the face not struck

after a drop of 4.5 ft; in specimen 12 after a drop of 3.0 ft ; and in specimen IS after a drop

Figure 46.Texture of ivall DE, terracrete block.

of 2.0 ft. This crack extended to the face

struck after a drop of 6.0 ft in II, 5.0 ft in 12,

and 2.5 ft in 13. Under the maximum load

each specimen was unstable when struck by

the sand bag.

(/) Racking Load

Racking-test results on specimens DE-R2

and R3 are shown in table 10 and figure 53. The results for specimen DE-Rl are not given

because they indicated that this specimen had

been damaged when it was alined in the racking frame. Evidently, forces had been exerted

accidentally which caused transverse cracks not disclosed by visual inspection before the

specimen was loaded.

Specimen Rl and R3 failed by rupture of

[34]
the bed and head joints in stepwise cracks ap- proximately along a diagonal from the point

of load application to the stop. There was no

failure of specimen R2.

The price of this construction in Washington, D. C, as of July 1937, was $0.36/ft

2

.

One cylinder of damp earth was rammed in a mold, 8 in. in diameter and 8 in. high, for

each specimen. The compressive strengths of

the cylinders are given in table 13. Four-foot rammed-earfh wall specimen*.—

The 4-ft wall specimens, shown in figure 34,

Figure 47.

Eight-foot wall specimen BE, terracrete blocl

5. Rammed-Eakth Wall DF

(a) Description

Wall DF was an earth construction rammed

by hand in wood forms. Each face was thin

dagga plaster ("earth" and water).

were 8 ft 3 n/i6 in. high, 4 ft OVs hi. wide, and

1 ft 2 in. thick. The texture of the wall is shown in figure 54. Eight-foot mmmed-earth wall specimens.—

The 8-ft wall specimens shown in figure 36 were similar to the 4-ft specimens. They were

[35]
8 ft 2i/

8

in. high, 8 ft 03/8 in. wide, and 1 ft 2 in. thick.

Table 13.

Compressive strength of rammed-earth cyl- inders for wall DF

[The compressive strength of the cylinders was determined by the Masonry Construction Section of the National Bureau of Standards on the day the corresponding wall specimens were tested]

Specimen Compressive

strength Specimen Compressive

strength

CI

lb/in.' 270

260

235 215

190

185

190

12 (P2)» WHn. 2 230

205

235

240

195

C2 IS (PS)* CS Rl

Tl R2

T2 RS

TS

11 (PI)* Average... ... 220

a The impact and concentrated loads were applied to the same speci- mens, the impact loads first.

(b) Compressive Load

The results of the compressive tests on wall

specimens DF-Cl, C2, and G3 are shown in table 10 and in figures 55 and 56. The shortenings and sets given in figure 55

are computed for a height of 8 ft. The gage

length of the compressometers was 8 ft 3

1:%6 in.

I

80

60

0<

—e • o

-W-os o

/

1 /

1 — 1 »»

/

—CrO

/ 7

u•-CD

1/ of 0 ,05 JO ,/S 20

fafero/ deflect/on /n. Figure 49.

Compressive load on wall DE.

Load-lateral deflection (open circles) and load-lateral set (solid circles) results for specimens DE-C1, C2, and C3. The

load was applied 3.92 in. (one-third the thickness) from one

face. The loads are in kips per foot of actual width of speci- men. The deflections and sets are for a gage length of 7 ft 6 in., the gage length of the deflectometer.

60

40

5 20

V)

/»

r

/•—•

~°—~/~ —O

/

o

—o / c

r —°

1

• • /

o- -f—o

/ —°~/ ( 5

/• o

-o-f-o—

J-o IV

y Of ,05 JO J5 .20 shortening /n./dff

Figure 48.

Compressive load on wall DE.

Load-shortening (open circles) and load-set (solid circles) results for specimens DE-Cl, G2, and CS. The load was applied

3.92 in. (one-third the thickness) from one face. The loads

are in kips per foot of actual width of specimen.

140

120

100

£ 60

£ 40

20<

• o —•—o

• 0

0£

Figure 50.-

.02 ,04- .06 cfef/ecf/on /n. -Transverse load on wall DE.

Load-deflection (open circles) and load-set (solid circles) results for specimens DE—Tl, T2, and TS on the span 7 ft 6 in.

[36]
indentafion /n, Figure 51.

Concentrated, load on wall DE, load

applied to outside face. Load-indentation (open circles) and load-set (solid circles) results for specimens DE-PI, P.2, and P3.

Under a load of 15.00 kips/ft on specimen

01 the inside face spalled near the top. At

16.25 kips/ft, vertical cracks appeared in one

edge of the specimen near the inside face close

to the top.

Under a load of 10.00 kips/ft on specimen

C2, vertical cracks appeared in both edges near the inside face at midheight. At 12.00 kips/ft the inside face spalled at midheight

near one edge, and at 13.00 kips/ft there was

spall ing of the inside face at midheight.

Under a load of 9.00 kips/ft, vertical cracks were observed near the top of specimen 03

on the inside face near the corners. At 11.10

kips/ft the inside face spalled at midheight

near the edge. Under the maximum load on

each specimen the effects were more pronounced.

Specimen DF-C2 after the compressive load

is shown in figure 57.

(c) Transverse Load

The results of the transverse tests on speci- mens DF-T1, T2, and T3 are shown in table

10 and figure 58.

I

V

<5 2

0

—o o—

—•—» c

/

0 //

0

tKDof vo

II

0 ,2 .4 .6 c/ef/ect/on /n. Figure 52.

Impact load on wall DE.

Height of drop-deflection (open circles) and height of dropset (solid circles) results for specimens DE—I1, 12, and 13 on

the span 7 ft 6 in.

Is.

5

0

• o

-• o

• 0

t o

DE 0 .02 .04- .06

c/eform at/on in./dft

Figure 53.Racking load on wall DE.

Load-deformation (open circles) and load-set (solid circles) results for specimens DE-R2 and Ri. per foot of actual width of specimen. The loads are in kips

[37]
Under the maximum load, specimens Tl and

T2 ruptured transversely under a loading

roller. Specimen DF-T3 cracked transversely

between a loading and a supporting roller at

48.8 lb/ft2

. The crack continued to widen

until the maximum load was reached

(d) Concentrated Load

The results of the concentrated test on wall

specimens DF-Pl, P£, and PS are shown in

table 10 and in figure 59. The concentrated load was applied on one

face near the center of the specimen. The

indentation after a load of 1,000 lb was 0.126

in. for specimen DF-Pl, 0.025 in. for P2, and

0.038 in. for PS. No other effects were observed.

