0 /! 0 0

NATIONAL BUREAU OF STANDARDS REPORT

EVALUATION OP REFRACTORY QUALITIES OP CONCRETES

FOR JET AIRCRAFT WARM UP* POWER CHECK*

AND MAINTENANCE APRONS '

by

W. L. Pendergast, E. C, Tuma, R. A. Clevenger

and S* F. Holley

QUARTERLY REPORT

ON

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
U. S. DEPARTMENT OF COMMERCE

Sinclair Weeks, Secretary

NATIONAL BUREAU OF STANDARDS

A. V. Astin, Director

THE NATIONAL BUREAU OF STANDARDS

The 6Cope of activities of the National Bureau of Standards is suggested in the following listing

of the divisions and sections engaged in technical work. In general, each section is engaged in

specialized research, development, and engineering in the field indicated by its title. A brief

description of the activities, and of the resultant reports and publications, appears on the inside

of the back cover of this report.

Electricity and Electronics. Resistance and Reactance. Electron Tubes. Electrical Instru- ments. Magnetic Measurements. Process Technology. Engineering Electronics. Electronic

Instrumentation. Electrochemistry.

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Technology. Length. Engineering Metrology.

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Inorganic Chemistry. Electrodeposition. Gas Chemistry. Physical Chemistry. Thermochemistry. Spectrochemistry. Pure Substances.

Mechanics. Sound. Mechanical Instruments. Fluid Mechanics. Engineering Mechanics.

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Radio Standards. High Frequency Standards. Microwave Standards. • Office of Basic Instrumentation • Office of Weights and Measures
NATIONAL HUREAIJ OF STANDARDS REPORT

NBS l®^©JE€T NBS REPORT

0903-21-Ii.428 March 31, 1955 4055

QUARTERLY REPORT

ON

EVALUATION OP REFRACTORY QUALITIES OP CONCRETES

FOR JET AIRCRAFT WARM UP, POWER CHECK,

AND MAINTENANCE APRONS

by

W. L. Pendergast, E. C. Tuma, R. A. Clevenger

and S. F. Holley

Refractories Section

Mineral Products Division

Sponsored by

Department of the Navy

Bureau of Yards and Docks

Washington, D. C.

Reference: NT4”59/NY 420 008-1

NBS File No. 9.3/H34-C

Approved

R. A. Heindl, Chief

Refractories Section

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU IF STANDARDS

The publication, reprintii

unless permission Is obtal 25,D,C, Such permlssio

cal ly prepared if that ag

Approved for public release by the

Director of the National Institute of

Standards and Technology (NIST)

on October 9, 201 5.

t, is prohibited

ds, Washington

as been specifir or its own use,
\
QUARTERLY REPORT

ON

EVALUATION OP REFRACTORY QUALITIES OF CONCRETES

FOR JET AIRCRAFT WARM-UP, POWER CHECK,

AND MAINTENANCE APRONS

TECHNICAL REQUIREMENTS

The technical requirements for the concretes designed

with dense aggregates are the same as those given in NBS

Report 3012, dated December 31* 1953*

The technical requirement for the concretes designed

with lightweight aggregates are: (1) they must develop a

flexural strength of 6f>0 psi after curing for 28 days in

the fog-room; (2) the maximum cement content shall not

exceed nine sacks per cubic yard.

1. INTRODUCTION

The objective of the investigation is the determination

of the physical properties of concretes that will evaluate

their suitability for use in jet aircraft warm-up, power

check, and maintenance aprons.

2. MATERIALS: PREPARATION AND TESTING

2.1 Cements

The lack of storage facilities has made it necessary

to procure additional lots of cement, at intervals, during

the course of this investigation, to replenish the stock

of the three types of cement used in this project. During

this quarter an additional 16 sacks of portland cement were
1
- 2 - purchased. This lot , as well as preceding ones of the same

brand, came from the same plant, and each shipment was

tested" in accordance with the Federal Specification

applicable to the particular type of cement. Because there

is no Federal Specification for high-alumina hydraulic

cement, this material was subjected to the same physical and

chemical tests as those applying to Type I portland cement.

