NATIONAL BUREAU OF STANDARDS REPORT

5783

SUMMARY REPORT

ON

FIRE RESISTANCE OF REINFORCED CONCRETE

by

Vo Ryan

<NB^

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
THE NATIONAL RLKEAL OF STANDARDS

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NATIONAL BUREAU OF STANDARDS REPORT

NB8 PROJECT MBS REPORT

1002“12”^872 February 11, 1958 5783

SUMMARY REPORT

ON

FIRE RESISTANCE OF REINFORCED CONCRETE

by

Js V* Ryan

Report to

Office of the Chief of Engineers

Bureau of Yards and Docks

Headquarters, U* S» Air Force

9MP0RTANT NOTICIE

NATiONAfi. BUREAU OF 8TAI

jntandAd for tue within the Qi to addltSonoO evaluation and

lilting ofthle Reiporti either In the Office of the Olrector, Natli howeveri the Government i| to foproduco additional eoplee

Approved for public release by the

Director of the National Institute of

Standards and Technology (NIST) on October 9, 2015.

ogreii accounting docuroento

naliy publlihed It li lubjected

eproductloni or open-literature on li obtained In writing from

Inch perrolulon It not neededi

repared If that agency wlihei

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
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SUMMARY REPORT

ON

FIRE RESISTANCE OF REINFORCED CONCRETE

ABSTRACT

An investigation was undertaken to determine the

effects of certain variables on the fire resistance of

reinforced concrete. A theoretical approach was

followed with subsequent actual fire tests. The results

obtained indicate that a good start has been made on the

investigation of the effect of cover thickness and that

the theoretical method is worthy of further studyo

1. INTRODUCTION

During tests to evaluate the fire endurance of

roof deck systems (1) , the reinforced concrete beams

used to support the decks failed to perform as well

as anticipated from the usual design practices. Beams

that had been expected to provide support of as much

as four hours to the roof decks, if needed, became

unsatisfactory in as little as N9 minutes. This

raised serious doubts as to the adequacy of the

existing information upon which reinforced concrete

beams, and other structural elements, were designed

to have the necessary fire resistance.

Experience from actual fires and a limited number

of fire tests had shown that concrete structures

often spalled under fire exposure, leading to partial

or complete loss of the protective thickness. However,

this spalling had not followed any clear pattern and

several theories have been advanced to explain the causes.

Unfortunately some of the various theories disagreed with

others.

In view of the obvious need for data, an investigation of the factors affecting the fire resistance of

reinforced concrete was undertaken. Among the factors

of interest were thickness of protective cover and period
»2 "

of aging 0 The stndy has been initiated successfully and

valuable data obtained* However 5 the lack of available

funds has made it necessary to cease activity at the

present time* This report is a summary of the

progress to date*

2. PLAN OF THE INVESTIGATION

The problem was attacked along two lines, theoretic

cal and experimental* The theoretical phase was undertaken first and the experimental phase designed not

