Potential use of waste rice husk ash for concrete paving blocks: strength, durability, and run-off properties
G. H. M. J. Subashi De Silva, M. W. S. Priyamali
Abstract
The purpose of the study was to use waste rice husk ash (RHA), residual ash generated at the rice husk fuelled clay brick kiln, for manufacturing paving blocks. Strength, durability, water quality of the paved surface run-off and microstructure of specimens were examined. Cement in paving blocks was partially replaced by five percentage of waste RHA: 0%, 5%, 10%, 15%, and 20% (by weight). At 10% waste RHA, paving block structure became denser than the conventional block, and 56-day compressive strength was improved by 18.1% and 26.5% for M15 (Grade 15) and M25 (Grade 25) blocks, respectively. Paving blocks with 10% waste RHA achieved splitting tensile strength and flexural strength greater than that of the conventional blocks. At all waste RHA levels, sulfate resistance was improved, water absorption was ranged 3–6% and British Pendulum Number was found to be higher than 45, satisfying the limits specified in standards. For the run-off, total suspended solids concentration was less than 6 mg/l, turbidity was ranged 2.15–3.57 NTU, conductivity was ranged 74.0–137.0 μs/cm and satisfied the limits in standards. This study concludes 10% of waste RHA without any pre-processing can be used as a cement replacement in paving blocks.