Research on Basalt Fiber-Reinforced Cementitious Composites (BFCC) has garnered significant attention. However, the effectiveness of the Basalt Fiber (BF) mechanism is often constrained by fiber agglomeration and interfacial debonding induced by variations in Coarse Aggregate (CA) content. The synergistic mechanism between CA and BF in crack bridging and stress transfer remains an area requiring further investigation. This study aims to elucidate the influence mechanism of the synergistic interaction between CA and BF content on the mechanical properties of cementitious materials, thereby addressing the limited synergistic enhancement effect caused by changes in BF dispersion due to CA content variation. To reveal the mechanism of the synergistic effect of CA and BF contents on the mechanical behavior of cement-based materials, the bending evolution of BFCC containing CA (CA-BFCC) under different combinations of CA and BF contents was examined by carrying out a four-point bending experiment. The results indicate that the optimal synergistic effect of CA-BF is observed at the combination of CA-20 % and BF-2 %. Compared to the specimen without CA and BF, the flexural strength and flexural toughness of CA-BFCC are increased by 44.5 % and 192.1 %, respectively. The rigid skeleton structure constructed by CA is able to optimize the distribution of BF, allowing the fibers to anchor deeply into the cement matrix. Meanwhile, BF can effectively compensate for the defects in the transition zone of the CA-matrix interface through its crack bridging effect and interface slipping energy dissipation. However, excessive CA or BF is not conducive to energy dispersion and may directly affect the synergistic mechanism between the two. The achievements of this study established a theoretical basis for the synergistic mechanism between CA and BF, providing a solid foundation for optimizing the design of fiber cement-based materials.

Clay-cement slurry, as a widely used anti-seepage material, is prone to calcium leaching and deterioration when exposed to environmental water. The influence of microstructural and mineralogical evolution on the transport properties of clay-cement samples under leaching conditions remains to be investigated. In this paper, accelerated calcium leaching tests were conducted on clay-cement pastes. A variety of techniques, including XRD, SEM, and NMR, were used to characterize the microstructural and mineralogical changes in the leached samples. The effect of accelerated leaching on transport behavior was studied by measuring changes in the water permeability and calculating diffusivity. XRD and SEM analyses show that after 28 days, the characteristic peaks of portlandite and ettringite almost disappear, while C-S-H gel undergoes decalcification and decomposition, leading to an increase in pore number and a notable rise in pore size (up to 1.90 μm). NMR results indicate that total porosity and peak pore size increase significantly, with the proportion of gel pores decreasing and that of small capillary pores (10-50 nm) rising from 10% to 22.1%. Moreover, the surface layer porosity (0-5 mm) increases from 31.33% to 50.65%, while the middle and lower layers show less degradation, indicating a progressive deterioration pattern. Regarding transport properties, the hydraulic conductivity increases from 4.7 × 10-10 cm/s to 2.14 × 10-8 cm/s (a two-order-of-magnitude increase), and the diffusion coefficient rises from 1.6 × 10-11 m2/s to 8.6 × 10-11 m2/s (a 5.3-fold increase). Both the diffusion coefficient and its increase factor gradually decrease from the surface to the interior, consistent with the evolution of porosity.

Reactive magnesia cement (RMC) captures CO2 through hydration and carbonation processes, offering significant potential for carbon reduction and broad application prospects. However, its low early-age strength and poor volume stability remain major challenges that limit large-scale application. Meanwhile, glass fiber-reinforced polymer (GFRP) offers high strength, lightweight, and excellent resistance to chlorides. To address these limitations, this study proposes a novel GFRP-encysted hollow composite structure and investigates its mechanical properties and microstructural evolution. Firstly, the carbonation effect on compressive strength, flexural strength, and carbonation depth of prism specimens is evaluated through a one surface carbonation test. Additionally, the intrinsic stress-strain responses and failure patterns of hollow cylinder specimens are examined. Furthermore, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) are employed to observe and track CO2-related products within the specimen. Thermogravimetric (TG) analysis is used to evaluate the pyrolytic behavior of carbonation products, while X-ray computed tomography (XCT) is applied to obtain the three-dimensional pore distribution in the specimen. The findings reveal that the compressive strength of the large opening specimen is increased by 79.17% at 28 days compared to the small opening specimen. This enhancement is attributed to hydrated magnesium carbonates (HCMs) produced from the carbonation of MgO, filling pores and microcracks within the specimen. These results establish connections between the compressive properties of hollow cylinders and their carbonation products, providing experimental data to support the combined application of RMC and GFRP in structural engineering.

