AlllOD =nb31b

NATL INST OF STANDARDS TECH

A1 11 0099631

6

—TA—

.U58

NO. 131

1981

NBS BUILDING SCIENCE SERIES 131

Laboratory Evaluation of

Nondestructive Methods to Measure

Moisture in Built-Up Roofing Systems

ENERGY

EFFICIENCf

U.S. DEPARTMENT OF COMMERCE • NATIONAL BUREAU OF STANDARDS
NATIONAL BUREAU OF STANDARDS

The National Bureau of Standards' was established by an act of Congress on March 3, 1901. The Bureau's overall goal is to strengthen and advance the Nation's science and technology

and facilitate their effective application for public benefit. To this end, the Bureau conducts

research and provides: (1) a basis for the Nation's physical measurement system, (2) scientific and technological services for industry and government, (3) a technical basis for equity in trade, and (4) technical services to promote public safety. The Bureau's technical work is per- formed by the National Measurement Laboratory, the National Engineering Laboratory, and

the Institute for Computer Sciences and Technology.

THE NATIONAL MEASUREMENT LABORATORY provides the national system of

physical and chemical and materials measurement; coordinates the system with measurement

systems of other nations and furnishes essential services leading to accurate and uniform

physical and chemical measurement througho^lt the Nation's scientific community, industry,

and commerce; conducts materials research leading to improved methods of measurement,

standards, and data on the properties of materials needed by industry, commerce, educational

institutions, and Government; provides advisory and research services to other Government

agencies; develops, produces, and distributes Standard Reference Materials; and provides

calibration services. The Laboratory consists of the following centers:

Absolute Physical Quantities^ — Radiation Research — Thermodynamics and

Molecular Science — Analytical Chemistry — Materials Science. THE NATIONAL ENGINEERING LABORATORY provides technology and technical ser- vices to the public and private sectors to address national needs and to solve national problems; conducts research in engineering and applied science in support of these efforts; builds and maintains competence in the necessary disciplines required to carry out this research and technical service; develops engineering data and measurement capabilities;

provides engineering measurement traceability services; develops test methods and proposes

engineering standards and code changes; develops and proposes new engineering practices;

and develops and improves mechanisms to transfer results of its research to the ultimate user. The Laboratory consists of the following centers:

Applied Mathematics — Electronics and Electrical Engineering^ — Mechanical

Engineering and Process Technology^ — Building Technology — Fire Research —

Consumer Product Technology — Field Methods.

THE INSTITUTE FOR COMPUTER SCIENCES AND TECHNOLOGY conducts

research and provides scientific and technical services to aid Federal agencies in the selection, acquisition, application, and use of computer technology to improve effectiveness and

economy in Government operations in accordance with Public Law 89-306 (40 U.S.C. 759), relevant Executive Orders, and other directives; carries out this mission by managing the Federal Information Processing Standards Program, developing Federal ADP standards

guidelines, and managing Federal participation in ADP voluntary standardization activities; provides scientific and technological advisory services and assistance to Federal agencies; and

provides the technical foundation for computer-related policies of the Federal Government.

The Institute consists of the following centers:

Programming Science and Technology — Computer Systems Engineering.

'Headquarters and Laboratories at Gaithersburg, MD, unless otherwise noted; mailing address Washington, DC 20234. 'Some divisions within the center are located at Boulder, CO 80303.
ATIONAL BURSAL! 09 BTANDAKUa

APR i 7 1981

NBS BUILDING SCIENCE SERIES 131 :^^Vi

Laboratory Evaluation of

Nondestructive Methods to Measure

Moisture in Built-Up Roofing Systems

Lawrence Knab

Robert Mathey

David Jenkins

Center for Building Technology

National Engineering Laboratory

National Bureau of Standards

Washington, DC 20234

Prepared for: Directorate of Engineering and Services

U.S. Air Force Washington, DC 20330

U.S. DEPARTMENT OF COMMERCE, Philip M. Klutznick, Secretary

Jordan J. Baruch, Assistant Secretary for Productivity, Technology and Innovation

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director

Issued January 1981
Library of Congress Catalog Card Number: 80-600189

National Bureau of Standards Building Science Series 131

Nat. Bur. Stand. (U.S.), BIdg. Sci. Ser. 131, 173 pages (Jan. 1981)

CODEN: BSSNBV

U.S. GOVERNMENT PRINTING OFFICE

WASHINGTON: 1981

For sale by the Superintendent of Documents, U.S. Government Printmg Office, Washington, DC 20402

Price $5.50

(Add 25 percent tor other than U.S. mailing)
ACKNOWLEDGMENT

This Investigation was sponsored by the Directorate of Engineering and

Services, U.S. Air Force, Washington, D.C. 20330. The authors wish to

acknowledge with thanks Mr. John F. Stanton and Mr. Michael Toriello of

the U.S. Air Force, for project coordination and their valuable technical

and administrative assistance.

Cover: An important consideration in roof maintenance is the detection

of moisture by nondestructive methods.

iii
TABLE OF CONTENTS

Page

ACKNOWLEDGMENT iii

LIST OF TABLES vi

LIST OF FIGURES vii

METRIC CONVERSION ix

ABSTRACT x EXECUTIVE SUI1MARY xi

1. INTRODUCTION 1

1 . 1 Background 1 1.2 Purpose and Scope 2

1.2.1 Purpose 2

1.2.2 Scope 2

2. SPECIMENS, DECKS, AND ENVIRONMENT 5

2.1 Specimens 5

2.2 Decks and Environment 7

3. MOISTURE INTRODUCTION, MEASUREMENT, AND GAIN 9

3.1 Moisture Introduction 9

3.2 Moisture Measurement 10

3.3 Rate of Moisture Gain 12

4. DATA ANALYSIS 13

4.1 Data Plotting and Curve Fitting 14

4.2 Sensitivity Criterion 16

4.3 Performance Characteristics and Indicators 18

5. ELECTRICAL CAPACITANCE METHODS 25

5.1 Mechanism of Operation 25

5.2 Instrument Description 26

5.3 Instrument Calibration 27

5.4 Test Results 28

5.5 Trends 28

5.5.1 Detection of Minimum Moisture Content (TVP) 28

5.5.2 Detection of Moisture Content Beyond the TVP 30

5.5.3 Shape of Data Sets and Their Fitted Curves 31

5.5.4 "Room Dry" Response 31

5.5.5 Additional Considerations 32

iv
TABLE OF CONTENTS (Continued)

Page

6. NUCLEAR BACKSCATTER METHOD 33

6.1 Mechanism of Operation 33

6.2 Instrument Description 34

6.3 Instrument Calibration 34

6.4 Test Results 35

6.5 Trends 35

6.5.1 Detection of Minimum Moisture Content (TVP) 36

6.5.2 Detection of Moisture Content Beyond the TVP 36

6.5.3 Shape of Data Sets and Their Fitted Curves 37

6.5.4 "Room Dry" Response 38

6.5.5 Additional Considerations 38

7. INFRARED THERMOGRAPHY METHOD 39

7.1 Mechanism of Operation 39

7.2 Instrument Description 40

7.3 Deck and Testing Environment 42

7.4 Test Results '^^ 7.5 Trends

7.5.1 Detection of Minimum Moisture Content (TVP) 44

7.5.2 Detection of Moisture Content Beyond the TVP 45

7.5.3 Shape of Data Sets and Their Fitted Curves 45

7.5.4 Additional Considerations 45

8. COMPARISON AND INTERPRETATION OF RESULTS AND TRENDS FOR

CAPACITANCE, NUCLEAR, AND INFRARED METHODS 47

8.1 Summary of Results ^8

8.2 Detection of Minimum Moisture Content (TVP) 49

8.3 Detection of Moisture Content Beyond the TVP 50

8.4 Shape of Data Sets and Their Fitted Curves 52

8.5 Interpretation of Effects and Trends as Related to

Performance Characteristics 52

8.6 Additional Considerations - "On the Roof" Uncertainity ., 53

9. REFERENCES 55

GLOSSARY OF TERMS 56

NOTATION 58

TABLES 1 THROUGH 15 60

FIGURES 1 THROUGH 26 76

APPENDIX A - COMPILATION AND ANALYSIS OF NDE DATA A-1

V
LIST OF TABLES

Table 1. Properties of Roofing System Components

Table 2. Composition by Thickness and Weight Per Unit Area of

Gravel-Surfaced Roofing Specimens

Table 3. Comparison of Membrane Weight Per Unit Area for "Standard" and

"Heavy" Asphalt Thicknesses

Table 4. "Room Dry" Responses (Rj)) for 18 Roofing Specimens for the

Capacitance and Nuclear Instruments with "Standard" and "Heavy'

Asphalt Thicknesses on Concrete and Steel Decks

Table 5. Summary of Specimens, Construction Variables, 3RSD, TVP , and S Values for the Capacitance and Nuclear Instruments

Table 6. Summary of Maximum Moisture Content, 3RSD, TVP and S Values for

Specimens Used with the Infrared Instrument

Table 7. Percentages of TVP Values Less than 10 percent, 20 percent, or "Not Attained" for Capacitance and Nuclear Instruments

Table 8. Percentages of TVP Values Less than 10 percent, 20 percent, or "Not Attained" and Percentages of S Values Less than 0.0 and 0.2

and SS less than -0.015 and 0.0 for the Infrared Instrument

Table 9. Percentages of S Values Less than 0.0 and 0.2 for Capacitance

and Nuclear Instruments

Table 10. Percentages of SS Values Less than -0.015 and 0.0 for

Capacitance and Nuclear Instruments

Table 11. Construction Variable Effects for Nuclear Instruments

Table 12. Summary of Percentages for All Insulations of TVP Less Than 10

percent, 20 percent, and "Not Attained"; S Less than 0.0 and

0.2; and SS Less than -0.015 and 0.0 for Capacitance, Nuclear,

and Infrared Instruments

Table 13. Instrument Effects for the Capacitance, Nuclear, and Infrared

Methods Rased on the TVP and S Indicators

Table 14. Instrument Effects for Capacitance and Nuclear Methods Based on

the TVP and S Indicators

Table 15. Percentages of TVP Values Less than 10 Percent, 20 Percent, and

"Not Attained" for "Standard" and "Heavy" Asphalt Thicknesses

and 1 in. and 2 in. Insulation Thicknesses

vi
LIST OF FIGURES

Figure 1. Fabrication of roofing specimens. Felts being applied to

Insulation board with hot asphalt.

Figure 2. Roofing specimen composition.

Figure 3. Typical gravel and smooth-surfaced specimens in testing position

for the capacitance and nuclear Instruments on the concrete

(right side) and steel (center) decks. Instruments Cl (right

side), C2 (center), and N2 (left side) are shown.

Figure 4. Roofing specimen, wooden supporting frame and the environmental

conditions used to Induce moisture.

Figure 5. Insulated wooden chambers used to induce moisture in tbe roofing

specimens.

Figure 6. Moisture gain in roofing specimens.

Figure 7. Adjusted NDE response versus moisture content for: perllte,

1 inch, steel deck, "standard" asphalt thickness, Instrument Nl

,

specimen 11.

Figure 8. Adjusted NDE response versus moisture content for: perllte,

1 Inch, concrete deck, "standard" asphalt thickness, Instrument Cl

,

specimen 62

Figure 9. Adjusted NDE response versus moisture content for: polyurethane

,

1 inch, steel deck, "standard" asphalt thickness. Instrument Cl,

specimen 41.

Figure 10. Adjusted NDE response versus moisture content for: glass fiber,

1 inch, steel deck, "heavy" asphalt thickness, instrument C2

,

specimen 52.

Figure 11. Adjusted NDE response versus moisture content for: flberboard,

1 inch, steel deck, "heavy" asphalt thickness, Instrument C2,

specimen 23.

Figure 12. Adjusted NDE response versus moisture content for: glass fiber,

1 inch, steel deck, "standard" asphalt thickness. Instrument C3

,

specimen 1

Figure 13. Adjusted NDE response versus moisture content for: polyurethane,

1 inch, concrete deck, "standard" asphalt thickness, instrument C3,

specimen 41

VI
LIST OF FIGURES (Continued)

Figure 14. Adjusted NDE response versus moisture content for: polystyrene,

2 inch, concrete deck, "heavy" asphalt thickness, Instrument Nl

,

specimen 38.

Figure 15. Adjusted NDE response versus moisture content for: perlite,

2 inch, concrete deck, "heavy" asphalt thickness, instrument N2,

specimen 18.

Figure 16. Adjusted NDE response versus moisture content for: polyurethane

,

1 inch, steel deck, "standard" asphalt thickness, instrument N2,

specimen 41

.

Figure 17. Schematic representation of Ry - Rp vs. Vp fitted curve showing

determination of S(TVP), S(MID), S(MAX).

Figure 18. Typical Relationships between Ry - Rp vs. Vp Fitted Curves and

their corresponding S vs. Vp curves.

Figure 19. Left: Instrument C3 (bottom of cart) and readout (top of cart).

Right: Instrument Nl

(Carts not used in laboratory testing.)

Figure 20. Electrical capacitance instrument response versus elasped time

for instrument Cl, range 4.

Figure 21. Electrical capacitance instrument response versus elapsed time

for instrument C2, "high" range.

Figure 22. Electrical capacitance instrument response versus elapsed time

for instrument C3, gravel setting.

Figure 23. Nuclear instrument response versus elapsed time for instrument Nl.

Figure 24. Nuclear instrument response versus elasped time for instrument N2,

Figure 25. Infrared thermography system.

Figure 26. Infrared thermography experimental apparatus.

viii
CONVERSION FACTORS TO METRIC (Sl) UNITS

Since the roofing industry generally uses conventional U.S. units, the

following table is provided for converting to metric units.

Physical Quantity

To Cnnvprt

From To Multiply By

j-iSngtn r t m

Area ft2 m2 9.29 X 10-2

Volume ft3 m3 2.83 X 10-2

Temperature Fahrenheit Celsius Tc = (Tf-32)/1.8

Temp. Diff. Fahrenheit Kelvin K = (ATf)/1.8

Density lbm/ft3 kg/m3 1.602 X 10+1

Mass per Unit Area lbm/ft2 kg/m2 4.88

ix
LABORATORY EVALUATION OF NONDESTRUCTIVE METHODS TO MEASURE MOISTURE

IN BUILT-UP ROOFING SYSTEMS

by

L. I. Knab,* R. G. Mathey,* and D. R. Jenkins**

ABSTRACT

This laboratory study investigated the reliability and accuracy of three

types of nondestructive evaluation (NDE) methods to quantitatively determine

the moisture content of the insulation in built-up roofing specimens. These

methods were electrical capacitance, nuclear backscatter, and infrared

thermography. Thirty-six roofing specimens, which consisted of five types

of rigid-board roof insulations, with attached bituminous built-up membranes

were tested over both concrete and steel decks. A wide range of moisture

contents was induced into the specimens by maintaining a constant water

vapor pressure difference across them.

Two performance characteristics of the NDE methods were evaluated:

(a) the minimum moisture content a method could detect, and (b) the relationship between NDE response and moisture content beyond the minimum

detectable moisture content. The two performance characteristics were assessed through normalization parameters defined in terms of the NDE

response and its scatter about a fitted curve. There were differences in

the performance characteristics, the magnitude of which depended on the

NDE method, the specimen composition, and the deck type used.

Keywords: Built-up roofing, electrical capacitance, infrared thermography,

insulation, moisture detection, moisture measurement, nondestructive evaluation, nondestructive testing, nuclear backscatter,

roofing systems.

Center for Building Technology, National Bureau of Standards, Washington,

D.C.

Professor of Engineering, University of Central Florida, Orlando, Florida,

on assignment to the National Bureau of Standards under provisions of the

Intergovernmental Personnel Act.

X
EXECUTIVE SUMMARY

I. BACKGROUND, PURPOSE, AND SCOPE

Moisture in insulated built-up roofing systems causes many premature roof

failures and unwanted energy losses. A promising approach for improving

the reliability of roof inspection and maintenance is through the use of

nondestructive evaluation (NDE) methods that can detect moisture in the

interior of roofing systems. Electrical capacitance, nuclear backscatter,

and infrared thermography are the most common commercially available NDE

methods used to detect moisture. Since considerable uncertainty existed

in the use of these methods, a comprehensive laboratory study was carried

out to determine the accuracy and reliability of these methods in order to

establish their moisture detection capabilities.

The purpose of this study was to conduct a controlled laboratory

investigation of the most common NDE methods to determine their ability to

quantitatively detect moisture in the insulation of built-up roofing systems.

The methods, number of instruments, and construction variables investigated

are shown in the following table.

Construction Variables

Insulation

NDE Method Surface

Asphalt

Thickness Type

Nominal

Thickness Deck

Electrical

Capacitance

(three instruments)

and

Nuclear Backscatter (two

instruments)

Gravel "Standard'

and

"Heavy"

Glass Fiber

Perlite

Fiberboard

Polystyrene

Polyurethane

2 in.

2 in.

2 in.

2 in.

in.

Concrete

and

Steel

Infrared

Thermography

(one instrument)

Gravel

and

Smooth

"Standard' Glass Fiber

Perlite

Polystyrene

I 2 in.

1, 2 in.

1. 2 in.

Steel

As noted in the table, there were significantly fewer tests conducted using

infrared thermography as compared to the other two methods. This is due to

differences in testing procedure requirements for the infrared method.

xi
Moisture was induced in thirty-six 2 x 2 ft. built-up roofing specimens by

maintaining a vapor pressure difference across them. Instrument readings

were taken on specimens with moisture content (percent by volume of

insulation) levels ranging from "room dry", corresponding to storage

conditions of about 70°F and 50 percent relative humidity, to a moisture

content of about 60 percent. Specimens containing moisture levels exceeding the "room dry" level (resulting from moisture induction) are denoted

"wet". For each specimen, instrument readings were taken at the "room

dry" condition and at many (about 10 to 20 or more) "wet" moisture content

levels. The readings were taken with the specimens resting on both concrete

and steel decks for the electrical capacitance and nuclear backscatter

methods and on steel deck only for the infrared method.

II. DATA ANALYSIS

The "adjusted NDE response," as measured by the "wet" minus the "room dry"

instrument readings versus moisture content, was analyzed. Quadratic

curves (least squares fit) were fitted to each adjusted NDE response versus moisture content data set; the residual standard deviation of the data about

the fitted curve was used to normalize the data set and its fitted curve.

Two performance characteristics were assessed for each instrument and

combination of construction variables (construction variable refers to

either specimen composition, i.e. surface, asphalt thickness, and insulation, or deck used - see previous table). The first performance characteristic, referred to as the "threshold moisture," was the minimum moisture

content a method could quantitatively detect. The "threshold moisture"

was defined as that moisture content for which the fitted curve for the

adjusted NDE response ("wet" minus "room dry") versus moisture content

exceeded the zero ("room dry") response by three residual standard deviation values. This definition is equivalent to normalizing the adjusted

NDE response by dividing by a scatter constant (three times the residual

standard deviation) thus enabling the comparison of "threshold moisture"

among the NDE methods.

The second performance characteristic was the moisture content beyond the

"threshold moisture" which a method could quantitatively detect. Moisture

content beyond the "threshold moisture" was measured by the sensitivity,

defined as the ratio of the slope of the fitted curve for the adjusted NDE

response versus moisture content to the residual standard deviation. Sensitivity values were determined only for moisture contents at and beyond

the "threshold moisture". Large (positive) sensitivity values indicate a correlated increase in the NDE response with an increase in moisture content. Sensitivity values near zero indicate poor correlation between the

NDE response and the moisture content. Negative sensitivity values indicate a decrease in response with an increase in moisture content. The

"threshold moisture" and sensitivity are called indicators, because they

are used to Indicate or measure the two performance characteristics. In

general, smaller "threshold moisture" contents and higher sensitivity

xii
values are indicative of better performance. The indicators were used

to measure instrument effects, that is, to assess differences between

instruments of a given type and between instrument types.

III. FINDINGS AND CONCLUSIONS

The findings and conclusions presented are based on a controlled laboratory

study which utilized the NDE methods and construction variables as shown in

the table in section I.

Minimum Detectable Moisture (Threshold Moisture Content)

All three methods were able to detect "threshold moisture." The three

methods detected "threshold moisture" values of less than 10 percent in

about 40 to 60 percent of the cases; "threshold moisture" values less than

20 percent were detected in 55 to 90 percent of the cases (table 12).

In general, the response of the nuclear backscatter instruments gave as low

or lower "threshold moisture" contents as compared to the electrical capacit' ance and infrared thermography methods (table 13). In some cases, the electrical capacitance Instruments could not detect a "threshold moisture"

value up to the maximum moisture content induced in the specimen. Infrared

thermography detected a "threshold moisture" for eight of the nine specimens

tested. In all cases, the nuclear instruments were able to detect the

"threshold moisture" content. These differences in detecting "threshold

moisture" among the NDE methods were not considered to be significant.

