Developing thermal insulation cement-based mortars using recycled carbon black derived from scrapped off-the-road tires

Abstract

This study appraised the feasibility of recycled carbon black (RCB) derived from scrapped off-the-road (OTR) tires, denoted as RCB-OTR, as aggregates to develop thermal insulation mortars. Sand in Ordinary Portland cement (OPC)-based mortars was replaced by RCB-OTR in volumetric proportions of 0, 30, 60, and 100%. The results revealed that the developed thermal insulation mortars had oven-dry densities between 1058 ± 1 and 2045 ± 5 kg/m3 and 28-day UCS between 8.6 ± 0.74 and 37.3 ± 0.76 MPa. Mortars at RCB-OTR replacement ratios below 30% can be employed as load-bearing units. Replacing all sand with RCB-OTR resulted in a considerable decrease in thermal conductivity from 1.800 ± 0.071 to 0.272 ± 0.021 W/mK, the volumetric heat capacity from 1.438 ± 0.063 to 1.044 ± 0.079 MJ/m3K, and thermal diffusivity from 1.255 ± 0.089 to 0.263 ± 0.034 mm2/s. Overall, mortars mixed with RCB-OTR exhibited good thermal insulation performance and satisfactory mechanical properties, demonstrating that RCB-OTR is a promising lightweight aggregate for thermal insulation building materials. This is the first study to incorporate RCB-OTR into the cement-based materials and evaluate the thermal properties. It contributes to the development of eco-friendly thermal insulation building materials using RCB-OTR and delivers an innovative solution for mining industry to dispose of waste OTR tires.