Coarse recycled aggregate concrete pavements - Design, instrumentation, and performance

Although there is a critical shortage of virgin aggregate, the availability of demolished concrete for use as recycled concrete aggregate (RCA) is increasing. Using the waste concrete as RCA conserves virgin aggregate, reduces the impact on landfills, decreases energy consumption and can provide cost savings. However, there are still many unanswered questions on the beneficial use of RCA in concrete pavements. This paper identifies several mix designs containing RCA that show encouraging results in both the laboratory and field testing. The coarse RCA used in the mix designs was selected to minimize impurities and limit the amount of interfacial transition zones. Waste curb and gutter and sidewalks were used to provide consistency in the RCA properties. Fine RCA was not used since it may contain large amounts of impurities that result in concrete strength loss. Twelve mix designs were laboratory tested using coarse RCA amounts of 0% (control), 15%, 30% and 50%, and cement contents of 315 kg, 330 kg, and 345 kg. Since all test mixes exceeded 30 MPa at 28-days, the lowest cement content mixes were selected for field testing Performance of four test sections is monitored through ongoing pavement evaluations using the Ontario Ministry of Transportation's Manual for Condition Rating of Rigid Pavements. Additionally, the pavement was instrumented with sensors to monitor pavement performance in relation to long-term environmental conditions. Preliminary laboratory testing and field results support a mix design containing quality coarse RCA of a specific size to result in concrete that exhibits similar or improved performance compared to non-RCA containing concrete.