Contents
Summary 1
Chapter 1 : Introduction 3
1.1 Background 4
1.2 Synthesis Approach 5
Chapter 2 : Literature Review: Effects of Lift Thickness on Pavement Performance 6
2.1 Basics of Compaction 6
2.2 Evolution of Superpave 8
2.3 Relationships Between Lift Thickness, NMAS, and Air Voids 11
2.4 Performance Impacts 13
2.5 Costs and Benefits 19
2.6 Summary of Findings from Literature 21
Chapter 3 : Survey Results: Current Practices Regarding Lift Thicknesses 23
3.1 State DOT Survey Responses 23
3.2 Canadian Responses 34
3.3 Industry Survey Responses 35
3.4 Analysis and Summary of Survey Findings 43
Chapter 4 : Case Examples 44
4.1 Florida-The Miner's Canary? 44
4.2 Through Thick and Thin 46
4.3 Increasing Field Density-A National Study 48
4.4 A Contractor Seeks Solutions 49
Chapter 5 : Conclusions and Further Research 51
5.1 Conclusions 51
5.2 Gaps in the Knowledge and Future Research Needs 54
References 55
Abbreviations 58
Appendix A State Survey Questionnaire 60
Appendix B Industry Survey Questionnaire 67
Appendix C Tabulated State Survey Responses 72
Appendix D Tabulated Industry Survey Responses 103