Xianliang Zhou

This study investigated the effects of NaOH molarity (6-14 M) and ground granulated blast furnace slag (GBFS) content (0-45%) on the properties of lithium slag (LS)-based cold-bonded lightweight aggregates. Bulk density, water absorption, porosity, and cylinder compressive strength were evaluated, and microstructural characterization was conducted using SEM, XRD, FTIR, MIP, and TG/DTG. Results showed that increasing NaOH molarity and GBFS content reduced water absorption (from 15.87 to 5.88%) and porosity (from 34.79 to 13.39%), while enhancing bulk density (731-1074 kg/m³) and compressive strength. At 30% GBFS, the 28-day strength increased by 224.48%, from 3.35 MPa (M6-30) to 10.87 MPa (M14-30). At 12 M NaOH, raising GBFS content from 0 to 45% increased strength by 435.62%, from 2.33 MPa to 12.48 MPa. LS without GBFS achieved 2.33 MPa, indicating inherent pozzolanic activity. Microstructural analysis revealed that performance improvement was due to enhanced geopolymerization and reduced harmful pores (> 200 nm). The M8-30 mix (915.68 kg/m³, 5.98 MPa) showed potential for meeting high-strength lightweight aggregate criteria with mix optimization. These findings demonstrate the feasibility of valorizing LS into high-performance lightweight aggregates, contributing to waste utilization and low-carbon construction.

The mitigation of early-age shrinkage and thermal cracking remains a pressing challenge in mass concrete structures. This study introduces a novel temperature-control admixture (TCA), formulated with gel-forming inorganic compounds, designed to suppress internal temperature rise while improving the mechanical stability of fly ash concrete. Four concrete mixes with TCA dosages of 0, 0.05, 0.10, and 0.15% were experimentally evaluated under controlled environmental conditions. Results show that the optimal dosage of 0.10% achieved a 27.3% reduction in shrinkage and a 12.2% increase in compressive strength at 28 days compared to the control. Furthermore, existing shrinkage models (Eurocode 2, fib Model Code 2010, AS 3600, Bazant B4) consistently overestimated shrinkage by up to 294% due to their inability to capture TCA-induced modifications in hydration and moisture transport. To address this, a modified prediction model incorporating admixture and fly ash–dependent correction factors was proposed, reducing the mean prediction error to just 10% and achieving a coefficient of variation as low as 0.08. This work provides a semi-empirical modeling approach that captures the influence of microencapsulated TCAs on concrete shrinkage and offers useful insights for the design and optimization of advanced concrete systems.

The cold bonding technology for producing lightweight aggregates has received significant international attention in the fields of waste treatment and the production of green building materials. In this study, sustainable lightweight aggregate concrete (LAC) is prepared by partially replacing natural coarse aggregate with cold-bonded sewage sludge ash lightweight aggregate. The properties and microscopic characteristics of concrete were studied. The results show that the density and compressive strength of LAC decreased to 1645 kg/m³ and 12.83 MPa when the replacement rate of lightweight aggregates from 0 to 100%, indicating that the LAC can be used for non-structural LAC. Structural LAC can also be designed when 75% lightweight aggregates and 25% natural coarse aggregate are used simultaneously. In addition, the results of Scanning Electron Microscope and Nuclear Magnetic Resonance show that high lightweight aggregate content is accompanied by higher porosity and pore size inside the LAC, which reduces the resistance of concrete to drying shrinkage and freeze-thaw cycles. This research provides theoretical support for the application of SSA in sustainable LAC and reducing the damage of SSA to the environment.

Lithium slag (LS), a by-product of lithium extraction processes, poses a significant disposal challenge during the rapid development of new energy technologies. In this study, LS was used to replace partially washed sand in the process of mortar production to compensate for the content of stone powder in sand. Five mortar mixes containing varying proportions of LS were prepared, and the macroscopic performance was evaluated. A comprehensive microscopic analysis, including microstructure observations, hydration product identification, and pore structure analysis, was conducted. The impact of LS on the chloride ion permeability of mortar was also investigated in this study. The results indicate that an increase in LS content gradually reduces the workability of the mortar, with a 39.29% decrease in fluidity when 40% of the sand is replaced with LS. Moreover, the compressive and flexural strengths of the mortar initially increase and then decrease with higher LS content. Microscopic tests reveal that 20% LS substitution significantly optimizes the pore structure of the mortar, resulting in a lower chloride ion permeability coefficient. Consequently, 20% LS substitution is recommended as the optimal dosage for use as fine aggregate in mortar.

