Application of RSM in optimizing the density and strength of lightweight concrete using EPS solution

This work addresses the challenge of balancing low density and adequate strength in Lightweight Concrete (LWC) by proposing a novel approach using an Expanded Polystyrene (EPS) adhesive solution instead of conventional beads. This solution acts as both a lightweight agent and an auxiliary binder, effectively overcoming issues like buoyancy, segregation, and weak interfacial bonding. Incorporating the solution after cement paste formation ensured uniform dispersion and enhanced material homogeneity. Response Surface Methodology (RSM) was used to evaluate the interactive effects of W/C (water to cement mass ratio), S/C (sand to cement mass ratio), and EPS volume fraction on compressive strength and density. The optimization yielded a maximum desirability (D=1.000). The optimal mixture (W/C =0.46, S/C = 1.76, EPS = 38.65%) predicted a compressive strength of 10.64 MPa and a density of 939.2 kg/m3. Experimental validation under rounded conditions (10.4 MPa and 935 kg/m3) confirmed the model's reliability, demonstrating a successful balance suitable for non-load-bearing applications.