NATIONAL BUREAU OF STANDARDS REPORT

INTERIM REPORT ON PROJECT 4847

STANDARDS FOR BUILT-UP ROOFS

by

W e C. Cullen

L. R. Kleinschmidt

H. R. Snoke

U. $. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

5422
THE NATIONAL BUREAU OF STANDARDS

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NATIONAL BUREAU OF STANDARDS REPORT

NBS PROJECT NBS REPORT

1004-40-4847 August 1957 5422

INTERIM REPORT ON PROJECT 4847

STANDARDS FOR BUILT-UP ROOFS

by

W. C. Cullen

L. R. Kleinschmidt

H. R. Snoke

Floor, Roof and Wall Coverings Section

Building Technology Division

IMPORTANT NOTICE

NATIONAL BUREAU OF ST

intended for use within the

to additional evaluation and 1 listing of this Report, either

the Office of the Director, N; however, by the Government

to reproduce additional copii

Approved for public release by the

Director of the National Institute of

Standards and Technology (NIST)

on October 9, 2015.

progress accounting documents

rmally published it is subjected

reproduction, or open-literature

sion is obtained in writing from Such permission is not needed,

prepared if that agency wishes

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

INTERIM REPORT ON PROJECT 4847

STANDARDS FDR BUILT-UP ROOFS

INDEX

Page

I. INTRODUCTION 1

II. SUMMARY AND CONCLUSIONS 1

A. Field Studies 1

B„ Laboratory Studies 2

III. PROPOSED SPECIFICATION FOR ASPHALT FOR LOW-SLOPE

ROOFS 5

IV. ACKNOWLEDGMENT 6

APPENDIX 1. FIELD STUDIES OF BUILT-UP ROOFS 7

1. Introduction 7

2. Selection of Roofs for Inspection 8

3. Areas Included in the Studies 9

4. Methods of Inspecting and Rating Roofs 9

5. Results of Field Studies 12

APPENDIX 2. LABORATORY STUDIES 13

1. Introduction 13

2. Physical and Chemical Characteristics 14

3o Component Distribution 15

4. Susceptibility to Heat 16

5. Accelerated Durability Exposures 17

6. Outdoor Exposures 21

7 o Water Absorption Tests 22

APPENDIX 3. DISCUSSION OF REQUIREMENTS IN THE PROPOSED

SPECIFICATION FOR ASPHALTS FOR LOW-SLOPE

ROOFS 24

lo Conventional Requirements 24

2. New Requirements 25
. *
INTERIM REPORT ON PROJECT 4847

STANDARDS FOR BUILT-UP ROOFS

by

W. C. Cullen

L. R. Kleinschmidt

H. R. Snoke

I. INTRODUCTION

This report gives the results of field studies of 101 lowpitched, mineral-surfaced, asphalt and coal-tar pitch, builtup roofs in the Western, Mid-Western and Eastern States, and

of laboratory studies of 14 asphalts furnished by roofing manufacturers as representative of materials sold by them for the

construction of dead-level, mineral-surfaced, built-up roofs.

Three samples of coal-tar pitch, furnished by two producers as

representing eastern and western production of one and eastern

production of the other, were included in some of the laboratory

studies.

While this was primarily a study of asphalts intended for

use in the construction of low-pitched, mineral-surfaced, builtup roofs, it was considered essential for proper evaluation to

compare the behavior of asphalt and coal-tar-pitch roofs in the

field and to compare the results of laboratory tests on representative samples of asphalt and coal-tar pitch where such

tests were applicable to both materials.

Complete details of the field studies are described in

Appendix 1 of this report and of the laboratory studies in

Appendix 2. Appendix 3 contains a discussion of the requirements in the proposed specification for asphalts for low-slope

roof s

.

II. SUMMARY AND CONCLUSIONS

A, Field Studies

Figure 1 shows graphically the results of the field studies.

In this and subsequent graphs, length of service is plotted

against 100 minus the numerical rating; consequently, the lower

thb slope of the curve, the better the performance rating.

Figures 2 to 7 and Table 2, Appendix 1, show details of the

field studies in the various areas. No data are shown for

coal-tar-pitch roofs on the West Coast because coal-tar pitch

has become generally available there only recently 0
.
o

pr

<

GZ

O

QZ

kJ

hkJ

Q

0 10 20 30 40

EXPOSURE, YEARS

FIGURE 1. RESULTS OF FIELD STUDY.

2

Conclusions drawn from the field studies were:

1. Numerous low-pitched, mineral-surfaced, asphalt and coaltar pitch, built-up roofs were observed in good, serviceable condition in all areas after more than twenty years

of exposure. Roofs of both types thirty years old were

not uncommon.

2. Coal-tar-pitch roofs were rated slightly higher, generally,

than asphalt roofs, in the Eastern and Mid-Western States,

This was most apparent in roofs exposed more than twenty

years.

3. Asphalt roofs in the Eastern and Mid -We stern States were

rated significantly higher than those in the Western States,

Asphalt roofs in the Mid-Western States were rated slightly

higher than those in the Eastern States.

4. It is our strong opinion that good service from any conventional, bituminous, built-up roof depends more on

initial workmanship and subsequent maintenance than on

the materials that are used. This conclusion is not entirely a product of this investigation, but is based,

rather, on considerable field experience.

B„ Laboratory Studies

In any appraisal of the results of these laboratory

studies, it should be borne in mind that specifications for

asphalt and coal-tar pitch have always been based largely on

physical characteristics. Through the years specifications

have evolved which insure materials that can be handled well,

will stay in place on a roof, etc.

,

but which give no

assurance of the "quality" of the product, if one defines

"quality" as service on a roof. That there is no general

agreement, even as regards physical characteristics, is

shown by the wide variations in the properties of the materials submitted for these tests.

We have made the standard tests to determine properties

that are usually listed in purchase specifications. In

addition, we have made other tests, many of which show
.

.
- 3

-

differences among the materials tested. Some of these tests

are reported here for the first time. We would expect that

different bituminous technologists would interpret the results of some of these tests differently.

Conclusions drawn from the laboratory studies are;

1. Types of Asphalt : Two types of asphalt are being furnished

by roofing manufacturers for low-slope, mineral-surfaced,

built-up roofs. Type I is largely characteristic of

asphalt produced for many years for this use. Type II

asphalt is characterized chiefly by high ductility at

77°F, embrittlement at 40°F, and a higher susceptibility

factor than Type I asphalt. Eleven samples of Type I

and three samples of Type II asphalt were furnished by

manufacturers for this study.

