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477

The Performance of Roofing

Made With Asplund Felts

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U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

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UNITED STATES DEPARTMENT OF COMMERCE

Maurice H. Stans, Secretary

NATIONAL BUREAU OF STANDARDS • A. V. Astin, Director

NBS TECHNICAL NOTE 477

ISSUED MARCH 1969

The Performance of Roofing

Made With Asplund Felts

Sidney H. Greenfeld

Building Research Division

Institute for Applied Technology

National Bureau of Standards

Washington, D.C. 20234

NBS Technical Notes are designed to supplement the Bureau's regular publications program. They provide a means for making available scientific data that are of transient or limited interest. Technical Notes may be

listed or referred to in the open literature.

For sale by the Superintendent of Documents, Government Printing Office Washington, D.C, 20402 - Price 35 cents
CONTENTS

Page

1. Introduction <, 1

2. Materials ....... 3

2.1 Felts o . . 3

2.2 Asphalts ...» 4

3. Procedures „ 12

3.1 Specimen Preparation 12

3.2 Exposure <> . » 12

3.3 Inspections <.».... 12

4. Results 13

5. Conclusions 14

6. Literature Cited 19

7. Glossary „ 19
THE PERFORMANCE OF ROOFING MADE WITH ASPLUND FELTS

Sidney H. Greenfeld

A study of the durability of roofing made

with Asplund wood fibers was conducted from

1942 to 1967. Concentrations of to 60 percent

wood fibers (oak or pine) prepared by three

variations of the Asplund process were evaluated

All the mineral-surfaced roll roofings and

shingles were performing well after 25 years,

with only four specimens showing more deterioration than the controls (only rags and paper in

their felts) . No differences in performance

could be related to the felt composition.

Key Words: Asphalt, Asplund, felt, mineralsurfaced roll roofing, shingles, wood fibers.

1. Introduction

Organic felts, because of their importance in asphalt roofing

systems, have been the object of continual study by the Asphalt Roofing

Manufacturers Association* since the Association established a Research

Fellowship at the National Bureau of Standards in 1926. At that time

felts were made primarily of rags. Additions of various materials,

such as newspapers and sawdust, were being made to the felt to obtain

flexibility, absorptivity and other properties not found in the largely

rag felts. Wood fibers were being substituted for part of the rags.

These additions and substitutions were made as matters of necessity

before their effects were fully understood. However, the industry was interested in knowing how these materials were affecting the durability

of the systems in which the felts were used. Therefore, they instituted

a felt study under Dr. 0. G. Strieter, their Research Associate at the

NBS, in 1926, which culminated in two publications: one in 1929, on the

production of experimental felts \ 1] and the other in 1936, on the

weathering of saturated felts and smooth- surface roll roofing made from

the experimental felts \ 2] . The conclusion drawn from this early work

was that "there was no significant difference in the resistance to

weathering of asphalt roofing which may be attributed to the kind of

fiber or combination of fibers employed" \ 2] . In 1941, the asphalt

Formerly Asphalt Roofing Industry Bureau

Figures in brackets indicate references at the end of this paper
roofing industry was rapidly increasing its production to meet the demands of the war-time construction boom. The European and Asian sources

of rags were becoming less available, and the Asplund process for defibrating wood had recently been introduced f3] and hesitatingly

accepted by the roofing industry. The industry had performed laboratory

tests and limited exposures of products made with these wood fibers,

but they wanted a controlled, unbiased evaluation of the long-term

effects wood fibers might have on the durability of its products. Consequently, in 1942, a comprehensive exposure program was started under

the Research Associate plan at the National Bureau of Standards by the

Asphalt Roofing Manufacturers Association.

This program was designed to evaluate hard- and soft-wood fibers in

concentrations up to 60 percent of the dry felt weight. The effects of

heat and chemical treatment of the fibers were also studied. Furnishes

containing these wood fibers were commercially processed into saturated

felts, smooth-surface roll roofing, mineral-surfaced roll roofing and

hexagonal shingles, which were exposed to the weather in Minneapolis,

Minnesota; Mobile, Alabama and Washington, D. C. The results of the

saturated- felt and smooth- surface roll roofing exposures were reported

in 1948 [4] . However, all of the mineral- surfaced specimens looked

essentially the same at that time, nor had enough time lapsed for differences to be expected. This report covers 25 years' exposure of these

specimens in Washington, D. C. only; inspections in Minneapolis and

Mobile were discontinued during the 1950 's. The last Mobile inspection

was made in 1950 and the last Minneapolis inspection in 1958. At these

inspections all of the shingles were rated "excellent", but differences

were noted in the roll roofings. The conclusions drawn at the last

Mobile inspection were that felts made with Asplund fibers produced

products that weathered as well as those made with rag and paper felts

and that, if the coarse fiber bundles were removed, "there is no limit

to the quantities of (Asplund wood) fibrous materials that can be incorporated into the felts" (within the range covered by this study)

.

