Suitability of CKD–SBA Stabilized Compressed Earth Bricks for Load-Bearing

Compressed earth brick (CEB) offers an environmental friendly replacement for conventional fired bricks, but rural East Africa has cost and soil stability constraints in the absence of stabilizers. This study investigates the use of two waste materials in CEB manufacturing: cement kiln dust (CKD) and sugarcane bagasse ash (SBA). Expansive lateritic soil, CKD from a cement factory, and SBA from a sugar refinery were used in this study. The expansive soil exhibited high plasticity (A-7-6(18)). Chemical analyses by XRF indicated that CKD ≈ 64.52% CaO and 19.73% SiO₂, whereas SBA ≈ 75.62% SiO₂ and 1.02% CaO. Structural bricks (290 × 140 × 115 mm) were produced by molding in two stages at 6 MPa by varying CKD 0-10% and SBA 0-25% CKD. Compressive strength, water absorption, density, efflorescence, and drop tests were performed after a 28 day curing period. The optimal percentage of binder was 6% CKD and 10% SBA giving the compressive strength of 5.10 MPa (almost eight times greater than the control 0.65 MPa), exceeding the BS 3921:1985 requirement of 5.0 MPa. Water absorption decreased from 9.55% to 8.10% and efflorescence remained minimal. The strength decreased with a higher percentage of SBA owing to calcium limitation instead of reactive silica. The environmental impact evaluation estimated the amount of embodied CO₂e of 3.5 kg/tonne which is much lower compared to 41.8 kg CO₂e/tonne of 6% cement stabilized blocks and 180-240 kg CO₂e/tonne of fired clay bricks.