Performance evaluation of cement grouted bituminous mixtures incorporating recycled concrete aggregate (RCA) under Egyptian conditions

The scarcity of natural aggregates, together with the growing volumes of construction and demolition waste (CDW), has intensified sustainability concerns in pavement engineering. While cement grouted bituminous mixtures (CGBM) have been investigated in many studies, most research has relied on natural aggregates, and only limited efforts have addressed the potential of using recycled concrete aggregate (RCA), especially under Egyptian conditions. CGBM is produced by filling an open-graded asphalt skeleton—typically designed with 18–35% air voids—with a specially formulated cement grout. In this work, laboratory experiments were conducted on CGBM prepared with different RCA replacement levels as substitutes for the coarse fraction of natural aggregates. Mixture proportions were established using the Marshall method, and the grout formulations were optimized based on fluidity, compressive strength, and flexural strength. The experimental program included multiple performance tests, such as drain-down, Cantabro abrasion loss, semi-circular bending (SCB), Hamburg wheel tracking (HWTT), dynamic modulus (E*), and flow number (FN). Results revealed that mixtures containing RCA generally matched or exceeded the control (0% RCA), while offering environmental and cost benefits. HWTT demonstrated enhanced rutting resistance, SCB indicated better fracture performance, and RCA incorporation increased stiffness and reduced permanent deformation in FN tests. The influence of RCA gradation was also evident. Multivariate analysis of variance (MANOVA) confirmed the significant impact of RCA content on performance. These findings support the adoption of RCA in CGBM to conserve natural resources, lower costs, and promote sustainable pavement practices consistent with international trends.