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NATL INST OF STANDARDS & TECH R.I.C.

A1 11 00993083

Rosslter, Walter J., /The viscosities of TA435 .U58 V92;1976 C.I NBS-PUB-C 1976 NBS BUILDING SCIENCE SERIES 92

U.S. DEPARTMENT OF COMMERCE / National Bureau of Standards

The Viscosities ^

of Roofing Asphalts I

at Application Temperatures 9

1
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National i;.,.

DEC 3 0

The Viscosities of Roofing Asphalts

at Application Temperatures

C • Walter J. Rossiter, Jr.,

and Robert G. Mathey

Center for Building Technology

Institute for Applied Technology

National Bureau of Standards

Washington, D.C. 20234 ^

Prepared for

Naval Facilities Engineering Command

Department of the Navy

Washington, D.C. 20390

Directorate of Civil Engineering U.S. Air Force Washington, D.C. 20330

Office of Chief of Engineers U.S. Army

Washington, D.C. 20314

and

National Bureau of Standards Washington, D.C. 20234

U.S. DEPARTMENT OF COMMERCE, Elliot L. Richardson, Secretary

Edward 0. Vetter, Under Secretary

Dr. Betsy Ancker-Johnson, Assistant Secretary for Science and Technology

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Acting Director

Issued December 1976
National Bureau of Standards Building Science Series 92

Nat. Bur. Stand. (U.S.), Bldg.Sd.Ser.92,23 pages (Dec. 1976) CODEN: BSSNBV

U.S. GOVERNMENT PRINTING OFFICE

WASHINGTON: 1976

For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402

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Contents

P«ge

1. Introduction 1 1.1 Objective 1 1.2 Function of Asphalt in Built-Up Roofing Membranes 1 1.3 Application Specification 2

1.4 Viscosity of Roofing Asphalts 2

2. Experimental Program 2

2.1 Measurement of Asphalt Viscosity 2

2.1.1 Asphalt Samples 2

2.1.2 Test Method 2

2.2 Interply Asphalt Thickness of Built-Up Roofing Membrane Specimens 3

2.2.1 Construction of the Specimens 3

2.2.2 Sampling of the Membrane Specimens 6

2.2.3 Measurement of the Interply Asphalt Thickness 7

3. Results 7

3.1 Measurement of Asphalt Viscosity 7

3.2 Measurement of Interply Asphalt Thickness 8

4. Discussion of Results 10

4.1 Viscosity of Roofing Asphalts at the Application Temperature 10

4.2 Interply Asphalt Thickness as Related to the Application Temperature 11

4.3 Interply Asphalt Thickness as Related to the Viscosity at Application 11

5. Viscosity Criterion for the Application of Roofing Asphalt 12

6. Recommendations 14

7. References 15

8. Appendix—Relationship Between Interply Asphalt Thickness and Viscosity

Examined in More Detail 15

iii

The Viscosities of Roofing Asphalts at Application Temperatures

Walter J. Rossiter, Jr. and Robert G. Mathey

The optimum range of kinematic viscosity over which hot asphalt should be applied in the

fabrication of built-up roofing membranes was determined to be 50 to 150 centistokes (mmVs)-

This viscosity range was based on the relationship between interpjy thickness and application

temperature of asphalt obtained from roofing membrane specimens fabricated in the field. Because

laboratory measurements showed a wide range of viscosities for roofing asphalts of the same type over their application temperature ranges, it was recommended that asphalts be applied at temperatures based on viscosity and not empirically determined temperature limits. In practice, the

viscosity-temperature relationship should be determined for each roofing asphalt for the application

temperature range prior to use. Using this relationship and the optimum viscosity range, the temperature range for applying each asphalt can be determined. Key words: Application temperature; asphalt; built-up roofing; interply thickness; roofing membranes; viscosity.

1. Introduction

More than 95 percent of built-up roofing membranes

are constructed using asphalt as the between-ply bitu- men and flood coat The built-up membranes are generally constructed by applying hot asphalt in consecutive, solid layers to adhere roofing felts to each

other in shingle fashion. The temperature range over which the hot asphalt is applied has been traditionally

determined empirically. Asphalt at temperatures within

this range, considering ambient temperature and wind

conditions, is expected to be fluid and readily applied. In addition to an application temperature range of

asphalt, a maximum temperature to which the asphalt

may be heated is specified. This maximum specified

temperature is intended to prevent flashing of the asphalt and deleterious changes in the asphalt's physical and chemical properties. Unfortunately, the minimum and maximum temperature requirements pertaining to the application of asphalt are not based on

scientific or technical evidence. The fundamental property of asphalt on which the application temperature

should be based is viscosity. Viscosity is the property

of the asphalt which governs its flow.

1.1. Objective

The objective of the research was to develop a viscosity criterion for the application of asphalt in the fabrication of built-up roofing membranes. The re- search project was divided into two phases. In the first phase, viscosity-temperature relationships were deter- mined for Type I and Type III asphalts, ASTM Designation D312-71 [2], for the normal temperature range

of application. The asphalts represented a variety of sources and blends commonly used by the roofing

industry in the United States. In the second phase,

3-ply built-up roofing membrane specimens were preFigures in brackets indicate references listed in section 7.

pared in the field with asphalts at temperatures that ranged from 325 to 500°F (163 to 260°C). The thick- nesses of the between-ply asphalt were measured and

related to the application temperatures and to the vis- cosities of the asphalts at those temperatures. Based on

the results of the viscosity-temperature relationships

and the between-ply thicknesses of the asphalts, a vis- cosity criterion for applying hot asphalt was recom- mended.

1.2. Function of Asphalt in Built-Up

Roofing Membranes

The function of the asphalt in the asphalt-felt built- up roofing membrane is twofold [3]. The asphalt is an

adhesive for bonding the felts and provides a water- proofing layer between the felts. Applying the asphalt

at a temperature within an empirically determined

temperature range does not assure that the hot asphalt

will flow properly to provide adequate adhesion and

waterproofing. Therefore, to attain these essential properties, the viscosity of the roofing asphalt during application should be specified.

Proper flow of the asphalt is a necessity during the membrane fabrication process. If the asphalt is too

viscous, it will not flow readily enough to penetrate the

felts, and may be too thick, uneven and possibly cause

interply voids. Poor penetration into the felts, and a thick or uneven application can result in poor adhesion

between plies. Excessive thickness of between-ply

asphalt under certain conditions may contribute to roofing failure by membrane slippage [4] or excessive thermal movement. In addition, too thick an application of the asphalt is a waste of a petroleum based

material. Voids which may trap water are potential sources of blisters.

If the asphalt is too fluid during application, it will flow too readily resulting in a layer of asphalt which

may be too thin. An application which is too thin may

result in poor adhesion, voids and inadequate water- proofing between felts.

