: The effect of expandable polystyrene (EPS) beads size and amount of recycled rubber powder and silica fume (SF) on compressive strength and water absorption of light concrete was investigated. Addition of 10% SF (wt. % of cement) increased the compressive strength of concrete by 15%. The compressive strength increased by 5 and 15% with addition of 10 and 20% (wt. % of total aggregate) recycled rubber powder to the concrete, respectively. Presence of 5 and 15% (vol. % of total aggregate) of EPS beads with diameter of 1-3 mm decreased the compressive strength by 10 and 30%, respectively. While adding the same amount of EPS beads with diameter of 3-6 mm reduced the property by 17 and 37%, respectively. Addition of 10% SF decreased the water absorption of concrete by 15%. The water absorption decreased by 6 and 8% with addition of 5 and 15% GRT to the concrete, respectively. Concrete water absorption was reduced by 8 and 25% with adding 5 and 15% of EPS beads with a diameter of 1-3 mm. Increasing the diameter of EPS beads reduced the concrete water absorption. Keywords: Expandable polystyrene beads, Recycled rubber powder, Fumed silica, Compressive strength, Water absorption, Concrete
