Research On High Performance Sodium-silicate Suspension Two-shot Grouting Materials And Its Application

Sodium-silicate suspension two-shot grouting material is composed of suspension liquid (liquid A) and sodium-silicate (liquid B) and can serve the purposes of timely filling, soil stabilization, strengthening and mitigation of water ingress to underground facilities due to its characteristics of short gel-time and strong grout-retention capacity etc., which has found wide application in tunnel wall injection, curtain grouting, strengthening of soft foundation, etc.. Considering some disadvantages exiting in ordinary cement sodium-silicate grouting material such as the unstability of gel-time and products, poor underwater-erosion resistance, the thesis underwent a systematic research on the composition and performance of cement sodium-silicate grouting material and presented the design philosophy of high performance sodium-silicate suspension two-shot grouting material and meanwhile investigated its structure-formation mechanism, underpinning a theoretical foundation for its design and fabrication.Based on the short gel-time features of ordinary cement sodium-silicate and alkali-activated salic cementitious materials, an ideal structure model of high performance sodium-silicate suspension two-shot grouting material was established. An experiment was undertaken to verify the solidification value of Na⁺ and water-erosion resistance of a grouting material combined with cement and metakaolin-sodium silicate. This paper put forward a compact structure with a dominant ingredient of (Na, Ca)-Si-Al-H zeolite gel formed on later age and a minor part of C-S-H formed on early age, which composed of sodium-silicate, substances that could release Ca²⁺ spontaneously and stably or by the aid of sodium-silicate, and active salic substances. Considering steel slag's ingredients of C₃S, C₂S, f-CaO and Ca(OH)₂, liquid A was produced with steel slag combined with salic materials such fly ash, slag or metakaolin as a substitution for cement, based on which, a high performance sodium-silicate suspension two-shot grouting material was developed with characteristics of its excellent workability, strengthening capacity, durability, cost-effectivess, energy-conserving and environmental friendliness.The influence of factors such as dosage of polyacrylamide (PAM) and water-reducing admixture, dosage and modulus of sodium silicate, the ratio of different powders, water to cement ratio of liquid A on the workability and gelling properties of the grouting materials was comprehensively studied and the main technical indices and method for the formulation of mixture proportions of high performance sodium-silicate suspension two-shot grouting material. Criteria such as Na⁺ solidification value, dissolved quantity of SiO₂, TDS, EC, ratios of strength variation and mass loss of hardened paste, volume stability, impermeability were used to evaluate the durability of grouting materials and the durability of cement-based (C0), steel slag-based (C1), steel slag-fly ash-slag-based (C2) and steel slag-fly ash-metakaolin-based (C3) two shot grouting materials were also studies comparatively. Results indicated that the excellence rate decreased in the order of C3＞C2＞C1＞C0. With the assistance of XRD, SEM, IR, MIP and TG-DSC, The thesis analyzed the hydration and hardening mechanism and structure formation process of high performance sodium-silicate suspension two-shot grouting material, and clarified the mechanism of its high durability property.Based on the comprehensive analysis of the composition, structure and performance of high performance sodium-silicate suspension two-shot grouting material, and the strengthening projects of Wuhan Changjiang Tunnel, its fabrication, grouting techniques and parameters were studies, with successful applications. The grouting effect indicated that this high performance grouting materials could completely replace cement-sodium silicate two shot grouting materials in the application of grouting engineering, and holds a promising potential socially and economically. The Life Cycle Assessment system (LCA) was used to evaluate its impact on environment, which indicated that this grouting material was a recyclable, energy-conserving, eco-friendly construction material.