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NISTIR 88-3870

Suggested Research Topics for

the Construction Engineering

Research Laboratory (CERL)

Program, Evaluation of Roofing

Materials Degradation

Processes

Walter J. Rossiter, Jr. and Larry W. Masters

U.S. DEPARTMENT OF COMMERCE

National Institute of Standards and Technology

(Formerly National Bureau of Standards)

National Engineering Laboratory

Center for Building Technology

Gaithersburg, MD 20899

November 1988

Prepared for: U.S. Army Construction Engineering Research Laboratory

P O Box 4005

Champaign, IL 61820-1305

76 V—ri Sttmutatlng AmoKs* Progncs*

NISTIR 88-3870

Suggested Research Topics for

the Construction Engineering

Research Laboratory (CERL)

Program, Evaluation of Roofing

Materials Degradation

Processes

Walter J. Rossiter, Jr. and Larry W. Masters

U.S. DEPARTMENT OF COMMERCE

National Institute of Standards and Technology

(Formerly National Bureau of Standards)

National Engineering Laboratory

Center for Building Technology

Gaithersburg, MD 20899

November 1988

National Bureau of Standards became the

National Institute of Standards and Technology on August 23, 1988, when the Omnibus Trade and

Competitiveness Act was signed. NIST retains

all NBS functions. Its new programs will encourage

improved use of technology by U.S. industry.

Prepared for: U.S. Army Construction Engineering Research Laboratory

P O Box 4005

Champaign, IL 61820-1305

U.S. DEPARTMENT OF COMMERCE

C. William Verity, Secretary

NATIONAL INSTITUTE OF STANDARDS

AND TECHNOLOGY

Ernest Ambler, Director

ABSTRACT

This document was prepared at the request of U.S. Army Construction

Engineering Research Laboratory (CERL) to provide assistance in

developing plans for conducting roofing research under its

program entitled, "Evaluation of Roofing Materials Degradation

Processes." Five areas of needed research dealing with servicelife prediction of membrane performance were suggested:

o Identification of Failure Modes and Mechanisms

o Service-Life Criteria for Polymer-Modified Bitumen

Membranes

o Service-Life Criteria for Adhesively-Bonded Weathered

Vulcanized-Rubber Membranes

o Service-Life Criteria for PVC Membranes

o Techniques for Quality Assurance of Membrane Materials

The suggestions are based on needs of the industry in the area of

service-life prediction as described in the NIST research plan

and the summary of the Round Table Seminar on Roofing Research.

Although the research topics proposed cover the wide range of

newer membrane products currently available in the U.S. industry,

the link between the topics is that of service-life prediction

and quality assurance. Completion of the studies recommended in

this report would provide valuable information on membrane

properties and predictive methodologies.

Key words: low-sloped roofing, membranes, performance, quality

assurance, roofs, research needs, service-life prediction

111
TABLE OF CONTENTS

Page

ABSTRACT iii

1. INTRODUCTION. ..... ..... 1

1 . 1 Background . . ...... l

1.2 Past Documents on Research Needs and

Service-Life Evaluation. ............ 3

1.3 Objective of the CERL Program. ......... 7

1.4 Objective of the Present Report. 9

2. SUGGESTED RESEARCH AREAS FOR THE CERL PROGRAM .... 11

2.1 Identification of Failure Modes and Mechanisms . 12

2.2 Service-Life Criteria for Polymer-Modified

Bitumen Membranes . 13

2.3 Service-Life Criteria for Adhesively-Bonded

Weathered Vulcanized-Rubber Membranes. 14

2.4 Service-Life Criteria for PVC Membranes. .... 15

2.5 Techniques for Quality Assurance of

Membrane Materials ....... 16

3. SUMMARY . 17

4. REFERENCES. ........ 19

5. ACKNOWLEDGMENTS ......... 20

IV
LIST OF TABLES

Page

Table 1. Summary of Research Needs Suggested by

the Round Table Participants .... 21

LIST OF FIGURES

Page

Figure 1. Sequence of Major Roofing Activities and Goals

Proposed in the NBS Roofing Research Plan [4] . 22

Figure 2. Steps in the Practice in ASTM E 632 for

Developing Predictive Service-Life Tests [6]. . 23

v

1 . INTRODUCTION

This document was prepared at the request of CERL to provide

technical assistance in its preparations for carrying out the

program. It presents some recommendations for research on lowsloped roofing systems to be included in the U.S. Army Construction

Engineering Research Laboratory (CERL) program entitled, "Evaluation

of Roofing Materials Degradation Processes."