2. Compliance with current specifications ; All specimens of

Type I asphalt submitted complied with the requirements

of Federal Specification SS-A-666, Type 1, Class A, for

surfaced, built-up roofs, except in minor respects, and

all complied with American Society for Testing Materials

Specification D312, "Mineral-Surfaced Flat".

The three Type II asphalts complied with Federal Specification SS-A-666, Type 1, Class A, except for penetration at 32°F and 77°F. They complied with A.S.T.M.

Specification D312, "Mineral-Surfaced Flat", except

that for two of them the penetration at 77°F was lower

than the minimum specified.

The three samples of coal-tar pitch complied with Federal

Specif ication' R-P-381 , Type I, for built-up roofing.

3. Component distribution in asphalts : The component distribution in asphalts cannot be used alone as a criterion

of quality.

4. Deterioration tests : 4.1 Accelerated weathering tests (Exposure to heat,

light and water):

4.1.1 Hardening: Both asphalts and coal-tar pitches

showed marked hardening as evidenced by increases in

softening point.
,* •

.
- 4 -

4 . 1.2 Shrinkage: The asphalts showed varying amounts of

shrinkage on long exposure. The two that shrank most

gave positive "spot" tests and contained the largest percentage of matter insoluble in n-pentane. The coal-tar

pitches showed no detectable shrinkage on long exposure.

4.1.3 Matter insoluble in n-pentane: All asphalts

showed marked increases in matter insoluble in n-pentane

on long exposure.

4.1.4 Photochemical reactions: Water-soluble acidic

compounds formed from the asphalts were markedly greater

than those from the pitches. The relatively large amounts

of acidic materials formed when asphalts are exposed to

light and moisture emphasize the very important role of

mineral-surfacing materials in built-up roofs.

4.1.5 Self-healing characteristics: Both asphalts and

coal-tar pitches exhibited self-healing properties after

4500 hours of accelerated weathering. The coal-tar-pitch

specimens healed more rapidly than the asphalt specimens

in all cases. Variations in the rate of self-healing

among the asphalts could not be attributed to the type

of asphalt.

4.2 Outdoor weathering tests:

4.2.1 Hardening: Both asphalts and coal-tar pitches

hardened during outdoor exposures as evidenced by increases in softening point.

4.2.2 Self-healing: Both asphalt and coal-tar pitch

exhibited self-healing properties during summer exposures;

neither showed self-healing properties during winter

exposure s

.

4.3 Heat susceptibility tests (Exposure to heat along):

4.3.1 Component distribution: Changes in the component

distribution of the asphalts when exposed to heat alone

were essentially the same as those found by exposure to

accelerated weathering.
,* .
- 5 -

4.4 Water absorption tests:

4.4.1 Long-time immersion: The amounts of water absorbed

by the asphalts in long-time immersion tests varied widely,

but were not indicative of the type or source of asphalt.

The water absorption of the coal-tar pitches fell within

the range of the asphalts that absorbed the least.

From 0.05 to 0.1 ml of o.Ol N alkali solution was required to neutralize material leached from each of the

asphalts and the coal-tar pitch. This is in marked contrast to the results of the accelerated weathering test

(Exposure 3) where from 20 to 80 ml of 0.01 N alkali

were required to neutralize the material formed from

different asphalt specimens during 900 hours of exposure.

Only 1.6 ml of 0.01 N alkali were required to neutralize

material formed from the different coal-tar pitches exposed similarly.

5. Specification : Laboratory examination of the asphalts

furnished indicates the desirability of a specification covering two types of asphalt, with requirements

that are more restrictive than those of the Federal

and A.S.T.M. specifications. A study of specifications

furnished by manufacturers lends weight to this conclusion.

III. PROPOSED SPECIFICATION FOR ASPHALT

FOR LOW-SLOPE ROOFS

Table 1 lists chemical and physical requirements of two

types of asphalt for use in the construction of mineralsurfaced, built-up roofs on slopes up to one inch per foot.

Type I asphalts are characteristic of low-slope asphalts

covered by Federal and A.S.T.M. specifications, but the

requirements in the proposed specification are more restrictive than in either of those specifications. Type II

asphalts are processed to approximate, initially, some of

the physical characteristics of coal-tar pitch, notably,

high ductility at 77°F.

TABLE 1. PROPOSED SPECIFICATION FOR ASPHALT

FOR LOW-SLOPE ROOFS.

Type I II

Min. Max. Min, Max.

Softening point (R & B),—^ °F

Ductility at 77° F-i/, 5 cm/

135 1^5 135 145

min. , cm. 15 100

Ductility at 40°F, 0.25 cm/

min. , cm. 3 —

Pene tr at ion-2/ at

32°F, 200 g, 60 sec. 10 5

77° F, 100 g, 5 sec. 25 60 15 25

115°F, 50 g, 5 sec.

Weight loss, 5 hrs. at 325°F—

%

100

ir\ O o 90

0.5

Penetration of residue at 77°F,

percent of original

Bitumen soluble in CC11+ , %

85 75

99

30

99

30

Bitumen insoluble in

n-pentaneL^ J0 Flow test at l40°F,

5 hrs .2^ cm. 2 9 2 9

Spot test.8/

Susceptibility factor^/ 2

Negative

5

Negative

Flash point, C.O.C.—^ °F 375 375

(Methods of Tests)

1 /

2/

V

b/

1/ —^N.B.S . RF-2577.

A.S.T,,M. D36.

A.S.T,»M. D113. 8/

A.S.T,,M. D5o

A.S.T,,M. D6. 1/

A.S.T,,M. D4.

(Modified ) . A. A.S.H. 0. T102

(“Naphtha)

.

10/A.S . T .M. D92.

Pen, at 115°F - Pen, at 32°F

Pen. at 77°F

- 6 -

The proposed specification contains some requirements

that are not normally included in specifications for asphalt

for use in the construction of built-up roofs, namely,

matter insoluble in n-pentane , spot test, susceptibility

factor, and flow test, applicable to both types. In addition, a minimum requirement for ductility at 40°F is included for Type I asphalt. The significance of the specification requirements is discussed in Appendix 3- under

"Discussion of Requirements in the Proposed Specification

for Asphalts for Low-Slope Roofs".

Type I asphalt should be readily available in all

areas. Type II asphalts have been available nationally

for a relatively short time. Consequently, most of the

long-service roofs reported in the field study were of

Type I asphalt.

