Effect of microbial solution on compressive strength, water absorption and sorptivity of cement mortar incorporated with metakaolin

Abstract

Recent researches in literature have established that the overall life of mortar used in plastering works can be improved by the self-healing processes. Cracking of mortar plasters is a common hurdle due to the intrinsic brittleness of the material. This will result in severe loss of durability and water tightness. There are various methods to prevent this problem, such as adding glass fibers to the mortar mix which prevents shrinkage cracks is one among them and another way to do it is with the help of microorganisms that precipitates calcium carbonate which fills the cracks. But not all kinds of bacteria will precipitate calcium carbonate. Even if it does it should survive under extreme conditions present in mortar. The species called bacillus is a kind which fulfills those conditions is used in this project. The two bacteria namely “Bacillus Subtilis” and “Bacillus Megaterium” were isolated by taking 10g rhizosphere soil and they are cultured. The objective of this project is to compare the productivity of two bacteria. Along with this, a material called metakaolin is also used in combination with bacteria and its efficiency is also checked. The use of metakaolin (kaolinite) in this project increases compressive strength, decreases the heat of hydration which in turn increases the efficiency of calcium carbonate (CaCO3) precipitation along with bacteria. Mortar cubes are cast in different combinations to observe the compressive strength by Compression Test, healing capacity of mortar through Ultrasonic Pulse Velocity (UPV) Test and the precipitated amount of calcium carbonate via X-ray Diffraction Test. Also, the durability of mortar cubes has been identified using Water Absorption Test and Sorptivity Test.

Low-Carbon Self-Healing Concrete: State-of-the-Art, Challenges and Opportunities

“…In investigating the corrosion resistance of bacterial RC beams and cylinders [36], a 90% reduction in corrosion probability is reported; this is possibly linked to the increased watertightness. The decreased water absorption rate in bacterial SHC has been relatively consistent in research compared to OPC concrete [40][41][42][43][44][45], hence lower porosity is often found in microstructural analysis [28]. In using crystalline admixtures, its nature as water-resistant and permeability-reducing [12] hints at an ability to sustain a lower water absorption rate; this has been established in various experiments with different components of the admixture [18,19,[33][34][35].…”

Improvement of tensile strength and durability of mortar through bio cementation

“…Thus, cracks formed readily, which in turn conducts to minimization in durability. Therefore, restoration of cracks is mandatory practice and also preserving very often is much necessary (Poornima et al, 2020). However, restoration of cracks is expensive and it needs high labor.…”

“…The predecessor minerals are transformed into CaCO 3 by bacteria. Self-healing mortars are utilized to treat cracks that are shown on the plaster by biologically producing limestone (Poornima et al, 2020). Thus, the biologically enhanced cement-based materials also presented better performance in crack repair and durability than regular concrete materials (Ghosh et al, 2008).…”