Observations of the thermal length changes from room

temperature to approximately 1200 P C were made on the three

neat cements. The specimens, which measured 7«25 x 1,25 x

1.25 inches, were cured for 28 days in the fog-room and

dried for 18 hours at 105°C before testing. Observations

of thermal length changes were made also on the same specimens

after two preheatings at approximately 1200°C. The specimens

were weighed and measured after the 28-day fog-room curing

and again after the first and third preheatings. The

specimens were stored in a desiccator between successive

heat treatments to prevent possible changes in the cement.

2 1 2 Aggregates

A second shipment of 2500 pounds of the lightweight

aggregate, "Rocklite , ” was received. A screen analysis was

made of a combined sample taken from the coarse, medium, and

fine grades of this material.

¥

By the Concreting Materials Section, Mineral Products

Division, National Bureau of Standards.

- 3

-

A second shipment of 50 pounds of the lightweight

aggregate, "Kenlite," having a top size of +3/k in* has

been received. The top size ordinarily furnished by the

manufacturers is +l/2 in. The larger aggregate was

requested because the trial concretes designed with this

aggregate failed to develop the required flexural strength

and the results indicated that an increase in the top size

might bring the strength up to the specified minimum.

The sintered slag furnished by the Armour Research

Foundation of Illinois Institute of Technology is a product

resulting from coal burning. It is that part of the ash

that fuses and drips to the bottom of the ash pit. It is

crushed, agglomerated, and sintered. The sintering

temperature affects the properties of the resulting product

materially. The first, a small shipment was sintered at

approximately 2200°F at the Institute laboratory. The

second, a 10-ton shipment, was processed by contract, the

sintering temperature used was approximately 2500°F.

2,3 Concretes

Nine one-cubic foot trial batches and five l5-cubic

foot final batches of conorete were designed and mixed.

Specimens fabricated from these batches were cured and

tested, if the curing period was complete.

Six of the trial mixes were designed with the lightweight aggregate, "Rocklite". Four of the six contained

Portland cement, one portland pogzolan, and one the highalumina hydraulic cement, "Lumnita"

.

- 4 -

One trial mix was designed using portland cement,

crushed building brick, and white marsh sand. The sand,

-30 to -100 mesh, was substituted for the usual crushed

brick fines of corresponding sizes. The results from this

one trial batch, together with those for certain trial

batches reported in KBS Keport 3012, December 1953* were

used as the basis for designing a l5-cubic foot final batch

of concrete containing portland cement, coarse sizes of

crushed building brick, and fine sizes of white marsh sand.

One l5~cubic foot final batch of concrete was designed

containing portland cement and coarse sizes only of calcined

Kentucky flint clay together with fine sizes -30 to -100

of white marsh sand. The results obtained on the trial

batches of this concrete, appearing in KBS Keport 3399,

June 1934 ^ were used as a guide in designing this mix.

The information obtained on two trial batches of

sintered slag ooncrete made this quarter, as well as that

on nine trial batches given in KBS Keport 3^55, December

1954 5 was used in designing three final batches of concretes

of 15-cubio feet each. Five sets of specimens were made

of the three concretes containing the sintered slag and

either portland, portland pozzolan, or high-alumina hydraulic

cement. One set of these specimens was cured in the fogroom for 28 day3 and tested. Four sets of each concrete

were cured for seven days in the fog-room and stored for
\
- 5 -

21 days under ordinary laboratory conditions. One of these

four sets was tested after this curing treatment and another

set after having been heated at 250 °C; the third set has

been heated at 500°C S and the fourth at 1000 P C. The specimens

exposed to the latter two heat treatments have not as yet

been tested.

The thermal length changes from room temperature to

approximately 1100 c'C were observed on specimens of the

three concretes containing sintered slag.

3. RESULTS AND DISCUSSION

3 » 1 Cements

The results of the acceptance tests, of the portland

cement received this quarter compared with those made on

earlier shipments, indicate that the uniformity between

shipments to be very good.

The thermal length changes of the three neat cements,

from room temperature to ll80 p C are shown graphically in

Figure 1. One set of curves shows the length changes of

specimens of the three cements after curing for 28 days in

the fog-room and drying for 18 hours at 105°C. The second

set of curves shows the length changes up to ll80 P C of the

same specimens after preheating twice to approximately ll80 p C.

The curves showing the length changes observed on the

three cements that were cured and dried at 105°C indioate

that a slight expansion occurred from room temperature to

100°C with no appreciable length change between 100 P C and

200 P C

Length

Change,

Percent

Figure I

- 6 - The portland cement contracted rapidly between 200 c C

and 700°C (2»7 percent),, This length change probably

resulted from the loss of water which was indicated by

previously reported differential thermal analysis /~”lJ.