IV. ACKNOWLEDGMENT

The authors acknowledge the assistance of the Asphalt

Roofing Industry Bureau in furnishing the list of older

asphalt roofs of known history, and of manufacturers of

asphalt and coal-tar-pitch roofings for the locations of

roofs, assistance in making inspections, and the samples

of asphalt and coal-tar pitch that they furnished. The

assistance of Dr. William S. Connor of the Applied Mathematics Division, N.B.S., in the statistical aspects of

the field survey is also acknowledged.
I

I

1

I
- 7 -

APPENDIX 1. FIELD STUDIES OF BUILT-UP ROOFS

1. Introduction

In planning the field studies of built-up roofs, the

following criteria were established as of primary importance:

a) The inspection areas should represent the widely

different climatic conditions in the United States,

b) The asphalt roofs should represent the principal

sources of asphalt used in this country,

c) Only roofs of known history should be examined,

d) The system for selecting roofs for inspection

should be entirely unbiased,

e) The system of rating the condition of a roof

should be on a numerical basis.

It was realized of course that many factors other than

the quality of the bitumen must be considered in evaluating

the performance of built-up roofs and that serious defects

may occur that are in no sense related to the quality or

kind of bitumen used. For example, it is our opinion that

more premature roof failures are caused by faulty workmanship than by faulty materials. Proper maintenance is also

of great importance in determining the service of any builtup roof.

While the principal purpose of this field study was to

evaluate the performance of mineral-surfaced, built-up

roofs on low slopes, other roofs of particular interest

were inspected where available. Among these were: smoothsurfaced, built-up roofs; built-up roofs in which glass mat

replaced the conventional felts; double-surfaced, built-up

roofs; and one application of an elastomeric sheet (Neoprene)

on a concrete deck. This report is confined to conventional

mineral-surfaced, built-up roofs.
»mm
- 8 -

2. Selection of Roofs for Inspection

In order to obtain roofs of known history for inspection, it was necessary to rely upon the roofing industry,, The

Asphalt Roofing Industry Bureau furnished a list of 86 mineralsurfaced, asphalt, built-up roofs known to be 10 years old or

older. Individual manufacturers of asphalt roofings who

submitted asphalt specimens furnished lists of more than

400 such roofs applied with the asphalts they are selling

currently, all less than two years old. Manufacturers of

coal-tar pitch furnished the locations of coal-tar pitch

roofs in the inspection areas. Frequently the local representatives of the roofing manufacturers and roofing contractors were able to point to older roofs of known history.

As it was obviously impracticable to inspect all of

the roofs suggested, the initial list of older roofs was

divided into three geographical areas, East Coast, Mid-West,

and West Coast, and each of these groups were broken down

into seven sub-groups, by age, as follows: Less than 10

years, 10 to 12, 13 to 15, 16 to 18, 19 to 21, 22 to 24, and

25 years and older. Actual rodfs to be inspected were

selected by lot from each sub-group. Where it was found

that a roof selected had been destroyed or reroofed, an

attempt was made to find a replacement. One-hundred-one

mineral- surfaced , built-up roofs were inspected in this

study, distributed as shown in Table 2.

TABLE 2. DISTRIBUTION OF ROOFS INSPECTED

ASPHALT ROOFS

Location: East Coast Mid-We st West Coast

Age, Yrs. No. No. No.

10 or less 2 3 5

10 to 20 11 10 4

20 to 30 5 9 8

+30 1

COAL-TAR-PITCH ROOFS

Age, Yrs. No. No.

10 or less 6

10 to 20 10

20 to 30 6

+30 1

7

5

7

1

No.
'
- 9

-

3o Areas Included in the Studies

Inspections were made in 23 cities in 16 States and the

District of Columbia, as follows:

1, Seattle and Tacoma, Washington,

2 0 San Francisco and Los Angeles, California.

3. Albuquerque, New Mexico.

4 0 El Paso, Texas.

5. Kansas City, Missouri.

6. Kansas City and Wichita, Kansas.

7. New Orleans, Louisiana.

8. Oklahoma City, Oklahoma.

9. Jacksonville, Florida.

10. Atlanta and Macon, Georgia.

11. Columbia, South Carolina.

12. Gastonia and Red Springs, North Carolina.

13. Washington, D. C.

14. Baltimore, Maryland.

15. Marion and Columbus, Ohio.

16. Philadelphia, Pennsylvania.

17. New York, New York.

b. Methods of Inspecting and Rating Roofs

Practically all roofs were inspected in company with a representative of the manufacturer of the roofing materials

and, frequently, with the owner or manager of the building.

In order to secure the greatest possible uniformity in

the inspections a form was developed which included the history of the roof and a check list of the elements that are

important in a built-up roof. Each element was rated numeri

cally in accordance with its importance as a factor in deter

mining the condition of the roof. A copy of the inspection

form with the ratings assigned to the various elements

follows

:

10

1 .

3 .

5 .

8 .

9 . 11 . 12 . 13.

14.

15 . 16 . 17.

18 .

1 .

2 .

3 .

4 .

ROOF INSPECTION FORM

Historical

Date

Rating

Building 2. Location

Used for 4. Year Applied

Slone 6. Sunshine

Roofing Contractor

Index 7. Rainfall Index

Manufacturer o ©

i

—

1

1 Spec. No.

Bonded: Yes No 10 15 20

Deck: Wood Concrete Metal Gypsum Other

Type of Felt Flys 2 3 4 5

Insulation: Yes No Type Thickness

Character of Bitumen: Asphalt Coal Tar Other

Source ______ Soft. Pt. Pen. _____ Duct. Other

Wt. of Bitumen per square: Between plies Top pouring

History of Repairs

Observations

Water Tightness: No leaks (8) Leaks with long-continued

rain (4) Leaks every rain (0) Cause:

Repaired Areas: None (10) Few (5) Many (0)

Nature:

Blistering: None (12) Moderate (6) Serious (0)

Between plies Between deck & membrane

Remarks:

Cracking of

Remarks

:

Felts: None (12)_ Few (6) Many ( 0

)

Surfacing:

Poor (0)

Adhesion to Bitumen:

Remarks

:

5 . Good (4) Fair (2)

11

ROOF INSPECTION FORM (Continued)

6 0 Bare Areas: None (6) Few (I ) Many (0)_

7<, Felts: Good (8) Fair (4) Poor (0)

Condition:

8 0 Bitumen: Areas water standing or likely to stand:

a) Condition: Good (4) Fair (2) _____ Poor (0)

b) Hardness: Soft (2) Medium (1) Hard (0)

c) Blisters, Pits, etc: None (2) Few (1) Many (0)

d) Alligatored: None (6) Moderately (3) Severely (0)

e) Cracking, Flaking, etc: None (6) Moderate (3)

Severe (0) Other Observations : 9o Bitumen: Areas water unlikely to stand:

a) Condition: Good (4) Fair (2) Poor (0)

b) Hardness: Soft (2) Medium (1) Hard (0)

c) Blisters, Pits, etc: None (2) Few (1) _____ Many (0)

d) Alligatored: None (6) Moderately (3)

Severely (0)

e) Cracking, Flaking, etc: None (6) Moderate (3)

Severe (0) Other Observations:
.