1
1.3, Application Specification

Roofing asphalts are classified in ASTM Standard

D312-71 into four types, I, II, III, and IV, by empirical tests such as softening point, ductility and pentration [2]. These tests are not a measure of the flow of roofing asphalt at application temperatures. They may

give a relative indication of this property for the vari- ous types. A Type I asphalt has a lower softening point

and may have a higher penetration than a Type III asphalt. At a given application temperature it would be

expected that a Type I asphalt would in general flow more readily than a Type III asphalt. Current specifications for applying hot asphalt do

not consider differences in flow properties for different asphalts. For example, the National Roofing Contractors Association (NRCA) lists in their manual [5] the same range of application temperatures for all four

types of asphalts. They recommend a minimum application temperature of 350 °F (177°C) and a maximum heating temperature of 475 °F (246° C).

Likewise, in the Tri-Service manual, "Maintenance

and Repair of Roofs," it is stated that "asphalt should

not be heated above 450 °F (232°C) and should

normally be not lower than 350 °F (177°C) when

poured or mopped on a roof [6]." This statement

ignores differences in flow of the four types of asphalts

at a given temperature. Some recognition of the flow phenomenon is made as this Tri-Service manual further

states that "if asphalt with a softening point of 150 °F

(66°C) or lower is used, the maximum kettle temperature is 375 °F (191°C) and the minimum temperature

for application is 300 °F (149°C)."

Manufacturers of bituminous roofing felts recom- mend in general a minimum application temperature

and a maximum heating temperature for roofing as- phalts. Some of the manufacturers recommend lower

minimum and maximum temperatures for Type I than

for Type III asphalts. The latter recommendation

acknowledges differences in flow properties between

the two types.

1.4. Viscosity of Roofing Asphalts

One session of the Fourth National Conference on

Roofing Technology, sponsored by the National Bureau

of Standards (NBS) and the National Roofing Contractors Association (NRCA) in 1975, discussed vis- cosity grading of roofing asphalt. Cullen briefly re- ported the conclusion of that session [3]. It was stated

that the hot asphalt should be applied with a viscosity of approximately 150 centistokes (mmVs) . In addition, Mertz has stated that the optimum application viscosity

is 100-150 centistokes (mmVs) under good weather

conditions which he defined as 60 °F (16°C) and

above [7].

Viscosity grading of asphalt is not a new concept.

Viscosity specifications have been used for a number

of years for paving asphalts. This subject is reviewed

in ASTM STP 532, "Viscosity Testing of Asphalt and

Experience with Viscosity Graded Specification [8]."

A viscosity grading criterion for the application of asphalt in the fabrication of a built-up roofing membrane would help to assure proper application of the hot

asphalt. The asphalt would be applied at a temperature

to achieve adequate bonding of the felts and a continu- ous waterproofing layer of asphalt between the felts. Membrane failures caused by inadequate interply ad- hesion would be reduced. Roofing performance would

be enhanced and asphalt would be conserved due to a reduction in excessively thick applications.

2. Experimental Program

The experimental program consisted of two phases.

The first phase was concerned with the measurement

of the viscosities of a wide variety of typical roofing

asphalts from many sources throughout the world. These, measurements were intended to provide information on the range of viscosity-temperature relationships

which may be expected for roofing asphalts from dif- ferent sources and blends. In the second phase of the experimental program,

the between-ply thicknesses of asphalts in roofing membranes were related to the viscosities of the asphalts at the time of application. Viscosity-temperature relation- ships were also determined for the two types of as- phalts. Types I and III, used in the fabrication of built- up roofing membrane specimens.

2.1. Measurement of Asphalt Viscosity

2.1.1. Asphalt Samples

The National Roofing Contractors Association se- lected the twenty asphalt samples used in the study to determine the range of viscosity-temperature relation- ships of roofing asphalts. The twenty asphalt samples,

ten each of ASTM D312-71 Type I and Type III [2], were made available to the National Bureau of Standards by the Trumbull Asphalt Company. These asphalt

samples, from various sources throughout the world, were typical of the broad range of asphalts currently

used in roofing in the United States. Four of the samples were blends of asphalts from two sources. Table 1

lists the asphalts along with their sources, softening

points, penetration and experimentally determined

kinematic viscosities. The properties of the asphalts used to prepare the

built-up roofing membrane specimens are given in table 2. The properties of the asphalts, softening point,

penetration and kinematic viscosity, were determined

for the two types of asphalt from samples collected both before and after fabrication of the membrane

specimens.

2.1.2. Test Method

Measurements of the viscosities of the asphalt samples were performed according to the procedure de- scribed in ASTM D2170-74, "Standard Method of Test

for Kinematic Viscosity of Asphalts (Bitumens) [9]."

The test method consists of measuring the time re- quired for the asphalt to flow through a constant vol2
Table 1. Sources and properties of asphalt samples

Desig- nation Source Refinery Type

ASTM-—D 312 Designation Viscosity'" '', Centistokes (mmVs)

Softening Point" Penetration" X 10"' mm

330 °F

(166°C)

380 °F

(193°C) 430 °F

"F "C (221°C)

1 Venezuela Jacksonville I 140 60 38 275 98 48

2 California Portland I 140 60 34 124 48 24

3 Wyoming C) I 146 63 31 238 87 39 4 Kuwait- Morehead City I 145 63 28 248 88 41 Venezuelan Blend

5 Kansas Hazelwood I 144 62 27 197 74 36

6 Persian Gulf Waltham I 144 62 37 254 92 44

7 Oklahoma Irving I 141 61 33 203 77 (') 8 West Texas Houston I 140 60 32 154 60 30

9 Gulf Coast Detroit I 144 62 28 220 81 43

10 California Compton I 142 61 24 189 69 32

11 California Portland III 199 93 16 1272 313 118 (50%) Persian Gulf (50%)

12 Texas Coast Jacksonville III 202 94 28 830 208 76

13 Wyoming C) III 204 95 30 456 104 41

14 Kuwait- Morehead City III 191 88 17 1243 333 141 Venezuelan Blend

15 West Texas Houston III 202 94 20 811 213 82

16 Kansas Hazelwood III 199 93 22 1369 318 118

17 V an f> 1 Q W dlLllalll III 197 91 23 1175 311 191 (50%) Persian Gulf (50%)

18 Oklahoma Irving III 201 94 24 1383 322 124

19 Gulf Coast Detroit III 198 92 20 650 170 66 20 Persian Gulf Compton III 200 93 18 1154 291 92

• Values of softening point and penetration were furnished by the Trumbull Asphalt Company.

*" Viscosity determined as described in ASTM Standard D2170-74.

' The viscosities are the averages of three measurements. The relative standard deviation for each average value was 3 percent or

less except for four values. The relative standard deviations for sample 4 at 330 °F (166°C), sample 16 at 330 "F (166°C), sample

9 at 330 °F (166°C) and sample 9 at 430 °F (22rC) were 4, 5, 7 and 8 percent, respectively.

^ The refinery of this asphalt was not provided to NBS.