Concrete structures face significant challenges in sulfate-rich environments, where sulfate attack can affect their durability and structural integrity. This study explores innovative approaches to enhancing concrete performance by integrating hydrophobic and densification technologies. It emphasizes the critical role of anti-sulfate erosion inhibitors in mitigating sulfate-induced damage, reducing water absorption, and inhibiting corrosive reactions. This research addresses prevalent issues in Chinese engineering projects where high sulfate concentrations are common, necessitating robust solutions for sulfate resistance. Through rigorous testing, including wet–dry cycling tests with 5% and 10% Na₂SO₄ solutions following the GB/T 50082-2009 standard, concrete formulations achieved exceptional long-term sulfate resistance, meeting or exceeding KS200-grade requirements. These findings provide valuable insights into optimizing concrete durability in sulfate-rich environments, offering practical strategies to enhance infrastructure resilience and reduce maintenance costs.

The alkali–carbonate reaction (ACR) is a type of alkali–aggregate reaction (AAR) that may lead to serious damage in concrete construction. There is sufficient research on the effect of the ACR on dolomite limestone; however, research on the effect of the ACR on pure dolomite is absent, and there are a large number of dolomite resources that cannot be effectively utilized in civil engineering. This study aims to investigate whether the ACR occurs in pure dolomite spoil and to determine the freeze–thaw resistance of pure waste dolomite slag-based concrete (PWDSC). In this study, X-ray diffraction (XRD) and the lithofacies method (LM) confirmed that the tested samples were pure dolomite. The rock cylinder method (RCM) and rapid preliminary screening testing for carbonate aggregates (AAR-5) were employed to determine the alkali activity of pure dolomite: the RCM indicated a variation of −0.09% in length during the 84-day test period, the AAR-5 exhibited a length expansion rate of 0.03% within 28 days, and the expansion rates were less than 0.1%. These findings suggest that pure waste dolomite slag (PWDS) does not possess alkali activity. The freeze–thaw cycle test showed no significant spalling on the concrete surface, the inside of the cement produced few micro-cracks according to scanning electron microscopy (SEM), and the uniaxial compressive strength (UCS) test showed a decrease of approximately 20% after 200 freeze–thaw cycles. The results verified that ACR does not occur in PWDS and that it can withstand freeze–thaw damage, to a certain extent, when used as concrete coarse aggregate.

The stability of the grouting material under the coupling effect of sulfate attack and dry–wet cycles is essential to engineering safety. As a novel grouting material, the stability research of high‐water quick‐setting material (HWQSM) under different corrosive environments is in the initial stage. Moreover, the stratified damage characteristics (SDC) of HWQSM under sulfate attack were not fully explored. To this end, the strength degradation and SDC of HWQSM exposed to three kinds of sulfate solutions (i.e., 10% MgSO ₄ solution, 10% Na ₂ SO ₄ solution, and hybrid solution of 5% Na ₂ SO ₄ and 5% MgSO ₄ ) and dry–wet cycles were analyzed by using ETM‐C mechanical testing machine, scanning electron microscopy (SEM), XRD, and AFM. The results show that the strength reduction rate, the thickness of the corrosion layer, and roughness between the corrosion layer and the transition layer of HWQSM are all positively correlated with the concentration of Mg ²⁺ in the erosion solution for the increase in dry–wet cycles. Under the combined action of ion erosion and carbonization, the pores and cracks of the corrosion layer expand, which would reduce the permeability resistance but increase the erosion damage rate. This research furnishes new views into the SDC of HWQSM under sulfate attack and dry–wet cycles, which would deeper our understanding to this special material undoubtedly; the research results are expected to furnish theoretical guidance of HWQSM resistance to different sulfate solutions.

As a new grouting reinforcement material, high‐water materials (HWMs) are being increasingly applied in different fields. This means that the environment in which these HWMs are employed are varied and increasingly complex. The dehydrating and saturation cycle of HWM caused by changes in the environment is referred to as the dry‐wet cycle. To explore the influence of the dry‐wet cycle on the mechanical properties of HWMs, uniaxial compression tests were performed on specimens with different water‐to‐cement ratios under different dry‐wet cycles. The degradation rate of the peak stress and elastic modulus increased with an increase in the water‐to‐cement ratio. The failure mode of specimens changed from splitting failure to shear‐splitting failure during the dry‐wet cycle. The results of scanning electron microscope and X‐ray diffraction showed that an HWM with a low water‐to‐cement ratio is relatively dense; therefore, the carbonization process is slow during dehydration. Raw materials were present after hydration and hardening reaction. Thus, the strength recovery ability is strong in materials with a low water‐to‐cement ratio during the saturation process. Finally, the experimental results can provide guidance for selecting materials with different water‐to‐cement ratios and control measures for dry‐wet cycle can be determined according to different engineering environments.