'
12

Under this system of rating, the various elements are

weighted in accordance with the degree of deterioration. A

roof with no defects would be rated 100 and the final rating

of a roof is the sum of the ratings of the elements. This

system was adopted as the method most likely to insure uniform procedures in the inspections. It is certain that the

numerical ratings are more readily evaluated than mere

descriptive terms.

This rating system might be used as a basis for determining the treatment necessary in long-time maintenance of

built-up roofs, though, obviously, it would not apply universally. The following is a suggested application;

Deterioration Action Indicated

o - 5 Yearly inspection and preventive maintenance »

5

- 15 Yearly inspection and minor maintenance . 15 - 30 Extensive maintenance and minor repair

30 - 50

Above 50

Major repair.

Reroofing probably indicated.

5. Results of Field Studies

The results of the field studies are shown graphically

in Figures 2 to 6 inclusive. The age and deterioration of

each roof inspected are shown by the points in Figures 2 to

6. The positions of the graphs were determined by the method

of least squares and are presented as a means for comparing

the general ratings of asphalt and coal-tar-pitch roofs in

the different areas.
.
DETERIORATION

,

(IOO

-

RATING)

EXPOSURE , YEARS

FIGURE 2. ASPHALT ROOFS EASTERN STATES.

DETERIORATION

*

(IOO

-

RATING!

EXPOSURE, YEARS

FIGURE 3. ASPHALT ROOFS - MID-WESTERN STATES.

DETERIORATION,

(IOO

-RATING)

EXPOSURE, YEARS

FIGURE 4. ASPHALT ROOFS WEST COAST STATES.

DETERIORATION

,

(IOO

-

RATING!

EXPOSURE , YEARS

FIGURE COAL-TAR PITCH ROOFS - EASTERN

STATES.

DETERIORATION

,

(IOO

-

RATING)

50

EXPOSURE , YEARS

FIGURE

'6 . COAL-TAR PITCH ROOFS - MID-WESTERN

STATES.

- 13 -

APPENDIX 2. LABORATORY STUDIES

lo Introduction

The 14 samples of asphalt and 3 samples of coal-tar

pitch were examined in the laboratory by chemical and physical

tests that are normally used to define the characteristics of

asphalts and pitches used in built-up roofs. While limiting

values under these tests may be used in specifications to

control the physical characteristics of asphalts and pitches

to insure materials that can be handled satisfactorily and

will remain in place on a roof, they give no assurance of the

quality of the product, when quality is considered in terms

of long-time service on a roof.

Additional laboratory tests were made to determine

differences among the asphalts and, wherever possible, between

the asphalts and coal-tar pitches. In devising these ’tests,

consideration was given to the conditions to which the bitumens

in low-slope, mineral-surfaced, built-up roofs are subjected.

Among these were exposure to elevated temperatures, alternate

wetting and drying accompanied by sunlight, where water runs

off quickly and where it evaporates in place. That a membrane

may be cracked in cold weather by movements in the roof deck

and subjected to long-continued exposure to water without

sunlight were also considered.

Asphalts, when stored in closed containers at room temperature, are hardened and become more brittle, as evidenced

by increases in softening point and in the amount of material

insoluble in n-pentane , and decreases in the penetration

values. These reactions are accelerated by elevated temperatures and will therefore apply in service to the moppings

between felts as well as to the surface coatings.

Exposure of asphalt to the sun induces a photochemical

reaction at the exposed surface, resulting in a thin surface

film of light-degraded material which is largely soluble in

water. When the slope of a roof is such that water runs off

readily, this light-degraded material is largely removed, the

coating loses weight and weathers to a dull, matt surface.

On roofs where standing water evaporates in place, the lightdegraded material is first dissolved and then deposited as a film when the water evaporates. On further drying, this film

causes a shrinkage of the surface of the coating. So-called

"alligatoring" may result from surface shrinking, with cracking the eventual result.
>• ' >
- 14 -

Cracked coating and mopping layers of bitumen may not be

too important if the bitumen has the ability to "self-heal"

in a reasonable time. Inability to self-heal could result in

early failure of a membrane 0 The flow test and the special

self-healing test are measures of the ability of a bitumen

to self-heal.

Knowledge concerning the importance of the initial

distribution of components or groups of compounds in an

asphalt is insufficient for use in purchase specifications,

but changes in the distribution of components, as in the

increase of n- pentane insoluble matter, give an indication

of the extent of degradation that has occurred

„

The spot test usually appears in specifications for

road asphalts as a control of quality

2. Physical and Chemical Characteristics

In Table 3 are reported the source of the crudes from

which the 14 asphalts included in this study were produced

and the conventional physical and chemical characteristics

normally used in purchase specif ications . These data show

that although the asphalts as a group fall within a narrow

softening point range, other physical characteristics are

markedly different. The ductilities and penetrations at

77°F and 32°F of samples 7 9 12 and 13 indicate the desirability of including two types of material in a purchase

specification. Consequently, asphalts 1, 2, 3 9 4, 5, 6, 8,

9, 10, 11 and 14 will be referred to hereafter as Type I asphalts, and Nos. 7, 12 and 13 as Type II asphalts.

All Type I asphalts complied with the requirements of

Federal Specification SS-A-666, Type I, Class A, for surfaced

built-up roofs, except in minor respects, and all complied

with American Society for Testing Materials Specification

D312, "Mineral-Surfaced Flat".

The three Type II asphalts complied with Federal Specification SS-A-666, Type I, Class A, except for penetration

at 32°F and 77°F. They complied with A.S.T.M, Specification

D312, "Mineral-Surfaced Flat", except that for two of them,

the penetration at 77°F was lower than the minimum specified.
TABLE 3 . PHYSICAL AND CHEMICAL

Ductility—/ Pene trationi/

Sample

No,

Source

of

Crude

Sof t .—

/

Point

(R & B)

At 77°F

5 cm/min.

At 40°F

0.25 cm/min.

77°F

100 g

5 sec

32°F

. 200 g

.

. 60 sec.

