An Evaluation of the Effects of Various Test Parameters on the

Air Voids of Asphalt Concrete Specimens

John P. Zaniewski, Ph.D.

Matthew Hypes

Asphalt Technology Program

Department of Civil and Environmental Engineering

Morgantown, West Virginia

January, 2008

ii

NOTICE

The contents of this report reflect the views of the authors who are responsible for the

facts and the accuracy of the data presented herein. The contents do not necessarily

reflect the official views or policies of the State or the Federal Highway Administration.

This report does not constitute a standard, specification, or regulation. Trade or

manufacturer names which may appear herein are cited only because they are considered

essential to the objectives of this report. The United States Government and the State of

West Virginia do not endorse products or manufacturers. This report is prepared for the

West Virginia Department of Transportation, Division of Highways, in cooperation with

the US Department of Transportation, Federal Highway Administration.

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Technical Report Documentation Page 1. Report No. 2. Government

Association No. 3. Recipient's catalog No.

4. Title and Subtitle An Evaluation of the Effects of Various Test Parameters on the Air Voids of Asphalt Concrete Specimens

5. Report Date January, 2008 6. Performing Organization Code

7. Author(s) John P. Zaniewski, Matthew Hypes

8. Performing Organization Report No.

9. Performing Organization Name and Address Asphalt Technology Program Department of Civil and Environmental Engineering West Virginia University P.O. Box 6103 Morgantown, WV 26506-6103

10. Work Unit No. (TRAIS) 11. Contract or Grant No. RP 122

12. Sponsoring Agency Name and Address West Virginia Division of Highways 1900 Washington St. East Charleston, WV 25305

13. Type of Report and Period Covered 14. Sponsoring Agency Code

15. Supplementary Notes Performed in Cooperation with the U.S. Department of Transportation - Federal Highway Administration 16. Abstract The Superpave mix design protocol was developed with goals of minimizing premature failures, reduced maintenance costs, and increased pavement life. Several researchers evaluated the various parameters controlled in AASHTO SuperPave mix design protocol, T312 and AASHTO R30. These projects focused on the major parameters which affect the preparation of samples, such as the operational parameters for the SuperPave Gyratory Compactor. However, the AASHTO procedures also control a variety of other parameters which affect the preparation of the samples. In several cases, the research support for the specific requirements in the procedures is either limited in scope or non-existent This research evaluated variations of test parameters required by the AASHTO mix design protocol and their effects on air void levels of asphalt concrete specimens. Variations in mix temperatures, compaction temperatures, oven cure times, mold preheating times, and time to determine Bulk Specific Gravity (Gmb) values were evaluated using asphalt specimens prepared with two different aggregate types and two different binder types. The effects of the design parameters and their interactions were evaluated. The research demonstrated the voids in the total mix, VTM, is not sensitive to the parameters evaluated during this research. 17. Key Words Asphalt test variability, Superpave tests

18. Distribution Statement

19. Security Classif. (of this report) Unclassified

20. Security Classif. (of this page) Unclassified

21. No. Of Pages 64

22. Price

Form DOT F 1700.7 (8-72) Reproduction of completed page authorized

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TABLE OF CONTENTS

Chapter 1: Introduction ........................................................................................................1

1.1 Background ....................................................................................................................1

1.2 Problem Statement .........................................................................................................2

1.3 Objectives ......................................................................................................................2

1.4 Scope and Limitations....................................................................................................3

1.5 Report Summary ............................................................................................................4

Chapter 2: Literature Review ...............................................................................................5

2.1 Effect of Viscosity on Compaction ................................................................................5

2.2 Effect of Oven Aging ...................................................................................................16

2.3 Summary of Literature .................................................................................................22

Chapter 3: Research Methodology.....................................................................................24

3.1 Introduction ..................................................................................................................24

3.2 Experimental Design ....................................................................................................24

3.2 Aggregate Processing...................................................................................................28

3.3 Mix Preparation ...........................................................................................................29

3.4 Specimen Fabrication...................................................................................................30

3.5 Testing Procedure ........................................................................................................30

Chapter 4: Results and Analysis ........................................................................................33

4.1 Introduction ..................................................................................................................33

4.2 Effect of Time to Determine Bulk Specific Gravity ...................................................34

4.3 Analysis of Variance ....................................................................................................35

Chapter 5 Conclusions and Recommendations .................................................................39

5.1 Conclusions ..................................................................................................................39

5.2 Recommendations ........................................................................................................40

References ..........................................................................................................................41

Appendix A - Mix Design..................................................................................................42

Appendix B - Test Results .................................................................................................44

LIST OF FIGURES

Figure 2.1 Temperature vs. Gmb Relation for Asphalt Binders X and Y ............................ 7

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Figure 2.2 Gmb vs Temperature for Multigrade and Unmodified 1 for Mix 1 .................. 10

Figure 2.3 Stuart’s air voids versus compaction temperature. ......................................... 17

Figure 2.4 Short-Term Oven Aging Results ..................................................................... 20

Figure 2.5 Air Voids Versus Aging Temperature ............................................................. 21

Figure 2.6 Air Voids Versus Aging Duration ................................................................... 21

Figure 2.7 Air Voids Versus Compaction Temperature ................................................... 22

Figure 3.1 Fractional Factorial Design ............................................................................. 26

Figure 4.1 Summary of Results (See Figure 3.1 for Sample Designations) ..................... 34

Figure B.1 Least Mean Squares Plots Aggregate Size ..................................................... 47

Figure B.2 Least Mean Squares Plots Mix Temperature .................................................. 47

Figure B.3 Least Mean Squares Plots Cure Time ............................................................. 48

Figure B.4 Least Mean Squares Plots Compaction Temperature ..................................... 49

Figure B.5 Least Mean Squares Plots Binder Type .......................................................... 49

Figure B.6 Least Mean Squares Plots Mold Preheat Time .............................................. 50

Figure B.7 Least Mean Squares Plots Agggregate Size and Mix Temperature................ 50

Figure B.8 Least Mean Squares Plot Aggregate Size and Cure Time .............................. 51

Figure B.9 Least Mean Squares Plots Aggregate Size and Compaction Temperature ..... 51

Figure B.10 Least Mean Squares Plots Aggregate Size and Mold Preheat Time ............. 52

Figure B.11 Least Mean Squares Plots Aggregate Size and Binder Type ........................ 53

Figure B.12 Least Mean Squares Plots Mixing and Compaction Temperature ............... 53

Figure B.13 Least Mean Squares Plots Mix Temperature and Cure Time ....................... 54

Figure B.14 Least Mean Squares Plots Mixing Temperature and Mold Preheat Time ... 54

Figure B.15 Least Mean Squares Plots Mixing Temperature and Binder Type ............... 55

Figure B.16 Least Mean Squares Plots Cure Time and Compaction Temperature .......... 56

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Figure B.17 Least Mean Squares Plots Cure Time and Mold Preheat Time .................... 56

Figure B.18 Least Mean Squares Plots Cure Time and Binder Type ............................... 57

Figure B.19 Least Mean Squares Plots Compaction Temperature and Mold Preheat Time

................................................................................................................................... 57

Figure B.20 Least Mean Squares Plots Compaction Temperature and Binder Type ....... 58

Figure B.21 Least Mean Squares Plots Binder Type and Mold Preheat Time ................. 58

LIST OF TABLES

Table 2.1 Estimated Compaction Temperatures for Equal Gmb Values ............................. 9

Table 2.2 Air Voids for the Mixtures with Diabase Aggregate and No Hydrated Lime. 13

Table 2.3 Air Voids for the Mixtures with Diabase Aggregate and 1.25 Percent Hydrated

Lime .......................................................................................................................... 14

Table 2.4 Air Voids for the Mixtures with Limestone Aggregate .................................... 15

Table 2.5 Summary of Short-Term Oven Aging Data ...................................................... 19

Table 3.1 Experiment Factors and Levels ......................................................................... 25

Table 3.2 Parameters for Each Sample Tested in the Fractional Factorial ....................... 27

Table 3.3 Stockpile Information ....................................................................................... 28

Table 4.1 Comparison of Contractor’s and WVU Asphalt Lab’s Results ........................ 33

Table 4.3 Student’s Paired T-Test Results for VTM Values ............................................ 35

Table 4.4 Summary of Fit Data......................................................................................... 36

Table 4.5 ANOVA Parameter Estimates .......................................................................... 37

Table A.1 19.5 NMAS Mix Design Gradation and Weighout Information ..................... 42

Table A.2 12.5 NMAS Mix Design Gradation and Weighout Information ..................... 43

Table B.1 Effect Tests (JMP Output) ............................................................................... 44

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Table B.2 Least Squares Means Tables (JMP Output) ..................................................... 44

Table B.2 Least Squares Means Tables (JMP Output) Continued ................................... 46

Table B.3 Data Sheet for VTM Determination After 1 Hour ........................................... 59

Table B.4 Data Sheet for VTM Determination After 24 Hours ...................................... 60

1

CHAPTER 1: INTRODUCTION

1.1 BACKGROUND

The SuperPave (SUperior PERforming Asphalt PAVEments) mix design system was

developed as a result of a five year, $150 Strategic Highway Research Program (SHRP)

(Tandon, 2004). The goal of the SHRP research was to minimize premature failures,

reduce pavement maintenance costs, increase pavement life, and reduce life-cycle costs

for hot-mix asphalt (HMA). The Marshall mix design system has been sufficient since

WWII, but today’s highway demands far exceed those of the past, thus the need for a new

and improved asphalt mix design system. The SuperPave mix design system has been

implemented by the majority of transportation agencies in the United States for HMA

mix designs due to its numerous benefits such as improved binders from enhanced lab-

aging procedures, a more comprehensive low-temperature testing protocol, improved mix

design procedure from the optimization of aggregate structure, and the use of a

compactor that better represents actual pavement characteristics (ARTBA, 2000).

These transportation agencies, along with paving contractors and construction materials

design and testing firms, use the SuperPave Gyratory Compactor (SGC) for not only the

HMA mix design, but for quality control and assurance testing (Buchanan, 2004). This

device produces specimens for analyses of both volumetric and mechanical properties of

asphalt concrete, as well as records data in order to provide a measure of the density

throughout the compaction process. The SGC is capable of measuring compactability so

that the tender mix behavior and similar compaction problems can be identified

(Yildirim, 2000).