Detection of Moisture Beyond the Threshold Moisture

In general, the nuclear backscatter and infrared thermography methods had

sensitivity values which considerably exceeded zero and which exceeded the

corresponding sensitivity values for the capacitance method. Depending

on the capacitance instrument, from 11 to 22 percent of the sensitivity

values were negative, indicating a decrease in the adjusted NDE response

as the moisture content increased.

For specimens containing perlite and fiberboard insulations, many of the

adjusted NDE response versus moisture content data sets (figures A13 to

A24, appendix A) for the capacitance method showed the following trend:

the adjusted NDE responses rose sharply at moisture contents of about 10

percent or less and then leveled off or decreased with increasing moisture.

Thus, for these cases, it was not possible to distinguish between relatively

low moisture contents and larger moisture contents.

Many of the adjusted NDE response versus moisture content data sets and

their fitted curves tended to be concave downward for the capacitance method

(figures Al through A36, appendix A). This is in contrast to an almost

linear (that is, slightly concave downward), linear, or concave upward trend

xiii
for the nuclear (figures A37 through A60) and infrared (figures A61 through

A69) methods. These trends are supported by the higher percentages (11 to

22 percent) of negative sensitivity values at and beyond the threshold

moisture content for the capacitance method as compared to all positive

sensitivity values for the nuclear and infrared methods.

It is concluded that the nuclear backscatter method was able to determine

the moisture content beyond the "threshold moisture"more reliably (always

having positive sensitivity values) and, for most construction variable

combinations (table 14), more accurately (larger sensitivity values) than

the electrical capacitance method.

Based on the limited infrared thermography data, the following conclusions

are drawn. As compared to electrical capacitance, the infrared thermography

method was able to determine the moisture content beyond the "threshold

moisture" more reliably (always having positive sensitivity values) and

more accurately (larger sensitivity values, table 13) than for the electrical capacitance method. It is concluded that no significant difference

existed between the ability of the nuclear backscatter and infrared thermography methods to detect moisture beyond the "threshold moisture" content,

because the sensitivity values for both methods were positive and about

the same in magnitude (table 13).

IV. FACTORS AFFECTING NDE FIELD SURVEYS

This report deals solely with a laboratory evaluation of three commonly used

NDE methods to detect moisture in built-up roofing systems. The laboratory

study was conducted under controlled conditions and did not consider all

variables or factors which may be encountered in actual field surveys.

Factors which were not investigated in this study and therefore not discussed

in the report include:

o moisture distribution through the thickness of the roofing system

o layers of water either on the surface or within the roofing system

o surface moisture

o volume of roofing system affecting instrument response

o point or grid measurements (capacitance and nuclear methods) as compared to full-field measurements (infrared method)

o gravel thickness

o distance between Instrument and moisture (capacitance and nuclear

methods)

o anything that affects surface temperature (infrared method)

These factors along with others which affect the response of the NDE methods

are discussed in detail in reference [3]. This reference recommends that non- destructive evaluation should always be accompanied by visual inspection of

the roof and by the taking of cores to verify moisture contents. In addition

xiv
to the factors listed above, the following must also be considered in select

an NDE method:

o Cost of equipment, personnel, and data analysis.

o Skill of personnel required to operate equipment and to collect and

analyze data.

o Knowledge of the roofing system and the effects of the construction

and environmental variables on the NDE method response.

o Purpose of moisture survey (routine maintenance, re-roofing

evaluation, etc.).

o Reliability and quality required in survey results.

o Combination of more than one NDE methods.

It has been pointed out that the selection of an NDE method to measure the

moisture in built-up roofing systems depends on many factors. Thus, the

information on the reliability and accuracy of the NDE methods for the roof

construction variables investigated in this study is an important

consideration in selecting an NDE method.

XV
Facing Page: Moisture can be introduced in the insulation

of a roofing system during construction.

xvi
1 . INTRODUCTION

1.1 BACKGROUND

Moisture in insulated built-up roofing systems causes many premature roof

failures. For example, moisture in the insulation of roofs will reduce the

useful life of a membrane by causing premature failures, such as blistering,
splitting, wrinkling, and deterioration of the membrane [1]*. Also moisture

can significantly increase the thermal conductance [2] of a roof, causing

unwanted energy losses.

Early detection of moisture in roofs is required if premature deterioration

is to be prevented. The traditional Inspection methods for moisture are

slow, costly, require cutting samples from the roof, and seldom provide

conclusive results.

A promising approach for improving the reliability of inspection and

maintenance procedures is through the use of nondestructive evaluation

(NDE) methods that can detect moisture in the interior of roofing systems.

There are currently a number of promising, commercially available, NDE

methods being used to detect moisture in roofing systems. They are primarily the nuclear backscatter, electrical capacitance, and Infrared thermography methods. These methods detect moisture by Indirect means. They can

be used to estimate the moisture content with an accuracy which appears to

depend on the equipment characteristics, composition of the roof, environmental conditions, operator skill, and several other factors [3]. A comprehensive study was carried out to compare the accuracy and reliability of

these methods so that their proper role in roofing inspection, maintenance,

and repair could be established.

1.2. PURPOSE AND SCOPE

1.2.1 Purpose

The purpose was to conduct a controlled laboratory study to investigate

NDE methods for:

o their ability to quantitatively detect a minimum moisture content

(threshold moisture content, TVP)

o their ability to quantitatively detect moisture beyond the threshold

moisture content (change in NDE response per change in moisture

content )

.

1.2.2 Scope

Two nuclear instruments (Nl and N2 )

, three electrical capacitance

Instruments (Cl, C2 , and C3), and one infrared thermography Instrument were

investigated. The Instruments or services using the Instruments are commercially available.

Thirty-six built-up roofing (BUR) specimens, measuring 2 x 2 ft. and

consisting of five different Insulations, in one and two in. nominal

Numbers in brackets refer to references at the end of this report.

2
thicknesses, were used to evaltiate t>^e NDE methods on hoth concrete and

stoel decl'S. A,ll the specimens used wltVi the capacitance and nuclear

Instruments were gravel-surfaced. Since there was essentially no difference in infrared instrument response hetween conparrible gravel and smoothsurfaced specimens, most of the specimens used with the infrared instrument were smooth-surfaced. Two interply asphalt thicknesses were investi.s"5ated.

The gravel surfacing weight per unit area was, in general, greater for the

thicker asphalt. Moisture was induced in the roofing specimens by Imposing

a constant vapor pressure difference across the specimens. The response

data for the NDE methods were taken over a wide range of moisture contents,

varying from near zero to about 60 percent by volume for some insulation

types.

3
Facing Page: Roofing specimen fabrication - application of asphalt

flood coat and gravel surfacing

,

4
2. SPECIMENS, DECKS, AND ENVIROWtENT

2.1 SPECI^ffiNS

NDE responses (readings) were taken on "room dry" roofing insulation boards

with attached BUR merabranes. The thirty-six "room dry" specimens were

stored at room conditions at approximately 70°F and 50 percent relative

humidity (RH). The moisture contents of the "room dry" insulation boards

and roofing felts used to constrvict the specimens were determined

gravimetrically after oven drying. After obtaining the NDE responses for

5
the "room dry" specimens, moisture was induced into the specimens, and NDE

responses were taken on the "wet" specimens. All specimens were nominally

2 by 2 ft. square. Five types of rigid board roof insulations, in 1 and 2 in. nominal thicknesses, were included in the study; they were glass

fiber, perlite board, fiberboard, expanded polystyrene, and foamed polyurethane. The BUR specimens were fabricated by a roofing contractor under

the supervision of National Bureau of Standards' personnel (figure 1). The

BUR membranes consisted of four plies of type 15 asphalt saturated, organic

felts (Type I - ASTM D 226-77 [4]). The felts were applied to the insulation boards in sandwich fashion by application of hot, Type III asphalt (ASTJl

D 312-77 [5]). Both gravel and smooth-surfaced specimens were included.

The rounded gravel, which was embedded in a hot asphalt floodcoat, was a 3/4 in. maximum size. Figure 2 shows a schematic of the composition of a roofing specimen; figure 3 shows typical gravel and smooth-surfaced

specimens

.

Table 1 gives the average measured properties for the insulation, felt, and

asphalt used in the fabrication of the test specimens. The glass fiber

board had an asphaltic facing sheet over which the BUR membrane was applied.

In this study, the facing was considered as part of the membrane. The

polyurethane board originally had asphaltic facing sheets on both sides.

In order to increase the rate of moisture introduction, the asphaltic facing

sheets were removed from both sides with a band saw to provide the required

1 and 2 in. thicknesses. The thickness of the polyurethane boards before

cutting was 2.25 in. for the 1 in. specimens and 3.25 in. for the 2 in.

specimens. The batch from which the 1 in. thick specimens were cut was probably different from the batch from which the 2 in. specimens were cut.

This is supported by the difference in density (table 1) and visual difference; i.e. the 2 in. thick boards appeared less uniform in texture than

the 1 in. thick boards.

Table 2 presents the gravel-surfaced specimens for which "room dry" and

subsequent "wet" NDF tests were performed. The specimens were taken apart

and the following thicknesses were measured: total specimen thickness,

combined membrane and gravel thickness, and the membrane thickness. The

table gives average values for total specimen thickness, the membrane and

gravel thicknesses, and the membrane and gravel weight per unit area. The

insulation thickness shown was taken as the difference between the measured

total specimen thickness and the combined membrane and gravel thickness.

The gravel thickness was taken as the difference between the measured com- bined membrane and gravel thickness and the membrane thickness. The weight

per unit area of the membrane included the weight of the floodcoat, including the floodcoat which adhered to the gravel. The weight of the floodcoat

v7hich adhered to the gravel was determined by weighing the gravel before

and after it was washed in a solvent.

/Table 2 also identifies the smooth-surfaced BUR specimens for which

"room dry" and subsequent "wet" NDF tests were performed. The table gives

average measured values for total specimen thickness and membrane thickness

6
and weight per unit area for specimens which had been taken apart. The

insulation thickness was taken as the difference between the total specimen

and the membrane thicknesses.

Thickness and weight per unit area measurements were performed after the

"wet" NDE tests had been completed. The values of the individual membrane

thicknesses in table 2 are the averages of nine measurements. In some

cases, as noted in table 2, the total thickness of the specimen could not

be measured because the insulation had deformed. Therefore, the total

specimen thickness had to be estimated using the membrane and gravel thick- nesses (table 2) and the insulation thickness given in table 1. Some melting and consequent reduction in the thickness of the polystyrene insulation

occurred during application of the hot asphalt and roofing felts. When

handling the gravel-surfaced specimens, some loose gravel fell off. As a result, this lost gravel was not included in the thickness and weight per

unit area measurements given in table 2.

As table 2 indicates, there was considerable variability in the data for

membrane thickness and weight per unit area. Table 3 presents the data for

the membrane weight per unit area for specimens tested using the capacitance

and nuclear methods. Because these methods may be influenced by interply

asphalt thickness, it was necessary to introduce asphalt thickness as a variable ("standard" and "heavy"). The membrane weight per unit area data were judged to be more consistent and reliable than the membrane thickness

measurements; hence weight per unit area data are used to compare the "standard" and "heavy" asphalt thickness levels in table 3. It is apparent that

for specimens containing different insulations there was a considerable

range in the weight per unit area values for the "standard" and "heavy"

asphalt thicknesses. It can be seen, however, for 1 and 2 in. insulation

thicknesses, that the weight per unit area for the "heavy" asphalt exceeded

the "standard" for each type of insulation. Table 2 also presents the

membrane weight per unit area values for specimens (nos. 51, 61, 113, 141,

143, 145, 733, 751, 155) with "standard" asphalt thickness and tested using

the infrared method. The information in tables 2 and 3 needs to be con- sulted when determining the effect of "standard" as compared to "heavy"

asphalt thickness on the NDE response as given later in this report. It is

noted that the gravel surfacing weight per unit area was, in general,

greater for the "heavy" asphalt thickness.

2.2 DECKS AND ENVIRONMENT

For the nuclear and capacitance instruments, the specimens were placed on 2.5 by 2.5 ft. square decks. Both concrete and steel decks were used; the

decks were elevated approximately two feet above a 6 ft. thick concretesteel structural test floor. After the specimens vjere centered on the

decks, the NDE readings were taken at ambient conditions of approximately

70°F and 50 percent RH. Figure 3 shows NDE readings being taken on the

specimen-deck assemblages. For all specimens placed on the steel deck and

for "room dry" and "wet" specimens containing polystyrene and also

7
polyurethane insulations, a 1 in. "room dry" perlite board was placed

between the specimen and the deck. To prevent moisture from being absorbed

into the 1 in. perlite board, a 3 mil polyethylene sheet was used between

the specimen insulation surface and the 1 in. perlite board. The reason

for using the 1 in. perlite board was that in current construction practice,

composite boards using foam plastic and mineral board are used for reasons

of fire safety.

Due to differences in the testing procedure requirements for the infrared

method, a special test setup, using a steel deck only, was used with con- trolled environmental conditions. The details of the infrared method are presented in chapter 7.

The concrete deck was a 5 in. thick structural concrete slab with no. 4

steel reinforcing bars in one direction spaced 12 in. on the top and no. 3

bars spaced 12 in. in both directions on the bottom. After curing, the

concrete deck was sealed with a two component epoxy paint to insure that

the moisture content in the concrete deck did not change during the testing

program.

A fluted steel deck (light, 22 gage) was used.

Facing Page: Ponded t/ater on roof surfaces may lead to moisture

introduction in the roofing system.

8
3. MOISTURE INTRODUCTION, MEASUREMENT, AND GAIN

3.1 MOISTURE INTRODUCTION

The NDE tests were performed on specimens containing a wide range of

moisture contents. Moisture was induced in the specimens by controlling

temperature and relative humidity conditions on each side of the specimens

as indicated in figure 4, Specimens were placed on the top of insulated

wooden chambers, as shown in figures 4 and 5. The inside of each of the

two large insulated chambers, 8 x 16 ft. in area, was maintained at 100°F

9
(+7°?) and 100 percent RH by means of four pools (each about 25 ft^)

containing heated water. The two insulated chambers were in an environmental laboratory which was maintained at 50°F (+4°F) and 25 percent (+5

percent) RH. Thus, the insulation (bottom) side of the specimens was subjected to 100°F and 100 percent RH while the membrane (top) side of the

specimens was subjected to 50°F and 25 percent RH. The calculated vapor

pressure difference was 1.84 in. of Hg for the environmental conditions

under which the specimens were exposed. The intent of using this relatively

large vapor pressure difference was to induce moisture into the specimens

at a rapid rate; usually, much lower vapor pressure differences exist

under actual field environmental conditions.

A wooden frame, approximately 2x2 ft., with a continuous wooden ledge at

the bottom, was used to support the individual specimens (figure 4). The

ledge provided about a 1/2 in. width of support at the bottom on all four

specimen edges. When additional support was needed because of deteroriation due to moisture, aluminum angle, 1/2 in. in width, spanned the center

of the wooden frame in both directions. To promote one-dimensional moisture migration, the edges of the specimens for all Insulations except the

perlite boards were sealed with an impervious, vinyl, vapor- barrier paint.

A wax was used to seal the edges of the perlite board specimens. Due to

handling, some specimen edge seals cracked or fell off during the moisture

introduction and testing of the specimens.

In an attempt to determine the moisture distribution through the insulation

thickness, 0.91 in. diameter cores were taken from the insulation of some

of the specimens. These cores v/ere generally taken as far away from the

center of the specimens as possible so as to not affect the NDE instrument

responses. The coring procedures and some coring data related to thermal

conductance are presented in reference [2 ] . The coring data for this NDE

study are considered preliminary and, in general, cores were not taken for

most moisture contents corresponding to NDE testing. Thus the coring data are not presented.

3.2 MOISTURE MEASURETTENT

Before the specimens were placed into chambers in the environmental room,

they were weighed ("room dry" weight) and measured. When the specimens

were removed from the chambers, the time was recorded and the specimens

weighed ("out" weight). With the exception of the specimens containing

glass fiber insulation, the surface of the insulation was wiped with paper

towels to remove any free or condensed surface water prior to weighing.

Distinct areas of visible free water, particularly for higher moisture contents, were observed on the surface of the warm side of the glass fiber

insulation. It appeared that the lateral distribution of moisture in

these specimens varied considerably. At some times during handling, particularly at higher moisture contents, considerable free water was lost from

these specimens.

10
Since some gravel fell fron the specimens during handling (removal and

return to moisture chamhers and during testing), the following procedure

was used to determine the moisture weight gain for all gravel-surfaced

specimens

moisture gain = "out" weight - "room dry" weight (1) + estimated cumulative gravel weight loss

where the last term (estimated cumulative gravel weight loss) was determined by summing the gravel weight loss during each

previous handling.

The gravel weight loss per handling v^fas estimated for all specimens as follows. Since the "room dry" moisture contents were relatively low

(table 1), the total gravel loss (for all handlings) was measured for 19

of the 30 gravel-surfaced specimens (table 2) as the difference between

the "room dry" weight and the oven dried weight after all testing was

completed. The gravel weight loss per handling v/as determined for these

19 specimens by dividing the total gravel loss by the number of handlings.

The average total gravel weight loss for each of the 19 specimens \7as

about 1.6 lb. and the average gravel loss per handling v/as about 0.08 lb.

The gravel weight loss per handling for 7 of the 30 specimens (nos. 11,

16, 18, 21, 23, 26, and 29-table 2) was estimated as 0.08 lb., with the

corresponding estimated total gravel weight losses ranging from 0.62 to

1.5 lb. The weight loss per handling for specimen Al was taken as 0.05 lb.

and was based on an assumed total gravel loss of 1.6 lb., since specimen 41 was handled more times than most of the other specimens.

The gravel weight loss per handling for the three specimens (nos. 51, 61,

113) used for the infrared measurements v/as assumed to be insignificant.

These specimens vrere tested under different conditions than for the capacitance and nuclear measurem.ents and were handled a fev/er number of times.

The gravel adjustment procedures applied were judged to be reasonable,

since in general it was observed that during testing only a small quantity

of gravel was lost during each handling.

The values of moisture gain for t>ie gravel-surfaced specimens are approximate but believed to be reasonable estimates of the moisture gain.

The uncertainty in the approximate moisture gain values is most likely

greater for the lower moisture content values.

For smooth-sufaced specimens, the difference in weight betvjeen the "out"

weight and "room dry" weights was taken as the moisture gain.

11
3.3 RATE OF MOISTURE GAIN

The rate of moisture gain varied depending on the type and thickness of

insulation in the roofing specimens. The exposure time ranged from about

10 to 100 days, depending on the type of insulation. There was interruption in the introduction of moisture in some specimens because the desired

moisture contents had been reached and because of maintenance of the

laboratory facilities. Therefore, some specimens were stored in plastic

bags at room temperature before testing.

Figure 6, taken from the companion thermal conductance study [2], shows

the insulation moisture content, Vp , in terms of the elapsed time in the

chambers for ten smooth-surfaced specimens which were fabricated from the same materials used in this study. Specimen numbers given in figure 6 pertain to the thermal conductance study [2j^ and are not found in the tables

in this report. The moisture content, Vp , in the specimen insulation is

expressed as the percent by volume of water in the insulation; Vp was

based on the average moisture gain for the entire specimen. The volume of

insulation was determined from the insulation thickness (table 2) and the

actual overall specimen dimensions (about 2 x 2 ft.). The volume of water

was determined from the weight gain of the specimen (62.4 lb. = 1 ft-^).

Moisture gain plots for gravel-surfaced specimens were not included since

some gravel fell from the specimens during handling. It is judged, however,

that the moisture gain characteristics for the smooth and gravel-surfaced

specimens were similar, since both surface types were subjected to the same vapor pressure difference.

Near or at the maximum moisture content, the insulation of some of the

specimens, particularly perlite and fiberboard, cracked, delaminated, or fell apart. For specimen 16, which contained 2 in. thick perlite insulation, delamination of the specimen occurred at a moisture content of about

18 percent. The specimen was adhered together using a hot glue and testing

continued until the maximum moisture content was reached (about 25 percent).

The corners of specimens containing 1 in. polyurethane insulation (nos. 41

and 43) warped (turned up, away from deck surface) as much as three inches

at their higher moisture content values. Since specimens containing 2 in.

polyurethane took on very little moisture, they were not included in the

analyses in this report.

* V = (, Volume of moisture ^ 100

^ Volume of insulation

Facing Page: Asphalt flood coat and mineral aggregate surfacing serves as

a protective barrier to resist weathering of the membrane

and moisture intrusion into the roofing system.

12
4. DATA ANALYSIS

This chapter presents the definitions and techniques used to present and

analyze the NDE data. Included are the procedures used for data plotting,

curve fitting, and outlier identification, and the definitions of the

sensitivity criterion, performance characteristics, and indicators used to

measure the performance of the NDE methods.

