Enhancing the mechanical properties of MgO-based formulations

• Main Author: Tan, Herh Kai
• Other Authors: Cise Unluer
• Format: Final Year Project
• Language: English
• Published: 2018
• Subjects: DRNTU::Engineering::Civil engineering::Construction technology
• Online Access: http://hdl.handle.net/10356/75099
• Institution: Nanyang Technological University

Reactive magnesia cement (RMC) has seen an increase in studies in recent years to gauge and increase its feasibility to be the next concrete binding material. In this project, the self-healing properties of RMC-based composites have been explored. The microbial induced healing method used in Portland cement was modified and attempted on crack healing in RMC-based composites. This project showed that microbial induced healing is feasible and capable of completely sealing cracks that were up to 15 times wider than the maximum crack recoverable by water-air cycles. Besides sealing of crack surface, microbial healing has also been shown to produce a significantly higher amount of healing products throughout the depth of the cracks, which translate to better quality of crack healing. It is evident that hydrated magnesium carbonates are the main healing products formed, and different types of hydrated magnesium carbonates form in cracks of different width and curing conditions. The morphology of these hydrated magnesium carbonates depends on the pH, crack width and urease activity of bacteria. Lower pH, larger crack width and high urease activity curing solution will tend to favor production of needle-shaped nesquehonite crystals. Higher pH, smaller crack width and low urease activity curing solution will favor production of rosette-shaped hydromagnesite/dygingite crystals.