Effect of Mineral Wool Impregnated with Carbon Nanotubes on Properties of Cement at High Temperatures

The most significant change in the structure of Portland cement at temperatures above 110°C is a decrease in strength. There are several additives that enhance the cement’s resistance to structural failure at high temperatures, such as metallurgical slags, quartz, and carbon nanomaterials. One of the emerging approaches is the utilization of mineral wool impregnated with carbon nanotubes. The relatively small particle size of mineral wool enables the filling of capillary micropores with carbon nanotubes, thereby increasing the overall structural integrity of the cement. This study investigates the impact of adding mineral wool saturated with carbon nanotubes (25%) to Saudi G-class cement. Six cement paste specimens were prepared with mineral wool contents ranging from 0 to 25%. The chemical composition of the cement was analyzed using X-ray fluorescence, the physical composition was evaluated via X-ray diffraction, testing of the cement slurry samples was conducted in accordance with ISO 10426-2:2003, tensile strength testing of the specimens was performed using the Brazilian method as per ASTM D 3967-08, and permeability testing was carried out according to ISO 10426-2:2003. The properties were assessed under elevated thermal conditions of 300°C. After curing for 7 and 28 days, these cement stones underwent testing over a temperature range from 25 to 300°C. The research findings indicate that the optimal content is 10-15% mineral wool containing 25% carbon nanotubes (resulting in a carbon nanotube concentration in the cement matrix of 2.5-3.75%). Results obtained after 28 days show high compressive strength values exceeding 50 MPa, which is 5-23% higher than that of the additive-free cement at 25°C and 5.7-6.2 times higher at 300°C. Additionally, tensile strength values are higher, being 1.4 times greater than the additive-free cement at 25°C and 3.7-3.9 times higher at 300°C. Moreover, low permeability values of the cementitious material were achieved, with permeability ranging from 2 to 3 mD*10-3 for mineral wool concentrations of 5 to 15%, representing a 2-2.5 times reduction compared to critical values, thereby ensuring good inter-column insulation.