" Viscosity determination not valid at this temperature because asphalt liberated a gas which was trapped in the capillary tube of the viscometer.

ume in a calibrated capillary viscometer under

a constant pressure and at a constant temperature. The calibrated viscometer has a viscosity constant, in units of centistokes per second (mm-/s'), ob- tained by measuring the flow time of a standard liquid of known viscosity. The viscosity of the asphalt, in centistokes (mmVs), is determined by multiplying its flow time, in seconds, by the calibration constant of the viscometer.

Zeitfuchs cross-arm viscometers, shown in figure 1, were the type of capillary viscometers used in this study. Five sizes of these viscometers (sizes 4 through

8) having different inside capillary tube diameters were used to measure viscosity depending on the rate of flow of the asphalt [9]. The time for the asphalt to flow through a constant volume in the viscometers

ranged from about 60 to 180 seconds. The values of

viscosity of the asphalts listed in tables 1 and 2 are

the average of three measurements. Each of the three measurements for a particular asphalt at a given temperature was made using a different viscometer of the same size.

A silicone oil bath was the constant temperature

medium for the viscosity measurements. The bath was

capable of maintaining the temperature within ±0.1 °F

(±0.05°C) of the selected test temperature.

Cleaning the viscometers presented some difficulty

and was time consuming. In general, the viscometers were removed from the oil bath, rinsed until clean with

a solvent such as tetrachloroethylene and dried in an oven at 350 °F (177°C). The capillary tubing of the viscometer must be clean prior to test in order to obtain valid results.

2.2. Interply Asphalt Thickness of Built-Up

Roofing Membrane Specimens

2.2.1. Fabrication of Membrane Specimens

The preparation of the membrane specimens under

field conditions was performed in Kansas City, Missouri, with the cooperation of the Roofers Local #20

Joint Apprenticeship Program. National Bureau of Standards personnel planned and supervised the field

3
Table 2. Properties of asphalts used to prepare built-up roofing membrane specimens

Physical Properties'" Viscosity " Centistokes (mm'' /s)

Asphalt" Softeninj ; Point" Penetration' 325 °F 350 °F 375 °F 400 °F 425 °Y 450 °F

°F °C X 10"' mm (163°C) (177°C) (191°C) (207°C) (219°C) (232°C)

ASTM Type I—sample

collected before 143 61 41 226 134 83 56 37 28

mopping specimens

ASTM Type I—sample

collected after 141 60 42 207 123 77 52 36 26

mopping specimens

ASTM Type III—sample

collected before 190 88 28 849 403 215 130 80 56

mopping specimens

ASTM Type III—sample

collected after 189 87 28 802 386 206 124 78 53

mopping specimens

Asphalt type described in ASTM D312-71.

* Physical properties determined by the National Bureau of Standards.

' Viscosity determined as described in ASTM Standard D2170-74.

" The viscosities are the averages of three measurements. The relative standard deviation for each average value was 3 percent or

less.

" Softening point determined as described in ASTM Standard D2398-71.

' Penetration determined as described in ASTM Standard D5-73.

Figure 1. Zeitjuchs cross-arm viscometers, sizes 4, 6 and 8.

4
study. The Joint Apprenticeship Program obtained the materials and equipment needed to prepare the membrane specimens, and provided the use of their facili- ties for membrane fabrication at the Kansas City Technical Education Center. Apprentice roofers performed

the mopping under the direction of journeymen roofers. The membranes were fabricated inside the building

where the temperature was about 60 °F (16°C). The

bottom plies of the membrane specimens were not bonded to the substrate over which membrane preparation took place.

Six types of 3-ply membrane specimens measuring

3 X 9 ft (0.9 X 2.7 m) were prepared from organic,

asbestos and glass roofing felts, and ASTM Type I and Type III asphalts, respectively. The materials used

in the preparation of the membrane specimens are

listed in table 3. Membrane specimens were fabricated

using each type of roofing felt and each type of asphalt

which was applied at temperatures that ran<red from

325 to 500 °F (163 to 260°C) in approximately 25 °F

(14°C) temperature increments. In general two membrane specimens were fabricated at each of these mopping temperatures. In some cases, there was a difference in the mopping temperatures of asphalt for two comparable specimens. Tables 4 and 5 list the temperatures of th^ asphalt at which each specimen was fabricated. A total of 95 membrane specimens

were prepared; 32 from organic felt, 32 from glass felt and 31 from asbestos felt.

Tahle 3. Materials used in jirc.jxirdlion oj the buill-up roofing

membrane specimens

Materials ASTM Specification

Asphalt—Type I D312-71

Asphalt—Type III D312-71

Asphalt saturated organic felt

Type 15 D226-75

Asphalt saturated asbestos felt

Type 15 D250-70

Asphalt-impregnated glass fiber mat

Type 15 D2178-69

The temperature of the asphalt in the mopping

bucket was recorded immediately prior to application

to the felts. A copper-constantan thermocouple and a

digital thermocouple indicator were used to measure

the temperature of the asphalt. The asphalt was trans- ferred from the heating kettle, which was located out- side of the building, to the mopping bucket at a temperature that was higher than the selected application

temperature. The asphalt was allowed to cool in the

Table 4. Asphalt application temperatures, average interply asphalt thickness and calculated asphalt viscosities for built-up roofing

membrane specimens fabricated with type I asphalt.

Type of felt in membrane

specimen

Number

of specimens

Application Temperature Interply Thickness"

Calculated asphalt viscosity centistokes (mm"/s) °F °C in mm

Organic 2 325 163 0.039 0.99 226

2 352 178 .030 .76 127

2 379 193 .023 .58 77

2 401 205 .022 .56 54

2 428 220 .022 .56 36

2 455 235 .015 .38 26

2 477 247 .022 .56 20

2 500 260 .018 .46 16

Asbestos 2 327 164 .041 1.04 217

2 354 179 .032 0.81 123

2 379 193 .036 .91 77

2 403 206 .031 .79 53

2 426 219 .023 .58 37

2 455 235 .024 .58 26

2 477 247 .024 .61 20

2 505 263 .021 .53 15

Glass 2 325 163 .037 .94 226

2 351 177 .032 .81 132

2 378 192 .022 .56 80

2 403 206 .019 .48 53

2 428 220 .020 .51 36

2 446 230 .018 .46 29

2 477 247 .021 .53 20

2 502 261 .019 .48 15

° The value of interply thickness for each membrane specimen represents the average of 24 measurements. The mean relative standard deviation of the average interply thickness determinations in tables 4 and 5 was 31 percent. Eighty percent of the

relative standard deviations fell within the range of 15 to 45 percent. The minimum and maximum relative standard deviations were 9 and 61 percent, respectively.