0.1 0.2 shortening

0.3

in/8 ft Figure 55.

Compressive load on wall DF.

Load-shortening (open circles) and load-set (solid circles) results for specimens DF-C1, C2, and C3. The load was applied

4.G6 in. (one-third the thickness) from one face. The loads are in kips per foot of actual width of specimen.

A

Figure 54.Texture o fwall DF, rammed earth.

A, one layer.

0 0.05 0./0 0./5

lateral deflection in. Figure 56.

Compressive load on wall DF.

Load-lateral deflection (open circles ) and load-lateral set

(solid circles) results for specimens DF-C1, C2, and C3. The

load was applied 4.66 in. (one-third the thickness) from one

face. The loads are in kips per foot of actual width of specimen. The deflections and sets are for a gage length cf

7 ft. 6 in., the gage length of the deflectometer.

[38]
(e) Impact Load

The results of the impact tests on specimens

DF-U, 12, and 13 are shown in table 10 and

figure 60. In specimen II and 12 after a drop of 1.5 ft a transverse crack was observed at midheight in the face not struck, extending halfway into the wall. A similar crack appeared

in 13 after a drop of 2.0 ft. A second trans- verse crack above the first appeared in II

after a drop of 4.5 ft. In specimens II, 12,

70

\ 40

© -• o

• o —CO

• d>

m-p>

woo w

I

I

Or 0.02 0.04 0.06

deflection in. Figure 58.

Transverse load on wall DF.

Load-deflection (open circles) and load-set (solid circles) results for specimens DF-Tl, T2, and T3, on the span 7 ft. 6 in.

1000

300

=5

(J

600

400

200k

0

Figure 57.

Wall specimen DF-C2 after compressive

load.

0.04 0.08 0.12 indenfa tion in. Figure 59.

Concentrated load on wall DF.

Load-indentation (open circles) and load-set (solid circles) results for specimens DF-Pl, P2, and Pi.

[39]
6 20

deflection in. deformation in/8 ft Figure 60.

Impact load on wall DF. Figure 62.

Racking load on wall DF.

Height of drop-deflection (open circles) and height of drop-set Load-deformation (open circles) and load-set (solid circles) (solid circles) results for specimens DF-I1, It, and IS on the results for specimens DF-R1, R%, and B3. The loads are in span 7 ft. 6 in. kips per foot of actual width of specimen.
and 13, after drops of 7.0, 3.5, and 3.0 ft, respectively, the cracks extended through the

wall. The tests were discontinued when the

specimens deflected excessively under the impact loads.

(/) Racking Load

Wall specimen DF-R3 under racking load

is shown in figure 61. The results for the racking loads on specimens DF—Rl, R"2, and R3

are shown in table 10 and figure 62. In specimens Rl and R3, the first cracks ap- peared under loads of 0.80 and 1.37 kips/ft,

respectively. In each specimen the crack fol- lowed the horizontal joint between courses for

about 3 ft from the loaded edge and then

extended diagonally to the stop. Specimen Rl

cracked along a diagonal from the loading

plate to the stop at a load of 1.75 kips/ft, and

specimens R2 and R3 under the maximum load.

Under the maximum load the crack in Rl

increased in width. Specimen DF-R2 after the

maximum load is shown in figure 63. The price of this construction in Washington, D. C, as of July 1937, was $0.35/ft2

.

V. HEAT TRANSFER PROPERTIES

1. Specimens

Five specimens of earth walls were tested

in a shielded hot-box heat-transfer apparatus.

They were approximately 8 ft high by 5 ft wide and were of various thicknesses and compositions. They were allotted the laboratory

identification symbols given in the following

descriptions.

Specimen HT13 was a monolithic terracrete wall 6 in. thick. The thermal transmittance was £7=0.79, so that the heat loss through this

wall would be comparable to that through a

6-in. monolithic concrete wall, such as No. 12A,

in the 1940 "Guide" of the American Society

of Heating and Ventilating Engineers. The

conductivity, k, was 12 Btu/hr for each square

foot and for each degree Fahrenheit per inch

temperature gradient.

Specimen HTllf was similar to HT13 except

for its thickness, 12% in. The transmittance,

U, was 0.64. Even though the walls were in- tended to be similar, the conductivity, k, of

specimen HT14 was 15.2 instead of the 12.0 for the preceding wall. In consideration of

this difference, a small slab was cut from

specimen HT1J± and tested for its conductivity

in the Bureau's hot-plate apparatus No. 5. This apparatus requires specimens approximately 1 in. thick and 8 in. square. The

actual measurement of heat flow occurs on an

area 4 in. square. This hot-plate test indicated a conductivity,

A; = 11.0, which does not coincide with the re- sults of the hot-box tests of either specimen

HT13 or specimen HTl^ but the result is not

considered conclusive, for two main reasons

:

First, the small slab prepared for the test was

cut from the side of specimen HTlIf, not from

the area through which the heat-flow measure- ment was made, and it does not follow that the

composition of the small slab was representative of the entire specimen. Second, there is a

possibility that the rough treatment necessarily

accorded the small slab during its preparation

loosened the stones and other components and

resulted in the formation of openings or air

pockets within it, with a consequent reduction

in conductivity. The conductivity of walls of

this class, however, is greatly dependent on

composition, and differences as large as 4 parts

in 15 are not surprising.

Specimen HTlo was an adobe block wall

113^ in. thick.

Specimen HT16 was a bituclobe block wall

II34 in. thick.

Specimen HT18 was a monolithic rammedearth wall, 12% in. thick.

The results indicate that the heat transmittances of specimens HTlo, HT16, and HT18

were approximately equivalent to each other

and that their conductivities are in the range

expected for concrete. In general, walls with great densities have

high conductivities. The results of the heattransfer determinations of earth walls agree

in general with this relation..

