NATIONAL BUREAU OF STANDARDS REPORT

5714

TESTS OF PRESTRESSED CELLULAR SLABS

(Slabs Nos. 20 through 27)

Arthur F. Kirs te In

Report to

Bureau of Yards and Docks

Department of the Navy

<NBS>

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
THE NATIONAL BUREAU OF STANDARDS

Functions an«l Activities

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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,

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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 projec t or program. Published papers appear either in the Bureau’s own series of publications or in the

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Inquiries regarding the Bureau’s reports should be addressed to the Office of Technical Information, National Bureau of Standards, Washington 25, D. C.
NATIONAL BUREAU OF STANDARDS REPORT

WBS PROJECT m8 REPORT

1001-10-i;8ll February 26, 1958 5714

TESTS OF PRESTRESSED CELLULAR SLABS

(Slabs Nos, 20 through 27)

by

Arthur F. Kirstein

To

Bureau of Yards and Docks

Department of the Navy

IMPORTANT NOTICE

NATIONAL BUREAU OF S' intended for use within thi to additional evaluation mc

listing or this Report, althei the Office of the Director, ? however, by the Oovernmen

to .reproduce additional cop

Approved for public release by the

Director of the National Institute of

Standards and Technology (NIST)

on October 9, 2015.

r progrsii accounting documents

formally published It Is subjected

g, reproduction, or open-literature

ilsslon Is obtained In writing from

• Such permission Is not needed,

ly prepared If that agency wishes

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
»

"

I
TESTS OF PRESTRESSED CELLULAR SLABS

(Slabs Nos, 20 through 27)

Arthur F„ Kir stein

In the continuing study or the properties of prestressed cellular slabs., eight additional slabs were

tested under concentrated loads. All of the slabs were

simply supported on two edges excepu Slab No, 20 which

was simply supported on four edges. Deflections., strains,,

crack patterns., and maximum load-carrying capacities were

recorded. Since most of the slabs in this series were

made of reinforced NBS blocks which resisted premature

diagonal tension failure,, these slabs developed higher

load-carrying capacities. These loads were sufficient

to cause the four center units under the loading block

to be punched into the slab before or simultaneously with

the formation of the diagonal tension cracks in the webs

of the units. This observation suggests that the resistance to failure by punching shear may be further increased by using stronger jointing materials and future

tests will be planned to explore this possibility.

1, INTRODUCTION

This phase of the study of the properties of prestressed cellular concrete slabs was mainly concernea with

the investigation of the properties of slabs containing NBS

blocks that were reinforced with welded wire fabric, A

portion of this investigation was devoted to evaluating the

performance of unreinforced cellular pavement blocks In prestressed slabs of this type.

Seven slabs composed of 6-in, cellular blocks and

one slab composed of cellular pavement blocks were fabricated and tested in the Structural Engineering Section

Laboratories, These slabs were prestressed in two directions with 1000 psi in the longitudinal direction and either

500 or 1000 psi in the transverse direction. The slabs were

simply supported along either two or four edges and the

arrangement of the blocks was varied. Both neat cement paste

and an epoxy resin were used as materials in the slabs.
.
- 2 -

2, DESCRIPTION OF TEST SPECIMENS

2.1 Cellular Blocks

Three types of cellular concrete blocks were examined in this phase of the investigation. They were the

plain concrete NBS blocks* the NBS blocks reinforced with

welded wire fabric* and the hollow pavement blocks.

The NBS plain and reinforced blocks were hollow

6-in, cubes having an opening lj.,5- by Ip, 5 in, in cross

section. There were 1- by 2-in, elliptical access holes

in the webs to permit the passage of the prestressing

tendons. These blocks were cast in steel three-unit gang

molds that were constructed to very close tolerances. The

blocks made in these forms were of superior quality and the

exterior dimensions of the blocks were within 0,01 in, of

the nominal values. The principal dimensions of these

blocks are shown in figure 1,

The pavement blocks were 6- by 15 5/8- by 7 5/8-

in, concrete blocks with one oblong cell through the

6- by 15 5/8 in, face. The cell was bounded by two semicircles of 2 l/lp in, radius at the ends and straight lines

between them. The shell thickness was 3/k In, One circular hole one inch in diameter was made in each 6- by 7 5/8-

in, face concentric with the center line of the 7 5/8 in,

sides and tangent to the center line of the 6 in, sides.

