In-situ tensile behavior of hybrid PE/PP fibers reinforced strain-hardening alkali-activated composites (H-SHAAC) subjected to different temperatures

Compared to traditional Strain-Hardening Cementitious Composites, Hybrid fiber-reinforced Strain-Hardening Alkali-activated Composites (H-SHAAC) offer enhanced environmental sustainability due to the incorporation of hybrid fibers and a low-carbon binder system. However, the thermo-mechanical properties of H-SHAAC under varying temperature conditions remain unclear. This study conducted in-situ tensile tests on H-SHAAC at various temperatures (0 degrees C, 30 degrees C, 70 degrees C, 100 degrees C, and 150 degrees C). The influence of temperature variation on the microstructure and mechanical properties of the reinforcing fibers, matrix, and H-SHAAC were studied. The degradation mechanism of H-SHAAC's mechanical properties under sub-elevated temperature was revealed. The results show that between 0 degrees C and 100 degrees C, the tensile strength of H-SHAAC decreases as the temperature rises, while its tensile strain capacity increases correspondingly. When the PP fiber replacement ratio in H-SHAAC reaches 25 %, it exhibits optimal tensile strain capacity (5.94 %-9.50 %), with an improvement of 1.4 %-41.4 % over the control group with a 0 % replacement ratio. However, this enhancement diminishes as the temperature increases. At 150 degrees C, the fibers nearly melt, leading to a sharp decline in both the tensile strength and deformability of H-SHAAC. By defining the initiation of equivalent cracks as a process of an increasing number of serially connected "springs" and increasing plastic deformation, a novel semi-empirical tensile constitutive model was established to accurately describe the tensile behavior of H-SHAAC at different temperatures. The findings of this study are of great significance for the characterization of the mechanical properties of H-SHAAC and similar materials in sub-elevated temperature applications.