Advancing Concrete Bricks: Enhancing Mechanical and Durability Properties with Crumb Rubber and Metakaolin

Abstract

One practical substitute for aggregate in concrete that can be used in sustainable building methods is waste tyre rubber and metakaolin a significant advancement in sustainable building methods. This study addresses the main problem of limited knowledge on optimizing crumb rubber proportions in concrete bricks, aiming to fill the research gap regarding their impact on brick properties. Bricks were manufactured using various crumb rubber proportions (CR5%, CR10%, CR15%, and CR20%) in a 215×103×65mm mould, maintaining a consistent water-to-cement ratio of 0.6 for all mixes. Rubberized concrete bricks were evaluated at 28 days for efflorescence, water absorption, initial rate of water absorption, density, physical observation, and compressive strength, compared to control specimens. The results revealed no efflorescence in any bricks, with a 38% density reduction in the CR20% mix compared to the control. Water absorption increased linearly with higher crumb rubber content, while the initial rate of water absorption rose to 15% crumb rubber before decreasing with further increases. Compressive strength ranged from 12 to 22 MPa, 17% higher than the minimum required for conventional bricks, although the CR20% mix's strength of 4.3 MPa was 60% lower than the control mix, rendering it unsuitable for non-load-bearing elements. The optimal combination for structurally sound concrete bricks was achieved by replacing up to 15% sand with crumb rubber and adding 10% MK. This study demonstrates that incorporating these materials can enhance the sustainability and structural integrity of concrete bricks.