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NATIONAL BUREAU OF STANDARDS REPORT

5821

FIREPROOFING STRUCTURAL STEEL

'by

Eo Mo Bender

<NB§>

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
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

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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

NBS PROJECT NBS REPORT

1002-20-4875 March 27, 1958 5821

FIREPROOFING STRUCTURAL STEEL

by

E. W. Bender

Report to

Office of the Chief of Engineers

Bureau of Yards and Docks

Headquarters, U. S. Air Force

IMPORTANT NOTICE

NATIONAL BUREAU OF STANE

intended for use within the Gov

to additional evaluation and revie listing of this Report, either in w

the Office of the Director, Nation however, by the Government age

to reproduce additional copies fc

Approved for public release by the

Director of the National Institute of

Standards and Technology (NIST)

on October 9, 2015.

rress accounting documents

lly published it is subjected

roductlon, or open-literature

i Is obtained in writing from

:h permission Is not needed,

pared if that agency wishes

<NBS>

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
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FIREPROOFING STRUCTURAL STEEL

ABSTRACT

An investigation of the effectiveness of fire-retardant

materials which can be applied directly to structural steel

members by spray techniques has been initiated® Test specimens have been prepared with protective coatings applied in

three different thicknesses by a number of manufacturers,

using normal field methods of application® Results of fire

tests on specimens protected by 1/2 in* fire-retardant coatings

are reported,,

1. INTRODUCTION

In certain types of buildings such as aircraft hangars,

it is common procedure to leave the structural steelwork unprotected, In cases where automatic sprinkler protection

cannot be furnished, the fire hazard may be high and losses

great. There are on the market today various materials which

can be applied by spray techniques directly to the steelwork,

and which are claimed to be useful for protection against fire.

The aim of this investigation was to obtain performance data

on these materials*

2. MATERIALS

A metal support structure to be fire-tested consisted of

a 2-ft square, 16 ga, hot-rolled steel plate, spot-welded to

a grid composed of 3/*+ in* cold-rolled plasterer s

1

• furring

channels. Specimens of these structures were sent to various

manufacturers to be coated with fire-retardant materials in

three different thicknesses, namely, 1/2 in,, 1-in,, and 2-in,

Each manufacturer was supplied with four specimens for each

thickness, two with the hot-rolled finish as received, and two

shop-coated. Metal grounds were welded around the periphery

of the surface to be coated, to insure obtaining the proper

thickness of the fireproofing* Only the specimens coated to a thickness of 1/2 in* are included in this report®

The fire-retardant coatings were said to have been applied

with the same equipment and techniques normally used in the

field. In surface finish the coatings ranged from a felted naplike finish to a hard troweled finish, and the materials ranged

in density from 12*2 to 64*9 lbs/ft^ or 0*52 to 2,7 lbs/fir for
- 2

a 1/2 in, thickness. Following is a list of the manufacturers

who applied the materials tested, together with a brief note

regarding the major components of each product:

Mr-O-Therm Application Company

Jet -Sul at ion

A mixture of all glass fibers and binder,

Columbia Acoustics and Fire Proofing Company

Cafeo Spray Standard Fiber

A mixture of all glass fibers and binder,

Keasbey and Mattison Company

Sprayed "Limpet" Asbestos

A mixture of all asbestos fibers and Portland

cement binder,

Larson Products

"Plaster Weld"

A liquid bonding agent for plaster. A plaster of perlite,

asbestos fiber, and gypsum was applied over the "Plaster

Weld" by means of a plastering machine.

National Gypsum Company

Thermaeoustic

A mixture of mostly glass with some asbestos fibers.

Smith and Kanzler Jetbestos Inc.

Spray Craft

A mixture of glass and asbestos fibers and binder.

United States Gypsum Company

Audicote

A mixture of perlite, bentonite clay, and asbestos fiber,

Zon-O-Lite Company

Zon-O-Lite Acoustical Plastic

A mixture of vermiculite, bentonite clay, and asbestos fiber,

3, METHOD OF TEST

The tests were performed in a firebrick furnace that

forms a cube-shaped combustion chamber, the specimen, with

the fireproofed face down, providing the cover for the cube.

