Validation of RAP and/or RAS in Hydraulic Cement Concrete: Technical Report

The increasing maintenance and rehabilitation actions lead to considerable amounts of reclaimed asphalt pavement (RAP) left in stockpiles in the United States. The possible use of RAP in Portland cement concrete (PCC) as aggregate replacement not only would help dispose of excess RAP stockpiles, but also provide a reduction in virgin aggregate consumption in PCC, which brings significant benefits from both economic and environmental standpoints. In this project, the previous findings on the mechanical properties and durability of RAP-PCC reported in the literature were validated. The microstructures and crack propagation in the RAP-PCC system were investigated through several advanced techniques such as optical microscope, x-ray CT, and scanning electron microscope. Performance evaluation of RAP-PCC slab by using pavement performance software and the life cycle assessment models were also conducted. Finally, the guidelines and implementation plan were provided in order to facilitate the use of PCC containing RAP in the field. The major conclusions from this project are: 1) The coarse RAP with suitable gradation containing sufficient intermediate size particles can help make dense graded concrete. The dense graded RAP-PCC showed better workability and mechanical properties compared to the other gap graded RAP-PCC. 2) The major weak point of the RAP-PCC system is the asphalt. Asphalt cohesive failure (i.e., crack easily propagate through the asphalt layer around the RAP particles) is the major failure mechanism. 3) Compared with the material production for plain PCC pavement, the production of materials for constructing RAP-PCC pavements (either full-depth or two-lift) was more economical and consumed less amounts of energy. It released less amounts of air pollutants, greenhouse gases, and toxic materials. It also led to less land use and water withdrawals. 4) The idea of using RAP-PCC as the bottom lift in a two-lift PCC pavement can maximize the RAP usage without compromising the pavement performance or compromise within the permissible limits.