2. Heat-Transfer Test Equipment

The heat-transfer tests were conducted in a shielded hot-box apparatus the arrangement of

which is shown in figure 64. During a test, heat flowed from the metering

[41]
and shield boxes, which were heated electri- cally, to the cold box, which was cooled by a

refrigerating machine. The electric energy

supplied to the metering box was closely

equivalent to the heat energy transferred

through the area of the specimen covered

by the metering box. The energy so supplied was measured with a watt-hour meter;

To promote uniformity of temperature, the

air within the boxes was given a gentle motion

by electric fans. The energy used by the fan

in the metering box was added to that introduced by the heating coils to arrive at the total energy supplied.

Air and panel-surface temperatures were measured by copper-const antan thermocouples

Fj g ure 64.- Longitudinal Section Through Heat Transfer Apparatus

and this measurement, converted into Btu and

divided by the time, the area, and the temperature difference, yielded the heat-transfer

coefficient for the specimen.

By means of the shield box, the space sur- rounding the metering box was maintained at substantially the same temperature as its in- terior except on the side in contact with the

specimen. This minimized heat exchange to or from the metering box except through the

specimen.

in conjunction with a potentiometer. Recording thermometers were used for approximate

measurements of the interior temperatures of

the boxes during the period preceding each

test when the apparatus was being brought to a state of steady heat flow.

3. Heat-Transfer Test Procedure

For testing, each panel was placed in the

apparatus in the position shown in figure 64,

and the temperature in the cold box was ad-

[42]
justed as closely as possible to 0° F and that

in the metering and shield boxes to 70° F. After a state of steady heat flow was attained,

the heat transmission of the specimen, indicated by the rate at which electric energy was

supplied to the metering box, was observed.

The results of the observations are given in

table 14.

Table 14.

Heat-transfer coefficients and test data for

earth wall specimens HT13, HT14, HT15, HT16,

and HT18

Item 1

HT15,

monolithic terra- crete

IIT14, monolithic terra- crete

IITIS, adobe

block

IITIS,

bitu- dobe

block

IITIS, ram- med

earth

Density lb/ft* 130.0 130.0 100.0 100.0 125.0 Thickness in 6 12J-6 11% 11M 12H

Observed thermal transmittance, u 0. 61 0. 51 0. 45 0. 45 0. 45 Corrected thermal transmittance, 17- . -- - .79 .64 .54 .53 .54 Thermal conductance C 2.00 1.26 .91 .88 .93 Warm surface film conductance,/! i. 8i 1. 85 1. 95 1.92 1. 87 Cold surface film conductance, fo -- 1.73 1.64 1.65 1.72 1.59 Thermal conductivity, k 12. 0 15.2 10.7 10.4 11.3

Temperature averages: Warm side: o F ° F ° F ° F ° F

Air 69. 9 69. 9 70.2 70.3 70.

1

Surface 46.2 50.4 53.8 53.9 53.3 Cold side: Air_ —0.2 —0.4 —0.3 0.0 0.0 Surface-. - - 24. 7 21.6 19.0 18. 2 19.7 Temperature differences: Air to air 70.

1

70.3 70.4 70.3 70.

1

Surface to surface 21.5 28.8 34.8 35.7 33.6 Surface to air, warm side-

.

23.8 19.5 16.3 16.4 16.8 Surface to air, cold side-.- 24.9 22.0 19.3 18.3 19. 7 Mean of air temperatures -

.

34.9 34.8 35.0 35.2 35.

1

Mean wall temperature 35.5 36.0 36.4 36.1 36.6

a The definitions of u, U, C, and k, representing the various coefficients of heat transmission, are: ii=numbor of Btu per hour transmitted through each square foot

of specimen for each degree Fahrenheit difference in temperature between the air on the two sides, as observed under test conditions. U=it corrected for a 15-mph wind outside and zero wind inside by means of the factors /i=1.65 and /o=6.00 taken from the ASHVE "Guide." C=number of Btu per hour transmitted through each square foot

of specimen for each degree Fahrenheit difference in temperature between the surfaces of the two sides as observed under

test conditions. fc=The thermal conductivity of the material, which is equal to the conductance of a slab of homogeneous material 1 in. in thickness.

In this table, the heat transmission of the

specimen is expressed in three ways. Two in- clude the effect of surface coefficients and a third is independent of surface coefficients. The first result, the observed thermal trans- mittance, u, is the number of Btu per hour

transmitted through each square foot of specimen for each degree Fahrenheit difference in

temperature between the air on the two sides as observed for the conditions described under

Heat-Transfer Test Equipment. Under these

conditions the warm surface film conductance,

7?, and the cold surface film conductance, fo, were those given in the table. Since the air velocity and its effect on the

two surfaces of the specimen may not be the same for different tests, it seemed desirable to correct the observed thermal transmittance to a standard condition of a 15-mph wind outside

and zero wind inside. This was done to obtain

the corrected thermal transmittance, U, by cor- recting the observed thermal transmittance, u, by means of the factors /2=1.65 and /o = 6.00, as recommended in the ASHVE "Guide."

The thermal conductance, C, of the specimen

also is presented, and this represents the number of Btu per hour transmitted through each

square foot of specimen for each degree Fahrenheit difference in temperature between the

surfaces of the two sides observed under the

test conditions.

The thermal conductivity, h, is equal to the

conductance of a slab of homogeneous material

1 in. in thickness.

4. Heat-Transfer Test Results

The results of the heat-transfer tests on five earth-wall constructions are given in table 14.

VI. WATER-PERMEABILITY

PROPERTIES

1. Specimens

The specimens used for water-permeability

tests were about 50 in. high, 42 in. wide, and

of the same thickness as the corresponding

structural specimens. They were supported on

a single course of brick resting on a steel- channel section. The brick course contained

a copper flashing so that water penetrating the

specimen could be collected and the rate of

flow measured. When laid, the bitudobe block

absorbed little water from the mortar, whereas

the adobe blocks were highly absorptive. The

water content of the materials used in the

specimens and both the consistency and the

water retentivity of the mortars are given in table 15. The specimens were aged at least

1 month indoors before being tested.

[43]
Table 15.

Construction data for earth walls

Specimen No.

B299 (DB)

B298 (DC)

B289 (DD)

B-'ss (

I ) K

B286 (DF)

Type of wall

Adobe block -. Bitudobe block...