The furnace is gas fired and vented by means of a baffled

flue and chimney to the outside. The temperature in the

the combustion chamber is automatically regulated so that it

follows the time-temperature curve prescribed in ASTM Spec, Ell

9
- 3 -

Standard Curve for Fire Tests, The times and temperatures

specified are 1000°F at 5 min, 1700°F at 1 hour,-* 2000°F at

b hours, and 2300° F at 8 hours.

The specimen is placed over the top of the combustion

chamber, with 1/2 in. of the face of the specimen resting

on the firebrick wall on all sides. An asbestos or mineral

wool gasket is placed around the edges of the specimen to

minimize heat flow from the specimen*

A transducer made of insulating firebrick, 2 ft long by

12 in* wide by 1 in* thick, is placed over the channel iron

backing of the specimen plate. The underside of the transducer

is blackened and thermocouples are placed on the under and

upper surfaces. Two pieces of asbestos millboard, 2b in* long

by 6 in* wide and 1/2 in* thick, with thermocouples placed on

the upper and lower surfaces, are laid on either side of the

transducer. Thus, a 3/4 in, sealed air space is formed by the

millboard and transducer and the 16 ga steel sheet of the

specimen, A thermocouple is placed on the geometric center of

the steel sheeet to indicate the temperature on the unexposed

face of the fireproofed specimen. The transducer gives an

indication of the heat flow from the combustion chamber through

the fireproofing and steel sheet,

A reinforced sheet-metal pan, 43 in by 4-3 in, with 2- in,

high sides, is suspended from the ceiling of the test room.

This pan is held 8 in, above the top of the transducer with

the center of the pan above the center of the specimen. Water

is piped to the pan and the outlets are arranged so that 1/2 in,

of water covers the bottom of the pan at all times. Records of

the water flow rate and the temperature of water entering and

leaving the pan provide another method of measuring heat flow

from the specimen.

The end point of the test was considered reached when

the temperature on the unexposed surface of the steel plate

reached 1000° F,

4 , RESULTS

The density, weight per sq ft for 1/2 in, application,

and time to reach 1000° F on the steel plate are given in

Table 1, The materials are listed in order of performance

in the fire test, that with the longest average endurance

being listed first.
5* DISCUSSION OF RESULTS

The Plaster Weld plus gypsum-perlite plaster would be

expected to give the best fire resistive performance of the

group, inasmuch as gypsum has more chemically combined water

than any other of the materials testedo This reasoning was

supported by early results in the tests of this combination,

which gave lower steel plate temperatures than any other

material until the plaster fell from the plate at 11 minutes*

At that time the stresses developed by shrinkage of the dehydrating gypsum and expansion of the heating metal were such

as to shear the plaster from the surface of the plate*

The results obtained with the other materials tested are

shown graphically in Figure 1 where density in lbs per ft^ is

plotted against time required for the steel plate to reach

1000° F* All of these materials contained either asbestos or

glass fibers, or a mixture of the two* Although no attempt

was made to determine the composition of the various binders,

it appears that, where the fire retardant components consisted

entirely of glass fibers or a mixture of glass and asbestos

fibers, the fire endurance varied with the density of the material 0 The mixture of vermiculite, bentonite clay, and asbestos showed

