Macro and micromechanical properties of polypropylene-fibre-reinforced rubber-based flexible energy-consuming concrete

Traditional concrete can suffer brittle fracture and performance limitations in transportation infrastructure. To over come these issues, a new flexible concrete incorporating rubber particles (RPs), polypropylene fibres (PPFs), bentonite and polymer emulsion was evaluated. An orthogonal test method was used to optimise the mix design. The influence mechanism of the different modifying materials and their content on concrete performance were explored. The key factors and their primary and secondary effects on improving compressive, tensile peak strain and flexural properties were clarified through range and variance analysis. Optimal flexural deformation performance of the new flexible concrete was found for the mix with 12% RPs (to replace fine aggregate), a PPF content of 6 kg/m³, bentonite content (as cement replacement) of 15% and polymer/cement ratio of 6%. Scanning electron microscopy revealed the deformation mechanism of RPs as energy absorbers, the effective containment of microcrack propagation by PPFs and a significant improvement in the structure of the interfacial transition zone due to the addition of bentonite and polymer emulsion, providing a new perspective for understanding and optimising the relationship between the microstructure and macro performance of flexible concrete.