13
4.1 DATA PLOTTING AND CURVE FITTING

The adjusted NDE response is defined as the "wet" instrument response, Ry,

minus the "room dry" instrument response, Rp. The terms "room dry" and "wet"

refer to roofing specimens at "room dry" conditions (table 1) and those

having induced moisture in the insulation, respectively. The adjusted NDE

response versus moisture content, Vp, data sets are plotted in figures

Al through A36 in appendix A for the three capacitance instruments; figures

A37 through A60 for the two nuclear instruments; and figures A61 through A69

for the infrared instrument. The "KEY" on the right side of each figure

identifies the symbol (e.g. "TRI" = triangle, "DIAH" = diamond) with each

specimen number (see figure Al).

To assist the reader to follow the data more easily in figures Al through

A60, the data points were connected by straight lines. For about 30 percent

of the total number of moisture content values at which Ry readings were

taken, either two or four repeated Ry readings were taken. These multiple

Ry readings did not exhibit as much scatter as expected. In many cases the

standard deviation of these readings was considerably less than the corre- sponding residual standard deviation (eqn. 3) resulting from the curve fitting procedures. It was concluded that the scatter in these readings

included only part of the variability normally associated with replicate

readings, primarily because the specimen was not repositioned between readings and the times at which the readings were taken were usually very close

together. For these reasons the multiple readings were not believed to be

statistically independent of one another, and hence not true replicates.

Thus it was not reasonable to treat each mutliple reading separately as though it were a truly independent data point. Hence, these multiple Ry

readings were averaged and that average was equally weighted with the

single Ry values taken at other Vp values.

Table 4 provides "room dry" (Rf)) responses for 18 of the 27 roofing

specimens for the capacitance and nuclear methods; these responses are discussed in chapters 5 and 6,

Table 5 gives the construction variables for each specimen, including the

deck type, insulation type and nominal thickness, and asphalt thickness.

To compare the effects of the construction variables, one scale for the

adjusted NDE response was used with each instrument (figures Al through A69),

Initially, linear, quadratic, and cubic polynomial forms were arbitrarily

selected and fitted to the NDE instrument response versus moisture content

data sets. This initial study showed that, in many cases, the quadratic

form represented a significant improvement in fit as compared to the

linear form. The cubic form, however, was judged not to represent a significant improvement in fit as compared to the quadratic form. Thus the

following quadratic form, though somewhat arbitrary, was chosen as best

suited for the variety of shapes of NDE data sets observed.

14
2

^est = (^W ~ KD)est = ao + ai Vp + a2 Vp (2)

where:

^est ~ estimated Ry - Rp response

Ry = "wet" NDE reading (at a given "wet" Vp value)

Rp = "room dry" NDE reading (at the "room dry" Vp value)

(Ry - RD)est ~ estimated Ry - Rp response

7p = moisture content, percent by volume of insulation

ao, aj, a2 = least squares coefficients

Based on eqn. 2, the residual standard deviation, RSD was calculated by:

1/2

RSD =

n 2

Z (^obs " "^est^

i=l

n-P

(3)

where:

n = total number of Ry - Rp observations

^obs = observed R^ - R^ response, including 0 (i.e. R^ = R^)

^est = estimated R^ - R^ response (eqn. 2)

P = number of parameters estimated; for a quadratic form,

P = 3.

The RSD value reflects the inherent scatter in the data as well as the

uncertainty in the model (quadratic form) used to fit the data. The relatively few data points which were separated from their fitted curve by

more than three RSD values were treated as outliers. The outliers are labelled in figures Al through A60 but were not included in any analysis of

the data. There were more outliers for specimens containing polystyrene

insulation than for the other insulation types.

An example of the procedure used to analyze the Ry - R]) (adjusted NDE

response) vs. Vp data sets and obtain fitted curves is as follows. The

response of instrument Nl (nuclear instrument, discussed in chapter 6) on specimen 11 (1 in. thick perlite insulation with "standard" asphalt thickness) on a steel deck was chosen. First the "wet" responses, Ry, were

obtained by adjusting the responses for time effects (eqn. 10, chapter 6),

(This adjustment was required only on instrument Nl.) Then the "room dry"

15
response, Rp, was substracted from each Ry value. In this case Rj) was equal

to 193 counts. As prevluously discussed, for a given Vp value, if there

were multiple Ry responses, the multiple Ry responses were averaged so as

to be weighted equally with single Ry responses taken at other Vp values.

The Ry - Rj) vs. Vp data set for the case being illustrated is shown in

figure A46, appendix A. A best fit quadratic curve (eqn. 2) was then

fitted to the Ry - Rp vs. Vp data set as shown in figure 7. Once the fit was made, the residual standard deviation value, RSD, was computed (eqn. 3).

A variety of shapes and scatter patterns occurred for the Ry - Rp vs. Vp

data sets for the three NDE methods studied. Examples of fitted quadratic

curves are shown in figures 7 through 16 and figures A61 through A69,

appendix A. The intent of these figures is to show the variety of shapes

and scatter patterns which were observed. The reader is referred to

chapters 5 through 8 for an assessment of the various NDE methods.

Tables Al through A5, All through A15, and A21 in appendix A present a summary of the Ry - Rp vs. Vp data for the capacitance, nuclear, and infrared instruments respectively. The tables show the Ry - Rp response at Vp

values of 0, 10, 20, 30, 40, 50, and 60 percent based on a best fit quadratic curve fitted to the points of each Ry - Rp vs. Vp data set. Also shown

in the tables are values of "3RSD", that is, 3 times the residual standard

deviation (RSD) and the threshold moisture content (TVP) for each fitted

curve. The values of 3RSD were used to determine the threshold moisture

content, which is discussed in the section 4.3.

4.2 SENSITIVITY CRITERION

A thorough search and study was made on how to define a sensitivity

criterion to compare the variety of NDE methods used in this study.

There are many possible ways to define sensitivity including normalizing

the response by the local or maximum response. For example, a recent

comparative study [6] of nuclear moisture and density instruments, defined

sensitivity, S, as:

Ar

S = ^

(4)

Aw

w

where:

Ar/r = relative change in count rate

Aw/w = relative change in moisture

In the current study, the three NDE methods investigated and analyzed had

vastly different fitted curve shapes (Ry - Rp vs. Vp) and also different

associated scatter (see figures Al through A69, appendix A). The three

instrument types operated with completely different mechanisms and widely

16
different Ry - Rp response scales. For example, the minimum and maximum

Ry - Rd scale values used for the different instruments were:

w u

Minimum Maximum

Instrument Scale Value Scale Value

Capacitance

CI 0 100

C2 0 200

C3 0 8

Nuclear

Nl 0 80

N2 0 300

Infrared 0 0.2

In addition, a variety of construction variables, including two deck types,

five insulation types, two insulation thicknesses and two asphalt thick- nesses were investigated. Because of the many variables and the wide ranges

of the variables involved, it was necessary to normalize the Ry - Rq data

in order to assess the performance charcteristics (discussed in section 4.3)

within and among instrument types.

Due to the large difference in the shape and scatter patterns of the data

sets, and the many variables and wide ranges of the variables, it was decided that the normalization process would be based on the fitted curve

and that it would include a measure of scatter of the Ry - Rp vs. Vp data

set about its fitted curve. That is, two fitted curves which were very

similar as normalized by a definition such as eqn. 4, but had significantly

different scatter (residual standard deviation), needed to be distinguished,

since the associated uncertainty in the response would be larger for the curve with more scatter. A sensitivity criterion, such as that given by

eqn. 4, though perhaps suitable for a single method (nuclear) was not deemed

appropriate for the current study.

Mandel and Stiehler [7] present an approach to quantitatively determine the

sensitivity of a test method. They define the sensitivity, S, as the absolute value of the ratio of the slope, m, of the response curve to the

standard deviation, s, i.e.:

S = |m|/s (5)

This definition of sensitivity (eqn. 5) was chosen because it is a rational

definition which incorporates scatter and was believed to be the best suited

17
for quantitatively comparing the results of the NDE methods. Their

criterion has also been used for other applications [8, 9].

In this report, the slope was taken to be the change in the adjusted NDE

response (A(Ry - R^^est^ predicted from the fitted curve (eqn. 2) per

unit change in moisture content (AVp). The standard deviation in eqn. 5 was approximated by the residual standard deviation (RSD, eqn. 3) of the

Ry - Rp vs. Vp data set about its fitted curve. Ideally, values of the

standard deviation at each Vp value should have been used to define the

sensitivity; however, data were not available to do this.

The sensitivity, S, can then be written as:

A(R„-Rt.)„^^

S = ( W_D_est)/^sj3

AVp

Use of the sensitivity, then, implies normalizing the Ry - Rj) data by

dividing by RSD. That is, the sensitivity can be written as:

A(Rw-RD)est

S = RSD (7)

AVp

From eqn. 7 it can be seen that the sensitivity is the slope of the

(Ry-RD)gs|./RSD vs. Vp curve.

Use of the sensitivity to assess the performance of the NDE methods is

discussed in the next section.

4.3 PERFORMANCE CHARACTERISTICS AND INDICATORS

Two performance characteristics were chosen to evaluate the NDE methods.

The following performance characteristics were determined for each Ry - Rp

vs. Vp data set and corresponding fitted curve:

o the minimum amount of moisture, called the threshold moisture

content (TVP), that an instrument could quanitatively detect

for a specified reliability; and

o ability of the instrument to quantitatively detect moisture

beyond the TVP value.

The first performance characteristic, TVP, was defined to be that Vp value

at which the fitted curve [ (Ry. - Ro^est* eqn. 2] deviated from (exceeded)

the zero ("room dry") response by 3 RSD values. This definition is equivalent to normalizing the Ry - Rj) responses by dividing them by a multiple

of the scatter (3RSD), thus permitting the comparison of threshold moisture

18
values within and among the NDE methods. The multiple of 3, which was chosen for analysis purposes and which was somewhat arbitrary, was found to

be a reasonable condition and requirement for computing and comparing

threshold moisture contents in a consistent manner. It was found that the

intercept for the (Ry - RD)est fitted curve (obtained by setting Vp = 0 in

eqn. 2) in most cases differed somewhat from zero, and in some cases, differed significantly from zero (for example, see figures 7 through 16 and

tables A1-A5, A11-A15, A21, appendix A). It was decided to measure the

deviation of 3 RSD values (used in TVP definition) from zero and not from

the intercept of the fitted curve. The reason for choosing zero was that

the zero value of Ry - Rp was measured and hence was known with certainty.

Also the uncertainty in the Vp values caused by gravel loss during testing

probably increased the uncertainty of the Ry ~ Rd vs. Vp points near the

origin (see section 3.2). The TVP values were obtained by setting the

right hand side of eqn. 2 equal to 3RSD and solving for Vp . An example

of the TVP determination is illustrated in figure 7, where 3RSD was equal

to 8.45 (table 5) and the resultant TVP value was 7.11 percent. If the

ordinate of the fitted curve (eqn. 2) never equalled or exceeded 3RSD up

to the maximum moisture content in the specimen, no TVP existed. This

condition was referred to as: "TVP not attained". The TVP values for the

capacitance and nuclear instruments are given in table 5. Also listed in

table 5 is the maximum Vp value attained in each specimen and three times

the RSD value (3RSD). Table 6 presents information similar to that in

table 5 for the infrared instrument.

The threshold moisture content is called an indicator because it is used as

a measure of the ability (or performance) of a method to detect a minimum

moisture content. In general, smaller TVP values are indicative of better

performance.

Table 7 presents, for the capacitance and nuclear instruments, a summary of

the percentage of the TVP values in table 5 which were:

o less than 10 percent

o less than 20 percent

o not attained up to the maximum Vp of the specimen (called "TVP

not attained")

For example, the top left entry of "11" in table 7 means that 2 of the 18

(11 percent) TVP values for instrument Cl for specimens containing glass

fiber insulation in table 5 were less than 10 percent. The entries given

in table 7 are for the three capacitance and two nuclear instruments and

for each of the five insulation types tested. Table 7 also presents entries

for the instruments for all insulations combined. Information similar to

that in table 7 is shown in table 8 for the infrared instrument. The

entries in tables 7 and 8 for "TVP less than 10 percent" and "TVP less than

19
20 percent" are based on the total number of tests performed, including

those tests for which a TVP value was not attained.

The TVP values for which percentages are summarized in tables 7 and 8 (less

than 10 percent , less than 20 percent , or

" not attained ") were chosen to

emphasize trends which are discussed in chapters 5, 6, 7, and 8.

The second performance characteristic (ability to detect moisture beyond

the TVP) was measured by the following indicators:

o the value of the sensitivity, S, (eqn. 6) at and beyond the

TVP value.

o the value of the slope, SS, of the S vs. Vp curve at and beyond

the TVP value.

The sensitivity values, S, were determined from eqn. 6, based on the

secant slope, for Vp ranges, called "moisture content ranges" of 0 to 10,

10 to 20, 20 to 30, 30 to 40, 40 to 50, and 50 to 60 percent as follows:

_ (Rw at Vp) - (R^ at [Vp - 10])

10 RSD

where:

(Ry at Vp) = instrument response at the higher moisture content

(i.e., for example 30 percent) in a given "moisture

content range" (i.e., for example 20 to 30 percent),

(Ry at [Vp - 10]) = instrument response at the lower moisture content

(i.e., for example 20 percent) in a given "moisture

content range", (i.e., for example 20 to 30 percent)

RSD = residual standard deviation of the fitted curve.

Values of S were determined only for moisture content ranges which either

included or exceeded the TVP value; S values were not computed for moisture

content values exceeding 60 percent nor for cases when the TVP was not

attained up to the maximum moisture content of the specimen.

For example, an S value of 0.10 over the moisture content range of 10 to

20 percent would mean that the Ry - Rp fitted curve increased 1.0 residual

standard deviation.

Tables A6 through AlO, A16 through A20, and A22 in appendix A give S values

for each Ry - Rp vs. Vp fitted curve for the capacitance, nuclear, and

infrared instruments respectively.

20
In table 5, the S values are summarized by three values: S(TVP), S(MID),

and S(MAX). The S(TVP) value is the S value in the moisture content range

in which the TVP occurs, while S(MAX) is the S value in the moisture content

range preceding the range containing the maximum moisture content. The

S(MID) value is the average of the S values for the moisture content ranges

between the range containing the TVP and the range preceding the range con- taining the maximum moisture content. Figure 17 shows a schematic - vs. Vp fitted curve and examples of S(TVP), S(MID), and S(MAX). For any

specimen, S(TVP), S(MID), and S(MAX) may or may not exist as follows:

o TVP was not attained ("TVP not Neither S(TVP), S(MID) or S(MAX)

attained") up to the maximum exist

moisture content of the

specimen

o TVP (e.g. 14 percent) occurred S(TVP) only exists

in the moisture content range

(e.g. 10 to 20 percent) containing the maximum moisture content.

o TVP (e.g. 22 percent) occurred in S(TVP) and S(MAX) exist; S(MID)

the moisture content range does not exist,

(e.g. 20 to 30 percent) preceding the moisture content range

(e.g. 30 to 40 percent)

containing the maximum moisture

content

o At least two moisture content S(TVP), S(MID) and S(MAX) exist

ranges (e.g. 20 to 30, 30 to

40 and 40 to 50 percent) exist

beyond the moisture content

range (e.g. 10 to 20 percent)

containing the TVP value.

For cases where the TVP existed but the maximum Vp value in the specimen

was less than the next higher multiple of 10 Vp (e.g. TVP = 12 percent and

the maximum Vp in the specimen was 18 percent), the computation of S(TVP)

was modified as follows: the S(TVP) value was based on a reduced moisture

content range measured from the maximum moisture content to the next lower

multiple of 10 Vp (for example, a reduced moisture content range of 10 to

18 percent if the TVP was 12 percent and the maximum moisture content was

18 percent).

To examine and compare the effects of the major factors in the study (NDE

method, insulation type and thickness, asphalt thickness and deck type),

plots of all the S values at or beyond the TVP value were made for each

specimen. These plots are called S vs. Vp plots and are shown in

21
figures A70 through A105, appendix A. The scale for the S axis was constructed as follows (see figure A70). A continuous linear scale was used for S values between 0.0 and 0.4, since most of the S values occurred

in this range. Discrete ranges of S were used for values exceeding 0,4

(0.40 to 0.49; 0.50 to 0.59; 0.60 to 0.69; 0.70 to 0.99; > 1.0) and for S

values less than 0.0 (0.0 to -0.049; -0.050 to -0.10; < -0.10). If no TVP

value was attained up to the maximum Vp value of the specimen (called

"TVP not attained"), a single point appears at a labelled location near

the bottom of the S axis and is plotted at the midrange of the moisture

content range in which the maximum Vp occurred. Values of S are plotted

at the midrange of the moisture content ranges used to compute S. For

example, for a moisture content range of 10 to 20 percent, the S value

would be plotted at 15 percent. The first point (S, Vp coordinates) on each specimen curve also represents the TVP for that specimen, with the

TVP plotted at the midrange of the moisture content range in which the

TVP occurred. For example, a TVP of 17 percent would be plotted at the

midrange of the 10 to 20 percent moisture content range or a 15 percent

Vp value. For the special case where the TVP existed but the maximum Vp

value was less than the next multiple of 10 Vp, the S value was plotted

at the midrange of the reduced moisture content range (e.g. TVP = 12

percent, maximum Vp = 18 percent, S based on moisture content range of

10 to 18 percent and TVP and S plotted at Vp of 14 percent). Tables A6

through AlO, A16 through A20, and A22 show the S values used in the S vs. Vp plots for each specimen, deck, and instrument combination. The S values for each specimen were connected by straight lines on the S vs. Vp

plots. For a given deck and instrument, there were in some cases more

than one specimen tested resulting in more than one S vs. Vp plot.

The purpose of figures A70 through A105 is to emphasize instrument response

differences in the S vs. Vp curves for particular combinations of construction variables. The S vs. Vp curves are shown for all instruments on each

figure. The "KEY" on the right side of each figure identifies the symbol

(e.g. TRI=triangle , "DIAM"-diamond) with each instrument (IR=inf rared)

.

Table 9 shows a summary of the percentages of the S values (at and beyond

the TVP) which were less than 0.0 and 0.2 for the capacitance and nuclear

instruments for each of the five insulations. Table 9 also presents percentages for all insulations combined. Information similar to that in

table 9 is presented in table 8 for the infrared instrument.

The S values for which the percentages are summarized in table 9 (less 0.0 , less than 0.2 ) were chosen to emphasize trends presented in later chapters.

Values of S less than 0.0 correspond to a concave downward shape and, more

important, indicate that both the Ry - Rp and (Ry-RD)/RSD responses are decreasing with increasing moisture content. The R value of 0.2 is significant because about 90 percent of the S values for the nuclear instruments

exceeded 0.2 while over 75 percent of the S values for the capacitance

instruments were less than 0.2. In general, higher S values are indicative

of better performance.

22
The slope, SS, of the S vs. Vp curve was also used as an indicator to

measure the ability to detect moisture beyond the threshold moisture

content. The SS values were found from:

SS = (2a2)/RSD (9)

where a2 is a quadratic curve coefficient appearing in eqn. 2.

Thus SS is a constant for each - vs. Vp fitted curve; a single SS

value was determined for each fitted curve whenever S values (eqn. 8) were

determined. (Neither S nor SS values were determined for cases when the TVP was not attained.)

Table 10 gives a summary of the percentages of the SS values (at and beyond

the TVP) which were less than -0.015 and 0.0 for the capacitance and nuclear

instruments and for each of the five insulations. Percentages for all insulations combined are also given in table 10. Information similar to that in

table 10 is shown in table 8 for the infrared instrument.

The values of SS for which percentages are summarized in table 10 were selected to illustrate trends. Values of SS less than about -0.015 correspond to a sharp drop in the S vs. Vp curve (for example, this was a strong

trend for the capacitance instruments for fiberboard insulation - see figures A86 through A93). In general, S vs. Vp curves which do not have

sharp decreases, are indicative of better performance.

To aid in interpreting the S vs. Vp curves shown in figures A70 through

A105, the graphical relationship between the Ry - Rd vs. Vp fitted curve

and the corresponding S vs. Vp curve are illustrated in figure 18. In

figure 18a, the Ry - Rp vs. Vp curve is essentially linear (small quadratic

component); the S values are positive and the SS values close to zero. Figure 18b shows a concave downward Ry - Rp vs. Vp curve, resulting in more

than a single Vp value for one Ry - Rp value. Here the S value is relatively

large and positive at A; at B the S value is zero; and at C the S value is

less than zero. The SS value (a constant) is negative (figure 18b). In

figure 18b, the S vs. Vp curve is linear, but appears broken because of the

discrete ranges chosen for the extreme S values. In figure 18c, the Ry - Rd vs. Vp curve is concave upward, corresponding to linearly increasing S values with increasing moisture content. Again note the break in the S vs. Vp curve. For this case (figure 18c), the constant SS value is positive.

