DEVELOPING SPECIFICATIONS FOR USING RECYCLED ASPHALT PAVEMENT AS BASE, SUBBASE OR GENERAL FILL MATERIALS, PHASE II
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This Phase II work focused on 1) validating the Phase I developmental specifications for using Recycled Asphalt Pavement (RAP) as a base, subbase or general fill, 2) evaluating the strength gain of RAP within the first two months after construction, 3) evaluating RAP-Soil mixes in the laboratory, and 4) evaluating the environmental performance of RAP in the field. The Phase I Developmental Specifications were updated to allow RAP as a subbase below rigid pavements. A second field site was constructed using RAP and a Limerock control section. It included surface water and leachate water collection systems in both the RAP and Limerock. The initial strength gains were evaluated over an 8-week period and the environmental performance was analyzed over 12 months. Construction with RAP was equivalent to or better than construction with Limerock. RAP's strength-deformation behavior increased throughout the 8-week study period based on field California Bearing Ratio (CBR) data converted to Limerock Bearing Ratio (LBR), Initial Stiffness Modulus (ISM) values from the Falling Weight Deflectometer (FWD), and stiffness values from both the Clegg Impact Hammer and the Soil Stiffness Gage (SSG). LBR, Clegg and ISM data indicated that RAP experienced a 50% strength gain over 8 weeks while the SSG results indicated that the strength gain was 15%. The Clegg, FWD and SSG testing also indicated that RAP stiffness was similar to Limerock. RAP-Soil mixes were evaluated by adding varying percentages of a poorly graded sand with clay, an A-2-6 (SM-SP) soil dredged from the Turkey Creek area in Palm Bay, Florida. The 80% RAP-20% soil mix produced the most desirable engineering behavior. Preliminary creep testing indicated that both the 100% RAP and the 80/20 RAP-Soil mix may pose long term deformation concerns. The environmental evaluation indicated that RAP poses no environmental concerns when used as a highway material. The concentrations of heavy metals were well below the EPA standards. Samples were taken over a 12-month period and subjected to four different environmental testing procedures. All four yielded the same conclusions, indicating that the testing program was valid.
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