Passive daytime radiative cooling (PDRC) is an emerging zero-energy cooling technology capable of achieving sub-ambient cooling even under intense sunlight. However, most PDRC materials face significant challenges in practical outdoor applications due to their high cost, complex manufacturing processes, and susceptibility to abrasion and pollution, which degrade their performance. In this paper, the composite coatings with both radiative cooling and environmental tolerance were synthesized by layer-by-layer (LBL) self-assembly technology using montmorillonite (MMT) and hydroxide (LDH) as the main radiatively cooling raw materials, and polyvinyl alcohol (PVA) was introduced to enhance the binding force. Therefore, we can get PVA/MMT/LDH (P/ M/L) composite coatings with high solar reflectance (65 %) and strong infrared emissivity (98 %). Under simulated sunlight at 987 W/m2, it achieves excellent cooling of 13.4 degrees C below ambient temperature. Moreover, in outdoor tests, the P/M/L composite coatings can reduce temperature by up to 10 degrees C. The composite coatings demonstrate superior wear resistance and environmental stability, withstanding a pH range of 3-11 and diverse salt solutions, while retaining over 99 % of its initial weight following abrasion. Furthermore, its tensile strength attains 18.85 MPa, thereby effectively overcoming the key challenges associated with outdoor applications. This work provides a promising solution for energy-saving and environmentally friendly applications in the future.

Alkali-activated binders (AABs) represent eco-friendly alternatives to ordinary Portland cement. Nevertheless, the synergistic influences of calcium dosage and aluminosilicate stoichiometry on phase assemblage, gel nanostructure, and mechanical properties have not been fully elucidated. Herein, AAB samples with graded CaO contents were fabricated, and the co-regulatory mechanisms of CaO dosage and Si/Al molar ratio on compressive strength and microstructural evolution were systematically explored through compressive strength tests, XRD, TG-DTG, FTIR, and SEM-EDS. In addition, pure reference C-S-H and N-A-S-H gels were synthesized by using the sol–gel method for comparison with AAB pastes. The results reveal that CaO dosage acts as the primary parameter dictating gel phase transition and strength level, categorizing the prepared AABs into three distinct zones: low-calcium region (CaO < 10 wt.%), medium-calcium region (10–20 wt.%), and high-calcium region (CaO > 20 wt.%). Combined grey relational and partial correlation analyses clarify the collinearity-induced false correlations and reveal the stage-dependent independent effects of oxide molar ratios on AABs’ compressive strength. Low-calcium AAB matrices are dominated by N-A-S-H gel networks coexisting with abundant low-strength zeolite crystals, which deteriorate thermal stability and retard strength gain. Increasing CaO content triggers a progressive phase transformation from N-A-S-H gel to high-strength C-(A)-S-H gel. Abundant Ca-rich chabazite and C-S-H gel form in high-calcium systems, which fill internal pores and microcracks and greatly enhance matrix densification and thermal resistance. This work clarifies the multiscale regulatory mechanism of calcium species over gel polycondensation, crystalline phase development, and mechanical performance of AABs, offering fundamental theoretical guidance for the customized design and property optimization of high-strength alkali-activated binders.

Dehydroxylation of kaolinite is a pivotal step in the preparation of supplementary cementitious materials and geopolymer precursors, yet its atomistic mechanism remains elusive. By integrating static DFT calculations (CI-NEB/DIMER), metadynamics simulations, and wave function analyses (MBIS charges, FBO, sobEDA), a dehydroxylation mechanism dominated by proton (H+) migration was revealed. Kinetic simulations at 1200 K identified interlayer migration (Path I, Delta G double dagger= 216.64 kJ & sdot;mol-1) and adjacent surface migration (Path II, Delta G double dagger= 141.52 kJ & sdot;mol-1) as feasible pathways. Energy decomposition analysis indicated that Path I was governed by Pauli repulsion, whereas Path II was controlled by the cost of bond breaking. The calculated barriers for both paths fell within the experimental activation energy range (140-255 kJ & sdot;mol-1). Thermogravimetric simulations quantitatively mapped the temperature domain contributions of Path I and Path II, thereby validating, for the first time at the macroscopic scale, their competing mechanism. The "static-dynamic-electronic-macroscopic" multiscale framework established herein offered a universal theoretical model for understanding the dehydroxylation of hydroxyl bearing solids.