Although the general shape of the Ry - Rj) vs. Vp fitted curve and the

corresponding ((Ry - R]))/RSD) vs. Vp curve will be similar, the magnitude

of the slope of the two curves could be significantly different. Thus one

of the characteristics of normalizing (dividing) by the RSD value is that

the slope (corresponds to S, see equation 6) of the normalized curve

((Ry ~ Rd)/P^SD) usually differs from the slope of the Ry - R^ curve. For

example, although two fitted Rtj - Rn curves may appear similar in slooe,

their normalized curves vjill not have similar slopes (S values) if they have

significantly different RSD values.

23
The indicators TVP , S, and SS are used in subsequent chapters to measure

instrument effects, that is, to assess differences between instruments of a given type (method) and between instrument types.

An example is:

o A significant difference in TVP, S, or SS values among the

capacitance, nuclear, and infrared methods for one or more combinations of construction variables (construction variable refers to

specimen composition and deck used, e.g. 1 in. thick glass fiber

insulation, "standard" asphalt thickness, steel deck).

These indicators were also used to measure construction variable effects

which occurred both within and between instrument types. An example is:

o A significant difference in TVP, S, or SS values for a particular

instrument or between two instrument types used on concrete as compared to steel deck (deck effect).

There are several factors which contribute to the uncertainty in estimating

the TVP, S, and SS values including:

o Lack of fit of model (quadratic used); for most of the data the

quadratic model appeared reasonable. In certain cases, however,

it was not. For example, the Ry ~ Rd ^P data sets for instrument C2 with perlite board and fiberboard are closer to a bilinear

than a quadratic shape (figures A15, 16, 21, 22, appendix A and

figure 11).

o Choice of normalization and sensitivity criteria, and definition of

TVP.

o Using the RSD as an average estimate of the standard deviation at

each moisture content.

o Uncertainty in the TVP value due to uncertainty in the moisture

content caused by gravel loss during testing (see section 3.2) as well as the measurement of the deviation of 3RSD (used in the TVP

definition) from zero and not from the intercept of the (Ry - RD)est

fitted curve.

These uncertainties must be recognized when using the TVP, S, and SS values

to measure instrument performance and to determine instrument and construction variable effects. Thus, significant differences in the TVP, S, and

SS values are needed for reliable conclusions regarding instrument

performance and instrument and construction variable effects.

Facing Page: Three types of electrical capacitance instruments were

used in this study.

24
5. ELECTRICAL CAPACITANCE METHOD

5.1 MECHANISM OF OPERATION

Electrical capacitance-radio frequency instruments respond to changes in

either the dielectric constant, which is a measure of the ability of material to store electrical energy, or in the dielectric loss factor, which

is related to the energy lost in an alternating electric field. Operation

of electrical capacitance-radio frequency instruments is given in detail

in reference [3]. Electrical insulators can be characterized by their

25
dielectric properties as well as by their electrical resistances. Detection

of roof moisture is based on the principle that either the dielectric constant or the loss factor for the roofing system with moisture will be significantly different than for the roofing system without moisture. Radio

frequencies (1 x to 30 x 10^ Hz) are used in most moisture determination

instruments. However, when large moisture contents are encountered, frequencies in the VHF range, (100 x to 300 x 10^ Hz) can be used. Using radio

frequencies, equipment is commercially available which measures dielectric

constant in some cases and dielectric loss factor in others.

Electrical capacitance instruments have been used for about 40 years by

paper mills, textile mills, and wall board producers to measure moisture

in their products. Some manufacturers' literature indicates that moisture

content readings should be accurate to less than + 2 percent. The various

items of equipment are in an advanced state of development and have taken

advantage of recent developments in electronics to enhance their dependability and portability. Available instruments make use of various electrode

configurations. These electrodes, which are attached to a constant frequency alternating current source, establish a field in the material to be

tested and determine the depth of penetration of the field. Current flow

or power loss can be measured.

The presence of moisture on the surface can greatly influence the response

and prevent obtaining information on the moisture content beneath the surface. Moisture may also have a profound effect on the "shape" of the

electrical field which can be established in the material. Regions of

high dielectric constant, such as wet regions, distort the field so that

the spacing of the field lines is closer there than in dry regions. Cases

where the moisture is not uniformly distributed or where discontinuities

exist in the material (such as joints) could lead to errors in interpretation, since most interpretations are based on the assumption that the

material is homogeneous. In addition to the field distortion, some instruments have limited penetration depths, which could prevent the detection

of moisture below a certain distance from the surface.

5.2 INSTRUMENT DESCRIPTION

Two typical, commercially available capacitance-radio frequency instruments

(not specifically sold for roofing applications) designated as Cl and C2

and one proprietary instrument, designated as C3, for which a roof survey

service is commercially available were investigated. During testing the

instruments were approximately centered on the surface of the specimens

and the dial reading recorded.

Instrument Cl (figure 3) contained a power loss circuit which operated at

10 Megahertz. Button-shaped electrodes covered an area 3 in. in diameter.

Instrument Cl was claimed by the manufacturer to have a penetration depth

of 3/4 in. The scale on the dial ranged from 0 to 50 units and could be

26
extended to a range of 0 to 100; scale divisions were marked: 0, 1, 2,

3 50. There were four moisture ranges; only moisture range 4, the

most sensitive moisture range, was used in this study.

Similar to instrument Cl, instrument C2 (figure 3) used a power loss

circuit and operated at 10 Megahertz. The electrodes of the C2 instrument

were two rollers, 3 5/8 in. wide and spaced 5 1/4 in. apart. The

penetration depth was claimed by the manufacturer as 2 in. The scale on

the dial ranged from 0 to 100 and could be extended to 200 units; scale

divisions were marked: 0, 1, 2, .... 100. There were three moisture

sensitivity ranges; only the "High", which was the most sensitive moisture

range, was reported in this study.

Instrument C3 (figure 19) used two capacitor plates mounted at the bottom

of the meter. A spray or fringe electrostatic field was formed between

the plates. The scale on the dial ranged from 0 to 25 units; scale divisions were marked on each half unit: 0, 0.5, 1.0, 1.5, 2.0 24.5,

25.0. There were two instrument settings, one for gravel-surfaced and the

other for smooth-surfaced roofs. The gravel setting was used in this study

because the instrument was used only on gravel-surfaced specimens. The

manufacturer recommends that instrument C3 should not be used on gravel

thicknesses greater than 5/8 in.

5.3 INSTRUMENT CALIBRATION

Calibration readings on the three instruments were usually taken at the

beginning of each day of testing. This was done to determine if the meters

were operating properly and to detect any change in meter response with time

which may have occurred during the testing period, which lasted about 150

days. The readings were taken on a piece of 1 1/8 in. thick polymethylmethacrylate mounted on a wooden stand about 6 in. high. Plots of the calibration readings vs the elapsed time for each of the instruments are shown in

figures 20, 21, and 22.

Because of instrument operating difficulties, instrument C2 was replaced

during the testing program after about 60 days. As shown in figure 21,

the calibration readings for both C2 instruments were in reasonable agreement, indicating that the two C2 instruments appeared to be similar in

their response. In general, limited data from both C2 instruments for

specimens containing moisture also indicated similar response. It is

noted that there was more scatter in the calibration curve for the C2

instrument which was replaced (figure 21),

The calibration curves for instruments C2 and C3 (figures 21 and 22) appear

to be relatively constant with time. Therefore, no adjustments were made

for the response of instruments C2 and C3 for specimens containing moisture.

For instrument Cl (figure 20), there was a maximum change of about 3 scale

units during the 150 day testing period. The change in response of

instrument Cl with time was for the calibration condition, that is, without

27
moisture. Because the change was considered small, and since it was not

known what change would have occurred on specimens containing moisture, no adjustment of the response for Instrument Cl was made for specimens

containing moisture.

5.4 TEST RESULTS

As discussed in chapter 4, the adjusted NDE response vs. moisture content

data sets for the three capacitance instruments are plotted in figures Al

through A36 in appendix A. The data are for gravel-sufaced specimens.

The "room dry" responses for instruments Cl, C2, and C3 for specimens 6

and 31 were estimated by the "room dry" responses for specimens of similar

composition. The "room dry" responses for specimen 56 were assumed for

specimen 6. As table 2 shows, the compositions of specimens 6 and 56 were

similar. The asphalt and gravel thickness and weight per unit area measurements were not determined for the specimen from which the "room dry"

responses for specimen 31 were estimated. However, both specimens were gravel-surfaced, contained nominal 1 in. thick polystyrene insulation, and

had similar total specimen weights. Table 4, which presents "room dry"

responses, shows that the assumed "room dry" responses for specimens 6

(i.e. see specimen 56) and 31 appear to be reasonable compared to other

"room dry" responses for the corresponding insulation type.

In some cases the response of instruments Cl and C2 for specimens containing

moisture exceeded the maximum scale reading. In these cases, the maximum

scale readings of 100 for instrument Cl and 200 for instrument C2 were used

for Ry. For instrument C2, most perlite specimens (nos. 11, 16, 66, and

18 - see figures A15 and A16) and fiberboard specimens (nos. 21, 658, 26,

and 29 - see figures A21 and A22) had many responses which exceeded the

maximum scale reading of 200 for both concrete and steel decks.

5.5 TRENDS

A discussion of the analysis techniques used are presented in chapter 4.

5.5.1 Detection of Minimum Moisture Content (TVP)

As table 7 indicates, instrument Cl, as compared to C2 and C3, in general

had as low or lower percentages of TVP values less than 10 percent for

each of the insulations and for all insulations combined. A similar trend

is seen for percentages of TVP values less than 20 percent.

Of the five insulations, perlite board and fiberboard had the highest

average percentages of TVP values less than 10 percent for the three instruments (table 7). A similar statement can be made for percentages of TVP

values less than 20 percent. This trend for perlite and fiberboard correlates with the steep initial rise of the Ry - Rp vs. Vp data sets (figures

A13 to A24, appendix A), particularly for instrument C2.

28
Instrument Cl, as compared to C2 and C3, had the highest average percentage

(38 percent, table 7) of TVP values not attained for all insulations; of the

five insulations, polystyrene and polyurethane had the higher percentages

(50 to 70 percent) of TVP values not attained for instrument Cl.

Instrument C2 had the lowest percentage (2 percent, table 7 ) of TVP values

not attained for all insulations.

As indicated in table 5 for instruments Cl and C3, many specimens with

"heavy" asphalt thickness had higher TVP values or did not attain TVP

values as compared to specimens with "standard" asphalt thickness. It is

noted that the gravel thickness was, in general, greater for the thicker

asphalt. Only 7 of the 52 (14 percent) TVP values for specimens with

"heavy" asphalt thickness were less than 10 percent as compared to 28 of

the 54 (52 percent) TVP values for "standard" asphalt thickness which were

less than 10 percent. (These percentages are based on the total number

of tests, including tests for which a TVP value was not attained). For

instrument Cl, there were no TVP values less than 10 percent for polystyrene

and polyurethane insulations. If polystyrene and polyurethane insulations

are excluded, a trend for instruments Cl and C3 similar to that above was

observed. (That is, only 19 percent of the TVP values for specimens with

"heavy" asphalt thickness were less than 10 percent as compared to 55 percent for "standard" asphalt thickness.) With instrument Cl, TVP values were

not attained for 16 of the 26 (62 percent) tests for specimens with "heavy"

asphalt thickness as compared to only 4 of the 26 (15 percent) tests with

"standard" asphalt thickness for which TVP values were not attained. For

instrument C3, all cases (5 out of 26, 19 percent) in which TVP values were

not attained occurred in tests with "heavy" asphalt thickness.

Table 5 also shows that the TVP values were not attained primarily for

specimens with:

o "Heavy" asphalt thickness for all insulations for instrument Cl.

o "Heavy" asphalt thickness for glass fiber, polystyrene, and

polyurethane insulations for instrument C3.

As evident from table 2, larger gravel thickness values correlated with

larger membrane weight per unit area and larger gravel weight per unit area

values. All 8 (100 percent) of the specimens with gravel thickness values

exceeding 0.60 in. had "heavy" asphalt thickness as compared to only 5 of

the 19 (26 percent) specimens with gravel thickness values less than

0,60 in. which had "heavy" asphalt thickness. All 14 specimens having

"standard" asphalt thickness had gravel thickness values less than 0.60 in.

The trend observed with instruments Cl and C3 for the "heavy" versus "standard" asphalt thickness (larger TVP values and more TVP values not attained

for "heavy" asphalt thickness) may, in general, be attributed to either

gravel thickness, asphalt thickness, or a combination of both. Since the

specimens with the "heavy" asphalt thickness also had, in general, larger

29
gravel thickness, the relative significance of these two variables was not

determined. During specimen fabrication, it was intended to have a typical

amount of gravel as recommended by the National Roofing Contractors Association. The values of gravel thickness given in table 2 were determined

after testing was completed. During handling and testing, some gravel fell

from the specimens (see section 3.2). Since gravel thickness was not con- trolled during testing, the trend of higher TVP values and more TVP values

not attained for larger gravel thickness as compared to smaller gravel

thickness is not known with certainty.

With instruments C2 and C3, many tests with specimens containing 1 in.

thick insulation had higher TVP values than tests with specimens containing

2 in. thick insulation. Only 18 of the 60 (30 percent) tests with 1 in.

thick insulation had TVP values less than 10 percent as compared to 35 of

the 48 (73 percent) tests with 2 in. insulation which had TVP values less

than 10 percent.

For instrument Cl, TVP values were not attained for 12 of the 22 (54

percent) tests with specimens containing 2 in. thick insulation as compared

to TVP values not being attained for only 8 of the 30 (27 percent) tests

with specimens containing 1 in. insulation. With instrument C3 , all cases

(5 out of 30, 17 percent) in which TVP values were not attained occurred in

tests with 1 in. thick insulation.

Hence, insulation thickness appeared to be a significant factor in

affecting TVP values and causing TVP values not to be attained, depending

on the instrument.

With instrument C3, all 5 cases for which TVP values were not attained

occurred on specimens with "heavy" asphalt thickness and 1 in. thick

insulation.

There were no significant deck effects (concrete vs. steel).

5.5.2 Detection of Moisture Content Beyond the TVP

Table 9 indicates that the capacitance instruments had their smallest

average percentage (0 percent) of S values less than 0.0 for glass fiber

insulation. Perlite board and fiberboard insulations had the largest percentages (35 and 29 percent) of S values less than 0.0. For all insulations combined, instrument C3 had the smallest (11 percent) percentage of

S values less than 0.0; a similar trend is evident with instrument C3 for

percentages of S less than 0.2. As previously discussed in section 5.4,

the response for instrument C2 exceeded the maximum scale reading on most

perlite and fiberboard specimens on both concrete and steel decks (figures

A15, A16, A21, and A22) thus making interpretation of Ry - Rp data difficult beyond the lower Vp values. The relatively large percentages of S values less than 0.0 and 0.2 for intrument C2 in table 9 for perlite and

fiberboard insulations are attributable, at least in part, to the flatness

30
of the - R]) vs. Vp data sets. Based on all insulations and the three

capacitance instruments, over 75 percent (table 9) of the S values were

less than 0.2.

Thus, in general, for some construction variable combinations, the S trends

given in tables 5 and 9 indicate that the capacitance instruments were

unable to detect moisture quantitatively at higher moisture contents beyond

the TVP.

In general for the S indicator and for the three capacitance instruments,

there were no significant deck effects (concrete vs. steel), insulation

thickness effects (1 in. vs. 2 in.), and asphalt thickness effects

("standard" vs. "heavy").

As indicated in table 10, the three capacitance instruments had their lowest

percentages of SS values less than -0.015 with polyurethane (0 percent) and

glass fiber (12 percent) and their highest percentage with fiberboard (92

percent). That is, fiberboard had more sharp drops in the S vs. Vp curves

(figures A86 through A93 , appendix A) as compared to the other insulation

types.

5.5.3 Shape of Data Sets and Their Fitted Curves

Many of the Ry - Rj) vs. Vp data sets (figures Al through A36, appendix A)

and their fitted curves tended to be concave downward for the capacitance

instruments. This trend is supported by relatively large percentages (11

to 22 percent, table 9) of S values less than 0.0. The concave downward

trend was particularly strong for perlite and fiberboard insulations.

For specimens containing perlite and fiberboard insulations, many of the

adjusted NDE response versus moisture content data sets (figures A13 to

A24, appendix A) for the capacitance instruments showed the following

trend: the adjusted NDE responses rose sharply at moisture contents of

about 10 percent or less and then leveled off or decreased with increasing

moisture. Thus, for these cases, it was not possible to distinguish between

relatively low moisture contents and larger moisture contents. The trend

of flatness due to off-scale responses for instrument C2 with specimens

containing perlite (figures A15 and A16) and fiberboard (figures A21 and

A22) has been discussed in section 5.5.2.

5.5.4 "Room Dry" Response

Table 4 shows, for 18 roofing specimens, the "room dry" responses for the

"standard" and "heavy" asphalt thicknesses with concrete and steel decks

for the three capacitance instruments. Also shown is the difference in

"room dry" responses between the "heavy" and "standard" asphalt thicknesses.

Two specimens were chosen for each insulation type and thickness combination.

Where possible, the specimens were chosen such that (a) the "room dry"

readings were taken not more than seven days apart and (b) the membrane

31
weight per unit area difference between "standard" and "heavy" was as large

as possible.

As evident from table A, in general the response for the "heavy" asphalt

thickness exceeded the "standard" by a relatively small amount. For the

most part, the absolute value of the response for the "heavy" asphalt thickness minus the "standard" asphalt thickness (absolute value of "Hvy-Std")

values were less than the 3RSD values shown in table 5 for each instrument.

Instruments Cl and C2 had very large responses for specimen 18 tested on both concrete and steel decks as compared to the other specimen responses.

The reason for this was not determined.

5.5.5 Additional Considerations

Several factors should be noted with regard to uncertainty introduced in

the laboratory study. In general, efforts were made to maintain visibly

surface dry specimens. At times during testing, however, the surfaces of

the specimens may have had small amounts of moisture thus affecting the

instrument response. The few outliers (see section 4,1) may have been the

result of surface moisture.

Gravel loss from the specimens (discussed in section 3.2) may have

effectively reduced the distance from the capacitance instruments to the

specimens and their decks. Thus as testing progressed and the gravel loss

occurred, the instrument responses may have been affected.

Facing Page: Nuclear backscatter instruments used in this investigation.

32
6. NUCLEAR BACKSCATTER METHOD

6.1 MECHANISM OF OPERATION

The mechanism of operation of the nuclear backscatter method is described

in detail in reference [3], Briefly, a radioactive isotope source emits

fast neutrons into a sample. The neutrons are scattered and slowed down,

primarily due to collisions with the nuclei of hydrogen atoms. The slowed

down or backscattered neutrons are counted by a detector and are related

to the number of hydrogen atoms present in the sample. The presence of

33
water in a sample, such as a roofing system, furnishes hydrogen nuclei for

this slowing process. However, other materials in the roof system, such

as hydrocarbons (asphalt, felts, insulation, concrete deck, etc.), also

contain hydrogen. Since the activity in the detector is related to the

total amount of hydrogen present in the volume of the sample being monitored,

the interpretation of the detector reading as being due to moisture alone

may not be valid.

6.2 INSTRUMENT DESCRIPTION

Due to the limited scope of this study, only two of the commercially

available nuclear instruments used in roof surveys were evaluated. The two

nuclear instruments used were referred to as Nl (figure 19) and N2 (figure 3).

The instruments were placed approximately on the center of the specimen and

neutron counting was initiated. ^-Jhen the neutron counting ended, the digital

response was recorded. The radioactive neutron source for both instruments

was americium beryllium, 40 millicures. The neutron source was sealed for

both meters. In instrument Nl , polyethylene neutron moderator shielding was

used, whereas in instrument N2 , no moderator shielding was used. The time

period for each reading was 30 seconds for instrument Nl; instrument N2 had

15 second, 60 second and 4 minute settings. During this study, the 60 second

setting was used. The output for both Instruments was displayed digitally

to the nearest count.

6.3 INSTRUMENT CALIBRATION

In general, calibration readings on both instruments were taken at the

beginning of each day of testing. This was done to determine if the

instruments were operating properly and to detect any change in instrument

response that may have occurred in the testing period which lasted about

150 days. The calibration readings were taken on a reference platform

(provided by the manufacturers), which was placed over one location on a concrete floor. Plots for each instrument of the response vs. the elapsed

time are shown in figures 23 and 24. In general, each point in figures 23

and 24 was based on 4 minutes of counting for each meter.

