Development of High-Performance Microfine Cementitious Grout with High Amount of Fly Ash, Silica Fume, and Slag

To develop high-performance microfine cementitious grout (HPMCG), the matrix [microfine Portland cement clinker (MPCC) + flue gas desulfurizing gypsum (MFGDG) + calcium carbonate (MCC)], microfine fly ash (MFA), silica fume (SF), and blast-furnace slag (MBFS) were selected. The viscoelasticity, fresh-state properties, mechanical performance, antipermeability, hydration mineral, and microstructure were investigated systematically. The 0%–3.0% naphthalene-based superplasticizer (N) and 1.0%–2.6% composite activator (CA) were applied, and the ratio of the water to binder (w/b) was selected as 0.8–3.0 by weight. The optimum component of HPMCG was acquired as the amount of MFA was 40% relative to that of the matrix, and the additional contents of SF and MBFS were 10% and 30%. The amounts of N and CA were suggested as 1.5%–2.0% and 2.4%, respectively. After optimization, the maximal flexural strength (FS) and unconfined compressive strength (UCS) of the HPMCG (91-day) can achieve 7.29 and 31.65 MPa; nearly all of the calcium hydroxide reacted, and more gels were generated. More generated gels interconnected with each other to form dense network structures, there were few microvoids and pores, and the entirety of the microstructure was enhanced obviously. The optimized HPMCG surpassed the expectation. The optimized HPMCG has superiorities, such as excellent viscoelasticity, good fluidity, high stability or stone rate, high mechanical strength, good antipermeability, an advantageous mineral component, and a microstructure. In civil engineering, they can satisfy high standard demands of construction and repair grouting practices.