Synthesis and characterization of eco-friendly alkali-activated industrial solid waste-based two-component backfilling grouts for shield tunnelling

The two-component grout consisting of liquid A (cement paste) and liquid B (accelerator) is often used for backfill grouting in shield tunnels. However, the traditional cement-sodium silicate (CS) grout not only consumes ordinary Portland cement, but also has the disadvantage of poor resistance to water corrosion. In view of this, this study explored the possibility of using industrial solid wastes as solid precursors to prepare a new eco-friendly two-component grout. Through a series of experiments, the effects of factors including the solid precursor composition of liquid A, the modulus of liquid B (sodium silicate), the volume ratio of liquid B to liquid A and the additive content on the properties of alkali-activated industrial solid waste (AAISW) based two-component grouts were investigated systematically. The gel time, flowability, bleeding ratio, mechanical strength and water corrosion resistance of AAISW grouts were tested and compared with those of the CS grout. It is found that the gel time of AAISW grouts can be adjusted in the range of tens of seconds to minutes. The flowability loss with time of liquid A of AAISW grouts is significantly less than that of liquid A of the CS grout. The AAISW grout has good stability and can achieve compressive strength comparable to or even higher than that of the CS grout. In addition, the water corrosion resistance of the AAISW grout is obviously better than that of the CS grout. The eco-friendly AAISW grout has obvious advantages over the CS grout in terms of performance and sustainability, so it has promising application prospects. (C) 2020 Elsevier Ltd. All rights reserved.