Modified expanded polystyrene particles for alkali-activated lightweight concrete enhancement: An experimental and simulation study

Expanded polystyrene is always regarded as a potential lightweight aggregate to be added to concrete to enhance the foam concrete thermal insulation performance. In addition, the usage of expanded polystyrene particles in concrete also contributes to the recycling of expanded polystyrene, which avoids environmental pollution handled improperly. However, the weak bonding performance between expanded polystyrene particles and lightweight aggregate concrete prevents the material from being widely applied. In this paper, molecular models of expanded polystyrene, expanded polystyrene modified by hydroxy, expanded polystyrene modified by carboxyl, and expanded polystyrene modified by amino were established to be composited with Natrium-Aluminate-Silicate-Hydrate, which is the main ingredient of alkali-activated material. The molecular dynamics simulation helps to optimize the expanded polystyrene modification method by analyzing the bonding property between expanded polystyrene and Natrium-Aluminate-Silicate-Hydrate through Potential Mean Force, tensile strength, and centroid position. The simulation results show that expanded polystyrene modified by carboxyl has the best bonding performance with the alkali-activated substrate. Different modified expanded polystyrene particles were composited with fly ash and slag-based alkali-activated slurry to prepare expanded polystyrene-lightweight aggregate concrete. The compressive strength of the developed carboxyl-expanded polystyrene-lightweight aggregate concrete reached 8.17 MPa with a density of 600 kg/m³. However, carboxyl modification negatively influences the material's thermal insulation performance, with a 3.5 % decrease. The simulation and experiment results lay a foundation for the wide application of modified expanded polystyrene-lightweight aggregate concrete. © 2025 Elsevier Ltd