This study systematically evaluated the influence of temperature rise inhibitor (TRI) on the early hydration behavior and mechanical performance of cementitious systems incorporating different supplementary cementitious materials (SCMs), including quartz, fly ash, and slag. Compressive strength tests showed that the 3-day order changed from slag > quartz > fly ash in the reference systems to quartz > slag > fly ash when 0.225% TRI was incorporated. This reversal indicates that, despite the higher intrinsic reactivity of slag, TRI imposed a stronger suppression on slag blended systems than on inert quartz blended systems. SEM observations further confirmed that TRI significantly reduced the C-S-H nucleation density on fly ash and slag surfaces, whereas quartz maintained relatively robust nucleation density. Our finding shows that TRI reshapes the early hydration behavior of blended cements by suppressing clinker hydration and weakening the nucleation-promoting effects of reactive SCMs such as fly ash and slag, whereas quartz, with minimal adsorption of TRI, remains largely unaffected.

Yodel is a widely applied model for predicting the static yield stress of cement paste. However, current research has primarily focused on unary paste, with limited investigation into the Yodel model of multi-component paste and yield stress prediction, and thus an in-depth study was conducted in this paper. Through an investigation of a cement-fly ash binary cement paste, the methods for determining the percolation threshold, particle size distribution and interparticle forces parameters within the multi-component Yodel model were proposed. Based on this foundation, a prediction model of multi-component paste yield stress related to particle surface area was proposed. The mean absolute percentage error of prediction results was almost below 10 %. Furthermore, the quantitative relationships among various parameters between unary and multi-component Yodel models were developed, including the percolation threshold, packing density, particle size distribution and interparticle force parameters, and the quantitative relationships of these parameters between unary and multi-component paste were established.

Electrically conductive concrete shows considerable potential for snow and ice melting, yet the durability of conductive systems incorporating red mud under cold and salt exposure has not been systematically elucidated. This study investigates the coupled mechanical-electrical degradation of conductive concrete containing red mud, steel fibers, and copper powder under separate freeze-thaw and sulfate wet-dry cycling. After 100 freeze-thaw cycles, mass loss ranged from 0.43‰ to 2.15‰ and surface porosity increased to 6.1-13.9%; flexural behavior was more sensitive to deterioration than compressive behavior, while resistivity generally increased initially and subsequently decreased. After 30 sulfate wetting-drying cycles, surface porosity reached 2.6-5.6% and compressive strength increased by 17-36%, whereas mean resistivity increased by 612.5% at 10% red mud replacement and mean capacitance decreased by 91.1% at 30% replacement. Under the present exposure protocols, sulfate wet-dry cycling therefore caused more persistent electrical degradation than freeze-thaw cycling. XRD and SEM analyses revealed a degradation sequence involving pore structure evolution, microcrack propagation, disruption of conductive pathways, and loss of interfacial polarization capacity. Among the tested mixtures, 20% red mud, 5% steel fibers, and a water-to-cement ratio of 0.38 provided the best overall balance of mechanical performance, electrical stability, and durability. These findings provide a multiscale basis for understanding asynchronous mechanical-electrical degradation and support the durable design of conductive concrete for transportation infrastructure exposed to cold and saline environments.

3D printed concrete (3DPC) holds significant potential for applications in extreme environments. Air-entraining agents (AEAs) can enhance the frost resistance of concrete in cold regions by introducing uniformly distributed small air-voids. However, in 3DPC, the use of viscosity-modifying agents (VMAs) and the unique printing process may adversely affect the characteristics of entrained air-voids. This study employs X-ray computed tomography (X-CT) to quantitatively characterize the evolution of air-void structures in AEA-modified 3DPC containing different VMAs across three critical manufacturing stages: before-printing, in-printing-nozzle and after-printing. The results reveal that the shear action of the screw rod effectively refines the air-void size distribution while increasing overall air-void volume fraction. Hydroxypropyl methyl cellulose (HPMC) effectively stabilizes small bubbles (< 500 mu m) during before-printing stage, increasing the air-voids count via a protective film that prevents rupture. Conversely, attapulgite leaves small bubbles vulnerable to break. However, during in-printing-nozzle and after-printing stage, attapulgite better protects large bubbles (> 1000 mu m), maintaining their shape against shear and elongation forces with a stable shell, while HPMC offers little protection, leading to more significant elongated bubble shapes. This study provides an experimental basis for regulating air-void structure in 3D printed air-entrained concrete from the perspective of materials selection and printing processes control.