A decided decrease in rate of contraction occurred between

J00 e C and 900°C. This is about the temperature range in

which the decomposition of calcium oarbonate occurs. A

rapid shrinkage occurred again between 900 c C and ll80°C

(2o9 percent) that was due probably to sintering.

The portland pozzolan cement had a rapid shrinkage

from 200 P C to 600 c C associated with water loss f~1Ja Expansion occurred between 600 o C and 1000°C, indicating the

resultant linear change of the inert material (pozzolanic)

and the contraction of the cement. Shrinkage occurred again

between 1000 °C and ll80 c C which may be attributed to sintering.

The thermal length changes of the high-alumina cement

were suggestive of the work reported by R. A. Heindl and

Z. A. Post /~2_7» A rapid rate of shrinkage occurred

between 200 P C and IjOO^C, an expansion between 4^0 c C and

800°C, a slight shrinkage between 800°C and 900°C, and a

rapid shrinkage* attributed to sintering, occurred again

between 1100°C and ll80°C.

All three cements contracted on cooling, the rate

being comparatively uniform and the magnitude of the same

order as the shrinkage during heating.
\
7

The curves, showing the length changes of the same

three specimens of cements during the third heating to

ll80 p c indicate that after such heat exposure all three

cements have a low and uniform rate of expansion (see

figure 1). The heat treatments at ll80°c apparently reconverted the cements to a sintered material containing glass

and bearing little resemblance to the original cements

The thermal expansion of the product resulting from heating

the high-alumina hydraulic cement was somewhat lower than

that resulting from the heating of the port land or Portland

pozzolan cement

„

The weight losses and the linear shrinkages of the

three neat cements after heating are given in Table 1.

A high percentage of the weight loss occurred during drying

at 110°C. All but a very small percent occurred during the

first heating to ll80°C. A very small percentage of the

total shrinkage occurred during drying at 110°C. Most of

the remaining total shrinkage occurred during the first

heating to 1180°C. The over-all shrinkage measurements

made by the extensometer method compare favorably with those

determined in the thermal expansion apparatus*

3 * 2 Aggregates

The results of preliminary screen analyses of the

second shipment of Rocklite indicated that there is a

considerable variation from the first shipment in the

Table

1.

Weight

Loss

and

Linear

Shrinkage

of

Neat

Cements

after

Heat

Exposures. 0I—I

05

t>p

CD -P

Cl •H

r-1 PPO

rCj +3

05

CO0

-pp • a 0

•H

p

1A 05 iH P0 P Ph O b

<P 0 • • •P bD bu no P P i—1 1 •H 0 o p p P o P p p o o op o B

rr* & cO -p o o o o p © p p p o « l o 0

bU bO P p o o p P p 0

>» Ph

CO cO 0

<13 TO

O P 1 1 Q -p co CO o

OJ OJ o p 1—1

-p

pp ‘r 1 0 0 -p P

-p •P cO <p <H T3

cC CO T3 0 0 i—1

-p ,p •PO

.p -p 0 O

bD bO 0 a

•H P P © 0 0

iH 0 P P ©

© 0 0 B

rP •H

-P -PO 0 0 P P P PH o O 0 0 B 73 T3 •H 0 00 W0 O0 £fH

05 CO Ph CQ CQ C/0 i—I ! OJ | cO| j

- 8 - gradation of the three lots, namely coarse, medium, and

fine sizes in which this material is marketed. This

variation in sizes between the two shipments will necessitate

screening and recombining the entire 25>00 pounds in order

to obtain the desired grading?

The small shipment of coarse Kenlite aggregate

furnished as +3/4 contained only 5>0 percent of this size.

The producer of this material informed us that his

production methods are geared to produce below -3/4 inch

and suggested that there might be some difficulty in

procuring such a coarse aggregate in many sections of the

country.

The thermal length changes, of the building brick

aggregate, are shown graphically in Figure 2 and for

convenience are repeated in Figures 3 and 4« The curve

showing the length changes from room temperature to 1000 P C

is smooth except for a slightly increased rate in the

temperature range of 5$Q Q C to 600 c C which indicates the

presence of small amounts of free quartz. Although the

brick has a softening point of approximately 1300°C it

started bloating before 1100°C and continued to do so to

the top test temperature. The cooling curve shows a low

and uniform rate of shrinkage. A permanent expansion of

3<>8 percent was indicated because of the bloating of the

material

.

