This study investigates the influence of gypsum (CaSO₄·2H₂O) and calcium hydroxide (Ca(OH)₂) on the hydration behavior and mechanical properties of multi-component solid waste-based cementitious materials. The evolution of hydration products was examined by evaluating compressive strength variations at different dosages and employing advanced analytical techniques, including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric–differential thermogravimetric analysis (TG-DTG), and scanning electron microscopy (SEM). The findings reveal that gypsum addition facilitates the formation of ettringite (AFt), while Ca(OH)₂ enhances system alkalinity, promoting the precipitation and solidification of calcium silicate hydrate (C-S-H) gel. A balanced incorporation of gypsum and Ca(OH)₂ significantly improves the early compressive strength and stabilizes hydration products. This study provides theoretical guidance for the effective utilization of solid waste resources and the optimized design of cementitious materials.

Alkali-activated cement (AAC) is a sustainable building material with low carbon emissions, but it has a growing demand for raw materials. In this study, the potential of low-purity modified calcium bentonite (CB) as a raw material for AAC was evaluated. The thermodynamic changes and pozzolanic properties of calcined CB were determined using X-ray diffraction (XRD), thermogravimetry-differential thermal analysis (TG-DTA), zeta potential, and a strength activity index (SAI) test. The compressive strength test, scanning electron microscopy–energy dispersive spectrometer (SEM-EDS), and Fourier-transform infrared (FTIR) spectroscopy were performed to examine the compatibility between CB and AAC. It was revealed that CB is a low-purity clay with low-pozzolanic activity. Calcination enhanced its pozzolanic activity, and the optimum temperature is 750 °C. The incorporation of modified CB improved the mechanical properties of AAC, and low-temperature modified CB had better compatibility with AAC than the high-temperature modified CB. Calcination at 150 °C had little effect on the structure of CB, and the water absorption of montmorillonite increased the ion concentration, increasing the rate and degree of hydration. Furthermore, low-temperature calcination had a dissolution–precipitation effect, resulting in leaf-like CaO·SiO₂·H₂O (C-S-H) gels, whereas the high-temperature calcination of CB was very reactive, resulting in flower-like C(N)-S-H gels.

Low-heat Portland cement and ground granulated blast furnace slag are widely used for the preparation of hydraulic concrete. Nevertheless, the effect and mechanism of corrosion on low-heat Portland cement paste mixed with ground granulated blast furnace slag need to be further explored. This paper investigated the impact of ground granulated blast furnace slag on the calcium leaching of low-heat Portland cement paste by evaluating its mass loss, porosity, leaching depth, compressive strength, and Vickers hardness, and comparing it with the leaching performance of ordinary Portland cement paste. Furthermore, the phase composition and morphology of low-heat Portland cement paste containing ground granulated blast furnace slag were analyzed by X-ray diffraction, mercury intrusion porosimetry, and scanning electron microscopy. The results indicate that, after 180 days of soaking in ammonium chloride solution, the mass loss rate, growth rate of porosity, leaching depth, and compressive strength loss rate of low-heat Portland cement paste were 8.0%, 43.6%, 9.1 mm, and 27.7%, respectively, while those of ordinary Portland cement paste were 7.4%, 37.8%, 8.4 mm, and 30.1%, indicating that low-heat Portland cement paste is slightly more damaging than ordinary Portland cement. The addition of ground granulated blast furnace slag could significantly improve the leaching resistance of low-heat Portland cement. For instance, after adding 20% ground granulated blast furnace slag, the above test values were 2.4%, 28.5%, 5.6 mm, and 20.8%, respectively. The reason for this is that ground granulated blast furnace slag has the potential to reduce the porosity of low-heat Portland cement paste, and it can also undergo the secondary hydration reaction with its hydration product Ca(OH)₂ to enhance the paste structure. Considering the cost performance, the suitable dosage of low-heat Portland cement paste for satisfactory leaching resistance is about 20%.

High belite cement (HBC) concrete is increasingly applied to the hydraulic projects, where much attention should be paid to the abrasion performance. In this paper, the mass loss, abrasion rate and morphology indexes such as depth of abrasion, volume loss and fractal dimension of HBC-based concrete at different wear periods were determined through underwater method. Moreover, a new method by transforming the survey area of worn surface was put forward to simulating practical erosion conditions, based on which, the abrasion performance prediction model was built by Projection Pursuit Regression (PPR) theory. Results show that the compounding addition of 30% mineral admixtures had little contribution to the abrasion resistance of HBC concrete after being long-term cured, while reducing water-binder (w/b) ratios was still an effective way for improving that. The worn surface of concrete specimens was divided into three regions for abrade zone, transitional zone and sound zone, and the abrasion evolution was found to be related to the wear duration and space position. Furthermore, there were good correlations between mass loss rate, depth of abrasion, volume loss and fractal dimension, and the fitting formulas were also proposed with good coefficients. Eventually, the PPR model based on the data of transformed survey area was proved to be a promising approach for predicting the abrasion performance.