only to study factors affecting the fire resistance of

reinforced concrete but also to explore the usefulness

of the theoretical method*

2ol Theoretical Phase

The theoretical study was made by digital computer

calculations of two dimensional heat flowo The

differential equations expressing the heat flow by

conduction in solids and those expressing the applicable

boundary conditions were modified to difference equations

in order that the digital computer could be employed*

The effects of moisture, phase changes in the concreting

materials, changes in the thermal properties, and the

mechanical behavior of concrete when exposed to high

temperatures are factors affecting the fire endurance*

These factors are not all well understood so that

allowance for them could be made only approximately in

setting up the equations* The complexity of the

probI.em was such that the capacity of the available

computer was a limiting factor* These app,roximations

and limitations required that the results of such

calculations be used with caution* It is believed,

however, that this method can lead to the development

of scaling relationships by which estimates may be made

of the probable behavior of reinforced concrete structures

when experimental results for similar stru.ctures are

available* The work and results of this phase were

summarized in a report (2) submitted to the sponsors

in September 195^<> Further work under this phase

since that date has involved preparations to obtain

more accurate solutions of the equations by uti.llzation

of a recently acquired computer of greater capacity*

However, the available funds were expended before any

results could be obtained* Therefore, the remainder

of this report will be concerned with' the experimental

phase and comparisons between the results*
“ 3

-

2®2 Experimental Phase

The experimental phase of the program was designed

to provide a basis for evaluation and verification of

the results of the theoretical method*, The heat flow

equations had been applied to concrete T^beams with top

slabs that extended far enough from the beams to

permit consideration of them as simple slabs, for heat

flow behavior® Therefore, the experimental work was

made up of fir'e exposure tests of a series of T-beams

and a series of slabs*

3* SPECIMENS AND MATERIALS

The beams were 17 ft in overall length and had

crosS“Seetlons in the shape of a To In order to simplify

both the fabrication and testing of the beams and still

permit a considerable range of cover thickness for the

reinforcing bars, the only variables were the overall

beam depth and the horizontal spacing of the main

reinforcement. The top slabs of the T*s were 5 ino

thick and ^6 in, wide approximately. The stems of the

T*s were approximately 11 3A^ ino wide and of depths that

differed from specimen to specimen. The beam reinforcement consisted of six longitudinal No, 8 deformed bars

with nine No, 3 deformed bar stirrups near each end®

The top slabs were reinforced with two No, 5 and three

No, 3 longitudinal deformed bars and with tran.sverse No,

4 deformed bars. The six No, 3 bars were placed in three

pairs, the vertical center-to-center distance between

pairs being 2 in. The horizontal, distance between the

bars within each pair was determined by the amount of

cover to be provided. The distance from the top

surface of the finished specimen to the midheight of the

group of Noo 8 bars was the same in each specimen so

that each beam would have the same total design load,

A 2~ by 4“in, rectangular mesh wire fabric was placed

in contact with the bottom and sides of the beam rein^

forcing bars and the bottoms of the top slab bars of

all the specimens except that having the least cover.

The general arran.gement of the reinforcement is shown

in figure 1,

The assembled reinforcement for each beam specim.en

was placed in a form which was then filled with concrete.

An electric powered vibrator was used during the pouring

of the concrete. The concrete was mixed 1 part by weight

of Portland cement, 4,1 parts sand, 3,4 parts gravel;

with a water/cement ratio of 0,90, The maximum allowed
\

gravel size was 3A in. for 'beams to have cover of

greater than 1 in, and 3/8 ino (White Marsh pea gravel)

for the beams to have cover of 1 ino or less. The

sand was a bank sand with an appreciable proportion of

small gravel included*

The beam depths and horizontal spacing of the No* 8

bar's were set to provide nominal covers of 1/2, 1, 2,

and h in* Each beam was left in the form several weeks

and then stored in a building that was well ventilated

during good weather and heated during colder weather*

They were stored for periods of about 2 years before

test, during which time measurements were made to

indicate the state of drying* These measurements were

made by mean.s of humidity sensing devices in tubes

extending into the concrete. The ends of the tiibes

in the concrete were open but those outside were sealed.

The devices gave indications of the relative humidity

of the air enclosed in the tubes* Assuming that moisture

equilibrium was reached between the air and concrete,

these relative humidity readings may be related to the

moisture content of the concrete in the vicinity of the

open end of the tubes.