These holes accommodated the passage of the prestressing

tendons. The principal dimensions of these blocks are also

shown in figure 1,

All of the blocks were made of a mix proportioned

of one part type III cement and three parts of sand by

weight with a water-cement ratio of 0,57« This mix had a

7-

day compressive strength of approximately 6000 psi and

determined by tests of 2 in, cubes. However* the actual

units were moist-cured for a considerably longer period of

time and then some of them were in dry storage before they

were assembled into slabs. Therefore* the compressive

strength of the concrete in the individual units should be

expected to be somewhat greater.

The Young 5 s modulus and Poisson's ratio of the concrete were determined In previous tests of the concrete

units and other specimens. Axial compression tests and

sonic modulus tests Indicated an average Young 5 s modulus of

4 x 10° psi with a variation of ^ 10 percent, Poisson 1 s ratio was found to be approximately 0.l5«
'

.
3

2.2. Prestressing Steel

"E la stuff" steel prestressing tendons were used in

this series of tests. Tensile tests of this material indicated a stress-strain relationship that was essentially

linear up to 95*000 psi 5 and exhibited a Young's modulus

of approximately 30 x 10° psi. The yield strength of the

bar was found to be 120^000 psi as determined by the 0.2

percent offset method and the tensile strength was found to

be 133*000 psi. Although "Elastuff" bars are made of coldworked high carbon steel., they are fairly ductile and can

be machined easily.

2.3. Description of Prestressed Slabs

The nominal dimensions of each slab containing 100

cellular blocks were 5-ft by 5-ft by 6-in. The arrangement

of the blocks in the slabs of this test series are described

as "criss cross" and "aligned." The crisscross assemblies

contained blocks that were arranged so that the axis through

the open ends of one block was perpendicular to the axis of

each adjacent blocks while the aligned assemblies were arranged so that the axes through the open ends of all blocks

were parallel. Both assembly methods arranged the holes in

the webs of each block in such a fashion as to permit the

prestressing tendons to be staggered with respect to the

midplane of the slab in one direction,, and to be placed at

the midplane in the other direction. Thus., the resultant

prestressing force produced an axial compression in two

directions through the slab.

Slab No. 25 was made of hollow pavement blocks which

were arranged as shown in figure 2 to produce a slab with

the nominal dimensions of 64- by 64- by 6 in. Auxiliary tests

of prestressed beam assemblies of these blocks indicated that

they required more rigid end anchorage than was used with

6-in. units to obtain 1000 psi prestress in the concrete without causing distress in the individual units. To produce a more rigid end anchorage for this slab the 12 blocks bordering

the slab shown in figure 2 were solid concrete. All of the

bars in the transverse direction were placed one-half bar

diameter above the midplane., and all of the bars in the longitudinal direction were placed one-half bar diameter below the

midplane
IIIIIIIIIII /
- 4 -

The principal variables in this test series were the

method of support, type of block, amount of prestress, arrangement of blocks, and jointing material „ A complete

summary of these variable factors are shown in table 1 along

with the maximum load-carrying capacity and the deflection

sensitivity of each slab for comparison with similar slabs

of this testing program reported in NBS Reports 4396, k-951*

and 5212 ,

2,4, Prestressing Procedure

The tensioning force was applied to the prestressing

bars by means of a hydraulic jacking rig that was equipped

with a dynamometer to determine the amount of prestressing

that was applied to the tendons „ The calibration curve for

the dynamometer is shown in figure 3*

Approximately one-half of the prestress was applied

to the slab in small increments by tightening the anchorage

nuts with a wrench. The remaining prestressing force was

applied by means of the hydraulic jacking rig. This final

stage of the prestressing operation was accomplished by using

a suitable sequence of stressing the tendons so that no unduly

large differences in strain would be induced in the blocks,

3* TESTING PROCEDURE

3.1, Test Setup

A 600,000-lb capacity hydraulic testing machine was

used to test the slabs. The specimens were simply supported

on 54-in, spans by 1-in, square aluminum bars that were

attached to the steel frames resting on the testing machine

platen. To ensure intimate contact between individual members,

all bearing surfaces were set firmly with high-strength plaster, All of the slabs were simply supported along two edges

as described above except Slab No, 20 which was simply supported along four edges. The four-edged support required

additional steel frames and aluminum support bars, otherwise

the setup was identical to that of the two-edged support,

3.2, Instrumentation

The deflection measurements of all the slabs except

Slab No, 20 were made with 0„001-in„ micrometer dial gages

that were attached to steel angles. The steel angles rested

on the slab directly over the supports, thus placing the

datum plane at the supports.
,*

'
- 5

-

Figure 4 shows the symmetrical arrangement of these gages.