Terracrete, monolithic

Terracrete block Rammed-earth, monolithic

is a

a.3

- z —

O t-. 7T, CB O ffl

3 i; >

Pet. 3.9

1.6

10. 8 4.7

Mortar 1

Pet. 10289

119

Ptf.7879

75

i Federal Specification for Cement, Masonry, SS-C-181b.

2. Water- Permeability Test Procedure

The water-permeability test is described, in

BMS7, Water Permeability of Masonry Walls,

as the "heavy rain test." The specimens were

supported on metal skids and clamped into

position so that the exposed face formed one

side of a pressure chamber. An air pressure

of 10 lb/ft 2 above atmospheric was maintained

in the chamber, and water from a perforated

tube was sprayed on the top of the exposed

face at the rate of 40 gal/hr for 1 clay, except

where otherwise noted.

The following observations were made on the

specimens during the test: Time for the appearance of moisture (dampness) and of visible

water on the back of a specimen ; time for the

leakage of water from the flashing at the back

of a specimen and the maximum rate of leak- age; extent of damp area on the back at the

end of 1 day. The ratings of performance in

the water-permeability test are arbitrary and

are based on the assumption that visible water,

extensive damp areas on the back, or leakage

through a wall would damage plaster applied

directly to the wall or would injure the finished

interior of a building. The following ratings

have been devised for specimens that would

not be damaged or eroded by the test exposure : Good : No visible water on back of wall in 1 day. Less than 50 percent of the wall area damp in 1 day. No leaks through the wall. Fair: Visible water on back of wall in more

than 3 hr and less than 1 day. Rate of leak- age, less than 1 liter/hr.

Poor : Visible water on back in 3 hr or less. Rate of leakage less than 5 liters/hr.

Very poor: Rate of leakage greater than 5

liters/hr.

3. Water-Permeability Test Results

Data obtained from the permeability tests are given in table 16.

Table 16.Permeability test data for earth walls

Specimen No.

B299 (DB)___ B298 (DC).._ B289 (DD)_._ B288 (DE)__. B286 (DF)..

Type of wall

Adobe block Bitudobe block.

Terracrete, monolithic. Terracrete block _ Rammed earth, monolithic.

Time to failure as indicated by

a

hr

0. 03 4.00

20. 00

0.03 M

3 a

hr 0.03

18. 00

0.03 M

hr 0.02

Liters 2

00

0. 05

0

VP.

F.G.

P. VP.

1 Duration of tost 0.7 hr.

As can be noted from figures 65 and 66, the

faces of both the rammed-earth and the adobeblock specimens were deeply eroded. The tests were stopped after an exposure period of 40

min because the drains were becoming clogged

with material washed from the faces. There was no penetration of water through the

rammed-earth specimen.

The monolithic terracrete specimen was

found to be the least permeable. Moisture

penetrated the terracrete at construction joints

between layers of compacted material.

The specimen containing the water-repellent

bitudobe block was less permeable than the

specimen containing either adobe or terracrete

block. Water penetrated all unit constructions only through the joints between the blocks

and the mortar. The water permeability of

these specimens appeared to be influenced by

the water absorption of the blocks when laid. Data from tests on brick masonry specimens

made at the National Bureau of Standards

subsequent to the publication of BMS7 indicate

that a difference in the water absorption of

brick at the time of laying had an important

effect on the permeability after erection of

otherwise similar specimens. It was found,

as is indicated in the tests on earth-block

[44]
specimens, that the lower the water absorption

of the units when laid the lower the permeability of the specimens.

Portland cement, are highly resistant to the

penetration of moisture from wind-driven

rains.

Figure 65.

Rammed-earth water-permeability specimen after test.

4. Conclusions

Walls of rammed earth or of adobe block

require adequate surface treatment to protect

them from the erosive effects of wind-driven

rains.

Rammed-earth walls 14 in. thick, containing

Walls of earth block, with or without admixtures of portland cement or emulsified asphalt, are permeable at the mortar joints to winddriven rains. The degree of permeability

increased with increase in the absorptive properties of the block at time of laying.

[45]
VII. ADDITIONAL COMMENTS

1. Types of Construction

Seven methods of earth construction are common in the United States. Adobe is most

widely known; rammed earth is the strongest

(a) Wattle and Daub

Osiers and small poles are woven into a basket-like frame which is smeared and daubed

with plastic earth, the operation being repeated

until all contraction cracks resulting from drying are filled. This method, called "wattle

V

Figure 66.

Adobe-block water-permeability specimen after test.

and most enduring of the nonstabilized types.

These two methods indicate possibilities for

improvement by applying modern methods and

equipment for selecting, conditioning, and

placing the earth. A brief description of the seven methods is given so that their relations

to each other may be more evident.

and daub," is rather extensively practiced in

the Southwest for skeleton walls of sheds or

for lean-to additions to low-cost houses.

While at best a primitive method, it provides

the very poor of arid regions with a means of

erecting inexpensive buildings. Its life depends on the type of soil, the care taken to

[46]
exclude water, and the rigidity of the framework.

(b) Sod Houses

Lacking lumber for houses, the pioneers of

the Great Plains resorted to the erection of

sod walls. The heavy prairie vegetation produced a close-matted sod that was cut on the

site into blocks 2 ft or more long, a foot or more wide, and 4 to 6 in. thick. These were

laid like brick, with the grass side down; the

length of the sod blocks determining the thick- ness of the wall. The roofs were relatively

flat and of poles and slabs covered first with

tar paper and then with two thicknesses of sod,

grass side down. The interior surfaces were trimmed plumb and then plastered smooth with

earth. Well-built "soddys" lasted from 10 to 20 years, depending on upkeep and on the

dryness of the climate, a new roof being

required occasionally.

While soddys were comfortable, they were

at best makeshifts. This form of construction does not permit improvement of technique

by applying newer building practices. However, sod could be piled against the walls of

farm buildings and on roofs as protection

against field fires.

(c) Mud Walling

In mud walling, earth of a plastic consistency is worked between studs of a frame building. Settlers in Pennsylvania utilized earth

in this manner not only as a protection against

cold winds but also as a safeguard from the

flaming brands thrown by Indians in border

clashes. It frequently was used for chinking

log houses. The Mexicans in the Southwest

build cajon walls (meaning "a narrow box")

by erecting 2- by 4-in. studs, nailing lath to both sides, and filling in the enclosed space

with stiff earth. Exterior walls built with

occasional studs and filled with plastic earth

and stone, sometimes lime, were at one time

common in parts of Europe and have been

known in this country. Temporary boards are fastened to the studs to facilitate filling, then

are replaced with conventional wood siding.