In 1958, the conclusions drawn in Minneapolis were that the shingles were

all in excellent condition and that some blisters and surface cracks were appearing in many of the mineral- surfaced roll roofings. However,

the two specimens with heat treated oak (E-l and E-2 in Table 1) were

still rated "excellent" and those with 30 percent chemically treated

pine and oak were rated "good". All of the specimens had retained the same ratings from 1950 to 1958, leading to the conclusion that the few

blisters and cracks present had appeared early during exposure and had

not gotten appreciably worse during the following eight years' exposure.

3 The specimens were inspected visually by local laboratory people and

rated "excellent", "good", "fair" or "poor" according to their

appearance

.
In attempting to interpret the results of this study, it must be

kept in mind that the study was started in 1942 without the benefit of

a statistically sound design. The inspections were conducted over the

years by different inspectors and the ratings were made subjectively.

Therefore, little weight can be given to small differences in ratings

among the specimens; only major deviations from the performance of the

control should be considered.

2 . Materials

The primary variable in this study was the felt composition

(furnish) . Every other component of the finished roof was kept as uniform as possible.

2.1. Felts

The felt furnishes, other than the Asplund fibers, consisted of

rags and paper. The Asplund fibers were prepared by one of three processes, described in detail by Ritter T5]. Briefly, the wood was reduced to chips by passing logs through rapidly rotating blades,

passed over a magnetic separater to remove ferrous contaminants, preheated with steam at 140 to 170 psi^ for one and a quarter minutes and

forced between two grinding discs, one fixed and one rotating at high

speed, to produce wood fibers. The output was sent through screens to remove the incompletely separated fiber bundles. The fine wood fibers

are called Asplund fibers, after the developer of this process.

The heat-treated and chemically treated fibers were made by using

the Asplund defibrator in combination with a B-K reaction chamber. In

this combination, additional periods of heating can be employed to produce the heat-treated fibers or caustic soda (NaOH) can be added to

make the chemically treated fibers. The time-temperature-concentration

relationships vary with the types of wood used and are designed to

produce the types of fibers desired. The heat-treated fibers received

seven minutes of steam treatment prior to grinding and the chemically

treated fibers were soaked in a hot three percent caustic solution

followed by five minutes of steam prior to defibration.

The wood fibers in suspension were blended with paper, from a Hydropulper, and rags, from beaters, also in suspension , to produce the

13 different furnishes used. The characteristics of the felts produced

appear in Table 1. The fiber classification of the felts appears in

Table 2c

4

1 lbf = 4.45 newtons (approximately)

1 in. = 2.54 cm (exactly)
The felts described in Table 1 were all produced in 36-inch rolls

on the same commercial felt-making machine. Felt A-l contained no Asplund fibers and was used as the control. All of the felts containing

Asplund fibers were both less pliable and weaker than the control, and

they all had higher asphalt capacities. The Asplund felts were all

thicker than the control, partially accounting for their being stiffer,

but the stiffness of the Asplund felts was not quantitatively a function

of their thickness. Similarly, there was no quantitative relation between tensile strength (per inch of width) and thickness or composition.

2.2 Asphalts

The felts for the roll roofing and shingles were commercially

saturated with different saturants. The characteristics of these

saturants are reported in Table 3. The softening points of these

saturants are somewhat higher than those in current use.

The physical characteristics of the saturated felts with which the

roll roofing and shingles were made are tabulated in Table 4. All of

these products meet or exceed the minimum saturation and strength re- quirements of current ASTM and Federal specifications for roll roofing

and shingles.

Both the mineral-surfaced roll roofing and shingles were prepared

by coating the felts with a stabilized asphalt and surfacing them with

green ceramic granules. The properties of the coating asphalt and the

stabilizer content are reported in Table 5.

