Experimental Study on the Structural Performance of Lightweight Precast Concrete Slabs Incorporating AAC Block Aggregate

Precast concrete slabs offer advantages in quality control, construction speed and installation efficiency; however, their self-weight increases the loads transferred to supporting structural members and complicates transportation and handling. This study investigates the preliminary development of lightweight precast concrete slabs incorporating waste Autoclaved Aerated Concrete (AAC) block aggregate as a partial replacement for natural coarse aggregate. The Phase I work comprised a review of 19 research studies, identification of the research gap, preliminary M40 concrete mix proportioning, manual design of a two-way slab, aggregate testing and an initial finite-element analysis using ANSYS. Five mixtures were proportioned with 0%, 5%, 10%, 15% and 20% AAC replacement by volume of coarse aggregate, at a preliminary water-cement ratio of 0.40. The cement content was 437.1 kg/m3 and the AAC aggregate specific gravity was measured as 0.60, with 15% water absorption. The aggregate impact value was 37%. A 700 mm ? 600 mm ? 100 mm two-way slab was designed using the procedure stated in IS 456:2000 and provided with 8 mm diameter reinforcement at 150 mm centres in both directions. Preliminary calculations indicated adequate flexural, shear and deflection checks under the adopted design assumptions. The initial ANSYS model produced deformation, strain and stress contours; however, the reported peak values are unusually high and require verification of units, material properties, loading, boundary conditions and mesh before engineering interpretation. The results presented are therefore limited to Phase I preparation and preliminary assessment. Cube and slab testing, durability assessment and experimental validation are planned for Phase II.