CO2 curing and the use of steel slag in cementitious materials represent a promising strategy towards low-carbon concrete, but how this combination affects long-term steel corrosion under chloride attack remains insufficiently explored. Here we investigated the mechanistic evolution of steel corrosion in carbonation-cured steel slagblended mortars by cyclic chloride exposure, using electrochemical measurements alongside microscopic characterization. Our results show that a 10 wt% steel slag addition improves chloride immobilization and microstructural compactness, which in turn delays corrosion initiation and early development. Electrochemical tests confirm that the corresponding mix (M-LG10) maintains stable low-frequency impedance curves over 240 drywet cycles. Its open-circuit potential (Eocp) shifts slowly, and icorr remains below 0.1 mu A/cm2. However, this protective effect weakens with prolonged exposure. After 480 cycles, the alkalinity loss from the carbonationcured system's low alkali reserve and water dilution compromises long-term passivity, making M-LG10 perform worse than the standard-cured NA-1 group. Microscopic analysis shows that M-LG10 eventually develops the thinnest corrosion layer in carbonation-cured groups, which has a dense structure. In contrast, mixtures without steel slag (M-LG0) or with 20 wt% slag (M-LG20) exhibit needle-like beta-FeOOH corrosion products that lack protective capability. Chloride enrichment at the steel-mortar interface accelerates corrosion, ultimately resulting in thicker, loosely structured corrosion layers accompanied by rust-expansion cracks. Taken together, our findings suggest that while carbonation curing combined with an appropriate steel slag content can enhance corrosion resistance during the early stage of chloride exposure, sustained long-term protection will require additional alkalinity to compensate for the inherent limitations of carbonation curing.

This study aims at investigating the mechanism through which limestone calcium carbonate (CC) powder particle size and replacement level regulate cement paste rheology, systematically probing the hydration process, water state migration, particle flocculation, and pore solution ion evolution. Results demonstrated that a 10 wt% cement substitution by CC particles coarser than cement reduced the paste's initial static yield stress, dynamic yield stress, and plastic viscosity by weakening interparticle interactions and ionic strength, improving flowability. Conversely, CC particles finer than cement increased these parameters due to enhanced flocculation and agglomeration. Coarser CC also hindered static yield stress development over time by retarding hydration and increasing double-layer repulsion, while finer CC accelerated static yield stress growth at higher replacement levels via promoted hydration and flocculation. These findings offer valuable insights for CC-based rheological control in cementitious materials.

Superhydrophobic silica fume (SSF) holds significant potential for enhancing the durability of cement-based materials in corrosive environments. Nevertheless, the trade-off between hydrophobicity and mechanical performance remains a critical challenge. SSF enhances the anti-corrosion performance of cement-based materials but reduces their early strength. This study reveals SSF's unique strength recovery mechanism: The alkaline environment progressively hydrolyzes the grafted silane layers, as directly evidenced by XPS, which shows a 13.06 % decrease in C-C/C-H bonds and a concurrent 10.81 % increase in Si-O-Si networks over 7 d. This alkaline hydrolyzes enables a delayed pozzolanic reaction, narrowing the gap in Ca(OH)2 consumption from 1.8 % (3 d) to 1.0 % (56 d) in a simulated system and driving a more than twofold increase in Q3 content in cement paste. Consequently, this delayed pozzolanic reaction underlies the observed strength recovery, effectively narrowing the compressive strength gap to 7.5 % at 56 d. This study confirms that the hydrophobic modification only temporarily suppresses reactivity, enabling a unique self-recovery mechanism that reconciles early-stage durability with long-term strength.

This study investigates the mechanism by which ground steel slag (SS) influences the static yield stress (SYS) evolution of cement-silica fume (SF) blended paste. Through analysis of hydration kinetics, water states, pore structure, particle flocculation, and ion concentration in pore solution, results demonstrate that SF markedly increases initial SYS due to its high specific surface area, promoting particle agglomeration, elevating flocculated water intensity, and accelerating hydration. Incorporating 20 % SS can significantly reduce the initial SYS, particularly counteracting the adverse effect of SF. This reduction stems from decreased solid volume fraction, flocculated water intensity, and ionic strength, enhancing fluidity. In addition, the incorporation of SS can refine the paste's pore structure, thereby facilitating the subsequent SYS growth. Thus, SS effectively mitigates the SF-accelerated early SYS development through delayed hydration while maintaining adequate SYS levels, benefiting applications like printable cementitious materials by extending the printable time window and ensuring build-ability. This study achieves synergistic rheological control by leveraging the distinct characteristics of SS and SF.

