Durability Properties of Ambient-Cured Metakaolin Stabilized Compressed Earth Blocks

This study assessed the durability of compressed earth blocks (CEBs) stabilized with 0-19% metakaolin (CEB_MKX) and cured at ambient temperature (26 ± 0.2 °C) for 28 and 180 days. Materials were characterized mineralogically, chemically, mechanically, and physically. Metakaolin was produced by calcining kaolin at 700 °C for 3h and activated with 12M NaOH. The optimum content was 11%, in accordance with the African Standard. Abrasion resistance of CEB_MK11% (2.73 cm²/g) was markedly higher than unstabilized CEBs (0.35 cm²/g). In wetting-drying cycles, CEB_MK11% exceeded the 15% mass loss limit after five cycles (17.18% after twelve), indicating moderate durability. Capillary absorption reached 3.42 g/cm² after 72 h, slightly higher than OPC-stabilized blocks (3.12 g/cm²), showing greater early-stage uptake but comparable long-term behavior. Erosion drip tests showed no visible surface erosion, though moisture penetration was higher in CEB_MK11% (21.1 mm) than OPC8% (16.3 mm), yet all values were < 90 mm, confirming adequate durability. Under water spray (0.5 bar), CEB_MK11% had an erosion rate of 38.5 mm/h (EI2), higher than OPC8% (3.9 mm/h, EI1) but clearly outperforming unstabilized CEBs (> 120 mm/h, EI5). Overall, 11% metakaolin significantly enhanced abrasion resistance and moisture durability, supporting its potential for sustainable construction. Keywords: sustainable materials, stabilized earth blocks, capillary absorption test, durability performance, wetting-drying cycles, Erosion drip test, water spray test.