Compaction in the laboratory is an extremely important element in the mix design

process, and in order to be effective, the mix design process must implement a laboratory

compaction method which closely simulates compaction in the field. Research conducted

by SHRP developed the SuperPave gyratory compactor specifications that are being

currently being used, as specified in AASHTO T 312. The gyratory parameters are:

• Vertical Consolidation Pressure of 600 kPa

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• Fixed Angle of Gyration of 1.25o, and

• Speed of Gyration of 30 rpm.

AASHTO T312 also describes the requirements for the mixing and compacting

temperatures, preheating time for the compaction mold, and cooling period for the

compacted sample prior to measuring masses for the computation of bulk specific gravity

(Gmb).

The period between mixing and compacting is referred to as curing. The procedure for

curing samples is described in AASHTO R30. Curing of laboratory samples for

volumetric mix design essentially consists of placing the mix in an oven at the specified

temperature for 2 hours.

1.2 PROBLEM STATEMENT

Several researchers have evaluated the various parameters controlled in AASHTO T312

and AASHTO R30. These projects focused on the major parameters which affect the

preparation of samples, such as the operational parameters for the SuperPave Gyratory

Compactor. However, the AASHTO procedures also control a variety of other parameters

which affect the preparation of the samples. In several cases, the research support for the

specific requirements in the procedures is either limited in scope or non-existent. For

example, the mixing and compacting temperatures used for the SuperPave Gyratory

Compactor were adopted from the Asphalt Institute’s recommendations. These

recommendations were originally developed for the Marshall and Hveem methods

(Roberts et al, 1996).

1.3 OBJECTIVES

The objectives of this project are to examine the differences in asphalt concrete

volumetric properties due to variations in the method for preparing samples for the

SuperPave Gyratory Compactor. In this study, variations in mix temperatures,

compaction temperatures, oven cure times, mold preheating times, and time to determine

Bulk Specific Gravity (Gmb) values were evaluated using asphalt specimens prepared

with two different aggregate types and two different binder types.

3

1.4 SCOPE AND LIMITATIONS

For this study, mixing and compaction temperatures were determined by the asphalt

cement supplier. ASTM D2493, Calculation of Mixing and Compaction Temperature,

was used as the reference temperatures for preparing the samples. In this standard, the

viscosity-temperature relationship is plotted providing a convenient means for

determining mixing and compaction temperatures.

Laboratory oven-curing time is a required step in the HMA mix design process. The

standard oven-curing time for HMA is two hours. The AASHTO Subcommittee for

Materials reduced the oven curing time to two hours from the initial recommendation of

four hours that was established by SHRP researchers. The fundamental purpose of oven

curing is to allow for absorption equivalent to the asphalt absorption that occurs during

field production. The AASHTO specification of a two-hour curing period is for the use

of non-absorptive aggregate, but a very significant percentage of HMA’s contain highly

absorptive aggregates and require a time of four hours for oven curing. If one fails to

increase oven curing time when highly absorptive aggregates are used, erroneous mix

specific gravities and volumetric property determinations will result (Horan, 2001).

Two production mixes were evaluated during this study. The mixes had Nominal

Maximum Aggregate Sizes (NMAS) of 9.5 mm and 12.5 mm. These mixes were

designed with a PG 76-22 binder. In order to determine if the binder grade affected the

results, a PG 64-22 binder was also used in the experiment. The mixes binders were

prepared at the same binder content as the production mixes.

The effect of mixing and compaction temperatures was studied for the two binders.

Since the temperature-viscosity relationship for the two binders is different, the

temperatures used in the experiments were varied by binder type. The temperatures used

for each binder corresponded to the upper and lower recommended temperatures based

on the equiviscosity concept in AASHTO T312.

The influence of cooling time on bulk specific gravity was studied and included in the

experiment. AASHTO T312 states that the samples should be cooled at room

temperature for 16 ± 1 hr, but the cooling can be accelerated with the use of a fan. The

4

specification does not include a minimum cooling time when a fan is used. It is common

practice in West Virginia to cool the samples until they can be easily handled and are not

tender. To evaluate if cooling time affects bulk specific gravity of the mix, samples were

cooled in front of a fan for 1 hour. The weights needed for determining Gmb were then

measured. These samples were then allowed to cool to room temperature until the next

day and the weights were measured again. Use of the same samples in this manner

restricted the randomization of the experiment, so this factor was not analyzed in the

analysis of variance. The Student t-method was used to evaluate if the bulk specific

gravity was significantly altered by cooling time.

1.5 REPORT SUMMARY

This report is divided into 5 chapters and 2 appendices. Chapter 1 represents an

introduction to the project which is followed by a Literature Review in Chapter 2. In

Chapter 3, the research methodology is presented, including the processes used to process

the aggregates and fabricate the samples, the experimental approach, as well as the tests

necessary for the completion of the project were all discussed. Chapter 4 includes an

analysis of the results followed by Chapter 5 which discusses the conclusions and

recommendations.

5

CHAPTER 2: LITERATURE REVIEW

A comprehensive literature review was performed to identify the research basis for the

mix design procedural criteria used for the SuperPave method. Literature was identified

for the effect of temperature on compaction, and the effects of temperature and aging

duration on air void content.

2.1 EFFECT OF VISCOSITY ON COMPACTION

The Asphalt Institute’s Mix Design Methods for Asphalt Concrete and Other Hot-Mix

Types (MS-2) recommended 170±20 centistokes and 280±30 centistokes, measured per

ASTM 2493, for mixing and compaction temperatures respectively for the Marshall mix

design. Thirty years later, these identical specifications, when adjusted for unit

conversion, are used in SuperPave, 0.17±0.20 Pa.s and 0.28±0.03 Pa.s for mixing and

compaction temperatures respectively. These viscosity parameters were established for

unmodified asphalt binders. However, due to the recent increases in traffics loads, high

performance, modified asphalt binders have been introduced which have a more complex

behavior than unmodified binders (Mostafa, 1999).

A study conducted by Yildirim et al. (2000) examined the effect that varying

temperatures have on bulk specific gravity of asphalt concrete. This study was an

attempt to devise an alternative to using ASTM D2493 to determine the mixing and

compaction temperatures of asphalt concrete. ASTM D2493 provides practical

temperatures for unmodified binders, but temperatures may become excessively high

when working with modified binders. Excessive temperatures can result in construction

problems, asphalt damage, and production of fumes. ASTM D2493 was intended for

unmodified binders which are classified as a Newtonian fluid, a substance in which

viscosity does not depend on shear rate. Yildirim’s investigation attempted to determine

the shear rate during compaction with the intention that the results could be factored in to

the mixing and compaction temperatures.

Two mixes were evaluated. Mix 1 used an angular, relatively porous crushed limestone,

and Mix 2 used a round, smooth, and relatively nonporous sand. The specimens were

6

compacted at equiviscous temperature conditions corresponding to 0.170 Pa·s and 0.280

Pa·s, respectively. Once compacted, the specimens’ volumetric mixture properties were

determined in accordance with AASHTO MP2, Standard Specification for Superpave

Volumetric Mix Design.

Yildirim states the mixing temperature of most binders is 10 to 20°C higher than the

compaction temperature. Throughout the mixing process, it is imperative to achieve

uniform dispersement of asphalt binder throughout the aggregate and complete coating of

the aggregates. Yildirim cited a study by Bahia that states increasing the mixing time 1

to 2 minutes can result in complete coating of the aggregates at extremely high viscosities

that are not expected to be exceeded in the field. Therefore, using the mixing temperature

lower than the values determined using ASTM D 2493 should not present any problems.

In phase 1 of the project, the relationship between compaction temperatures and bulk

specific gravity of a compacted mix was evaluated. In phase 1, samples were prepared

using a range of compaction temperatures using both modified and unmodified binders

and the bulk specific gravity was measured. The specimens were compacted in the

SuperPave Gyratory Compactor at five different temperatures. Mix 1 was compacted at

55°C, 65°C, 75°C, 85°C, and 95°C. Mix 2 was compacted at 50°C, 60°C, 70°C, 80°C,

and 90°C. The Asphalt Institute (1989) states that compaction temperatures usually

range from 80°C to 155°C. Yildirim chose compaction temperatures between 50°C and

95°C to “better evaluate temperature’s effect on bulk specific gravity”. The authors

stated that at higher temperatures, the viscosity of asphalt binder decreases; consequently,

it becomes more difficult to see the effect of temperature on compaction in the SuperPave

Gyratory Compactor.

The least squares method was used in order to estimate the relation between compaction

temperatures and bulk specific gravity. The model used for the estimations was bxay ⋅= . For this model, y represented the Gmb values, a and b were regression

constants, and x represented the compaction temperatures. In each of the eight

experiments, Gmb values for asphalt mixes, using both modified and unmodified binders,

increased with increasing compaction temperatures. Also, it was determined that the

7

implementation of the shear rate concept for unmodified binders can reduce mixing and

compaction temperatures of asphalt concrete by approximately 10°C to 30°C (Yildirim et

al., 2000).

Yildirim states that the factors affecting the Gmb values of a specimen include aggregate

gradation and type, viscosity of the asphalt binder, and the type of compactor used. For

any two specimens, if all factors affecting the Gmb are kept constant, the Gmb values for

the two samples will be the same. The authors states that this idea can be used for the

calculation of shear rate inside the SGC.

Figure 2.1 illustrates Yildirim’s approach. The figure depicts the estimated relationship

between the Gmb values and compaction temperature. He hypothesized that the specimen

prepared with the unmodified asphalt binder and compacted at temperature A will yield

the same Gmb value as the sample prepared with the modified asphalt binder which was

compacted at temperature B. This would indicate that the viscosity value of unmodified

asphalt binder at temperature A is equal to the viscosity value of modified asphalt binders

at temperature B.

Figure 2.1 Temperature vs. Gmb Relation for Asphalt Binders X and Y

8

For each mix design comparison, a Gmb value was chosen. Usually, a Gmb value at the end

of the compaction temperature range was selected. Figure 2.2, which is representative of

all of Yildirim’s results, shows Gmb values increase with increasing compaction

temperature. Therefore, the voids in the total mix (VTM) will decrease with increasing

temperatures. Usually, a Gmb value at the end of the temperature was selected. For each

figure, the relationship between Gmb values and compaction temperatures was estimated

for one modified asphalt binder and for one unmodified asphalt binder. Subsequently,

the corresponding compaction temperatures were estimated using the selected Gmb value.

These Gmb values and the corresponding temperature for compaction are listed in Table

2.1.

Yildirim hypothesized that the asphalt binder viscosity throughout compaction should be

equal for two different specimens if they have the same bulk specific gravity. This

hypothesis is based on the fact that all of the variables affecting Gmb such as type and

gradation of the aggregate and the compactor type are all kept the same. Thus, it can be

concluded that at the temperatures corresponding to a particular Gmb value, viscosity

values for the modified and unmodified binders are the same during compaction.