115°F

50 g.

5 sec

.

1

OJP cm. cm.

1 Wyo. 145 9 3.3 42 22 117

2

M 148 13 3.5 26 9 90

3

ft 146 23 4.0 29 11 108

4 Texas 158 7 4 .

6

30 17 73

5 Calif

.

144 21 5.4 42 19 132

6 Mid, Con. l4l 38 6.0 31 13 113

7 Calif. 143 150+ 1.512/ 16 5 95

8 Mid, Con. 149 14 4.2 31 12 89

9 Mid. Con. 142 11 3.6 46 22 122

10 Calif

o

146 26 5.7 36 18 130

I 11 Ven. 148 23 4. 6 28 15 98 1

12 Calif. 143 110 Li.O^/ 16 5 99

|

13 l40 150+ Ll.oW 20 7 120

14 Mid. Con. 148 8 3 .

6

4l 21 105 1

1/ A.S.T.M. D-36. 4/ Pen. at 115°F minus Pen. at 32°F I 2/

1/

A.S.T.M. DA.S.T.M. D—

113.

5. 1/

Pen. at 77°F

F. S. SS-S-164 (Modified).

1
CHARACTERISTICS OF ASPHALTS 0

f 3uscepftibility

yactor^t/

Flow at

120°F1/

5 Hr s =

Heat Test, 5 Hrs.^^

at 325°F

Solubility

CarbonJZ/

Disulfide N-PentanelA

Soluble Insoluble

Spot Test^/

Loss

Penetration of

Residue Naphtha

j

cm. X % %

1 2 0 26 2,0 L0.1 40 99.7 30.0 Negative

1 3o11 io 7

m 25 99.7 29.8 n

3.39 2» 2

it 27 99.8 28.5 ti

|! 1 0 86 Oc 7

ii 28 34.4 ii

2 ° 69 1.9 ii 38 — 35.9 Positive

*' 3.23 3 o 6

it 29 — 24.2 Negative

j! 5-62 3 * 6

ii 13 99.8 29 o 7

it

2.48 lc 2

n 30 99.8 30.6 ii

| 2.18 IcO it 43 99.9 27.4 it

I 3 ° 12 1.4 it 36 99.9 41.5 Positive

' 2.96 1.4 it 28 99.9 31.5 Negative

1 5.87 2.4 ii 14 99.7 29.7 it

5.65 4.4 ii 15 — 24.8 n

1

2 -° 5 1.0 it 39 — 27.2 n

6/ A. S . T .M„ D-6 0 %/ AcAcScHoOc T-102 (Naphtha).

7/ AcScToMo D-4. 10/ FractureSc

8/ NcBcSc RP2577.

- 15 -

The three samples of coal-tar pitch complied with

Federal Specification R-P-381, Type I, for built-up roofing.

The examination of these materials also indicated that

the softening point and penetration ranges contained in both

the Federal and A,S.T»M„ specifications for asphalt can be

reduced to insure a better defined material. Although a "susceptibility factor" and flow test are not included in

either the Federal or A,S,T„M 0 specif ications 9 these give

a numerical evaluation of the "relatively susceptible

asphalts" and "self-healing" properties, which the A.S.T.M.

specification states are desirable.

3, Component Distribution

In Table 4 are reported the source of the crudes from

which the asphalts were produced, their softening points,

and components distributions. The component distributions

were determined according to the procedures described in

Research Paper 2 577 ? NBS J, Res, Vol, 54, No, 3, March 1955°

Asphalt samples I to 6, 8 to 11 , and l4 were produced by

vacuum reduction or vacuum reduction accompanied by air

blowing. Samples 7, 12 and 13 were produced by special

processes. Component analysis did not distinguish between

these two types of asphalt.

As reported in a subsequent section of this report,

component analysis can be used to determine changes in

asphalts occurring during accelerated durability exposures.

The asphaltene content as determined by this component

analysis may give some indication of the quality of the

asphalt. Asphalts of the same softening points having the

lower asphaltene content would normally be preferred. When

used in conjunction with the spot test, it could eliminate

materials prepared from cracked residuums.

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16 -

4„ Susceptibility to Heat

Five grams of the asphalts contained in 250 ml beakers

were heated for 10 days at 200°F in an enclosed oven c The

source of the crudes from which the asphalts were produced

and their component distribution before and after exposure

are reported in Table 5° All the asphalts showed marked

susceptibility to heat when evaluated by the increases in

their asphaltene content

„

After exposure at 200°F for ten days, asphalt samples

6, 8, 9 and 14, which had been produced from Mid-Continent

crudes, contained less n-pentane insoluble material

(asphaltenes) than samples 1, 2, 3, 4, 5? 10 and 11, which

had been produced from Wyoming, Texas, Venezuelan and

California crudes 0 These samples would be classified under

Type I material of the suggested specificationo The two

asphalt samples 7 and 12, which were produced from California

crudes and which would be classified as Type II materials

under the suggested specification, showed essentially the

same asphaltene content as samples 5 and 10, Type I materials

which were also produced from California crude oils 0 The

asphaltene content of sample 13, a Type II material, was

slightly higher after exposure than that of asphalts produced

from the Mid-Continent crude oils 0 No detectable weight

losses occurred during the heat exposure . Weight gains in

the order of 0 e 4 percent occurred during these heat exposures

These data indicate the changes that will occur in

the asphalt moppings between the plies of felts as well as

in the top coatings of asphalt built-up roofs, because of

their susceptibility to heat 0

TABLE

5„

DISTRIBUTION

OF

COMPONENTS

IN

ASPHALTS

BEFORE

AFTER

10

DAYS

EXPOSURE

AT

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After

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*

.
17 -

5. Accelerated Durability Exposures

5c 1 Exposure 1

To simulate roof conditions where there are no run-offs

and standing water evaporates in place

The specimens were prepared by depositing a uniform film

of the melted bitumens over the bottom of 3-1/2- X 1-in.

petri dishes. The asphalt specimens were prepared at a spreading rate qf 60 lbs/100 ft 2

; the coal-tar-pitch specimens at a spreading rate of 70 lbs/100 ft 2 .

The coatings were exposed in a horizontal position in

a low- intensity , enclosed carbon arc durability machine (see

Figure 7). They were exposed for 21 hours to light only.

The petri dishes were then filled three-quarters full with

distilled water and re-exposed to the radiation of the arc,

allowing the water to evaporate in place, which required

from 6 to 8 hours. The temperature of the dry specimens

during their exposure was from 125°-130°F.