The slab specimens were each 2 ft square* They were

made to nominal thicknesses of 1, 2, 3? and h inches*

Two slabs were cast of each thickness* No reinforcement

was used in the slabs. Tubes to permit humidity measurements were placed in the forms for four of the eight

specimens before the concrete was poured* The concrete

for the slabs was the same mix as that for the T-beams*

However, only the 3/8 in* maximum pea gravel was used

for coarse aggregate* After each slab was removed from

the forms, it was stored in a room maintained at approximately 70° P and 50 percent relative humidity* The slabs

were stored for periods up to nine months before test*

Thermocouples had been attached to the reinforcing

bars of the beams before they were placed in the forms*

Similar thermocouples were placed in the slab forms

before the concrete was poured. The locations of the

couples are indicated in figure 2*

h. TEST PROCEDUKE

The specimens were placed in furnaces appropriate

to their sizes and exposed to fires controlled to

produce, as closely as practicable, the temperatures of
” 5

“

the standard time -temper atare curve defined in ASTM

Standard Method for Fire Test of Building Construction

and Materials, E-119, which includes 1000*" F at 5 min,

1300°F at 10 min, 1550°F at 30 min, 1700°F at 1 hr,

1850°F at 2 hr, and 2000°F at h hrs.

4-»l Beam Tests

Each team was placed along the longitudinal centerline of the large floor- test furnace « Each end rested

on a short section of steel beam suspended from a heavy

I-beam frame* The supports were provided with means

for cooling by circulating water and were enclosed,

with the ends of the beams, in brick and plaster. The

exposed length of each beam was approximately 1^ ft.

Separately supported slabs were used to close the

remainder of the furnace opening, A gap of about 3 in,

width between each side of the T-beam top slab and the

filler slabs was filled with mineral wool or glass fiber

insulation.

The applicable Standard Test Method specifies that

load-bearing building components shall be tested under

a load calculated to develop the working stresses contemplated in the design. It further specifies that the

specimen shall sustain this load throughout the fire

test. However, it does not specify what shall constitute

failure to sustain the load. Various criteria have been

considered as an aid to the determination of load failure,

including the combination of a deflection and a rate of

deflection, the values of which are related to dimensions

of the specimen.

The beams were loaded at four points, 2 and 6 ft

on each side of center, through rollers on bearing plates

laid on the top surface. Each beam was subjected to a

total load of 59600 lb, including the dead weight of the

beam. This load was designed to stress the steel to

20,000 psi. The beam with 2 in® cover was tested

without full load in order to reduce the moisture content.

It had been intended to retest it with full load later

but the beam suffered some damage during the initial

exposure. Therefore, it was retested without full loado

The fire exposure of each beam, except the nonloaded exposures of the 2 in, cover beam, was continued

until a net deflection of at least 2,5 in® was attained®

The test of the beam with 1/2 in, cover was continued

after this deflection had been reached and the load removed

in order to obtain additional temperature data.
- 6-

Temperatures were recorded from the thermocouples

in the furnace, on the reinforcing "bars, in the concrete,

and on the ijinexposed surfaces. Each beam was broken

up after test in order to determine, if possible, the

actual cover thicknesses achieved and the actual positions

of the thermocouple Junctions,

4,2 Slab Tests

The small slabs were tested in a furnace having an

opening of about 22 in, square. The slabs were laid on

the top of the furnace to close this opening. The edges

of the slabs were Insulated with fire brick and mineral

wool to minimize lateral heat losso A metal pan,

painted black, in which water was circulated, was

positioned about 6 to 9 in, above the unexposed surfaces

of the slabs. This pan acted as an absorber of the

heat energy radiated from the specimens and thus served

to provide some control of ambient conditions. Measurements of the flow rates and temperature rises of the

water were made to give an indication of the rate of heat

transfer. Of the two slabs of each thickness, one was

tested with a thermocouple, under a 6 in, square by 0,4

in, thick felted asbestos pad, at the center of the

unexposed surface, and the other was tested without either

thermocouple or pad. Unexposed surface temperature

indications were also obtained by commercial, marking

pencils, the marks of which were stated by the manufacturer to melt at selected temperatures. Temperatures

were recorded from thermocouples in the furnace, in the

concrete, and as mentioned, on the unexposed surfaces

of half the slabs. The fire exposures were continued

until temperatures in excess of 1000°F had been indicated

by all the thermocouples in the concrete. No load was

applied to any of the slabs.