5
Table 5. Asphalt application temperatures, average interply asphalt thicknesses and calculated asphalt viscosities for built-up roofing

membrane specimens fabricated with type III asphalt

Type of felt in membrane

specimen

Number

of specimens

Application Temperature Interply Thickness*

Calculated asphalt viscosity centistokes ( mm"/s

)

op °C in mm

Organic 2 323 162 Ci AI^7 U.Ud/ 2 343 173 .058 1.47 503

2 374 190 .043 1.09 233

2 392 200 .VOL i.oU 100

2 424 218 .054 L.Oi Q*> oL

2 482 250 AOA U. /O oo

2 484 251 .027 Sri oooL

2 500 260 AT A A Q OA

Asbestos 2 329 165 Mod /OO 2 343 173 A/CO .Uoz oUo

1 3/0 AC^

1 379 193 AA/1 .1)04 l.OO ZUO

1 399 204 .051 1.30 134

1 403 206 .047 1.19 125

1 426 219 1.1 ( 1 455 235 AOO A Ql U.ol /1Q

1 457 236 .048 1 OO 4o

2 482 250 AC 1 1 QA OO

2 489 254 .020 A CI 0.51 oU

Glass 1 322 161 f\A A 1 0/1 fl3A yoo

1 331 166 .1)01 1 3n 2 342 172 ACT 1 QA ozy

1 378 192 A/1 C 1.11 ZXO

1 385 196 A/I O 1 Afl 1.09 loo

1 392 200 .041 1.04 156

1 397 203 .050 1.27 139

1 426 219 .044 1.12 80

1 428 220 .036 0.91 77

2 466 241 .027 0.69 42

2 471 244 .034 .84 38 2 500 260 021 .53 26

The value of interply thickness for each membrane specimen represents the average of 24 measurements. The mean relative standard deviation of the average interply thickness determinations in tables 4 and 5 was 31 percent. Eighty percent of the

relative standard deviations fell within the range of 15 to 45 percent. The minimum and maximum relative standard deviations were 9 and 61 percent, respectively.

mopping bucket until the desired application temperature was reached. The temperature of the asphalt was

recorded only before mopping the bottom felts. In the preparation of the membrane specimens, the bottom felts were mopped with hot asphalt and the second plies of felt were immediately laid in the hot

asphalt. The top plies were laid in the same manner

after mopping the second plies of felt. Two comparable

membrane specimens were mopped at the same time. The membrane specimens were prepared in "sandwich"

fashion by laying one 3 x 9 ft (0.9 x 2.7 m) piece of felt directly over another. This type of membrane fabrication differed from the usual field method of "shingle"

application of roofing felts. The felts were laid with

care and smoothed out by hand. Brooming of felts was not carried out because this procedure might have

affected the flow of the hot asphalt and influenced the between-ply thickness of the asphalt. The experiment was designed to measure the between-ply bitumen

thickness as a function of asphalt flow and not of pressure applied to the felts.

One gallon (3.8 dm^) samples of the Type I and

Type III asphalts were collected both before and after membrane fabrication. These samples were sent to the National Bureau of Standards laboratories for the pur- pose of measuring their viscosities over the range of application temperatures.

2.2.2. Sampling of the Membrane Specimens

The 3 X 9 ft (0.9 x 2.7 m) membrane specimens were

too large for shipment to the National Bureau of Standards laboratories and for measurements of the

interply asphalt thickness. Therefore, six 6 x 12 in ( 152

X 305 mm ) coupon samples were randomly sampled

from each of the large membrane specimens. The ran- dom sampling procedure was determined by the National Bureau of Standards' Statistical Engineering

Laboratory.

Each membrane specimen was divided into six equal 11/2 x 3 ft (0.5 x 0.9 m) sections. Each section was divided further into nine equal 6 x 12 in (152 x

6
305 mm) subsections. One subsection coupon from

each section of each membrane was randomly cut, thus providing the six coupon samples from each membrane

specimen. Figure 2 shows a typical random sampling

pattern for the selection of six coupon samples from a membrane specimen. A total of .570 coupon samples was sent to the National Bureau of Standards laboratories for determination of the interply asphalt thickness.

-9ft -

-(2,7 m)-

FiGURE 2. Typical random sampling pattern for the selection of

six coupon samples from a membrane specimen.

2.2.3. Measurement of the Interply Asphalt Thickness

The interply thicknesses of the asphalt in the field mopped specimens were determined with the use of a 20-povver machinist's microscope. A 1/2 x 12 in (13 x 305 mm) strip was cut from each of the coupon samples. Each strip was placed on edge under the lens of

the microscope and the interply bitumen thickness was

measured in units of 0.001 in (0.025 mm). Four thick- ness measurements were made for each strip, two for each between-ply mopping. The measurements were made at distances of approximately 4 and 8 inches (102

and 203 mm) from one end along the edge of the

strip. Figure 3 shows a membrane strip mounted under

the lens of the microscope.

The microscope base on which the membrane strip was mounted was movable and the movement could be

read directly in 0.001 in (0.025 mm) using a micrometer. A cross-hair in the eye piece of the microscope was aligned on one asphalt/felt interface. The microscope base supporting the sample was then moved until the cross-hair passed over the interply asphalt and was

aligned on the opposite asphalt/felt interface. The

interply thicknesses of the asphalt were determined

from the differences in the micrometer readings.

A total of 24 measurements were made to determine

the interply thicknesses of asphalt in each membrane

specimen, since there were six coupon samples cut from

each membrane specimen.

3. Results

3,1. Measurement of Asphalt Viscosity

The viscosities of the 10 Type I and 10 Type III asphalts were determined at 330, 380 and 430 °F (166,

193 and 221 °C) to determine the range of viscosityFicuRE 3. Measurement of interply asphalt thickness using a

machinist's microscope.

temperature relationships of typical roofing asphalts.

The viscosities are given in table 1 and the ranges in which they fell are illustrated graphically in figure 4. The viscosity data may also be illustrated according

to ASTM D341-74 which is a method for plotting the log log viscosity versus the log absolute temperature

[10]. Such plots for the most viscous and least viscous

asphalts given in table 1 approximated straight lines as shown in figure 5. It is noted that for asphalt designated as number 7 in table 1, the viscosity determination at 430 °F (221 °C) was not vaHd because the asphalt liberated a gas, observed as bubbles entrapped

in the capillary tubing of the viscometer. These en- trapped bubbles caused an erratic, nonreproducible

flow of asphalt.

An attempt was made to measure the viscosity of

the asphalts at 480 °F (249°C), but the test method

was not suitable with these asphalt samples at this high

temperature because of the gas bubbles which formed

within the capillary tubes of the viscometers. At temperatures in the range of 325 to 450 °F (163 to 232°C), the test method was in general readily applied

to the measurement of the viscosities of these roofing

asphalts.

7
TEMPERATURE, °C

190

380 TEMPERATURE, "F

Figure 4. Ranges of the viscosity-temperature relationships jar the Type I and Type III asphalts obtained from various sources throughout the world.

170 180

TEMPERATURE, "C

190 200 220 230

1500

1000

40

1

18

1 1 1

1 1 1 1

Type 1 o

Tvpe III «

13

1

N. i

2

Data correspond to asphalt sample designations 1,2, 13

1

and 18 given in Table 1,

1 1 1

1 1 1 320 340 360 380 400 TEMPERATURE, °F

440

Figure 5. Plots of the log log viscosity versus the log absolute temperature for the most viscous and least viscous Type I and Type III asphalts given in table 1.

