Development of effective microfine cement-based grouts (EMCG) for porous and fissured strata

Abstract To develop effective microfine cement-based grout (EMCG) with high performance and good grouting effectiveness in geotechnical and structural engineering, the microfine Portland cement clinker and industrial wastes (microfine flue gas desulfurization gypsum (MFGDG), fly ash (MFA), steel slag (MSS) and blast furnace slag (MBFS)) were designed. In comparison, the CEM II/B-M MC and OPC were selected. The viscous behavior, flowability, spreading ability, stability of slurry, setting time, mechanical strength, linear stability, hydration mineral, microstructure, groutability and grouting effectiveness were evaluated systematically. The 0–1.5% polycarboxylate-based superplasticizer (PCE) and 2.8% alkali activator (AA) were applied to optimize workability and mechanical performance. The initial water-binder ratio (W/B) of 0.8–2.5 was applied, the amounts of MFA, MSS and MBFS by mass were 0–50%, 10–18% and 10–25%, respectively. The optimal composition of EMCG was obtained when the MFA content was 40% relative to the mass of MPCC + MFGDG + MFA, and the extra amounts of MBFS and MSS were 20% and 14%. The contents of PCE and AA were recommended as 0.9–1.5% and 2.8%. The maximum 91-day FS and UCS of EMCG are 7.53 and 31.12 MPa, and its 28-day UCS of reinforced fine sand (d10 = 0.32 mm) ranges up to 13.6 MPa. The developed EMCG has advantages such as good viscous behavior, fluidity, stability or hardening rate, strength, mineral composition, microstructure, penetration ability and grouting effectiveness. It is considered very satisfactory for the anti-seepage and reinforcement applications in construction and repair engineering.