Study on properties of sodium bentonite modified superfine slag cement composite grouting material

• The BASCP optimal ratios from range analysis: W/C = 0.8, C/GGBS = 5:5, Bentonite = 3%, NaOH = 0.8%. • The optimal BASCP grouting material proportion reduces the bleeding rate by 17.54%. • The BASCP attained 57.85 MPa at 28 days, with an average strength gain of 29.01%. • BASCP effectively metabolized CH cubic crystals, promoting C(A)SH and NASH formation. • BASCP can mitigate shear slip occurrence and enhance material density. At present, the use of alkali-activated geopolymer gel derived from solid waste particles as a partial replacement for cement has emerged as an effective approach to developing green and environmentally friendly grouting materials. However, the interaction between geopolymers and cement can lead to negative impact mechanisms, such as localized accumulation of reaction products and inhibition of strength development. This study presents a modification investigation of alkali-activated slag cement incorporating bentonite. Research indicates that: (1) The dosage of bentonite is inversely related to the fluidity of the slurry. A dosage of ≤6% can still achieve high fluidity standards. Additionally, bentonite significantly reduces the bleeding rate of BASCP. (2) The compressive strength exhibits a trend of initially increasing and subsequently decreasing with variations in bentonite dosage. (3) A significant amount of cubic crystals was observed to precipitate on the surface of the experimental samples without the addition of bentonite, as determined by scanning electron microscopy (SEM). The primary component was identified as Ca(OH)₂ through three quantitative analysis methods: energy-dispersive spectroscopy (EDS), thermogravimetric analysis (TGA), and X-ray diffraction (XRD). (4) The damage constitutive model established based on the ringing frequency of acoustic emission signals and stress parameters indicates that the incidence rate of damage is minimized at a bentonite dosage of 3%. The research findings indicate that bentonite can significantly enhance the performance of alkali-activated slag cement grouting materials. This provides a valuable reference for further studies focused on the modification and optimization of green and environmentally friendly grouting materials.