Municipal solid waste incineration fly ash (MSWIFA) contains high concentrations of heavy metals and chloride ions, which severely limits its resource utilization, as scarce studies focus on the synergistic disposal of these two pollutants. Compared with traditional cement solidification technology, alkali activation technology has the advantages of low energy consumption, low carbon emissions and stronger adaptability to chloride ions. In this study, layered double hydroxide (LDH), calcined layered double hydroxide (CLDH), and nano-SiO2-CLDH composite (SiO2@CLDH) were utilized as modifiers to investigate the solidification and stabilization of alkali-activated MSWIFA materials. The effects of modifiers on the mechanical properties and ion leaching characteristics of materials, as well as the synergistic solidification mechanism, were explored. The results indicated that SiO2@CLDH exhibited the best performance improvement. It increased the 60-day compressive strength by 45.7%, while reducing the 28-day leaching concentration of Pb by 33.3% and Cl-leaching concentration by 66.3%, compared with blank group. The pozzolanic effect of nano-SiO2 and the rehydration effect of CLDH synergistically accelerated the hydration reaction, promoted the formation of highly polymerized C-S-H gel, and refined the pore structure of the cementitious materials. SiO2@CLDH achieved efficient synergistic solidification of heavy metals and chloride ions through the combined effects of chemical binding, physical adsorption, and pore retardation. This study provides a new modified material and theoretical reference for the harmless and resourceful disposal of MSWIFA.

Abstract In this research, cement mortar with oil shale residue and polycarboxylate superplasticizer was produced. The strengths, water absorption ratio, and fluidity of these cement mortar samples were measured. The cross-sectional morphology characteristics and porosity of these cement mortar samples were also studied. Meanwhile, the water-cement ratio effect on cement mortar was represented by comparing the above properties of reference samples. The experimental results indicated that oil shale residue (OSR) exerted a more pronounced effect on the porosity and fluidity of cement mortar (As can be observed from Figures 2 and 5). The cement mortar had the highest compressive strength when the polycarboxylate superplasticizer content was 0.5%. At both 1h and 24 h, cement mortar with a water-cement ratio of 0.6 showed a higher water absorption ratio and fluidity. But the higher the water-cement ratio, the lower the strength of the samples. Cement mortars had similar application properties, regardless of the polycarboxylate superplasticizer contents. So the oil shale residue and water-cement ratio were the main factors of cement mortar application properties.

A preparation method for recycled semi-flexible pavement (RSFP) materials was proposed to improve recycled pavement performance and diversify reclaimed asphalt pavement (RAP) recycling approaches. This study investigated the high-temperature performance, low-temperature performance, water stability, secondary aging resistance, fatigue performance, and engineering applications of RSFP materials. Experimental results show that RSFP materials possess better high-temperature stability and secondary aging resistance than conventional recycled pavement materials. RSFP material performance is directly affected by the asphalt skeleton's air voids and the cementitious grouting material's filling rate. A denser and thicker internal cement skeleton enhances high-temperature stability, while a thinner and less continuous structure improves resistance to low-temperature cracking. A lower filling rate results in a more fragmented cement skeleton, which reduces the fatigue life of RSFP materials. Notably, RSFP materials achieve optimal fatigue life at an air void content of 25 %. The application of RSFP materials was validated through two years of monitoring on an experimental road, confirming their suitability for heavy traffic conditions. These findings promote sustainable road construction practices and offer an effective solution for utilizing RAP in high-traffic infrastructure.

Carbonation curing of steel slag is an effective strategy to increase its utilization and achieve carbon sequestration in building materials production. This study investigated the effects of industrial Vitamin C (VC) on the carbonation process of steel slag/cement pastes to improve carbonation efficiency and mechanical properties. After carbonation, the internal and external carbonation degrees and the compressive strength of the specimens were evaluated. The results demonstrated that an increase in VC concentration led to elevated Ca2+ leaching, with the highest VC group exhibiting an 870.62 % increase in Ca2+ concentration compared to the reference group (without VC), thereby facilitating the formation of calcium carbonate. The inclusion of VC increased carbonation depth and improved the mechanical properties of the steel slag/cement paste. The maximum compressive strength was 34.67 MPa and the CaCO3 content of the internal sample achieved 19.41 %, respectively, representing increases of 138.61 % and 311.23 % over the group without VC. However, VC inhibited the hydration process, resulting in slower late-stage strength development compared to the group without VC. After 28 days, the compressive strength of carbonated steel slag/cement pastes containing VC reached up to 45.23 MPa, which was 30.72 % higher than that after carbonation. Calcite was identified as the primary carbonation product, appearing as individual cubic grains in the reference samples and as stacked formations in the VC-containing samples. This study improved inhomogeneous carbonation of steel slag products and provided inspiration for enhancing steel slag and other calcium-based cementitious materials.

