Effects of biocementation on some properties of cement-based materials incorporatingBacillus Speciesbacteria – a review

Influence of Lysinibacillus sphaericus on compressive strength and water sorptivity in microbial cement mortar

“…The OPC (LB) cement paste showed a significant difference (t calc = 0.00004729, p = 0.05) in normal consistency with OPC (LB) being statistically lower than the OPC (H 2 ) cement paste as shown in Table 2. This was in agreement with the findings of Mutitu and co-authors [5, 29, 30]. The soundness of both OPC (LB) and OPC (H 2 ) cement pastes exhibited no significant difference (t calc = 0.5, p = 0.05) and hence they were similar.…”

“…However, the microbial mortars OPC-H 2 O (LB), OPC-LB (H 2 O) and OPC-LB (LB) showed significant calcium carbonate precipitates. This could be attributed to the MICP deposits from the Lysinibacillus sphaericus either present in mix media or present in the cultured curing solution [5, 31, 32]. There a lot of observable differences between the SEMs including morphology of CSH which densifies from b to c to d.…”

“…The increase in compressive strength could be attributed to the materials precipitated by the Lysinibacillus sphaericus being involved in the hydration process forming calcium silicate hydrate responsible for strength development. The added Ca 2+ together with calcium acetate, in presence of the microbial cell-wall nucleation site readily combine with the precipitated CO 3 2- and crystallizes out as calcium silicate hydrate (C–S–H) [5, 16, 27, 30].

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“…Microorganisms in soils and waters play a major role on physico-mechanical properties and durability of building materials through the process generally referred to as microbial biocementation [3]. The process is affected by variation in temperatures, humidity, type of cement, type and concentration of bacteria and soil/water pH among others [4, 5]. Through microbial biocementation, calcium carbonate is deposited in cement mortar or concrete matrix.…”

“…Addition of bacterium in OPC mortar/concrete matrix is an innovative treatment which improve the transport/migration properties of OPC making these microbial treated concrete/mortars to act as intelligent systems that are different from the usually prepared OPC cement structures [13, 14]. These smart structures have self-sensing and self-healing properties towards external factors such as change in temperature, pH, humidity and concrete/mortar pore solution chemistry [5, 9, 16].…”