Recycled brick aggregates (RBAs), a major component of construction and demolition waste (CDW), offer a sustainable alternative to natural coarse aggregates (NCA) by conserving resources and reducing landfill accumulation. However, its high porosity, weakly adhered mortar, and low strength restrict its structural applications. This study investigates a sustainable and cost-effective surface treatment method to enhance the inferior properties of RBAs using agricultural waste biomass ashes. Three types of pozzolanic slurries (sugarcane bagasse ash-cement (SBA-C), rice husk ash-cement (RHA-C), and corn cob ash-cement (CCA-C)) were formulated with a fixed proportion of 70 % agricultural waste ash and 30 % cement by mass. These slurries were prepared at varying water-to-binder (w/b) ratios of 2, 4, and 6 to optimize the treatment efficacy. The results showed that RBAs treated with various types of agricultural waste slurries exhibited 22.9-33.3 % reduction in water absorption, 2.3-8.5 % increase in particle density, 23.7-29.4 % improvement in crushing resistance, 16.9-20.6 % decrease in impact value, and 25.1-29.2 % enhancement in abrasion resistance, compared to untreated RBAs. Among the tested agricultural waste slurries with different w/b ratios, the RHA-C slurry with a w/b ratio of 2 showed the greatest improvement, followed by the SBA-C and CCA-C slurries. Mercury intrusion porosimetry (MIP) showed reduced harmful pores (>200 nm), while X-ray diffraction and scanning electron microscopy confirmed the formation of additional hydration products and surface densification, confirming microstructural enhancement in treated RBAs. Moreover, concrete prepared with treated RBAs showed superior mechanical and durability performance compared with untreated RBA concrete, while maintaining comparable cost and CO2 emissions to conventional concrete. Overall, this approach valorizes both CDW and agricultural waste, advancing circular economy principles and enabling more sustainable concrete production.

Concrete structures in China's plateau regions suffer severe thermal-fatigue degradation due to long-term large diurnal temperature gradients. The interfacial transition zone (ITZ), as the weakest link, governs such thermally induced damage, yet quantitative ITZ-targeted metrics remain unclear. To address this issue, a real-environment-informed accelerated test was developed to reveal how FA modulates ITZ evolution in ordinary Portland cement (OPC) and low-heat cement (LHC) with an ITZ nano-scratch depth/coefficient of friction (COF) detection, hardness population analysis, in-situ thermal-stress visualization, and layered image recognition of ITZ. Results reveal that thermal fatigue cycling (TFC) triggered a maximum 85.7% widening and a 20% COF rise in the ITZ of pure OPC after 1200 cycles, accompanied by decreased C-S-H density, increased porosity (maximum by 161%), and a concurrent 21% reduction in micro-hardness. Layered image analysis of ITZ porosity zones further quantified graded pore coarsening, with OPC exhibiting intensified porosity gradients (Delta del phi ITZ >0) and LHC showing gradient smoothing after TFC. FA behaves as a dual-function modifier for ITZ, serving as a stress diffuser or a hydration-induced micro-healing agent, depending on binder chemistry and dosage: in OPC systems, FA contributed to ITZ densification and bonding, whereas in LHC, it served as a filler to redistribute stress and delay localized fracture. Optimized dosages (<= 30%) refine ITZ porosity, disperse microcrack networks, and mitigate hardness loss, whereas excessive FA (>30%) creates weak interfacial regions accelerating degradation. Four coupled mechanisms were identified: (i) aggregate-paste thermal mismatch cracking; (ii) graded pore coarsening; (iii) C-S-H gel deterioration; and (iv) interfacial debonding. Moisture-exchange tests further validate the mechanism: <= 30% FA reduces mass loss by up to 1.5%, while LHC shows slightly higher loss (0.2%) than OPC. Finally, data-driven modeling using random forest regression identified ITZ width as the top predictor (VIM = 0.31) of strength evolution, establishing an exponential multiscale correlation between ITZ widening and macroscopic strength decay.