There was a definite trend of increasing instrument response x-zith elapsed

time for instrument Nl (figure 23) but not for instrument N2 (figure 24).

In addition to the calibration response taken on reference platforms,

calibration responses for instruments Nl and N2 were periodically taken

directly on the surface of the concrete and steel decks used in testing

the roofing specimens. The decks v/ere in their same positions as used

when testing roofing specimens but vzithout roofing specimens on them. A

definite trend of increasing instrument response with elapsed time was again observed for responses taken on the decks for instrument Nl but not

for instrument N2

.

For instrument Nl and for a given elapsed time interval, the ratio of the

calibration responses taken at the beginning and end of the time Interval

34
was about the sane for responses taken on the reference platform and on the

concrete and steel decks. This ratio, which did not change over a wide range

of instrument response values, was used to adjust the response of instrument

Nl for time effects. That is, the following equation was used to account for

a change in instrument response during the elapsed time interval between when

the "room dry" and subsequent "wet" NDE responses were taken on the roofing

specimens:

^ Ry = R X -2 (10)

where Ry = corrected NDE "wet" response for which the time interval between

"room dry" and "wet" responses is accounted for,

R = unadjusted "wet" NDE response,

= calibration response (figure 23) on reference platform for when

"room dry" NDE response was taken,

Cy = calibration response (figure 23) on reference platform for when

"wet" NDE response was taken.

The values of and Cy used were based on weekly averages, which were

found by averaging the calibration readings (up to 7, figure 23) for each

week.

Equation (10) was used only for instrument Nl, since no definite trend for

calibration response occurred for instrument N2.

6.4 TEST RESULTS

As discussed in chapter 4, the adjusted NDE response vs. moisture content

curves for the two nuclear instruments are plotted in figures A37 through

A60 in appendix A. The data are for gravel-surfaced specimens.

For instruments Nl and N2 and for specimens 6 and 31 , the "room dry"

responses were estimated as the initial "wet" responses, which corresponded

to the lowest Vp values (Vp of 0.3 percent for specimen 6 and 0.9 percent

for specimen 31). Since the Vp values corresponding to the initial "wet"

responses were near the "room dry" Vp values, the estimated "room dry"

responses are believed to be reasonable.

6.5 TRENDS

A discussion of the analysis techniques used are discussed in chapter 4.

35
6.5.1 Detection of Minimum Moisture Content (TVP)

Table 7 shows that, for all insulations except glass fiber, at least 50

percent of the TVP values were less than 10 percent for each nuclear instrument. Table 7 indicates that all TVP values were attained for both nuclear

instruments and that all TVP values were less than 20 percent for all insulations except glass fiber, for which about 70 percent of the TVP values

were less than 20 percent.

As evident from table 5, with both nuclear instruments many tests with

specimens containing 1 in. thick insulation had higher TVP values as com- pared to tests with specimens containing 2 in. thick insulation. Only 27

of the 60 (45 percent) TVP values for specimens with 1 in. insulation were

less than 10 percent as compared to 38 of the 48 (79 percent) TVP values

for specimens with 2 in. insulation which were less than 10 percent.

In many cases with instrument N2 , specimens tested on the steel deck had

higher TVP values than specimens tested on the concrete deck. Only 13 of

the 27 (48 percent) TVP values for specimens tested on the steel deck had

TVP values less than 10 percent as compared to 21 of the 27 (78 percent)

TVP values for specimens tested on the concrete deck which had TVP values

less than 10 percent.

There were no significant asphalt thickness effects ("standard" vs. "heavy")

.

6.5.2 Detection of Moisture Content Beyond the TVP

As table 9 indicates, the percentages of S values less than 0.2 were less

for instrument N2 than Nl for all insulations. However, all S values were

positive and, in general, considerably exceeded zero for both instruments

and for all insulations. For both instruments, an average of 87 percent

of the S values for all insulations exceeded 0.2 (table 9). The following

table shows the percentages of S values less than 0.2, 0.3, and 0.4 for

each insulation type for instruments Nl and N2 taken together.

Glass Fiber Perlite Fiberboard Polystyrene Polyurethane

S < 0.2 25 5.1 4.2 20 7.3

S < 0.3 62 20 8.5 33 24

S < 0.4 78 38 19 51 51

As indicated by the table, lower S values occurred for glass fiber and

higher S values for fiberboard as compared to the other insulation types.

36
Table 11 shows for instruments Nl and N2 the significant deck, insulation

thickness, and asphalt thickness effects which occurred based on the S indicator. The corresponding figure numbers of the S vs. Vp plots on which

the effects are based are also shown. For example, the top left entry for

instrument Nl, "1", Std, PU" under the column "Concrete S > Steel S" means

that for instrument Nl and the construction variables of 1 in. thick, polyurethane insulation and "standard" asphalt thickness, the S values corre- sponding to the concrete deck significantly exceeded the S values for the

steel deck. This effect can be seen by comparing the S vs. Vp curves for

instrument Nl in figures A102 and A103.

From table 11, the following trends for the deck effects are apparent:

o With both instruments, all but one deck effect occurred with 1 in.

thick insulation.

o With one exception, for instrument Nl , the S values for the steel

deck exceeded those for the concrete deck, while for instrument N2,

the S values for the concrete deck exceeded those for the steel

deck.

Trends in table 11 for both instruments for the insulation thickness

effects are:

o All insulation thickness effects occurred only for the case where

the S values for the 2 in. thick insulation exceeded those for the

1 in. thick insulation.

o Seven of the nine cases occurred with "heavy" asphalt thickness.

Trends in table 11 for both instruments for asphalt thickness effects are:

o All asphalt thickness effects occurred only for the case where the

S values for the "standard" asphalt thickness exceeded those for

the "heavy" asphalt thickness.

o Eight of the ten cases occurred with 1 in. thick insulation.

No significant construction variable effects in table 11 were observed for

glass fiber insulation.

As apparent from, table 10, most SS values exceeded -0.015 for both

Instruments.

6.5,3 Shape of Data Sets and their Fitted Curves

In general, the Ry - vs. Vp data sets (figures A37 through A60) for

both nuclear instruments were approximately linear in shape.

37
6.5.4 "Rootn Dry" Response

As discussed previously, the nuclear response can be strongly affected by

any hydrogen bearing material, such as asphalt and concrete. Thus, if the

hydrogen content of the roof construction varies and is not accounted for,

it will add uncertainity to the moisture determination. Table 4 presents

responses for both nuclear instruments for 18 specimens with "standard"

and "heavy" asphalt thicknesses and tested on concrete and steel decks for

the "room dry" moisture content. The response for the "heavy" asphalt

thickness minus the "standard" asphalt thickness ("Hvy-Std") values, with

one exception, were always positive. With each instrument and in most

cases, the "Hvy-Std" values exceeded the 3RSD values in table 5. In some cases, the "Hvy-Std" values were considerably larger than the 3RSD values

of each instrument. Thus, variable asphalt content, similar to the "standard" and "heavy" asphalt thicknesses of this study, could confound the

response and appear to be water, as defined by the TVP definition (3RSD)

used in this study. Coring would be needed to account for variability of

this magnitude in the asphalt content.

6.5.5 Additional Considerations

Several factors should be mentioned with regard to the uncertainty

introduced in the laboratory testing. At times during testing, responses

were taken on adjacent specimens resulting in the two nuclear instruments

being separated from each other by about 2 ft. (figure 3). During these

times, each instrument could affect the other's response. However, due

to the distance of separation, this effect was not believed to have a significant effect on the responses. Gravel loss from the specimens (discussed in section 3.2) may have effectively reduced the distance from the

nuclear instruments to the hydrogen sources (asphalt, moisture, concrete

deck, etc.). Thus, as testing progressed and the gravel loss accumulated,

the nuclear instruments would tend to have somewhat higher readings. Ho\\rever, this gravel loss effect is believed to be insignificant because the

gravel loss occurred gradually throughout testing and because the gravel

thickness decrease due to gravel loss was probably relatively small.

Facing Page: Infrared thermography instrument and test setup

used in testing.

38
7. INFRARED THERMOGRAPHY tlETHOD

7.1 MECHANISM OF OPERATION

The physical principles involved in the operation of infrared thermography

systems and the factors involved in the response of this instrumentation to

moisture in roofing systems are described in detail in reference [3].

Briefly, an infrared thermography system consists of an infrared sensor or camera-like unit and a display unit which is much like a TV-monitor. The

infrared camera responds to radiation which is either emitted from or

39
reflected from a roof surface. For given environmental conditions, the

intensity of emitted radiation depends on the surface temperature and the

omittance of the roofing system while the intensity of reflected radiation

depends on the incident solar and sky radiation and the reflectance of the

roof surface. By definition, omittance is a measure of radiation efficiency

of a real surface and it is equal to the absorptance if the surface can be

characterized as a "grey body". The sum of the reflectance, or the fraction

of incoming radiation which is reflected, and the absorptance, or the

fraction of incoming radiation which is absorbed, is equal to unity.

The heat transfer modes which affect the roof surface temperature are:

conduction through the roofing system, convection at the roof surface,

absorption of solar and night sky radiation, and absorption of radiation

from neighboring buildings. Since the roofing system consists of a structural deck, insulation, and a built-up membrane, the heat conductance

(and heat capacity for transient conditions) of each of these components

influences heat conduction through the roofing system. If water or water

vapor is present in the insulation or one of the other components, then

conductance is increased and the surface temperature is changed. Such

changes in the surface temperature are detected as differences in infrared

radiation intensity and displayed. The different shades of grey associated

with the different radiation intensities over wet regions allows these

regions to be identified. A picture (thermogram) of the display can be

taken.

Variations in roofing system construction can also lead to variations in

surface temperatures. Examples are variations in the:

o thickness of built-up membrane

o thickness of insulation

o thickness of structural deck

o major structural members, such as beams and joists

Heat sources under the roof or on the roof surface can have a similar

effect. Thus, careful interpretation of thermograms is necessary to

insure that moisture is the cause of the surface temperature differences

indicated by the thermograms.

7.2 INSTRUMENT DESCRIPTION

Because of the similarity in method of operation of the various commercially

available infrared thermography systems, only one system was evaluated.

This system is shown in figure 25.

The sensor or camera-like unit (right side, figure 25) consists of infrared

transparent lenses, a mechanical-optical scanner and an infrared radiation

detector. The radiation detector is relatively small (0.35 mm diameter)

and responds to radiation in the 2.0 X 10-6 to ^ lO'^ m wavelength band.

40
Other systems have detectors which operate in the 8.0 x 10 ° to 14.0 x 10 " m

band.

The mechanical-optical scanner consists of rotating prisms, or mirrors,

which provide a vertical and horizontal scan of the field of view. Different points in the field are sequentially aligned with the detector by the

scanning elements and in this way the radiant flux from each point or small

region of the surface of the roof is read by the detector. The amplified

voltage output of the radiation detector is used to modulate the beam

intensity of a cathode ray tube in the display unit (left side, figure 25),

By coordinating the scanning systems in the camera unit and the cathode ray

tube, a black and white monochrome image is produced whose grey tones

correspond to the point-by-point radiation intensities. These intensities

are different for surface points over wet insulation compared to surface

points over dry insulation.

The image displayed on the cathode ray tvibe screen has a reference grey

scale at the bottom. In addition, so-called isotherms can be superposed

on the image. Isotherms are produced by causing an arbitrarily selected

Intensity to show as white on the image and on the reference grey scale.

If two isotherms corresponding to different intensities are used, the difference in intensity between points under the isotherms can be determined

within + 0.2°F when using the most accurate scale.

Infrared wavelengths rather than wavelengths in the visual range are employed because surfaces at temperatures in the 0°F to 180°F range have a much greater radiation intensity in the infrared region. Substantial intensity in the visual region would not occur until the temperature is increased

to about 1000°F or until the wavelength viewed is incandescent. The temperature range from 0°F to 180°F' is considered to be typical of roof surface

temperatures under practical viewing conditions.

The observed radiation intensity differences between regions in the field

of view can be converted to a temperature difference, but in the field of

view an apparent radiance temperature difference rather than an actual

temperature difference is obtained. This is because the sensor responds

to both emitted and reflected radiation. If there is no incident radiation,

as in the laboratory, or if it is constant during measurement, only emitted

radiation is significant. Under the latter conditions, the apparent radiance temperature difference and the actual temperature difference are the same if the correct emittance and intensity-temperature law are used.

When the response of a given specimen was being determined, the difference

in temperature or radiation intensity was observed between the center of a specimen subjected to a steady-state heat flux (described in section 7.3)

and a reference pad at room temperature. An isotherm capability of the

instrument was used by which the Intensity difference measurement was determined by observing the number of tonal differences in the grey scale on the

displayed image of the reference pad and specimen surface. Calibration

41
curves furnished with the instrument simplify the conversion from grey

scale units to temperature.

7.3 DECK Mm TESTING ENVIRONMENT

Because of lengthy experimental runs required to reach the appropriate

conditions for measurement, fewer specimens were subjected to infrared

thermography as compared to the other two NDE methods and all specimens

were placed over a steel deck (sam.e deck type as used for the capacitance

and nuclear testing).

As is evident from the discussion of section 7.1, moisture in the insulation

or in the built-up membrane alters the thermal conductance. To cause this

alteration in conductance to affect the surface temperature, it was necessary to impress a heat flux through the specimen. The experimental

arrangement for impressing the heat flux is shown in figure 26.

Roofing specimens with various levels of moisture were placed on the steel

deck which formed the top of an insulated box. The upper portions of the

two boxes are shown in figure 26. The interior of each box was maintained

at approximately 100°F by continuous operation of a variable resistance

controlled incandescent lamp and a low-speed fan. The boxes were located

in an environmental room that was maintained at 50°F and 10 percent relative

humidity. Specimens were allowed to come to steady-state conditions in

this environment. Boundary conditions were consequently "radiation" boundary conditions since a roofing specimen was used on the steel deck in contact with a medium at 100°F nominal on the deck side and a medium at 50°F

nominal on the built-up membrane side. One dimensional heat flow conditions

were attained at the center of the specimen.

Thermocouples were attached to the built-up membrane surface of the speci- men in all cases. The temperature in the interior of the insulated box was

read by a thermocouple positioned about 3 in. below the specimen center.

The temperature in the environmental room was determined from a thermocouple

em.bedded in the membrane surface of a temperature reference pad. This

temperature reference pad was a 10 in. by 10 in. piece of polyurethane

insulation with a built-up membrane attached. Two pads were actually used, one with a smooth asphalt surface and one with gravel surfacing. The pads can be seen in figure 26 at the extreme left end and right end of the

supporting structure over the roofing specimens.

To provide normal incidence viewing of the specimens without tilting the

infrared camera unit, observations were made through a mirror with high

infrared reflectance mounted at 45°. These are shown in figure 26 next to

the temperature reference pads.

For all thermography observations, thermocouple readings were taken of the

specimen surface temperature, the interior temperature of the insulated box,

and the reference pad temperature or room temperature. The specimen surface

temperature measured by the thermocouples provided a check on the temperature

42
measured by use of the thermographic system. Although the data are not

reported here, the agreement was good in all cases.

Thermographic temperatures were reduced from the measured data by means of

the equation.

Tg^-^ = Tp^*^ + 7.2574 AI (11)

where TC5 = surface temperature (°C),

Tp = reference pad or room temperature (°C),

AI = change in intensity represented by the product of the number

of grey scale units and the sensitivity setting.

Since only radiation in the 2.0 x 10 " to 5.6 x 10 " m band is "seen" by

the thermography system, the usual fourth power of the temperature law is

not correct. Equation 11 is a curve fitted to an instrument calibration

curve for temperatures from 0°C to 30°C.

The results in this report are in the form of normalized temperatures since

the temperature gradient across the specimen and the room temperature were allowed to vary somewhat from specimen to specimen. The normalized

temperature parameter, R, is given by:

R = (Ts-Tp)/(Tj^-Tp) (12)

where Tg is the interior temperature in the insulated box

and Tg-Tp is the temperature gradient across the specimen. The above

equation is derived from the steady-state heat flow equation which is:

Hs(Ts-Tp) = Ct (Tg-Tp) (13)

where Hg is the exterior surface heat transfer coefficient, and

C-j- is the total thermal conductance of the exterior surface layer,

built-up membrane, insulation, deck, and interior surface

layer.

Since moisture in a specimen would increase the thermal conductance of

either the insulation or the built-up membrane, C-p would be altered by moisture but Hg would not. The parameter R is directly proportional to C-p and

the variation of R is related to moisture in the same way (except for a constant multipler) as C-p.

Ry is the value of R obtained from eqn. 12 when Tg is measured on a specimen

containing moisture and Rp is the value of R when Tg is measured on a "room

43
dry" specimen. As with the other NDE methods discussed, the adjusted NDE

response (Ry-R])) is reported.

7.4 TEST RESULTS

The adjusted NDE response vs. moisture content and their corresponding

fitted curves are shown in figures A61 through A69 in appendix A.

Because it was necessary to subject each specimen to a steady-state heat

flux before readings were taken, it was not possible to cover the full

range of construction variables with the infrared instrumentation. As

already noted, one deck type (steel) was used. The full range of moisture

contents, Vp , was investigated for roofing specimens having perlite, glass

fiber, and polystyrene insulations. With smooth-surfaced specimens, both

1 in. and 2 in. insulation thicknesses were tested. However, for gravelsurfaced specimens only the 1 in. insulation thickness was investigated.

All specimens had a "standard" asphalt thickness.

The response of the thermographic system to smooth-surfaced and to

gravel-surfaced specimens was similar. This means that for a smoothsurfaced specimen and a gravel-surfaced specimen at the same surface temperature as measured by a thermocouple on the asphalt surface, the image

intensities on the display unit were almost identical. Thus, in comparing

the response from the different instrument types (chapter 8), results for

smooth-surfaced specimens were interpreted as though these results were for

gravel-surfaced specimens.

7.5 TRENDS

A discussion of the analysis techniques used are presented in chapter 4.

7.5.1 Detection of Minimum Moisture Content (TVP)

The following trends were observed (table 6):

o For a given insulation type, the TVP values for the 2 in. thick

insulations were less than for the 1 in. thick insulations.

o For a given insulation thickness, the TVP values for perlite

insulation were lower than glass fiber and polystyrene insulations.

o All TVP values were: for perlite less than 15 percent; for glass

fiber less than 33 percent; and for two of the three TVP values

for polystyrene, less than 27 percent.

In one out of nine TVP values, the TVP was not attained up to the maximum

Vp (17 percent) of the specimen, which contained 1 in. thick polystyrene

insulation (table 6).

44
1,5.1 Detection of Moisture Content Beyond the TVP

All S values (table A22) were positive and, in general, considerably

exceeded 0.0 for all three insulations. For the three insulations combined

62 percent of the S values exceeded 0.2 (table 8).

With specimens containing 2 in. thick insulation, the S values for perlite

(figure A83) and polystyrene (based on only one S value, figure A99)

exceeded those for glass fiber (figure A75).

Two of the eight SS values for the infrared instrument were less than

-0.015 (specimen 61, figure A79 and specimen 733, figure A83). These two occurrences were not considered significant because the corresponding S

values were relatively large.

7.5.3 Shape of Data Sets and Their Fitted Curves

In general, the shape of the Ry - Rp vs. Vp data sets (figures A61 to A69) were approximately linear.

7.5.4 Additional Considerations

When comparing the various NDE methods, it should be noted that the infrared

thermography system produces more information than is represented by Ry or Rp. Since an infrared picture of the roof surface is presented, it is possible to define the boundaries of "hot" or wet areas whereas the capacitance

and nuclear methods yield only a point reading.

45
Facing Page: Intrusion of moisture in roofing systems can cause

premature failures.

46
8. COMPARISON AND INTERPRETATION OF RESULTS AND TRENDS FOR CAPACITANCE,

NUCLEAR, AND INFRARED METHODS

The "EXECUTIVE SUMMARY" presents the findings and conclusions of this study.

This chapter presents a comparison and discussion of the; findings for the

three NDE methods investigated.

47
8.1 SUWIARY OF RESULTS

Table 12 summarizes the results for the capacitance, nuclear, and infrared

instruments for all insulations for the TVP, S, and SS indicators presented in chapters 5, 6, and 7. Table 13 summarizes the instrument effects

for specimens witli the "standard" asphalt thickness and tested on steel

deck v/ith the capacitance, nuclear, and infrared instruments. In table 13,

the following symbols are used:

C = capacitance instruments Cl, C2, and C3

N = nuclear instruments Nl and N2

IR = infrared instrument

~ = approximately equal to

For example, the top left entry of "C < N" in table 13 is for the indicator

TVP and for 1 in. thick glass fiber insulation. It means that the TVP

values for the capacitance instruments were, in general, less than the TVP

values for the nuclear instruments. Some subjectivity was introduced in

determining the entries in table 13. None the less, it is believed that

the subjectivity introduced is minimal and should not affect the general

trends shown in table 13. Table 13 shows the figure numbers for the S vs. Vp plots on which the S table entries are based. The TVP indicator entries were based on table 5 and table A21. Infrared instrument trends shown in

tables 12 and 13 are based on results from specimens containing "standard"

asphalt thickness and glass fiber, perlite, and polystyrene insulations

tested on steel deck.

