Establishing a similarity relationship for chloride ingress in concrete between simulated laboratory and real sea exposure tests is crucial for predicting the long-term durability of concrete structures using short-term monitoring. This study collected 150 real-sea exposure datasets and 300 laboratory simulation datasets from domestic and foreign literature. Utilizing the Markov Chain Monte Carlo (MCMC) method and Bayesian theory, probabilistic prediction models of the surface chloride concentration (Cs) and the apparent chloride diffusion coefficient (Dapp) were developed. Furthermore, a similarity coefficient was introduced to analyze the linear relationship between these key parameters in the two environments. Ultimately, an environment-time similarity probability model, which accounts for uncertainty, was established. This probabilistically-based similarity model for chloride ingress in marine concrete can effectively predict chloride distributions under real sea exposure, providing a reliable theoretical basis for assessing the long-term durability of concrete structures using short-term laboratory tests.

With the rapid growth of liquefied natural gas (LNG) infrastructure, the safety of storage and transportation systems faces increasing threats from cryogenic leakage-induced damage. To address this critical safety concern, a multiphysics simulation framework is proposed capable of evaluating the micro/meso-level degradation behavior of LNG storage tanks under ultra-low temperatures (-162 degrees C). A novel peridynamics (PD)-based micro/ meso-level model is developed and experimentally validated using cryogenic beam fracture tests, enabling the simulation of coupled thermal-hydraulic-damage responses, pore water crystallization, and crack propagation. The model incorporates a coupled formulation of temperature-driven phase transition, moisture transport, and crystallization-induced damage, along with a multiscale scheme to capture temperature-dependent variations in elastic modulus and strength. The PD simulations effectively reproduce brittle fracture patterns observed at low temperatures, revealing pronounced brittleness below-60 degrees C for concrete (w/c 0.4-0.8) and localized damage in interfacial transition zones and pore clusters. Beam fracture simulations across a temperature range from-80 degrees C to 20 degrees C exhibit strong agreement with experimental results, confirming the model's reliability in capturing both strength loss and fracture evolution. Full-scale leakage scenarios predict thermal penetration depths of 0.57 m/day and complete wall freezing within 2.5 days, with critical risk zones identified at LNG impingement regions, liquid accumulation areas, and annular base zones. This simulation method provides a validated and comprehensive safety assessment tool for LNG containment systems, offering new insights into damage mechanisms and supporting safer design and operation of cryogenic energy infrastructure.

Engineered geopolymer composites (EGC) made from industrial solid wastes, such as fly ash (FA) and ground granulated blast-furnace slag (GGBS), are a sustainable alternative to traditional cement-based composites. The incorporation of polyethylene (PE) fibres can significantly improve the uniaxial tensile behaviour of EGC, while the tensile performance may be strongly influenced by matrix rheology. Nevertheless, the relationship between matrix rheology, macroscopic mechanical behaviour and microstructure remains insufficiently understood. This study systematically investigates the effects of precursor combination ratio (FA/GGBS), activator modulus (Ms) and sand-to-precursor ratio (S/P) on the matrix rheological properties, compressive strength, uniaxial tensile behaviour, fibre distribution and pore structure of PE fibre-reinforced EGC. The effects of various ranges of matrix rheological properties on the compressive strength, tensile properties, fibre distribution coefficient, pore size and pore shape of EGC were explored. Results indicated that the mixture containing 70 % FA, a Ms of 1.5 and an S/P of 20 % exhibited the most robust tensile strain-hardening behaviour. The compressive strength, tensile strength and tensile strain capacity of this optimal mix were increased by 33.8-350 %, 9.4-127.5 % and 132.2-518.1 %, respectively, compared with mixes containing lower FA contents, lower Ms and higher S/P. Maintaining matrix flowability within 250-260 mm, dynamic yield stress within 25-35 Pa and plastic viscosity within 15-25 Pa·s was found to be conducive to the development of an optimised pore structure, improved fibre dispersion, and enhanced fibre bridging behaviour in EGC, thereby leading to higher compressive strength and more robust tensile strain-hardening behaviour.

