Flexural Performance of Ambient-Cured Metakaolin-Stabilized Compressed Earth Brick Walls With Cement-Soil Mortar Joints

Abstract

This study investigates the flexural performance of metakaolin-stabilized compressed earth brick (CEB) walls with cement-soil mortar joints, focusing on their potential as sustainable materials in regions prone to lateral loads. While metakaolin-stabilized CEBs offer sufficient compressive strength for infill applications, the flexural strength of the walls is critical for resisting lateral forces. The bond between the CEBs and the mortar plays a key role in this strength. The research aimed to optimize this bond by determining the appropriate cement-soil mortar mix and metakaolin (MK) content for stabilization. Stabilization levels were represented as CEB_MKX, with metakaolin replacement percentages (X) ranging from 0% to 19%, in increments of 2%. Five CEB samples for each metakaolin content were tested for physical, mechanical, and thermal properties according to WD-ARS 1333 Edition, 2018. The optimum metakaolin content was found to be 11%, with the best cement-soil mortar mix at a ratio of 1:0.75:5.25, based on 28-day compressive strength tests in accordance with BS EN 998–2. Walls made with metakaolin-stabilized CEBs (Characteristic flexural strength, $f_{\mathrm{xk}}$ = 0.43 ± 0.02 MPa) showed a 79.17% improvement in flexural strength (under four-point loading of five samples) compared to unstabilized bricks walls ($f_{\mathrm{xk}}$ = 0.24 ± 0.01 MPa), meeting and exceeding the standards set by British 5628, 2005 for lateral load resistance. Strain gauges and Linear Displacement Transducers were used to measure strain and deflection at the mid-height of the walls during testing. This research supports the development of design guidelines for eco-friendly stabilized earth bricks, promoting sustainable building solutions.