Mechanical and thermal properties of fibrous rubberized geopolymer mortar

•Effect of both crumb rubber and polypropylene fibers on properties of geopolymer mortar.•Crumb rubber enhances the ductility and toughness of geopolymer mortar.•Crumb rubber improves the thermal properties of geopolymer mortar.•Regression models accurately predict mechanical and thermal properties are introduced. Nowadays, geopolymers play an important role in developing eco-friendly construction materials to avoid the pollution that comes from the Portland cement industry. Geopolymers show enhanced mechanical properties while ductility tends to be relatively low. Moreover, the thermal properties of construction materials are important in terms of energy-saving and sustainability. On the other hand, by increasing the used rubber tires and with low recycling processes, these wastes become a serious environmental problem. So, this work is directed to develop and investigate enhanced rubberized geopolymer composites regarding ductility as well as thermal properties. To achieve these targets, reusing Crumb Rubber (CR) from used rubber tires as a partial replacement of sand by volume was investigated with (10 %, 20 %, and 30 %) replacement ratios and different CR particle sizes (0–1 mm, 1–3 mm, 4 mm, and 0–4 mm). Parallel with using CR, polypropylene fibers with different volume fractions of (0.5 %, 1.0 %, and 1.5 %) were implemented. The effect of CR content and size on the Physical, mechanical, and thermal properties have been investigated. Additionally, the effect of incorporating polypropylene fibers in rubberized geopolymer mortar has been studied. The results indicated that despite the mechanical properties of rubberized geopolymer mortars tend to be lower, the mode of failure, toughness, and performance under flexural due to the synergistic influence of rubber and fibers have been improved remarkably. Additionally, the results of the transient plane source method indicated that thermal conductivity, thermal diffusivity, and heat capacity have been significantly enhanced in terms of heat insulation. Incorporating 20 % CR with 1 % fibers increases the flexural toughness by 27.5 % more than the mix containing 1 % fiber only. Incorporating 30 % CR decreased the thermal conductivity by about 39.7 %. Furthermore, the regression analysis by developing numerous relationships was proposed. The results of the regression model revealed that the models developed were adequate in explaining the effect of the independent parameters on the responses. It will be helpfu