Effect of metakaolin and boron-carbide on the properties of magnetite, basalt and quartz concrete at different elevated temperatures

Nuclear buildings are important radiation-shielding structures. They must be shielded against radiation, fire, or heat during service life. Therefore, thermal properties and behaviour under elevated temperatures are essential in designing the nuclear structure. Furthermore, heavyweight concrete is essential for fire resistance in nuclear buildings. Mineral additives improve the physical, mechanical and fire resistance properties. The paper studied the influence of metakaolin and boron carbide additives on the thermal, mechanical and microstructural properties of magnetite, basalt and quartz concrete. Visual observations, residual mechanical properties and microstructural observations using (SEM) were studied at 20, 150, 300, 500 and 800 & DEG;C. Results showed the enhancement of the compressive strength up to 300 & DEG;C upon using metakaolin and boron carbide additives. As well as metakaolin and boron carbide caused the spalling of magnetite concrete, where the compressive strength had shown a steep decline above 500 & DEG;C. Furthermore, metakaolin and boron carbide positively influenced the strength properties of basalt and quartz concrete by reducing the permeability level and hindering the decomposition level of CSH. The Scanning Electron Microscopy (SEM) images associated the role of metakaolin and boron carbide in improving cement gel structure and reducing the decomposition level of the concrete.