The deflection measurements of Slab No. 20 were made in a different manner to accommodate the measurement of the

"curl-up" action of the corners that is typical of slabs

supported along four edges. In this case the dial gages

were attached to two steel frames that were supported on

three points. These points were located on the top surface

of the slab directly over the supports, and at the center of

the support where * theoretically , no deflection takes place.

Figure 5 shows the location of the dial gages and the position of the frame supports on Slab No. 20 . The strains on the top and bottom surfaces of the

slabs were measured with bonded electrical resistance wire

gages of the A=3 type. The location of these gages are

shown in figures 4 and 5°

Slab No. 25, the slab containing pavement blocks,

was instrumented in a fashion similar to the other slabs

that were supported along two edges. The instrumentation

diagram for Slab No. 25 is shown in figure 6.

Since it is of some interest to determine whether or

not the loading block is punched into the slab before diagonal cracks form in the webs, four dial gages were arranged

around the loading block on Slab No. 27 as shown in figure

7 to determine the changes in depth of slab and penetration

of the loading block into the slab. Two of these gages have

extensions that pass through a hole in the top flange of the

blo/ck and rest in a hole in a steel plate that is cemented

to the interior surface of the lower flange of the block.

These gages are expected to indicate when the diagonal cracks

form in the webs. The other two gages are attached to the

loading block and rest on the top surface of the slab.

These gages are expected to indicate when the loading block

is punched into the slab. An instrumentation diagram for

this slab is shown in figure 8.

3»3 Test Procedure

All of the slabs except Slab No. 25 were loaded at

the center of the top surface through a 6 - by 12- by 12- in.

concrete loading block. Since the units in Slab No. 25 were

16 in. long, a concrete loading block 6- by 16- by l6-in.

was used to apply the load to this slab. The load was

applied in increments of 2000 and 5000 lb, and gage readings

were made for each increment until the maximum load was

reached.
. , . aI
- 6 -

4,1, 4, TEST DATA

Deflection and Load-carrying Capacity of Slabs

Figure 9 shows the observed relationships between the

applied load and center deflection of Slabs Nos, 20 through

27. The reciprocal of the slope of the linear or elastic

portions of these curves can be considered to be a measure

of the deflection sensitivity of the slabs, and is expressed

in terms of micro inches of deflection per pound of applied

load { //- in/lb) , Table 1 shows a comparison of the deflection sensitivities and the maximum load-carrying capacities

of the slabs tested during this phase of the investigation

and previously tested comparable slabs.

The "curl-up" of the corners of slabs simply supported on four edges was observed for Slab No, 20 and is

shown in figure 10, Slab No, 20 was the only slab reported

herein that was supported on four edges,

4,2,

Concrete Strains

The relationships between the applied load and the

strains in the concrete for Slabs Nos, 21 through 27 are

shown in figures 11 through 17 . The legend on figure 11

indicates the positions of the strain gages on the concrete

and identifies the curves in figures 11 through 17 as top

longitudinal, top transverse, bottom longitudinal, and

bottom transverse. Figure 18 shows the load-strain relationship for Slab No, 20 which was simply supported on four edges.

Therefore, the direction of strain in the concrete cannot be

considered longitudinal or transverse. Since the strain gages

were applied to Slab No, 20 in the same positions as indicated

by the "legend in figure 11, the averages of the gage readings

on the top and bottom surface of the slab are presented in

figure 18,

4,3,

Crack Patterns

The crack pattern observed in Slab No, 24, which was

constructed of unreinforced NBS blocks, was typical of the

diagonal tension failures reported in NBS Report No, 5212,

The top view of the crack pattern in Slab No, 24 is shown in

figure 19, This widespread cracking of the flanges of the

blocks was accompanied by extensive crack formations in the

webs of the blocks. In contrast to this widespread cracking

of reinforced blocks a typical top view of the crack pattern

in the NBS blocks reinforced with welded wire fabric of Slab

No, 27 is shown in figure 20, This localized punching failure

around the loading block was accompanied by only minor cracks

in the webs of a few blocks immediately surrounding the loaded

area of the slab.
,* •
As mentioned previously in the text and indicated in

figures 7 and 8, measurements were made on Slab No. 27 to

determine the punching action of the loading block and the

vertical component of the extension of the webs in the blocks

around the loaded area. The results of these observations

are shown in figure 21. Attention is directed to the fact

that the dial gages measuring the extension of the block webs

did not indicate a sudden extension in the web associated with

the formation of large cracks until the ultimate load was

reached and the loading block punched into the top surface of

the slab. It is realized that the measurements made with the

dial gages mounted on the loading block contain minor errors

due to the local deformation around the loaded area. However,

no attempt was made to correct these errors as they were considered to be quite small.

