Performance Evaluation of Cement-Stabilized RAP–Aggregate Mixtures for Sustainable Pavement Base Applications

Abstract

The use of reclaimed asphalt pavement (RAP) in base course layers provides significant environmental and economic benefits; however, increasing RAP content may lead to a reduction in strength and load-bearing capacity. This study investigates the effectiveness of cement stabilization in improving the engineering performance of a RAP–aggregate mixture used in base course applications. Based on a previous experimental evaluation of RAP–aggregate mixtures, the mixture containing 30% RAP was selected for the present study due to its reduced strength performance, with an untreated California Bearing Ratio (CBR) value of 58.3%. To enhance its performance, the selected mixture was stabilized with cement contents of 4%, 5%, and 6%. The results demonstrated a significant improvement in strength with increasing cement content. The CBR increased from 58.3% for the untreated mixture to 84.6%, 94.33%, and 101.9% at cement contents of 4%, 5%, and 6%, respectively. The Modified Proctor test results showed that the maximum dry density (MDD) increased from 2.10 g/cm³ for the untreated mixture to 2.13, 2.15, and 2.17 g/cm³ at 4%, 5%, and 6% cement, respectively, while the optimum moisture content (OMC) increased from 3.94% to 4.24%, 4.60%, and 5.12%. Furthermore, the 7-day Unconfined Compressive Strength (UCS) increased progressively with cement content, reaching 386.4, 445.3, and 491.7 psi  at 4%, 5%, and 6% cement, respectively. The findings demonstrate that cement stabilization is an effective technique for improving the engineering performance of RAP–aggregate mixtures. Although the improvement in dry density was relatively small, substantial increases in both CBR and UCS were achieved with increasing cement content, indicating significant enhancement in load-bearing capacity and compressive strength. The results support the use of cement stabilization as a practical approach for improving RAP-containing materials for pavement base course applications while contributing to more sustainable and cost-effective pavement construction.