Development of a new type sprayed high ductility concrete (SHDC) and uniaxial compression test of rock-SHDC combined body

Abstract

The application prospect of sprayed high ductility concrete (SHDC) as a tunnel and coal mine roadway supporting material is extensive. In this paper, modified desulfurization gypsum, manufactured sand, PVA-PP hybrid fiber, expansion agent, and shrinkage reducer were used as the primary raw materials to solve the environmental and cost problems caused by traditional SHDC, and an orthogonal experiment with four factors and three-level designs was conducted. The SHDC mix proportion in the orthogonal experiment was optimized on the basis of entropy weight method to optimize the grey correlation analysis. Then, the specimens were prepared by spraying to verify their performance. Finally, a low-cost, high-performance, and green SHDC was designed. The rebound rate of the vault was 17%, and the full face was 11%. The 28d compressive strength was 32.18 MPa, the ultimate tensile strain was 1.19%, and the autogenous shrinkage was 518.79με. In addition, the microstructure of SHDC and the synergistic mechanism of hybrid fibers were analyzed by optical microscopy, SEM, XRD, and TGA. On the basis of the engineering background of sprayed concrete, the rock-SHDC combined body was processed and manufactured, and uniaxial compression test was carried out. The DIC technology and surface-bonded strain gauge were used to explore the deformation and crack propagation characteristics of the composite, the energy evolution, and the impact tendency. When multiple cracks in the rock mass propagated to SHDC, convergence occurred, and 2–3 cracks converged into 1 crack. The rock monomer showed weak impact tendency, whereas the combined body and SHDC monomer showed non-impact tendency. So, SHDC can effectively limit rock deformation and maintain good integrity.