It is questionable whether this method has

application except for interior partitions and

for that portion of end walls protected by

gables. Earth so employed has the advantages of occupying little space and providing

insulation against sound and temperature.

(d) Poured Earth

In Martinsburg, W. Va., a house was built

in 1887 by pouring thin earth mixtures between

movable forms 6 to 12 in. high, and this

method has been employed in other localities. The earth in each course is permitted to settle until sufficiently firm, when the forms are

raised for successive courses. Excellent walls

12 to 18 in. thick are built in this way, but

the method is slow and messy. Unless conditions are very favorable, contraction cracks

are almost inevitable, when the wall dries,

and must be filled with earth or mortar.

Rocks 12 in. in diameter and smaller stones are sometimes imbedded in the wet earth. The

poured-earth method of construction does not

call for the heavy labor required for rammed

earth and might become more common if asphaltic stabilizers were used to increase the

weather resistance. The vacuum method for

extracting moisture in concrete might be uti- lized to expedite consolidation and reduce

shrinkage.

(e) Monolithic Adobe

The Indians and missionaries of the Southwest built monolithic walls of earth mixed

with native grasses or charred twigs and water

to the consistency of dough. This is the tra- ditional method followed in England for

building cob. The earth and straw are mixed

by tramping it into a uniform mass. This

adobe mixture is piled onto the wall in layers

6 to 24 in. high and 18 and 30 in. thick and

left until sufficiently dry to bear the weight

of succeeding layers. Earth that slumps be- yond the wall lines in each course is cut plumb

before adding other courses. Sometimes temporary boards support the earth. The exteriors frequently are plastered with the same

earth mixtures or with lime mortar. Many

old churches and other large buildings built by

this method are still in use.

(/) Adobe Block

Adobe block, with or without straw or other

bonding material, is the form of earth con-

[47]
struction most widely found at present. While

restricted to arid sections, other building materials are so scarce in these localities that

adobe block fill a very definite need.

(g) Rammed Earth

Rammed earth and adobe block are the two

basic forms of earth construction which are now being studied. Rammed earth has been

built in monolithic and in block form, depending on preference, economy, and equipment at hand. More judgment than actual skill is re- quired in working with rammed earth.

The technique should be mastered before

the erection of a major building with monolithic Avails is attempted. The difficulty of

manipulating the heavy forms and the fact

that mistakes of soil selection and ramming

cannot be so readily detected as in block construction add to the problems of building

monolithic walls. Rammed earth is more durable than adobe

and offers many opportunities for further development by the application of engineering

methods.

2. Selection or Earth

Until recently the earth for construction

merely consisted of a suitable material (sometimes vegetative binder or stones being added)

mixed with water to obtain consistencies,

varying from a slurry to one about the dryness

of brown sugar, permitting pouring, molding,

or ramming, depending on the method selected

for building the wall.

Virtually the same kind of earth is suitable

for all methods of building earth walls. Earth

12 to 18 in. below the surface is likely to be more uniform in composition and be freer of

undesirable roots or humus (which should be

avoided, especially for rammed earth) than

surface earth. Contrary to popular belief, the

earth must not have a high clay content ; however, there must be a sufficient amount of clay

(15 to 30 percent) to properly knit or bond

the other ingredients. Unfortunately, "adobe"

is a term applied to certain heavy clays and

silty clay loams which contain much too high

a percentage of clay to make satisfactory adobe

block. These earths should not be confused

with adobe construction.

For construction purposes, earth is classified mechanically by size of particles as sand, silt, and clay, and its suitability for structural use

is then judged by the proportionate amounts

of these materials. Very fine clay is colloidal

in character; that is, it seems to have a gluelike or gelatinous property that readily takes

up moisture—this is the material in soils that

causes so much trouble due to its instability.

When dry it absorbs a large amount of moisture and expands. Upon subsequent drying

colloidal clay warps and contracts excessively,

thereby causing cracks. Sand reduces shrinkage but excessive amounts of it prevent proper

bonding. Too much silt produces a soft wall

that erodes readily. When the earth contains an excess of clay, it can often be conditioned

by adding sand ; and sandy earths can be con- ditioned by adding clay. The best sand is one graduated between particles the size of a nut

and fairly fine, as in concrete practice, so that

the particles will interlock and be bound to- gether with the colloidal material. However,

too much large material is undesirable. The

graduation of particle sizes in the earth described herein conveys a general idea of a wellgraded soil.

3. Construction Equipment

Concrete mixers and pug mills are effective for mixing earth and water for earth constructions. The block press developed at the Haskell Institute and the pneumatic rammer serve

to decrease the labor involved and to increase

the rate of construction of rammed-earth and

terracrete walls. Many rigging and scaffolding

arrangements are advantageous when handling

forms for monolithic constructions. Portable

elevators of the kind used for loading coal

trucks might prove practical for placing earth

in forms, especially where duplication or mass

production is practiced.

Builders who specialize in bitudobe, rammed

earth, and terracrete could economically employ equipment. However, further experiments

are needed.

4. Protection Against Moisture

Probably the outstanding weakness of earth

walls is their susceptibility to damage by moisture. Moisture must be guarded against in

[48]
any type of earth wall, for the wall will not

last if water is absorbed. Moisture is absorbed

by capillarity from the ground through a per- vious foundation, by splashing, and from a leaking roof. Rains against a wall, however,

damage it very little. Where the intervals

between rains are not long enough to permit

drying, especially in freezing weather, a water- proof coating is needed. Rivulets from the

roof or rain gutters cut a plain-earth wall like a knife and are to be guarded against. Protection against erosion from sand driven by high

wind is necessary in some regions.

The water-permeability tests indicate that

the plain, or untreated, earth walls need a protective covering. The stabilized-earth spec- imens have sufficient resistance to moisture ex- cept in the case of faulty mortar joints.