Using construction waste to prepare pervious concrete provides a low-carbon route for developing sponge cities. However, the complex constituents lead to a technical bottleneck in controlling fresh properties of paste. By regulating the paste film thickness (PFT) of recycled micropowder-ground granulated blast furnace slag-cement (RSC) paste, this study prepares recycled aggregate concrete with balanced strength and permeability (RSC-RAPC). Water reducer effects on flowability, PFT and rheology are investigated, establishing a PFT-performance relationship that is more applicable to aggregates of 4.75-9.5 mm. Compared with pure cement paste, RSC paste exhibits 17.1% higher PFT and 10% higher initial yield stress, while average fluidity decreases by 5.26%. Within a water reducer dosage of 0.11%, adjusting the PFT of the recycled aggregates in RSC paste from 0.20 mm to 0.57 mm yields RSC-RAPC with 13.5%-24.7% of connected porosity, 1.38-2.59 mm/s of permeability, and 6.1-28.8 MPa of 28-day compressive strength. Three interfacial transition zones are identified in RSC-RAPC, where the new paste-old paste interface exhibits 10.66% higher microhardness than the weakest interface due to carboaluminate reaction densification. A target porosity of 15%-17% is recommended, as it can maintain excellent permeability and mechanical strength while cutting both carbon emissions and economic costs per unit strength by over 43% and 45%, respectively.

Ballastless-track filling-layer repair requires rapid strength development, deformation compatibility, and environmental resistance. This study investigated sulphoaluminate cement-emulsified asphalt (SEA) mortar prepared with two cationic emulsions having nominal solid contents of 60% and 50% at A/C = 0–0.6, where A/C denotes the as-received emulsion-to-cement mass ratio. At a fixed A/C, changing solid content simultaneously changes the calculated nonvolatile-residue contribution and emulsion-introduced water, so the observed behavior reflects their coupled influence. As A/C increased from 0 to 0.6, the 28-day compressive strength decreased from approximately 68 MPa to below 10 MPa, and the dynamic elastic modulus decreased from approximately 12 GPa to 4 GPa. For the 60% solid-content emulsion (EA-A), the integrated mercury-intruded volume increased from 0.113 to 0.245 mL/g and D50 increased from 17.7 to 332.5 nm, indicating substantial coarsening of accessible pore entries. Higher A/C improved relative retention under low-high temperature and wet-dry cycling and reduced the chloride migration coefficient by up to 47.4%, but the high-A/C mixtures retained much lower absolute strength and stiffness. At the same A/C, EA-A generally exhibited a better balance of mechanical and environmental performance than the 50% solid-content emulsion (EA-B), consistent with more nonvolatile residue and less emulsion water. SEM and XRD observations linked the exposure-related strength evolution with phase precipitation, local cracking, and interfacial changes. Considering strength, stiffness, shrinkage, and environmental retention together, EA-A with A/C = 0.2–0.4 is proposed as a preliminary composition window, whereas A/C = 0.6 is not recommended for applications requiring high support capacity.

The unprecedented consumption of river sand by the construction industry has intensified the global sand shortage, creating an urgent need for viable alternatives. In this study, waste-based supersulfated (SSC) fine aggregates were fabricated by twin-roller compaction. The process achieved a maximum production capacity of 1.032 t/h, while the highest sieving yield was 92%. The aggregates were evaluated in terms of physical properties, mechanical reliability, hydration characteristics, pore structure and environmental safety, and were subsequently used to prepare high-performance concrete (HPC). The physical and mechanical performance, aggregate distribution and interfacial transition zone (ITZ) characteristics of the resulting HPC were then examined. AFt and C-(A)-S-H gels were identified as the primary hydration products. Decreasing aggregate particle size improved compactness and hydration degree while refining the pore structure. HPC containing SSC aggregates achieved a compressive strength of 78.1 MPa and a reduced drying shrinkage of 399.7 με. These performance advantages were associated with uniform aggregate dispersion, physical filling and enhanced ITZ characteristics. Overall, the efficient production and favourable performance of waste-based SSC aggregates demonstrate their broad potential as a sustainable fine aggregate for HPC.