a similar relation between fire endurance and density,, However,

the mixture of perlite, bentonite clay, and asbestos, and also

the material consisting entirely of asbestos fibers, showed

greater fire endurance for a given density than the other

materials testedo

The fire endurance data given in this report may be used

in estimating the protection which might be obtained for a

roof, floor, or ceiling section 0 Predictions of the endurance

of columns, beams, or braces from these data is not simple,

although it is expected that some estimates of this type may be

feasible with use of the analog computer* The endurance of

1-in* thick and 2-in, thick materials will be reported when the

tests are finished*

6 0 CONCLUSIONS

Seven materials continued to bond to the steel plate for

the duration of the fire exposure* The results indicate that

these seven materials show some merit for use as fire-protective

covering when applied directly to steelwork*
TABLE 1

Fire Test Results On Specimens with One-Half Inch Fireproofing

Manufacturer Finish on Weight Time Fiber

and Plate and for Steel Plate or

Material Specimen i In® reached MineNumbe r Density Thickness 1000°F ral

Ibs/ft3 lbs/ft2

"” Min: Sec

Natl Gypsum Co® Glass &

Thermacoustic Unpainted 7 27 o 2 1*13 66 : 00 asbestos

do Unpainted 8 24-0 3 1,00 56:35

do Shop-coated 65 28 © 4 1*18 88:00

do Shon-coated 66 28 ® 1 1.17 71:00

Average 27 oO 1*12 70:24

Uo S. Gypsum Cc> © Perlite &

Audicote Unpainted 49 20 o 3 0*85 63:00 Asbestos

do Unpainted 50 20 o 7 0*86 57:33

do Shop-coated 107 17 o 5 0*73 40:00

do Shon-coated 108 17 ® 6 0.74 4l : 05

Average 19.0 0*80 50:24

Air-O-Therm

Application Co,

Jet-Sulation Unpainted 13 26 . 4

- lolO 38:30 Ail glass

do Unpainted 14- 25®1 1*05 43:25

do Shop-coated 71 21.4 0*89 45:00

do Shon-coated 7 2 15.9 0*66 . 35:00

Average 22®2 0*93 4

- 0:29

Keas'bey & Mattison

Co, All

Limpet Unpainted 25 12.9 0*54 43.35 asbe stos

do Unpainted 26 13©2 o .55 35:00

do Shop-coated 83 12*4 0*52

do Shon-coated 84- 12 ® 7 Oo 53 37:58

Average 12*8 0*54 38:51

Zon-O-Lite Co,

Zon-O-Lite

Acoustical

Plastic Unpainted 37 1. 6 ® 8 0*70 29:20 Vermicu”

do Unpainted 38 16*9 0.70 32:50 iite &

do Shop-coated 91 18.0 0.75 45:45 asbe stos

do Shon-coated 92 16*8 0 o 66 35:00

Average 17 ®I 0*70 35:44

Smith & Kanzler

Jetbestos Inc®

Spray Craft Unpainted 31 21*1 0*88 63:05 Glass &

do Unpainted 32 16*3 0*68 32:00 asbestos

do Shop-coated 85 16*7 0*70 25:00

do Shon-coated 86 15*2 0*64 22:05

Average 17.3 0*73 35.33
TABLE 1 (continued)

Manufacturer Finish on Weight Time Fiber

and Plate and for Steel Plate or

Material Specimen i In* reached MineNumber Density Thickness 1000°F rai

lb s/ft

3

lbs/ft2

Columbia

Acoustics and

Fireproofing Co.

Cafco Spray Unpainted 1 18.

3

0,76 35:00 All glass

Standard Fiber Unpainted 2 16,7 0.70 33:55

do Shop-coated 55 13.5 0,56 37:20

do Shoe-coated 56 l4.i 0.59 35:00

Average 15.65 0.65 35:16

Larson Products

Plaster Weld Unpainted 4-3 55.7 2.

3

25:00 * Perlite

do Unpainted 5-4 64,9 2,7 32:55 * asbestos

do Shop-coated 97 52,0 2,2 21:05 * gypsum

do Shou-coated 98 47.8 2.0 21:45 * Average 54.8 2^3 25:09

* Plaster fell from steel plate at approximately 11 min in

all these tests.

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1.-

FIRE

ENDURANCE

U. S. DEPARTMENT OF COMMERCE

Sinclair Weeks. Secretory

NATIONAL BUREAU OF STANDARDS

A. V. Astin, 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 pnd Metrology. Photometry and Colorimetry. Optical Instruments. Photographic

Technology. Lengtfi. Engineering Metrology.

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Metal Physics.

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and Refrigeration. Floor, Roof, and Wall Coverings, ('.odes and Safety Standards. Heat

Transfer,

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

BOULDER, COLORADO

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Standards.
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