RECYCLED ASPHALT PAVEMENT AND CRUSHED CONCRETE BACKFILL: RESULTS FROM INITIAL DURABILITY AND GEOTECHNICAL TESTS

This report describes research results from the second year of a three-year study focused on the use of recycled asphalt pavement (RAP) and crushed concrete (CC) as backfill for mechanically stabilized earth (MSE) walls. The objectives of the research project are reviewed. The compaction characteristics of RAP and CC are presented, and the effect of compaction on particle breakdown is discussed. Tests to evaluate the accuracy of nuclear gauges, when used to measure the compacted density and water content of RAP and CC in the field, are also discussed. Results indicate that the nuclear gauge overpredicts the as-compacted moist density and water content of RAP and CC. Triaxial strength testing of RAP and CC are presented, and indicate that these materials exhibit adequate strength for MSE wall applications. Results are presented from expansion tests performed on various CC specimens to evaluate the potential for excessive heave or expansion after compaction. Expansion appears only to be a problem when the CC contains significant sulfates, but the sulfate levels necessary to cause problems are not expected to occur in the field. Preliminary results from corrosion tests indicate that RAP and CC do not adversely affect the corrosion rate of metallic strip reinforcement at early exposure periods.