Following each test, the slab was examined and

broken up to determine the actual depths from the exposed

surface to the thermocouple Junctions and the actizal

thickness of the slab.

5, RESULTS

ine humidity data from the beams were obtained by

cards with spots of dyes each of which changed color over

certain humidity ranges. Color change of all the spots

Indicated relative humidity of over oO percent. The

cards were placed in the pipes extending into the concrete,

and the open ends of the pipes than capped. Throughout

the aging periods of the beams, not only did all the spots
“ 7

"

change color but the dyes ran and the cards felt damp

when removed from the pipes® This was taken to indicate

that the relative humidity of the air in the pipes was

in the range of 95 to 100 percent® Consequently it is

evident that the concretes at the centers of the beams

were still wet after almost two years of aging®

The humidity data from the 2 ft square slabs were

obtained by electrical resistance type humidity sensing

elements, each sealed into a pipe fitting attached to

close one end of a copper tube extending into the center

portion of one of the slabs® The length to inside diameter

ratio of the tubes was very large as was the ratio of the

volume of air surrounding the sensing element to the area

of the end of the tube open to the concrete® These

two factors made the system very slow to come to equili“

brium and, therefore. Insensitive to short=time fluctua=-

tionso The aging of the slabs in a constant temperature

and humidity room eliminated or greatly reduced such

fluctuations so that the slow approach to equilibrium

was the chief drawback® The data indicated increasing

relative humidity for about the first month during which

readings were taken® Since the moisture content of the

concrete would have been decreasing from its initial high

value or have reached an equilibrium value during this

period, it must be assumed that the increasing humidity

readings indicated that the air in the copper tube and

pipe fitting systems was still coming to moisture equili“

brium® For the remaining several months, the relative

humidity values from three of the four specimens leveled

off® The readings at about six months were in the range

of 5l to 5^ percent® Since the specimens had been in a

room maintained at about 50 percent relative humidity,

the data shows they had come to uniform moisture content

throughout, in moisture equilibrium with the surrounding

atmosphere ® Although the primary purpose of the fire exposure

tests was the accumulation of data on the time “temperature

history at various depths and locations within the specimens

when the standard time-temperature exposure occurred on

the appropriate surface, the T-beam.s were tested in

compliance with the standard method for determining fire

endurance® Therefore, the results of these tests are

reported with both temperature history and fire endurance

in mind®
^ 8-

5«1 Fire Endurance of T-beams

The fire endurance of reinforced concrete beams is

determined by failure to support the design load. The

beams with 1/2, 1, and h in. cover were tested under

load and reached net deflections that raised doubts as

to their ability to sustain the load further at 1 hr

6 min, 1 hr 58 min, and 5 hr 20 min, respectively. The

behaviors of the individual beams were much the same

in their respective tests. In ail but the test of the

beam with 1 in. cover, concrete sloughed off along each

arris at the bottom of the beam, in lengths from a few

feet to nearly full length and up to depths sufficient to

expose part of the bottom No. 8 reinforcing bar. This

loss of concrete started within the first 10 to 15 min

and continued Intermittently throughout the test. There

were not, ordinarily, any distinct sounds associated with

the sloughing, nor any other evidence of spalling of some

violence. In addition to the sloughing of concrete, cracks

formed and enlarged in the beam stem and top slab. Those

in the beam stem were mostly tension cracks, extending

across the soffit and up each side. Those in the top

slabs extended up the sides but varied from short, and

full width, transverse cracks to nearly full length

longitudinal cracks. Examples of the cracking and

sloughing of concrete are shown in figures 3, 5? and 6.

The deflections of the loaded beams Increased throughout their tests except for the beam with 4 in. cover.