Length

Change,

Percent

l

Figure 2

Length

Chonge

,

Percent

Temperature , °C

Figure 3
' *

'
Length

Change,

Percent

Figure 4

- 9 -

3 • 3 Conc retes

Table 2 gives the composition, some properties of the

fresh concretes, together with the flexural strengths of

specimens of trial batches designed with the lightweight

aggregate, "Rocklite”, sintered, slag or building brick.

For the concrete containing the Rocklite only two of

the twelve trial batches, six of which were included in

NB-S Report 3855 # December 1954 # developed a flexural

strength of 600 psi. In designing these twelve trial mixes

the ratio of coarse to fine aggregate was increased from

55/45 to 65/35. The percentage of the top sizes of the

coarse aggregate was increased until the concrete became

too harsh to place well. Reductions in the water-cement

ratio and air-entraining agent were made. However, an

examination of the beams after breaking show aggregate

fracture to be nearly 100 percent.

In the design of the trial batch P-B-WM-A, the substitution of the white marsh sand for the fines of the building

brick aggregate permitted a reduction in the water -cement

ratio which in turn resulted in diminishing the air content.

The sonic modulus of elasticity after 21 days fog-room

curing of the beams fabricated with this concrete Indicated

that the required flexural strength will develop during a

28-day curing period.

Table

2.

Properties

of

Fresh

Concretes,^

Trial

Mixes

Remarks

Cured

Concretes

mostly

aggregate

fracture,

few

airvoids mostly

fractured

aggregate;

few

airvoids few

pull-outs,

mostly

aggregate

fracture;

some

airvoids 1 1 i

505£

pull-outs

50%

fractured

aggregate o

T> 1

DO

Flexural Strength

28-day

Fog-room

Cur:

psi

600 o <Q

-dlltsI1TJl1 <Q 3NO

^o|

Remarks

Fresh

Concrete

excess

of

water

bleeding good

workability

harsh

but

placeable

good

placeability

good

placeability

slightly

harsh

but

placeable

very

good

very

good

harsh;

fair

placeability

Water

Cement Ratio 0.37 0.40 0.29

Ro

0.35 0.35 3O

0.51

0.39-

Weight

of

Fresh

Concrete §1

95.00 o-4

toO'

95.60

00*001 3R

95.60

131.90 oCAoCA 01

Slump

inches 00*9 2.00 2.00 6.00

O o

(V

3.00

O

CV

1.00

ts0) Pi -P -P T3 COO o a x: tca

vO 3

-4O O' 5

ca

<A to CA

CV > o U 2 s < O

cv ca ol rH rH

1=o o

•po

Picoo coo

Pio

-p

42 o

CAJR

CO •a

to

35.8 38.2 -4i38.7 35.7 -4

CA

O

lA

-4

45.8 33.3

Vinsol

Resin

by

Weight

of

Cement 8o

none ooo

0.005 ooo0.005

lA8o

none 0.005

Cement

Content

sacks/yd^

of

concrete j

Co

to s<6

8.61

R

CO

8.98 8.65 7.82 7.90 o

cC

O 1 o to „ 2 £ C nj tt O -P O M -:

0.74 Elo Ro

vOb-o . :

0.67 o ;:

1.56 rH

n

rH

U -H

O

O a^^.5 :

0.90 :

1.07 :

1.05 Ono :1.01 :1.09 :1.38 :

1.55 ol i 4" °1

rH rH iH rH rH rH rH rH rH

Identification^ CCS tL

Ts1 %CnJ 4

<Aw

pc' i %2 ft.

P-SS-I Z-SS-I J,1 CU

The

second

letters: R»

Rocklite, a

lightweight

expanded

shale,

coated;

SS»

sintered

slag; B=

crushed

building

brick;

WM=

white

marsh

sand.

The

third

letters; =

batch

identification,

the

superscript 3

indicating

that

the

aggregate

was

used

in

the

same

proportions

as

received

but

with

increases

in

the

+3/U

to

+3/8

inch

sizes.

If

no

superscript

appears

with

the

batch

identification

letter

the

Bureau

of

Yards

and

Docks'

gradation

was

used.