Steel protective coatings are commonly used to enhance the durability of reinforced concrete (RC) structures. However, conventional coatings can inadvertently accelerate localized corrosion through galvanic effects at micro-defect sites. To address this critical limitation, self-healing coatings capable of autonomous defect repair are urgently needed. This study developed a novel self-healing 8-hydroxyquinoline-functionalized MgAl layered double hydroxide (8HQ@MgAl LDH) film through hydrothermal synthesis and alkaline-induced restructuring. This innovative design integrates 8HQ--intercalated LDH layers for inhibitor storage with epitaxially grown Mg (HQ)(2) crystalline barriers, formed through Mg2+ coordination. Electrochemical impedance spectroscopy analysis of the chloride-contaminated simulated concrete pore solution demonstrated exceptional performance, revealing fivefold higher low-frequency impedance than conventional LDH after 15 days. Artificial scratch tests demonstrated autonomous healing capability, maintaining electrochemical stability (<5 % impedance fluctuation over 96 h) while forming a regenerated barrier enriched with corrosion-inhibiting elements. The atomic-scale mechanism was further investigated using molecular dynamics simulations, which revealed that 8HQ- anions formed interfacial clusters through bidentate coordination with Fe3 + and Ca2+, thus effectively blocking Cladsorption.

The global quarrying industry generates hundreds of million tons of stone powder annually, posing significant environmental challenges. This study systematically evaluates the feasibility of incorporating four distinct stone powder types including silicate-based basalt and granite, as well as carbonate-based marble and limestone, as high-volume cement replacements (20-60 vol%) in ultra-high performance concrete (UHPC). Results demonstrate that while all powders acted primarily as inert fillers, their distinct physical characteristics differentially influenced performance. BP maximized packing density but decreased water film thickness (WFT) due to its high specific surface area, whereas MP and LP offered a balanced enhancement in both packing and workability (maximum 25.3% slump flow increase). Although the dilution effect retarded early-age hydration and reduced early strength, the optimized particle packing density compensated for this at later ages. Consequently, the reduction in 28-day compressive strength for all mixtures was limited to less than 7% at a 20% replacement level and remained below 15% even at a 40% replacement level. Microstructural refinement, notably in GP and MP mixes, reduced porosity and improved chloride resistance by up to 22.6%. Crucially, stone powder incorporation reduced CO2 emissions by up to 53% and decreased the binder and carbon intensity indices by 55% and 48%, respectively. This study provides a basis for selecting diverse waste stone powders to produce sustainable, low-carbon UHPC that maintains satisfactory mechanical performance and excellent durability.

Enhancing the reactivity of highly crystalline T-O-T clays such as muscovite remains a bottleneck for alkaliactivated binders. This work compares thermal treatment (T), mechanochemical activation (MCA), and their sequences-calcination followed by MCA (T-MCA) and MCA followed by calcination (MCA-T)-to establish how activation order governs structure-reactivity-performance. Integrated multi-scale characterization, supported by molecular dynamics, shows that T induces dehydroxylation with limited framework disruption, whereas MCA generates defects and particle refinement without removing long-range order. In contrast, T-MCA produces extensive loss of periodicity and a higher density of accessible reactive sites, accelerates early dissolution-polycondensation, and yields mixed N-A-S-H/K-A-S-H gels with superior early strength. MCA-T promotes the persistence of defects via layer collapse and local reorganization, thereby slowing reaction kinetics and yielding Na-dominated gels with limited strength. These findings position T-MCA as a practical route to convert muscovite into high-performance alkali-activated binders and geopolymers-particularly where conventional ashes or slags are scarce but muscovite resources are abundant-and provide design guidance linking layeredsilicate destabilization to reaction kinetics, gel assemblage, and mechanical performance.