Another research project, sponsored by the Federal Highway Administration (FHWA),

dealing with the determination of mixing and compaction temperatures of asphalt

concrete was completed by Stuart (2001). The objective of this study was to find an

asphalt binder or mastic property that can provide the compaction temperatures needed

for asphalt mixture design. This project is conceptually similar to that of Yildirim’s. The

background of the study begins with a discussion of the determination of the compaction

temperature of asphalt concrete using the equiviscous principle, which is based on the

viscosities of the asphalt binder. Stuart states that when this principle is used,

theoretically, all asphalt binders should provide the same optimum asphalt binder content

at 4 percent air voids when all other variables, such as compaction effort and aggregate

gradation are held constant. Unaged asphalt binders are used to determine the

compaction temperature. Therefore, the methodology assumes that each asphalt binder

will age harden approximately the same prior to compaction. Stuart also states the

equiviscous principle was developed for use with unmodified asphalt binders, therefore,

9

for some polymer-modified binders, the equiviscous principle gives a compaction

temperature significantly higher than what is actually necessary. Excessive high

temperatures can possibly cause damage to the asphalt binder, which can lead to the

generation of fumes and asphalt binder drain-down, thus causing low asphalt binder

content in some mixtures.

Table 2.1 Estimated Compaction Temperatures for Equal Gmb Values

Binders Mix Gmb

Compaction Temperatures for Gmb

Value

Multigrade-Unmodified 1 1 2.312 Multigrade-Unmodified 1 93oC Unmodified 1 83oC

Multigrade-Unmodified 1 2 2.261 Multigrade-Unmodified 1 90oC Unmodified 1 80oC

TR Modified-

Unmodified1 1 2.308 TR Modified-Unmodified1 94oC Unmodified 2 78oC

TR Modified-

Unmodified1 2 2.257 TR Modified-Unmodified1 89oC Unmodified 1 73oC

Multigrade-Unmodified 2 1 2.312 Multigrade-Unmodified 2 93oC Unmodified 2 71oC

Multigrade-Unmodified 2 2 2.261 Multigrade-Unmodified 2 91oC Unmodified 2 68oC

TR Modified-

Unmodified2 1 2.310 TR Modified-Unmodified2 95oC Unmodified 2 70oC

TR Modified-

Unmodified2 2 2.259 TR Modified-Unmodified2 91oC Unmodified 2 64oC

10

Figure 2.2 Gmb vs Temperature for Multigrade and Unmodified 1 for Mix 1

For the experiment, the SuperPave Gyratory Compactor was used to compact a mixture

with an unmodified asphalt binder at various temperatures to obtain the range in

temperature that did not affect the volumetric properties of the mixture at the design level

of compaction effort (N-design). Polymer-modified asphalt binders were then substituted

for the unmodified asphalt binder. The volume of binder was kept constant. The

compaction temperature that gave the same volumetric properties as the unmodified

asphalt binder was found for each modified binder. The rheological properties of the

asphalt binders and mastics used in the mixtures were then measured to determine what

property provides temperatures that meet the temperature ranges given by the compaction

process.

Stuart’s experiment incorporated three binder types and three aggregate types. Each

combination of aggregate and binder type was compacted at four temperature levels.

Two aggregate types were variations of an aggregate blend used extensively in a previous

FHWA, and two National Cooperative Highway Research Program (NCHRP) studies.

The blending percentages used in the three prior studies were 61-percent No. 68 diabase,

11

30-percent No. 10 diabase, 8-percent natural sand, and 1-percent hydrated lime. This

blend met the requirements for a Virginia Department of Transportation (VDOT) SM-3

surface mixture gradation. The three binders were a PG58-28 unmodified binder and two

proprietary modified binders, Novophalt and Styrelf. Three of the compaction

temperatures were selected : 1.) equiviscosity compaction temperature, 2.) plus 20°C, and

3.) minus 20°C. A fourth temperature was selected based on the viscosity of the mastic

of the asphalt cement and fine aggregate.

Tables 2.2 to 2.4 show the percentages of air voids in the various mixtures and their

variations with differing mixture and compaction temperatures.

Table 2.2 shows all of the data for the asphalt concrete mixtures with diabase aggregate

and no hydrated lime. For the specimens fabricated with the PG 58-28 unmodified

asphalt binder, the mixing temperature was fixed at 145oC. Table 2.2 shows the air voids

of the two specimens compacted at 117oC had a difference of 0.9 percent (4.1 vs. 5.0

percent). This is a large difference based on the air voids at other compaction

temperatures; the reason for this was not evident.

The specimens made with diabase aggregate and no hydrated lime and Novophalt (PG

76-22) Polymer-Modified Asphalt Binder were fabricated had a fixed mixing temperature

of 166oC. The average air voids of all samples were greater than the allowable air void

range of 3.5 - 4.5 percent. In the mix design process, this would indicate additional

asphalt binder would be needed to achieve 4.0 percent air voids. The air voids using

mixing and compaction temperatures of 166 oC and 139 oC were 1.0 percent apart (5.6 vs.

4.6 percent). These tests were repeated using new materials and the air void levels for the

repeat tests was 4.3 percent, compared to 5.0 percent for the initial test. A reason for this

was not evident.

The specimens fabricated with diabase aggregate and no hydrated lime and Styrelf (PG

82-22) Polymer-Modified Asphalt Binder had a fixed mixing temperature of 163oC.

Table 2.2 shows that the average air-void levels were greater than 4.0 percent. However,

most samples were within the allowable air void ranges of 3.5 to 4.5 percent. The air

voids for the two specimens fabricated using mixing and compaction temperatures off

12

188 and 177oC, respectively, were 1.2 percent apart (3.8 vs. 5.0 percent). Stuart stated

that this is a large difference based on the air voids of the other compaction temperatures,

but a reason for this was not evident.

Table 2.3 shows the air void data for the mixtures with diabase aggregate and 1.25

percent hydrated lime. The specimens fabricated with PG 58-28 asphalt binder had a

fixed mixing temperature of 145oC. The specimens fabricated with Novophalt (PG 76-

22) were made with a fixed mixing temperature of 166oC. The specimens with the

Styrelf (PG 82-22) asphalt binder were made with a fixed mixing temperature of 163oC.

Stuart had no mention of the reasons for the air void differences in the table.

13

Table 2.2 Air Voids for the Mixtures with Diabase Aggregate and No Hydrated Lime.

Binder Type

Temperature, °C Air Voids, Percent

Mixing Compaction Replicate 1 Replicate 2

PG 58-28

145 157 4.0 4.1

145 137 4.0 4.0

145 117 4.1a 5.0a

145 107 4.5 4.8

Novophalt (PG 76-22)

166 179 5.2 4.6

166 159 4.4 4.8

166 139 5.6a 4.6a

166 139 (repeat) 4.4 4.1

166 119 5.2 4.7

Styrelf (PG82-22)

163 177 4.2 4.1

163 157 4.6 3.9

163 137 4.7 4.6

163 117 5.4 5.7

aThe difference in air voids is large. A difference of 0.7-percent air voids means that the 67- and 95-percent confidence limits for the average asphalt binder content by mass at a 4-percent air-void level will be be 0.25 and 0.5 percent, respectively, using two replicate specimens.

14

Table 2.3 Air Voids for the Mixtures with Diabase Aggregate and 1.25 Percent Hydrated

Lime

Binder Type

Temperature, °C Air Voids, Percent

Mixing Compaction Rep 1 Rep 2 Rep 3 Rep 4 Average

PG 58-28

145 157 4.7 3.5 3.5 3.2 3.4

145 137 4.9 2.6 4.2 3.8 4.3

145 117 5.0 6.0 3.7 3.7 4.1

145 107 3.9 4.1 4.4 3.5 4

Novophalt (PG 76-22)

166 179 4.3 4.3 4.1 3.7 4.1

166 159 4.6 4.1 4.0 4.0 4.0

166 139 4.6 4.5 3.9 3.6 4.2

166 119 4.7 5.3 4.5 5.0 4.9

Styrelf

(PG82-22)

163 177 3.1 3.4 4.3 4.0 3.7

163 157 3.9 3.5 3.3 4.0 3.7

163 137 4.8 4.7 4.5 4.6 4.6

163 117 5.2 5.3 4.6 5.0 5.0

15

Table 2.4 Air Voids for the Mixtures with Limestone Aggregate

Binder Type

Temperature, °C Air Voids, Percent

Mixing Compaction Rep 1 Rep 2 Rep 3 Rep 4 Average

PG 58-28

145 157 4.6 3.3 3.6 3.5 3.5

145 137 4.2 3.7 4.1 4.3 4.1

145 117 4.6 4 4.1 3.9 4.2

145 107 4.4 4.1 3.8 4.3 4.2

Novophalt (PG

76-22)

166 159 3.8 3.4 3.5 3.2 3.5

166 139 3.9 3.9 3.3 4.1 4

166 119 4.6 4.3 4.4 4.1 4.4

Styrelf (PG82-

22)

163 177 3.4 2.9 2.9 3.0 2.9

163 157 4.1 3.8 3.6 3.5 3.6

163 137 4.1 3.8 3.8 3.5 3.8

163 117 4.7 4.3 4.2 4.1 4.2

Table 2.4 shows the air void data for the mixtures with limestone aggregate. The

specimens fabricated with PG 58-28 asphalt binder had a fixed mixing temperature of

145oC. The specimens fabricated with Novophalt (PG 76-22) were made with a fixed

mixing temperature of 166oC. The specimens with the Styrelf (PG 82-22) asphalt binder

were made with a fixed mixing temperature of 163oC. Stuart had no mention of the

reasons for the air void differences in the table.

Stuart stated that all of the compaction temperatures for the diabase mixtures with

Novophalt and Styrelf asphalt binders, but without hydrated lime, yielded air void levels

slightly greater than 4.0 percent. This means that the asphalt binder content would have

to be increased to obtain a 4.0 percent air void level. For the specimens fabricated with

16

diabase aggregate with hydrated lime, 4.0 percent air voids were obtained. Stuart stated

that this was an example of the complexities that polymer-modified asphalt binders can

provide.