Comparison of the two curves in figure 21 indicates

that an increase in the rate of penetration of the loading

block into the slab Is associated with the first measurable

change in the depth of the web of the cells adjoining the

loaded area. Although these displacements appeared to develop simultaneously, it is worth noting that the large values

of penetration by the loading block at loads approaching the

maximum cannot be accounted for by the much smaller value of

extension of the block web. It is probable, therefore, that

punching shear was the primary cause of failure in slabs of

the type exemplified by Slab No. 27.

5. DISCUSSION

For the purpose of comparison table 1 of this report

includes the pertinent information obtained from the previously tested Slabs (Nos. 3 , 4, 8, 11, 14, 13 , 16, 18, and

19) along with the eight additional slabs which form the

subject of this report.

Upon examination of table 1 it can be seen that the

data points to the load-carrying superiority of the slabs

made with reinforced blocks. Direct comparisons between

Slabs Nos. 11 and 26 and Slabs Nos. 18 and 27 show that there

Is a large difference in the load-carrying capacities of the

slabs containing reinforced and unreinforced NBS blocks.

Additional comparisons can be made which appear to indicate

the superiority of the reinforced blocks. These comparisons

are those of Slabs No. 16 to 20, No. 19 to 21, No. 15 to 22,

and No. 14 to 23. However, judgment of these data must be

tempered with the fact that these slabs contained two variables.

These variables were the use of reinforced and unreinforced

blocks and the use of different jointing materials in the

various slabs.
.

’

.
8

In the attempt to ascertain the difference in the

load-carrying capacities of slabs having polyester resin

and the stronger epoxy resin joints. Slab No. 24 was made

to be identical to Slab No. 19 except that Slab No. 24

had the stronger epoxy resin joints. The load-carrying

capacity of both slabs was 28,000 lb., and the failure was

caused by the formation of diagonal tension cracks in the

blocks. Since the webs of the unreinforced NBS blocks

failed, no advantage was gained by using the stronger

jointing material. However, comparisons of the test results for Slabs Nos. 21 and 26, and Slabs Nos. 22 and 27

containing reinforced blocks lead to a different conclusion. These data indicate that an increase in load-carrying capacity can be realized through the use of stronger

jointing materials. This conclusion can be verified by

comparing the results of Slabs Nos. 3 ? 4, 8, and 20 if the

differences between the various reinforced blocks are not

considered to be vital factors.

The above discussion considered only the strength

factor of the jointing material. However, there are other

factors to consider . Water tightness, which is probably the

most important other single factor, was not considered.

The grout, neat cement, polyester resin, and epoxy resin

joints are all brittle and cracks may form in the joints

under load. Designs may be made that limit the service

load so that cracks do not form. However, it may be an advantage to use a material that has a greater extensibility,

such as, an epoxy- thiokol adhesive.

As indicated in the test data, the mode of failure

for the slabs containing reinforced NBS blocks appears to

be different from that of slabs containing unreinforced

NBS blocks. Previous tests of slabs containing unreinforced blocks indicated the diagonal tension failure of the

block webs without noticeable displacement to the four blocks

directly below the loading block, while tests of the slabs

with reinforced NBS blocks In this series show a definite

displacement of these blocks as shown in figure 21.

Slab No. 25 j containing the pavement type blocks,

carried a maximum load of 20,750 pounds. These units had

fairly weak webs that required special end anchorages to

withstand the prestressing force. This weakness was again

noticed in the diagonal tension failure of the webs under

load which caused most of the bottom surface of the slab to

fall to the testing machine platen after the maximum load

was reached.

- 9

-

6. CONCLUSIONS

The foregoing discussion can be summarized in the

following conclusions:

1. The slabs containing NBS blocks reinforced with

welded wire fabric carried considerably more

load than comparable slabs containing unreinforced NBS blocks.

2. When using unreinforced NBS blocks to form a

slab* no strength advantage is derived from the

use of the stronger and more expensive epoxy

resin over the polyester resin or neat cement

paste as a jointing material.

3. The load-carrying capacity of slabs containing

reinforced NBS blocks can be increased by using

stronger joint fillers.