Table 14 presents the construction variable sets* for the instrument effects

between capacitance and nuclear instruments as measured by the TVP and S

indicators. For example, for the instrument effect "Nuclear < Capacitance"

measured by the TVP indicator, the construction variable set for glass fiber

is: 1", 2", llvy, C,S. This means that the TVP values for the nuclear

instruments were in general less than the capacitance instruments for speci- mens containing 1 and 2 in. thick glass fiber insulation, for "heavy" asphalt

thickness, and tested on concrete and steel decks. As discussed for table 13, some subjectivity, which was judged to be minimal, was introduced in assigning the entries for table 14. Table 14 gives the figure numbers for the S vs. Vp plots on which the construction variable set entries for S are based. The

construction variable sets for the TVP indicator are based on table 5.

Table 15 presents the percentages of TVP values less than 10 percent, less

than 20 percent, and "not attained" for the "standard" versus "heavy"

asphalt thicknesses and for 1 in. versus 2 in. thick insulations. As

previously noted, gravel thickness was, in general, greater for the "heavy"

* The term construction variable set means a combination of one or more construction variables (for example, specimen containing 1 in. thick,

glass fiber insulation, with "standard" asphalt thickness and tested on

a steel deck).

48
asphalt thickness. The purpose of table 15 is to illustrate asphalt and

insulation thickness effects with the capacitance and nuclear instruments.

8.2 DETECTION OF MINIMUM MOISTURE CONTENT (TVP)

In general for each insulation type, the percentages of TVP values less than

10 percent for nuclear Instruments equalled or exceeded the corresponding

percentages for the capacitance instruments (table 7) and the infrared

instrument (table 8). A similar trend is seen for percentages of TVP values

less than 20 percent.

As given in table 12, in general, for all insulations combined, the nuclear

instruments had higher percentages of TVP values less than 10 percent than

did the capacitance and infrared instruments. A similar statement can be

made for percentages of TVP values less than 20 percent.

With glass fiber, perlite and polystyrene insulations, the percentages of

TVP values less than 10 percent were not significantly different for the

capacitance instruments C2 and C3 (table 7) and the infrared instrument

(table 8). The percentages of TVP values less than 10 percent for glass

fiber, perlite, and polystyrene insulations were significantly lower for

instrument Cl as compared to instruments C2 and C3 (table 7) and the

infrared instrument (table 8).

For the capacitance instruments C2 and C3 , the TVP was not attained for 2 to 9 percent of the tests (table 12) as compared to the nuclear instruments,

for which TVP values were always attained. Instrument Cl had a significantly

larger percentage (38 percent, table 12) of TVP values not attained as com- pared to instruments C2, C3, Nl, N2, and the infrared instrument. With the

infrared instrument, 1 TVP value in 9 tests (11 percent) was not attained.

However, the significance of this result for the infrared instrument is not

known due to the limited infrared data.

The TVP instrument effect trends based on table 13 are:

o With one exception, the TVP values for the nuclear and infrared

instruments were about the same for the three insulations.

o For glass fiber insulation, the TVP values for the capacitance

instruments were less than or about equal to the nuclear and

infrared instruments.

o With perlite and polystyrene insulations, the TVP values for the

nuclear and infrared instruments were less than or about equal to

the capacitance instruments.

Based on table 14, the following instrument trends for nuclear and

capacitance instruments are apparent:

49
o The TVP values for the nuclear instruments were less than the

capacitance instruments for the construction variable sets shown;

there were one or more construction variable sets for all

insulation types.

o Only for 1 and 2 in. glass fiber insulation, with "standard" asphalt

thickness, and for steel deck were the TVP values for the capacitance

instruments less than the nuclear instruments.

The entries in table 14 correlate with the as large or larger percentages

of TVP values less than 10 percent for nuclear as compared to capacitance

instruments with perlite, polystyrene, and polyurethane insulations as given in table 7. A similar statement can be made for the TVP values less

than 20 percent. As evident from table 15, with "standard" asphalt thickness the percentages of TVP values less than 10 percent for the capacitance

instruments C2 and C3 were about the same as compared to the nuclear instruments. A similar statement can be made for percentages of TVP values less

than 20 percent. Instrument Cl for "standard" asphalt thickness had a significantly lower percentage of TVP values less than 10 percent as compared to instruments C2 , C3, Nl, and N2.

With the "heavy" asphalt thickness, the nuclear instruments had significantly

larger percentages of TVP values less than 10 percent as compared to capacitance instruments Cl and C3. A similar trend is evident for percentages of

TVP values less than 20 percent. As discussed in chapter 5, because specimens with "heavy" asphalt thickness may have had, in general, larger gravel

thicknesses during testing, the relative significance of the asphalt and

gravel thickness variables could not be determined. This confounding of the

gravel and asphalt thickness needs to be recognized when comparing the

capacitance instruments with the nuclear instruments.

Table 15 indicates that instruments C2, C3, Nl and N2 had significantly

larger percentages of TVP values less than 10 percent for specimens with

2 in. as compared to 1 in. thick insulation. A similar but weaker trend

is seen for percentages of TVP values less than 20 percent.

8.3 DETECTION OF MOISTURE CONTENT BEYOND THE TVP

Perhaps the most significant effect between the capacitance, nuclear, and

infrared instruments was that effect which was measured by the percentage

of S values less than 0.0. As table 12 indicates, from about 10 percent

(instrument C3) to 20 percent (instruments Cl and C2) of the S values for

the capacitance instruments were less than 0.0 as compared to no S values

(0 percent) less than 0.0 for the nuclear and infrared instruments. The

trend of the S values less than 0.0 for the capacitance instruments was strongest for the perlite and fiberboard insulations; no values of S were

less than 0.0 for the capacitance instruments for glass fiber insulation

(table 9). The significance of the S values less than 0.0 is that the

adjusted NDE responses, Ry - Rp , and (Ry - Ro)/RSD, are decreasing per

50
increase in Vp (figure 18b). Also most (76 percent, table 9) of the S values for the capacitance instruments were less than 0.2, compared to

38 percent (table 8) of the S values for the infrared instrument being

less than 0.2. These are in contrast to most (87 percent, table 9) of the

S values for the nuclear instruments being greater than or equal to 0.2.

For all construction variable combinations, the S trends given in tables 5,

8, 9, and 12 indicate that the nuclear and infrared instruments were able

to detect moisture quantitatively at higher moisture contents beyond the

TVP (no S values less than 0,0). The capacitance instruments, for some construction variable combinations, could not detect moisture quantitatively

at higher moisture contents beyond the TVP,

As indicated in table 12, 33 percent of the SS values for the capacitance

instruments were less than -0.015 as compared to 25 percent of the infrared

SS values and 5 percent of the nuclear values. The significance of the SS

values less than -0.015 is that the S vs. Vp curve drops sharply. With the

capacitance instruments, values of SS less than -0.015 occurred most often

(92 percent, table 10) for specimens containing fiberboard insulation

(figures A86 through A93). The occurrences of SS values less than -0.015

for the infrared and nuclear instruments were not considered significant

because, in general, the corresponding S values were relatively large.

Based on table 13, the instrument effect trends for the capacitance, nuclear,

and infrared instruments for the S indicator are:

o For the three insulations, the S values for the nuclear instruments

exceeded the S values for the capacitance instruments and were about

the same (with one exception) as the S values for the infrared

instrument.

o For glass fiber and perlite insulations, the infrared S values

exceeded the capacitance S values.

The instrument effect trends for the capacitance and nuclear instruments

as taken from table 14 are:

o The S values for the nuclear instruments exceeded those for the

capacitance instruments for all combinations of construction variables investigated except for 1 in, thick glass fiber insulation

with "heavy" asphalt thickness tested on concrete and steel decks,

(The lack of S values for the capacitance instruments for 1 in.

polystyrene insulation with "heavy" asphalt thickness and tested

on steel deck prevented determining an instrument effect trend for

this combination.)

o There were no construction set entries for which the capacitance

instrument S values exceeded the nuclear instrument S values.

51
These trends are in agreement with the relatively large percentages of S values less than 0,0 and 0.2 (table 9) for the capacitance instruments as compared to the nuclear instruments for each of the five insulations. One

exception to this was that there were no S values less than 0.0 for glass

fiber insulation for the capacitance instruments.

Of all the insulations, glass fiber S values appeared to be the most similar

for the capacitance and nuclear methods. This trend is indicated by the

results in table 9.

8.4 SHAPE OF DATA SETS AND THEIR FITTED CURVES

Many of the Ry - Rj) vs. Vp data sets and their fitted curves tended to

be concave downward for the capacitance method (figures Al through A36,

appendix A). This is in contrast to an almost linear (i.e., slightly con- cave downward), linear, or concave upward trend for the nuclear (figures A37

through A60) and infrared (figures A61 through A69) methods. These trends

are supported by the higher percentages (11 to 22 percent) of S values less

than 0.0 for the capacitance method as compared to the nuclear and infrared

methods, for which there were no S values less than 0.0 (table 9). The concave downward trend was particularly strong for the capacitance method

for perlite and fiberboard insulations (again note the relatively large

percentages of S values less than 0.0 in table 9).

For specimens containing perlite and fiberboard insulations, many of the

adjusted NDE response versus moisture content data sets (figures A13 to

A24, appendix A) for the capacitance method showed the following trend:

the adjusted NDE responses rose sharply at moisture contents of about 10

percent or less and then leveled off or decreased with increasing moisture.

Thus, for these cases, it was not possible to distinguish between relatively

low moisture contents and larger moisture contents. The trend of flatness

due to off-scale responses for instrument C2 with specimens containing

perlite (figures A15 and A16) and fiberboard (figures A21 and A22) has been

discussed in section 5.5.2.

8.5 INTERPRETATION OF EFFECTS AND TRENDS AS RELATED TO PERFORMANCE

CHARACTERISTICS

As discussed in chapter 4, this study was primarily concerned with the

evaluation of the two performance characteristics:

o quantitative detection of the minimum moisture content (TVP)

o quantitative detection of the moisture content beyond the TVP.

These two performance characteristics were quantitatively evaluated for

the three instrument types through the use of the indicators TVP, S, and

SS. When using the indicators, one instrument or construction variable

52
combination may have a more favorable indicator value than another

instrument or construction variable combination. When interpreting the

indicator values, however, it is important for the user to recognize that,

although one instrument may have a more favorable indicator value than

another, both instruments could possibly be used to detect or determine

moisture content. Also, depending on the use, only the performance

characteristic for the minimum amount of moisture (TVP) may be important;

in this case more significance should be given to the TVP indicator than to

the S or SS indicators.

8.6 ADDITIONAL CONSIDERATIONS- "ON THE ROOF" UNCERTAINTY

The reported trends are for a controlled laboratory study designed to

determine the effect of insulation type and thickness, asphalt thickness,

and deck type on the ability of the three NDE methods investigated to

quantitatively detect and measure the moisture content. Thus, the uncertainties associated with the construction variable effects were, in part,

accounted for in a systematic, controlled, manner. On an actual roof,

however, the uncertainty associated with one or more of the construction

variables (effects) may not be able to be accounted for easily. For example,

it is well known that nuclear instruments are affected by any hydrogen bearing material, such as asphalt. Thus, variations in asphalt thickness can cause changes in the nuclear instrument response (see table 4). In this

study, however, asphalt thickness was (at least in part) accounted for by

subtracting the "room dry" response from the "wet" response (Ry - R^)* On

an actual roof, asphalt thickness may not be able to be accounted for and

could be misinterpreted as moisture. Thus, the asphalt thickness variability may need to be measured by taking cores. The uncertainties associated

with the construction variable effects for each type of instrument can accu- mulate on an actual roof, unless they can be accounted for by coring, for

example. In reference [3] , a thorough discussion of the advantages and

limitations of the capacitance, nuclear, and infrared methods is presented.

Thus the information in reference [3], which is not in this report, needs

to be combined with the information presented in this report with regard to

method choice, usage, and data interpretation and analysis.

The authors acknowledge the financial support for part of the data analysis

from Mr. Harold Berger, NBS Office of Nondestructive Evaluation, and

Dr. Robert L. Alumbaugh, Materials Science Division, Civil Engineering

Laboratory, Naval Construction Battalion Center.

The authors would like to recognize the helpful statistical consultation

and input of Dr. James Filliben. The authors acknowledge the helpful suggestions of Drs. James R. Clifton, James R. Harris, and Mr. William C. Cullen

who reviewed this report. Ms. Ulesia Gray is thanked for her role in the

typing and final preparation of the manuscript. The authors appreciate the

long hours and the cooperation of Messrs. Michael Glover, Jessie C. Hairston,

James C. Owen, David K. Ward, and Nathaniel E. Waters in the preparation

of test specimens, conduct of tests, and collection of data.

53
Mr. A. Phillip Cramp is recognized for his supervision of the fabrication

of the roofing specimens. Mr. Bernard J. Hunt is recognized for his design

of the environmental chamber used to introduce moisture in the test specimens.

Mr. Nathaniel E. Waters is also acknolwedged for his efforts in reducing and

preparing the data for computerization. Ms. Catherine A. Scarbrough

deserves special recognition for her role in the computerization and plotting

of the data. Finally, the senior author would like to express his sincere

gratitude to his wife, Marlene Knab, for her continued help and encouragement

throughout this project.

54
REFERENCES

Busching, H.W., Mathey, R.G., Rossiter, W.J. Jr., and Cullen, W.C.,

"Effects of Moisture in Built-Up Roofing — A S tate-of- the-Art Literature Survey," National Bureau of Standards Technical Note 965, July

1978.

Knab, L.I., Jenkins, D.R., and Mathey, R.G., "The Effect of Moisture

on the Thermal Conductance of Roofing Systems," National Bureau of

Standards, Building Science Series 123, April 1980.

Jenkins, D.J., Mathey, R.G., and Knab. L.I., "Moisture Detection in

Roofing by Nondestructive Means — A State-of-the-Art Survey," National

Bureau of Standards Technical Note, in press.

ASTM "Asphalt-Saturated Organic Felt Used in Roofing and Waterproofing,"

ANSI/ASTM D 226-77, Annual Book of ASTM Standards, Part 15, Philadelphia

PA., 1978.

ASTM "Standard Specification for Asphalt Used in Roofing," ANSI/ASTM

D 312-71 (Reapproved 1977), Annual Book of ASTM Standards, Part 15,

Philadelphia, PA., 1978.

Honig, A. et al, "Comparison of Commercial Portable Gauges for

Radiometric Determination of Building Materials Density and Moisture,"

RILEM, BRNO Technical University, Report VUT-69-D-1, 1969, (Working

Copy)

.

Mandel, J., and Stiehler, R.D., "Sensitivity - A Criterion for the

Comparison of Methods of Test," Journal of Research of the National

Bureau of Standards, Vol. 53, No. 3, Sept. 1954, Research Paper 2527.

Lashof, T.W., Mandel, J., and Worthington, V., "Use of the Sensitivity

Criterion for the Comparison of the Bekk and Sheffield Smoothness

Testers," Technical Association of the Pulp and Paper Industry,

Vol. 39, No. 7, July 1956, pp. 532-543.

Stiehler, R.D., and Mandel, J., "Evaluation of Analytical Methods by

the Sensitivity Criterion," Analytical Chemistry, American Chemical

Society, Vol. 29, April 1957, pp. 17A-19A.

55
GLOSSARY OF TERMS

Adjusted NDE Response = "wet" NDE response minus the "room dry" NDE response

Adjusted NDE Response vs. Moisture Content Data Set = set of "wet" minus

"room dry" NDE responses vs. moisture content

Adjusted NDE Response vs. Moisture Content Fitted Curve = refers to the

quadratic best fit curve fitted to the adjusted NDE response vs. moisture content data set.

Construction Variable = refers to the composition of the specimen (for example,

insulation type and thickness and asphalt thickness) and the type of

deck (concrete or steel) the specimen was tested on.

Construction Variable Set = refers to a combination of one or more construction variables

Moisture Content = percent of moisture by volume of Insulation (see Vp)

Moisture Content Range = Ranges of moisture content: 0 to 10 percent; 10 to

20 percent; 20 to 30 percent; etc. used in the determination of S values

(see eqn. 8)

NDE = nondestructive evaluation

"Room dry" = refers to moisture condition in insulation in roofing specimens

at approximately 70°F and 50 percent relative humidity

"Room dry" NDE response = NDE response obtained for roofing specimen

containing only "room dry" moisture

RSD = Residual Standard Deviation = measure of scatter (eqn. 3) of the

adjusted NDE response about its fitted curve

A(R„-Rt.n^^^

Sensitivity = ( W D)est )/^gp

AVp

Sensitivity vs. Vp (S vs. Vp) Curve = refers to the sensitivty versus moisture content curve

Threshold Moisture Content = the minimum moisture content which an instrument

could detect. Defined to be that value of the moisture content (Vp) at

which the fitted curve [(Rw~RD)est» ^qri* 2] deviated from (exceeded)

the zero ("room dry") response by 3 residual standard deviation (RSD)

values.

56
GLOSSARY OF TERMS (Continued)

"TVP Not Attained" = refers to the case when the deviation of the fitted

curve [(Rw~RD)est^ from zero does not reach three residual standard

deviation values.

"Wet" = refers to specimen containing induced moisture

"Wet" NDE response = NDE response obtained for roofing specimen containing

induced moisture

57
NOTATION

BUR = built-up roofing

C-p = total thermal conductance (eqn. 13)

Hg = exterior surface heat transfer coefficient (eqn. 13)

Rj) = "room dry" NDE instrument response

Ry = "wet" NDE instrument response

R^ - Rp = adjusted NDE response

Ry - Rp vs. Vp Data Set = adjusted NDE response versus moisture content

data points

~ ^D ^s. Vp Fitted Curve = adjusted NDE response versus moisture content

fitted curve

(Ry - RD)est ~ estimated or predicted response based on the adjusted NDE

response versus moisture content fitted curve (eqn. 2). Values of TVP

and S were based on (RyRD^esf

RSD = residual standard deviation (eqn. 3)

S = sensitivity (eqns. 6, 7, and 8)

S(MAX) = S value in the moisture content range preceding the range containing

the maximum moisture content. (S values were not computed for moisture

content values exceeding 60 percent.)

S(MID) = average of the S values for the moisture content ranges between

the range containing the TVP and the range preceding the range

containing the maximum moisture content.

S(TVP) = S value for the moisture content range in which the TVP occurs.