1 . 1 Background

The current U.S. roofing industry scarcely resembles that of the

mid-1970s. Fundamental changes, often described as revolutionary,

have occurred in the types of materials used for membranes and

insulations, and also in the application methods for systems.

Elastomeric and thermoplastic single-ply and polymer-modified

bituminous membranes are now used in considerable amounts

whereas, only a decade ago, built-up membranes were almost the

only type of waterproofing used for low-sloped roofs. Where

built-up roofing is now specified, fibrous glass mats and, in

some cases, polyester fabrics have essentially eliminated

organic- and asbestos-based felts as the reinforcement of choice.

Data on membrane use compiled by the U.S. National Roofing

Contractors Association (NRCA) illustrate the changes. For

example, NRCA indicated that, in early 1983, about 175 membrane

products were available for low-sloped roofing whereas, in late

1987, the number had increased to 544 [1].
Before the mid-1970s, components of membrane roofing systems were

all adhered, one layer to another. Now, the systems also may be

partially attached, loose laid with ballast, or a combination of

two or more methods. The different application procedures have

resulted in problems with performance that were unknown a decade

and one-half ago. For example, inadequately ballasted roofs may

be readily damaged or destroyed by high winds.

The changes which have occurred in the industry have, for the

most part, been beneficial [2]. Low-sloped roofing today is

generally performing better than in the early 70s. Moreover, the

changes of the last decade have heightened the industry's

awareness that the factors affecting roofing performance must be

more fully understood to assure success with new materials and

systems

Although the new materials and systems have generally performed

satisfactorily, their use has not been trouble free. One of the

key concerns facing the industry is the lack of techniques for

reliably evaluating service-life of membranes based on short-term

tests [3]. Many of the current membrane materials are new to the

market and were introduced with only limited in-service history.

Consensus standards and minimum levels of performance have not

been developed for the newer membrane materials and a technical

basis for their development is needed. Moreover, an urgent need

exists to develop methods for assuring the quality and reliability

of the long-term performance of low-sloped roofing.

2
1 . 2 Past Documents on Research Needs and Service-Life Evaluation

1.2.1 NBS Special Publication 659 . In 1983, the National Bureau

of Standards (NBS) published Special Publication 659, "Low-Sloped

Roofing Research Plan" [4]. The development of this plan was

motivated by the changes that have occurred in roofing technology

and the need to provide solutions to roofing performance problems.

The major thrust of the plan was directed towards materials and

systems research and the application of measurement technology to

roofing research. The intent was to establish, through the

suggested research, the technical bases for developing standards

and performance levels which can form the rationale for the

selection of cost-effective and durable roofing materials. The

plan was reviewed by a broad segment of the roofing industry's

leaders before publication.

Four major areas for research for low-sloped roofing were covered

in the NBS plan: (1) low-sloped roofing systems, (2) roofing

membranes including built-up and single-ply, (3) thermal insulations

used in roofing systems, and (4) condition assessment and repair.

The proposed tasks within the four research areas were concentrated

in the following categories:

o Characterization of failure mechanisms of roof membranes and

systems as a basis for understanding roofing performance and

advancement of roofing technology,

o Development of minimum levels of performance for roofing

systems, membranes, and thermal insulations.

3
o Theoretical analysis of roofing system performance and the

development of models for predicting performance,

o Advancement of the in situ condition assessment and repair

of roofs.

Figure 1 is taken from the NBS report [4]. It illustrates the

four major research areas included in the plan, some specific

tasks associated with each area, and the inter-relations between

the research areas. As is evident from Figure 1, the suggested

research is extensive. Its achievement is expected to require

the joint efforts of many research laboratories in the roofing

community.

1.2.2 Roofing Research Round Table . In December 1987, the

National Bureau of Standards, the National Roofing Contractors

Association (NRCA) , and the Roofing Industry Educational Institute

( RIEI ) published a summary of the Round Table Seminar entitled,

"Roofing Research: the Challenge and the Opportunity" [2]. The

Round Table convened about 50 individuals representing a crosssection of the U.S. roofing industry to discuss the needs for

research to improve the performance of low-sloped roofing and to

recommend research actions. The discussions of the Round Table

were divided into two parts: elastomeric and thermoplastic

roofing systems, and bituminous roofing systems. Although no

attempt was made to reach consensus during the discussions,

4
numerous suggestions for needed research were made by the

participants. The suggestions are summarized in Table 1.

