A blending of construction and demolition and agricultural wastes for efficient circularity: A sustainable approach for ceramic tile coarse aggregates and rice husk ash in M20 concrete

The present study evaluates a sustainable approach of blending ceramic tile coarse aggregates (CTCA) and rice husk ash (RHA) to produce M20 concrete. In the first step, CTCA was used to replace gravel stones by weight with the percentage replacements of 0% (C00 and control), 10% (C10), 20% (C20), 25% (C25) and 30% (C30) in M20 concrete. The best CTCA replacement result was used as the control for the second step. In the second step, ordinary Portland cement (OPC) was replaced by RHA in the range of 0% (C00R=C20=control), 5% (C05R), 10% (C10R), 15% (C15R) and 20% (C20R). The workability of fresh concrete, compressive strength at 7, 14 and 28 days, bulk density and water absorption were tested for each step. When blending CTCA in concrete, 20% CTCA replacement showed the maximum compressive strength of 22.43± 0.01 MPa on the 28^th day. An increased compressive strength  of 23.30± 0.02 MPa and relatively low water absorption (3.13%) resulted when blending C20 and C05R. The bulk density of concrete increased gradually as curing age increased, while showing an inverse relationship with RHA. The study recommends the replacement of 20% natural gravel stones and 5% OPC with CTCA and RHA, respectively, in concrete.