Because all of the specimens were made from the same coating on the same commercial machine, no further information was obtained on the coating. The weights of the roll roofing specimens, their total bitumen

contents (saturant and coating), their total ash contents and their

pliabilities are reported in Table 6. The weights, bitumen contents

and ash contents of the shingles are reported in Table 7. The figures

in these two tables are presented more to show the uniformity of the

specimens than to establish differences among them. The mineralsurfaced roll roofing specimens were all heavier than the minimum weight

required by ASTM (D 249) , but the shingles were lighter than required by

ASTM D 226-65. However, when these specimens were exposed, type 210

shingles were being manufactured instead of type 235, and these specimens

met the requirements for type 210 shingles.

ASTM D 249-60 and Fed. Spec. SS-R-630 Asphalt Roll Roofing Surfaced

with Mineral Granules; ASTM D 225-65 and Fed. Spec. SS-S-300 Asphalt

Shingles Surfaced with Mineral Granules.
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169 (76)

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Softening Point, R & B, °F (°C) 219 (104)

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Table 7. Asphalt Shingles

Weight Total Ash Total Bitumen

No. lb/100 ft 2 lb/100 ft

2 lb/100 ft 2

33.2 37.9

38.2 37.9

34.8 38.0

33.0 37.5

34.4 39.8

32.6 38.1

31.6 38.1

'35.2 40.8

33.2 42.8

32.5 40.3

35.8 40.0

A-l 80.7

B-l 86.3

B-2 82.8

C-l 79.7

C-2 84.2

D-l 81.6

E-l 80.0

F-l 86.8

F-2 86.7

G-l 83.4

G-2 85.8

11
3. Procedures

3.1. Specimen Preparation

The felts were made in a commercial felt mill, saturated in a com- mercial saturator and made into finished products on a commercial roofing machine. Conditions of operation, saturants, coatings and granules were kept as nearly uniform as possible in order to maintain the felt

furnish as the principle variable.

3.2. Exposure

The specimens were exposed on specially constructed roof decks,

made from 1 x 6-inch straight sided sheathing boards. The decks were installed on the roof of the Industrial Building at the old National

Bureau of Standards site facing due south at an inclination of 45°.

The specimens were applied directly to the decks, each specimen covering a 3 x 9-foot area. Each of the mineral-surfaced roll roofing

specimens was cut to contain two two-inch head laps, fastened with

roofing nails two-inches on centers.

The hexagonal shingles were also applied directly to the decks

without an underlayment in the manner prescribed for hexagonal shingles

3.3. Inspections

Periodically the exposure specimens were inspected visually by the

members of the Research Committee of the Asphalt Roofing Manufacturers

Association and representatives of the National Bureau of Standards.

No attempt was made to give absolute ratings to the specimens; only

relative performances were evaluated.

The letter designations for the inspectors were made to differentiate among them, only, and any particular designation, such as "A",

does not refer to the same person at different inspection periods.

Where the specimens have been rated numerically, the following ratings

prevail:

3 = Excellent

2 = Good

1 = Poor

Other inspectors on other occasions rated the specimens verbally without attempting to quantify the ratings.

12
4. Results

The members of the Research Committee and representatives of the

National Bureau of Standards inspected the Washington, D. C. exposures

in 1948, 1954, 1958 and 1965. Photographs were taken in October 1958

and April 1967.

The results of the 1948 inspection, after six and a half years of

exposure, were reported qualitatively. The shingles were performing

better than the mineral-surfaced roll roofing. A small amount of

blistering was becoming apparent on the roll roofing but weathering had

not progressed far enough to permit evaluation of deterioration re- sulting from differences in the composition of the felt [4].

In May of 1954 the exposures, then over twelve years old, were

inspected again. The shingles were still in excellent condition but some deterioration had become apparent in the mineral-surfaced roll

roofing. One of the eight inspectors had reported that B-2 and E-2 were not performing satisfactorily and B-l and G-2 were "less than good".

The other seven inspectors rated all of the specimens "good". Thus,

twelve years was the earliest period in which differences in deterioration appeared and these differences were considered significant by only

one observer. There was no consistent pattern of deterioration relating

to felt composition in these twelve year observations. The nature of

the defects was not reported.