Shrinkage of coatings during exposure ; The shrinkage

of the coatings from the sides of the dishes after 2500 , 3000, 3500, 4000 and 4500 hours of exposure is reported

in Table 6. Included in this table are the weight changes

which occurred during 4500 hours of exposure.

The coal-tar-pitch coatings showed no shrinkage from

the sides uf the petri dishes after 4500 hours of exposure.

Type I asphalts, samples 6, 8, 9 ? 11 and 14, showed

less shrinkage from the sides of the dishes than samples

1, 2, 3 , 4, 7 and 10, The shrinkages of samples 3 ? 5 and

10 were essentially the same, approximately 0.6 inch, and

were the most pronounced of any of the Type I asphalts.

Samples 7 and 12, Type II, produced from California crudes,

showed much less shrinkage than Type I asphalt, samples 5

and 10, also produced from California crude. Sample 13,

Type II, showed less shrinkage than the averages shown by

Type I asphalts produced from Mid-Continent crudes. Figure

8 shows the shrinkage which occurred after 4500 hours of

exposure in coal-tar-pitch sample 40 and asphalt samples 4,

5 and 11
#

’
"«W

FIGURE ACCELERATED DURABILITY TEST APPARATUS

TABLE

6.

SHRINKAGE

FROM

SIDES

OF

DISH

OF

TEST

SPECIMENS

AND

WEIGHT

CHANGES

IN

ACCELERATED

DURABILITY

TEST„

(EXPOSURE

1)„

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FIGURE 8. EXTREMES IN THE SHRINKAGE OF ASPHALT AND

COAL-TAR-PITCH SPECIMENS AFTER 4500 HOURS

OF EXPOSURE 1.

18 -

Water-soluble, photochemical. degradation products : After

1000 , 3000 , 3500 , 4000 and 4500 hours of exposure to light

the petri dishes were filled with distilled water, allowed to

stand for 18 hours, and the extracted material titrated with

0.01N alkali solution. These data are reported in Table 7 . This titratable material was a photochemical degradation

product. The relative amounts were markedly greater for

the asphalts than for the coal-tar pitches. See Exposure 3

for the amounts of titratable materials formed when they are

removed after each 21-hour exposure to light.

Changes in physical characteristics ; In Table 8 are

reported the softening points and penetrations of the

asphalts before and after exposure. All asphalts showed

marked hardening and embrittlement, as evidenced by the

increases in the softening points and decreases in penetrations ,Changes in distribution of components ; In Table 9 are

reported the component distribution of the asphalts before

and after ^OO-hours exposure (Exposure 1), As in the exposures of the asphalts to heat alone, there were marked increases in the n-pentane insoluble components. Although

these exposures were made at temperatures of 125°-130°F,

which were appreciably lower than maximum roof temperatures,

heat degradation still occurred.

The percentage of n-pentane insoluble material in

samples 6, 8, 9 and 14 after exposure was appreciably lower

than that found in samples 1, 2, 3? 4, 5? 10 and 11. All

of these samples would be classified as Type I materials

under the suggested specification. Samples 7 and 12, Type

II, produced from California crude oils, contained less

n-pentane insoluble material than samples 5 and 10, Type I,

also produced from California crudes. The n-pentane

insoluble content of sample 13, Type II, after exposure,

was slightly less than the average of that formed in samples

6, 8, 9 and 14, produced from Mid -Continent crudes. These

increases in n-pentane insoluble material, which were formed

at the expense of the water-white oils and dark oils, resulted in a hardening of the asphalts as discussed under

"Change in physical characteristics". Asphalts containing

the lesser amounts of n-pentane insoluble material after

exposure would be preferred. For example, if a choice had

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TABLE 80

SOFTENING

POINTS

OF

ASPHALTS

AND

COAL-TAR

PITCHES

AND

PENETRATIONS

OF

ASPHALTS

BEFORE

AND

AFTER

b^OO

HOURS

EXPOSURE

TO

ACCELERATED

DURABILITY

TEST

(EXPOSURE

1).

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After

Exposure 
'

. *
TABLE 90

DISTRIBUTION

OF

COMPONENTS

IN

ASPHALTS

BEFORE

AND

AFTER

4500

HOURS

OF

EXPOSURE

TO

AOCFLERATED

DURABILITY

TEST

(EXPOSURE

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19 -

to be made among samples 5, 7, 10 and 12, all produced from

California crude oils, samples 7 and 12, Type II materials,

would be preferred* By the same reasoning, sample 13 would

be preferred to sample 11*

5.2 Exposure 2

Exposures made to simulate conditions to which a cracked

membrane may be subjected.

The specimens were prepared and exposed as described

under Exposure 1„ At fixed intervals, a groove 1/16 in,

wide was cut through the coatings along a diameter. The

specimens were then exposed dry to the radiation of the arc

until the groove had healed. The temperature of the specimens

during their dry exposures was 125°-135°F. In Table 10 are

reported the extent of self-healing in specimens which had

been exposed for 4500 hours before being grooved. The

self-healing in the coal-tar-pitch coatings was much more

rapid than' in the asphalt specimens. Asphalt samples 2,

3 , 5, 7, 8, 9 ? 10, 11, 13 and l4 showed satisfactory selfhealing within 96 hours of exposure. The percentages reported represent the approximate closure of the grooves

at the times indicated. Asphalt samples 1, 4, 6 and 12

were not included because of lack of space in the test

equipment.

5.3 Exposure 3

Exposures made to simulate roof conditions where watersoluble, light-degraded products were partially removed as

by dew or rain.

Specimens were prepared for this exposure as for Exposure 1, except that the coatings were applied in petri

dishes at a spreading rate of 18 lb/100 ft^, to accelerate

degradation.

The dry specimens were exposed horizontally to radiation from the carbon arc (Figure 7)» After 21 hours of

exposure the petri dishes were filled with water and

allowed to stand, without light, for one hour, and the

water poured off. This process was repeated until the

coatings had been exposed to light for 900 hours. The

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20

coatings were dried and weighed after 200, 400, 600 and 900

hours of exposure, and the accumulated washings to these

periods titrated with 0.01N alkali. The coatings were also

examined for shrinkage. In Table 11 are reported the shrinkage, weight loss and amount of alkali required to neutralize

the water-soluble degradation products after 900 hours of

exposure. The latter is reported as grams of sodium hydroxide

required to neutralize products formed on 100 sq. ft. of

exposed surface.

