Impact of Limestone Powder on the Mechanical and Microstructure Properties of Magnesium Oxychloride Cement Pastes

Magnesium oxychloride cement (MOC), a type of special construction material, has drawn much research attention in solid waste utilization and environment protection thanks to its eco-friendly production process. The potential consumption of limestone powder (LSP) in MOC products would further mitigate the environmental pollution. This study investigates the feasibility of using LSP in optimized MOC pastes. By adding 10%-40% by weight LSP, the flowability, mechanical, and microstructure properties of LSP-MOC pastes (MOC pastes mixed with LSP) were experimentally evaluated. Results showed that LSP had an adverse effect on the flowability and retarded the setting process. In terms of mechanical properties, decreases in flexural and compressive strength became significant in the presence of LSP. However, it is noteworthy that expansion was mitigated via free deformation tests, which was also reflected by microstructures. By defining normalized expansion strain, the overall strength-expansion performance was analyzed, resulting in a maximum consumption of 30% by weight LSP at a slight improvement in MOC pastes.