Development and characterization of eco- and user-friendly grout production via mechanochemical activation of slag/rice husk ash geopolymer

Abstract

In this study, mechanochemical activation was used both to increase the reactivity of a one-part geopolymer during ambient curing and as an alternative activation technique to overcome the difficulties associated with conventional two-part geopolymers. The mechanochemical grinding of raw materials of varied compositions in a solid-state resulted in the synthesis of ready-to-use geopolymeric precursors, which with just the addition of water, resulted in the development of eco- and user-friendly geopolymer grout. In addition, conventionally activated geopolymer grout and ordinary Portland cement (OPC) grout were investigated for comparative purposes. Four rice husk ash (RHA) replacement ratios were used (0%, 10%, 20%, and 30% by the total precursor weight) to investigate the feasibility of using RHA as a partial precursor in slag-based mechanochemically activated geopolymer (MSG) grout. A series of tests were examined, such as rheological behavior (flow curve response, yield stress, and plastic viscosity), fresh properties (setting time and bleeding capacity), mechanical characteristics (unconfined compressive strength, ultrasonic pulse velocity), and microstructure analysis (scanning electronic microscopy, X-ray Diffraction). The experimental results showed that the rheological characteristics and fresh properties of MSG grouts were considerably enhanced in terms of groutability when slag was replaced with 0–30% RHA. In addition, the mechanical characteristics increased with the increased partial replacement of slag with RHA up to 20% and decreased beyond that. In terms of activation mechanism, the mechanochemical activation technique reduced the rheological characteristics and fresh properties while the strength increased by 18% compared to the conventional activation method. Microstructural analysis revealed the existence of more unreactive particles in both conventionally activated geopolymer and MSG grout containing 30% RHA. The results also confirmed that MSG grouts had a shorter setting time and more stable bleeding capacity than OPC grout.