Mechanical properties and mesoscopic damage characteristics of basalt fibre-reinforced seawater sea-sand slag-based geopolymer concrete

Abstract

This study aims to investigate the macroscopic mechanical properties and mesoscopic damage mechanisms of basalt fibre-reinforced seawater sea-sand slag-based geopolymer concrete (SS-SGC). At the macroscopic level, the influences of different volumes and lengths of basalt fibre (BF) on the workability, compressive strength, and splitting tensile strength of SS-SGC were analyzed. The optimum BF length was identified as 12 mm, with an optimal volume fraction of 0.6 %. This combination resulted in 9 % improvement in compressive strength and a 7 % enhancement in splitting tensile strength compared to the control group. Compared to Ordinary Portland Cement (OPC), SS-SGC exhibited a remarkable reduction of 79.6 %, 60.2 %, and 21 % in carbon emissions, energy consumption, and cost, respectively. At the microscopic level, scanning electron microscopy (SEM) was employed to analyze fibre distribution characteristics and the ITZ microstructure between the two aggregates and the matrix. The fibre bridging and aggregate synergistic mechanisms were proposed, highlighting the role of the high-density far-field ITZ of coral coarse aggregate (CCA) in altering the crack propagation trend and confining microscopic damage within the highly ductile matrix, thereby improving the mechanical properties of the concrete. At the mesoscopic level, a six-phase numerical model was established, considering different aggregates and their ITZ characteristics, to systematically analyze the mesoscopic damage evolution, as well as the macroscopic strength and stress-strain behavior of SS-SGC. The research outcomes serve as a reference for future multiscale studies on SS-SGC and its practical engineering applications.