Of the items listed in Table 1, strong support was given for the

development of:

o diagnostic techniques and measurement tools for roofing

condition assessment

o a statistical database on in-service performance and

failures to provide a basis for selecting the problems that

require study

o improved methods for the characterization of membrane

materials, and the changes experienced in service

o more relevant accelerated exposure tests and techniques for

measuring incipient changes in membrane properties

o performance testing and criteria for systems.

A comparison of the Round Table summary of research suggestions

(Table 1) with the major areas of proposed research in the NBS

plan (Figure 1) shows them to be consistent with each other

[2,4]. Both draw attention to performance testing and criteria

for membrane systems, characterization of membrane materials and

deterioration mechanisms, durability testing, and condition

assessment. These areas of research are suggested as essential

elements for inclusion in the CERL program on "Evaluation of

Roofing Materials Degradation Processes."

5
1.2.3 ASTM Standard Practice E632 . From the evidence provided

by the NBS plan [4] and the Round Table Seminar [2], it is clear

that studies to improve the long-term performance of low-sloped

roofs are needed. Experience has shown short-term laboratory

tests for predicting how innovative materials and systems will

perform in service over the long term often are seldom fully

satisfactory [3]. The shortcomings of short-term tests include [5]

o They are seldom developed to assure that the mechanisms of

degradation are the same in the short-term test and in

service

.

o Some of the key factors which can contribute to early

failures or poor performance (such as application quality)

are often not accounted for.

o The levels of performance required of the material or system

are not defined.

o Recommendations are usually not made as to how the results

of standard tests for different materials should be compared

to each other.

In response to the need to overcome these shortcomings and to

have available a systematic approach for developing improved

tests for durability of building materials and systems, ASTM E

632, "Standard Practice for Developing Accelerated Tests to Aid

Prediction of the Service Life of Building Components and

Materials," was developed [6].

6
The Practice outlines a logical sequence of steps to be undertaken

in developing tests for predicting the service life of building

materials and components. It is applicable to innovative

materials and components and to existing materials and components

even if used under conditions outside the normally expected

range. The sequence of steps given in the ASTM Practice is shown

in Figure 2. As seen in this figure , the procedures are divided

into four parts: (1) problem definition, (2) pre-testing, (3)

testing, and (4) interpretation and reporting of data. The

application of ASTM E 632 to new roofing membrane materials and

systems has previously been discussed [3]. Studies conducted as

part of the CERL program on "Evaluation of Roofing Materials

Degradation Processes" should be based on the E 632 methodology.

1 . 3 Objective of the CERL Program

The objective of the CERL program, "Evaluation of Roofing

Materials Degradation Processes," is to provide methods for

evaluating the quality and service life of membrane roofing

systems which can become the basis for standards and specifications 1. The task description for the CERL program indicates that:

o In conducting the research, the procedures given in ASTM E

632 should be followed. Processes by which roofing materials

degrade while in the service environment should be determined,

and the - parameters of change are to be identified.

1 The summary of the CERL program given in this section was

taken from a personal communication from D. Bailey, CERL.

7
o Models which describe the essential aspects of system

performance should be developed and include relationships

between specific modes of failure and properties of the

roofing materials.

o Based on the identification of failure modes, laboratory

studies should be undertaken to develop new or improved

methods for characterizing the important properties of

membrane materials, and for evaluating their resistance to

failure through the more commonly occurring degradation

processes. The methods for service life evaluation should

be based on probabilistic procedures for predicting longterm performance. Such statistically-based techniques can

provide increased confidence in extrapolating the results of

short-term tests to long-term performance [7].

The development of understanding about degradation mechanisms and

the factors that affect changes in material properties will

provide knowledge necessary to prepare specifications that

minimize material degradation, thus reducing long-term maintenance

and repair costs. As a long-term goal, it also will help the

development of standard test(s) which will more reliably predict

serviceability and performance of membrane roofing.

