Effect of a low content of waste rubber inclusion on pore structure and thermal insulation properties of hybrid slag mortars

The reuse of sustainable waste materials in cement-based mixtures is a key solution for the production of environmentally friendly construction materials. Among the various types of industrial wastes, the utilization of waste rubber (WR) has become a vital topic in the sustainable material design. This study aimed at developing an eco-friendly mortar by enhancing the use of WR as a cement additive in hybrid slag mortar mixtures. For this purpose, five different hybrid slag mixtures were prepared, with three contents (0%, 1.0%, and 2.0%) and two different particle size ranges (0-0.6 mm and 0-1.0 mm) of WR. The experimental results demonstrate that the incorporation of a low content of WR into the mixtures leads to a major pore modification effect, resulting in an increase in the number of pores with lower pore sizes. Based on the pore modification effect, a thermal insulation enhancement of approximate to 17% was measured with limited strength reductions. Besides, strong linear relationships between the strengths and the effective pore contents with R-2 of > 0.80 were detected. With the aim of promoting the sustainable design, the integration of a low content of rubber and slag seems as a good option.