Calcined kaolinite is a key component in limestone-calcined clay cement (LC3), enabling the replacement of highemission clinker through its high reactivity. However, the development of substitutes for calcined kaolinite is required due to the restricted availability of high-purity clay. In this study, calcined kaolinite tailing was used as a substitute for calcined clay to prepare LC3, while PVA fibers were incorporated to enhance toughness. The results show that the incorporation of calcined kaolinite tailing and limestone increases the 28-day tensile strength of the matrix by 30.6 %. Although the incorporation of 2.0 % PVA fibers by volume results in a marginal increase in the 28-day tensile strength of LC3, it leads to a marked increase in ductility from 0.025 % to 2.29 %. The higher plastic viscosity of the LC3 mixture reduces fiber agglomeration, resulting in a 12.1 % increase in fiber dispersion coefficient. The pozzolanic reactions reduce the content of calcium hydroxide in the fiber-LC3 matrix interfacial transition zones (ITZ) and strengthen the interfacial adhesion. However, the chemical bonding energy between fibers and LC3 matrix decreases by 42.6 % due to the increase in porosity within the ITZ. Furthermore, the numerical model containing actual fiber inclination functions reveals that the superior bonding properties of PVA fibers embedded in the LC3 matrix during slip-hardening enhance the crack control and stress transfer capabilities of PVA fibers. This study provides valuable insights for understanding the distinct reinforcement effectiveness of PVA fibers in LC3 and PC systems.

The surface color uniformity of fair-faced concrete is critical for architectural aesthetics but remains challenging to control, especially when high fluidity is required for workability. This study systematically investigates the mechanism of color deviation in high-fluidity cement paste (300-350 mm) by linking macroscopic appearance to microscopic phase segregation. The key innovation is the identification of a critical flowability threshold (∼330 mm), beyond which gravity-driven phase separation becomes dominant. Multi-scale characterization techniques (image greyscale, XRD, SEM, and X-CT) reveal that exceeding this threshold reduces the paste's yield stress, allowing denser clinker particles (e.g., C4AF, C3S) to settle while lighter phases (gypsum, ettringite, free water) accumulate in the upper region. For the first time, X-CT visualization directly shows the formation of interconnected bleeding channels (>1000 μm) in the high-fluidity paste, facilitating this segregation. Quantitatively, when fluidity increases from 300 mm to 350 mm, capillary porosity in the bottom region drastically decreases from 2.00% to 0.58%, whereas the top region retains higher porosity. Furthermore, mineral admixtures (FACs, LS, SF) are found to mitigate color deviation, likely due to optimized particle packing and higher adsorption of free water. These findings provide a rheological and microstructural basis for controlling concrete surface color by maintaining paste's fluidity below the identified threshold (330 mm) and incorporating appropriate mineral admixtures, thereby achieving an improved balance between workability and aesthetic quality.

Temperature-rise inhibitor (TRI) reduces heat evolution by modulating early-age cement hydration; yet the extent to which these early hydration kinetic perturbations propagate to long-term hydration and performance remains unclear, particularly in cements blended with supplementary cementitious materials (SCMs). This study examines the long-term evolution of compressive strength, hydration, and microstructural development in TRImodified systems incorporating quartz, fly ash, or slag. TRI imposes a transient suppression of early hydration but does not materially change the ultimate degree of hydration of either clinker or SCMs. Compressive strength development depends strongly on TRI dosage, SCM type, and replacement level. At 360 days, the compressive strength shortfall is confined to high-replacement blends with low-reactivity SCMs: quartz- and fly-ash-blended systems remain up to similar to 15% below the reference samples, whereas slag-blended systems are broadly comparable to the REF. Pore-structure analyses indicate that TRI-induced delays hinder early pore refinement, increase the macropore fraction, and thereby lead to the observed compressive strength loss.