8
1 . 4 Objective of the Present Report

As mentioned in the introduction, this report was prepared at the

request of CERL. Its purpose is to provide technical assistance

in planning studies to develop improved methods for evaluating

the quality and service-life of low-sloped roofing membrane

materials and systems. The report outlines studies for research

in the areas associated with the evaluation of the long-term

performance of membrane materials and systems. The studies

proposed for consideration were selected primarily based on

consideration of the NBS plan [4] and the Round Table recommendations

[2], as previously mentioned. Because of concerns about the

long-term performance of relatively new, but widely used, roof

systems such as those incorporating elastomeric, thermoplastic,

and modified bituminous membranes, the proposals for needed

research, described herein, emphasize the elastomeric, thermoplastic,

and modified bitumen systems.

In selecting the research topics that follow in the next section

of the report, it was kept in mind that they must be consistent

with both:

1. the key needs of the industry (primarily as recommended by

the NBS Research Plan and the Round Table Seminar) , and

2. the objectives of the CERL roofing research program.

9
The important needs of the industry include the establishment of

a means of providing a database on in-service performance and

failures, the development of improved techniques for assessing

the service-life of roofing materials and systems, and the

development of improved methods for characterizing membrane

materials. These topics are addressed in the five research areas

that are suggested for the CERL program in the next section of

the report. The first area deals with analysis of in-service

performance; the next three concern service-life assessment; and

the fifth focuses on techniques for quality assurance of membrane

materials

.

10
2. SUGGESTED RESEARCH AREAS FOR THE CERL PROGRAM

This section of the report presents areas of research suggested

for inclusion in the CERL program. These research areas are:

o Identification of Failure Modes and Mechanisms

o Service-Life Criteria for Polymer-Modified Bitumen

Membranes

o Service-Life Criteria for Adhesively-Bonded Weathered

Vulcanized-Rubber Membranes

o Service-Life Criteria for PVC Membranes

o Techniques for Quality Assurance of Membrane Materials

These studies focus on serviceability and encompass field and

laboratory studies, as well as the development of mathematical

models on rates of deterioration. Though the studies are

complementary, each is intended to stand alone. The link between

the individual studies is the evaluation of service life and

improvement of long-term performance.

The approach taken to outline each proposed study is to state a

title and objective. These are followed by comments concerning

the background and significance of the proposed study. Then a suggested technical approach is given. Finally, an estimate of

the time required to conduct each study is provided.

11
2 . 1 Identification of Failure Modes and Mechanisms

Obi ective : To obtain and analyze information on the in-service

performance and failure modes of low-sloped roofing membranes and

systems, particularly those that have a relatively short history

of in-service performance such as the single-ply and modified

bitumens

Comments : One of the major topics of discussion at the Round

Table Seminar on Roofing Research [2] was the lack of a significant

database on field performance which could aid service-life

predictions. A database on field performance also is needed to

guide research efforts and to aid the selection of important

research projects. The information obtained from the field can

help direct the development of accelerated exposure tests. In

addition, analysis of information on in-service performance and

failure modes can help form the basis for the development of

models used to describe the interactions of the various components

of low-sloped roofing systems. It is anticipated that assistance

in obtaining data on in-service performance will be needed from

industry associations such as NRCA, MRCA, and RCI 2 . It would be

beneficial to explore mechanisms for receiving non-proprietary

data from manufacturer and related associations.

Recommended Approach :

o Conduct field inspections of newer roofing systems to obtain

information on in-service performance; where possible, obtain

field specimens from new and existing roofs for measurement of

selected performance-related properties.

o Where problems are experienced, identify probable failure

mechanisms

o Work with industry associations such as NRCA, MRCA, and RCI to

obtain data on in-service performance; analyze data as to

probable causes of the problems identified.

o Explore the potential for development of an industry database

on in-service performance to identify the major performance

problems and recommend research activities as solutions to the

problems identified.

o Prepare a report on the findings of the field investigations

including recommendations for needed research.

Estimated Duration : Concurrent with laboratory studies.

2 National Roofing Contractors Association (NRCA) , Midwest

Roofing Contractors Association (MRCA) , and Roof Consultants

Institute (RCI)

12
2 . 2 Service-Life Criteria for Polvmer-Modif ied Bitumen Membranes

Objective ; To develop a methodology for evaluating the long-term

weathering performance of polymer-modified bituminous membrane

materials

.