As an innovative biomimetic surface, slippery surface demonstrates remarkable properties such as water repellency and self-cleaning. Due to its intriguing features, many researchers have employed them as mist collectors for water harvesting in deserts and arid regions. This study investigates the effects of magnetic fields (MF) on droplet condensation and evaporation dynamics on PDMS/paraffin solid slippery surfaces (PSSS). Through experimental and computational analyses, it was demonstrated that magnetic fields enhance droplet evaporation rates on PSSS, thereby delaying condensation and reducing collected water volume by up to 18.4 % under stronger fields (230 mT). Notably, under low relative humidity (RH), distinct "evaporation rings" emerged in high-MF regions, attributed to accelerated localized evaporation and humidity reduction. COMSOL simulations validated that MF intensity gradients correlate with ring formation, as stronger fields reduce surface RH and inhibit droplet nucleation. Additionally, MF exposure reduced water droplet contact angles, expanding vapor-liquid interfacial areas and further promoting evaporation. These findings bridge the gap between magnetic interactions and phase-change processes at engineered interfaces, offering critical insights for optimizing water harvesting technologies in arid, mineral-rich environments where geomagnetic anomalies may influence efficiency. The study underscores the interplay of environmental factors and surface engineering in sustainable water collection systems.

The long-term durability of cement-based materials is inherently reliant on water migration within porous structures. This study leverages the potential of low-cost silica fume (SF), a waste-derived resource, and combines it with the "Lotus Effect" principle to create superhydrophobic silica fume (SSF), which is then used to impart superhydrophobicity to cement-based materials. The findings reveal that incorporating 4 wt% (the weight ratio of cement) of SSF into cement-based materials achieves a water contact angle (WCA) of 151.79 degrees, effectively mitigating water penetration. Furthermore, the impedance value of the superhydrophobic cement-based materials containing 4 wt% SSF group demonstrates a nearly 100-fold enhancement in anti-corrosion compared to the Control group, accompanied by significantly reduced chloride ion diffusivity. For concrete that introduces SF and SSF, a significant negative correlation (R-2 > 0.99) is observed between the fractal dimension of micropores (D-2) and chloride diffusion coefficients, indicating that higher fractal dimensions (i.e., more complex pore structures) effectively hinder chloride migration. These findings collectively demonstrate that incorporating SSF enhances the corrosion resistance of concrete materials, preventing Cl from reaching the concrete-steel interface. Given the large-scale and efficient production capabilities of SSF, coupled with its ease of transportation, it emerges as a promising option for mitigating chemical erosion in marine infrastructures.

While Portland cement produces large amounts of carbon dioxide, low-calcium high-strength cements effectively reduce carbon emissions by decreasing the proportion of high-calcium minerals. In order to enhance the practical application value of low-calcium high-strength cement, the effects of mineral admixtures on the chloride binding capacity and pore structure characteristics of low-calcium high-strength cement pastes were investigated by equilibrium method and mercury intrusion method. The results showed that the chloride binding capacity of low-calcium high-strength cement pastes is superior to that of Portland cement. Fly ash and slag enhance this capacity by promoting monosulfoaluminate and C-S-H gel formation, with fly ash being more effective. Ground limestone also boosts chloride binding when incorporated at less than 10 wt%. However, sulfates have a more significant negative impact on chloride binding capacity in low-calcium high-strength cement pastes compared to Portland cement. The porosity of low-calcium high-strength cement pastes exhibits contrasting trends with the addition of fly ash, ground limestone, and slag. Fly ash and limestone initially coarsen the pore structure but later facilitate the transition of larger pores to smaller ones. In contrast, slag initially has little impact but later promotes the conversion of large capillary pores to medium ones, optimizing the pore structure. Notably, above 10 wt% fly ash, the critical pore diameter decreases with additional fly ash except at 10% where it increases for 3 days. Ground limestone enlarges the critical pore diameter, and this effect intensifies with higher content. During early hydration, slag decreases the critical pore diameter, but its impact diminishes in later stages.