Sluggish hydration kinetics of conventional Portland cement-asphalt mortars preclude their application in the strict 4-hour rapid rehabilitation of high-speed railway slab tracks. To overcome this, a novel viscoelastic sulphoaluminate cement-emulsified asphalt (SEA) mortar was developed. Synergistic regulation via borax, calcium formate, and polycarboxylate ether successfully decoupled the inherent conflict between workability retention and early-age strength, achieving a 4-hour compressive strength > 15 MPa. Macroscopically, escalating the asphalt-to-cement (A/C) ratio triggers a fundamental rigid-to-viscoelastic transition. While penalizing late-age strength and dynamic modulus, this shift profoundly enhances deformational compatibility and vibration-damping capacity. Microstructurally, demulsified asphalt forms a hydrophobic film encapsulating cement grains, driving a unique "physical retardation-delayed burst" hydration kinetic and macroscopic pore coarsening. Nevertheless, this flexible membrane mechanically interlocks with inorganic hydrates to construct a robust organic-inorganic interpenetrating network. Crucially, this topology dictates a durability trade-off: the hydrophobic film truncates capillary connectivity, drastically reducing chloride permeability, whereas pore coarsening compromises freeze-thaw resilience. Ultimately, this study establishes critical mix-optimization thresholds for rapid track repair and elucidates the microstructure-property-durability constitutive relationships of organic-inorganic composites.

Understanding the decalcification mechanism of calcium silicate hydrate (C-S-H) under marine environments is crucial for concrete durability. In this study, the decalcification behavior of C-S-H under a water-heat-salt environment was systematically investigated through immersion experiments and reactive molecular dynamics simulations. Experimental results showed that elevated temperature and NaCl solution significantly accelerated Ca leaching and reduced the Ca/Si ratio of C-S-H. Simulation results further revealed that both high temperature and NaCl reduce the dissolution free energy of Ca, making its release more thermodynamically and kinetically favorable. Local structure analysis indicated that Cl- disrupts Ca-Os (O atoms in silicate tetrahedra) connection through electrostatic attraction, while Na+ competes with Ca for silicate coordination sites. Elevated temperature further weakens the Ca-Os interactions and enhances the ion mobility. In contrast, the dissolution of Si atoms shows a clear energy barrier and requires higher energy due to strong Si-Os bonding. Based on these findings, an atomic-scale decalcification mechanism is proposed involving thermal activation, Cl- attraction, and Na+ competition, providing new insights into the degradation processes of C-S-H under the water-heat-salt environment.

To address the challenges of high annual production and low reactivity of different types of clay-bearing sludge, adopting pre-treatment technologies to enhance sludge reactivity for effective utilisation as construction materials is a promising sustainable approach. Given the complexity of sludge sources and compositions (e.g., clay minerals), it is crucial to apply pre-treatment strategies that are precisely tailored for sludge reactivity. This paper presents a comprehensive review of the effects of different pre-treatment approaches (mechanical, thermal, chemical, mechano-thermal and chemo-thermal) on the reactivity and physicochemical properties of raw sludge from sewage treatment plants, drinking water plants and dredging projects. The subsequent fresh properties, mechanical behaviour, durability and microstructure of cementitious and alkali/acid-activated materials after the incorporation of treated sludge are also critically reviewed. Regardless of sludge source, mechano-thermal pre-treatment has been mostly adopted to enhance the reactivity of sludge, where the raw sludge requires grinding to pass through a 200-mesh screen, followed by calcination at 600–800 °C for 1–2 h. This process transforms clay mineral phases (e.g., kaolinite, muscovite) within the sludge into amorphous phases. This review summarises recent advancements in applicable pre-treatment methods for various types of sludge and identifies the remaining challenges in developing sustainable high-performance sludge-derived materials for practical applications.