Fiber reinforced polymer (FRP) - engineered cementitious composite (ECC) has been considered an effective approach for externally reinforcing the reinforced concrete (RC) beam. Nonetheless, the premature debonding of FRP-ECC layer may impede the complete realization of its reinforcement efficacy, especially for scenarios of RC beam under shear. To address this issue, this study delves into characterizing the shear behavior of FRP-ECC reinforced RC beam with distinct shear span ratios (1.4, 2.2 and 3.0), uncovering the interfacial debonding mechanism through the coupled nondestructive digital image correlation (DIC) - image processing (IP) approach. Experimental outcomes demonstrate a notable enhancement (ranging from 0.4 % to 28.5 %) in the structural shear capacity when employing the FRP-ECC layer in comparison to the pristine beam, as the shear span ratio varies from 1.4 to 3.0. Concurrently, there is an increase in the shear force corresponding to concrete cracking (ranging from 16.3 % to 26.6 %) and steel yielding (ranging from 6.7 % to 24.8 %). These phenomena are attributed to the FRP-ECC layer's role in impeding crack propagation within the concrete. However, if the interfacial bond of FRP-ECC layer is surpassed at a local region, it may debond from the beam surface. In scenarios with higher shear span ratios, the FRP-ECC layer experiences greater shear contributions, leading to more pronounced debonding. For an RC beam featuring a shear span ratio of 3.0, the FRP-ECC system encounters a debonding ratio of 41.08 %. The debonding mechanism related to FRP-ECC grid-reinforced concrete beams proposed in this study will provide significant reference value for analogous scenarios in future research and engineering applications.

Calcium leaching is a common deterioration phenomenon in hydraulic concrete structures, which leads to the decomposition and leaching of cementitious materials, increased porosity, elevated permeability coefficients, and reduced strength and durability, ultimately compromising service performance. Developing calcium leaching simulation methods holds significant application value for the long-term performance assessment and safety evaluation of hydraulic concrete structures. This paper reviews the key issues in the simulation of calcium leaching in cement-based materials, including the mechanisms of dissolution and models for the decomposition of calcium compounds. The basic assumptions and application conditions of existing models are summarized and critically discussed. For high concrete dams and large reservoirs subjected to long-term calcium leaching effects, further research is needed on the molecular dynamics-based simulation of the dissolution process in cement-based materials, the development of calcium analysis models under multi-factor coupling effects, and the life-cycle safety assessment of hydraulic concrete structures under calcium leaching.

The safe disposal of rubber waste by recycling it into concrete mixes as a partial replacement for sand offers environmental benefits, reduces construction costs, and conserves natural resources. The current study experimentally investigates the production of reinforced concrete (RC) beams with shear deficiencies, incorporating rubber as a partial sand replacement at volume fractions of 10

To meet the demanding conditions of marine environment, cementitious materials of concrete must exhibit low hydration heat, high strength, and superior erosion resistance. This study investigates the hydration and marine durability of high-ferrite Portland cement (HFPC)-fly ash blends under varied curing temperature. Its mineral composition, rich in C4AF and C2S, results in significantly slower and lower early-age heat release - only 86.7% of ordinary Portland cement at 3 days (20 degrees C). Fly ash slightly delays early hydration and reduces heat release of HFPC, but accelerates it after an initial inhibition period (similar to 12 h at 20 degrees C, similar to 6 h at 60 degrees C) through providing hydration product nucleation sites and dilution effects. Incorporating fly ash (40% being optimal) markedly refines pore structure and enhances chloride penetration resistance. HFPC-fly ash blends demonstrate excellent early durability in NaCl and Na2SO4 solutions, offering promising marine applications.

