TRB's National Cooperative Highway Research Program (NCHRP) Synthesis 524: Aggregate Quality Requirements for Pavements Aggregate Quality Requirements for Pavements documents transportation agency requirements for the quality of aggregates for various pavement types. Constructing and maintaining pavements requires an abundant and dependable supply of quality aggregates. Aggregate comes from a wide range of materials, including quarried rock, sand, and gravel, and materials such as slag, reclaimed asphalt pavement, and recycled concrete aggregate. While all transportation agencies have specifications for aggregate quality, there is wide variation in what different agencies consider suitable aggregates for specific applications.

The report is accompanied by the following appendices:

• Appendix A: Survey Questionnaire
• Appendix B: Compilation of Survey Responses Provided by Agency Respondents
• Appendix C: Survey Respondent Information
• Appendix D: Links to Approved Aggregate Lists and Specifications Published by Agencies