Stuart did not explicitly look for a relationship between VTM and compaction

temperature. To examine this effect the data in Tables 2.2 to 2.4 were entered into an

Excel spreadsheet to produce Figure 2.3. Visually there appears to be a tendency for air

voids to decrease with an increase in compaction temperature. A linear trend line fit to

the data demonstrates air voids decrease as compaction temperature increases:

Air Voids = 5.49 - 0.0087x RSQUARE = 0.1319

An exponential trend line was used to fit the data per Yildirim’s method; however, the

dependent variable was air voids instead of bulk specific gravity. Air voids are inversely

proportional to bulk specific gravity so the power coefficient should have opposite signs

between Stuart’s and Yildirim’s work. The trend line function was:

y = 19.154x-0.3055 RSQUARE = 0.1454

As suggested by the scatter in the data on Figure 2.3, both the linear and exponential

models have low RSQUARE values so neither model indicates a meaningful relationship

between compaction temperatures and the air voids of the samples.

2.2 EFFECT OF OVEN AGING

Another project, SHRP-A-383, conducted by C.A. Bell et al. (1994), evaluated laboratory

aging procedures on the volumetric properties of asphalt concrete. The objectives of this

study were very broad, including both short and long term effects on both loose and

compacted mixes. Short term aging simulates the change in binder properties which

occur during the asphalt concrete production and construction. Long-term aging

simulates the changes in binder properties which occurs over the life of the pavement.

Only the short term aging of loose mixes in considered in the following.

17

0

1

2

3

4

5

6

100 110 120 130 140 150 160 170 180 190

Compaction Temperature

Air

Void

s

Control Limestone

Control Diabase w/o lime

Control Diabase w/ lime

Novophalt Limestone

Novophalt Diabase w/o lime

Novophalt Diabase w/ lime

Styrelf Limestone

Styrelf Diabase w/o lime

Styrelf Diabase w/ lime

Figure 2.3 Stuart’s air voids versus compaction temperature.

The short-term aging portion of the project involved aging the uncompacted mixtures in

order to simulate the precompaction phase of construction. The short-term oven aging

implemented a forced-draft oven for time durations of 0, 6, or 15 hours at temperatures of

135oC or 163oC. The aged mixtures were then compacted at 1725 or 3450 kPa (250 or

500 psi) compactive effort by a Hveem kneading compactor to attempt to obtain the

target air void levels of 8 and 4 percent, respectively. The actual air void levels attained

were dependent on the asphalt-aggregate combinations and varied from the target levels.

The bulk specific gravity, permeability, resilient modulus, and tensile properties were

determined for all of the samples.

The results from the short-term oven aging tests are summarized in Table 2.5. Figure 2.4

illustrates that significant aging occurs, as shown by an increase in modulus with aging

time. As can be seen from Figure 2.4, from 0 to 6 hours, aging always results in an

18

increase in modulus, and form 6 to 12 hours, 5 samples decrease in modulus, and 7

samples increase in modulus. When a temperature of 161oC (325oF) is implemented, the

modulus samples for 15 hours is lower than the ratio for samples aged for 6 hours. The

difference was due to severe aging of the asphalt film in the coated mixture and the

inability to adequately compact these samples after aging. Table 2.5 shows that the air

void levels of these samples were significantly greater than the levels of both unaged

samples and samples aged at 135oC (275oF).

Due to the fact that Bell’s project did not explicitly research the variations in air voids in

asphalt concrete with respect to variations in compaction temperature, aging temperature,

and aging duration, Figures 2.5 through 2.7 were generated from the data in Table 2.5.

Figure 2.5 shows a varied trend with air void contents both increasing and decreasing

with increased aging temperatures. Figure 2.6 also illustrates that no definitive trends

exist between air void contents and aging duration. Figure 2.7 shows that, according to

Bell’s data, the percentage of air voids increases with increasing compaction temperature.

Higher air void content with higher compaction temperature is counter intuitive. At

higher compaction temperatures, asphalt binder viscosity is lower, which should promote

a decrease in air voids.

The determination to the samples’ air voids require measurement of the maximum

theoretical specific gravity of the mix, Gmm. This mix parameter varies depending on the

amount of asphalt absorbed into the aggregate surface voids. The quantity of binder

absorbed should vary with curing time and temperature. Bell did not document the

procedure used to prepare samples for determining Gmm.

19

Table 2.5 Summary of Short-Term Oven Aging Data

Key for Table.2.5 and Figures 2.4 to 2.7

K ASPHALT K=AAK-1 G=AAG-1 (SHRP CODES)

L AGGREGATE L=RL (CRUSHED GRANITE) B=RB (CHERT GRAVEL)

L VOIDS L=LOW M=MEDIUM

S SHORT TERM S=SHORT TERM

0 AGING PERIOD 0=6/4 HOURS 1=15/8 HOURS

0 AGING TEMP. 0=LOW (135oC) 1=HIGH (163oC)

O AGING TYPE O=SHORT TERM OVEN AGING

20

Figure 2.4 Short-Term Oven Aging Results

02468

101214161820

Aging Temperature (oC)

Air V

oids

(%)

KBGBGLKL

135 163

21

Figure 2.5 Air Voids Versus Aging Temperature

0

3

6

9

12

15

18

0 2 4 6 8 10 12 14 16 18 20

Aging Duration (hrs)

Air

Void

s (%

)

KBGBGLKL

Figure 2.6 Air Voids Versus Aging Duration

0

22

2

4

6

8

10

12

14

16

18

20

Compaction Temperature (°C)

Air

Void

s (%

)

KBGBGLKL

Low High

Figure 2.7 Air Voids Versus Compaction Temperature

2.3 SUMMARY OF LITERATURE

The equiviscosity concept was established for the Marshall mix design method, and

unmodified binder is widely accepted and was adopted as requirement for the Superpave

mix design method. Yildirim et al. (2000) demonstrated that it is possible to compact

samples of unmodified and modified binders to the same bulk specific gravity by

selecting an appropriate compaction temperature. However, the compaction temperatures

used in Yilidirim’s research were significantly lower than the equiviscosity compaction

temperature for the binders. This was an intentional feature of the research as it was

reasoned that equiviscosity temperatures would “mark” the temperature-viscosity-

compaction relationship. Thus, Yildirim’s results are of limited value when investigating

how variation in the specified Superpave process affects resulting mixture volumetric

properties.

A component of the research conducted by Stuart (2001)provided a data set for

examining the effect of compaction temperature on the air voids of compacted asphalt

concrete. Regression models of these data demonstrated that compaction temperatures

did not account for the variability in the air void data.

23

Bell et al.(1999) investigated the effect of aging temperature, aging duration, and

compaction temperature on the air voids of asphalt concrete samples prepared with the

Hveem kneading compactor. Bell’s data were used to prepare Figures 2.5 through 2.7.

These figures demonstrate the highly variable air void results mask any affect of the

sample preparation parameters.

There are several parameters specified in the Superpave method, AASHTO MP2, which

have not been investigated in the literature. The experiment conducted during this

research investigated these parameters.

24

CHAPTER 3: RESEARCH METHODOLOGY

3.1 INTRODUCTION

The objective of this research project was to determine the effects of variations in the

sample preparation process on the volumetric properties of asphalt concrete. The

research approach included:

• Develop an experimental plan for the research.

• Select mix designs used by contractors in West Virginia.

• Gather the sample materials.

• Randomly assign treatments to the samples.

• Perform laboratory procedures in accordance with the randomized

experimental plan.

• Complete statistical analyses of the results.

• Report the results.

3.2 EXPERIMENTAL DESIGN

Two mix designs supplied by local asphalt concrete producers were used for the

experiment. From Southern West Virginia Paving Inc. located in Summersville, West

Virginia, a wearing course mix with a nominal maximum aggregate size of 9.5 mm and

an asphalt binder content of 6.7% was used. The second mix design was supplied by

Greer Industries, Inc. from Clarksburg, West Virginia. This mix design had a nominal

maximum aggregate size of 12.5 mm and an asphalt binder content of 5.4%. Both mixes

consisted of 100% limestone and were blended from aggregates located in 3 separate

stockpiles at each location. Both mixes were designed with PG 76-22 modified asphalt

binders. Gradation and weighout information for each mix design are presented in

Appendix A.

The primary experimental design is shown in Figure 3.1. The factors and levels of the

experiment are shown in Table 3.1.

25

Table 3.1 Experiment Factors and Levels

Factor Level

Mix Type (Aggregate Size) 9.5, 12.5

Mixing Temperature Low, High

Cure Time (Hrs) 2,4

Compaction Temperature Low, High

Mold Preheat (Hours) 0.5, 2

Binder Type PG 64-22, PG 76-22

With seven factors and two levels, there are 64 combinations. The one half factorial

shown on Figure 3.1 results in 32 combinations. In accordance with industry practice,

the average results of two compaction pills are treated as one sample for bulk specific

gravity. Thus the experiment required preparation of 64 compacted pills. Only one unit

is used as a sample for the maximum theoretical specific gravity test so 32 samples were

prepared. The order of sample preparation and testing was randomized as shown in Table

3.1.

The Gmb test method, AASHTO T166, requires cooling the samples for 16 ± 1 hr or

“cooling in front of a fan” for an unspecified time. The common practice in West

Virginia is to cool the sample until they can be readily handled. To evaluate if this

process affects the volumetric parameters, each Gmb sample was tested twice: after

cooling in front of a fan for 1 hour, and 2.) after 24 hours at room temperature. This did

not require preparation of new samples. Since the two observations of Gmb were from the

same sample a paired Student t-test was used for the statistical analysis.

The between sample compaction and measurement of weights to determine Gmb , was not

included in the fractional factorial. For this evaluation, the same samples were measured

at different times. The two times were 1 and 24 hours after compaction. A paired

Student’s t test was performed to determine if any significant differences existed between

the two sets of data.

