Acoustic emission based experimental study on mechanical properties and damage analysis of carbon nanotube reinforced fiber shotcrete

Abstract

Fiber shotcrete support is an important method for initial support in tunneling, slope, and foundation pit projects. However, the strength of fiber shotcrete is affected by the substantial number of irregularly dispersed pores and microcracks due to the constraints of the spraying process, surrounding rock conditions, and construction environment. Therefore, to improve the mechanical properties of fiber shotcrete, this paper proposes the addition of carbon nanotubes (CNTs) to mixed alkali-resistant glass fiber-reinforced shotcrete (AR-GFRS). Mechanical experiments were used to examine the impact of CNT admixture and curing time on the strength of AR-GFRS. The acoustic emission (AE) properties and damage patterns of CNT glass fiber shotcrete (CNGC) specimens were examined using the AE monitoring technique. Scanning electron microscopy, or SEM, was used to analyze the specimens' microscopic characteristics. Research shows: (1) At 0.2 wt% CNT doping, the compressive strength and the split tensile strength of CNGC specimens were enhanced to peak values. (2) An increment in the ratio of CNT to the overall mass led to an increase and then a decrease in the values of the CNGC intensity and AE characterization parameters. (3) Combined with the RA-AF analysis, CNGC specimens showed more than 80 % of shear damage, so CNGC damage mode was more stable shear damage. (4) It was found by SEM that the incorporation of CNT promoted the production of hydration products and enhanced the homogeneity of the specimens. The results of this study add innovative ideas and references for the use of CNT-reinforced fiber shotcrete.