Comments : The use of polymer-modified bituminous membranes as

the waterproofing components of low-sloped roofing systems is

increasing rapidly in the U.S. Recent estimates indicate that

these materials account for 15 percent of the membranes currently

installed and predictions are that the use will increase to 25

percent by 1990. Voluntary consensus standards in the U.S. are

not available to evaluate these products and are not expected for

3 years or more. NIST has been assisting the Department of

Defense (DoD) in the development of interim criteria for use in

guide specifications. Research conducted in the DoD-sponsored

study has indicated that test methods for assessing long-term

weathering are not available. In particular, preliminary UVresistance (xenon arc) tests of selected modified bitumens raised

questions concerning the applicability of a proposed ASTM

procedure for assessing the UV resistance of these materials.

Recommendations were made that research be conducted to provide a weathering test method for incorporation in the criteria.

Recommended Approach ;

o Develop a research plan following the methodology outlined in

ASTM E 632. It is anticipated that the key degradation

factors incorporated in the test program would be heat and UV

radiation.

o Investigate the use of sensitive analytical methods for

detecting changes in membrane material properties, uniformity

of membrane material, or the phase distribution of the

polymer-bitumen matrix.

o Develop a test procedure for exposing selected modified

bitumens to heat and UV radiation using statistical techniques.

It is anticipated that the membrane materials in this laboratory

program could be some of the same products that CERL has under

investigation in its field studies on modified bitumens.

o Subject the specimens to the heat and UV conditions over time,

and measure the changes in properties. Analyze the data using

reliability theory and develop degradation models on the rate

of deterioration.

o Publish reports describing the progress and interim results of

the study. Include recommendations for a laboratory procedure

for assessing the long-term performance of modified bitumens

in the final report.

o Draft a test method suitable for presentation to ASTM and

incorporation in guide specifications.

Estimated Duration ; 3-4 years.

13
2 . 3 Service-Life Criteria for Adhesively-Bonded Weathered

Vulcanized-Rubber Membranes

Objective: To develop a methodology for assuring the quality of

bonded seams in weathered vulcanized-rubber membranes.

Comments : The use of vulcanized-rubber materials (primarily

EPDM) for low-sloped roofing membranes has become common in the

U.S. Current estimates indicate that over a billion square feet

are now applied annually. EPDMs are non-polar, relatively inert

rubbers; this makes the adhesive-bonding of sheets, forming

membrane seams, a critical parameter associated with long-term

performance. This may be even more critical as time passes, and

patches and splices are needed. A key concern expressed in the

roofing industry is that, as these membranes weather, the

rubber's surface characteristics may be altered such that

successful bonding of the aged material may become difficult.

For example, in the CERL study of EPDM roofing at Ft. Benning, it

was found that repairs to cut sheets delaminated within months

after formation. This occurred even though industry guidelines

for repair were followed. A technical basis for making sound

repairs to weathered EPDM is lacking and should be developed.

Recommended Approach :

o Investigate methods for characterizing EPDM surfaces regarding

properties relevant to bonding, such as scanning electron

microscopy, Fourier transform infrared spectroscopy, surface

energy, and other analytical surface chemistry techniques.

o Obtain samples of weathered EPDM membranes and characterize

their surfaces; compare the characteristics of the weathered

surfaces with those of unaged samples.

o Investigate techniques for preparing surfaces of weathered

EPDM for bonding; characterize the surfaces of the materials

before and after using the surface preparation techniques.

o Prepare seams from weathered EPDM sheets; measure the initial

strength of the bonds as a function of the cleaning procedures.

o Based on the results of the bond strength tests, conduct timeto failure experiments on seams prepared from weathered

material; compare the results to those obtained in previous

NIST time-to- failure studies on unaged EPDM; develop a

degradation model related to the rate of seam delamination.

o Prepare an interim report of the progress of the study would

be prepared; publish a final report including recommendations

for properly preparing the surface of weathered EPDM before

bonding.

o Prepare a draft cleaning method suitable for presentation to

ASTM and for incorporation in guide specification.

Estimated Duration : 2 years.