Marked differences were noted between the results of

Exposure 1, where light-degraded products were partially

dissolved and redeposited on the coatings, and of Exposure

3, where these products were partially removed daily. In

Exposure 1, the alkali required to neutralize the lightdegraded material formed from the asphalts during 1000 hours

of exposure varied from 3 to 9 grams per 100 ft^; in Exposure 3 , 18 to 66 grams were required after 900 hours of

exposure. A number of the asphalts showed slight weight

gains after 4500 hours under Exposure 1; all showed

progressively greater weight losses at the 200, 400, 600

and 900 hour weighing periods of Exposure 3° The relationship of the weight losses in Exposure 3 to the amounts of

alkali required to neutralize the water-soluble degradation

products indicates strongly that the weight losses were due

largely to the removal of water-soluble products.

In another investigation here it has been shown that

asphalts exposed to radiation from the carbon arc and

washed daily continued to lose weight during an exposure

of 4500 hours duration. Similarly, specimens exposed

outdoors and weighed at intervals of 6 months, continued

to lose weight during a 3-year exposure. Since the

formation of water-soluble degradation products is a light-induced reaction, the value of opaque mineral

surfacing for any asphalt roof is obvious.

Practically no shrinkage occurred in any of the

asphalts during Exposure 3 <» This is in marked contrast

to their behavior in Exposure 1, indicating that the redeposited, water-soluble, degradation products caused the

shrinkage. In Exposure 3 the asphalts weathered to a dull, matt surface; in Exposure 1, the surfaces were dull

and wrinkled.
*

> '
21

As in Exposure 1, the coal-tar pitches in Exposure 3

showed markedly less light-degraded materials formed than

the asphalts. The daily removal of the light-degraded materials from the pitches did not increase appreciably the

amounts of these materials that were formed. Weight losses

of the coal-tar-pitch specimens were confined to the first

200 hours of Exposure 3

Changes in the component distribution of the asphalts

during 900 hours of Exposure 3 are shown in Table 12. These

changes paralleled those in Exposure 1, with asphalts 5 and

10, produced from California crudes, showing the largest

amounts of matter insoluble in n-pentane at the end of the

test. Again, Type I asphalts 6, 8, 9 and l4, produced from

Mid-Continent crudes, contained less matter insoluble in

n-pentane than the other Type I asphalts. Of all of the

asphalts, No. 13, Type II, contained the smallest amount of

matter insoluble in n-pentane. The other Type II asphalts,

7 and 12, produced from California crudes, contained less

than Type I asphalts 5 and 10, also produced from California

crudes.

6. Outdoor Exposures

Changes in Physical Characteristics : In Table 13 are

reported the softening points and penetrations of the asphalts

before and after 10 months of exposure outdoors.

For the outdoor exposure the specimens were prepared as

for Exposure 1. They were exposed in a horizontal position

on the roof of the Industrial Building, National Bureau of

Standards, during May 1956. The length of the exposure was

10 months.

At the end" of the 10-month, outdoor exposure all asphalts

showed a marked increase in softening point and a corresponding decrease in penetration values. The increases in softening point ranged from 13 ° to 21°F , and were apparently not

related to the initial softening points of the asphalts or to

the source of the crudes from which the asphalts were produced

These data indicate that asphalts having softening points near

the minimum specification requirement would be preferred to

those whose softening points were near the maximum requirement

The coal-tar-pitch specimens also showed an increase in soften

ing point after the 10-month exposure. The maximum increase

was 7°F.

TABLE

11.

SHRINKAGE,

WEIGHT

LOSS,

AND

MATERIALS

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WITH

ALKALI

FORMED

AFTER

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13.

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POINTS

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ASPHALTS

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22

Shrinkage : Since these exposures were of such short

duration, only traces of shrinkage of the asphalt coatings

from the sides of the petri dishes occurred,. No shrinkage

was detected in the coal-tar-pitch specimens.

Self-healing characteristics ; To determine self-healing

ability the specimens were grooved, as for Exposure 2, before

exposure on May 22, 1956. Both asphalt and coal-tar specimens

healed within 24 hours. Specimens were grooved again on July

12, 1956, and again all specimens healed within 24 hours.

Specimens were grooved again November 8, 1956, and when inspected on December 31, 1956, no self-healing was detected

in either the asphalt or coal-tar pitch specimens. Inspection on February 27, 1957, showed evidence of incomplete selfhealing in sample 7

On March 18, 1957, when the exposure was terminated, the

asphalt specimens were essentially the same as in the previous inspection. The coal-tar-pitch specimens showed some

self-healing. These data indicate that little or no selfhealing can be expected from either asphalt or coal-tar

pitch during cold weather.

7. Water Absorption Tests

The water absorption tests were made on the asphalts

and coal-tar pitches to determine the amount of water absorbed during long-time immersion in distilled water, A

further objective was to determine the amount of alkali required to neutralize material leached from the specimens

during immersion.

Approximately 25 grams of asphalt and 30 grams of coaltar pitch werq melted, poured into molds, forming disks with

a surface area of approximately 0.11 ft 2 , Each disk was

weighed, placed in a separate petri dish, and covered with

distilled water. The disks were removed from the water at

intervals, blotted dry, and reweighed. Any gain in weight

was taken as the quantity of water absorbed during the period.

The total amount of water absorbed per 100 ft 2 of exposed

surface in one year is shown in Table 14.

TABLE

Ilf.

RESULTS

OF

WATER-ABSORPTION

TESTS

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23

After immersion for one year, the water in which each

specimen was immersed was titrated with 0.01N sodium

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leached per 100 ft2 during one year of immersion.

All specimens were glossy black after one year of

immersion.

24 -

APPENDIX 3. DISCUSSION OF REQUIREMENTS IN THE PROPOSED

SPECIFICATION FOR ASPHALTS FOR LOW-SLOPE

ROOFS

1. Conventional Requirements

Softening point ; All of the asphalts submitted in this

program had softening points within the range of l40°F to

l65°F specified in Federal Specification SS-A-666, Type I,

Class A, for surfaced built-up roofs, and all but sample 4

(158°F) within the range of 135°F to 150°F specified by

A.S.T.M. Specification D312, "Mineral-Surfaced Flat". We

believe that a softening point range of 135°F to l45°F will

insure, in large measure, asphalts of desirable qualities for

low-slope roofs.

Ductility at 77°F ; Federal Specification SS-A-666, Type

I, Class A, requires a minimum ductility at 77°F of 5 cm. and

A.S.T.M. Specification D312, "Mineral-Surfaced Flat", a minimum ductility of 10 cm. While five of the Type I asphalts

had a ductility lower than 17 cm. at 77°F, as suggested in

the proposed specification, four of these showed softening

points higher than the maximum specified. We believe that

these asphalts would have met the higher ductility requirement

if they had been processed to meet the softening point requirement in the proposed specification.