26

Figure 3.1 Fractional Factorial Design

27

Table 3.2 Parameters for Each Sample Tested in the Fractional Factorial

Pill Number Aggregate Size

(mm)

Mix

Temperature (oC) Cure Time (hrs)

Compaction Temperature

(oC)

Mold Preheat

Time (hrs)

Binder Type

(PG)

1 9.5 154 2 142 0.5 64-22

2 12.5 160 2 142 0.5 64-22

3 12.5 154 4 142 0.5 64-22

4 9.5 160 4 142 0.5 64-22

5 12.5 154 2 147 0.5 64-22

6 9.5 160 2 147 0.5 64-22

7 9.5 154 4 147 0.5 64-22

8 12.5 160 4 147 0.5 64-22

9 12.5 154 2 142 2 64-22

10 9.5 160 2 142 2 64-22

11 9.5 154 4 142 2 64-22

12 12.5 160 4 142 2 64-22

13 9.5 154 2 147 2 64-22

14 12.5 160 2 147 2 64-22

15 12.5 154 4 147 2 64-22

16 9.5 160 4 147 2 64-22

17 12.5 160 2 149 0.5 76-22

18 9.5 177 2 149 0.5 76-22

19 9.5 160 4 149 0.5 76-22

20 12.5 177 4 149 0.5 76-22

21 9.5 160 2 160 0.5 76-22

22 12.5 177 2 160 0.5 76-22

23 12.5 160 4 160 0.5 76-22

24 9.5 177 4 160 0.5 76-22

25 9.5 160 2 149 2 76-22

26 12.5 177 2 149 2 76-22

27 12.5 160 4 149 2 76-22

28 9.5 177 4 149 2 76-22

29 12.5 160 2 160 2 76-22

30 9.5 177 2 160 2 76-22

31 9.5 160 4 160 2 76-22

32 12.5 177 4 160 2 76-22

28

3.2 AGGREGATE PROCESSING

Once the mix design information was obtained, the amount of aggregates needed from

each stockpile was calculated from the percentages given in the mix designs. It was

determined that approximately 250 kg of aggregate from each location would be required

to produce the samples. Therefore, the 250 kg was multiplied by the respective

percentages for each stockpile at each location in order to determine the amount of

aggregate necessary from each stockpile, as shown in Table 3.2.

Table 3.3 Stockpile Information

9.5 mm Nominal Maximum

Aggregate Size Mix

Stockpile Percentage of Mix Weight (kg)

CA1

40% 100

FA1

45% 112.5

FA2

15% 37.5

12.5 mm Nominal Maximum

Aggregate Size Mix

Stockpile Percentage of Mix Weight (kg)

A67 20% 50

A8 45% 112.5

B1 35% 87.5

The aggregates were obtained from the suppliers and processed in preparation for the

production of asphalt samples. The aggregates were sieved in accordance with AASHTO

T27-99 to separate the aggregates into their respective sizes. A Mary Ann Mechanical

Laboratory Sieve Shaker was used to separate the aggregate into materials retained on

12.5 mm, 9.5 mm, 4.75 mm 2.36 mm, 1.18 mm, 0.600 mm, 0.300 mm, 0.150 mm, 0.075

mm sieves and the pan. The sieved material was washed in accordance with AASHTO

T11-96. The washed aggregates were dried in an oven at 110 ± 5 C for 24 hours. Once

29

dried, the aggregates were allowed to cool and were then placed into separate containers

according to size.

The weights of the aggregates from each stockpile for each sample were computed using

a Microsoft Excel spreadsheet. Once the weights of each size of each aggregate from

each stockpile were determined, the appropriate amounts were weighed out in metal

rectangular pans. Sufficient material was prepared to make the two Gmb samples and one

Gmm sample needed for each combination of factors and levels.

3.3 MIX PREPARATION

For this project, a total of 64 Gmb and 32 Gmm samples were produced in order to examine

the interactions of the different design parameters. The Gmb, or pill, samples were

produced in identical pairs and the Gmb of each pill was averaged together to determine

the Gmb for the sample. A Gmm, or Rice sample, was produced for every pair of pills.

The samples were prepared in accordance with AASHTO T312-03 in the random order

identified in Table 3.1. The aggregates and binder, in separate containers, along with the

bucket mixer bucket and mixing wand were heated to the specified mixing temperature.

Once heated the aggregates were poured into the mixer bucket and a small crater formed

in the middle of the aggregate. Once the bucket containing the aggregate was placed on

the digital scale, the proper amount of the asphalt binder was added. The sample was

then mixed thoroughly with the mechanical bucket mixer.

After mixing the asphalt concrete was poured from the mechanical mixer bucket onto a

table and quartered. Quartering consists of mixing the sample and separating the sample

into four equal-sized portions. Once quartered, a preheated trowel was used to place mix

from portions from opposite sides of the sample in a tared container on the digital scale.

The sample was then requartered and the process repeated for the second pill and again

for the Rice sample. The Gmm samples for the 12.5 mm mix weighed 1500g, and the 9.5

mm Gmm samples weighed 1000g. The samples were then placed into the oven and

heated to the appropriate compaction temperature for the specified curing time.

30

3.4 SPECIMEN FABRICATION

The Gmm samples were produced in accordance with AASHTO 209-99. The Gmb samples

were produced in accordance with AASHTO T312-03. Compaction was accomplished

by the SuperPave Gyratory Compactor (SGC). At the specified time prior to compaction

of the sample, the SGC mold, base plate, and upper plate were placed in the oven at the

specified compaction temperature. Once heated to compaction temperature, the mold

was removed from the oven and the base plate was placed into the mold along with a

piece of release paper. The weighed out mixture for a single Gmb sample was placed in a

preheated transfer tray and transferred into the mold in one lift. Release paper was placed

on top of the mix along with the upper mold plate. If necessary, the top of the upper plate

was dusted with powdered graphite. The mold was then set into the SGC and allowed to

run at a vertical consolidation pressure of 600 kPa, a fixed angle of 1.25o, ,and a speed of

gyration of 30 rpm for 100 gyrations. Once compacted, the sample was removed from

the gyratory mold and set on a table in front of a fan to continue cooling for one hour. At

this point, the mass of the dry, submerged, and saturated surface dry (SSD) were

measured. The samples were allowed to cool at room temperature for 24 hours and the

masses were remeasured.

3.5 TESTING PROCEDURE

3.5.1 Test for Maximum Theoretical Specific Gravity

Once separated, the sample was placed into the pycnometer and weighed. Water was then

placed into a pycnometer and hooked up to the vacuum machine. The vacuum machine

removes air trapped in the sample by gradually increasing the vacuum pressure until the

manometer reads 3.7± 0.3 kPa. Once this pressure is attained, this pressure is maintained

for 15 ± 2 minutes. At this point, the sample was placed in the constant temperature

water bath (25oC (77oF)) for 10 minutes. After the 10 minutes in the water bath, the

submerged weight was taken and recorded. From these recorded weights, the Theoretical

Maximum Specific Gravity, Gmm, was determined.

)( EDAAGmm −−

=

31

Where:

A = mass of oven-dry sample in air, g

D = mass of submerged sample and pycnometer at 25oC, g

E = mass of pycnometer submerged in water at 25oC, g

3.5.2 Test for Bulk Specific Gravity

The Bulk Specific Gravity values were determined in accordance with AASHTO T166-

00. After cooling for the specified time, the pill was placed on a digital scale and the dry

mass was recorded. The pill was then submerged in the constant temperature water bath

(25oC (77oF) for 4 1± minutes and the submerged weight was recorded. The SSD weight

was determined by removing the specimen from the constant temperature water bath and

quickly blotting the specimen with a moist towel. The sample was immediately placed

on the digital scale and that weight recorded as the saturated surface dry (SSD) weight.

Once these weights were determined and recorded, the Gmb was then determined with the

equation found below:

CBAGmb −

=

Where:

A = mass of dry sample, g

B = mass of saturated surface dry sample, g

C = mass of submerged sample, g

Once the Bulk Specific Gravity was calculated, the air voids (VTM) for each sample was

determined using the equation found below:

−⋅=

mm

mb

GGVTM 1100(%)

Immediately after the SSD weight was recorded, the pills were placed on a shelf with a

fan blowing air on them and allowed to dry overnight. Twenty-four hours later, the pills’

32

dry, submerged, and SSD weights were recorded again and the new Gmb was calculated

and recorded. This Gmb value was used to compute new VTM values.

33

CHAPTER 4: RESULTS AND ANALYSIS

4.1 INTRODUCTION

For this project, a statistics software package for data analysis developed by JMP, which

is a division of the SAS Institute Inc., was used. This program was used to perform an

analysis of variance of the fractional factorial design in order to determine the significant

factors affecting the percentage of air voids in hot mix asphalt concrete.

The samples were fabricated for 12.5 mm and 9.5 mm Nominal Maximum Aggregate

Sizes (NMAS), with both the gradation and asphalt binder content specified by the

contractor. Table 4.1 illustrates the difference in the contractor’s results and those

obtained in the laboratory. As can be seen, the samples produced with the 12.5 NMAS

yielded acceptable air voids while those made with the 9.5 NMAS mix design were

almost 50% below the target value of 4%. The reason for the low air void content was

not investigated. Figure 4.1 is a summary of all the air void data collected during the

experiment.

Table 4.1 Comparison of Contractor’s and WVU Asphalt Lab’s Results

Result 12.5 NMAS 9.5 NMAS

Criteria Contractor WVU Asphalt Lab Criteria Contractor WVU Asphalt Lab

Percent Binder

(Pb

) - 5.4 5.4 - 6.7 6.7

VTM (%) 4.0 4.0 3.64 4.0 4.0 2.05

34

Figure 4.1 Summary of Results (See Figure 3.1 for Sample Designations)

4.2 EFFECT OF TIME TO DETERMINE BULK SPECIFIC GRAVITY

Using Microsoft Excel, a student’s paired, two-tailed T-Test was used to analyze the

VTM values determined 1 hour and 24 hours after compaction. It was assumed that the

distributions from each set of data were normally distributed with identical variances. As

can be seen in Table 4.2, the calculated t Stat value is well below the t Critical value thus

35

there is insufficient evidence to reject the null hypothesis of equal means at a confidence

level of 95%).

Table 4.3 Student’s Paired T-Test Results for VTM Values

Terms Variable 1 Variable 2

Mean 0.0284 0.029

Variance 8.02E-05 8.18E-05

Observations 32 32

Hypothesized Mean Difference 0

df 31

t Stat -1.252

P(T<=t) two-tail 0.220

t Critical two-tail 2.040

4.3 ANALYSIS OF VARIANCE

The JMP data analysis software package was used to analyze the data obtained in the

laboratory and yielded results which illustrated the parameters’ effects on the air voids

after 1 hour in each sample. The data output is included in Tables 4.4 and 4.5.

Table 4.4 contains numeric summaries of the multiple regression model. The Rsquare

term indicates the percentage of variability that is explained by the linear model (not

random error). If the Rsquare value is 1, then all of the variability is explained by the

linear model (data falls exactly on a straight line). If Rsquare is equal to 0, then none of

the variability in y is explained by the linear model (no relationship exists between the

variables). From Table 4.4, it can be seen that 94.6% of the variability can be explained

by the linear model, meaning the vast majority of the variability is explained by the linear

model. The Rsquare Adj. term in Table 4.4 makes it more comparable than models with

different numbers of parameters. Due to the fact that adding terms to an existing model

always increases Rsquare the adjusted Rsquare compensates for adding terms to a model

36

that already has terms in it. The Root Mean Square Error term is the distance, on

average, of a data point from the fitted line, measured along a vertical line. The Mean of

Response is simply the average of all the recorded VTM values and the Observations

term represents the number of samples produced.