14
2 .4 Service-Life Criteria for PVC Membranes

Objective : To develop a methodology for evaluating the long-term

weathering performance of poly (vinyl chloride) (PVC) membrane

materials

Comments : Poly (vinyl chloride) (PVC) is the major thermoplastic

polymer that has been used as single-ply membranes in low-sloped

roofing systems. The Corps of Engineers has a guide specification

for PVC roofing. PVC is a rigid material which must be plasticized

to provide flexibility so that it may be used as a sheet membrane.

A key performance requirement associated with the long-term

performance of PVC membranes is the permanency of the plasticizer.

Plasticizer loss can cause shrinkage and embrittlement of the

material, which can lead to cracking and splitting of the

membrane. ASTM has developed a specification for PVC membranes

that contains requirements dealing with heat and UV exposure.

Although these requirements concern, to a limited extent, the

permanency of the plasticizer in a sheet, they do not provide for

an evaluation of its long-term performance in service. Considering

the critical nature of the ability of a sheet to retain plasticizer,

a methodology to evaluate long-term performance, including

plasticizer permanency, needs to be developed.

Recommended Approach :

o Develop a research plan following the methodology outlined in

ASTM E 632. It is anticipated that the key degradation

factors incorporated in the test program would be heat and UV

radiation, perhaps in conjunction with water immersion.

o Investigate the use of sensitive analytical methods for

detecting changes in membrane material properties and loss of

plasticizer; it is anticipated that thermal analysis techniques

and microscopy would play a major role in this regard.

o Develop a test procedure using statistical techniques for

exposing selected PVC membrane materials to heat and UV

radiation. If available, unaged materials comparable to those

CERL has under investigation in its field studies on PVC

systems should be used.

o Subject the specimens to selected exposure conditions (e.g.,

heat and UV) over time and measure the changes in properties.

Analyze the data and develop degradation models on the rate of

deterioration

o Publish reports describing the progress and interim results of

the study. A final report would contain recommendations for a laboratory procedure for assessing the long-term performance

of PVC membrane materials.

o Draft a test method suitable for presentation to ASTM and for

incorporation in guide specification.

Estimated Duration : 2-3 years.

15
2 . 5 Techniques for Quality Assurance of Membrane Materials

Objective : To investigate the use of quality assurance techniques

for characterizing the properties of membrane materials.

Comments : One of the subjects discussed at great length by the

Round Table participants was the characterization of low-sloped

roofing membrane before and after aging. They acknowledged that

materials change and that the changes may not always be detrimental,

but presently the basis for making such determinations is not

available. A suggestion of the Round Table was that a need

exists to develop sensitive methods for the characterization of

membrane materials and to develop criteria for judging whether

the changes are within acceptable limits. Most importantly, the

development of the characterization methods should keep in mind

the fundamental chemical processes that materials undergo during

aging. The CIB/RILEM Roofing Committee has recently recommended

that thermal analysis (TA) techniques be applied to membrane

characterization. Although the Committee presented preliminary

data on some typical properties of new or laboratory exposed

specimens, no data were available for materials that had aged in

service. The technical bases for using thermal analysis techniques

for membrane characterization does not exist and needs to be

developed.

Recommended Approach :

o Selected samples of elastomeric, thermoplastic, and bituminous

membrane materials would be subjected to thermal analysis (TA)

techniques. The techniques used in the investigation would

include thermogravimetric analysis (TGA) , dynamic mechanical

analysis (DMA) , and differential scanning calorimetry (DSC)

The initial analyses would set baseline data for the samples.

o Subject the selected samples to pre-testing, as described in

ASTM E 632, to determine changes occurring in the materials

that can be detected by the TA techniques.

o Conduct field inspections of aged roofs and obtain membrane

samples. Include roofs both performing satisfactorily and

with problems. In addition, sample so that some specimens are

taken from sections of the roof that have received relatively

little exposure. To the extent possible, include in the

inspections roofs for which unaged, original material was

available. It is anticipated that the inspections will be

selected with the assistance of industry associations such

NRCA, MRCA, and RCI

o Conduct TA analyses on the specimens removed from the roofs.

Analyze the data for changes experienced by the membrane

materials over time; make recommendations for allowable

change in material properties (as related to type of material

and roof condition)

o A report would be prepared including recommendations on TA

methods for assessing the quality of membrane materials.

