Recycled Concrete Aggregate Coefficient of Thermal Expansion

Despite a critical shortage of virgin aggregate, the availability of demolished concrete for use as recycled concrete aggregate (RCA) is increasing. Using this 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 about the beneficial use of RCA in concrete pavements. This research studied the effect of RCA on the coefficient of thermal expansion (CTE) and its impact on pavement performance. CTE is a key property of concrete and relates to the amount of expansion and contraction caused by changes in temperature. CTE testing was conducted on 16 cores containing various amounts of coarse RCA (0%, 15%, 30%, and 50%) using a simplified methodology. Testing showed that concrete performance improved as the amount of RCA increased. This result was demonstrated by a decrease in CTE; values for the CTE ranged from 7.28 × 10^-6/°C for 0% coarse RCA to 4.10 × 10^-6/°C for 50% coarse RCA. The variability of the CTE results was also examined to assess whether the RCA content or simplified testing methodology affected the results. Performance of the RCA concrete was simulated by using the Mechanistic–Empirical Pavement Design Guide. Average, minimum, and maximum CTE values for each RCA amount were used to investigate the sensitivity of this important property on pavement roughness, cracking, and faulting. Simulated pavement performance of all the RCA sections improved as the CTE values decreased.