White

marsh

sand

was

substituted

for

the

parent

aggregate

from

+50

to

-100

sizes.

Dash

indicates

tests

have

not

been

completed.

10

Table 3 gives the properties of the final batches of

fresh concrete designed with sintered slag, crushed

building brick, or calcined Kentucky flint clay.

In the concretes using either crushed building brick

or calcined flint clay, white marsh sand was used for the

-30 to -ICO mesh fines as in the trial batches. The

results given in Table 3 for the several properties of

the three individual mixes of five cubic feet each for

the same concretes indicate the variation that may be

expected with laboratory controlled mixing.

The results of the completed tests on concretes

designed with sintered slag and either portland, portland

pczzolan, or high-alumina hydraulic cement, are given in

Table 4 . All three concretes developed the required

flexural strength after a 28-day fog-room curings

Figures 2, 3 and 4 show the length changes during

heating, from room temperature to approximately 1200 °C? fcr

concretes designed with crushed building brick and either

high-alumina cement, ’’Lumnite," portland cement, or

Portland pozzolan cement, respectively. Although the

curves describing the length changes of these three concreres

were shown in Figure 6, NBS Report 3705? September 1954?

they are shown again for comparison with the length changes

of the cement and the aggregate.

Table

3.

Properties

of

Fresh

Concretes,^

Final

Mixes

Remarks

Cured

Concrete

mostly

pullouts 50^

pull-outs

50£

fractured

aggregate

CJ -ri ©

-P © -P ?

& & 3 s 2 III

Flexural Strength

28-day

l \

i

-h 3 & S

?

*

50

lT\ O CMcRemarks

Fresh

Concrete

slightly

harsh

but

placeable

very

good

slightly

harsh

but

placeable

very

good do do

slightly

harsh

but

good

placeability do do

— i

harsh

but

placeable;

slight

bleeding

do do

harsh

but

placeable

placed

well

slightly

harsh

harsh

but

placeable

Water

Cement Ratio 0.39 0.39 0.39 cn -4 -4-4-4 odd 0.39 0.37 0.37 3 3 3

o do odd 3 3 3

Weight of

Fresh

Concrete ^ S 8 S, \ d pH | 3 3 3133.30 133.00 133.00

CM CM O'

CO, lf\ CO 3 3 3

138.55 139.39 139.82

CM CO CM

CM O C'- S i 3

Slump

inches 1.50 5.50 2.25 2.50 3.00 3.50 2.50 2.00 2.00 2.00 1.75 2.00 1.00 2.25 1.00 I

t l

© a. e V.

CM O CsO IC\ d -4 c'MCM U~\ O'* r- cm c^-

O'* O'* -4

Air

Cor

Me

the

Gravimetric

1

1.88 1.36 3.20 1.24 1.79 1.58 -4 ir\ o 3- <0 v\

CM CM CM 3 Si 3

o'* CM d

-4 IAN CM

1

Water

Content

gals/yd^

ol

concrete

41.0 41.0 40.0 O o 3 3 ^

36.0 35.1 35-0

-oj- Oo~\ o*\ oS

35.3 36.1 33.8

Vinsol

Resin

by

Weight

j

of

Cement 2 0.005 0.005 0.005 0.005 0.005 0.005

none none none 0.005 0.005 0.005 0.015 0.015 0.015

Cement

Content

©

-p2

c

o

tH o lA t>- O H

(r\ O' O' ^

.3*

00 CM H

-T IA IA

oo d co

-4 C'- O'

Cr3 CO co co d

° d t*- d

CO CO CM -O OM U*\ d d d

Proportion

by

Weight

Cement

to

Coarse

and

to

Fine

Aggregate -

H

*’ o o H U *d H

H

K

pH O O

OO "O TJ

c'i pH

pH 1

:

1.53

:

1.52

do do

1

:

2.72

:

1.23

do do

cn

O'* pH O O £

^ o

CM

pH

.3

-P3

•Ha

ts©a

T 7 ?

? f

?

Z-SS-l

Z-SS-2 Z-SS-3

pH cm O'*

i i i I J J

a. a. cu

P-C-WM-1 P-C-WH-2 P-C-WM-3

© i

a9

I

c

.3

'©l 'ol

Table

k-.