Table 4.4 Summary of Fit Data

Summary of Fit Data

Rsquare 0.946

Rsquare Adj 0.834

Root Mean Square Error 0.365

Mean of Response 2.843

Observations 32

37

Table 4.5 ANOVA Parameter Estimates

Parameter Estimates

Term Estimate Std Error t Ratio Prob > ltl

Intercept 2.842813 0.064542 44.05 < 0.0001

Main Parameters for

Experiment

Aggregate Size -0.795937 0.064542 -12.33 < 0.0001

Mixing Temperature -0.078438 0.064542 -1.22 0.2522

Cure Time -0.064687 0.064542 -1.00 0.3399

Compaction Temperature 0.048438 0.064542 0.75 0.4703

Mold Preheat Time -0.044688 0.064542 -0.69 0.5045

Binder Type 0.042188 0.064542 0.65 0.5281

Combinations of

Parameters for

Experiment

Aggregate Size & Mixing Temperature 0.176563 0.064542 2.74 0.0210

Aggregate Size & Cure Time -0.062188 0.064542 -0.96 0.3580

Aggregate Size & Compaction Temperature 0.019688 0.064542 0.31 0.7666

Aggregate Size & Mold Preheat Time 0.039063 0.064542 0.61 0.5585

Aggregate Size & Binder Type -0.064063 0.064542 -0.99 0.3443

Mixing Temperature & Cure Time -0.119687 0.064542 -1.85 0.0934

Mixing Temperature & Compaction Temperature -0.061562 0.064542 -0.95 0.3627

Mixing Temperature & Mold Preheat Time -0.048348 0.064542 -0.75 0.4703

Mixing Temperature & Binder Type -0.002812 0.064542 -0.04 0.9661

Cure Time & Compaction Temperature -0.022813 0.064542 -0.35 0.7311

Cure Time & Mold Preheat Time 0.062813 0.064542 0.97 0.3534

Cure Time & Binder Type -0.124062 0.064542 -1.92 0.0835

Compaction Temperature & Mold Preheat Time -0.011562 0.064542 -0.18 0.8614

Compaction Temperature & Binder Type 0.059063 0.064542 0.92 0.3817

Mold Preheat Time & Binder Type 0.012188 0.064542 0.19 0.8540

The Parameter Estimates, Table 4.5, shows the estimates of the parameters in the linear

model and a t-test for the hypothesis that each parameter is zero. The Prob > ltl values

give the probability of observing a t-value as large or larger than the computed t-value

under the null hypothesis (i.e., parameter equals 0). A Prob > ltl value of 0.05 or less

would indicate that the parameter estimate is different from the null hypothesis value at

the 95% level. A small Prob > ltl value means that the data provides evidence against the

null hypothesis. Therefore, if a Prob > ltl value is less than 0.05, the term that value is

representing had a significant effect on the VTM of the samples. As can be seen on

38

Table 4.5, the only terms that had a significant effect on the VTM values was the NMAS

and the interaction of mix temperature and NMAS.

The fact that NMAS has a significant effect on VTM is an artifact of the experiment. As

discussed in Chapter 3, the VTM of the 9.5 mm mix was an average of 2.05 percent and

the VTM of the 12.5 mm mix was 3.64 percent. Since only two mix types were included

in the experiment, the fact that there is a difference in the VTM based on mix type

confounds the experiment. The consequence of this confounding is that the statistical

relationship between VTM and NMAS is an artifact of the experiment and not a

statistically significant event. This confounding also explains the results for the NMAS –

mix temperature interaction term.

39

CHAPTER 5 CONCLUSIONS AND RECOMMENDATIONS

This research project has yielded results showing that only one of the design parameters,

NMAS, and one of the interactions, NMAS and mixing temperature, had significant

effects on the air void levels of the asphalt concrete test specimens. However, this result

was produced by the experimental design. Future research should include a wider range

of mix designs to further evaluate the effects these parameter interactions have on the air

voids in asphalt concrete.

5.1 CONCLUSIONS

The mixing temperature parameter had no significant effect on the air voids of asphalt

concrete. The experiment implemented mixing temperatures of 154 and 160oC, and 160

and 177oC for the PG 64-22 and PG 76-22 binders, respectively. This conclusion is

consistent with the literature when the mixes are prepared at “reasonable” mixing

temperatures.

The compaction temperature parameter had no significant effects on the air voids of

asphalt concrete. The experiment implemented compaction temperatures of 142 and

147oC, and 149 and 160oC for the PG 64-22 and PG 76-22 binders, respectively. Future

research may include a wider range of temperatures interacting with various experimental

parameters to further explore the effects, if any, on air voids of asphalt concrete.

The binder types did not have a significant effect on the air voids of asphalt concrete.

The experiment evaluated mixes with PG 64-22 and PG 76-22 binders. The mixing and

compaction temperatures were selected based on a range around the equiviscosity

temperatures of the binders as recommended by the asphalt cement supplier.

The varying cure times did not have a significant effect on the air voids of asphalt

concrete. The experiment implemented cure times of 2 and 4 hours. Future research may

include a shorter duration of cure times. This may be an important issue for quality

control of field mixes as currently there is not a WVDOH minimum curing time for

mixes produced at asphalt plants.

40

The mold preheat times were believed to have had no significant effects on the air voids

of asphalt concrete. The experiment implemented mold preheat times of 0.5 and 2 hours.

The time between preparation of the Gmb sample and measurement of the masses to

determine the Gmb had no significant effects on the air voids of asphalt concrete. The

experiment implemented VTM determination times of 1 and 24 hours. It appears the

current practice of allowing the samples to cool until they can be “readily handled” is not

affecting the test results.

5.2 RECOMMENDATIONS

The research reported herein indicates that several of the mix preparation procedures

included in the SuperPave design method did not affect the VTM of the samples. This

could lead to the conclusion that the testing protocol could be revised to facilitate the

preparation of samples for both mix design and field quality control. This could have a

major influence on the time required to perform a mix design and hence could lead to a

more efficient mix design methodology. This could result in a significant savings to the

industry without sacrificing quality. However, the number of mixes used in this research

is too limited to recommend changes to the nationally adopted AASHTO procedures.

The research concept demonstrated in this research should be expanded to include more

mix types and replicate mix designs for each mix type in the Superpave methodology.

41

REFERENCES

"ARTBA’S Research on Industry Growth & Superpave 2000: Where We are Now." Better Roads Jan. 2000. 30 Jan. 2005 <http://obr.gcnpublishing.com/articles/brsearch00.htm>. Bell, C.A., Y. Abwahab, M.E. Cristi, and D. Sosnovske. Selection of Laboratory Aging Procedures for Asphalt-Aggregate Mixtures. Oregon State University. Washington, DC: Strategic Highway Research Program, 1994. Buchanan, Shane M., and Jimmy Brumfield. "Investigation of the Gyration Angle of Superpave Gyratory Compactors." Journal of Materials in Civil Engineering 16 (2004): 444-451. Horan, Robert D. "Asphalt Mix Curing At the Design Lab and At the Field Lab." Asphalt Magazine 2001: 22-24. 20 Sept. 2005 <http://www.asphaltinstitute.org/upload/Asphalt_Mix_Curing.pdf>. Mostafa, Elseifi. Viscoelastic Modeling of Straight and Modified Binders at Itermediate and High Temperatures. Virginia Polytechnic Institute, 1999. Stuart, Kevin D. Methodology for Determining Compaction Temperatures for Modified Asphalt Binders. Turner-Fairbank Highway Research Center. McLean, Va: Federal Highway Administration, 2001. Tandon, V., and I. Avelar. SUPERPAVE Practices: Adoption, Issues, and Benefits. Diss. Universtity of Texas at El Paso, 2002. 27 Sept. 2005 <http://ctis.utep.edu/publications/Reports/SuperpaveLongReport.pdf>. Yildirim, Y., M. Solaimanian, and T. Kennedy. Mixing and Compaction Temperatures for Hot Mix Asphalt Concrete. Diss. The Univ. of Texas at Austin, 2000. 10 Aug. 2005 <http://www.utexas.edu/research/ctr/pdf_reports/1250_5.pdf>.

42

APPENDIX A - MIX DESIGN

Table A.1 19.5 NMAS Mix Design Gradation and Weighout Information

Seive Stockpile

CA1

FA1

FA2

1 25 100 100 100

3/4 19 100 100 100

1/2 12.5 100 100 100

3/8 9.5 91.8 100 100

No.4 4.75 29 92.4 100

No.8 2.35 7.4 61.3 90.5

No.16 1.18 5.4 37.8 52.2

No30 0.6 4.9 23.9 27.5

No.50 0.3 4.8 14.3 12.5

No.200 0.075 2.7 8 3.3

Stockpile Percentages Total

40% 45% 15% 100%

Sample Weight Pb Total Agg. Wt.

Pill 4650 6.70%

Rice 1000

10300 690.1 9609.9

43

Table A.2 12.5 NMAS Mix Design Gradation and Weighout Information

Seive Stockpile

A67 A8 B1

1 25 100 100 100

3/4 19 100 100 100

1/2 12.5 66 100 100

3/8 9.5 40 92 100

No.4 4.75 8 24 100

No.8 2.35 4 6 82

No.16 1.18 3 5 48

No30 0.6 2 4 25

No.50 0.3 2 3 15

No.200 0.075 1.4 1.5 8

Stockpile Percentages Total

20% 45% 35% 100%

Sample Weight Pb Total Agg. Wt.

