Effect of Aggregate Size and Void Ratio on Plant Growth in Porous Concrete-Based Hydroponic Systems

This study examines the key factors influencing the application of porous concrete in hydroponic cultivation, focusing on aggregate size and void ratio. Porous concrete specimens were produced using aggregate sizes of 19.050 mm, 12.700 mm, and 9.525 mm, with designed void ratios of 20%, 25%, and 30%. Compressive strength was evaluated at curing periods of 7, 14, and 28 days, while plant growth performance was assessed using four species: Kaiware, Wheat, Mizuna, and Green Oak. The findings revealed that plant growth varied significantly with changes in void ratio and aggregate size, with an optimal void ratio of 29.97% for efficient water absorption and drainage, thereby enhancing plant development. The aggregate size of 9.525 mm was found to be most suitable for Kaiware and Wheat due to enhanced root anchorage and moisture balance, whereas Mizuna and Green Oak grew more effectively on 19.050 mm aggregate. This indicates that optimal aggregate size for plant cultivation may vary by species. In terms of mechanical performance, the highest compressive strength was recorded for porous concrete incorporating 9.525 mm aggregates with a void ratio of 23.71%, reaching 8.2 MPa at 28 days of curing.