Improved mechanical and macro-microscopic characteristics of shotcrete by incorporating hybrid alkali-resistant glass fibers

Fiber reinforced shotcrete (FRS) is an essential method for engineering support such as tunnels, slopes, and foundation pits. This study focuses on addressing the limitations of traditional fiber-reinforced shotcrete (FRS) by introducing innovative alkali-resistant glass fiber (AR-GF) series products, namely Anti-Crak & REG; HP (HP) and AntiCrak & REG; HD (HD) mixed FRS. The aim is to overcome issues such as rusting, corrosion, high labor, and low surface aesthetics. The mechanical and microscopic properties of alkali-resistant glass fiber reinforced shotcrete (ARGFRS) were investigated under different conditions of admixture and mixing patterns using uniaxial compression, split tensile, and scanning electron microscopy (SEM) tests. The results show that the mixing of AR-GF series products HD and HP greatly enhanced the mechanical properties of shotcrete and improved the microstructure of shotcrete. The split tensile strength was increased by 23% with the 6% content compared to 3% with HP fiber alone. AR-GFRS in HP and HD hybrid mode has better compressive and splitting tensile strength compared with the same total content of AR-GF with HP fibers alone. The optimal amount of HP was 3% of the cement mass for single mixing of HP, and the optimal mixing pattern of HP and HD was the mixing of HP (length 24 mm) and HD (length 18 mm and 6 mm). The excellent integrity of the rupture surface can be observed from a microscopic point of view, and the AR-GF was predominantly extracted. The HP damage morphology on the rupture surface was classified into fiber integrity, breakage, disorganization, and dispersion. A hybrid AR-GFRS model was established to reveal the hybrid AR-GF shotcrete reinforcement mechanism. The research results provide new ideas for the development of mixed fiber shotcrete, and lay the foundation for the design and construction of mixed alkali-resistant glass fiber shotcrete support.