The next comprehensive inspection was made in 1958. Like the other

inspections, this one was made by the members of the Research Committee

and a representative of the National Bureau of Standards. The ratings were based on the appearances of the specimens relative to how each inspector thought they should be after 16 years of exposure. Because of

the subjective nature of this type of inspection, the performances of

the specimens relative to the control (A-l) becomes the primary con- sideration. Sufficient differences in deterioration among the specimens

existed in 1958 to warrant duplication of the inspection summaries in

Table 8.

It is interesting that the inspector who had rated roll roofings

E-2 "fair" and B-l and G-2 "less than satisfactory" in 1954 rated them

excellent in 1958. This change in rating illustrates that it is ex- tremely difficult to project long-term performance from early observations .

After 16 years of exposure, only one composition of felt (B-2) had

produced a mineral-surfaced roll roofing product that had performed less

satisfactorily than the control. B-2 had been among the poorer performers in 1954, also. It contained the higher concentration (30%) of

unmodified pine Asplund fibers. On the other hand, the chemically

treated pine and the unmodified oak fibers produced products that were outperforming the control.

13
The shingles were all still performing extremely well and all but

four were rated excellent by all of the inspectors. One inspector rated

C-2, E-l, F-2 and G-l good. E-l (30% heat treated oak) and G-l (30%

chemically treated oak) were also among those performing less than ex- cellently among the roll roofing.

A 23-year inspection of these materials was made in 1965 by five

members of the Research Committee. This was the only inspection in

which blistering and cracking were observed as well as general appearance. The results are presented in Table 9.

All of the mineral-surfaced roll roofing showed some signs of deterioration, but all were still performing satisfactorily; none was considered a failure. Nine of the twelve Asplund felts were outperforming the control. Only three were less satisfactory: B-l and B-2, con- taining 15% and 30% untreated pine, and E-2, containing 50% heat-treated

oak. These three also contained appreciable quantities of rags. Both

B-l and B-2, because of their high rag contents, had low asphalt

capacities, but E-2 had a high capacity. The efficiency of saturation

of all three exceeded the 90 percent level. Specimens with low saturation efficiencies (F-2, G-l) were outperforming the control,, Thus,

performance does not seem to be related to felt furnish or efficiency of

saturation in the ranges of these variables covered in this study.

In general, all of the shingle specimens were performing excellently after 23 years of exposure. Only one shingle specimen (C-2) was performing appreciably worse than the control. This one contained 37

percent rags, 33 percent paper and 30 percent untreated oak. The same

felt produced mineral-surfaced roll roofing that was outperforming the

control. Therefore, again it is not possible to blame its poor performance on the felt furnish.

No group inspection was made after 25 years of exposure, but photographs were taken of all of the specimens. Examination of the photographs

revealed that little change had occurred in any of the specimens since

the 1965 inspection (23 years 1 exposure). Even the specimens rated

"poor" in 1965 were still performing adequately. Photographs of the

three roll roofing specimens and one shingle specimen that showed the

worst deterioration are reproduced in Figures 1 to 4. Figure 5 is of

the control.

5. Conclusions

One important conclusion can be drawn from this comprehensive ex- posure program o All of the specimens have given a more-than-satisfactory

performance during their 25 years of exposure. Small differences in

deterioration were observed after 16 years of exposure, but none was related to felt furnish. Durable shingles and mineral-surfaced roofing

can be made from organic felts irrespective of the type or quantity of

Asplund fibers in the ranges covered in this study.

14
Table 8

Asplund Felt Specimens After 16 Years

of Exposure in Washington, D. C.