This beam was loaded to about .8 of the design applied

load for the first 1 hr 15 min, during which period the

deflections increased at first and then decreased. The

application of full design load required the substitution

of a different regulator in the loading system. This was

done between 1 hr 15 min and 1 hr 30 m.in, after which time

the full design load was applied. After the full load

application, the deflection curve was of the same general

form as those of the other fully loaded beamso The beams

with 1/2 and 1 in. cover were under full load from the

start of the fire exposure. The deflection curves are

shown in figure 7«

5*2 Time-temperature History

The temperature data obtained from the several thermocouples on the reinforcing bars and in the concrete of the

T-beams and the 2 ft square slabs were examined to determine

the times at which temperature of 1000° F was attained at

each location. Most steels used in reinforcing bars have

yield strength values at 1000°F equal to about 50 percent

of their room-temperature values. Because of this and
“ 9

“

the fact that safety factors of two are usually involved

in design of such specimens, this temperature is often

taken to he critical in evaluating the protection

afforded steel by various materials, and is sometimes

considered an indication of the immi.nence of load failure

However, for the loaded beams, the times at which load

failure occurred were significantly greater than the

times at which this temperature was first reached at one

of the thermocouples on the Noo 8 steel barso This should

be expected since the beams included bars of this size

that had cover from the bottom greater than the minim,umo

In none of the beam tests was this temperature observed

on all the Noo 8 barso It is believed, however, that

the attainment of this temperature may be taken as an

indication of the approximate time that load failure

should be expected for beams having only two main

reinforcing bars, so located that each bar has equal side

and bottom cover o As in all but one of the tests dis=

cussed herein, fire exposure of reinforced concrete

beams often results in sloughing or spalling of concrete,

especially from the arrises, to reduce the thickness of

cover for the steel reinforcements The loss of cover

reduces the time required for temperature rise in the

steel and, therefore, the time to load failure » On the

other han.d, adequate means to retain the concrete in

place may be expected to Increase the fire resistance to

be obtained from a given bearo.o Since the theoretical

method assumed no sloughing, the predicted values should

more nearly agree with the performances of beams designed

to prevent or reduce sloughing

o

The temperature data, as translated to time=to“1000°F,

was compared with the time for equivalent beams or slabs

as predicted by the theoretical precedures previously

carried outo The results are presented in the form of

correlation charts, or plots of the actual times observed

in tests against the times predicted by theory o Figures

8 through 10 are these chart So The solid line in each

corresponds to a l-tO“l correlation, or full agreement

between experiment and theoryo

6« DISCUSSION

The sloughing of concrete from the beams gives an

indication of the effectiveness of the wire fabric placed

outside the bar reinforcement » The fact that the 1 ino

cover, with fabric, remained intact whereas the 1/2 in<, cover

sloughed badly indicates that the latter should have

remained intact had fabric been included (See figures 3

and 5)o Since the 2 in» and h in^ covers sloughed
- 10-

despite the presence of the fabric, it appears that the

fabric is not fully effective when placed far from

the concrete surface. However, for beams in which the

main reinforcing bars are to have covers of 2 in, or more,

placement of the wire fabric at about 1 in, from the

concrete surface may be expected to retain the cover

during fires, and improve the beam's fire resistances

over those of beams similar except for the use of such

fabric

The agreement between theoretical and actual heat

transfer data is fairly goodo In fact, it may appear

to be better than it actually is. The theoretical

value is determined on the basis of the thickness of cover

for the reinforcing steel or for the thermocouple junction

in the concrete. But, since the omission of the effect

of the steel bars was a necessary simplification for the

theoretical computations, this value is for a particular

locus, a line perpendicular to the cross section in a

beam or a plane parallel to the surfaces in a slab.

However, the thermocouple junctions were beads of about

0,05 in, diameter and the main steel bars were of 1 in,

diameter. Consequently, the actual temperatures

observed were not those at particular points but represented the effect of heat flow across a concrete-to-=metal

surface into a volume. To permit comparisons with

theoretical values, it was assumed that bar temperatures

could be directly compared with computed temperatures of

the concrete at a position corresponding to the center of

the bar.