4. Slabs containing reinforced NBS blocks fail in

a pure punching action as the four units directly

under the loading block are punched into the slab.

Since the pavement blocks are prone to fail by

diagonal tension at low loads and since they

require special end anchorages to withstand the

prestressing force, they were found to be unsuitable for use in prestressed slabs of this

type.

USCOMM- NBS-DC

Table

1.

Comparison

of

Test

Results

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REGULAR NBS BLOCK

PAVEMENT BLOCK

FIGURE I CELLULAR BLOCKS

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CL

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SOLID CONCRETE

ANCHORAGE BLOCKS

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Cl

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FIGURE 2. ARRANGEMENT OF PAVEMENT BLOCKS IN SLAB NO. 25

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legend:

GAGES I THROUGH 12 INDICATE DIAL GAGES

CI-C4 INDICATE SR-4 GAGES ON BOTTOM SURFACE OF SLAB

C5 - C8 " " " " TOP " " "

FIGURE 4. LOCATION OF DIAL GAGES AND STRAIN GAGES ON

SLABS SIMPLY SUPPORTED ON TWO EDGES.

4

'- 6

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legend:

GAGES I THROUGH 18 INDICATE DIAL GAGES

CI-C4 INDICATE SR-4 GAGES ON BOTTOM SURFACE OF SLAB

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FIGURE 5. LOCATION OF DIAL GAGES AND STRAIN GAGES

ON SLAB NO. 20 (SIMPLY SUPPORTED ON FOUR EDGES).

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GAGES ! THROUGH 12 INDICATE DIAL GAGES

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C5 - C8 " 11 «• •• TOP " " 11

FIGURE 6. LOCATION OF DIAL GAGES AND STRAIN GAGES ON

PAVEMENT BLOCK, SLAB NO. 25.

FIGURE

4

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C5 - C8 11 n •« «• TOP 11 »» " A 8 B ARE GAGES FOR MEASURING CHANGES IN DEPTH OF SLAB.

C 8 D ARE GAGES FOR MEASURING PENETRATION OF LOADING

BLOCK INTO SLAB.

FIGURE 8. LOCATION OF DIAL GAGES AND STRAIN GAGES

ON SLAB NO. 27

')

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VERTICAL DISPLACEMENT OF CORNERS, IN.

FIGURE 10. VERTICAL DISPLACEMENT OF THE CORNERS

DUE TO THE "CURL UP" ACTION, SLAB NO. 20.

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FIGURE

II.

OBSERVED

RELATIONSHIP

BETWEEN

APPLIED

LOAD

AND

CONCRETE

STRAIN

IN

SLAB

NO.

21.

<

tr

h-

(/>

UJ

hLxJ oro

o

o

Sd I >i ‘avon a3iiddv

FIGURE

12.

OBSERVED

RELATIONSHIP

BETWEEN

APPLIED

LOAD

AND

CONCRETE

STRAIN

IN

SLAB

NO.

22

.

<X>IO I!

FIGURE

13.

OBSERVED

RELATIONSHIP

BETWEEN

APPLIED

LOAD

AND

CONCRETE

STRAIN

IN

SLAB

NO.

23.

(0

<

<r

h-

(f)

LlJ tUJcno

2

O

o

Sdl >1 ‘OVOl 03 IlddV

FIGURE

14.

OBSERVED

RELATIONSHIP

BETWEEN

APPLIED

LOAD

AND

CONCRETE

STRAIN

IN

SLAB

NO.

24.

<0OXOO

’too

ro

UJ oo

<N

COz

UJh- ooooo

UJ o > ° s

UJ

o:

CL2Oo oo

roOO

’too

lO <

o:

h-00

UJ

h-UJ

o:o2Oo

FIGURE

15.

OBSERVED

RELATIONSHIP

BETWEEN

APPLIED

LOAD

AND

CONCRETE

STRAIN

IN

SLAB

NO.

25.

<£>

LU O W

CM 2

LU

<

CCI—

if)

LUILd

<ro

2

o

o

IU>

if)

if) LU

CE

0-s

o

o

Sdl» ‘OVOl 03 IlddV

FIGURE

16.

OBSERVED

RELATIONSHIP

BETWEEN

APPLIED

LOAD

AND

CONCRETE

STRAIN

IN

SLAB

NO.

26.

11

"II

Io

x

«» <

cr. h-CO

UJ

UJ

<ro

2

o

o

Sdi* ‘ovoi Q3 IlddV

FIGURE

17.