Phosphogypsum (PG), the industrial byproduct from phosphorus chemical production, consumes land resources while generating environmental contamination. Incorporating PG into supersulfated cement (SSC) constitutes a technically feasible approach. This study implemented the mechanochemical modification of PG and incorporated modified phosphogypsum (MPG) into high-alumina slag-based SSC. The performance of physical properties was assessed, and the microstructural evolution mechanisms governing aluminosilicate phase transformations were revealed. The results demonstrated that the 15% MPG-7.5% Ca(OH)2-77.5% slag formulation was optimal, demonstrating 53.8 MPa at 28-day curing, which exceeded natural gypsum-based SSC. The primary hydration products in SSC were C-(A)-S-H gel and AFt. At 15% dosage, MPG promoted aluminum leaching from slag, triggering the isomorphic substitution of Si4+ by Al3+ in the silicate networks and converting C-S-H to C-A-S-H while extending chain polymerization and enhancing the cross-linking density. At 15% dosage, more AFt and highly polymerized C-(A)-S-H with elevated aluminum content induced microstructural densification, manifested by the increased harmless porosity and reduced most probable pore diameter.

Vascular self-healing cementitious materials fabricated with pre-embedded pipelines have shown effective crack healing, but weak interfacial affinity between the channel wall material and the matrix often delays channel rupture and limits healing efficiency. In this study, we introduce an embedded 3D printing approach that generates wall-free vascular channels, followed by in-situ formation of channel walls through the controlled delivery of curable sealing agents. This method ensures strong bonding between channel walls and the matrix, enabling synchronous fracture and reliable healing activation. The approach meets key requirements for vascular self-healing systems, including isolation of healing agents, efficient activation, and freeform construction of three-dimensional transport networks. We systematically evaluated the sealing performance of the generated channel walls and their influence on matrix mechanical properties. The findings provide new insights into the design of vascular networks for self-healing concrete and offer a comprehensive strategy to enhance durability and functionality in cementitious materials.

Construction and demolition waste (CDW), an unavoidable byproduct of global urbanization, leads to environmental degradation and resource depletion. To address this challenge, a coldpressing method was utilized to transform multi-source construction waste recycled powder (MCWRP) into artificial aggregates for sustainable buildings. Ground granulated blast furnace slag (GGBS) was incorporated as a reactive micro-filler to enhance aggregate properties. The effects of varying cement and GGBS contents on cold-pressed MCWRP-based artificial aggregates (MCWAAs) were assessed through single-particle crushing strength, apparent density, and water absorption tests. Microstructural characterization was performed using X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS), and low-field nuclear magnetic resonance (LF-NMR). Results indicate that MCWAAs achieved a 28-day crushing strength of up to 3.3 MPa, an apparent density of 1882.3 kg/m3, and a water absorption rate of 10.8%, demonstrating their practical applicability. SEM analysis revealed that compaction pressure and hydration products densified the initially loose MCWRP structure. However, MCWAAs prepared with cement alone exhibited porous microstructures due to the coarse particle size of MCWRP. The incorporation of GGBS significantly refined the microstructure, reducing porosity to 11.48%. TGA and LF-NMR confirmed that higher GGBS content enhanced C-S-H gel formation, refined pore structure, and increased aggregate compactness. Consequently, MCWAAs exhibited improved strength and density with reduced water absorption, which offers a scalable, automated solution for the efficient reuse of CDW and other solid residues.

Current research on cement primarily focuses on macroscopic properties, yet microscopic aspects are equally crucial for understanding its complex behavior. To investigate cement at the mesoscale, a coarse-grained force field for cement materials is developed. In this study, a bottom-up approach was adopted to develop the coarse-grained field, where the structure and mechanical properties of the cement system were simulated using molecular dynamics (MD) and then reproduced in the coarse-grained model. First, the molecular model of cement is established, and the radial distribution function and Young's modulus of cement are obtained by MD simulation. The model is then coarse-grained into mesoscopic representations, and the force field parameters (sigma, epsilon, cutoff distance) of the Lennard-Jones potential (12-6) are determined through iterative coarse-grained dynamics and uniaxial tensile simulations. These parameters are applied to mesoscopic models with varying crack widths and filling rates, and stress-strain curves are obtained through uniaxial tensile tests. Results indicate that increased crack width reduces model strength, while higher particle filling rates enhance tensile strength. Mean-square displacement and radial distribution function analyses reveal that stronger interparticle interactions contribute to enhanced mechanical performance. Additionally, creep protocols elucidate the material's mechanical evolution pathway, capturing the progression from stable elastic response and time-dependent delayed yielding to rapid plastic densification under increasing external loads. This work establishes a robust and practical coarse-grained force field for cement using a straightforward methodology, laying the groundwork for future refinements and applications in mesoscale cement research.