Metals extraction and processing generate a substantial amount of industrial waste, posing significant environmental hazards. To reduce the accumulation of such waste, this paper incorporates steel slag (SS) into a lime (CH)–sodium sulfate (SN) composite-activated cementitious system. The mechanical properties, hydration products, and microstructure of the cementitious system with varying SS contents were characterized. The results indicate that the addition of SS not only enhances the mechanical properties of the cementitious system but also significantly reduces its cost and energy consumption. When the content of SS is lower than 30

Supplementary cementitious materials (SCMs) are essential for enhancing both the performance and sustainability of modern cement systems. Among these, lithium slag (LS) has emerged as a promising candidate, though its impact on cement hydration remains insufficiently understood. As an aluminosilicate-based material, LS can synergistically interact with carbonate additives like limestone powder (LP), promoting the formation of carboaluminates. This synergy not only significantly reduces cement consumption but also markedly enhances the long-term performance of cementitious systems. However, the combined use of LS and LP as a SCM remains underexplored and warrants further investigation. Therefore, this study examines the hydration of LS-blended cement in the presence of LP. Additionally, the pore structure and aluminosilicate component in LS were analyzed to comprehensively evaluate its role as an SCM. The results indicate that aluminosilicates in LS exhibit high polymerization, which limits its reactivity. Nevertheless, LS’s unique pore structure facilitates internal curing, which, along with pozzolanic reactions, enhances late-age strength and microstructure. Additionally, LS serves as an internal source of sulfate and aluminate, mitigating premature sulfate depletion caused by LP’s hydration-accelerating effect and promoting the formation of carboaluminates. LS also enhances the polymerization of C-(A)-S-H by lowering the Ca/Si ratio and increasing the Al/Si ratio, achieving a mean chain length (MCL) of 3.590 at 28 d. The blended cement with 45% combined SCM achieves MCL values and 90-day compressive strengths comparable to those of pure cement, demonstrating its potential for sustainable cement development.

The use of shellfish waste as a raw material in cement and concrete production is recognized as a feasible approach. Similar to limestone, seashell powder (SP), which is primarily made up of calcium carbonate, has been identified as a promising supplementary cementitious material (SCM). However, the current understanding of SP's chemical interactions within aluminum-rich cement systems remains limited, often resulting in its classification as simply an inert filler. Therefore, this research seeks to clarify the contribution of SP to fly ash (FA) cement by investigating the hydration products. The investigation reveals that SP facilitated hydration albeit to a lesser extent compared to limestone. In cements incorporating SP, the AFm phases, characterized by carboaluminate formations, became predominant, and the calcium carbonate content diminished over time, indicating reactive engagement of SP. The addition of 5 % SP enhanced the polymerization of the C-(A)-S-H structure in FA cement. Moreover, the substitution of cement with SP elevated the effective water to cement ratio, leading to a reduction in the Ca/Si ratio of C-(A)-S-H, while the Al/Si ratio remained virtually unchanged. Analysis identified the presence of monocarboaluminate (Ca/Al/C atomic ratio of 4: 1.97: 4.39) and hemicarboaluminate (Ca/Al/C atomic ratio of 4: 2.25: 2.40) in FA cements with 5 % and 10 % SP additions, respectively. Nonetheless, incorporating SP negatively impacted the compressive strength of FA cement, underscoring the importance of using SP in moderation. Specifically, the 28-day compressive strengths of FA cements with 5 % and 10 % SP additions measured at 42.9 MPa and 40.2 MPa, respectively. Moreover, SP-FA cement offers significant environmental advantages. This research innovatively elucidates the reaction mechanism of SP within fly ash cement, offering vital insights into SP's impact on the hydration process and advancing the recycling of shellfish waste.

