This study designs and uses water-borne epoxy resin (WBER) and curing agent (CA) to modify traditional cement-based grouting for tunnels. The purpose of this paper is to analyze the rheological and mechanical properties of composite grouting with different ratios of WBER and CA and analyze the modification mechanism by means of chemical characterization to explore the feasibility of WBER as a high-performance modifier for tunnel construction. The composite grouting is prepared by mixing cement paste with polymer emulsion. A series of experiments was carried out to investigate the effects of WBER and CA, including the slump test, viscosity, rheological curve, setting time, bleeding rate, grain size distribution, zeta potential, compressive and splitting tensile strength, X-ray diffraction(XRD), Fourier-transform infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM), on the composite grout. The results show that WBER improves grout fluidity, which decreases in combination with CA, while also reducing the average particle size of the composite grout for a more rational size distribution. Optimal uniaxial (38.9%) and splitting tensile strength (48.7%) of the grout are achieved with a WBER to CA mass ratio of 2:1. WBER accelerates cement hydration, with the modification centered on the reaction between free Ca²⁺ and polymer-OH, significantly enhancing the strength, fluidity, and stability of the polymer-modified composite grout compared to traditional cement-based grouting.

This study proposes a method to convert non-structural calcium-rich construction and demoli­tion waste fines into adsorbents of heavy metal ions by mixing waste fines with diammonium hydrogen phos­phate solution to produce hydroxyapatite, which has high surface areas and excellent ion-exchange capacity with heavy metal ions. As a result, environmental polluting waste is converted into environmentally cleaning material. Waste putty powders was chosen as the representative waste to investigate the detailed formation process of hydroxyapatite and the key reaction parameters of the reaction. Results showed that hydroxyapatite can be pro­duced on waste putty particles. Higher ageing temperatures or longer ageing duration are beneficial to the yield and crystallinity of the produced hydroxyapatite. Adsorption testing confirmed that Ni²⁺ can replace Ca²⁺ in the hydroxyapatite lattice, leading to the formation of a new crystal, arupite (Ni₃(PO₄)₂•8H₂O), and contributing to a modest adsorption capacity for Ni²⁺ (15 mg/g) for the hydroxyapatite-containing waste putty.

The rehabilitation of underground infrastructure requires cement grouts that combine high injectability into micro-cracks with superior mechanical strength and durability. Conventional grouts, however, are limited by excessive yield stress and the formation of weak crystalline phases. This study investigated sodium polyacrylate (PAAS) as a multi-functional modifier to address these limitations. Through a multi-scale approach combining rheological measurements, spectroscopic analysis (FTIR, LF-NMR), diffraction (XRD), and electron microscopy (SEM), we elucidated the synergistic modification mechanisms of PAAS. The results demonstrated that PAAS operated via two pathways: (i) chemically, its carboxyl groups chelated Ca²⁺ ions, suppressing Ca(OH)₂ crystallization and refining C-S-H gel; (ii) physically, it provided electrostatic and steric dispersion, dismantling flocculated networks to reduce yield stress by 80.3% and enhance fluidity by 30.7%. This drastically improved injectability was complemented by micro-structural optimization, where PAAS eliminated percolation pores (>1 μm) and promoted a homogeneous, dense matrix. Consequently, the mechanical properties were significantly enhanced, with a 0.04% PAAS dosage maximizing compressive strength (15.56 MPa, +26.2%) and a 0.06% dosage elevating flexural strength (5.74 MPa, +29.3%). This work establishes that low-dosage PAAS modification enables a unique combination of high fluidity, strength, and durability by leveraging synergistic chemical and physical mechanisms, providing a tailored, cost-effective solution for advanced grouting applications.

Cement-based grouting materials with a high water-to-cement ratio are susceptible to connected pore development, chloride ingress, and mechanical degradation in chloride-bearing groundwater and marine environments. To improve resistance to NaCl attack, this study compared an unmodified cement-based grouting material (NC) with a polyacrylate-emulsion-modified material (PA). Mechanical properties, surface wettability, pore structure, phase assemblage, thermal behavior, functional groups, and microstructure were investigated under different NaCl concentrations (0%, 5%, 10%, and 15%) and immersion durations (28 and 90 d). This study systematically evaluates the coupled evolution of mechanical strength retention, surface wettability, pore structure, chloride-bearing phases, and microstructure in a bulk PA-emulsion-modified high-water-to-cement-ratio grouting material under graded NaCl exposure. The results showed pronounced concentration- and time-dependent effects. Low NaCl concentrations were associated with continued hydration and reaction-product filling, whereas higher concentrations and prolonged exposure led to pore coarsening and strength loss. PA modification improved the mechanical stability of the material in NaCl environments. After 90 d of immersion in 15% NaCl, the compressive and flexural strengths of the PA group were 23.60% and 22.53% higher than those of the NC group, respectively, while the corresponding strength-retention ratios were higher by 9.06 and 10.40 percentage points. Contact-angle and MIP results showed that PA reduced surface wettability and mercury-accessible porosity. After 15% NaCl exposure, the contact angle of the PA group remained 72.5°, compared with 40.1° for the NC group, while the porosity decreased from 38.11% in the NC group to 30.98% in the PA group. XRD, TG-DTG, and FTIR analyses indicated the formation and evolution of Friedel’s salt or other chloride-bearing AFm phases after NaCl exposure. Combined with SEM observations, the results indicate that PA mitigates NaCl-induced deterioration through reduced surface wettability, refined pore structure, regulated chloride-bearing product distribution, and improved matrix integrity. Overall, the findings establish a coupled surface–pore–phase–microstructure framework for understanding the enhanced NaCl resistance of PA-modified cement-based grouting materials.