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%.

The hydraulic concrete in the alpine region is subjected to alternating actions of freeze–thaw (F) and abrasion (W) during operation, resulting in significant deterioration of concrete durability. In this paper, the water/binder ratio (W/B) was employed as the test variable, the working condition F group and W group were set as the control group, and the working condition F-W group was used as the test group. Fast-freezing and underwater methods are used for the alternating test. By measuring the mass loss, relative dynamic elastic modulus (RDEM), surface morphological characteristics, fractal dimension of concrete in each alternating cycle, and the evolution law of concrete performance under the alternating action of F and W was explored. The results show that compared with the control group, the alternating action will accelerate the mass loss of concrete, reduce the RDEM, and cause the deterioration of surface wear. The maximum increase in mass loss and RDEM of concrete is 1.92% and 20.11%, respectively. During this process, the fractal dimension of the concrete increases as the number of alternating cycles increases, but it still does not exceed the limit of 2.4. In addition, a relationship function between the fractal dimension and the mass loss rate, volume loss, was established. It was found that the experimental group had a good linear correlation, and the correlation was close to 95%, which was about 20% higher than that of the control group.

This study investigates the mechanical and impact resistance properties of high-performance cementitious composites (HPCCs) incorporating hybrid fibers under a low water-to-binder ratio, with a focus on the multi-scale synergistic effects of different fiber types. Aramid fibers (AFs), basalt fibers (BFs), and calcium sulfate whiskers (CSWs) contribute to reinforcement at the macro, meso, and micro levels, respectively. Experimental results reveal that hybrid fiber systems significantly outperform single-fiber composites in terms of both impact resistance and crack suppression. The optimal mix design—comprising 3% CSW, 0.067% AF, and 0.033% BF—achieved a remarkable 233.3% increase in impact energy absorption compared to the control group. This enhancement is attributed to the complementary roles of the three fibers: CSWs refine the pore structure and mitigate microcrack propagation; AFs effectively restrain the development of macrocracks due to their high tensile strength and aspect ratio; and BFs contribute to energy dissipation through crack bridging and mechanical interlocking. Statistical analysis using the two-parameter Weibull distribution accurately characterized the variability and reliability of the impact resistance data, while pore structure analysis confirmed a reduction in average pore diameter and a more favorable pore size distribution. These findings underscore the effectiveness of fiber hybridization in improving the mechanical behavior and dynamic load resistance of cement-based composites, offering valuable insights for their application in demanding engineering scenarios.

In the river environments of Xinjiang characterized by high sediment content and high flow velocities, hydraulic concrete is highly susceptible to damage from the impact and abrasion of bed load. Consequently, this imposes more stringent requirements on its mechanical properties and abrasion resistance. The incorporation of crumb rubber, a recyclable material, into concrete presents a dual benefit: it enables resource recycling while simultaneously offering a novel pathway for the development of concrete technology. This study takes rubber powder concrete as the research object. With the same water-to-binder ratio, rubber powder was incorporated at three volume fractions: 0%, 5%, and 10% of the cementitious material. The drop weight impact test and underwater steel ball method are adopted to evaluate its impact resistance and anti-scouring-abrasion performance, respectively. By testing the compressive strength, impact toughness, wear rate, anti-scouring-abrasion strength and three-dimensional morphological characteristics, the influence of rubber powder content on the mechanical properties and anti-scouring-abrasion performance of concrete is systematically analyzed. The research results show that the addition of rubber powder reduces the compressive strength of concrete, but significantly improves its impact resistance and anti-scouring-abrasion performance. Among all test groups, the concrete with 10% rubber powder content has the most significant decrease in compressive strength, with a decrease of about 37% compared with the 5% content group, while the 5% content group has a decrease of about 27% compared with the control group. However, its impact toughness at 3d, 7d and 15d is increased by about 84.7%, 88.4% and 84.4%, respectively, compared with the control group, showing the largest improvement range. At the same time, the wear rate of this group is reduced by about 42.5%, and the anti-scouring-abrasion strength is increased by about 61%. Combined with the three-dimensional morphology analysis, it can be seen that the specimens in this group exhibit the optimal anti-scouring-abrasion performance. In terms of microstructure, the porosity of rubber powder concrete increases, the generation of C-S-H gel decreases and its continuity is damaged, leading to a significant decrease in compressive strength. The reduction in the generation of delayed ettringite enhances the toughness and anti-scouring-abrasion performance. In general, the increase in rubber powder content will lead to a decrease in the compressive strength of concrete, but within a certain range, it can significantly improve its impact resistance and anti-scouring-abrasion performance. Crumb rubber effectively enhances the impact and abrasion resistance of hydraulic concrete, demonstrating strong application potential in high-flow, sediment-laden river environments.

Based on mortar composites with a low water–cement ratio, the effects of hybrid aramid fiber (AF), calcium sulfate whisker (CSW), and basalt fiber (BF) on their mechanical properties and wear resistance were studied, and the correlation between wear resistance and compressive strength are discussed. A microstructure analysis was conducted through scanning electron microscopy (SEM) and the nitrogen-adsorption method (BET). The research results show that compared with the control group, the compressive strength, flexural strength, and wear resistance of the hybrid AF, CSW, and BF mortar composites with a low water–cement ratio increased by up to 33.6%, 32%, and 40.8%, respectively; there is a certain linear trend between wear resistance and compressive strength, but the discreteness is large. The microstructure analysis shows that CSW, AF, and BF mainly dissipate energy through bonding, friction, mechanical interlocking with the mortar matrix, and their own pull out and fracture, thereby enhancing and toughening the mortar. A single doping of CSW and co-doping of CSW and AF can refine the pore structure of the mortar, making the mortar structure more compact.