Utilizing a variety of solid wastes to prepare alkali-activated cementitious materials is one of the principal trends in the development of cementitious materials. Commonly used alkali activation precursors such as granulated blast furnace slag (GBFS) and fly ash (FA) will be less available due to resource pressures. Supply limitation is an important reason to research alternative precursors. To realize the high value-added utilization of copper–molybdenum tailings (CMTs), this study adopted the modified sodium silicate solution as an alkaline activator to activate GBFS-FA-CMTs cementitious system to prepare alkali-activated cementitious materials. The influence of CMTs content on the compressive strength of GBFS-FA-CMTs cementitious system was analyzed, and the mechanism of GBFS-FA-CMTs cementitious system was also analyzed through hydration product types, physical phase composition, and microscopic morphology. The results indicated that a paste with the incorporation of CMTs, S50F30C20 (50% GBFS, 30% FA, 20% CMTs), achieved the highest compressive strength of 79.14 MPa, which was due to the filling effect of the CMTs and the degree of participation in the reaction. Pastes with different contents of CMTs, while maintaining a constant CBFS content, exhibited similar strength development. Excessive amounts of CMTs could result in reduced compressive strength. Microstructural analysis revealed that the hydration products were structurally altered by the addition of CMTs. In addition to ettringite, quartz, C(-N)-S-H gel, and calcite, gaylussite was also formed; moreover, the mass of chemically bound water increased, and the microstructure of reaction products became denser. An excess of CMTs may restrict the growth of the hydration gel, leading to more microstructural defects. The study suggests that CMTs could enhance the compressive strength of hardened paste within an alkali-activated slag-fly ash system, possibly due to a filling effect and participation in the chemical reaction. This research confirms the feasibility of using CMTs in alkali-activated cementitious materials.

This study aimed to study the effects of different carbonation-hydration processes and carbonation degrees on the mechanical properties and leaching behavior of heavy metals in stainless steel (SS) slag paste. SS slag powders were carbonated at different water/solid ratios, and cement paste containing 50% by weight carbonated SS slag were prepared and employed in different carbonation-hydration approaches. CO2 uptake of SS slag powders seriously depended on water/solid ratio, and the optimum water/solid ratio for carbon sequestration was 8% in the experimental range. The long-term cumulative leaching fractions of Cr and Ni in carbonated SS slag powder decreased with carbonation progress, whereas excessive carbonation showed negative effects on the immobilization of heavy metal ions. The 30-day cumulative leaching fraction of Cr and Ni of SS slag powder with carbonation degrees of 36.2% were 65.8% and 43.2% lower than raw SS slag. Carbonation-hydration curing approaches showed obvious effects on mechanical property development and leaching characteristics of heavy metals of SS slag paste. The CO2 uptake of SS paste were positively correlated to the hydration period before carbonation curing, and CO2 uptakes of 14.5% and 17.2% were obtained for H3C6 and H28C6 (H3C6 and H28C6 refer to SS paste specimens first cured in a concrete-curing room for 3 and 28 days, respectively, and then subjected to carbonation curing for 6 h). Carbonation curing for 2 h after hydration first for 3 days can increase the 28-day compressive strength by 27.7%, and the cumulative leaching fractions of Cr and Ni of H3C6 decreased by 58.2% and 44.4%, respectively.

The efficient utilization of coal gasification slag (CGS) to prepare alkali-activated materials (AAMs) presents a significant opportunity for addressing the challenges associated with solid waste accumulation and environmental degradation. However, the aluminosilicate glass in CGS is highly polymerized, rendering it challenging to stimulate its potential reactivity. Additionally, the presence of residual carbon impedes the hydration process in AAMs, thereby limiting its applicability. This study focuses on the residual carbon content and polymerization degree of CGS after calcination treatment to overcome these challenges and improve the reactivity of CGS. Results revealed that residual carbon in CGS underwent thermal decomposition, increasing the proportion of aluminosilicate glass components. The degree of polymerization of CGS was reduced by 25 % under calcined conditions at 550 degrees C, whereas at 700 degrees C, CGS recrystallized, and the aluminosilicates were again highly polymerized. The highest reactivity of CGS was observed after calcination at 550 degrees C. The 28 days compressive strength of the prepared AAM paste reached 47.5 MPa, representing an increase of 18.45 % compared to the control. This study innovatively elucidates the physicochemical properties of calcined CGS. It highlights the critical importance of controlling calcination conditions to manage the polymerization degree and phase transformations during carbon removal, thereby enhancing the reactivity and performance of AAMs.