Nano-engineered cementitious materials (NECMs) integrated with superior mechanical performances, enhanced durability and multifunctionality, are represented as the next-generation infrastructure materials. Nevertheless, a considerable gap remains between laboratory-scale investigation and industrial-scale implementation of NECMs. This review aims to provide a comprehensive understanding of NECMs performances with the objective of elucidating their potential for practical application. Firstly, the production and dispersion of nanomaterials are systematically reviewed, which primarily govern the cost and industrial feasibility of NECMs. Afterwards, the progress of the research on the hydration kinetics, microstructure, mechanical performance, durability and functionalities of NECMs is analyzed and summarized. In addition, representative case studies of NECMs in structural, industrial and large-scale applications are presented to illustrate the potential prospects for the development of NECMs. Through the comprehensive evaluation of NECMs, this review aims to offer valuable insights to guide both academic research and practical implementation, promoting the sustainable and large-scale application of NECMs in modern construction.

The stability of air bubbles is a critical factor in determining the performance of concrete. This study investigated the influence of various supplementary cementing materials (SCMs), with a 20

Due to the inferior properties of recycled aggregates (RAs), recycled aggregate concrete (RAC) is rarely utilized in important construction projects. While numerous methods have been employed to enhance the properties of RAs, these treatment methods often require substantial labor and material resources, limiting their widespread application in engineering projects. This study proposes a combined adjustable cement slurry coating and mixing approach (CSCM) to enhance the properties of RAC. In CSCM, the influence of the variable saturation degree (Sd) of RAs on the aggregate water absorption/desorption behavior is considered, and the mixing water is divided into two stages based on the Sd of the RAs. The impact of CSCM on the properties of RAC and variable Sd of RAs on the efficiency of CSCM were evaluated. Additionally, the mechanism of compressive strength enhancement by CSCM was further explored through the micro-mechanical properties and distribution of hydration products in the interfacial transition zones. Experimental results indicate that CSCM significantly improves the compressive strength of RAC when compared to the normal mixing approach. This improvement in strength is attributed to the CSCM's "nailing effect", which strengthens the bond between aggregates and new mortar. Moreover, maintaining the aggregate Sd at a relatively low level (e.g., lower than 50 %) is crucial for the application of CSCM. In this case, a formula has been developed to optimize the efficiency of CSCM in enhancing the compressive strength of RAC, which can be adjusted based on variations in aggregate Sd. The proposed CSCM provides a straightforward and effective method for enhancing RAC properties, offering considerable potential for practical engineering applications.

The present paper investigates the impact of calcium hydroxide (CH) and temperature on the reactivity of silica fume, and its binary mixtures by formulating the SCM-CH-systems containing KOH and K2SO4. The reactivity assessment of both individual SCM and blended SCMs can be obtained through heat of hydration, bound water, as well as CH consumption. Results indicates that an increase in CH content primarily extends the continuous reaction of SCMs and enhances the ultimate degree of reaction. However, a rise in temperature significantly expedites the reaction of SCMs, especially for silica fume, which has the highest activation energy. Furthermore, silica fume competes with fly ash or slag in blended SCMs system, and the competitive reaction is exacerbated by higher temperature and lower CH. In the early age, fly ash inhibits the reaction of its own and silica fume by absorbing Ca2 +, and the dissolution of slag is limited by Ca2+. In the later age, the reaction of silica fume with CH dominates and thus greatly inhibits the reaction of fly ash, which leads to a slight decrease in the overall reaction degree of SCMs with excessive CH and a significantly increase with limited CH.

Replacing cement with calcined clay and limestone powder supports sustainability and carbon reduction in LC3, but the variability of raw materials complicates balancing strength and toughness in concrete. In this paper, the effect of in situ polymerization of acrylamide on LC3 concrete performance is investigated. The reaction mechanisms of cement hydration and polymerization can be characterized using nano-microstructure techniques such as SEM, MIP, and nanoindentation. The results show that there is a chemical bond formed between acrylamide and cations, including calcium and aluminum, leading to the strong bonding effect between hydration products. Besides, the organic film formed by acrylamide polymerization can bridge cracks, fill pores, and serve as a load-bearing interface, providing flexible stress linkage. Consequently, the flexural strength of concrete is significantly improved by 44 % after curing for 90 days. Furthermore, its fracture energy is greatly promoted by at least 100 %, which can provide a guide for the enhancement in the toughness of LC3 concrete.

