This study investigated the effects of bacteria, hollow fibers, and bacteria-loaded hollow fibers on the carbonation behavior, mechanical properties, microstructural evolution, and carbon sequestration efficiency of Steel Slag-Sea Sand Concrete (SS-SSC) under CO2 curing conditions. The results indicate that bacteria-loaded hollow fibers enhanced the functional persistence of bacteria and were associated with increased calcium carbonate formation under CO2 curing conditions. At a bacterial concentration of 2 & times; 106 CFU/mL and a fiber dosage of 1 kg/m3, SS-SSC exhibited the highest mechanical performance after 28 days of CO2 curing, with the compressive strength of the bacterial group, sisal fiber group, and polypropylene fiber group increasing by 19.96%, 16.35%, and 17.94%, respectively, compared to the control group. The bacteria-loaded hollow fibers group showed further improvements, achieving compressive strength, carbonation degree, and CO2 sequestration rate increases in the ranges of 25.9-30.3%, 17-20%, and 11.6-13.9%, respectively, indicating a synergistic enhancement effect. The Bacteria-loaded hollow fibers significantly reduced chloride ion migration after carbonation curing, demonstrating improved durability under chloride-rich conditions. Microstructural analyses (SEM, XRD, TGA, and NMR) showed that samples incorporating bacteria-loaded fibers exhibited higher CaCO3 and ettringite contents, a denser interfacial structure, and refined pore morphology, which corresponded with improved mechanical performance and CO2 sequestration capacity. This study provides a new technical pathway for bacterial mineralization and offers a promising approach for developing low-carbon and sustainable concrete materials.

Understanding the mechanical behavior of concrete in industrial environments is of critical importance for structural performance assessment and durability design. In this study, uniaxial compression tests were conducted on concrete subjected to the combined action of SO2 and CO2, and the failure modes, stress-strain responses, and energy evolution characteristics of concrete were systematically investigated. The results indicate that, prior to the peak stress, energy evolution is dominated by the accumulation of elastic strain energy, with limited dissipation. In the post-peak regime, the response is governed by the release of stored elastic strain energy, which is progressively converted into dissipated energy through mechanisms such as crack propagation and frictional heating. Under the combined SO2–CO2 action, the uniaxial compressive failure of concrete exhibits a distinct two-stage evolution. In the early stage, corrosion products fill internal pores, leading to a temporary enhancement in strength and elastic modulus, and resulting in a predominantly brittle failure mode. In the later stage, the accumulation of corrosion-induced damage reduces the load-carrying capacity, while the failure behavior remains characteristically brittle. After 72 days corrosion, the peak stress of the concrete decreased by 10.22%∼27.08%, accompanied by a corresponding reduction in peak strain ranging from 16.42% to 41.18%. Based on statistical damage theory, a corrosion-dependent damage variable was introduced to establish a uniaxial compressive damage constitutive model for concrete subjected to the combined SO2–CO2 action. The proposed model effectively captures the full stress-strain evolution of concrete.

Accurate prediction of the temperature field in high geothermal tunnels holds significant engineering value for ensuring the safety of tunnel construction and stability of long-term operation. The paper proposed a transient temperature field prediction model based on physics-informed neural network (PINN) for high geothermal tunnels, which can accurately predict the spatiotemporal distribution characteristics of the tunnel temperature field with only a small amount of monitoring data. Firstly, the physical mechanism of heat transfer in high geothermal tunnels was innovatively integrated into a deep learning framework, incorporating the residual block and hard boundary constraint operator to form a PINN model. Secondly, the PINN model was validated through the numerical simulation and physical model test. Ultimately, influencing elements of the tunnel temperature field were comprehensively analysed using the PINN model. The principal conclusions are as follows: (1) The proposed PINN model demonstrates high prediction accuracy. The absolute error between PINN and the finite element numerical solution is less than 0.6 degrees C, and the MAPE metric between PINN and the physical model test result is controlled within 2 %. (2) The MSE, RMSE, and MAPE of the PINN model are all smaller than those of the data-driven DNN model, indicating that the PINN model has better prediction accuracy and reliability. (3) Both the surrounding rock temperature and secondary lining temperature show an upward trend with rising initial rock temperature and ambient temperature, while demonstrating a downward trend with increasing return air speed. Through sensitivity analysis, it is found that the sensitivity of factors influencing the rock temperature at the radial distance r = 9m is as follows: initial rock temperature > ambient temperature > return air speed, and the sensitivity of factors affecting the secondary lining temperature is as follows: ambient temperature > initial rock temperature > return air speed.

