Magnesium Oxychloride Cement-Based Heavyweight Mortars with Coarse Hematite and Barite Aggregates for Gamma Radiation Shielding: Mechanical, Thermal and Microstructural Evaluation

Magnesium oxychloride cement (MOC) is a non-hydraulic cement that is created through a chemical reaction between light-burned magnesia powder and a magnesium chloride (MgCl2) solution. This type of cement has excellent mechanical and physical qualities, such as superior workability, elevated early strength, and reduced density. It is also used in fire-resistant coatings. Compared to Portland cement, MOC has better bonding and compressive strength. This study investigated the feasibility of producing heavyweight radiation-shielding mortars using an MOC binder with coarse hematite and barite aggregates of up to 8 mm, which are significantly larger than the fine aggregate sizes traditionally used in MOC systems. The mechanical, thermal, microstructural and gamma-ray performances of the mortars were experimentally evaluated. In this study, two different groups of mortar specimens were prepared using a magnesium oxychloride cement (MOC) binder with natural crushed stone, hematite, and barite aggregates. The thermal conductivity, compressive strength, bending strength and radiation-shielding properties of the produced mortar samples were examined. To overcome the inherent water sensitivity of MOC, a phosphate modification was incorporated into the binder system. A flexural strength, compressive strength, thermal conductivity, density, and scanning electron microscopy (SEM) analysis, and gamma radiation attenuation tests were performed using 137Cs and 60Co sources at 662, 1173 and 1332 keV. The strength values of MOC samples produced with normal aggregate were higher than those with hematite and barite. The thermal conductivity values of BMOC samples and HMOC samples gave similar results. The thermal conductivity values of mortars produced with normal aggregate were very high. The radiation retention values of barite aggregated samples were higher than those of other samples. The lowest radiation-shielding value was obtained from the normal aggregated samples. The findings demonstrate that phosphate-modified MOC can successfully incorporate coarse heavyweight aggregates of up to 8 mm while maintaining satisfactory mechanical performance and providing enhanced gamma-ray shielding, offering an environmentally promising alternative to conventional Portland cement-based shielding materials.