Improving the accurate determination of the fracture energies in cementitious composites is highly significant for engineering practice. This research employed X-ray computed tomography (XCT) and digital volume correlation (DVC) to investigate fracture behavior in fiber-cement composites. In-situ XCT loading experiments were conducted for tracking failure progression, facilitating three-dimensional volume image reconstruction. The internal volumetric strains of the samples were calculated by DVC based on the volume images before and after deformation, enabling computation of deformation energies outside the fracture domains. The fracture energies of the samples were obtained after taking the deformation energy into account. The outcomes showed that the fracture energy will be overestimated by about 10 % (the value will increase for fiber reinforced materials) when the deformation energy is not considered.

Ultra-high performance geopolymer concrete (UHPGC) offers a promising low-carbon alternative to conventional ultra-high performance concrete (UHPC), whereas the underlying relationships between its microstructural features and macroscopic mechanical performance remain insufficiently understood, limiting further performance optimization. This study systematically investigated the effects of precursor composition (GGBS/SF) and steel fiber dosage on the microstructure evolution and mechanical properties of UHPGC. The correlations among pore structure, fiber orientation, and interfacial transition zone (ITZ) characteristics with macroscopic mechanical performance of UHPGC were elucidated through X-ray computed tomography (XCT), backscattered electron microscopy (BSEM), and nanoindentation analyses. Results revealed that the mixture containing 1.5-2.0 % steel fibers and a GGBS/SF ratio of 0.8/0.2 exhibited the optimal performance, achieving a compressive strength of 157.9 MPa, a tensile strength of 9.3 MPa, and pronounced strain-hardening behavior. Nanoindentation confirmed the continuous densification of the C(N)A-S-H gel network, while XCT analysis revealed a refined pore structure and uniform fiber distribution (distribution coefficient > 0.9). Furthermore, UHPGC achieved an 18-53 % reduction in carbon emissions compared with UHPC, demonstrating a significant sustainability advantage. This study elucidates the synergistic mechanisms among gel evolution, pore structure refinement, and fiber-matrix interfacial behavior, providing an effective pathway for developing next-generation high-performance and low-carbon geopolymer composites.

To address surface defects induced by the curing of waterborne epoxy resin (WEP) and its inherent hydrophilicity, this study developed a dense, hydrophobic composite coating for concrete using a two-step fabrication approach. In the first step, cellulose nanocrystals (CNC) modified with hexadecyltrimethoxysilane and tetraethyl orthosilicate were incorporated into the WEP matrix to enhance crosslink density and coating compactness. In the second step, nano-silica modified with hexadecyltrimethoxysilane and methyltrimethoxysilane of varying particle sizes (30 nm and 100 nm) was deposited onto the coating surface. This constructed a multi-scale hierarchical structure, minimizing the contact area with corrosive media. Experimental results demonstrate that the proposed coating significantly enhances the waterproofing and impermeability of concrete. The treated mortar specimens exhibited an extremely low chloride ion migration coefficient of 1.408 & times; 10-12 m2/s (approximately 5% of the control group) and a water absorption rate that is only 7% of that of the blank group. Additionally, the coating achieved a water contact angle of 150.3 degrees, accompanied by robust mechanical durability and chemical resistance. This study provides an effective strategy for enhancing the performance and applicability of waterborne epoxy coatings in concrete infrastructure protection.