Concrete, brick, or rubble-stone foundations,

with a tar coating on top, or slate or asbestos

shingles imbedded in mortar, prevent water

rising by capillarity. Such protective foundations should be at least 12 in. above the sur- rounding ground level to prevent absorption

of splashing water. Unless made of local stone laid by cheap labor, masonry foundations

may prove expensive because they must be

at least as thick as the earth walls. There is real need for studying the durability of stabilized-earth foundations and other economical

types.

Little difficulty should be experienced in keeping the roof tight; and this should be

done, for water is more insidious here than at the foundation. A sheet of tar paper laid in

asphalt, slate imbedded in mortar, or a 6-in. concrete belt-course applied to the top of the

wall afford fairly certain protection.

The cheapest coating is a wash that will not

change the color of the walls when applied

directly. Linseed oil so far appears to be the

most promising. The next cheapest would be

coatings similar to whitewash or calcimine.

Rammed-earth buildings in Birmingham, Ala.,

have been coated with such preparations, some

of which seem to be giving good results.

5. Construction Details

To build enduring earth walls is one thing;

to build an earth house is another. Practices

common to all masonry building should be

understood and followed in addition to the

technique of constructing earth walls. Maximum economy is effected by carefully

planning the order and details of construction

and by selecting a design of simple lines with

Figure 67.

Typical details of monolithic wall, flat-roof construction.

few angles. More than one story is structurally feasible by making the lower wall sec- tions thick ; however, the cost of building walls

higher than one story is considerable.

Earth in the form of blocks presents fewer

difficulties than monolithic walls because defective blocks can be discarded, suitable weather

is not quite so vital during construction, window and door openings are not different from

[49]
wall sections, and there are no heavy forms

to manage. If there are few angles, openings,

or protruding details, rammed earth and

terracrete have advantages in being stronger

and more enduring and often being lower in

cost than other constructions.

More thought given to details is required

for monolithic than for block walls. Where

forms are used, a type should be selected that

Window and door lintels must be strong

when the earth is to be rammed over them.

One good plan is to make the openings of such

a height that the lintels come directly under

the wall plate. The wall over lintels may be

built of block if the high-lintel arrangement is not satisfactory.

Wide eaves and gables afford protection to the wall and are advisable if there is any

Figure 68.Typical details of block wall parapet-roof construction.

will be rigid and that can be easily handled.

It is important to consider how the forms may

be shifted, to reduce the number of resettings as much as possible. Considerable labor can

be saved by making the wall sections between

openings of uniform length so that a box-form

may be used. Walls less than 14 in. thick are

difficult to ram, although a thinner wall might

have sufficient structural strength.

doubt as to the permanence of the exterior

coating. In adobe-block and other unit construction, a reinforced concrete cap continuous

around the wall just under the plate is desirable.

Fireplaces and chimneys are commonly built

of adobe block but must be lined with firebrick

and flue lining. Except for the difficulty of

ramming thin walls, fireplaces and chimneys

[50]
[51]

could be made of rammed earth or monolithic

terracrete. In the judgment of builders experienced in

all types of earth construction, the typical

details shown in figures 67, 68, and 69 represent satisfactory methods of construction.

The flat roof shown in figure 67 is a simple

construction based on the practice of placing

lintel is made sufficiently strong to support

the wall above the window or door opening.

A solid sill is not so essential in the block

wall for offsets can be accommodated by frac- tions of block. The floor cast integrally with

the foundation for the wall solves the floorjoist problem. An impervious layer of tar paper or slate imbedded in asphalt protects the

Figure 72.

Interior vie-w of bitudobe house, Southivest architecture.

no solid wall above the lintel. A solid window

sill is favored for a monolithic wall. The

floor joists are carried on a wood support

attached to the inside face of the concrete foundation. An impervious layer of tar paper

is placed between the foundation and the wall. The parapet roof shown in figure 68 is typical of the architectural style suitable to adobe or bitudobe construction. A continuous

concrete cap protects the top course of block.

The roof joists are supported on a wood plate

inserted in the wall. The reinforced-concrete

wall from moisture in the foundation. A

suitable nonloadbearing partition is indicated.

The sloping roof shown in figure 69 suggests

the more conventional construction. Rafters

and ceiling joists are supported on a wood

plate. The reinforced concrete lintel and solid

sill are recommended for the monolithic wall. The reinforced concrete lintel is especially

necessary when any solid wall is carried over

the window or door openings. Floor joists

may be supported on a wood plate on the

foundation. Material must be taken from the

[53]
wall to allow the joists to bear on the plate;

and this removal should be done as soon as practicable after the wall is started, for the

wall soon becomes exceedingly hard. Tar

paper or some other impervious material is placed on the foundation to protect the wall.

Two residences in Phoenix, Ariz., are shown

in figures 70 and 71, illustrating respectively

the typical Southwest architecture, with terra- cotta tile roof, and a modernly styled, shingled

roof house. Bitudobe block laid in bitudobe

mortar were employed in both houses.

Figure 72 presents an interior view of the

house shown in figure 70. The exposed ceiling

beams, rustic wall surface, and simple window

openings are typical details of this construction. The walls can be plastered with either

bitudobe or cement mortar.

The drawings of the specimens were pre- pared by E. J. Shell and G. W. Shaw of the

Building Practice and Specifications Section

of the National Bureau of Standards, under

the supervision of V. B. Phelan.

The structural properties were determined

by the Engineering Mechanics Section, under

the supervision of H. L. Whittemore and A. H.

Stang, and by the Masonry Construction Section, under the supervision of D. E. Parsons.

The chemical properties of the bituminous

stabilizer were determined by the Paint Section, under the supervision of E. F. Hickson.

The heat-transfer properties of the constructions were determined by the Heat Transfer

Section, under the supervision of M. S. Van

Dusen.

The water-permeability properties were determined by the Masonry Construction Section,

under the supervision of D. E. Parsons.

The following members of the professional

staff assisted:

E. S. Cohen W. G. Hoback J. S. Rimmer

A. H. Easton D. C. List L. R. Sweetman

C. C. Fishburn M. F. Peck H. L. Weiss

A. Heiter P. H. Petersen

VIII. SELECTED REFERENCES

1. Adobe Block (Plain and Stabilized)

Year

1930.

1910.

1934.

1920.

1935.

1936.

1937.

1938.

1939.

1940.

1926.