The issues of cracking, spalling, and corrosion of concrete structures are major causes of significant losses. One of the most effective strategy to prevent these phenomena from occurring is to keep concrete from being wetted. However, many hydrophobic modifiers are liquid, which are difficult to transport and easy to volatile. This work selects silica as the substrate and uses fluorine-free silane as the hydrophobic modifier to design and develop a self-made solid superhydrophobic powder that can be directly mixed with cement and sand to produce monolithic superhydrophobic concrete (SC). Benefiting from the rough structure and low surface energy, the SC surface maintains superhydrophobicity with a large water contact angle (WCA) of 153.8°, causing droplets to easily roll off from the SC surface. The SC has a lower corrosion current density (Icorr = 3.878 × 10−6 A·cm−2) and a higher corrosion potential (Ecorr = – 0.368V), and its corrosion resistance is significantly improved than that of ordinary concrete (OC). In addition, the adhesion between pollutants and concrete is effectively reduced, and the surface resistance to dust and dirt is enhanced. This work developed a simple and convenient strategy for the preparation of SC with excellent anti-corrosion and self-cleaning properties, which has great engineering and scientific significance.

The micro-cracks in a material lead to a reduction in its overall strength and service life. The emerging capsule-based self-healing system provides a new strategy for repairing the cracks, effectively delaying the potential damage of the matrix, and prolonging the service life of composite materials. Determining the optimal size and dosage of microcapsules required to repair cracks in the matrix is essential for the development and design of capsule-based self-healing materials. This paper presents a novel two-dimensional capsule-based self-healing model composite material whose surface is paved by reproducible and random cells and some microcapsules are randomly dispersed in those cells to investigate the rupture behavior of microcapsules forced by growing cracks. An analytical model is proposed from the viewpoint of geometrical probability to express the probability characteristics of the embedded microcapsules stimulated by linear cracks in a two-dimensional capsule-based self-healing model composite. Additionally, the effect of the size and dosage of the embedded microcapsules on the intersection probability is analyzed, and the maximal probability is also found to improve the self-healing efficiency. Finally, the accuracies of these probability values and theoretical solutions are verified via computer simulation, and the results show that the developed model of the geometrical probability of the crack intersection with microcapsules randomly distributed in the cells of the matrix will help to provide a theoretical basis for the quantitative design of capsule-based self-healing materials.

To better understand the limitations of the hydrotalcite formation and the capacity of hydrotalcite to bind chloride in dolomite-containing Portland cement-based materials, the reaction of dolomite in C3A pastes and the corresponding chloride binding behavior were investigated in this study. The phase assemblages, the chloride binding capacity, and the pH value were determined. The results indicate that hydrotalcite can only form in a limited range of (active magnesium)/(available aluminum) ratios. The dissolution of dolomite, which provides the magnesium activity, rather than the dedolomitization reaction, appears to be what drives the dolomite reaction with C3A and is primarily dependent on dolomite content. The hydrotalcite formation is not affected by Ca(OH)2. Hydrotalcite seems to possess a greater capacity to bind chloride than monocarboaluminate in hydrated C3A pastes, especially at high chloride concentrations. Chemical chloride binding contributes approximately 10% to the total chloride binding capacity of hydrotalcite. The remaining dolomite reduces chloride binding by increasing carbonate ion activity, and Ca(OH)2 reacts with dolomite to decrease carbonate ion activity and thereby promote chloride binding.

混凝土材料在荷载和环境作用下容易发生开裂,影响结构的耐久性以及强度.受胶囊法自修复体系的启发,以多孔轻骨料为载体,研究人员提出内置封装修复剂材料的轻骨料自修复体系.评述了近年来国内外有关轻骨料自修复水泥基材料的发展状况,阐述无机多孔轻骨料的破裂方式以及修复剂释放机理,对比分析内置修复剂轻骨料水泥基材料裂缝愈合前后的基体力学性能和耐久性能,以及裂纹愈合程度和愈合效率的评价方法,总结了轻骨料自修复水泥基材料裂缝修复研究所存在的主要问题,展望了其研究趋势和发展前景.