A geopolymer is a low-carbon cementitious material, and its condensation process is akin to the formation of inorganic polymers. The crystal phase of synthesized geopolymers was identified using XRD; the scattering peaks of amorphous phases were analyzed, and the zeolite minerals akin to different n(Si)/n(Al) geopolymers were determined. Based on this, a model structure of N-A-S-H geopolymers was established. The molecular dynamics structure of the model was simulated, and the density, energy, and bulk modulus of the model were calculated using three different force fields. According to the calculation results, the most suitable force field for N-A-S-H calculation is COMPASS III. In this study, all calculations were performed using MaterialsStudio 7.0. The research process introduces a new modeling method for geopolymers, similar to building C-S-H based on Tobermorite, which aids in advancing the molecular dynamics simulation of geopolymers.

The passive film of reinforcing steel in marine concrete is damaged by the infiltration of chloride and sulfate ions. Layered double hydroxide (LDH) can adsorb anions and release interlayer ions to form passive films due to its ion exchange property. A Mg-Al-NO 3 layered double hydroxide/montmorillonite (LDH/Mnt) composite inhibitor was prepared by layer-by-layer self-assembly (LBL) of LDH and Mnt. The structure and morphology of the LDH/Mnt composites were characterized by X-ray diffraction (XRD), laser Raman spectroscopy, N 2 -adsorption/desorption measurements, and transmission electron microscopy (TEM). The LDH/Mnt composites, as inhibitors of chloride ions and sulfate ions, exhibited high slow-release efficiency. The mass ratio of LDH and Mnt affected the curing capacity of the synthesized composites, and the optimum mass ratio was LDH/Mnt = 1:1 for which slow-release efficiency reached 94.16%.

Nano-sized C-S-H, a promising early strength agent, can accelerate the hydration rate of Portland cement and increase the early compressive strength of cement-based composites effectively. Nano-sized C-S-H suspensions with different contents of effective constituent and size distributions were prepared by a convenient coprecipitation method and the microstructures were analyzed by Zeta potential, XRD and FT-IR. The exothermic heat, early mechanical properties, hydration degree and hydration products of cement with/without nano-sized C-S-H cured at different temperatures were studied by hydration exothermic, XRD, SEM and TG analysis. Nano-sized C-S-H with semi-crystalline structures was prepared, and the size of the nano-sized C-S-H seeds showed an obvious increase with an increase in theoretical concentration, and slight precipitation in the suspension was observed when the theoretical concentration was 2%. The XRD, TG and SEM analyses showed that nano-sized C-S-H expedites the reaction of C3S in the first 24 h; therefore, the hydration induction period is obviously shortened. The 8 h, 16 h and 24 h compressive strength of mortars containing nano-sized C-S-H increased by 176.0%, 145.6% and 43.9%, respectively, compared with the reference mortar. The enhancement effects of nano-sized C-S-H at 10 °C were lower than that at 20 °C.

选用矿渣和粉煤灰为原料,陶粒为轻集料,水玻璃为碱激发剂,采用物理发泡法,通过碱激发方式制备地聚合物基陶粒泡沫混凝土(GCFC),研究泡沫掺量、陶粒掺量及陶粒等级对GCFC性能的影响,探究了GCFC孔结构的变化趋势.结果表明:当陶粒掺量为30％、陶粒等级500 kg/m3时,随着泡沫掺量增加,当泡沫掺量1.0倍时,比强度达到峰值10273 N·m/kg,导热系数为0.109 W/(m·K);当泡沫掺量1.2倍、陶粒等级500 kg/m3时,随着陶粒掺量增加,GCFC比强度先增大后减小,掺量为30％时比强度达到峰值9902 N·m/kg,导热系数为0.097 W/(m·K).当泡沫掺量小于1.2倍,经20次冻融循环后GCFC的质量损失率和冻后强度满足标准要求;GCFC冻后强度与陶粒等级成正比关系.GCFC孔结构的圆度值随泡沫掺量的增加而变大,当泡沫掺量超过1.2倍后,圆度值增加速度加快;当陶粒掺量逐渐增大时,平均圆度值先降低再升高,陶粒掺量为30％时平均圆度值下降至最低为1.42.