Estimated Duration : 2-3 years

16
3 . SUMMARY

This document was prepared at the request of CERL to provide

assistance in developing plans for conducting roofing research

under its program entitled, "Evaluation of Roofing Materials

Degradation Processes." Five areas of needed research dealing

with service-life prediction of membrane performance were

suggested:

o Identification of Failure Modes and Mechanisms

o Service-Life Criteria for Polymer-Modified Bitumen

Membranes

o Service-Life Criteria for Adhesively-Bonded Weathered

Vulcanized-Rubber Membranes

o Service-Life Criteria for PVC Membranes

o Techniques for Quality Assurance of Membrane Materials

The suggestions are based on needs of the industry in the area of

service-life prediction as described in the NBS research plan and

the summary of the Round Table Seminar on Roofing Research.

The research would be conducted according the outline given in

ASTM E 632.

Although the research topics proposed cover the wide range of

newer membrane products currently available in the U.S. industry,

the link between the topics is that of service-life prediction

and quality assurance. As discussed in the Round Table Seminar,

the roofing industry lacks predictive tests on long-term performance.

Roofing materials are often not properly characterized regarding

17
long-term performance before introduction into the market,

placing the owner in the position of providing the testing ground

for the materials [2].

The laboratory-based research studies recommended in this report

would provide valuable information on membrane properties and

predictive methodologies for each classification of newer

material. The benefit would be gained by the industry as a whole

and not limited only to CERL. A major benefit is the tutorial

factor in that such studies would demonstrate a methodology for

performing service-life tests and developing such methods for

incorporation in standards. One significant result may be that

industry task groups, working through an organization such as

ASTM, could continue to develop service-life tests as needed.

From the point of view of benefits to the CERL program, the

accomplishment of the studies outlined would contribute to its

long-term goal of providing improved Army guide specifications

that minimize material degradation. The ultimate result would be

the construction of low-sloped roofs for Army buildings having

reduced maintenance and repair costs.

18
4 . REFERENCES

1. Roofing Materials Guide . Volume 11, National Roofing

Contractors Association, Rosemont, IL (August 1987)

2 . Roofing Research: the Challenge and the Opportunity . National Roofing Contractors Association, Rosemont, IL

(December 1987) .

3. Rossiter, Walter J., Jr. and Mathey, Robert G., "A Methodology

for Developing Tests to Aid Service-Life Prediction of

Single-ply Roofing Membranes," Proceedings, 7th Conference

on Roofing Technology, National Roofing Contractors Association,

Rosemont, IL (April 1983)

4. Cullen, William C., Rossiter, Walter J., Jr., Mathey, Robert

G. , and Clifton, James R. , "Low-Sloped Roofing Research

Plan," Special Publication 659, National Bureau of Standards

(U.S.), Washington, DC (July 1983), 40 pages.

5. Frohnsdorff, G. , Masters, Larry W. , and Martin, Jonathan W.

,

"An Approach to Improved Durability Tests for Building

Materials and Components," Technical Note 1120, National

Bureau of Standards (U.S.), Washington, DC (July 1983), 35

pages

6 . Standard Practice for Developing Accelerated Tests to Aid

Prediction of the Service Life of Building Components and

Materials . Designation E 632-82, Annual Book of ASTM

Standards, ASTM, Philadelphia, PA 19103.

7. Martin, Jonathan W. , "Service-life Prediction from Accelerated

Test Results Using Reliability Theory and Life Testing

Analysis," in Problems in Service-life Prediction of

Building and Construction Materials . Masters, L.W. , Ed.,

NATO AS I Series, Martinus Nijhoff Publishers, Dordrecht

(1985) pp. 191-212.

19
5 . ACKNOWLEDGMENTS

The preparation of this report was sponsored by the, U.S. Army

Construction Engineering Research Laboratory (CERL) , whose

support the authors gratefully acknowledge. The encouragement of

David Bailey, CERL, who assisted in the development of the

project, is sincerely appreciated. Thanks are also extended to

the authors NIST colleagues, Geoffrey Frohnsdorff, Jonathan

Martin, and Mary McKnight, for their valuable comments and

suggestions on a draft of the report.

20
Table 1. Summary of Research Needs Suggested by the Round Table

Participants

.