研究了稻壳灰(RHA)对水泥-石灰石粉浆体强度的改善作用,并通过热重和X射线衍射测定了水泥-石灰石粉-RHA复合浆体的水化程度及水化产物,分析了相关作用机理.结果表明:复合浆体抗压强度随着RHA掺量的增加先增后降,RHA掺量为10％时,复合浆体抗压强度达到最高,与纯水泥浆体相比,掺入10％RHA和10％石灰石粉的复合浆体3、7、28 d抗压强度分别提高了8.21％、18.43％、1.75％,掺入15％RHA有助于提高浆体抗压强度随龄期的增长幅度;RHA具有一定的填充效应、活性效应及内养护作用,掺量小于10％时,RHA填充效应和活性效应起主导作用,能够加速C3S的水化,并进行二次水化反应,提高复合浆体早期抗压强度;RHA掺量增至15％时,因RHA吸附大量水分,降低了水泥的水化程度,导致复合浆体早期抗压强度较低,但随着龄期的增加,RHA逐渐释放吸附水,起到内养护作用,促进水泥水化及参与二次水化反应,从而提高了复合浆体抗压强度的增长.

采用平衡法研究了CaCO3和CaSO4·2H2O共同存在时Ca2+对C3A水化浆体氯离子固化能力、生成产物和氯盐溶液pH值的影响.结果表明:C3A水化浆体固化氯离子后生成含氯铝酸盐并释放OH-,提高了氯盐溶液的pH值;CaCO3和CaSO4·2H2O分别作用时均会降低C3A水化浆体的氯离子固化能力和氯盐溶液pH值的提高程度,CaCO3和CaSO4·2H2O共同作用时则会显著降低C3A水化浆体的氯离子固化能力;C3A水化浆体中含氯铝酸盐生成量和氯离子固化能力随氯盐溶液pH值的降低而减小,而Ca2+会降低氯盐溶液pH值的提高程度,但能提高C3A水化浆体的氯离子固化能力,CaCO3或CaSO4·2H2O单独存在时都能使Ca2+提高氯离子固化能力的效果更为显著,且CaCO3比CaSO4·2H2O的作用更加明显,但CaCO3和CaSO4·2H2O共同存在时会出现负协同作用;在CaCO3和CaSO4·2H2O共同作用下,Ca2+促进各水化产物与氯离子反应生成含氯铝酸盐的效果由小到大为:AFt＜ C3AH6 ＜AFm＜碳铝酸钙水化物,同时改变了所生成含氯铝酸盐(固溶体)的物相结构.

采用平衡法研究了氯离子浓度、氯盐溶液pH值和钙离子对铝酸三钙(C3A)水化浆体固化氯离子的能力及其固化产物的影响.结果表明:C3A水化生成的水化铝酸三钙(C3AH6)能够固化氯离子,其在碱性溶液中与氯离子反应生成的Friedel's盐(Fs)与水铝钙石(OH-AFm)之间的固溶体有2种类型,结构分别与β-Fs-R(高温三方晶系的Fs)和α-Fs-M(低温单斜晶系的Fs)类似,氯盐溶液的pH值会影响生成固溶体的类型;随着氯离子浓度的提高,C3A水化浆体中固溶体生成量和氯离子固化量增大,平衡后氯盐溶液pH值提高,但固化氯离子占总氯离子的比例降低;氯盐溶液pH值降低导致C3A水化浆体中固溶体生成量减少,氯离子固化能力减弱;钙离子减少了固溶体的生成量,降低了氯盐溶液pH值,但提高了C3A水化浆体的氯离子固化能力.

In this study, the impact of CaCO3 and CaSO4 center dot 2H(2)O on chloride binding in hydrated blended C(3)A pastes was investigated. The chloride binding capacity and pH value were obtained through equilibration method, and the phase assemblages were evaluated using XRD and Raman spectroscopy. The results showed that the exposure of the hydrated blended C(3)A pastes to NaCl solutions caused an increase of pH as a result of the chloride binding by the AFm phases. Both CaCO3 and CaSO4 center dot 2H(2)O led to the decrease of chloride binding capacity and pH value, and CaCO3 was more obvious than CaSO4 center dot 2H(2)O on reducing chloride binding capacity. The greater the CaCO3 content was, the more obvious the reduction was, while most reduction occurred for the CaCO3/C(3)A molar ratios less than 0.5. Especially, coupled incorporation of CaCO3 and CaSO4 center dot 2H(2)O caused a significant reduction in chloride binding capacity and pH, with binding capacity of ettringite < carboaluminate hydrates < monosulfoaluminate < C(3)AH(6). The chloride-bearing AFm phases formed after exposure were solid solutions which presented two monoclinic and rhombohedral polymorphs at ambient temperature, and the polymorphs were dependent on the composition of blended C(3)A pastes and chloride concentrations. CaCO3 whether with CaSO4 center dot 2H(2)O or not led to the solid solutions formation with carbonate-AFm as end member. While CaSO4 center dot 2H(2)O showed no effect on the constitution of solid solutions, but led to the transformation of polymorphs. (C) 2019 Published by Elsevier Ltd.