Conventional corrosion inhibitors in cementitious systems often suffer from poor retention and low efficiency under chloride attack, limiting their long-term protective performance. Herein, a zeolitic imidazolate-modified layered double oxide (ZLO) was synthesized by in situ growth of ZIF-8 on layered double oxide (LDO) nanosheets. This modification enables targeted chloride capture and electrochemical self-repair in simulated concrete pore solutions (SCPs). ZLO exhibits a hierarchical porous structure with a high surface area and abundant active sites, significantly enhancing chloride adsorption capacity. Electrochemical tests demonstrated that ZLO reduced the corrosion current density and increased the polarization resistance, keeping the values below the critical threshold (0.1 mu A/cm2) over a 72 h cycle. Impedance analysis confirmed the stabilization of passive films and inhibition of charge transfer. Surface characterization revealed the accumulation of protective alpha-FeOOH and Fe3O4, which resulted from strong Fe2+-imidazolate coordination, forming a dense corrosion product protective film. Additionally, The imidazolate moieties further supported passive film regeneration, contributing to the selfhealing ability. The proposed ZLO strategy not only facilitates the development of multifunctional corrosion inhibitors but also offers promising potential for enhancing the long-term durability of reinforced concrete structures in marine environments.

The rapid industrialization has led to significant SO2 emissions, accompanied by high temperatures and humidity, causing severe deterioration of concrete. This study investigates the degradation of concrete by analyzing changes in pH value and SO42- concentration after 20-day coupled heat-moisture-SO2 exposure. It systematically examines the impacts of water-cement ratio, temperature, relative humidity (RH), and SO2 concentration on attack products and pore structure. The results indicated that SO2 ionized in the pore solution of concrete, releasing H+ and SO42- that reacted with cementitious phases such as Ca(OH)2, CSH, and calcium aluminate. These reactions decreased the pore-solution alkalinity and promoted the generation of ettringite and gypsum, with gypsum content significantly exceeding that of ettringite. Under saturated conditions, lower water-cement ratios, elevated temperatures, and higher SO2 concentrations increased gypsum content, expanded capillary and macropore volumes in the middle and later stages of attack, and accelerated the ion diffusion. The minimum pH and maximum SO42- concentration at 20 d were 3.52 and 29.90%, respectively. Notably, at 80% and 90% RH, the generation of gypsum was significantly reduced, which was merely 22.62% and 23.75% of those at 98% RH at 20 d, respectively. The proportion of large pores and overall porosity decreased, significantly impeding H+ and SO42- diffusion. Furthermore, predictive models for pH and SO42- concentration in concrete were developed by utilizing the GBR, XGBoost, RF algorithms. This study provides a theoretical framework for evaluating the durability of concrete structures situated within intricate industrial settings.

Abstract CO2 curing can greatly enhance the properties of concrete while actively sequestering CO2. However, the influencing mechanisms of CO2 curing on the passivation film of steel bars in concrete remains unclear. In this study, the passivation and depassivation behaviors of steel bars in CO2-cured mortar were investigated via electrochemical measurements, and the microscopic morphology and chemical composition of the passivation film were examined using scanning electron microscopy (SEM) equipped with energy-dispersive spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). The results demonstrate that CO2 curing can accelerate the passivation of steel bars, which can be attributed to the higher oxygen partial pressure around the steel bars when compared to standard curing. Although the thickness of passivation film on steel bars in CO2-cured specimens (4.06 nm) is less than that in standard-cured specimens (4.73 nm), the charge transfer resistance in CO2-cured specimens (458.54 kΩ·cm2) is higher than that in standard-cured specimens (384.49 kΩ·cm2). Specifically, the dense and ordered microstructure observed by SEM, together with the relatively high Fe2+/Fe3+ atomic ratio (0.90 vs. 0.63) of the passivation film detected by XPS, contributes to the enhanced electrochemical stability. In addition, it is found that CO2 curing significantly delays the depassivation onset of steel bars in mortar when subjected to chloride drying-wetting cycles, with the depassivation of standard-cured specimens initiating after 18 cycles and that of CO2-cured specimens being postponed to 30 cycles. Consequently, the protective performance of the passivation film in CO2-cured specimens surpasses that in standard-cured specimens despite the slightly thinner thickness.