S vs. Vp Curve = sensitivity versus moisture content curve; refers to the

S value plotted at midrange of each moisture content range

SS = slope of the S vs. Vp curve (eqn. 9)

Tg = interior temperature of the insulated box used in the infrared

thermography testing and analysis (eqn. 12)

Tp = reference pad or room temperature (eqn. 11)

Tg = surface temperature (eqn. 11)

58
NOTATION (Continued)

TVP = threshold moisture content

-, ^ . , . , . ( Volume of Moisture ^ „ mn Vp = moisture content by volume of water m the insulation = ^Tr~-x T~t \ ;

' ^ . Volume of Insulation

. . , . ( Weight of Moisture ^ ^ 1 nn Wp = moisture content by weight of insulation = ^„ . , ^—r~r :; :—

^ y o Weight of Dry Insulation

AI = change in intensity used In infrared analysis (eqn. 11)

59
" a

t>

O

u os

t-l csi ^ c c c

<M r-l CS f-H

XI 1-1 .-1 1-1 i-H OH p.

u

>^ 3 XI

4-1 4J CO •H tn 4J Td •H J2 •H o tu a B (U 13 3 to

dj o

Xl 4-1 1 •H> > c tu o c

T3 4J •H CO

to 4J

u

to XI o <u B

•H 3

to 8

to &^ c

•H o •H Q) > to .c

M-4 4-1

n 13 o

U-l &o to o CJ

>-t to 60 4-1 •U 0 1-1 V4 CO C O tu to

to cx

4-1 tn >, >^ to § u 0) T) VI T) a

ui to >s IV 10 E J3 4-1 4J CO

(0 •H to tu

to

X 4J tu

B

O c l-l t4^ T3 u IV 4-1 vO

tu a. o M-l f-H c Q. u to O

•H to lU to

B

M-l o. 3 4J

O

(U 4J x: T3 to (« 60 60

a

to c *H

V

to *H tu CO c -a o 3 CO

C o tu CO XI

(U •H CO >. O 4-1 CO M (K u -H lU T3 o

<u T3 i-i a. C 4-1 00 o « (V J3 c u 11 cu •H s: 4-t M-l s 4-1 to c o c o e • (U o o tu c 60 o u

•H

u 4J o c l-l 0

4-)

a -H •H IV

H

to 4J

O 4-1 CJ to

a o

to to o to to tu

a

u c r-H C4.4 14 1 to tu lU tu 3 to 00 > B 00 V4 to 4-1 u B

•H to 3 C 4-1C •H

t4-l

O 14 4-1 -H to •H 01

C o (D 0 to s: 4-1 01 O. 4J •H t4H o. 3 c 4J u VI Vi o o to o U-l c B to ^1 u o V t4H o tu tv CO •H o 4-1 uh B to a tu o O 3 tu M 01 *H l-l u •o 4J 3 60

t4-l lU o o 3 j= 4-> CO

U-l XI <u •H > 60 COu

<u

B u-l 4J o •H •H 0) o 3 <ll to X lU o >

oiu s <

to Xi o T) lU t4-l 60 x:

60
c

<u CO • a

a •H C -H CNl CT^ CN O m CO X 00 00 CN 0^ Csl (3N in CO C3N CN m 00 0 X «> sD OS O in 00 00 vO CN CO 00 X CN 00 00 00 in X X 0 CO OS 00 < CN CO in CO CO o 0) o . H a

I/; •H 60J= > H <

CN CM m CO CN CM CN Csl CN CN CN CM CN CN CN

C

o (n /-N •H CO • CJ o u CJ CJ 0 u CJ CJ u (U c in O CN CN CN m CO X X 0 0 0 0 0 OS CO 00 0 X 00 00 CO Os X 00 OS

nl C -H 0^ (» O 00 0 0 0 0 0 0 0 0 0 0 0 OS <t OS 00 OS 00 as 0 00 3 O • o O O o o o CN CN CN - CN CN CN - -' - CN 0 0 0 - - 0 0 CM 0 CN 0 -

C/} •H 60 C X > M H <

CN

(U CO 4-J Pu TO CN O -X in CO CO 00 CJ% in CM X in CN

CO CO X -a- in > 4-J

1 1 1 1 1 1 o CN CM CN CN CO CO CN CN u 60 o iH

(LI 3

Uni

Avg.

(/) ^ .H CO • ID 11 c CJ^ m 00 CO CN 0 00 m 0 in OS -a CN CN 00 in CN X 00 D

> C -H <f <r <r CO so \D in m 1^ in CO CO <f <f CO < CO in <f <f <r OS <• in CO 1 1 1 1 1 (0 1 j 1 1 1 U O ' O o o o O O o o o 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

CJJ •H 60 X > H <

l-l CN

<u OJ CO c Cl, (U U-l Vj ^ <f CN u 4J < J3 CN CN X 0 CM in 0^ 0 CO CO CN 0 X 0

x>B 60 4-1 ^

CM CM CN ro m CO CN CO CO CN CO CN CM CO CN CM CN CO CO CO CN CM CN CM

<a •H •H . C 60 3 ><

<u CO ^

c (fl • a (U c u C -rt 00 CNI (J^ in CO <r CO <r 00 CN 00 00 <J^ 00 CN 0 in X in <r X in X CO CO CX! C

CO <r <f <f in CO CO CO -a- CO CO CO CN CN in CN CO CO CO in csl -a- CO CO -a- <f CO CO <r e o • a; •H 6C O O o o o o o o o 0 0 0 0 0 0 0 C 0 c 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

J= > H <

CO CO

cn •c o a o T5 XI 13 T3 13 T3 13 13 13 13 13 13 13 13 13 13 0

rH o S-1 V4 u u U u »H u U U IH u U U u >u >u i-i « c CO CO cox CO CO CO CO CO CO CO CO CO CO CO CO CO CO (0 CO CO CO CO CO ^ T3 •O a a 13 T3 >i13 "O >^13 c > 13 13 >> 13 13 13 13 13 •D

o. u C C c > > > c C > > c tn C > C C > c C C > C c > C > > c: > 13 C C C c c

0] •H CO CO CO a CO CO CO CO CO CO CO CO CO CO (0 CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO (0 < 4-J 4-1 4-1 <u D (U 4J 4-1 1) 1) x-t 4-J 4-1 U 4J 1) 4H 4-1 u 4-J u 4H 4-1 u 4-1 1) u 4-1 u 4H +J 4H i-i 4-1 4-1 H C/2 CO CO X CO CO 3: c/:) C/D CO CO CO CO c/: X. CO X c/: CO a: CO X. 3: CO X C/^ CO CO CO CO CO

CO

CO (5c C • rH rH rH CN CN CN - rH rH CN CM CN rH rH CN Csl CM CN CN rH CsJ CN CN ^ c

E O tH O •H

Th

CU OJ

)< l-l u IH u u 11 u 1) 1) u c c U U

c 11 D u U cu D u 11 11 cu 13 -a 13 13 c^ c C c^ c CO (0 <u o ,0 X X X X X X X X U IH U )H 1; 1) D D n u X X X X u u

•H *H •H •H •r^ •H •H •H CO CO CO CO CO u >-l IH U l-J iH 4-1 4J •H u u

4-1 tK (i- tl. u CU U u u 11 U 0 0 0 0 >s >s >S >s >s >S 11 1) tu U >s >s

to 11 4J 4-> 4H 4^ 4J 4-1 4-1 X X X X X 4.J 4-1 4-1 4-1 4-1 4J Vj 4-1 4-J u 4-1

Cfl CO C/3 CO CO CO CO CO (fl CO •H -H *H •H u u u u 1-1 l/l CO CO CO (/) CO 3 3 CO CO CO CO > CO CO (fl CO CO CO CO CO CO CO rH (-H iH u u u u 1) >s >s >^ >s >s >s >s >s CO CO >,

(0 H (0 CO (0 CO CO CO CO CO CO CO V4 l4 u iH u l4 X X X X X rH r-H CO CO l4 V4 c rH rH D 1; 1) u 11 U u •H •H •H •H C 0 0 1) (U 0 0 o O o o o CJ O CJJ Ou Oh P-. 0-. PL, Cu IX (1. [1. fc. [JH Dj CU CU CU CU Cu 0 C.5 CU Cu d.

en u 1) U 11 u 0

e CNl Csl -a- <r 00 00 CN X X 00 00 CO X C3S CO <r X 00 CT^ CO CO in CO in in in in m in X X in CN csl CN CO CO CO CO CO <r <r -J CO in in o O X

<u

CI. c«

CO to

CO CO

<U 11 U U 4H 4-1

CO to X X

& a

to to

CO (0

o- a

>-• lu u u

4-1 4-1 c: c:

CN CN • -H

4-1 (0 M to 00001 O X 4-1 4-1 13 13 4-J 3 3 u u o 1> O O CO CO o to X X (0 ra e to <: <: cc cc CO cc

CO X O U 14H

61
Table 3. Comparison of Membrane Weight Per Unit Area for

"Standard" and "Heavy" Asphalt Thicknesses

Insulation Type and

Nominal Thicknness (in.)

Asphalt

Thickness Unit

Weight Per

Area (Ib/ft^)

Glass Fiber 1 Standard 2 .12 (1)^ 2.19 (2)

1 Heavy 3 .24 (52) 3.28 (4) 3.30 (54)

2 Standard 1 .97 (6) 2.20 (56)

2 Heavy 3 .26 (8) 3.62 (58)

Perlite 1 Standard 1 .79 (11) 2.01 (62)

1 Heavy 3 .56 (14)

2 Standard 1 .92 (16) 2.14 (66)

2 Heavy 2 .34 (18)

Fiberboard 1 Standard 1 .20 (21) 1.49 (658)

1 Heavy 3 .01 (23)

2 Standard 1 .60 (26)

2 Heavy 2 .34 (29)

Polystyrene 1 Standard 2 .10 (31)

1 Heavy 3 .82 (34)

2 Standard 1 .36 (36)

2 Heavy 2 .49 (39) 3.50 (38)

Polyurethane 1 Standard 1 .89 (41)

1 Heavy 3 .14 (43)

^ Specimen numbers shown in parentheses; these specimens were tested with

capacitance and nuclear instruments.

62
63
OD a IT *n o N ry o M w o — — o

C < If 1^ — O N M -O O — O O O ooooc — — o — — — oo — — ooo-- — — oo

(D in O N

mm OD

Ajfyfn — — — o — I m in ffi fy — f

' 3- (7> tfl — N U) 1

I n -c lO 0- . V ry v «

' * CD O N

m IT - * *

• » •

n o N <j -

(B « * in in - o - o - ,0(3P^,0O'ncy(yini0f*>'0(Doo'CO'O*f»>cDo^na)*f\iNtJi — in fvjofyoo — — — coooo — ooooooowowoo — — o — o

N a -

s « fn o o o

O (C * « O 4- M

O O O O

o o o o o ma * < ^ (J. OD K

(MO O O

ainnjin — fM — o'M'no«r\j<t«t\join^-riN«'«io*<vjfo<M(Dsa> — ow«

.f\j-. — f^Jlnl^Jln'^^*|^J»'^J — ooooo — o — o-* — inNinNfM'^iMnvD'D —

- cc s —

a in — CD o o o o

— ina)n«i;ii^ OtyrOOin^JMCT- — <f-^(E* nn — — — — rj — —

O O f\J '

O (D — "O — N Pd I © «r <D * I

oj in I 1 o in lO in '

3} 4 A O iS

- U- 1

in —9^1

O (E Q O

<D in * oj o

O CO « o

iM O — O O —

J. &

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O O

^ i£i f\j cy. r- o

f\J rvj - <t o -

n N cc O O IN o o o

CD n a U

o c?' in *

> O O O

in N

o o

lO ^- N — ry .

I O •*) — — cc M I

I (y - 4» f*. I

17' * CT « O (7> I

ZZ_I_JZZZ_I_I-I^Z-J-JZZ^_JZZJ_1Z_JZZJJZ-IZZJJZ-*Z_IZJZ-JZ_(ZJZZ_J_JZJZ_I

uui/ii/iL'u»u</i'/iv^uuwtnouu^inL'utrtinuv>Ltuv)(nutnuy(rtwuinu»nu(/)u<nu

. D O > > *-

I I/) i/l X X X , iQO)->->->-UOQ!J>>-UOQO>>OOQO>->-00>-VOQ>->-OtJ>->->->JQ>->- t->-^>>>t->-r->->>t-^-r-r->^*"f-^r->;>t-^j»>e-»->>h-t->^>>^t->>

I wj u) X X X X yi in u' w 1 X «n in vt ui X x w u) in ui x I ui m x x wi w x x u> w x x x x w) uj x x

I M (\j — — — I

c e

a) =tE

) M

O W U o

dJ (0 iJ 4-f

64
SOKMARY CF SPECIMENS. CCNSTRJCTION VARIABLES! 1HS0, TVP, VALUES FCF THE CAp*ACITANCE AND N'JCtFAO I N S T "U^F ! T S SPEC IWEN

"NO. INS» ASP, DECK

INSTRiJMENT Nl INSTRJMFNT N2

TVP

1 OF

a GF

4 GF 1 S« GF 1 52 GF I « GF 1 54 CF 1 5 2 GF I

5S GF 2

5i GF 2 SB GF 2

I 1 PR I e? PR 1

I 1 fR 1 62 PR I 1 « 1 14 PR 1

1 6 PR 2 6 6 PR 2

1 6 PR 2 66 PR 2 IH OR 2 in PR 2 ?i rt) I 658 Fa 1 21 FB I 65a FS 1 ?3 FT 1 23 FT I 26 F8 2 26 Fl 2 29 FH 2 2R F'* 2

31 PS 1 31 'S 1 34 PS 1 14 PS 1 36 PS 2 36 PS ? 33 PS 2 39 PS 2 38 PS 2

3^3 PS 2 4 1 OU 1 4 1 PU 1 4 3 PU I 43 P J 1

STD

STO

STO

STO

l-VY FV Y l-VY FVY

STO

STD

STO

STO hVY

FVY FVY

FVY

STD

STC

STD

STD

H VV hVY

STD

STD

STC STD HVY hVY

STD STD

S TO STO FVY hVY

STO

STD

t-VY FVY

STC

STC

hVt FVY

STC STD FVY

hVY HVY

HVY STD

STC HVY

HVY

CCN CCN

STL

STL CCN

CCN

CON

STL

STL STL CCN

CCN

STL

STL CCN

CON

STL

STL CCN

CCN

STL

STL CCN

STL CCN

CCN

STL

STL CCN

STL CCN CCN

3TL STL CCN

STL CCN

STL CCN

STL CON

STL CCN

STL

CCN

STL CCN CCN

STL

STL CCN

STL CCN

STL

3<).42 54.81

34.4 2 5H.a 1 45. 70 46.50

37. t5 45.70

46.50

37. t5

2 1 . <) 5 37 .24

21 . siS 37. 24 34.35 29.25

34.35

2^). 29 44.60

70. 13 39.20

70 . n

44. ( 1 44 . e I 24.7 6

29 .92

2<<.92 25. J 1 32.24 25.3 1 22.34

39. 77 39. 7 7 30. 36 30.3 6 20 . 44 20.44

50 .5 4 50 .54 ee.25

86.25

36 . 0 1 36. CI 33. 14 28. El 33. 14 2S.e 1

1 7.60

28. 86 15.21

13.04

4. 15 28 . 68 21.33

18.36

3 1.02 7.08

6.24

I 1 . 04 13.96

14.13

19.17

14 .93 5.90

I 5 . 3 b

14.15 15.24

9.62

J. 03 10.39 8.49

16.84

1 9.55

3.17

.227

. I 89 .226

.208

. 124

. 143

. 1 95

. 183

.291

. 1 94

.491

. 1 88 .423

.171

. ?0<. .221

.3 70 .281 .503

.420 .346

.4 17 .246

. ^ 02 .631

.6 34 .9V7 .503

1.046 .528

.846

.565

.69 3 .305

.167 .417

.558

.8 10

.4 13 .557

.381 .468

.222

. 1 65 .323

.4 36 .447

.85 1 .356

.480

.5 11 .311 .283

.374

.227

.205

.4 31 .291 .39 3 .342 .228

. 1 77

.35J .553

.9S1

.34 3 .421

. 1 59

. 1 65

. 72 7 .451 .312

.437

.332

. 1 88 .288

.313

. 246

. 288

. 068

. 192

.216

.458

.172

. ISO .23 1

.288

.35 9

. 163

. 439

.267 .209

.152

,626 .297

1 ,073

. 45 1 .774

.050

.461

.9 38 .613

,679

. 167 .283

. 548

1 .151

. 356

. 372 .304 .375

.097

. 1 66

.631 .455

,177

, 591 ,257

,589

,362 .353

.093

.202

19.25 25.27

1 1.95

IC. 21 30.08

1 7, 72

I ( , 91

I 7,92 13.00

1 2. 66 9.46

2 3.29

e. 85 10.10

2 4. 59 17.03 12,26

14.26

19.02

17.29

1 e .49

I 2. 33

3f . 08

1 7.54

1 1 . 30

1 7,20

e, 14

1 0 , 87

2 3,56

2 3,16

1 4, 59

I 5, 59 12.63

11.11

2 4. 60

1 1 . 58 23.69

1 5.50 14.53

1 0.48 15.70

7.87

1 2.54

27. 05

2 I .08

1 1 .75 32.21

1 7.85

11.25

23. 1 3 18.89

30,90

6, 31 23, 30 25,27

27,93

25.4 1

12.12 14.63 8.79

14.96

11.26 13.24

.327

, 194 ,167

,263 ,147

, 361 ,253 .167

,298

.705 ,499

,237

,304 ,289

, 368 ,478

,421

, 345

.621 ,911 .24^ ,333

,437

.462 1.627 1.118

.962

.503

1 .026

.740 1.218

.582 ,2(8

.591 .602

. 3H9

2 . 840 .720

.975

.888

,51 7 ,349

, J30

,22 7 ,605

,235 1,112

1 ,852

,783

,240

,46 1 ,247

,472

.406

, 1 89

,288

,418

,636

,783

, 794

, 486 ,314

. 356

1,378

1 . 0»5

.608

.438 3.038

1 , 1 27

, 486 .432

.255

. 1 98

. 830

. 378

.0 33

.546 .473

. 357 .404

.407

.342

.249

. 156 .2 30 .538

, 322 ,235

, 462

,64 3

, 331

, 468

. 529

• 851 .463

,944 ,677 .322

, (.35 ,192

,251

1 . 999

1 . 637 1.687

1 . 666

.931 .963

1 . 337

. 966

1 .267 .613

.487 3.236

1 .535

.957

. 793 .456

.515

. 1 79 .170

1 . 355

. 521

. 954

1 . 375

. 768

.631 .699

.24?

.403

3 No. = specimen number; INS. = Insulation type: GF = glass fiber, PR = perlite, FB - fiberboard, PS = polystyrene,

PU = polyurethane; 1=1 in., 2 = 2 In.; ASP. = asphalt thickness: STD = "standard'; HVY = "heavy"; DECK = deck used: CON = concrete, STL = steel.

Maxiinum moisture content induced in the specimen.

^ Three times the residual standard deviation.

^ Threshold moisture content.

^ S(TVP) » S value in the moisture content range in which the TVP occurred; S(MAX) = S value in the mclsture content range preceding the range containing the maximum moisture content; S(MID) = average of the S values for the moisture content

ranges between the moisture content range containing the TVP and the range preceding the range containing the maximum

moisture content.

^ Data not included because the quadratic fitted curve was inappropriate.

* TVP not attained up to the maximum moisture content of the specimen.

65
X 1—

1—

CM < m vO 1 1 1 O 1—

O 1 1 1 • • • • • • 1 1 1 O o O o o o

> N c CNl in o

1 1 <r CO 1 1 1

1 1 CNI 1 1 1

1 1 • • • 1 1 1 CO o o o o

D-i a^ CN <t in o

> o ON O CO CNJ 1 CNI o o CM 1

1—

o • • • • • • 1 • • CO o o o O o O .-H

tj 00 CM <f CO '—

> .—

1—

00 Csl CN in in

E-i CN OT CNI

ro 1-H CO 0^ m 00 in CM —

m O 1—

(

in in 1—

CO O o O o o o o O o

m o o O o o o o o o

B

3 ^

<f o 00 o CO <f

•H —

X .-H <r CM 00 CM

CO P-i CO ro CO S >

in. CM

C CO CO CO

QJ q; a ^

o

5-1 Sj !-i QJ 0) QJ

QJ QJ QJ d 3

Q) QJ Q) o •r-l H •H U \-i •iH ,—1 Pi- ^ QJ QJ QJ >^

4-1 rt) 4-1 4-1 4-1 4-1 4-1 4J

CO C C^) co •H •H •H CO CO CO CO CO CO I—

t—iH >~. >^ 3 e CO CO CO u S-i !-i i-H iH I-H CO o 1—1 1—

r-\ QJ Q) QJ O O O

M

O o P-i P-I P-I P-i P4 P-I

0)U t—

I—

X- rH rC r3

CO QJ J-l 4-1 QJ 4-) 4-1 QJ 4-1 4-1 4-1 > o o > o O > o O

>-i CO o o CO o o CO o o

3 U E e U E E U E E

CO CO CO o CO CO CO CO

c

E

•H • 1—

1—

m in CO in

CJ o <r <3- in in

d) s (—

(

1—.—

a

CO 66
TVP

for

All

Insulations Not

<

10%

<

20%

Attained

19

44

38

52

87

1.8

46

72

9.3

39

68

16

57

91

0.0

63

89

0.0

60

90

0.0

TVP

for

Polyurethane

Not

<

10%

<

20%

Attained O O O CO

in iri

o

O O O O

o in in o

o o in in

o o o

o o o

o o o

O in m v£)

TVP

for

Polystyrene

Not

<

10%

<

20%

Attained o o o jn

o o o o

o o o fn

-d- oj

0

OOT

59

0

001

09

0

001

OZ

TVP

for

Flberboard

Not

<

10% <

20%

Attained o o o fn

o O o \D O O 00

o o O in o^ o^

o o o

o o o o o o

O O in 00 r- r--.