The integration of multi-material 3D printing with origami engineering offers a promising avenue for deployable structures, but weak interfacial bonding between rigid and flexible phases remains a key limitation. This study first proposed four distinct hinge designs (enclosed, interlaced, inserted, and interlocked) for Miura-ori architectures, and subsequently investigated their mechanical behaviors with further elucidation of stress-transfer efficiency and interfacial failure modes under static tensile or compressive loading. Research outcomes identified the 5.0 mm interlaced hinge as the optimal interface design, improving stress distribution at the rigid-flexible interface and suppressing premature debonding. Notably, the dominant failure mode shifted from interfacial separation to ductile fracture within a TPU elastomer. Further research proves that increasing the embedment depth of the interlaced hinge from 1.0 mm to 5.0 mm can significantly increase fracture elongation from 100.8% to 342.4% while maintaining a stable peak tensile strength of approximately 12.5 MPa. At the structural scale, dual-material printed Miura-ori architecture exhibits better mechanical performance than single-material printed spatial counterparts (5163 N vs. 4019 N in compressive capacity, 18.7 mm vs. 8.0 mm in fracture elongation). These findings provide valuable insights into high-performance deployable structure design based on multi-material additive manufacturing.

This study investigates and calculates the influence of realistic boundary conditions on the mechanical performance of frame short beams in a slab-on-beam reinforced concrete (RC) structure. Twelve frame short beams, with spatial location and longitudinal rebar ratio as experimental variables, were designed, constructed and tested under vertical loading, and their test results were compared with those of four simply supported beams. The experimental results showed that realistic boundary conditions enhanced the load capacity of short beams but compromised the ductility, resulting in more evident shear failure characteristics. Frame short beams developed significant elongation even under monotonic vertical loading. Then, a numerical model was established to further investigate the behavior of frame short beams and slabs. The results showed that the distribution of axial compressive force became uniform along the beam span when the cross-section of frame short beams included a certain width of flanges from slabs. Therefore, a frame short beam could be treated as an axially restrained individual component with a certain width of flanges. The slab portions outside the flange width acted as a source of external axial restraint. Finally, a calculation method was proposed for the load capacity of restrained short beams, which showed greater accuracy than the existing methods.

Porous concrete prepared with recycled brick–concrete aggregate (RBCA) is a promising material for ecological slope protection and permeable infrastructure because of its high connected porosity and potential for construction-waste recycling. However, its open pore network and the high water absorption of RBCA make it highly vulnerable to freeze–thaw deterioration, particularly in cold-region water-level fluctuation zones. This study investigated the freeze–thaw damage evolution and service-life prediction of RBCA porous concrete under dry, partially immersed and fully immersed conditions. Specimens were subjected to up to 45 freeze–thaw cycles, and their mass loss, compressive strength, pore-structure evolution and cracking behavior were characterized using mechanical testing, X-ray computed tomography (XCT) and acoustic emission (AE) monitoring. The results showed that immersion condition strongly controlled the deterioration process. After 45 cycles, the compressive strength loss reached 24.5%, 42.0% and 55.0% under dry, partially immersed and fully immersed conditions, respectively, indicating that increased water participation substantially accelerated damage accumulation. XCT results further revealed progressive pore coalescence and enlargement, with fully immersed specimens showing the most pronounced shift toward large connected pores. AE analysis indicated that freeze–thaw damage promoted earlier and more dispersed cracking during compression, while RA–AF results demonstrated a transition from interface-dominated shear damage to tensile cracking as the immersion degree increased. Based on pore-structure evolution, a porosity-based freeze–thaw damage factor was derived, and an immersion volume rate was introduced to quantify local damage under partially immersed conditions. A damage model incorporating cycle number and immersion volume rate was then established, achieving good agreement with experimental results with an R² of 0.98. The proposed framework provides a quantitative basis for durability assessment and service-life prediction of RBCA porous concrete used in cold-region ecological protection structures.