Pill 4750 5.40%

Rice 1500

11000 594 10406

44

APPENDIX B - TEST RESULTS

Table B.1 Effect Tests (JMP Output)

Term Nparm DF F Ratio Prob > F

Main Parameters for

Experiment

Aggregate Size 1 1 152.08 < 0.0001

Mixing Tempe

rature 1 1 1.48 0.2522

Cure Time 1 1 1.00 0.3399

Compaction Temperature 1 1 0.56 0.4703

Mold Preheat Time 1 1 0.48 0.5045

Binder Type 1 1 0.43 0.5281

Combinations of

Parameters for

Experiment

Aggregate Size & Mixing Temperature 1 1 7.48 0.0210

Aggregate Size & Cure Time 1 1 0.93 0.3580

Aggregate Size & Compaction Temperature 1 1 0.09 0.7666

Aggregate Size & Mold Preheat Time 1 1 0.37 0.5585

Aggregate Size & Binder Type 1 1 0.99 0.3443

Mixing Temperature & Cure Time 1 1 3.44 0.0934

Mixing Temperature & Compaction Temperature 1 1 0.91 0.3627

Mixing Temperature & Mold Preheat Time 1 1 0.56 0.4703

Mixing Temperature & Binder Type 1 1 0.00 0.9661

Cure Time & Compaction Temperature 1 1 0.12 0.7311

Cure Time & Mold Preheat Time 1 1 0.95 0.3534

Cure Time & Binder Type 1 1 3.69 0.0835

Compaction Temperature & Mold Preheat Time 1 1 0.03 0.8614

Compaction Temperature & Binder Type 1 1 0.84 0.3817

Mold Preheat Time & Binder Type 1 1 0.04 0.8540

Table B.2 Least Squares Means Tables (JMP Output)

Aggregate Size Mix Temperature

Level Least Sq. Mean Std. Error Mean Level Least Sq.

Mean Std. Error Mean

1 2.05 0.913 2.05 1 2.76 0.913 2.76 2 3.64 0.913 3.64 2 2.92 0.913 2.92

45

Cure Time Compaction Temperature

Level Least Sq. Mean Std. Error Mean Level Least Sq.

Mean Std. Error Mean

1 2.78 0.913 2.78 1 2.89 0.913 2.89 2 2.91 0.913 2.91 2 2.79 0.913 2.79 Mold Preheat Time Binder Type

Level Least Sq. Mean Std. Error Mean Level Least Sq.

Mean Std. Error Mean

1 2.80 0.913 2.80 1 2.89 0.913 2.89 2 2.89 0.913 2.89 2 2.80 0.913 2.80 Aggregate Size & Mix Temperature Aggregate Size & Cure Time

Level Least Sq. Mean Std. Error Mean Level Least Sq.

Mean Std. Error Mean

1,1 2.15 0.129 2.15 1,1 1.92 0.129 1.92 1,2 1.95 0.129 1.95 1,2 2.17 0.129 2.17 2,1 3.38 0.129 3.38 2,1 3.64 0.129 3.64 2,2 3.89 0.129 3.89 2,2 3.64 0.129 3.64 Aggregate Size & Compaction Temperature Aggregate Size & Mold Preheat Time

Level Least Sq. Mean Std. Error Mean Level Least Sq.

Mean Std. Error Mean

1,1 2.12 0.129 2.12 1,1 2.04 0.129 2.04 1,2 1.98 0.129 1.98 1,2 2.05 0.129 2.05 2,1 3.67 0.129 3.67 2,1 3.56 0.129 3.56 2,2 3.61 0.129 3.61 2,2 3.72 0.129 3.72 Aggregate Size & Binder Type Mix Temperature & Cure Time

Level Least Sq. Mean Std. Error Mean Level Least Sq.

Mean Std. Error Mean

1,1 2.03 0.129 2.03 1,1 2.58 0.129 2.58 1,2 2.07 0.129 2.07 1,2 2.95 0.129 2.95 2,1 3.75 0.129 3.75 2,1 2.98 0.129 2.98 2,2 3.53 0.129 3.53 2,2 2.87 0.129 2.87

46

Table B.2 Least Squares Means Tables (JMP Output) Continued

Mix Temperature & Compaction Temperature Mix Temperature & Mold Preheat Time

Level Least Sq. Mean Std. Error Mean Level Least Sq. Mean Std. Error Mean

1,1 2.75 0.129 2.75 1,1 2.67 0.129 2.67

1,2 2.78 0.129 2.78 1,2 2.86 0.129 2.86

2,1 3.03 0.129 3.03 2,1 2.93 0.129 2.93

2,2 2.81 0.129 2.81 2,2 2.92 0.129 2.92

Mix Temperature & Binder Type Cure Time and Compaction Temperature

Level Least Sq. Mean Std. Error Mean Level Least Sq. Mean Std. Error Mean

1,1 2.80 0.129 2.80 1,1 2.80 0.129 2.80

1,2 2.73 0.129 2.73 1,2 2.73 0.129 2.73

2,1 2.97 0.129 2.97 2,1 2.98 0.129 2.98

2,2 2.88 0.129 2.88 2,2 2.84 0.129 2.84

Cure Time and Mold Preheat Time Cure Time and Binder Type

Level Least Sq. Mean Std. Error Mean Level Least Sq. Mean Std. Error Mean

1,1 2.80 0.129 2.80 1,1 2.70 0.129 2.70

1,2 2.76 0.129 2.76 1,2 2.86 0.129 2.86

2,1 2.80 0.129 2.80 2,1 3.07 0.129 3.07

2,2 3.02 0.129 3.02 2,2 2.74 0.129 2.74

Compaction Temperature & Mold Preheat Time Compaction Temperature & Binder Type

Level Least Sq. Mean Std. Error Mean Level Least Sq. Mean Std. Error Mean

1,1 2.84 0.129 2.84 1,1 2.99 0.129 2.99

1,2 2.95 0.129 2.95 1,2 2.79 0.129 2.79

2,1 2.76 0.129 2.76 2,1 2.78 0.129 2.78

2,2 2.83 0.129 2.83 2,2 2.81 0.129 2.81

Mold Preheat Time & Binder Type

Level Least Sq. Mean Std. Error Mean

1,1 2.85 0.129 2.85

1,2 2.74 0.129 2.74

2,1 2.92 0.129 2.92

2,2 2.86 0.129 2.86

47

Aggregate Size

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

LEVEL

VTM

(%)

2 1

Figure B.1 Least Mean Squares Plots Aggregate Size

Mix Temperature

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

LEVEL

VTM

(%)

2 1

Figure B.2 Least Mean Squares Plots Mix Temperature

48

Cure Time

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

LEVEL

VTM

(%)

2 1

Figure B.3 Least Mean Squares Plots Cure Time

Compaction Temperature

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

LEVEL

VTM

(%)

2 1

49

Figure B.4 Least Mean Squares Plots Compaction Temperature

Binder Type

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

LEVEL

VTM

(%)

2 1

Figure B.5 Least Mean Squares Plots Binder Type

50

Mold Preheat Time

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

LEVEL

VTM

(%)

2 1

Figure B.6 Least Mean Squares Plots Mold Preheat Time

Aggregate Size and Mix Temperature

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

LEVEL

VTM

(%)

2 1

Figure B.7 Least Mean Squares Plots Agggregate Size and Mix Temperature

51

Aggregate Size and Cure Time

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

LEVEL

VTM

(%)

2 1

Figure B.8 Least Mean Squares Plot Aggregate Size and Cure Time

Aggregate Size and Compaction Temperature

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

LEVEL

VTM

(%)

2 1

Figure B.9 Least Mean Squares Plots Aggregate Size and Compaction Temperature

52

Aggregate Size and Mold Preheat Time

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

LEVEL

VTM

(%)

2 1

Figure B.10 Least Mean Squares Plots Aggregate Size and Mold Preheat Time

Aggregate Size and Binder Type

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

LEVEL

VTM

(%)

2 1

53

Figure B.11 Least Mean Squares Plots Aggregate Size and Binder Type

Mixing Temperate and Compaction Temperature

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

LEVEL

VTM

(%)

2 1

Figure B.12 Least Mean Squares Plots Mixing and Compaction Temperature

54

Mixing Temperate and Cure Time

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

LEVEL

VTM

(%)

2 1

Figure B.13 Least Mean Squares Plots Mix Temperature and Cure Time

Mixing Temperate and Mold Preheat Time

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

LEVEL

VTM

(%)

2 1

Figure B.14 Least Mean Squares Plots Mixing Temperature and Mold Preheat Time

55

Mixing Temperature and Binder Type

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

LEVEL

VTM

(%)

2 1

Figure B.15 Least Mean Squares Plots Mixing Temperature and Binder Type

Cure Time and Compaction Temperature

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

LEVEL

VTM

(%)

2 1

56

Figure B.16 Least Mean Squares Plots Cure Time and Compaction Temperature

Cure Time and Mold Preheat Time

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

LEVEL

VTM

(%)

2 1

Figure B.17 Least Mean Squares Plots Cure Time and Mold Preheat Time

57

Cure Time and Binder Type

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

LEVEL

VTM

(%)

2 1

Figure B.18 Least Mean Squares Plots Cure Time and Binder Type

Compaction Temperature and Mold Preheat Time

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

LEVEL

VTM

(%)

2 1

Figure B.19 Least Mean Squares Plots Compaction Temperature and Mold Preheat Time

58

Compaction Temperature and Binder Type

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

LEVEL

VTM

(%)

2 1

Figure B.20 Least Mean Squares Plots Compaction Temperature and Binder Type

Binder Type & Mold Preheat Time

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

LEVEL

VTM

(%)

2 1

Figure B.21 Least Mean Squares Plots Binder Type and Mold Preheat Time

59

Table B.3 Data Sheet for VTM Determination After 1 Hour

Sample

Rice Pill 1 Pill 2

Avg. Air Voids (%) Dry Weight (g)

Submerged Weight

(g)

Weight of

Pycnometer in

Water (g)

Gmm

Dry Weight

(g) Submerged Weight (g) SSD Weight (g) G

mb Air Voids (%) Dry Weight (g) Submerged Weight (g) SSD Weight (g) G

mb Air Voids (%)

1 1192.9 2029.1 1330 2.416 4616.7 2672.1 4620.9 2.369 1.94% 4671.1 2702.4 4672.2 2.371 1.84% 1.89%

2 1516.4 2235 1330 2.480 4741.1 2765.3 4747.8 2.391 3.58% 4758.2 2770.4 4768.9 2.381 4.00% 3.79%

3 1514.7 2233.4 1330 2.478 4762.6 2779.6 4769.6 2.393 3.41% 4750 2774.6 4759 2.394 3.40% 3.40%

4 1145.2 2001.9 1330 2.420 4650.9 2692.4 4655.8 2.369 2.10% 4651.7 2691 4656.9 2.366 2.21% 2.15%

5 1511.3 2230.8 1330 2.476 4747.3 2770.5 4755 2.392 3.37% 4736.5 2772.8 4746.1 2.400 3.04% 3.20%

6 1024.3 1929 1330 2.408 4668.4 2696.9 4672.5 2.363 1.88% 4659.6 2695.3 4662.2 2.369 1.64% 1.76%

