Environmental resistance investigation for shield inert synchronous grouting material based on slag powder, fly ash and silica fume

In this work, the shield inert synchronous grouting material were fabricated using slag powder, fly ash and silica fume as the raw materials. In view of the inevitable influence of environmental factors on shield grouting materials after construction, the environmental resistance of inert grouting materials and single liquid active synchronous grouting materials was comparatively investigated by water absorption test, impermeability test, chemical corrosion resistance test as well as frost resistance test. Water absorption test confirmed that inert grouting materials possessed hygroscopic rate of 10.12%, which is lower than 11.31% of the counterpart after 48 h immersion. The impermeability pressure of the inert grouting materials was as high as 0.93 MPa, which was also higher than the single liquid grouting materials. Chemical corrosion resistance test showed that inert grouting materials exhibibted better salt erosion resistance, acid erosion resistance and alkali erosion resistance compared with single liquid active synchronous grouting materials under the same conditions. Frost resistance confirmed that the inert grouting materials strength exhibited loss rate and mass loss rate of 1.64% and 0.33%, which were lower than 1.92% and 0.62% of the single liquid active synchronous grouting materials after 10 freeze-thaw cycles. The phase changes of grouting materials at different ages were comparatively investigated by X-ray diffraction (XRD), and the microstructure evolution of grouting materials at different ages were compared by scanning electron microscopy (SEM). It was observed that the key for enhanced environmental resistance of inert grouting materials was the formation of a large number of cementitious materials and crystalline substances in the hydration process, which effectively improved the compactness and internal strength of inert grouting materials. On this basis, the work mechanism of environmental resistance for slag powder-fly ash-silica fume-based shield inert synchronous grouting material was proposed.