The high ductility at 77°F of asphalts 7, 12 and 13

indicates that these asphalts have been processed to simulate

some of the physical characteristics of coal-tar pitch used

in low-slope roofs. The relatively high ductility of asphalts

of this type makes mandatory the inclusion of two types of

asphalt in the specification.

Penetration tests :

At 32°F: The Federal and A.S.T.M. Specification requirements of 10 and 5 ? respectively, can be raised safely to 15

for Type I asphalts. This higher value is more likely to

insure desirable self-healing qualities. Examination of the

three Type II asphalts indicated a minimum penetration requirement at 32°F of 5.

- 25 -

At 77°F: The penetration limits of 25 to 60 suggested

are in line with the softening point and the penetration

values of the Type I asphalts tested . These limits also

provide a means for differentiating between Type I and Type

II asphalts. Limits of 15 to 25 are indicated for Type II

asphalts from the samples tested.

At H5°Fs Federal Specification SS-A-666, Type I, contains no requirement for penetration at 115°F„ Since a self-healing material is desired, a minimum requirement of

100, for Type I asphalt, as specified in A.S.T.M. Specification D312, "Mineral-Surfaced Flat", is considered desirable.

Tests indicate a minimum of 90 for Type II asphalts.

Weight loss. 5 hrs. at 32°F ; Tests of numerous asphalts

have indicated that the maximum requirement of 1.5% in the

Federal and A.S.T.M. Specifications for this test is entirely

unrealistic. The loss on heating of each of the Type I and

Type II samples tested in this series was less than 0.1%.

Consequently, the proposed maximum was placed at 0.5%«

Penetration at 77°F after heating : Here again the require melrt^of-I^T~ofthe^ 77°F before heating,

in both Federal and A.S.T.M. Specifications, is known to be

unrealistic. Minimums of 85% and 75% for Types I and II

asphalts, respectively, are more realistic.

Bitumen soluble in CC14: The requirement of 99% bitumen

soluble m caroon tetrachloride is standard for unfilled

petroleum asphalts.

2. New Requirements

Matter insoluble in n-pentane : The percentage of matter

insoluble in n-pentane is known to increase as the blowing

operation is continued; consequently, a minimum requirement

for the amount of material insoluble in n-pentane could control the extent of blowing. Large percentages of matter

insoluble in pentane are characteristic of "cracked residuums",

generally regarded as having poor resistance to weathering.

26 -

The two asphalts in the series tested that initially

contained the largest percentage of matter insoluble in

n-pentane a^so gave positive spot tests, showed the greatest

shrinkage under Exposure 1, and were included in the three

that required the most alkali to neutralize water-soluble

degradation products formed in Exposure 3 „ It is significant

also that the percentage of matter insoluble in n-pentane

increased in all asphalts during the accelerated and outdoor

weathering tests and the heat tests.

Spot test : The spot test has been used largely in

specifications for road asphalts to eliminate cracked residuums. It is believed that it can serve the same purpose

for roofing asphalts. Note the reference to the two asphalts

that gave positive spot tests, under "Matter insoluble in

n-pentane "

Susceptibility factor : The susceptibility factor requires

no extra laboratory work since it is calculated from the penetration determinations. Inclusion of minimum requirements for

a susceptibility factor serves to distinguish between Type I

and Type II asphalts and places numerical values on the

"relatively susceptible" and "self-healing" properties described in A.S.T.M. specifications.

Flow test : The flow test, adapted from Federal Specific at ion~SS^S^l 64, "Sealer; Hot-Poured Type, for Joints in

Concrete", was included in an attempt to insure asphalts

with good self-healing qualities.

Ductility at 40°F. 0.25 cm/min, : The principal purpose

served by this requirement is to distinguish between Type I and Type II asphalts. All samples of Type II asphalt and all

of the samples of coal-tar pitch tested fractured rather than

stretched in this test; all samples of Type I asphalt met the

requirement for the test.
'*
U. S. DEPARTMENT OF COMMERCE

Sinclair Weeks, Secretury 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 field laboratories in Boulder, Colorado, is suggested in the following listing of

the divisions and sections engaged in technical work. In general, each section carries out spe- cialized 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 front cover of this report,

WASHINGTON, D. C.

Electricity and Electronics. Resistance and Reactance. Electron Tubes. Electrical Instruments. Magnetic Measurements. Dielectrics. Engineering Electronics. Electronic Instrumentation

Electrochemistry.

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

Technology. Length Engineering Metrology.

Heat and Power. Temperature Physics. Thermodynamics. Cryogenic Physics. Rheology

and Lubrication. Engine Fuels.

Atomic and Radiation Physics. Spectroscopy. Radiometry. Mass Spectrometry. Solid State Physics. Electron Physics. Atomic Physics. Nuclear Physics. Radioactivity, X-rays. Betatron

Nucleonic Instrumentation, Radiological Equipment. AEC Radiation Instruments. Chemistry. Organic Coatings. Surface Chemistry. Organic Chemistry. Analytical Chemistry.

Inorganic Chemistry. Elect rodeposition. Gas Chemistry. Physical Chemistry. Thermochemistry. Spectrochemistry Pure Substances.

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

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

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

Metallurgy. Thermal Metallurgy. Chemical Metallurgy. Mechanical Metallurgy Corrosion

Metal Physics

Mineral Products. Engineering Ceramics. (Mass. Refractories. Enameled Metals. Concreting

Materials. Constitution and Microstructure

Building Technology. Structural Engineering. Fire Protection. Heating and Air (modi

tinning. Floor, Roof, and Wall Coverings, Codes and Specifications.

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

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

Circuitry, Digital Systems Analogue Systems. Application Engineering.

• Office of Basic Instrumentation • Office of Weights and MeasureBOULDER, COLORADO

Cryogenir Engineering. Cryogenic Equipment. Cryogenic Processes, properties of Materials

Gas Liquefaction

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

Propagation Services Sun-Earth Relationships.

Radio Propagation Engineering. Data Reduction Instrumentation. Modulation systems.

Navigation Systems. Radio Noise Tropospheric Measurements. 1 ropospherir Analysis Radio

Systems Application Engineering.

Radio Standards. Radio Frequencies Microwave Frequencies. High Frequency Fleet ricai Standards. Radio Broadcast Service High Frequency Impedance Standards. Calibration

C . riter Microwave Physics. Microwave Circuit 'standards.