The comprehensive utilization of non-hazardous industrial solid waste (NHISW) is a key focus of the circular economy. This paper argues that green technology innovation is a crucial factor in improving the comprehensive utilization rate of NHISW. Through theoretical analysis, an empirical study is conducted using a sample of 297 cities in China from 2003 to 2019. The study revealed that green technology innovation can significantly enhance the comprehensive utilization rate of the NHISW. This conclusion remains robust after conducting robustness tests and addressing endogeneity issues via two-stage least squares (2SLS) and the difference generalized method of moments (GMM) estimation. The heterogeneity analysis reveals that green technology innovation significantly boosts the comprehensive utilization of NHISW in the first stage of the environmental Kuznets curve, but its marginal effect decreases as the economy grows. Additionally, a higher proportion of the secondary sector negatively moderates this relationship. This study suggests that the government can strengthen policy support for green technology innovation and encourage the application of green technology to improve the comprehensive utilization rate of NHISW.

Temperature rise inhibitor (TRI) is an admixture designed to mitigate thermal cracking by effectively reducing the early hydration heat of cement. However, the interaction between TRI and supplementary cementitious materials (SCMs) remains inadequately understood. This study investigates the coupling effect of TRI and quartz (as an inert SCM) on cement hydration through calorimetry, pore solution analysis, and adsorption-dissolution experiments. The findings indicate that the depressing effect of TRI on cement hydration is weakened in the presence of quartz. Adsorption tests reveal that TRI preferentially adsorbs to cement particles rather than quartz, ruling out competitive adsorption as a contributing factor. Instead, the dilution effect of quartz slightly reduces the pH of the pore solution, which in turn slows the initial dissolution of TRI, thereby diminishing its depressing effect. Furthermore, the study confirms that TRI delays C3S and C3A hydration but does not inhibit long-term clinker reaction, with hydration degrees converging after 28 days. These insights enhance our understanding of SCMs' role in modulating TRI's performance and provide guidance for optimizing TRI application in modern concrete.

The Limestone Calcined Clay Cement (LC3) is a novel cementitious material based on clay materials, which can reduce carbon emission by up to 40 %. Considering the fact that clay is restricted to be directly used as construction materials in China, kaolin tailings, as one of industrial waste, might be a potential resource to make LC3. In this study calcined kaolin tailings (CKT) from Guangxi Province were blended with limestone as replacement of cement clinkers. The mechanical performance, hydration behavior, and microstructural evolution were investigated by various characterization methods. The results show that replacement of CKT and limestone enhances the long-term strength development, resulting in a comparable 28-day strength as pure Portland cement. The pozzolanic and synergistic reactions of CKT mainly occur after 3 days. The later formed AFm phases and C-A-S-H can further refine pore structure. When the replacement rate is over 30 %, the dissolved aluminum ions from CKT are more inclined to enter C-A-S-H rather than to form more AFm. At an equivalent gel-space ratio, CKT-limestone blended cements showed higher compressive strength than the reference cement and other blended cement reported in the literature, highlighting the potential of CKT-limestone systems as a low-carbon option for China.