The limited crack control, ductility, and energy dissipation capacity of conventional reinforced cementitious thin plates under bending and cyclic loading remain a key challenge for structural applications. This study investigates the bending performance of engineered cementitious composite (ECC) thin plates reinforced with shape memory alloy wire mesh (SMAWM), steel wire mesh (STWM), and hybrid SMA-steel wire mesh configurations under monotonic and cyclic four-point bending loading. The objective is to evaluate the structural resilience and bending behavior of ECC thin plates reinforced with different wire mesh systems. Experimental and numerical approaches, including four-point bending tests, Digital Image Correlation (DIC), and finite element analysis, were used to evaluate load-deflection response, toughness, crack behavior, and self-centering performance. Steel wire mesh specimens achieved the highest peak load of 1190 N, whereas SMA wire mesh specimens exhibited superior ductility with a displacement of 45 mm but a lower peak load of 860 N. Hybrid reinforcement systems, such as SMAWM2-STWM2-1.0, showed balanced performance with a peak load of 1031 N and a displacement of 36.64 mm. DIC analysis revealed crack closure ratios of 54% for ECC, 10% for steel wire mesh, and 78% for SMA-reinforced specimens, while hybrid configurations improved crack control and recovery. Finite element simulations agreed well with experimental results and confirmed that hybrid reinforcement improves stress distribution and crack resistance. These findings highlight the potential of hybrid SMA-steel reinforcement for enhancing the strength, ductility, and resilience of ECC structural elements under bending and cyclic loading.

Cementitious materials can deteriorate under thermal cycling (TC) above the freezing point even though no ice-related bulk phase transition occurs, which points to moisture behavior as a likely driver of damage, yet its specific contribution remains unclear. To isolate this contribution, we developed a field-temperature-referenced accelerated TC regime (5–45 °C, 3 h/cycle) and applied it to white Portland cement (WPC) paste preconditioned to controlled internal relative humidity (RH) levels of 10–99% and tested under either sealed or free-exchange boundary conditions, so that the internal moisture state and boundary-controlled moisture exchange could be separated. Under sealed conditions, UPV loss grew with internal RH, from 3.89% (S10) to 8.62% (S99), despite negligible net mass change. Standardized multiscale indicators revealed an RH-dependent transition in the governing mechanism: drier specimens were controlled by capillary suction and pore coarsening, whereas wetter specimens underwent cyclic moisture redistribution, accumulated short-T2 water (interlayer and gel water), and developed localized microcracking within a densifying matrix. 1H NMR confirmed that this redistribution was only partly reversible, leaving a residual shift toward short-T2 components, and the calculated calcium-silicate-hydrate (C-S-H) interlayer spacing evolved toward about 0.76 nm regardless of the initial state. Allowing free moisture exchange changed the mechanism rather than merely intensifying it: F99 showed the largest UPV loss (19.4%), together with stronger crack connectivity, pronounced strain localization (μεxx = −2.25, μεyy = −4.76), and intensified carbonation, signaling a coupled moisture transport–carbonation–fracture pathway. On this basis, a tri-component thermo-hygro damage model was formulated to apportion UPV-based deterioration among intrinsic thermal fatigue, RH-dependent amplification, and boundary-controlled moisture exchange. The results establish, at the matrix scale, that internal moisture state and boundary exchange—not net drying—govern the severity and the mode of TC-induced damage in cement paste.