The viscosities of the Type I and Type III asphalts

used to prepare the roofing membrane specimens in the

field were measured at 25 °F (14°C) increments over

a range from 325 to 450 °F ( 163 to 232°C ) . The vis- cosities were determined for asphalt samples which

were collected from the heating kettles both before and

after mopping. The viscosities of these asphalts corre- sponding to the temperatures noted above are given in table 2 and illustrated graphically in figure 6. Figure 7 shows that plots of the log log viscosity versus the log absolute temperature for the asphalt samples collected before mopping approximated straight lines. The values of the viscosities of the asphalts corre- sponding to the temperatures listed in tables 1 and 2

are the average of three measurements. The relative standard deviation for each average value of viscosity

given in tables 1 and 2 was 3 percent or less except

for four values given in table 1. The relative standard

deviations for sample 4 at 330 °F (166°C), sample 16

at 330 °F (166°C), sample 9 at 330 °F (166°C)

and sample 9 to 430 °F (221 °C) were 4, 5, 7 and 8

percent, respectively.

The results indicated a wide range of asphalt viscosities at a given temperature. This range decreased with an increase in temperature. The Type III asphalts were

in general more viscous than the Type I asphalts at a given temperature. The viscosity-temperature relation- ships indicated that the Type III asphalts were in general more temperature susceptible than the Type I asphalts.

3.2. Measurement of Interply Asphalt

Thickness

The interply thicknesses of asphalt as a function of

the application temperatures are given in tables 4 and

5 and plotted in figure 8. The values of interply thick- ness for each membrane specimen represent the aver- age of 24 measurements. In cases where two comparable membrane specimens were mopped at the same

temperature, the interply thicknesses given in tables 4

and 5 represent the average values obtained from the two specimens.

The mean relative standard deviation of the average

interply thickness determinations given in tables 4 and

5 was 31 percent. Eighty percent of the relative stand- ard deviations for these determinations fell within the range of 15 to 45 percent. The minimum and maximum

relative standard deviations were 9 and 61 percent,

respectively.

8
TEMPERATURE. °C TEMPERATURE. X

TEMPERATURE. °F 320 340 360 380 400 420 440 TEMPERATURE, "f Figure 6. Viscosity-temperature relationships of the asphalts Figure 7. Plots of the log log viscosity versus the log absolute used in the preparation of roofing membrane specimens. temperature for the asphalt samples collected before mopping.

APPLICATION TEMPERATURE. °C

160 170 BO 190 200 210 220 230 240 250 260

310 320 330 340 350 360 370 3M 390 400 410 420 4 30 440 450 460 470 480 490 500 50

APPLICATION TEMPERATURE. °F

Figure 8. Interply asphalt thickness as a function of the application temperature.

9
The lines in figure 8 were obtained from linear regression analyses using the data from tables 4 and 5

for each type of membrane. From this figure it can

be seen that at a given temperature the interply asphalt

thickness was greater for the Type III asphalt than for the Type I. With an increase in application temperature, the interply thickness decreased. The type of felt appeared to affect the asphalt thickness. For either Type I or Type III asphalt, the interply thickness was

in general greater for the asbestos felts than for the organic and glass felts.

4. Discussion of Results

4.1. Viscosity of Roofing Asphalts at the

Application Temperature

Two of the three temperatures at which the viscosities of the asphalts listed in table 1 were measured,

380 °F (193°C) and 430 °F (221°C), were within the range normally recommended for application [5, 6].

The third temperature, 330 °F (166°C), was purposely chosen to be slightly lower than the normally

recommended minimum application temperature of 350 °F (177°C).

It can be seen from the data in table 1 and figure 4

that there was a wide range in viscosities of both Type

I and Type III roofing asphalts for each of the three temperatures. For the Type I asphalts, the values of

viscosity ranged from 124 to 275 centistokes (mm-/s)

at 330 °F (166°C), 48 to 98 centistokes (mm-/s) at 380 °F (193°C) and 24 to 48 centistokes (mm-/s) at 430 °F (221 °C). For each temperature the highest value of viscosity was approximately twice the lowest

value. The difference between the highest value of viscosity

and the lowest value for each temperature was greater

for the Type III asphalts than for the Type I asphalts.

For the Type III asphalts the values of viscosity ranged

from 456 to 1383 centistokes (mmVs) at 330 °F

(166°C), 104 to 322 centistokes (mmVs) at 380 °F

(193°C) and 41 to 124 centistokes (mm-/s) at 430 °F

(221°C). The highest value of viscosity for the Type

III asphalt was approximately three times greater than

the lowest value for each of the three temperatures.

The wide range of viscosities of roofing asphalts at their application temperatures is significant and must

be considered in the fabrication of built-up roofing.

Empirical tests such as softening point and penetration now used for the classification of roofing asphalts are

essentially useless to indicate flow behavior in the range

of application temperatures. The softening points given

in table 1 fall into a narrow range for each type of

asphalt, in contrast to the wide range of viscosities. This can be seen from the plot of softening point versus

viscosity at 380 °F (193°C) in figure 9 which indicates

that there is no apparent relationship between these parameters. For the Type I asphalts, there appears to be no apparent relationship between penetration and

viscosity at 380 °F (193°C), as shown in figure 10. For the Type III asphalts there appears to be a rela- tionship between these parameters. However, statistical

SOFTENING POINT,

70 80

120 140 160 180 SOFTENING POINT.

200 220

Figure 9. Relationship between softening point and viscosity of asphalt at 380 °F (193°C).

PENETRATION AT 77 °F (25 °C), 0.1 mm

Figure 10. Relationship between penetration and viscosity at 380 °F (193°C) for typical roofing asphalts.

10
analysis of the limited data showed that penetration

could not be used as a reliable measure of viscosity. Because of the wide range of viscosities within a type and between types, asphalt should not be applied

at an empirically chosen temperature but at a temperature selected according to viscosity to achieve proper flow during application. The data indicate that asphalts within a type should not necessarily be applied

at the same temperature. The data further indicate that Type III asphalt should in general be applied at higher

temperatures than Type I asphalt. It is noted that for one of the Type III asphalts, number 13, the viscosities

at 380 °F (193°C) and 430 °F (221°C) were about

the same values as those for some of the Type I as- phalts, in spite of the fact that the softening point of asphalt number 13 was about 60 °F (33°C) higher

than those of the Type I asphalts.

Figure 4 shows, as expected, that the viscosity of the asphalt decreases with an increase in temperature.

The decrease in viscosity with an increase in temperature was less for the Type I asphalts than for the Type

III asphalts. The Type I asphalts included in this study were less susceptible to temperature change than the Type III asphalts. This may be important, particularly

if an asphalt is highly temperature susceptible, because

a slight decrease in application temperature may in- crease the viscosity above that recommended for proper

application.