Another limitation on the quality of the correlation

obtained is that due to uncertainty as to the precise

locations of the thermocouple junctions and cover for

the steel bars. Reasonable care was taken to support

the bars and thermocouple junctions in the desired

positions during the casting of the specimens. Following

fire exposure, each specimen was broken up, the thermocouple leads traced, and the locations of the junctions

measured where possible. However, the accuracy of these

measurements was affected by the conditions of the specimens.

The beams were tested until a minimum deflection was

reached in most instances and the exposures continued

well past the times at which 1000°F was reached. Many

of the thermocouple leads were very brittle, as a result

of the long exposure to high temperature, and broke

during the breakup of the specimens. This, coupled with

the sloughing of concrete from the beam arrises during

tests, made the measurement of concrete cover for the

bars at the thermocouple locations impossible in many
casesg It was necessary to assume that the intended

nominal cover had been achieved, but variation of 1/h

to 1/2 ino must be considered a real possibilityo

The thermocouples in the slab portions of the beams

were placed in holes drilled from the top surface at the

time of preparation for testo The thermocouple junctions

were placed in the holes which were filled with a loose

granular insulator. The locations of the junctions were

determined by measuring the lengths of leads in the

holeso The measurements were probably accurate to about

l/l6 to 1/8 in ,

in the 5 in, thick slabs, or about 1 to

2o5 percent of the total thicknesso

The tests of the 2 ft square slabs were stopped

shortly after 1000° F was reached at the thermocouple

junction most remote from the exposed surface in each

case. No concrete was sloughed from the surfaces and

the thermocouple lead wires were less brittle than were

those in the beamso Therefore the original surfaces

were still intact and it was possible to measure the

thermocouple junction locations to the nearest 1/32 in,

in all cases and the nearest l/6k in, (about 1/2 to lA

the junction bead diameter) in most cases. Consequently

the correlation indicated in the figures is most meaningful for the 2 ft square slabs and least meaningful for

the beam bars.

The data from the 2 ft square slabs more nearly

approximates a straight line than either that for the

beam bars or that for the slab portions of the beams.

However, this line does not coincide with the l“to“l

correlation line, nor is it parallel. It represents

correlation between theoretical and actual values of

about ^-to-3 for slabs without unexposed surface

thermocouple pads.

The timeS“tO“1000°F for the thermocouples in slabs

with unexposed surface pads were significantly less than

those for similarly placed thermocouples in slabs without

pads. Thus, on concrete slabs of thicknesses at least up

to h in,, the presence of insulating overlays of limited

lateral dimensions influences the temperatures within

the slabs, and may be expected to influence the fire

resistances of the slabs.
7. SIMMARY AND CONCLUSIONS

The fire endurance tests of the beams provided data

on the fire endurances of particular constructions over

a range of concrete cover thicknesses.. These data should

be of value in the design of reinforced concrete beams

for desired fire resistances.

The tests point up the importance of the retention

of all the concrete as cover to the structural reinforcement. The inclusion of wire fabric at about 1 in. from

the concrete surface, or immediately outside the main

bars in cases of cover less than 1 in., was shown to be

both satisfactory and practicable as a means to achieve

this end. The fabric employed had a 2- by 4-in. mesh,

but a 4- by 4-in. mesh probably would have been adequate.

The tests of the beams and small slabs provided

data upon which to make correlations with the predictions

derivable from the theoretical work done previously. The

correlations were fairly good, which indicates that the

procedures followed and assumptions made in the theoretical analysis were reasonable. The fact that the

correlations were not l-to~l may be due in part to the

limitations of the available computer and the resulting

possible errors in the theoretical values.