Year

1941. J. D. Long, Adobe construction, Calif. Agr.

Exp. Sta. Bui. 472.

A. G. Carpenter, How the world is housed,

American Book Co.

J. W. Adams, Adobe as a building material

for the plains, Colorado Agr. Exp. Sta. Bui. 174. T. A. H. Miller, Adobe or sun-dried brick, U. S. Dept. Agr. Farm. Bui. 1720.

J. W. Sjogren and J. W. Adams, Adobe

brick for farm buildings, Colorado Agr.

Exp. Sta. Bui. 308. Harold C. Schwalen, Effect of soil texture upon the physical characteristics of adobe

bricks, Univ. Arizona, Agr. Exp. Sta. Bui. 58. C. L. McKesson, Soil stabilisation with

emulsified asphalt, Highwy. Research

Board Proc. 15th Annual Meeting.

G. F. Ashley, How to build an adobe home,

Calif. Homes, 15, 22 and 23. Harold C. Schwalen, Adobe construction,

Agr. Eng. 17, 9; 387-389.

Specifications for construction with asphalt

stabilized bricks, acceptance test program

for bitudobe brick, Am. Bitumuls Co., Baltimore, Md.

2. Terracrete Ray W. Crum, Soil-cement mixtures for roads, pt. II, Highwy. Research Board

Proc. 17th Annual Meeting.

Frank T. Sheets and Miles D. Catton,

Basic principles of soil-cement mixtures,

Reprint Engr. News Record, 120, No. 25, June 23. Soil-cement roads, Portland Cement Assoc.

Const. Hand.

Francis Macdonald, Terracrete building with rammed earth-cement, Chestertown, Md.

Tentative method of test for moistures- density relations of soil-cement mixtures,

ASTM Designation D558-40T.

Tentative method of wetting and, drying

test of compacted soil-cement mixtures,

ASTM Designation D559^0T.

Tentative method of freezing and thawing

test of compacted soil-cement mixtures,

ASTM Designation D560-40T.

3. Rammed Earth

T. A. H. Miller, Report on the condition of rammed-earth buildings, Sumter, S. €., U. S. D. A., Bur. Agr. Chem. and Engr.,

December. Houses of rammed-earth construction, U. S. D. A., Resettlement Adm. (Farm Security

Adm.)

[54]
Year

1936.

1937.

1938.

1940.

1916.

1925.

Ralph L. Patty, Relation of colloids in soil to its favorable use in pise or rammedearth walls, South Dakota State Col., Agr. Exp. Sta., Dept. of Agr. Engr. Bui.

298. M. C. Betts and T. A. H. Miller, Rammcdearth walls for buildings, U. S. Dept.

Agr., Farm. Bui. 1500. Ralph L. Patty and L. W. Minium, Rammedearth walls for farm buildings, South

Dakota State Col., Dept. of Agr., Exp.

Sta. Bui. 277. Statement on condition of rammed-earth

houses, U. S. Dept. Agr., Farm Security

Adm., June 6.

4. General

Spectator (London), Mar. 11. Louise W. Mears, A. M., The sod house. Journal of Geography, vol. 14, p. 385-389.

F. Hardy, Cohesion in colloidal soils, Journal Agr. Sci. (England) 15, No. 4, p. 430-433.

Year

1926. R. M. Gray, A mud ranch house designed

by a California engineer, Agr. Engr.,

7 : 276. 1920. Clough William Ellis, Cottage building in

cob, pise, chalk, and clay, Charles Scribner's Sons, New York.

1930. George J. Bouyoucos, A comparison of the hydrometer method and the pipette

method, for making meclianical analyses

of soils, with new directions, Journal American Society of Agronomy, 22, 747751.

1938. Charles E. Kellogg, Soil survey manual,

U. S. Dept. Agr., Misc. Pub. 274. 1939. H. G. Scherecht, Improve physical properties of clays by controlling pH values,

Brick and Clay Record, March, p. 18-21.

1940. Ralph L. Patty, Paints and plasters for rammed-earth walls, South Dakota Agr.

Exp. Sta. Bui. 336. 1924. Recommended mmimum requirements for masonry wall construction, Bureau of Standards, U. S. Department of Commerce, BH6.

Washington, June 11, 1941. o

[55]

BUILDING MATERIALS AND STRUCTURES REPORTS

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The following publications in this series are available by purchase from the Superintendent of Documents at the prices indicated:

BMSl Research on Building Materials and Structures for Use in Low-Cost Housing 10(6 BMS2 Methods of Determining the Structural Properties of Low-Cost House Constructions.. 10^ BMS3 Suitability of Fiber Insulating Lath as a Plaster Base 10* BMS4 Accelerated Aging of Fiber Building Boards 10* BMS5 Structural Properties of Six Masonry Wall Constructions 15* BMS6 Survey of Roofing Materials in the Southeastern States 15(6 BMS7 Water Permeability of Masonry Walls 10* BMS8 Methods of Investigation of Surface Treatment for Corrosion Protection of Steel 10* BMS9 Structural Properties of the Insulated Steel Construction Co.'s "Frameless-Steel" Constructions for Walls, Partitions, Floors, and Roofs 10* BMS10 Structural Properties of One of the "Keystone Beam Steel Floor" Constructions Sponsored by the H. H. Robertson Co 10(4 BMS11 Structural Properties of the Curren Fabrihome Corporation's "Fabrihome" Constructions for Walls and Partitions 10* BMS12 Structural Properties of "Steelox" Constructions for Walls, Partitions, Floors, and Roofs

Sponsored by Steel Buildings, Inc 15* BMS13 Properties of Some Fiber Building Boards of Current Manufacture 10* BMS14 Indentation and Recovery of Low-Cost Floor Coverings 10* BMS15 Structural Properties of "Wheeling Long-Span Steel Floor" Construction Sponsored by

Wheeling Corrugating Co 10* BMS16 Structural Properties of a "Tilecrete" Floor Construction Sponsored by Tilecrete Floors, Inc - 10* BMS17 Sound Insulation of Wall and Floor Constructions 10* BMS18 Structural Properties of "Pre-Fab" Constructions for Walls, Partitions, and Floors Sponsored by the Harnischfeger Corporation 10(4 BMS19 Preparation and Revision of Building Codes 15(6 BMS20 Structural Properties of "Twachtman" Constructions for Walls and Floors Sponsored by