The viscosities of the Type I and Type III asphalts

used to prepare the roofing membrane specimens fell within the ranges of the viscosities of the typical roof- ing asphalts obtained from various sources. Values of

viscosity, softening point and penetration for the as- phalt samples collected before and after mopping membrane specimens are given in table 2. There was a

slight decrease or fallback in the viscosity of both the Type I and Type III asphalts during the course of preparing the membrane specimens, as shown in figure

5. There was no significant change in the softening

point or penetration of Type III asphalt and only a 2 °F (1°C) decrease in the softening point of the Type

I asphalt. The viscosity fallback was not extensive but

it occurred during a 3 hour period. The slight fallback

in viscosity could be attributed to overheating of the asphalt which was necessary in this experiment. In order to obtain the temperature of 500 °F (260°C) in the mopping bucket as required by the experimental

program, the temperature of the asphalt in the kettle reached 575 °F (302°C).

4.2. Interply Asphalt Thickness as Related to the Application Temperature

In the fabrication of built-up roofing membranes,

adequate interply thickness of asphalt and adhesion

between piles of felt depend to a large extent on proper

application of the asphalt. Adequate interply thickness

requires that the asphalt has a certain viscosity during

application. Since a test method to measure asphalt

viscosity precisely in the field was not available, temperatures of the asphalt at the time of application were

related to subsequent laboratory determinations of

viscosity. Interply thicknesses were readily measured in the laboratory. It would have been desirable to measure

the interply adhesion of the membrane specimens in evaluating proper application of the asphalt; however, no established test method was available. The relationships between interply asphalt thickness and application temperature are shown in figure 8 for

the six types of membranes fabricated with organic,

asbestos and glass felts and Type I and Type III as- phalts. As expected, the interply thickness decreased

with an increase in application temperature. The inter- ply thicknesses for the 95 membrane specimens, tables 4

and 5, ranged in general from 0.02 to 0.06 inches (0.51

and 1.52 mm ) . The thicknesses of Type III asphalt were

greater than the thicknesses of Type I in membranes

containing all three felts over the application temperature range. For both Type I and Type III asphalts, the interply thicknesses were in general greater in the asbestos membranes than in the organic and glass membranes. The

interply thicknesses of Type III asphalt in the organic

membanes were greater than in the glass membranes,

whereas the interply thicknesses of Type I asphalt in membranes containing these felts were essentially the same. The authors have not investigated the reasons for

the apparent differences in asphalt thickness between

membranes fabricated with the three different felts and

the same type of asphalt. It was possible that the or- ganic and glass felts absorbed more asphalt during

application than the asbestos felts.

4.3. Interply Asphalt Thickness as Related to the Viscosity at Application

The important property of the asphalt that deter- mines the interply thickness is viscosity and not the temperature during application. The interply thicknesses

of the membrane specimens were related to the viscosities of the asphalts at their application temperatures.

The interply thickness-viscosity relationship was deter- mined from the thickness-temperature relationships of

the membrane specimens and the viscosity-temperature curves of the asphalts used to fabricate the membrane

specimens.

Interply thickness data were obtained for asphalt

application temperatures ranging from approximately

325 °F (163°C) to 500 "F (260°C). It was not possible to measure the viscosity of the asphalts above

450 °F (232°C.). In order to have viscosity-temperature data over the same temperature range as the

interply thickness-temperature data, it was necessary

to extrapolate the viscosity-temperature curves (fig. 6)

to 500 °F (260 °C). Using the NBS computer, least squares curves were fit to the viscosity-temperature data between 325 °F (163°C) and 450 °F (232°C), and

values of viscosity were predicted for asphalt temperatures above 450 °F (232°C). Viscosity-temperature

data for the asphalt samples collected before mopping

were used in the least square analyses. The computergenerated equation for the viscosity-temperature rela- tionship for the Type I asphalt determined from the

least square fit was:

11
log r, = 0.0013846535 — 153.25223Z

+ 224359530.0Z3 (1)

where 17 = viscosity and Z = 1/(°C + 273.15).

For the Type III asphalt the computer generated equation was determined to be:

log r? = —0.0096243870 — 298.62132Z

+ 300228880.0Z^ (2)

Equations (1) and (2) were used to calculate the vis- cosities of the asphalts at the temperatures at which

the mem.brane specimens were prepared. For obtaining

the calculated values of asphalt viscosity, these equations were preferred over the method described in ASTM D341-74 [10] and illustrated in figure 7. These

calculated values of viscosity are given in tables 4 and

5 along wtih the corresponding application temperatures and interply thicknesses. Values of interply thick- ness as related to the asphalt viscosities are illustrated graphically in figure 11.

It can be seen from figure 11 that a linear relation- ship between interply thickness and viscosity did not

exist over the viscosity range of 0 to 1000 centistokes (mm-/s). In the viscosity range of 500 to 1000 centi- stokes (mmVs) there was no increase in interply thickness with an increase in viscosity. The data in the

viscosity range of 500 to 1000 centistokes (mm-/s)

represented Type III asphalt applied at temperatures

from approximately 325 °F (163°C) to 350 °F

(177°C). These temperatures are below the minimum

recommended application temperatures for Type III asphalts [5, 6]. Since the data in the viscosity range

of 500 to 1000 centistokes (mm-/s) were not obtained

from recommended application temperatures and the

asphalt was too viscous for proper application, these data were not considered in subsequent analyses. Fig- ure 12 presents the interply thickness-viscosity data over the viscosity range of 0 to 250 centistokes (mm-/s). The straight line in this figure determined

from a linear regression analysis was obtained by

treating all data as being equivalent. It was assumed

that visocsity governed the interply thickness of as- phalt. Differences arising from the type of felt or

asphalt were not considered in this analysis. These

differences and their effect on interply thickness are examined in the Appendix.

5. Viscosity Criterion for the Application

of Roofing Asphalt

The interply thickness-viscosity relationship shown

in figure 13 was used as the basis for the recommended

application viscosity criterion. In 1972 Cramp, Cullen

and Tryon [4] recommended that the optimum application rate for asphalt in the fabrication of built-up

membranes be within the range of 15 to 20 pounds per 100 square feet of area (0.73 to 0.98 kg/m-). This

application rate corresponds approximately to an inter- ply thickness of 0.03 to 0.04 in (0.76 to 1.02 mm). As

shown in the shaded area of figure 13, a viscosity range

of about 60 to 145 centistokes (mm-/s) corresponds

to the interply thickness range of 0.03 to 0.04 in (0.76

to 1.02 mm). Based on the results of this study the

viscosity range, 60 to 145 centistokes (mm-/s), is the recommended optimum viscosity range for the application of roofing asphalt in built-up membranes. In practice this viscosity range can be taken as 50 to 150

centistokes (mm-/s). The range refers to asphalt vis- cosity at the time of membrane fabrication and not

1

\ r 1 r

• ORG»NC Far Tm iii asphalt o OBGANIC FELT TyPt I ASPHALT

t. ASBESTtS FB.T TYPE III ASPHALT a ASBESTOS FELT. TYPE I ASPHALT

GLASS faT. TYPE III ASPHALT

GLASS FELT; nrPt I ASPHALT

J L

100 200 300 J L

400 500 600

VISCOSITY, centistokes (mm^/s)

700 BOO 900 BOO

Figure 11. Relationship between interply asphalt thickness and viscosity for the tdscosity range of 0 to 1000 centistokes (mm'/s).