Water inrush is a major disaster in civil infrastructures extensively located in geologically unstable and water-rich regions, which demand grouting hydrogels to expansively block geological fractures and to be robust against the impact of rushing water. However, the traditional strategy of reinforcing hydrogels via fixed crosslinking sites inevitably interferes with their swelling properties. In this study, physical entanglement is employed as a reinforcing strategy to prepare a mechanically robust super-absorptive hydrogel, aiming to address this challenging dilemma. A rate-dependent fixing-sliding effect is revealed to exist in physical entanglement-reinforced hydrogels by comprehensively analyzing the rheological, mechanical, and swelling properties. Under high-velocity external forces such as water stream impact, polymer chains are frozen to fix the physical entanglement sites, thereby strengthening the hydrogels; during relatively slower water absorption, polymer chains are movable to allow sliding, achieving a higher swelling ratio. Accordingly, the hydrogels exhibit robust mechanical compressive strength (> ∼7 MPa) and a remarkable swelling ratio (∼1663 g/g to 618 g/g), which can effectively plug gushing water (1 L/min) with only usage of 24 g in the model water inrush test device. This work presents a useful strategy to design hydrogels combining seemingly incompatible swelling and mechanical properties, providing insightful guidance for developing not only grouting hydrogels but also a wide range of robust yet super-absorptive polymer-based materials.

Recycled concrete powder (RCP) has a large amount of calcium carbonate, which suggests that it can be used to make limestone - calcined clay (CC) cement (LC3) system by replacing limestone powder. So that it can promote the recycling of construction demolition waste and reduce the requirement of the natural resource for LC3. In this study, the fresh and hardened properties of CC-RCP cement system were comprehensively characterized by varying the CC/RCP ratio and dosage, including rheological, mechanical properties, hydration products and pore structure. The results indicate that the addition of CC prolong the setting time, but the effect could be mitigated by the recombination of RCP. By comparing with RCP, CC had a less obvious effect on increasing viscosity, but it could improve the shear thickening behavior of paste. In the case of less total content of CC and RCP, a ratio of 1:1 CC/RCP was better for the development of long-term strength. Whereas, with the increasing of substitution, the mixtures with CC alone or blending with RCP in a 2:1 ratio achieved higher strength. The incorporating of CC and RCP could make the conversion of C4AH13 into hemicarboaluminate (Hc) and monocarboaluminate (Mc), and it resulted in a denser structure with more medium capillary pores and gel pores than that mixtures with CC only.

The combination of well-balanced mechanical performance, high transparency and appealing eco-friendly attributes endows poly(lactic acid) (PLA) with significantly potential for wide-ranging applications in high-value packaging sectors. However, effectively toughening PLA without compromising its transparency and stiffness remains a formidable challenge. In this study, we synthesized a series of graft copolymers by incorporating hydroxyl-functionalized linear low density polyethylene (LLDPEOH) and copolymers of cycloolefin (COCOH) as the main chain and PLA as the side chain, which were subsequently employed as novel toughening agents for commercial PLA. The achievement of high-performance PLA blends with a balanced combination of toughness, strength, and transparency can be realized through meticulous tuning of the structure and mass fraction of the blended graft copolymers. The maximum elongation at break for the PLA blends increased by about 50 times that of neat PLA, reaching up to 300 %. Furthermore, these materials retained their high strength (54 MPa) and excellent transparency (light transmittance up to 90 %). The excellent properties of PLA blends could be ascribed to the well-designed chain structure of the graft copolymer which leaded to and excellent compatibility with the PLA matrix and unique phase morphology. This work is significant in guiding the design and synthesis of graft copolymers as toughening agents for PLA, thereby expanding its application range in areas where high transparency and toughness are required.

Limestone calcined clay cement (LC3) is one kind of the low-carbon binder in the recent years, contributing significantly to sustainable construction practice. This paper investigated the possibility of using the recycled powder from waste concrete as a substitution for limestone in the LC3. The results show that the mixtures containing equal amount of recycled powder demonstrate comparable rheological and mechanical properties to those containing limestone. The drying shrinkage of mortar with 30% recycled powder was higher than the reference cement mortar, but the value at 90 ages decreased 18.75% with the combination of calcined clay. The increasing of the normalized heat evolution for LC3 mixes was resulted from the filler effects provided by finer recycled powder and its sequential hydration with calcined clay. Compared to hydrated LC3 with limestone, the hydrated ternary system with recycled powder exhibits decreased formation of hemi- and mono-carboaluminate. The findings of this paper suggest that recycled powder exhibits considerable promise as a substitute for limestone in the production of LC3 and promoting carbon capture, utilization and storage (CCUS) of cement industry.