OBSERVED

RELATIONSHIP

BETWEEN

APPLIED

LOAD

AND

CONCRETE

STRAIN

IN

SLAB

NO.

27.

co

iO

x

<

QC

I

CD

UJ

LlI tro

o

o

Sdix ‘ovoi a3iiddv

FIGURE

18.

OBSERVED

RELATIONSHIP

BETWEEN

APPLIED

LOAD

AND

CONCRETE

STRAIN

IN

SLAB

NO.

20.

SUPPORT SUPPORT^ N

FIGURE 19. TOP VIEW OF CRACK PATTERNS IN SLAB NO. 24.

^ N

FIGURE 20. TOP VIEW OF CRACK PATTERNS IN SLAB NO. 27.

VERTICAL

EXTENSION

OF

BLOCK

WEBS

COO

in

o

o

rOO

CMo

Lu

S

LU

O

<

_J

CL

CO

sdi>i

l avon Q3HddV

FIGURE

21.

PENETRATION

OF

LOADING

BLOCK

INTO

SLAB

AND

VERTICAL

EXTENSION

OF

BLOCK

WEBS,

SLAB

NO.

27.

U. S. DEPARTMENT OF COMMERCE

Sinclair W eeks, Secretary

NATIONAL BUREAU OF STANDARDS

A. V. Asti n. Director THE NATIONAL BUREAU OF STANDARDS

The scope of activities of the National Bureau of Standards at its headquarters in Washington,

D. C., and its major laboratories in Boulder, Colo., is suggested in the following listing of the

divisions and sections engaged in technical work. In general, each section carries out specialized

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

the activities, and of the resultant publications, appears on the inside front cover. WASHINGTON, D. C.

Electricity and Electronics. Resistance and Reactance. Electron Devices. Electrical Instru- ments. Magnetic Measurements. Dielectrics. Engineering Electronics. Electronic Instrumentation, Electrochemistry.

Optics find Metrology. Photometry and Colorimetry. Optical Instruments. Photographic

Technology. Length. Engineering Metrology.

II eat. Temperature Physics. Thermodynamics. Cryogenic Physics. Rheology. Engine

Fuels. Free Radicals Research.

Atomic and Radiation Physics. Spectroscopy. Radiometry. Mass Spectrometry. Solid State Physics. Electron Physics. Atomic Physics. Neutron Physics. Nuclear Physics. Radioactivity. X-rays. Betatron. Nucleonic Instrumentation. Radiological Equipment.

Chemistry. Organic Coatings, Surface Chemistry. Organic Chemistry. Analytical Chemistry. Inorganic Chemistry. Electrodeposition. Molecular Structure and Properties of Gases. Physical Chemistry. Thermochemistry. Spectrochemistry. Pure Substances.

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

Mass and Stale. Capacity, Density, and Fluid Meters. Combustion Controls.

Organic and Fibrous Materials. Rubber. Textiles. Paper. Leather. Testing and Specifications. Polymer Structure. Plastics. Dental Research.

Metallurgy, Thermal Metallurgy. Chemical Metallurgy. Mechanical Metallurgy. Corrosion.

Metal Physics.

Mineral Products. Engineering Ceramics. Glass. Refractories. Enameled Metals. Concreting Materials. Constitution and Microstructure.

Building Technology. Structural Engineering. Fire Protection. Air Conditioning, Heating,

and Refrigeration. Floor, Roof, and Wall Coverings. Codes and Safety Standards. Heat

Transfer.

Applied Mathematics. Numerical Analysis. Computation. Statistical Engineering. Mathematical Physics.

Data Processing Systems. SEAC Engineering Group. Components and Techniques. Digital

Circuitry. Digital Systems. Analog Systems. Application Engineering.

• Office of Basic Instrumentation. • Office of Weights and Measures.

BOULDER, COLORADO

Cryogenic Engineering. Cryogenic Equipment. Cryogenic Processes. Properties of Materials.

Gas Liquefaction.

Radio Propagation Physics. Upper Atmosphere Research. Ionospheric Research. Regular

Propagation Services. Sun-Earth Relationships. VHF Research.

Radio Propagation Engineering. Data Reduction Instrumentation. Modulation Systems.

Navigation Systems. Radio Noise. Tropospheric Measurements. Tropospheric Analysis.

Radio Systems Application Engineering. Radio Meteorology.

Radio Standards. High Frequency Electrical Standards. Radio Broadcast Service. High

Frequency Impedance Standards. Calibration Center. Microwave Physics. Microwave Circuit

Standards.