12
0 50 100 150 200 250

VISCOSITY, cenlistokes (mmVsl

Figure 12. Relationship between interply asphalt thickness and viscosity for the viscosity range oj 0 to 250 cenlistokes (mm'/s).

the viscosity of the asphalt in the kettle. To maintain

the application viscosity range, consideration should

be given to environmental conditions such as ambient

temperature and wind speed.

It is realized that the application rate of asphalt in the fabrication of built-up roofing membranes recom- mended by the roofing industry is normally 15 to 25

pounds per 100 square feet (0.73 to 1.2 kg/m'-). Such

an application rate would extend the viscosity range beyond the optimum to 220 centistokes (mm'-/s), as shown by the dashed lines in figure 13. It is recom- mended, however, that the viscosity criterion should be

based on the optimum application rate.

It is not necessary to measure the viscosity of the asphalt at the job site in order to apply the viscosity

criterion. The viscosity criterion can be used as the basis for determining the proper application temperature range for any roofing asphalt, provided that the viscosity-temperature relationship is known. An example of using the viscosity criterion to determine the application temperature range is illustrated in figure 14 for the two asphalts used to fabricate the membrane

specimens in this investigation. The shaded area in this figure indicates the recommended viscosity criterion of 50 to 150 centistokes (mm-/s). The application

temperature ranges for the asphalts are determined bv

1.0 <

a. 1 <

VISCOSITY, centistokes |tnm'/s| Figure 13. Interply thickness-viscosity relationship used as the basis for the recommended application viscosity criterion.

13
TEMPERATURE. "U

150 160 170 180 190 200 210 220 230

360 400 450 TEMPERATURE. °F

Figure 14. An example of the use of the viscosity criterion for determining the application temperature ranges for the asphalts

collected before mopping given in table 2.

the intercepts of the shaded area with the viscositytemperature curves. For the Type I asphalt the rec- ommended temperature range is about 345 to 405 °F

(174 to 207°C), and for the Type III asphalt the temperature range is about 390 to 450 °F (199 to 232 °C). Again, these recommended temperature ranges

refer only to the application temperature and not to the kettle temperature. It is emphasized that these application temperature ranges apply only to the Type

I and Type III asphalts used to prepare the membrane

specimens. Because of the wide range of viscosities for a given type of asphalt (table 1), it is necessary that the viscosity-temperature relationship of an asphalt

be known prior to application.

6. Recommendations

This study investigated the viscosities of typical

roofing asphalts at their application temperatures and

the relationship between interply asphalt thickness of roofing membrane specimens and the viscosity of the asphalt at the time of application. Based on this study

the following recommendations are made:

( 1 ) Roofing asphalts should not be applied between

empirically determined temperature limits. Asphalts of

the same type, as determined by softening point and

penetration, may have widely varying viscosities over

the application temperature range.

(2) Roofing asphalts should be applied between

temperature limits which are based on the viscosities of the asphalts over the application temperature range. Viscosity is the property which governs the flow of asphalt during fabrication of built-up roofing membranes.

(3) The optimum viscosity of the asphalt at the time

of application should be within the range 50 to 150

centistokes (mmVs). This viscosity range corre- sponded to an application rate of approximately 15 to 20 lb/ 100 ft= (0.73 to 0.98 kg/m = ). To maintain this viscosity range at application, consideration should be

given to environmental conditions, such as ambient

temperature and wind speed.

(4) The viscosity-temperature relationship should be

determined for each roofing asphalt for the application

temperature range prior to application. Using this relationship and the optimum viscosity range of 50

to 150 centistokes (mm-/s), the temperature range for applying each asphalt can be determined. It is not

necessary to measure the viscosity of the asphalt at the job site.

This investigation was conducted under the Tri- Services Investigational Program and was jointly spon- sored by the National Bureau of Standards and the Directorate of Engineering and Services, U. S. Air

Force; Naval Facilities Engineering Command, U. S. Navy; and the Office of the Chief of Engineers, U. S. Army.

The authors wish to acknowledge with thanks the persons and organizations who assisted in this research. Dr. Edwin C. Mertz, National Roofing Contractors

Association, identified the typical asphalts which were

used in this investigation. The twenty asphalts from

various sources were supplied by Mr. Robert A. Lindquist from Trumball Asphalt Company. Guidance in determining asphalt viscosities was provided by Mr.

Vytautas P. Puzinauskas, Asphalt Institute. Arrange- ments for the fabrication of the roofing membrane

specimens by Roofers Local #20 Joint Apprenticeship

Program was made by Mr. Paul L. Morris, Chairman

of the Program. Fabrication of the membrane speci- mens was carried out under the supervision of Mr. Wes

B. Weddle, Faculty Advisory to the Program. Mr. Erik

Anderson, National Bureau of Standards, contributed

to the preparation of membrane specimens.

Measurement of asphalt thicknesses and assistance in viscosity measurement was carried out by Mr. Jessie C. Hairston.

Special appreciation and thanks are extended to Dr. James J. Filliben, Statistician, National Bureau of Standards, for his advice in the planning of experimental procedures, data reduction and analyses.

14
7. References

[1] Asphalt and Tar Roofing and Siding Products 1973, Current Industrial Reports, U. S. Department of Commerce,

Social and Economic Statistics Administration, Series: MA-29A(73)-1, July 1974.

[2] Standard Specification for Asphalt for Use in Constructing Built-Up Roof Coverings, ASTM Designation D312-

71, 1975 Annual Book of ASTM Standards, Part 15, American Society for Testing and Materials, Philadelphia, Pennsylvania, 1975.

[3] Cullen, William C, The Composite Roofing Membrane,

The Roofing Spec, September 1975, p. 17. [4] Cramp, A. Philip, Cullen, William C, and Tryon, Max,

Slippage of Built-Up Roof Membranes—Causes and Prevention, National Bureau of Standards Report 10950, November 1972.

[5] A Manual of Roofing Practice, National Roofing Contractors Association, Oak Park, Illinois, 1971.

[6] Maintenance and Repair of Roofs, Department of the Army, the Navy, the Air Force, and the Marine Corps, TM 5-167, NAVFAC MO-113, AFM 91-31, MCO

P11014.9, Washington, DC, January 1974, p. 18. [7] Mertz, Edwin, Asphalt-Specifications, Properties and Heating, Roofing/Siding/Insulation, July 1975, p. 51. [8] Viscosity Testing of Asphalt and Experience with Viscosity Graded Specifications, ASTM Special Technical

Publication 532, American Society for Testing and

Materials, Philadelphia, Pennsylvania, June 1973.

[9] Standard Method of Test for Kinematic Viscosity of Asphalts (Bitumens), ASTM Designation D2170-74,

1975 Annual Book of ASTM Standards, Part 15, American Society for Testing and Materials, Philadelphia,

Pennsylvania, 1975. [10] Standard Viscosity-Temperature Charts for Liquid Petro- leum Products, ASTM Designation D341-74, 1975 Annual Book of ASTM Standards, Part 23, American

Society for Testing and Materials, Philadelphia, Pennsylvania, 1975.