The overall investigation clearly indicates the

effect of cover thickness on the fire endurance of

reinforced concrete beams. It shows that the assumptions,

as given in some fire resistance listings, that fire

resistance is independent of cover thickness beyond 1 1/2

in., and that 1 1/2 in. cover is adequate for 4 hr

resistance, are both erroneous.
“13-

references

1, "Fire Tests of Concrete Channel Slab Roof Deck

Constructions," J. V<, Ryan, NBS Report 27^7,

July 3, 1953* An unpublished report of the

National Bureau of Standards to the Department

of the Army, Office of the Chief of Engineers*

2. "Theoretical Heat Transfer Scaling Relationships

for Fire Endurance of Reinforced Concrete," ko

F« Robertson and S* M* Genensky, NBS Report 4-85^,

September 21, 1956* In unpublished report of the

National Bureau of Standards, to the Office of

Chief of Engineers, Department of the Army and

Directorate of Construction, U* S* Air Force*

USCOMM-NBS-DC

AT ENDS OF BEAMS

NOTE- DIMENSIONS "A"AND"B" VARY WITH AMOUNT

OF PROTECTIVE COVER PROVIDED TO STEEL

/MD/r- ALL BARS DEFORMED, OF INTERMEDIATE GRADE STEEL

FIG. I- CONSTRUCTION DETAILS OF BEAM SPECIMENS
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U. S. DHrARTMKNT OF COMMERCE

Sincliiir Weeks. Socretary

NATIONAI- HllHEAU OF STANDARDS

A. V. Astiii, Dirvetor THE NATIONAL BUREAU OF STANDARD.S

"I'he scope of activities of the National Bureau of Standards at its lieadquarters 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, eacli section carries out specialized

research, developnient, and engineering in the field indicated hy 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. Fhigineering Electronics. Electronic Instrumentation. Electrochemistry.

Optics {Uid Metrology, 1‘hotometry and (Colorimetry. Optical Instruments. Photographic

Technology. Length. Engineering Metrology.

II eat. Temperature Physics. rhermodynamics. (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. Ratliological Equipment.

Chemistry. Organic (Coatings. Surface (Chemistrv. Organic (Chemistry. Analytical Chemistry. Inorganic Chemistry. Eleclrodeposition. Molecular Structure and Properties of Gases. Physical Chemistry. Thermochemistry. S|)ectrochemistry. Pure Substances.

Mechanics. Sound. Mechanical Instrumenis. Fluid Meclianics. Engineering Mechanics.

Mass and Scale. (Capacity, Density, and Fluid Meters. (Combustion (Controls.

Organic and Fibrous Materials. Rubber. '1'exlile.s. Paper. Leather. Testing and Specifications. Polymer Structure. Plastics. Denial Research.

Metallurgy. Thermal Metallurgy. (Chemical Metallurgy. Mechanical Metallurgy. Corrosion.

Metal Physics.

Mineral Products. Engineering (Ceramics. (Class. Refractories. Enameleil Metals. (Concreting Materials. (Constitution and Microstrm'lurc.

Building Technology, Structural Engineering. Fire I’rolection. 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. SEA(C Engineering (Croup. (Components and Techniques. Digital

(Circuitry. Digital Systems. Analog Systems. Ap|>lication Engineering.

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

BOULDER, (COLORADO

Cryogenic Engineering, (Cryogenic E<piipment. (Cryogenic Processes. Properties t)l Malcrials.

Gas Liquefaction,

Radio Propagation Physics. Upper Atmos|)here Research. Ionospheric Rt'searc h. Regular

Propagation Services. Sun-Earth Relationships. VHF Research.

Radio Pro[)agation Engim^ering. Data R<*duclion Instrumentation. Modulation Systcni.s.

Navigation Systems. Radio Noise. 'rropospheric Measurements. 'rro|>os|)heric Analysis.

Radio .Systems Application ICngineering. Radio Mct<‘orolog>

Radio Standards. High I'reipiem'y Eha’trieal .Standards. Radio Broadcast .S*m\ ie<‘. High

Fn-quency Inqicdanee .Standards. (Calibration (Cenlei-. Microwave Ph>sies. Mierowa\e (.ireuit

Standards.
) i