Strengthening mechanism of polyvinyl alcohol fibers on mechanical properties of geopolymer concrete subjected to a wet-hot-salt environment

Abstract

Concrete materials are subjected to a complex coupled environment of temperature, humidity, and salt ions when in a coastal area during the summer. Geopolymer concrete (GPC), as one of the best alternatives to ordinary silicate concrete, was explored in this study to investigate its mechanical damage under wet-hot-salt environment, and to understand the strengthening mechanism of its mechanical properties by polyvinyl alcohol fibers (PF), which are crucial for the application of GPC in coastal engineering. To achieve this, a series of experiments were conducted to investigate the effect of wet-hot-salt coupled environment and PF content on the mechanical properties of fiber-reinforced geopolymer concrete containing nano-SiO2 (PF-GPC). In the experimental design, a coupled environment of 45 °C temperature, 100% humidity, and 5% NaCl solution content was firstly established for simulation acceleration test by an environmental simulation test chamber. Then different PF volume contents (from 0% to 0.8%) were considered for the cube compressive strength test, split tensile test, elastic modulus test and impact test. The results indicated that the wet-hot-salt environment significantly weakened the mechanical properties of GPC specimens, while the addition of appropriate content of PF effectively mitigated the degradation caused by the wet-hot-salt environment. The compressive strength, splitting tensile strength and elastic modulus of PF-GPC reached their maximum value at a PF content of 0.6%. Particularly, the addition of PF significantly improved the impact resistance of PF-GPC in wet-hot-salt coupled environment, with the highest impact resistance indices observed at a PF content of 0.4%. Moreover, the correlation between the elastic modulus and compressive strength of PF-GPC in wet-hot-salt environment was established by using the power function equation. And based on the applicability of the two-parameter Weibull distribution in the impact life model, an impact damage evolution equation of PF-GPC was established and validated under the wet-hot-salt conditions, which can provide valuable guidance for the design of GPC structures under different damage probabilities. The findings of this study indicated that PF-GPC can be applied in the wet-hot-salt environment, which is important for the low-carbon sustainable development of building materials.