Utilization of sawdust ash as cement replacement for landcrete interlocking blocks production and mortarless construction

Abstract

This study aimed to partially replace ordinary Portland Cement (OPC) with sawdust burnt ash (SDBA) in making interlocking laterite soil blocks. Four sets of mixes were considered: 0, 10, 20, and 30 wt%. Mix proportion was 1:6 (cement + SDBA: laterite) with a 0.70 water-to-cement ratio. 192 specimens of size 185 mm × 220 mm × 120 mm were produced and cured at normal temperature and humidity under shady and sunny conditions for 7, 14, 21 and 28 days. The research targeted four tests using 48 specimens apiece at these ages: bulk density, compressive strength, traction, and water absorption. A minimum density of 2123 kg/m3 and a maximum density of 2288 kg/m3 were recorded at 28 days when 10% and 20% of SDBA respectively replaced cement. Average compressive strengths at 0, 10, 20, 30 wt% of SDBA were respectively 6.20 ± 0.213, 6.52 ± 0.268, 6.32 ± 0.231 and 5.73 ± 0.339 N/mm2 at 28 days. Also, water absorption rates increased as the contents of SDBA replacement were increased. It was also shown that 20 wt% of SDBA is the optimum replacement level for OPC to make interlocking blocks and achieve desirable engineering properties. Though strength properties of compression and traction did not significantly improve, SDBA’s pozzolanic and cementitious properties could prevent the blocks from premature failure. Conclusively, interlocking blocks failed to significantly outperform reference samples (0%) after 28 days of testing. However, 20 wt% of SDBA on day 21 produced an average compressive strength of 6.22 ± 0.042 N/mm2 satisfying minimum allowable sandcrete blocks strength of 2.75 N/mm2 for load-bearing masonry structures per Ghana Building Code.