Effect of Calcite Precipitation on Properties of Fresh and Hardened Laterized Concrete

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Reduction in strength and durability is the limitation for use on laterized concrete in various engineering applications.This research focuses on the effect of calcite precipitation on the strength and durability of laterized concrete. The laterized concrete sample was prepared by fine aggregate replacement with laterite at 0 %, 10 %, 20 %, 30 %, and 40 % by weight of fine aggregate. A prescribed concrete mix proportion of 1:1.5:3 and a water-to-cement ratio of 0.5 was used to prepare the concrete. At each level of replacement, Sporosarcina Pasteurii bacteria at concentrations of 0, 1.5 x 108, 3.0 x 108, and 6.0 x 108 cells/ml were incorporated in the laterized concrete. Fresh concrete samples were tested for slump, hardened concrete cubes were tested for Compressive Strength at 7, 14, 21 and 28 days of water curing and a durability test in form water absorption was performed after 28 days. The slump results showed that the workability of the concrete reduces as the laterite content increases due to more water absorption during mixing, however, the concentration of bacteria had no discernible impact on the slump value. The results of the compressive strength test showed that the compressive strength at all bacterial cell concentrations improves with curing age and declines with increasing laterite content. However, the strength of laterized concrete prepared at a 10% level of replacement is marginally similar to the control sample. All the bacterial concrete performed better than their corresponding non-bacterial concrete with 1.5x108 cells/ml giving the optimum result. The water absorption of the samples was found to increase with an increase in laterite content and after the bacteria introduction, the concrete samples showed reduced water absorption when compared with the non-bacterial samples with 1.5 x 108 cells/ml giving the optimum improvement. Calcite crystals and denser surfaces were found by scanning electron microscopy imaging in the bacterial concrete. The bacterial laterized concrete with laterite replacement not exceeding 20% produced concretes of compressive strengths greater than 〖25N/mm〗^2and is suitable for reinforced concrete works