Calcium leaching increases the hydraulic concrete material's porosity and the diffusion coefficient, thereby jeopardizing engineering safety. Fly ash and silica fume are commonly used mineral admixtures in hydraulic concrete, and their effects on the material's leaching characteristics, especially its microstructural and transport properties, require further investigation. In this study, calcium leaching tests were conducted on cement paste (CP), silica fume-cement paste (SF), and fly ash-cement paste (FA) using a 6 mol/L ammonium chloride solution to accelerate the leaching process. Subsequently, a series of quantitative and qualitative analyses was performed on the deteriorated specimens, including phenolphthalein indicator spraying, X-ray diffraction (XRD), nuclear magnetic resonance (NMR), and scanning electron microscopy (SEM). Additionally, the diffusion coefficients of the material at different locations were calculated and analyzed. The results show that partially replacing cement with silica fume or fly ash increases the initial porosity, gel pore content, and initial diffusion coefficients. After 28 days of leaching, compared to the initial values, the porosity increases in the 0-4 mm layer from the leached surface were 83.6% for CP, 11.0% for SF, and 39.0% for FA. The diffusion coefficients increased by factors of 14.3 (CP), 6.1 (SF), and 13.6 (FA), indicating enhanced resistance to leaching. The primary reason for this is that the reactive silica in the admixtures undergoes a pozzolanic reaction with the calcium hydroxide generated by cement hydration, producing additional calcium silicate hydrate (C-S-H) gel, which reduces the capillary pores that would otherwise result from calcium hydroxide decomposition.

Environmental thermal cycling (TC) is a common but often under-specified service action for concrete infrastructure exposed to daily or seasonal temperature variation, solar heating, moisture exchange, and restraint. Unlike freeze–thaw or high-temperature exposure, non-freezing TC causes gradual damage through coupled thermo-hygro-mechanical (THM) processes. This review summarizes the mechanisms, modeling methods, and mitigation strategies for non-freezing TC and re-analyses published data using shared exposure parameters. The compiled evidence shows that early strength gain may arise from continued hydration, crack filling, or capillary prestress, and should not be taken as evidence of long-term resistance. Later damage is mainly linked to interfacial transition zone (ITZ) mismatch, moisture-controlled rate effects, crack–pore connectivity development, and restrained thermal deformation. To improve cross-study comparison, a thermal-cycling action spectrum (TC-AS) is proposed to describe TC exposure beyond temperature amplitude and cycle number. A reduced severity index, STC, is then calibrated from endpoint data. For concrete systems, STC improves late-stage damage ordering from R2 ≈ 0.22 using temperature amplitude alone to R2 ≈ 0.75, with Q2 ≈ 0.41. However, it should currently be used as a within-class semi-empirical ordering variable rather than a general predictive model. Moisture boundary, amplitude, and internal water state are the dominant controls, while water-to-binder ratio (w/b) and supplementary cementitious material (SCM) dosage are material- and dosage-dependent. Existing models are reviewed from empirical indicators to coupled THM and mesoscale descriptions, and mitigation is discussed in terms of exposure reduction, pore–interface stabilization, and damage-tolerant repair. The review highlights the need for boundary-resolved testing and lab-to-field equivalence before TC assessment can support reliable service-life design.

Roller-compacted concrete (RCC) in dam construction has become popular in most areas of Tibet. The service environment and incorporation of high fly ash in RCC make it a big challenge of attaining balance between excellent freezing-thaw resistance and high strength. It is reported that the modified absorptive polymer (MAP) presents excellent freezing-thaw resistance in RCC. However, the influential mechanism of MAP in RCC is not clear. In this study, the cementitious materials (RCC, fly ash blended pastes, and mortars) incorporated with MAP are utilized. Working and mechanical performances of RCC are studied. Hydration and microstructure of blended pastes are investigated by many experimental tests (hydration heat test, electrical resistivity test, differential thermogravimetric test, nuclear magnetic resonance test, and nanoindentation test). Rheological and drying shrinkage of mortar are analyzed. It is found that MAP has no significant effect on the Vc value, air content, and apparent density of RCC. The incorporation of 0.3% by weight MAP2 significantly increases the compressive strength of RCC by up to 28.7%, but the effect on the splitting tensile strength is negligible. The incorporation of MAP has little effect on the rate of hydration of blended pastes, amount of chemically bound water and calcium hydroxide (CH). The incorporation of MAP in the blended paste is helpful to increase the average chain length (ACL) of C & horbar; S & horbar; H and content of high-density C & horbar; S & horbar; H (HD C & horbar; S & horbar; H) gel, concurrently impeding the migration of Al. Water absorption and release behaviors of MAP strongly affect the fluidity, yield stress, plastic viscosity and drying shrinkage of the mortar.

