NATIONAL BUREAU OF STANDARDS REPORT

5224

STAIN INDICES OF TWENTY- ONE ASPHALTS

FIRST SUPPLEMENT TO NBS REPORT NO. 4732

REPORT ON THE EVALUATION OF TWENTY- ONE

COATING- GRADE ROOFING ASPHALTS

by

Sidney H. Greenfeld

and

Shigeru Ishihara

<NB§>

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
U. S. DEPARTMENT OF COMMERCE

Sinclair Weeks, Secretary

NATIONAL BUREAU OF STANDARDS

A. Y. Astin, Director THE NATIONAL BUREAU OF STANDARDS

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WASHINGTON, D. C.

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NATIONAL BUREAU OF STANDARDS REPORT

NBS PROJECT NBS REPORT

1004-11-1017 April 1, 1957 5224

STAIN INDICES OF TWENTY-ONE ASPHALTS

FIRST SUPPLEMENT TO NBS REPORT NO. 4732

REPORT ON THE EVALUATION OF TWENTY- ONE

COATING- GRADE ROOFING ASPHALTS

by

Sidney H. Greenfeld

and

Shigeru Ishihara

Research Associates

Asphalt Roofing Industry Bureau

Floor, Roof and Wall Coverings Section

Building Technology Division

Jointly Sponsored by

Asphalt Roofing Industry Bureau

and

National Bureau of Standards

IMPORTANT NOTICE

NATIONAL BUREAU OF S

intended for use within the

to additional evaluation and

listing of this Report, eithei the Office of the Director, h however, by the Governmen

to reproduce additional cop

Approved for public release by the

Director of the National Institute of

Standards and Technology (NIST)

on October 9, 2015.

progress accounting documents

irmally published it is subjected

, reproduction, or open-literature

ision is obtained in writing from Such permission is not needed, prepared if that agency wishes

<NBS>

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

STAIN INDICES OF TWENTY- ONE ASPHALTS

FIRST SUPPLEMENT TO NBS REPORT NO. 4732

REPORT ON THE EVALUATION OF TWENTY-ONE

COATING- GRADE ROOFING ASPHALTS

by

Sidney H c Greenfeld

and

Shigeru Ishihara

ABSTRACT

The stain indices of the 21 asphalts discussed in

NBS Report No. 4732 were measured in accordance with

A.S.T.M. Procedure D1328-54T. The indices ranged from

4 to 26. No correlation was found between stain index

and penetration, softening point or durability. Reasons

for this lack of correlation are discussed.

1. INTRODUCTION

On 1 July 1956 a report was sent to the Research Committee

describing the properties and weathering characteristics of 21

1 /

coating-grade roofing asphalts. Subsequent work on the mechanism

of the weathering of asphalt indicated that one phase of weathering was related to the ability of some of the components of the

maltenes to migrate to the surface of the exposed coating and

17

"Report on the Evaluation of Twenty-One Coating-Grade Roofing

Asphalts", NBS Report No. 4732, 1 July 1956.

2

react with oxygen in the presence of light. It was proposed to

investigate the use of the stain index determination, ASTM

D1328-54T (Staining Properties of Asphalts), as a measure of the

migration because it measures the movement of some of the component oils to the surface of the asphalt.

2 . EXPERIMENTAL

The apparatus and conditions of test are described in ASTM

„

. 2 / D1328-54T.-

The asphalts are those discussed in detail in NBS Report No.

4732.

3. RESULTS AND DISCUSSION

The results, the average of two determinations differing by

no more than two papers, of the stain index determinations are

compiled in Table 1, along with some of the other characteristics

of the 21 asphalts. The stain indices varied from 26 for Ambit

asphalt to 4 for C810. However, except for the highest and

lowest two, all of the indices fell within the range of 10 to 20.

Thus, the stain index, like many of the other attributes of blown

asphalts, appears to be more characteristic of the type of material than of any individual specimen of that type, and an average

of 15 ±5 papers seems to be characteristic of air-blown coatinggrade asphalts.

2 / “ ASTM D1328-54T , Staining Properties of Asphalt, 1690-1694,

Part 3 of ASTM Book of Standards, 1955-

TABLE

1.

PROPERTIES

OF

ASPHALTS

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- 4 -

The processing of the four asphalts outside of this range

differed in some respects from that of the other asphalts.

Ambit (S.I. = 26) was catalytically blown; 01175 (S.I. = 24)

was reconstituted with reclaimed lube stock; Mexico #12

(S.I. = 8) was not fully blown (S.P. - 196°F); and C8l0

(S.I. = 4) was steam reduced to a penetration of 20/30 before

blowing. Although the asphalt designated "Catalytic" (S.I. ^ l4)

was also catalytically blown (from a Lagunillas flux) , its

properties fell within the normal range.

The stain index represents the farthest penetration of the

aromatic white oils, as observed by their fluorescence under

ultraviolet light. It is believed that during weathering the

oils, both light and dark, migrate to the surface of the asphalt,

where they are degraded in the presence of light. However, the

dark oils are consumed more rapidly than the white oils during

normal weathering. Hence, the movement of the dark oils is

also of interest. The numbers in parentheses in column 2 of

Table 1 represent the farthest movement of the dark oils during

the stain index determination. The dark oils stained between

two and six, usually four, papers less than the white oils.

Because diffusion varies with the square root of the molecular

weight, one would expect the dark oils, because of their higher

molecular weight, to diffuse less than the white oils under the

same conditions. This qualitative deduction and observation are

- 5 -

borne out quantitatively for the two asphalts for which molecular

weight data are available. In NBS Report No. 486l^'

/

the molecular

weights for these components of asphalts C210 and M200 were reported as follows:

0210 M200

White Oils 450 500

Dark Oils 7*+5 900

The ratio of the square roots of the molecular weights of the light

and dark oils of C210 is 0.778 and that for those of M200 is 0.746,

whereas, the ratios of the papers stained are 0.724 and 0.702, for

the two asphalts, respectively. Considering the tolerances in

both determinations, this agreement is very good.

However, when an attempt is made to compare these two asphalts

or to correlate stain index with the usual rheological properties

or durability, difficulties are encountered. Asphalt M200 contains

higher molecular weight oils and also has a higher stain index.

There also seems to be no relation between stain index and penetrations, penetration index or softening point, the rheological

properties by which asphalts are usually characterized. The

reasons for this lack of correlation, especially in a qualitative

sense, are not clear, for it would be expected that the softer,

higher-penetration asphalts would have more of the light, more

17"The Chemical Changes Occurring During the Degradation of Two

Coating Asphalts", N.B.S. Report No. 4861, 1 October 1956.

- 6 -

fluid oils and, consequently, a higher stain index. Apparently,

the forces that hold an asphalt together, i.e., the ability of

the asphaltenes to hold on to the oils, are sufficiently strong

to distort the effects of diffusion.

This property is also related to the durability of asphalt,

for it has been observed that it is very difficult to separate

the maltenes from the asphaltenes in asphalts that weather well.

However, there is no apparent correlation between durability,

as presently determined, or weight loss, and stain index.

In summary, it may be concluded that there is no apparent

correlation between stain index and durability, weight loss, or

any of the rheological properties of coating-grade asphalts

normally measured.
" /
THE NATIONAL BUREAU OF STANDARDS

Functions and Activities

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

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

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

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

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

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

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Reports and Publications

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

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

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

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

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

Standards, Washington 25, D. C.
NBS