Properties

of

Cured

and

Heat-Treated

Concretes

i*'©

-P6ONNata*0 i 0 P ac3

UO 0 ,c

tr\ +>

«H 0 ^ 0 ct5 >

fl) Qi

h

C*\ M-H c* « -5 o I § go a §a H

OO -P 2V£ I bO*H MOlH ? O <H -H

<H f* +> _ >5 O 0) .9 3^.2 oCM

fc\ ta

<s I o a to < m t>>NO 3

a! ir\ rH

•d

U CM Oh 4) C-+

ch5 -P

n) ^C toi 0 0 4-5 0

CM -S $ -p i—I -C 0 o"\ £ IS -9 g 3 H .-US <H 13o b H!h c«3 0

•r~i© 0 p 0 ©

*H COO

H

H

-P -P 0 0 0

11 - The curves showing the linear changes that were observed

in the concretes designed with sintered slag as the aggregate

and either portiand, portland pozzolan, or the high-alumina

hydraulic cement are shown in Figure The shape of the

curves indicating the length changes and the total expansion

from room temperature to 800°C is quite similar to the curves

describing the length changes observed in the concretes

designed with crushed building brick. However , from 800°C

to the top temperature, namely 1070°C, rapid expansion

occurred in all three concretes. This concrete is the only

one of those tested having permanent expansion after cooling*

In order to learn whether the t hemal length changes up

to 1C00 P C of a concrete could be predicted when the thermal

length changes of its ingredients are known, calculations

were made based on data for building brick aggregate and

the hydraulic cements. The results indicate that in the

concrete containing the portland cement no reliance whatsoever

can be placed in the computed values. The observed value at

lOOO^C was O.L). percent expansion, the value obtained by

computation indicated a shrinkage of 0«1| percent. The

corresponding values for the concretes containing Lumnite and

portland pozzolan cements were 0*55 versus 0 0 percent, and

0*35 and 0,3255 expansion, respectively. Though the values

for the last two concretes at 1000°C are in reasonably good

agreement, the plotted curves of the calculated values are

quite erratic when compared with those developed from

observed values

Length

Change

,

Percent

+ ZD T AGGREGATE " Sintered Slog

Temperature,°C

Figure 5
’ ••

,

’

‘

• - .
REFERENCES

r\J N.B.S. Report l8l7> Figure 4*

/ 2J Refractory Castables: II, Some Properties, and

Effects of Heat-Treatment, Journal American

Ceramic Society, Vol. 37 * No, 5? May 1954

Figure 2.

THE NATIONAL BUREAU OF STANDARDS

Functions and Activities

The functions of the National Bureau of Standards are set forth in the Act of Congress, March

3, 1901, as amended by Congress in Public Law 619, 1950. These include the development and

maintenance of the national standards of measurement and the provision of means and methods

for making measurements consistent with these standards; the determination of physical constants and properties of materials; the development of methods and instruments for testing materials,

devices, and structures; advisory services to Government Agencies on scientific and technical

problems; invention and development of devices to serve special needs of the Government; and the

development of standard practices, codes, and specifications. The work includes basic and applied

research, development, engineering, instrumentation, testing, evaluation, calibration services, and

various consultation and information services. A major portion of the Bureau’s work is performed

for other Government Agencies, particularly the Department of Defense and the Atomic Energy

Commission. The scope of activities is suggested by the listing of divisions and sections on the

inside of the front cover.

Reports and Publications

The results of the Bureau’s work take the form of either actual equipment and devices or published papers and reports. Reports are issued to the sponsoring agency of a particular project

or program. Published papers appear either in the Bureau’s own series of publications or in the

journals of professional and scientific societies. The Bureau itself publishes three monthly periodicals, available from the Government Printing Office: The Journal of Research, which presents

complete papers reporting technical investigations; the Technical News Bulletin, which presents

summary and preliminary reports on work in progress; and Basic Radio Propagation Predictions,

which provides data for determining the best frequencies to use for radio communications throughout

the world. There are also five series of nonperiodical publications: The Applied Mathematics

Series, Circulars, Handbooks, Building Materials and Structures Reports, and Miscellaneous

Publications.

Information on the Bureau’s publications can be found in NBS Circular 460, Publications of

the National Bureau of Standards ($1.25) and its Supplement ($0.75), available from the Superintendent of Documents, Government Printing Office. Inquiries regarding the Bureau’s reports and

publications should be addressed to the Office of Scientific Publications, National Bureau of

Standards, Washington 25, D. C.