7 1069.5 1959.2 1330 2.429 4661.6 2696 4667.9 2.364 2.68% 4648.8 2690.7 4652.7 2.369 2.45% 2.57%

8 1528.2 2242.7 1330 2.483 4734.9 2757.7 4748.9 2.378 4.23% 4722.8 2755.4 4734.5 2.386 3.89% 4.06%

9 1508.7 2228.7 1330 2.473 4746.5 2763.1 4755.9 2.382 3.70% 4751.8 2767.8 4762.4 2.382 3.68% 3.69%

10 1108.5 1977.1 1330 2.402 4640.5 2679 4650.9 2.353 2.05% 4666.1 2693.6 4678.2 2.351 2.14% 2.09%

11 1083.7 1966.5 1330 2.423 4652.7 2692.2 4659.3 2.365 2.40% 4638.4 2678.7 4646.1 2.358 2.71% 2.55%

12 1537.6 2250.1 1330 2.490 4744.5 2770.8 4757.6 2.388 4.10% 4740.8 2754.6 4751.5 2.374 4.66% 4.38%

13 1116 1980.2 1330 2.396 4636.1 2680.1 4642.2 2.363 1.38% 4666 2695.2 4671.7 2.361 1.47% 1.42%

14 1557.1 2258 1330 2.475 4739.4 2758.5 4747.8 2.382 3.74% 4737.5 2758.3 4746.4 2.383 3.72% 3.73%

15 1505.9 2227.7 1330 2.476 4714 2748.9 4723.5 2.387 3.58% 4711.2 2744.8 4723.5 2.381 3.84% 3.71%

16 1180.9 2022.4 1330 2.417 4625 2680.4 4628.1 2.375 1.77% 4681.7 2713.6 4685.1 2.375 1.77% 1.77%

17 1567.3 2263.2 1330 2.472 4737.4 2770.2 4748.2 2.395 3.10% 4741.2 2770.4 4751.9 2.393 3.19% 3.15%

18 1042.8 1939.5 1330 2.407 4636.1 2672.4 4643.4 2.352 2.26% 4646.2 2675.2 4654.2 2.348 2.45% 2.36%

19 1014.9 1926.3 1330 2.425 4640.6 2689.9 4645.5 2.373 2.13% 4654.9 2696.5 4661.4 2.369 2.29% 2.21%

20 1544.1 2251 1330 2.478 4740.8 2767.6 4752 2.389 3.59% 4747.8 2771 4763.9 2.382 3.86% 3.73%

21 1001.1 1917.1 1330 2.418 4633.7 2689.5 4645.5 2.369 2.03% 4640.4 2688.8 4647.4 2.369 2.02% 2.03%

22 1514.3 2237.1 1330 2.494 4740.7 2768.6 4752.5 2.390 4.18% 4737.5 2766.1 4749 2.389 4.20% 4.19%

23 1527.8 2240.3 1330 2.474 4741.6 2780.6 4751.9 2.405 2.78% 4736.7 2776.8 4751.7 2.398 3.06% 2.92%

24 1020.4 1926 1330 2.404 4647.6 2693.6 4650 2.376 1.20% 4672 2704.2 4677.5 2.368 1.53% 1.36%

25 1013.3 1921.9 1330 2.405 4634 2687.1 4648 2.363 1.72% 4630 2682.5 4640.3 2.365 1.65% 1.69%

26 1566.7 2265.3 1330 2.481 4738.7 2768.5 4749.9 2.392 3.62% 4738.3 2762.9 4750.4 2.384 3.92% 3.77%

27 1507.4 2226.6 1330 2.468 4720.2 2754.6 4734.1 2.385 3.38% 4740.1 2765.7 4755.5 2.382 3.47% 3.43%

28 1039.6 1937.8 1330 2.408 4647.7 2680.4 4653.5 2.356 2.16% 4647.1 2686 4651.7 2.364 1.81% 1.98%

29 1527.3 2240 1330 2.474 4741 2767.7 4753 2.388 3.48% 4748 2766.6 4758.4 2.384 3.65% 3.57%

30 1068 1954.5 1330 2.408 4644.7 2683.2 4651.8 2.359 2.02% 4641.2 2675.6 4646.8 2.355 2.23% 2.12%

31 1097.1 1975.4 1330 2.429 4631 2677.9 4638.2 2.362 2.74% 4642.3 2680.8 4648.7 2.359 2.87% 2.80%

32 1509.3 2230.1 1330 2.478 4732.4 2765.2 4745.7 2.389 3.55% 4730.5 2766.8 4744.3 2.392 3.44% 3.50%

60

Table B.4 Data Sheet for VTM Determination After 24 Hours

Sample

Rice Pill 1 Pill 2 Avg. Air Voids

(%) Dry Weight

(g)

Submerged

Weight (g)

Weight of Pycnometer

in Water (g) G

mm

Dry Weight

(g)

Submerged

Weight (g)

SSD Weight

(g) G

mb

Air Voids

(%) Dry Weight (g)

Submerged

Weight (g) SSD Weight (g) G

mb Air Voids (%)

1 1192.9 2029.1 1330 2.416 4617.7 2672 4624.8 2.365 2.12% 4672.3 2701.2 4677.2 2.365 2.12% 2.12%

2 1516.4 2235 1330 2.480 4742.3 2765.2 4751.1 2.388 3.72% 4759.5 2769.4 4770.6 2.378 4.11% 3.91%

3 1514.7 2233.4 1330 2.478 4763 2778.3 4768.9 2.393 3.43% 4751.2 2771.6 4757.7 2.392 3.45% 3.44%

4 1145.2 2001.9 1330 2.420 4651.8 2689 4658.5 2.362 2.38% 4653.2 2690.6 4659 2.364 2.30% 2.34%

5 1511.3 2230.8 1330 2.476 4749.6 2769.9 4753.6 2.394 3.28% 4739.2 2772.6 4745.6 2.402 2.97% 3.12%

6 1024.3 1929 1330 2.408 4668.9 2694.1 4672.8 2.360 2.03% 4659.9 2691.8 4662.4 2.365 1.81% 1.92%

7 1069.5 1959.2 1330 2.429 4662.2 2701.6 4664.7 2.375 2.23% 4649.4 2690.7 4652 2.371 2.41% 2.32%

8 1528.2 2242.7 1330 2.483 4737.6 2755.7 4749.5 2.376 4.30% 4724.9 2753.7 4736.8 2.383 4.04% 4.17%

9 1508.7 2228.7 1330 2.473 4748.8 2760.9 4756.9 2.379 3.81% 4754.1 2766.6 4763.7 2.381 3.75% 3.78%

10 1108.5 1977.1 1330 2.402 4641.3 2678.1 4645.5 2.359 1.81% 4667.3 2692.5 4670.5 2.360 1.78% 1.79%

11 1083.7 1966.5 1330 2.423 4654 2692.7 4658 2.368 2.28% 4640.2 2676.7 4644.4 2.358 2.69% 2.48%

12 1537.6 2250.1 1330 2.490 4746.1 2768.2 4757.8 2.385 4.20% 4743 2751.5 4753.1 2.370 4.84% 4.52%

13 1116 1980.2 1330 2.396 4636.7 2678.8 4640.7 2.363 1.36% 4666.9 2700.3 4670.4 2.369 1.13% 1.24%

14 1557.1 2258 1330 2.475 4740.9 2758.6 4750 2.381 3.82% 4738.6 2758.6 4746.7 2.383 3.70% 3.76%

15 1505.9 2227.7 1330 2.476 4715.3 2747.3 4723.9 2.386 3.65% 4713.3 2744.5 4723.5 2.382 3.81% 3.73%

16 1180.9 2022.4 1330 2.417 4626.3 2681.3 4629.1 2.375 1.75% 4682.9 2712.3 4685.5 2.373 1.83% 1.79%

17 1567.3 2263.2 1330 2.472 4738.7 2770.4 4748.3 2.396 3.07% 4742.6 2768.9 4755.1 2.388 3.40% 3.23%

18 1042.8 1939.5 1330 2.407 4636.1 2672.4 4643.4 2.352 2.26% 4646.2 2675.2 4654.2 2.348 2.45% 2.36%

19 1014.9 1926.3 1330 2.425 4641.1 2689.2 4648 2.369 2.27% 4656 2694.3 4663.1 2.365 2.46% 2.37%

20 1544.1 2251 1330 2.478 4742.6 2766.1 4752.3 2.388 3.64% 4750.5 2771.4 4761.4 2.387 3.67% 3.66%

21 1001.1 1917.1 1330 2.418 4635.6 2686.5 4634.9 2.379 1.61% 4641.6 2686.5 4650.4 2.363 2.26% 1.94%

22 1514.3 2237.1 1330 2.494 4742.5 2768 4750.3 2.392 4.07% 4739.3 2765.8 4747.1 2.392 4.09% 4.08%

23 1527.8 2240.3 1330 2.474 4742.9 2779.5 4753.5 2.403 2.89% 4740.2 2771.7 4749.3 2.397 3.12% 3.01%

24 1020.4 1926 1330 2.404 4643.5 2688.2 4650.9 2.366 1.60% 4672.7 2703.1 4677.4 2.367 1.56% 1.58%

25 1013.3 1921.9 1330 2.405 4635.4 2686.4 4649.5 2.361 1.80% 4630.7 2682.2 4640.5 2.365 1.66% 1.73%

26 1566.7 2265.3 1330 2.481 4740.4 2767.1 4748.6 2.392 3.59% 4740 2763.7 4751.2 2.385 3.89% 3.74%

27 1507.4 2226.6 1330 2.468 4721.9 2755.1 4732.8 2.388 3.26% 4743.3 2764.2 4756 2.381 3.50% 3.38%

28 1039.6 1937.8 1330 2.408 4648.7 2683.2 4659.3 2.352 2.29% 4648 2685.9 4655.1 2.360 1.96% 2.13%

29 1527.3 2240 1330 2.474 4741.8 2766.9 4750.6 2.390 3.39% 4749.1 2766.6 4759.8 2.383 3.70% 3.54%

30 1068 1954.5 1330 2.408 4646 2681.4 4651.6 2.358 2.08% 4641.6 2681.4 4648.8 2.359 2.03% 2.05%

31 1097.1 1975.4 1330 2.429 4634.1 2671.6 4640.1 2.354 3.08% 4643.3 2678.9 4649.9 2.356 3.01% 3.04%

32 1509.3 2230.1 1330 2.478 4734.9 2762.6 4748.5 2.384 3.76% 4733 2765.6 4746.4 2.389 3.55% 3.66%