1. Elastomeric and Thermoplastic Roofing Systems

Diagnostics

o Performance testing and criteria for systems

o Methods and equipment for diagnostic testing

o Characterization after in-service performance

o Statistical database on in-service performance

o Requirements for good maintenance practice

System Characterization

o Sensitive methods for characterization

o Material characterization as related to systems and environment

o Relevant accelerated tests and techniques for incipient change

o Database on in-service performance

In Situ Moisture

o Definition of excessive moisture and its effects

o Understanding of moisture migration under dynamic conditions

o Improved NDE techniques for determining moisture content

o Definition of potential corrosion with mechanical fasteners

Looking Ahead for Single-Ply

o Improved communication among all segments of the industry

o Understand roof performance as related to envelope performance

o Modelling techniques for performance prediction

o Improved methods for adhering components together

2. Bituminous Roofing Systems

Selection Criteria for Polymer-Modified Bitumens

o Development of performance standards

o Development of test methods for performance standards

o Investigation of the applicability of the Agrement concept

Application Techniques for Polymer-Modified Bitumens

o Definition of temperature limitations

o Development of substitute methods for torch application

Base Flashings for Bituminous Roofing

o Development of prescriptive and performance requirements

o Definition of the state-of-the-art of flashing performance

Insulation

o Development of performance requirements for insulations

o Determination of performance requirements for fasteners
RESEARCH AREA

Membranes

Low-sloped

Roofing Systems

Thermal Insulation

Condition Assessment

and Repair

Figure 1. Sequence of Major Roofing Activities

Proposed in the NBS Roofing Research

and Goals

Plan [4].

22
PART 1 - P R06LER DEFINITION

Figure 2. Steps in the Practice in ASTM E 632 for

Developing Predictive Service-Life Tests [6]

23
N BS-1 1 4A (REv. 2-80

U.S. DEPT. OF COMM.

4.

BIBLIOGRAPHIC DATA

SHEET (See instructions)

1. PUBLICATION OR 2 REPORT NO. NISTIR 88-3870

. Performing Organ. Report No. 3. Publication Date NOVEMBER 1988

TITLE AND SUBTITLE

Suggested Research Topics for the CERL Program

Evaluation of Research Materials Degradation Processes

5. AUTHOR(S)

Walter J. Rossiter, Jr. and Larry W. Masters

6. PERFORMING ORGANIZATION (If joint or other than NBS. see instructions) 7. Contract/Grant No. NATIONAL BUREAU OF STANDARDS -

U.S. DEPARTMENT OF COMMERCE

GAITHERSBURG, MD 20899

9.

SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street. City. State, ZIP)

U.S. Army Construction Engineering Research Laboratory

. Type of Report & Period Covered

PO Box 4005

Champaign, IL 61820-1305

10.

SUPPLEMENTARY NOTES

Document describes a computer program; SF-185, FlPS Software Summary, is attached.

11.

ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bi bl i o graph y or I i teratu re survey, mention it here)

This document was prepared at the request of U.S. Army Construction Engineer^

Research Laboratory (CERL) to provide assistance in developing plans for

conducting roofing research under its program entitled, "Evaluation of

Roofing Materials Degradation Processes." Five areas of needed research

dealing with service-life prediction of membrane performance were suggested:

o Identification of Failure Modes and Mechanisms

o Service-Life Criteria for Polymer-Modified Bitumen Membranes

o Service-Life Criteria for Adhesively-Bonded Weathered

Vulcanized-Rubber Membranes

o Service-Life Criteria for PVC Membranes

o Techniques for Quality Assurance of Membrane Materials

The suggestions are based on needs of the industry in the area of servicelife prediction as described in the NIST research plan and the summary of

the Round Table Seminar on Roofing Research. Although the research topics

proposed cover the wide range of newer membrane products currently available

in the U.S. industry, the link between the topics is that of service-life

prediction and quality assurance. Completion of the studies recommended in

this report would provide valuable information on membrane properties and

predictive methodologies.

12. KEY WORDS (Six to tw e/ve entries; alphabet/ cal order; cap/ to 1 i ze only proper names; and separate key words by semicolons)

low-sloped roofing; membranes, performance, quality assurance, roofs, research needs;

service-life prediction.

13. AVAILABILITY 14. NO. OF

PRINTED PAGES

^ Unlimited For Official Distribution. Do Not Release to NTIS 29

Groe r - rorr Superintendent of Documents, U.S. Government Printing Office, Washington, D.C.

15. Pri ce 20 “*02.

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Order From: National Technical Information Service (NTIS), Springfield, VA. 22161

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