采用压汞法测试了水泥-石灰石粉浆体孔结构,基于热力学模型探讨了其多重分形特征以及与渗透性之间的关系.结果表明:水泥-石灰石粉浆体孔结构具有多重分形特征,阈值孔径至孔体积微分曲线上初次剧增对应的孔径之间(孔径范围II)(过渡区域)不具备分形特征,孔径范围I(小于孔径范围II,小孔分形区域)和孔径范围III(大于孔径范围II,大孔分形区域)具有分形特征,前者的分形维数大于后者;随石灰石粉掺量增加,孔径范围I和III的分形维数分别提高和降低,并对孔径范围I的影响更加明显;整个孔径范围的分形维数不宜用于分析渗透性,而应针对与渗透性相关的孔径小于临界孔径的范围进行分形,得到的分形维数能有效用于计算渗透系数,随石灰石粉掺量增加,该分形维数越大,渗透系数越大,且与渗透性有着良好的相关性.

The pore structure of cement mortars with ground limestone and improvement of ground slag by calculating the evaporable water in this paper. The results show that, the ground limestone and ground slag content had less effect on the initial porosity of cementitious material. With the increasing ground limestone content, the total porosity, macroporous porosity and proportion of mortars with 10％ ground limestone were smallest at the age of 7 days while the microporous porosity and proportion reached the maximum. At the age of 28 days, the total, macroporous and microporous porosity of mortars increased, while the microporous proportion decreased. With the increase of ground slag content, the total porosity, macroporous and microporous porosity of cement-limestone mortar decreased on the 7th and 28th day, and the proportion of small pores increased.

Ground marble and dolomite were chosen as the materials to test the particle size distribution under different grinding time,and the Blaine specific surface area was calculated.The characteristic particle size,uniformity coefficient and specific surface area were determined by means of grinding dynamics and linear regression analysis using Rosin-Rammler-Bermet (RRB) equation as the particle size distribution model.The results show that with the increase of grinding time,the number of the particles in the range of 0～10 μm gradually increases,the number of particles larger than 10 μm gradually decreases.The grinding efficiency decrease gradually with the time,and ground marble has a higher grinding efficiency than ground dolomite at the same time.The uniformity coefficient of ground marble increases,and the particle concentration phenomenon enhances,however,the uniformity coefficient of ground dolomite decreases,and the particle concentration phenomenon weakens.There exist logarithmic and double logarithmic correlations between the specific surface area and characteristic particle diameter of the two particles.

The variation of rheological parameters with hydration time for the cement-ground limestone paste was studied and the rheology of cement-ground limestone paste was measured through the rotational viscometer of RHEORIAB QC type, the related rheological parameters was obtained by fitting paste rheological curve based on Herschel-Bulkley model. Dynamic yield stress and consistence of cement-ground limestone paste were fitted respectively by models proposed by Roussel and Philippe. The results show that the dynamic yield stress of cement paste is smaller than ground limestone paste, while the consistency is larger. The dynamic yield stress and consistency of cement-ground limestone paste linearly increase with hydration time; the increasing rate of the dynamic yield stress and consistency linearly decrease with the increasing mixing amount of ground limestone, and the initial dynamic yield stress linearly increase, while the consistency increases at first then decreases and presents a quadratic parabolic law.

Effects of ground limestone fineness on cement pastes were studied and the theological properties of cement-ground limestone pastes were determined through the rotating viscometer.The related rheological parameters were obtained by fitting paste rheological curves based on Herschel-Bulkley model.The results show that new building energy and consistency decreases with the growth of ground limestone fineness,while dynamic yield stress increases at the same time.The growth of ground limestone fineness reduces the thixotropy of cement paste and slows the progression,and promotes the instantaneous structure recovery capability of cement paste.New building energy of cement-ground limestone pastes decreases with test time,while consistency and dynamic yield stress increase.