Prediction of Strength and Stiffness Properties of Recycled Pavement Base Materials Using Non-destructive Impact Echo Test

Abstract

Reclaimed Asphalt Pavement (RAP) and Recycled Crushed Concrete Aggregates (RCCA) are being used increasingly as an alternative to the conventional base materials in pavement construction. However, product variability and lack of strength-stiffness characteristics are limiting the use of recycled materials in pavement application. A non-destructive evaluation technique could provide a better quality control tool for the highway officials during the construction. Therefore, the objective of the current study is to develop a correlation between the non-destructive impact echo and Unconfined Compressive Strength (UCS) test for RAP and RCCA materials. Both impact echo and UCS tests were performed on specimens prepared with 100% RAP and RCCA. The RAP and RCCA were separately treated using four (0, 2, 4 and 6%) different dosages of Portland cement. Based on the experimental results, the range of P-wave velocity was found between 175 m/s to 475 m/s, the compressive strength varied between 67 kPa to 2860 kPa and tangent modulus range was 19 MPa to 280 MPa. Dynamic modulus of elasticity was also calculated from the P-wave velocity, density, and Poisson’s ratio. At 4% and 6% cement contents, dynamic modulus of elasticity was within 10% of the tangent modulus found from UCS test. At 0% and 2% cement content, higher variation was observed. Inadequate fines to fill the voids might be the reason of lower P-wave velocity at 0% and 2% cement contents. This could eventually have predicted lower values of dynamic modulus.