8. Appendix. Relationship Between

Asphalt Thickness and Viscosity Examined

in More Detail

The optimum range of viscosity over which the hot

asphalt should be applied has been given as 50 to 150

centistokes (mm-/s). This range was based on the

interply thickness-viscosity relationship given in figure 12 for which all data were treated as equivalent. No

distinction was made between interply thickness data

for membranes fabricated from the different types of

of felt and asphalt.

If a distinction is made between the types of felt and

not between the asphalts, an interply thickness-viscosity

relationship can be determined for membranes containing each type of felt. It can be seen from these rela- tionships in figure 15, determined by regression analyses, that the asphalts applied at a given viscosity re- sulted in greater interply thicknesses in the asbestos

felt membranes.

The data were also examined by making a distinction between the types of asphalt and not between the types

of felt. The relationships shown in figure 16, as deter- mined by regression analyses, indicated that greater

interply thicknesses were observed in membranes fabri- cated from Type III asphalt. This difference in interply thickness may possibly be attributed to the Type III asphalt being more temperature susceptible than the Type I. From figure 6 it can be seen that a small de- crease in temperature caused a larger increase in the

viscosity of the Type III asphalt than for the Type I particularly at the lower temperatures.

100 150

VISCOSITY, centistokes (mm^/s)

Figure 15. Relationships between interply thickness and asphalt viscosity for the three types of membranes.

15
The relationship between interply asphalt thickness

and viscosity will depend to some extent on the rate of cooling of the hot asphalt during application. The

interply asphalt thicknesses were determined from

membrane specimens fabricated indoors at 60 °F

(16°C). Environmental conditions other than those encountered in this investigation may result in an

interply thickness-viscosity relationship different than

that shown in figure 10 because of differences in the

rate of cooling of the asphalt. Conditions affecting the cooling rate of asphalt include air temperature, wind

speed, substrate temperature and the specific heat of the substrate. The type of construction technique may also affect the interply thickness-viscosity relationship. The inter- ply thickness of roofing membranes may be affected by

brooming, unrolling of felts, and the type of equipment

for spreading asphalts and laying felts.

I

16
NBS-1 14A (REV. 7-73)

U.S. DEPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET

1. PUBLIC ATION OR REPORT NO. NBS BSS-92

2, Gc>v *t Aece s s ion No.

3. \<i i ipi' rit'-. A< .CSS ion No.

4. TITLE AND SUBTITLL

The Viscosities of Roofing Asphalts at Application

Tennperatur es

5. Publitation Dale December 1976

6. Performing Organization Cod<-

T A T TTW r^D ^ Q ^ /. A U I rHJKto } Walter J. Rossiter, Jr. and Robert G. Ma they

8. Performing Organ. Report No.

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Project/Taslc/Work Unit No.

11. Contract /(irant No.

12, Sponsoring Organization Name and Complete Address (Street, City, State, ZIP)

Naval Facilities Engineering Command, Department of the Navy,

Washington, DC 20390; Directorate of Civil Engineering, U.S.

Air Force, Washington, DC 20330; Office of Chief of Engineers,

U.S. Army, Washington, DC 20314; and NBS

13. Type of Report & Period Covered Final 1976

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES,

16. ABSTRACT (A 200-word or less (actual summary ol most significant information. If document includes a significant

bibliography or literature survey, mention it here.) The optimum range of viscosity over which hot asphalt should be applied in the

fabrication of ^uilt-up roofing membranes was determined to be 50 to 150

centistokes (mm /s). This viscosity range was based on the relationship between

interply thickness and application temperature of asphalt obtained from roofing

membrane specimens fabricated in the field. Because laboratory measurements

showed a wide range of viscosities for roofing asphalts of the same type over their application temperature ranges, it was recommended that asphalts be applied

at temperatures based on viscosity and not empirically determined temperature

limits. In practice, the viscosity-temperature relationship should be determined

for each roofing asphalt for the application temperature range prior to use. Using this relationship and the optimum viscosity range, the temperature range

for applying each asphalt can be determined.

17. KEY WORDS (six to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper name; separated by semicolons)

Application temperature; asphalt; built-up roofing; interply thickness;

roofing membranes; viscosity.

18. AVAILABILITY [^Unlimited

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Technical Notes—Studies or reports which are complete

in themselves but restrictive in their treatment of a

subject. Analogous to monographs but not so comprehensive in scope or definitive in treatment of the subject area. Often serve as a vehicle for final reports of work performed at NBS under the sponsorship of other government agencies.

Voluntary Product Standards—Developed under proce- dures published by the Department of Commerce in Part

10, Title 15, of the Code of Federal Regulations. The

purpose of the standards is to establish nationally rec- ognized requirements for products, and to provide all concerned interests with a basis for common understanding of the characteristics of the products. NBS

administers this program as a supplement to the activities of the private sector standardizing organizations.

Consumer Information Series—Practical information,

based on NBS research and experience, covering areas

of interest to the consumer. Easily understandable language and illustrations provide useful background knowledge for shopping in today's technological marketplace.

Order above NBS publications from: Superintendent

of Documents, Government Printing Office, Washington,

D.C. 20402. Order following NBS publications—NBSJR's and FIPS

from the National Technical Information Services,

Springfield, Va. 22161. Federal Information Processing Standards Publications (FIPS PUBS)—Publications in this series collectively constitute the Federal Information Processing Standards Register. Register serves as the official source of information in the Federal Government regarding stand- ards issued by NBS pursuant to the Federal Property

and Administrative Services Act of 1949 as amended.

Public Law 89-306 (79 Stat. 1127), and as implemented

by Executive Order 11717 (38 FR 12315, dated May 11, 1973) and Part 6 of Title 15 CFR (Code of Federal

Regulations).

NBS Interagency Reports (NBSIR)—A special series of interim or final reports on work performed by NBS for

outside sponsors (both government and non-government). In general, initial distribution is handled by the sponsor; public distribution is by the National Technical Information Services (Springfield, Va. 22161) in paper copy or microfiche form.

BIBLIOGRAPHIC SUBSCRIPTION SERVICES

The following current-awareness and literature-survey

bibliographies are issued periodically by the Bureau:

Cryogenic Data Center Current Awareness Service. A

literature survey issued biweekly. Annual subscription: Domestic, $20.00; Foreign, $25.00.

Liquified Natural Gas. A literature survey issued quarterly. Annual subscription: $20.00,

Superconducting Devices and Materials. A literature survey issued quarterly. Annual subscription: $20.00.

Send subscription orders and remittances for the pre- ceding bibliographic services to National Bureau of Standards, Cryogenic Data Center (275.02) Boulder,

Colorado 80302.
U.S. DEPARTMEIMT OF COMMERCE

National Bureau of Standards

Washington, D C. 20234

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