1958

Mineral-Surfaced Roll Roofing

Specimen Inspector Average

No. A B C D E F G H

A-l 3 3 3 2 3 3 3 3 2.9

B-l 3 3 3 2 3 3 3 3 2.9

B-2 2 3 2 2 3 3 2 3 2.5

C-l 3 3 3 3 3 3 3 3 3.0

C-2 3 3 3 3 3 3 3 3 3.0

D-l 3 3 3 2 3 3 3 3 2.9

D-2 3 3 3 2 3 3 3 3 2.9

E-l 3 3 3 2 3 3 3 3 2.9

E-2 3 3 3 2 3 3 3 3 2.9

F-l 3 3 3 3 3 3 3 3 3.0

F-2 3 3 3 3 3 3 3 3 3.0

G-l 3 3 3 2 3 3 3 3 2.9

G-2 3 3 3 2 3 3 3 3 2.9

Table 8 continued on next page

15
Table 8 - continued

Shingle s

Specimen

No. A B C

Insp

D

ector

E F G H

Average

A-l 3 3 3 3 3 3 3 3 3.0

B-l 3 3 3 3 3 3 3 3 3.0

B-2 3 3 3 3 3 3 3 3 3.0

C-l 3 3 3 3 3 3 3 3 3.0

C-2 3 3 3 2 3 3 3 3 2.9

D-l 3 3 3 3 3 3 3 3 3.0

E-l 3 3 3 2 3 3 3 3 2.9

F-l 3 3 3 3 3 3 3 3 3.0

F-2 3 3 3 2 3 3 3 3 2.9

G-l 3 3 3 2 3 3 3 3 2.9

G-2 3 3 3 3 3 3 3 3 3.0

3 = Excellent

2 = Good

1 = Poor

16
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18
6. Literature Cited

f 1] Shaw, Mo B., G. W. Bicking and 0. G. Strieter, Experimental

Production of Roofing Felts, RP No. 67, Jo Res. NBS 2,

1001-1016, 1929.

\2] Strieter, 0. G., A Study of the Weathering Quality of Roofing

Felts Made from Various Fibers, RP No. 888, J. Res. NBS _16,

511-523, 1936.

\ 3] Abrahams, Ho A., Asphalts and Allied Substances, Fifth Ed.,

D. Van Nostrand, 1, 728, 1945.

T4] NBS Report, unnumbered, Investigation of Roofing Felts

Containing Asplund Fibers, Sept. 1, 1948 (Restricted).

[5] Ritter, G. A., Paper Mill News 67, No. 47, Nov, 18, 1944.

This work was sponsored by the Asphalt Roofing Manufacturers

Association at the National Bureau of Standards. The preparation and

exposure were supervised by Dr. 0. G. Strieter o Inspections were conducted by members of the Research Committee of the Asphalt Roofing

Manufacturers Association and Dr. H. R. Snoke, of the National Bureau

of Standards.

7, Glossary

Asplund fibers - Wood fibers prepared by a process developed by

Ao Asplund.

Caliper - The thickness of a material as measured with calipers

Furnish - The composition of felt in terms of fibers, i.e.,

rag, wood, paper

Shingles types - The designation used to describe shingles in terms of

the shapes of their tabs and the approximate weight

of one square of material

»

Shives - Bundles of wood fibers that have not been dispersed.

Square - Quantity of roofing material covering 100 square

feet of roof area„

19
.

>,i

FIGURE 1 - Mineral^ Surfaced Roll Roofing B-l with Felt Composed of

55% Rags, 30% Paper and 15% Pine Fibers. Rated 1.3 out

of 3.0 after 23 Years of Exposure.

20
B2

p " j&&

FIGURE 2 - Mineral-Surfaced Roll Roofing B-2 with Felt Composed of

377o Rags, 33% Paper and 307o Pine Fibers. Rated 1.1 out

of 3.0 after 23 Years of Exposure.

21
-'*r«?

' 2 PIs*

"'

v^w?7r5rr, ?TT^

i i

S6

FIGURE 3 - Mineral-Surfaced Roll Roofing E-2 with Felt Composed of 20%

Rags, 307c Paper and 50% Heat Treated Oak Fibers. Rated 1.4

out of 3.0 after 23 Years of Exposure.

22
r*5« »a '»

MnWMl^MMMMHM '

/ :. . v_\..- * *.wA"<cf>, ti>*. *t.i*J #.,

FIGURE 4 - 307 no«k%-K

2 With

D Fel,

fc Composed of 37% Rags, 337. Paper and 30/o Oak Fibers. Rated 2.1 out of 3.0 after 23 Years of Exposure.

23
FIGURE 5 - tiineral-Surfaced Roll Roofing A-l Used as Control, with

Felt Composed of 73% Rags and 27% Paper. Rated 1.9 out

of 3.0 after 23 Years of Exposure.

24
•MUMMHJMr

•|""""

| ——»—»"—mumir ii "mmw.i a<f

/

I

J

smmmmmmmmmwmmmmmmmm /

/

y•

r***-r»°~mmtmtmm

»'-•.. Hi -

FIGURE 5 - (Continued) Mineral-Surfaced Shingles A-l Used as Control

with Felt Composed of 73% Rags and 27% Paper. Rated 2.7

out of 3.0 after 23 Years of Exposure.

* U.S. GOVERNMENT PRINTING OFFICE : 1 969— 3^(1 -025/1 32 25

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