This study systematically examines the degradation of cement paste under accelerated leaching conditions using a combined multi-scale experimental and numerical simulation approach, aiming to connect nanoscale structural alterations to macroscale performance decline. Cement paste sheets were leached in 5 M NH4Cl solution (pH approximate to 4.5) for 7 d, 14 d, 28 d, and 56 d. The findings indicate a hierarchy of leaching resistance of cement hydration products: hydrotalcite > C-(A)-S-H > hydrogarnet > ettringite > portlandite, whereas clinker phases (C3S, C2S) are easier to decalcify than C-(A)-S-H. Comprehensive analyses elucidate the mechanisms of Al migration from C-(A)-S-H into Al-Si gel, emphasising the preferential transformation of Al-containing segments and the stabilization of Al primarily in tetrahedral coordination (Al-4). Analysis of pore structure shows that initial leaching mainly enlarges large pores (200-1000 nm) due to the dissolution of portlandite, while subsequent stages primarily increase gel pores (similar to 10 nm) as a consequence of C-(A)-S-H decalcification. Molecular simulations further illustrate that the deterioration of mechanical properties at the nanoscale is primarily influenced by the decrease in packing density rather than the reduction in the Ca/Si ratio. Furthermore, the increase in pore connectivity markedly increases permeability during leaching. This research offers integrated multi-scale insights that enhance the fundamental comprehension of cement paste durability under leaching conditions.

Cellulose ethers (CE) are extensively used as viscosity modifying admixtures in the cementitious materials. Scare attention was focused on the chloride transport in the CE-added cementitious materials, which significantly influences the service life of buildings in chloride-enriched environments. This work studied how CE affect the chloride transport in cement pastes and the underlying mechanisms. The chloride binding isotherm and natural chloride diffusion tests were executed to disclose the chloride transport in the CE-added cementitious system. The phase assemblage analysis was performed by X-ray diffraction analysis and thermogravimetric analysis, and microstructural properties were revealed using scanning electron microscopy and mercury intrusion porosimetry. Results suggest that adding CE increases the chloride binding capacity and decreases the chloride resistance in cement pastes in a dose-dependent manner. The decreased alkalinity in CE-added cement pastes is responsible for the increased chloride binding capacity by providing more adsorption sites for Cl- in the system. CE decrease the pore tortuosity and increase the porosity mainly by inducing capillary and large pores in cement pastes. By establishing relationships between the chloride diffusion coefficient and chloride binding capacity and pore structure parameters, it is found that the chloride transport in CE-added system primarily depends on the pore structure. Overall, CE increase the chloride diffusion coefficient of cement pastes. This work provides new understandings on the chloride transport in CE-added cementitious materials and theoretical support for further applying CE in cement-based materials, especially for those in chloride-enriched environments.

The bond performance at the interface between new and old concrete is critical for the repair and strengthening of concrete structures. This review systematically examines the core influencing factors and the resulting mechanical performance. The findings indicate that interface treatment through roughening methods is fundamental to ensuring bond quality, as it enhances mechanical interlock, often proving more effective than the sole use of bonding agents. Material modification, particularly the incorporation of ultra-high-performance concrete (UHPC), significantly improves the interfacial performance. The dense microstructure and high fiber content in UHPC effectively bridge micro-cracks, thereby substantially enhancing crack resistance, mitigating shrinkage, and increasing overall mechanical strength. Furthermore, the review underscores that optimal bond performance is achieved through the synergistic design of multiple factors, including surface roughness, bonding agents, fiber reinforcement, and curing regimes. Current research gaps are identified, particularly concerning the long-term durability under coupled environmental and mechanical loads, as well as the development of comprehensive theoretical models. Future research directions are briefly noted to address these challenges.