TVP

for

Perllte

Not

<

10%

<

20%

Attained

30

70

30

50

100

0.0

58

92

0.0

47

88

8.8

83

100

0.0

92

100

0.0

88

100

0.0

TVP

for

Fiber

Glass Not

<

10%

<

20%

Attained

11

50

22

44

78

0.0

22

50

5.5

26

59

9.3 o o o

o o o

r-- er> r- ^£5 v£)

CN eT> o rsi <n

Instrument CI C2 C3

Avg:

CI,

C2,

C3

2 2 2

00><

67
Table 8. Percentages of TVP Values Less than 10 percent, 20 percent, or "Not

Attained" and Percentages of S Values Less than 0.0 and 0.2 and SS

less than -0.015 and 0.0 for the Infrared Instrument

Insulation

Indicator Glass Fiber Perlite Polystyrene All Insulations

TVP < 10 percent 33 67 33 44

TVP < 20 percent 33 100 33 55

TVP not Attained 0 0 33 11

S < 0.0 0 0 0 0

S < 0.2 43 33 50 38

SS < -0.015 0 67 0 25

SS < 0.0 67 100 0 63

68
(0C cn o

•H CO t^

4-1 C» 00 CN

tfl

V o i-H

COC o

•H • o .—

c^l

—

00 o o o

iH OJ '—

tH

V

<S

C-si CDC o O CNl CNl in o

<u CO

O o\ CO CT> '—

o —

o <u

4-1 C4-I >-l •H 3 o >—

o C/) • •

tfl r—

o o o ON <r o o o

(X o CN .—

tfl PhV

CJ

>-l O

MH tuc o o 00 ON CN o

CM CD o <! CN

—

CN • t-i v '—

o 4J o CO •v >. c CO o 00 00

(fl CO • • t—

o <r ONO o O o CO o '—

'—

• 4-1 V o (=! OJ c e

CO Csl cn o CN ^

4-J !-i o C!N 00 o CO CO in in in

CO

C

u o V

CDM o ,o

(U

m

U

1-4 !-i (U

Cfl C/3 pQ o

CO CD •H • 0) iH o f-H CN <r o o o 3 O cn CN CN

I—

DV

cfl Z >

TSC CNl in '—

tfl M-l o o CNl '—

CN in

O Q) CJ^ o 00 C7N

4-1

v 1—

CO

O •H

a) I—

60 ^

cfl in CU o 4-1 • c o in in

O o o

<r I—

c^ o^

PM

CD o o CO ON 0^ ^ CM

•H

V

<U o

CO

tfl cn CO o H tfl • T—

o o o O o o o o

CJ

V

t^

tj)

4-1 CN CN

t^

(Us3 CNl ro CN

!-i cl; C_J

U CLJl Z :s

4-1

Cfl cM 60 60 > >

69
CO o

c • o o 00 in -* in o •H 00 00 00 in CN -a- u 4-1 V

o

iw i-H lO c o o

M • • • • o o r

fO ON o

I-H 1 CO ro cn

1—

<: \/o

c o o O O o in o m

« o O O o in u

o 4-1 0)

)-< CO 3 —

to o o o o o o o o 1—

• • • • • • o o o o o o o o o

1

o

o o ON r- o o o in c o 00 00 ON 1^ in u (U V I-H 0 ^4

<+-( 4-1 m

CO

CO >^ o o o O 1—

o o o in o o o in

Pi 1 CN] CN '

' N/o

o o o o o o o in

T3 o o o o cn <r M V

u nj o o

<4-( u-1 CO O CO Xi • •H o o o o CNl o o o

1 o ON ON CNI v

o

o o o CN in ro o o <3N ro in

\/ u 4-1 o •HH

l-i CO HI o O cn

CO • • • o 0^ o CsJ o 00

1 CM '—

in cn V

o

1-1 o O in CTN 00 o <f

0) in in CNI u N/ 0 H

<^-l in

CO

CO cn O ON o o O CO • • • • • (—

o in CN o o o

O 1 —

V

c_>

4-1 c CN CNI <u tj> z

e

Du

4-1 o O CJ) U z z

(0dM 00 ci > > < <d

70
CO&

tn <

>

o

a) W

w

c

o

•H

<D

4-1

O

e

o

o

U3

o

ou

CO e

0) 3

P^cX)PJO^p^—^fIHCJ^P^00CL|O^Ci^CJ^ «< •><; "<

(H (=: C c i-i iH iH O "O "O "O " U •'4-1 •>.M »•

00 CP> O •* CT> •• •» o% •» o^

: <: <;: -h: <;: <: <: <; —( .—i ' >—i <; cm ^-^ i—i ^-^ i—( n--- cn ^—

CO ^

PnOOCLl-a-tlHCNCljLJ-l

"cr. -00 •-a^ •-00 O O O 4-1 4-1 u -cj -u -co - -o "00 '•—I -r-~ 13 CTv >^oo >^oo >.oo >>aN 4-i<;><><><:><

CO Lo cc a^

Oh 0^ fij 00

- <: " <C

4-) - > -

CO -O- ffi 00

-CT^ -00 :<;:<;

o

- <: > -

- o

a

-O CO

t3 o

Ph >—

- <

4-1 -

CO CM -O

Cl2 O CO vO CO

Ph 00 CXj CTi Pi 0^

- <: - < - <

O - O - 4-J - U 00 u <)• CO un

— — o^ - CT^

: < : < : <

V—V CO o

PH-d-pHOPnroPHtn

-00 "CO -co C < C<Ci-l<rH<:

O O 4-1 4-1 U -U -CO -CO -

- o •" " •- < >>00 >^C3^ r-~ >-.00 >< ><4-l< >< V—' ^ —^ CO 5;;; ^-^

OS t3^ CO r~- CO 0^

Ph r-~ Ph Oh <3N - < - < - <

4-) - > - 4-1 - CO 00 K VO CO 00 -r^ - CTn - <3^ :<:<:< ^ -H CN ^—

CN

ua

01u • uo 0)

CJ f—

o ^

CO CO 4-> c c

•H •H

Wl •o

•

OJ 0) 0) <J to to c 3 to 01

t-1 (U

0) to to

M-i o to

C4-I s

•H 4-J T3 4-1 to o

•U CO 0) e M-J to • 0) >4-l o w e 0) •H to to

^-^ (LI to a> •H c

C (U 4-) 6C u

•H •H 4-1 ^ tn CJ

4-1 0) •H

»^ o 4-1 CO •H i-H X to to 3

3 OJ o a

Vj CO to o CO to 4-1 •H o

13 )-l I—

C CO Q0) CO >

4-1 Pi

U3 3 > •H to O

iH CO •H

tu 4-1 to

0) O >

(J 3

CO c; CO

4-1 to to 01

tu 4-1 c x:

I—

o 4-1 J2 c u

to o u

•H •H >-l o

>-i 4-1 o U-i CO to y-i > CO 3 to u

C to c tu o C o

•H •H •H e

4-1 4-1 3

CJ to c

3 •H

)-i o > 01

4-1 <D 0) l-l cn -a >-l 3 c ty; o t4-f •H u o <

to J3 u

71
oo c»

m < CO in <t

O CO o r-* CX5 00 00 UO CM o- vO V

COO «^

H

C cn

CO o w

m

M

X c i-H CD 4-1 CO O 4.1 •

i-J to •H o ^ O r~ CO CJ\

O in in

CO

O 1 CO CO CO fO CM

Pli (U CO > hJ CI.

V

CO CJ

O }-l CM o • CO <4-l o rH

O C30 I-H V£) CO 00

C Oi <X) 00 v£) CNl 1—

CO o c o V

•H tH •

4-1 CO o CO

CO 4-1 rH 4-1 o 3 <j2 • CO CO o rH CM i—H c» o o o o C 4-' CO Csj CM I-H 1—I o 4J

t—

c

T—1 : QJ • T3 1 (-1 QJ 4J (2 o c CO o •r-l CO c CO 00 CM CTi vD o o o rH

4_l cn r-H I—

CO 4-< 4-) a) c xt <3

60 QJ CO Q)

CO o CO

u

4-1

U QJ CO

C 0)

U

(D > y H CM <f 1

CM 00 o in

}j o 1—1 «^ 00 v£) a^ 00 On in \/ p 1 c

<4-l 4-1 CO CO O C

>i o 0^ CNl CT^ CO o -J- V4 ^ CO I-H l/^ CO vD

CO QJ QJ V"

T—

%, ^ o 3 O C 3

CO Q)a

rH CM CO rH CM • H O C.J C-J CM

i-H c

<u CO 6 QJO I-H CO 1—

0) 1-1 c u (J H 4-1 CO CO TJ

CO 4.J -a <+-l CM Q) c •H o c CO O !S V-l M O CO QJ CO

CO rH tH cx O c MH

CO > CM 3 > COC

u

U 2 < M 1 1 rH

QJQJ

4-1

flw1 CO - c c

CO CO

QJ Q) •H 4-1 U-^ re it

UJ CJ rH

CO

C >H

cO o QJ iH o P- T3C u

CO CO QJ

<D

CO CO •H

CO

C <4H

OJ

O

•H CO

4-1 CO

CJ CO CO • 'H rH rH 3

4-» CO

C c o

•H CO

CO

QJ QJ (J C c QJ CO

co X. o

cd 4-J •H iH

QJ QJ

!h 4-) QJ 3 4-J > >. 4-1 CO

CO rH rH

QJ

O CO T3 f. a

sd CO TJ QJ CO CO C c C

CO 0) o

!h •H

>, !h 4-1 -a 4-1 CO CO u CO rH

CO >^ c 3

rH CO CO c o 4-1 C

CO

a CO •H

4-1 CO ne

QJ c CO o o^ . o >,

4-1 'O )H CO CO

QJ QJ ^ QJ >.

CO ,43 CJ CO iH

CO •H QJ CO

O

PQ 14H 0-

11
Table 13. Instrument Effects^ for the Capacitance, Nuclear, and Infrared

Methods Based on the TVP and S Indicators

Insulation

Glass Fiber

(Figs. A71 and A75)

Perlite

(Figs. A79 and A83)

Polystyrene

(Figs. A95 and A99)

Indicator 1" 2

•• 1" 2" 1" 2"

TVP

C < N C < N

C < IR C « IR

IR « N IR » N

N < C C « N

IR < C C « IR

IR » N IR « N

M < C N < C

C « IR IR < C

N < IR IR « N

S

N > C N > C

IR > C IR > C

N > IR IR « N

N > C N > C

IR > C IR > C

IR « N IR » N

N > C N > C

b b

b b

^ For "standard" asphalt thickness and steel deck. The follov«/ing definitions

are used: "C" represents the capacitance instruments (CI, C2, C3); "N" represents the nuclear instruments (Nl, N2 )

; "IR" represents the infrared instrument;

"»" means approximately equal to.

Entries not determined because only one S value occurred for the infrared

instrument.

73
t-1 (Nl 0) oP < > -

P4>EHuo

<u

01 M

(0 tso

(U g

IH

rt

(U

i-io1

T3 to C I-I n) O

J-l <Uo O c •H a T3 u C

•Ho M a

rJ XI o c

to

i-i o

UHm

4-) u

(U Uh

lUM

4-> d

<uB3

VI

COa

tn G\

>. < O ^C) J2 00M

•H

t«> - - >

T3 3d

4-J «

t/D :

t/3 I tc - -H C

tji

m

O « t/l -r-t >i o -u > D. a) a: c

tvj (D aj • • .-I

COU -H

C

v>

O

>> tfl T-l > O 4-1 E a taa

•a >H th

4-1 .H XI

It) e O CO T3 CJ - >

t-g -

i-< tu to 3 i-H : to p. d e x; c • to

to to iH ^ 3 ^ o to

•H (U

O E tU -H O 4-1 X

(U T3 •

>-i

d C3

CO n) -H : 0) CM tN 4-J « H C : O to ^ CO -H

tn tu t3 a) D.

CU CO to > ^ CU o to J3 X CU ^

tj to c

COO

4J CU

CU iH U to CO iH

to

X CU 0.-01

to CO

O 4-1 CU to CO •H : -o -a

4-1 >, 4-1

C

C > ^ al a) CO

-I X5 4-1 - B

to 1-1

tJ c 3 M 2

4-1

C -H CU iJ

CJ to 4-1 4-1 4-1 U to tJ to

74
T3 0101 c CO •H U)

(fl <S) 4-1 p < u

•H

4-J x: O HCo

•a •H c i~l « n)

i-H3

4-1 Ul c C

(UM o

t-i » <u c

•H o CN

«N c

nj c

01a

C

u •H

01 Puo T3C« c« cn

0)

4-J CO

(0

cn 0) 10 c

0) kJ o

•H

U3

dJ

H 3

i-l 4-1 > «

Pu

a > CO H <:

of >

U) (0

0) OJ

CS 4Jc

0)u

V4 Pi

0) c

Co

O o o o o

LO '

<. fn r

CO o o o

rr ^>

OJ

H coHH 5^O C <N1 CNl O

•H N/

4J •

Q-* I> o O o o H COCM c

&^ •H 00 Ln O I-H LTl GO

CNI

V • c > o o O 1—

ro

H CSl rO CO CN

•n

QiP >

CN C_J

Cu QJ CN O • CO O

O o o

cC > W

tu

H c/^

CO

01c > CO o o 00 in

CNJ in IT) 00 00 00 o QJ •H 6^OCN

\/

il

CO Pu CO > LO CO in

m CO c^

00

to

C/j>

<u ON >^ o CO

s-s CN in o'~* N/

CO

•<r <J"

H c Cn

m in

CO

m c CM CN

<u z

t-i CN] CN o z

COc

00 00 > > < <

CO

CO

QJ

cj •H

4-)

4_l -H

Cfl -C

CL

CO

CO>

to0) J=

0)

4Juo

y-i

)-< 0)

4-1 CO

<uuM COC

0)E

CO •Ho

0) 01 c cx

OJ CO

01

C

•H 4-1

V4

CO o

to 14-1

4-1 CO x:

CO

M

01 •H C 0)

.:<: 3 o

•i-t .H

01 4J >

CO

i-H

M

01 60 >

CO -o

l-i

C o CO

75
1=o

•Hmo

4Ja

tobO

•H

cn •p•COa

1-1o

pCO • a

•H CO IWo a o CO

»-l CO

M-l 4J O o co 4=

•H 4-1

4-) •H

COo

•H X)

}-i CO

CO

O • t—

u

60

76
77
I

CM

(U

4-1 4J

CO ef

i-l iH

fo an CM co CU •H -C3 •X3

4-1 •H

•H CO CO O 4-1 «k

W)

u

CU 4J •H c

4-1 CU

CO <L) CJ

0) 4-1 4-1 <UU cs c o u

•H co

CO o ^ C CU

<D <u Xl e •H

•iH 4-1 CO

CJ(U c 4-> a o X:

CO W)

CO •H

4-1 V4

CU c o

CO 1—1 3 CJ

>-i 3 4J CO CO CO 4-> C C

J: •H 0)

4-1 o V4 § o CO V4 6 <D 4-1 CO iH CO O c 3 C C

CO TJ • C

iH

C CO 15

(U CO ^ O > O J=

CO CU <u CO

J-1 CJ T5

00

C CU

CO »-i 4-1 Vj CO

CO -H CU O O +J •H CO C (U >s CO O -H H O w CO

en

CUu3

60

•H

78
79
EXTRUDED POLYSTYRENE FACING

Detail View

50°F ; 25% RH OUTSIDE

16 FT Overall View

Figure 5. Insulated wooden chambers used to induce moisture in the

roofing specimens.

80
81
82
,

-

O

- o

o

( o

0

(3p —

1 1 1 I ^1 1 1 1 ^1 I 1 I

o\

1 1




OJ

bJO

(H

Ixi Q_

UJ

O

z>

CL3

OO

UJ

0^

CD

o

ru

CD

oo

LULU

QQ_

CO

LU

tLU

^

Ck: o

o

ze- oz

OLU

e: -ZD XQi Ot- Z CD

LUCO

t-LU

o

LU

OO ^

X

LUCL

O

l-HQ

<t

<r

E-

(Si


 LOLD

Lf) OJ

in

ru

I

<E O-) Z3 </) f- LU O ZQLU LU CO Q- O Z: <J) UJ

83
9

LO

LO

OJ

I

!Z LiJCO

It iijo

UJ uj

Q. ulitiJ o _

3 UIV>

UJ ujo

ID T

Q.

UJO

»-»z: U.<E

olaJ c^uj(nQ.oz:a)Uj

84
85
86
87
88
89




 OJ




o

bJ

a.

LJ

o

CL

z:o

o

LU

DC

CO

o

00

o

LUO

QUJ

Q.

UJ</)

Ld

QclOJ

oz:

z:OEoz:

UJ

z: E—

•-•COz:

LUCO

LUO

I-

<3: LUX

Q^CL

ID CO

C? <E

z>

<E

LU

ru


 <9

<r Q *-D ZD CO t- LU Q ZI Q LU LU Cn 0_ O Z CO LU

90
91
C^ (1 

\1J /—

\^

W CO CO H G 4—

CO GO OJ CO

05 (11

4-) o O J-I cu r\W 1—

1 1 + (-;

'X* "

CnJ

Q

p ,

CO Cl d) c^3 Zj D5 O O 4-J (-< 1—

Q O CD C (11 w p O1—

^ 1 Q CO r\ 1 1 1uo1 + 4-1 4-* 4-J rH \J Q UJ ^ (11 Q to 1 1 •i—1 QJ CJ CO •> CO Pi O G CJ

i—Pi t—

pi Lj Lj t— ^ M

*H CO C/j o CU <L) CO o >—

CO CO r-H M-l t3 CO o o U O C 4-10 0 e

II CO 1 O i-i CU u OJ E O (=: CUD C d o o D o Ph cd O 0) iH 4-1 4-J 6

4-J > I-I CO •H c H CD p: > o o X > o > o o CO o 4-1 CJ cn E E <u 3 ^ +^

<Q o E S E S

CO LUO

CO

CM

CO

C

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CU

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4-1 o <u

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92
a.

0.4

d > U.U Q CO O U.U SS = 0.0

Linear ABC ; A (SS = 0.0) 0.0

1 ,1 1 0 TYP Vp^ Vp 0 TVP Yp^ Vpj Vp

b.

SiO.O->j^ S<0.0 0.4

1 SS < 0.0

CO

A

/ Concave downward \

- / (SS < 0.0) rill 0.0

1 ^

s-.o

TYP Ypi YP2 Yp 0 TYP Yp^ Ypj Vp

Concave upward

(SS > 0.0) 0.4

S > 0.0 /c S>0.0

CO SS > 0.0

A / B — 1 1

0.0

'

1 0 TYP Ypi YP2 Yp 0 TYP Ypi YP2 Yp

MOISTURE CONTENT, Yp .(volume %) MOISTURE CONTENT, Yp,(volume %)

S =SENSITIYITY;SS = slope of S vs Yp curve

Figure 18. Typical Relationships between Ry - Rp vs. Vp Fitted

Curves and their corresponding S vs. Vp curves.

93
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»-4ZU>l->IK3CUIZ:h- Q^UJU)Q.OZa)liJ

99
100
101

APPENDIX A

COMPILATION AND ANALYSIS OF NDE DATA

A-1
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NBS>114A (REV. 9-78)

U.S. DEPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR REPORT NO.

BSS 131

2, Gov't Accession No, 3. ft^Cipieni's Acc&$sioft No»

4. TITLE AND SUBTITLE

"Laboratory Evaluation of Nondestructive Methods to

Measure Moisture in Built-Up Roofing Systems"

5. Publication Date January 1980

5. Perfoiming Organiitatlon Cod«

1

7. AUTHOR(S)

Lawrence Knab, Robert Mathey and David Jenkins

8. Performing Organ. Report No.

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, DC 20234

16. Pro}ect/tasJ«/Work linit No.

11. Contract/Grant No.

12. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS fSrree*, City, st^te. ziP)

Directorate of Engineering and Services

U.S. Air Force

Washington, DC 20330

13. Type of Report & Period Covered

Final

^nsorifig Ageicy CSode

15. SUPPLEMENTARY NOTES

Library of Congress Catalog Card Number: 80-600189

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

16. ABSTRACT (A 200-word or less {actual summary of moat significant information. If document includes a significant bibliography or

literature survey, mention it here,) This laboratory study investigated the reliability and accuracy of three types of. non destructive evaluation (NDE) methods to quantitatively determine the moisture content

of the insulation in built-up roofing specimens. These methods were electrical capacitance, nuclear backscatter , and infrared thermography. Thirty-six roofing specimens,

which consisted of five types of rigid -board roof insulations with attached bituminous

built-up membranes, were tested over both concrete and steel decks. A wide range of

moisture contents was induced into the specimens by maintaining a constant water vapor

pressure difference across them.

Two performance characteristics of the NDE methods were evaluated: (a) the minimum

moisture content a method could detect, and (b) the relationship between NDE response

and moisture content beyond the minimum detectable moisture content. The two perfor- mance characteristics were assessed through normalization parameters defined in terms

of the NDE response and its scatter about a fitted curve. There were differences in

the performance characteristics, the magnitude of which depended on the NDE method,

the specimen composition, and the deck type used.

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) Built-up roofing electrical capacitance; infrared thermography; insulation; moisture

detection; moisture measurement; nondestructive evaluation; nondestructive testing;

nuclear backscatter: roofing systems

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173

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