Connecticut Pre-Cast Buildings Corporation 10* BMS21 Structural Properties of a Concrete-Block Cavity-Wall Construction Sponsored by the National Concrete Masonry Association 10(6 BMS22 Structural Properties of "Dun-Ti-Stone" Wall Construction Sponsored by the W. E. Dunn Manufacturing Co 10(6 BMS23 Structural Properties of a Brick Cavity-Wall Construction Sponsored by the Brick

Manufacturers Association of New York, Inc 10* BMS24 Structural Properties of a Reinforced-Brick Wall Construction and a Brick-Tile CavityWall Construction Sponsored by the Structural Clay Products Institute 10* BMS25 Structural Properties of Conventional Wood-Frame Constructions for Walls, Partitions,

Floors, and Roofs 15(6 BMS26 Structural Properties of "Nelson Pre-Cast Concrete Foundation" Wall Construction

Sponsored by the Nelson Cement Stone Co.,. Inc , 10(6 BMS27 Structural Properties of "Bender Steel Home" Wall Construction Sponsored by The

Bender Body Co 10* BMS28 Backfiow Prevention in Over-Rim Water Supplies 10* BMS29 Survey of Roofing Materials in the Northeastern States 10* BMS30 Structural Properties of a Wood-Frame Wall Construction Sponsored by the Douglas

Fir Plywood Association 10* BMS31 Structural Properties of "Insulite" Wall and "Insulite" Partition Constructions Sponsored by The Insulite Co 15* BMS32 Structural Properties of Two Brick-Concrete-Block Wall Constructions and a Concrete- Block Wall Construction Sponsored by the National Concrete Masonry Association. 10*

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

[Continued from cover page in]

BMS33 Plastic Calking Materials. _ 100 BMS34 Performance Test of Floor Coverings for Use in Low-Cost Housing: Part 1 100 BMS35 Stability of Sheathing Papers as Determined by Accelerated Aging 100 BMS36 Structural Properties of Wood-J* rame Wall, Partition, Floor, and Roof Constructions with

"Red Stripe" Lath Sponsored by The Weston Paper and Manufacturing Co 100 BMS37 Structural Properties of "Palisade Homes" Constructions for Walls, Partitions, and

Floors Sponsored by Palisade Homes 100 BMS38 Structural Properties of Two "Dunstone" Wall Constructions Sponsored by the W. E. Dunn Manufacturing Co 100 BMS39 Structural Properties of a Wall Construction of "Pfeifer Units" Sponsored by the Wisconsin Units Co . 100 BMS40 Structural Properties of a Wall Construction of "Knap Concrete Wall Units" Sponsored

by Knap America Inc 100 BMS41 Effect of Heating and Cooling on the Permeability of Masonry Walls 100 BMS42 Structural Properties of Wood-Frame Wall and Partition Constructions With "Celotex"

Insulating Boards Sponsored by The Celotex Corporation 100 BMS43 Performance Test of Floor Coverings for Use in Low-Cost Housing: Part 2 100 BMS44 Surface Treatment of Steel Prior to Painting 100 BMS45 Air Infiltration Through Windows 100 BMS46 Structural Properties of "Scot-Bilt" Prefabricated Sheet-Steel Constructions for Walls,

Floors, and Roofs Sponsored by The Globe-Wernicke Co 100 BMS47 Structural Properties of Prefabricated Wood-Frame Constructions for Walls, Partitions,

and Floors Sponsored by American Houses, Inc 100 BMS48 Structural Properties of "Precision-Built" Frame Wall and Partition Constructions

Sponsored by the Homasote Co 100 BMS49 Metallic Roofing for Low-Cost House Construction 100 BMS50 Stability of Fiber Building Boards as Determined by Accelerated Aging 100 BMS51 Structural Properties of "Tilecrete Type A" Floor Construction Sponsored by the Tile- crete Co 100 BMS52 Effect of Ceiling Insulation on Summer Comfort 100 BMS53 Structural Properties of a Masonry Wall Construction of "Munlock Dry Wall Brick"

Sponsored by the Munlock Engineering Co 100 BMS54 Effect of Soot on the Rating of an Oil-Fired Heating Boiler 100 BMS55 Effects of Wetting and Drying on the Permeability of Masonry Walls 100 BMS56 A Survey of Humidities in Residences 100 BMS57 Roofing in the United States—Results of a Questionnaire 100 BMS58 Strength of Soft-Soldered Joints in Copper Tubing 100 BMS59 Properties of Adhesives for Floor Coverings 100 BMS60 Strength, Absorption, and Resistance to Laboratory Freezing and Thawing of Building

Bricks Produced in the United States 150 BMS61 Structural Properties of Two Nonreinforced Monolithic Concrete Wall Constructions.. 100 BMS62 Structural Properties of a Precast Joist Concrete Floor Construction Sponsored by the

Portland Cement Association 100 BMS63 Moisture Condensation in Building Walls 100 BMS64 Solar Heating of Various Surfaces 100 BMS65 Methods of Estimating Loads in Plumbing Systems 100 BMS66 Plumbing Manual 200

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 of Floor Coverings for Use in Low-Cost Housing: Part 3 150 BMS69 Stability of Fiber Sheathing Boards as Determined by Accelerated Aging 100 BMS70 Asphalt-Prepared Roll Roofings and Shingles _ 150 BMS71 Fire Tests of Wood- and Metal-Framed Partitions 200

BMS72 Structural Properties of "Precision-Built, Jr." Prefabricated Wood-Frame Wall Construction Sponsored by the Homasote Co ; 100 BMS73 Indentation Characteristics of Floor Coverings 100 BMS74 Structural and Heat-Transfer Properties of "U. S. S. Panelbilt" Prefabricated Sheet-Steel Constructions for Walls, Partitions, and Roofs Sponsored by the Tennessee Coal, IrOn & Railroad Co 150 BMS75 Survey of Roofing Materials in the North Central States 150 BMS76 Effect of Outdoor Exposure on the Water Permeability of Masonry Walls 150 BMS77 Properties and Performance of Fiber Tile Boards 100 BMS78 Structural, Heat-Transfer, and Water-Permeability Properties of Five Earth-Wall Constructions ....... 200