Evaluating the Effects of Recycled Aggregate Treatment Methods on the Mechanical Properties of Concrete

ABSTRACT: The increasing generation of construction and demolition waste and the depletion of natural aggregate resources have increased the need for sustainable alternatives in concrete production. Recycled concrete aggregate (RCA) offers a viable solution; however, its high porosity, water absorption, and adhered mortar may adversely affect concrete performance. This study evaluated the effects of recycled aggregate treatment methods on the mechanical and durability properties of concrete. Three recycled aggregate conditions were investigated: non-treated recycled aggregate (NTRA), water pre-soaked recycled aggregate (PTRA), and cement slurry-treated recycled aggregate (STRA). Concrete specimens were produced at a constant water–cement ratio of 0.50 and evaluated using slump, compressive strength, water absorption, and chemical resistance tests. Compressive strength was determined at 7, 14, and 28 days. At 28 days, NTRA, PTRA, and STRA recorded compressive strengths of 24.8, 26.1, and 29.3 MPa, respectively, with STRA achieving an 18.1% improvement over NTRA. PTRA recorded the highest slump of 60 mm, while STRA and NTRA achieved 55 and 45 mm, respectively. Water absorption decreased from 6.2% for NTRA to 5.6% for PTRA and 4.8% for STRA. Following chemical exposure, STRA recorded the highest residual compressive strength of 25.0 MPa compared with 22.5 MPa and 21.3 MPa for PTRA and NTRA, respectively. The study concludes that cement slurry treatment provides the most effective overall improvement in recycled aggregate concrete by enhancing strength and durability and reducing water absorption. Its adoption is recommended for sustainable concrete production where improved structural performance is required. Keywords: Recycled aggregate concrete; cement slurry treatment; compressive strength; water absorption; durability.