Experimental study on shear property and rheological characteristic of superfine cement grouts with nano-SiO2 addition

Abstract Grouting has been widely used in geotechnical engineering, such as deep mines and tunnels, to reinforce the rock joints or cracks. In this study, the effects of particle sizes of cement and nano-SiO2 on shear strength parameters, microstructure characteristics and rheological properties were evaluated. Results showed that with the addition of superfine cement and nano-SiO2, the early-age shear strength parameters (cohesion and internal friction angle) and microstructure characteristic of specimens were significantly improved. The large viscosity of grouts caused by the fast hydration reaction with superfine cement and nano-SiO2 addition can be significantly optimized by adding superplasticizer (SP). The optimal SP dose levels of 1.5% and 0.75% were recommended for superfine cement grouts with and without nano-SiO2 addition, respectively. And the direct shear test on grout-infilled sandstone specimens proved the grouting effectiveness. The finer cement exhibited higher viscosity, while the shear strength parameters of two types of superfine cements varied little. Suitable superfine cement should be selected in grouting engineering with the consideration of crack aperture, groutability and cost-savings.