The cooling effectiveness of single-head ventilation systems in high-temperature tunnels with multiple working faces is often insufficient, posing risks to both personnel and machinery. This study investigates the synergistic cooling mechanism between single-head ventilation and mechanical refrigeration through field monitoring, numerical simulations, and parametric analysis in a high geothermal tunnel. A three-dimensional coupled heat transfer model was developed to assess the effects of various parameters, including the refrigeration equipment output parameters (air temperature T-m: 5 similar to 25 degrees C, air volume V-m: 10 similar to 30 m(3)/s) and the relative positioning of the refrigeration equipment air duct and the main ventilation duct (their outlets distance L) on the tunnel cooling efficiency and temperature distribution. The model was validated using field data, with an absolute error <= 0.94 degrees C and a relative error <3%. Additionally, a polynomial regression model was used to predict the environmental temperature at the excavation face (T-a) based on Tm and V-m. Results show that: (1) Mechanical refrigeration reduced the average tunnel temperature by up to 7.0 degrees C (18.4%), with a maximum drop of 9.1 degrees C at the excavation face. (2) When the refrigeration equipment and main air duct outlets are aligned, the cooling effect at the excavation face is maximized. To optimize both the cooling efficiency and the temperature uniformity at the excavation face, it is recommended to connect the r refrigeration equipment air duct directly to the main ventilation duct. (3) The relationship between T-m, V-m, and T-a follows distinct trends: T-a increased linearly with T-m and decreased with V-m in a concave-down power-law fashion. (4) Considering both cooling effectiveness and economic efficiency, the output parameters of the refrigeration equipment are set to T-m = 18.8 degrees C and V-m = 30 m(3)/s, with the main ventilation air volume remaining unchanged.

The macro and micro textures of aggregates not only affect the internal structure and skid resistance of asphalt mixtures, but their surface structure evolution and abrasion mechanisms are of great research value in powder technology. The primary aim of this paper is to quantify how different abrasion methods affect the texture and resistance of aggregates. Through common abrasion tests using a modified Los Angeles Abrasion tester on limestone, basalt, 75# calcined bauxite and 88# calcined bauxite, limestone and 88# calcined bauxite were identified as the optimal combination for differential abrasion. Limestone and 88# calcined bauxite with different particle sizes were subjected to newly developed differential abrasion tests using a modified Los Angeles Abrasion tester. Their abrasion cycles, rate of mass loss, and texture changes were analysed in detail using the Aggregate Image Measurement System and a laser scanning confocal microscope. Results indicate that abrasion mode significantly influences abrasion rates and texture evolution of aggregates. Notably, differential abrasion notably affects limestone and 88# calcined bauxite differently, influencing their texture and surface roughness. Finally, a macro-micro texture correlation model of aggregates after differential abrasion was established. The study underscores differential abrasion's potential for enhancing long-term abrasion resistance.

To investigate the interfacial slip mechanics of ancient brick masonry subjected to hygrothermal environments, combined shear-compression tests were conducted on pre-conditioned triplet specimens. This study systematically analyzes the influence of hygrothermal cycle duration and pre-compression stress levels on failure modes, interfacial slip behavior, interfacial fracture energy, and dilatancy. Experimental results indicate that increasing pre-compression stress drives a transition in failure modes from pure interfacial detachment (Type I) to mortar joint failure (Type M). By enhancing interfacial frictional confinement and densification, pre-compression significantly augments ultimate shear strength and fracture energy while suppressing dilatancy during interfacial slip. Under hygrothermal cycling, damage morphology evolves from smooth interfacial fracture to rough internal mortar failure, accompanied by a general degradation in shear strength and fracture energy. Notably, under zero pre-compression, a transient increase in fracture energy is observed during the initial phase (0–6 days); this is attributed to the synergistic effect of moisture activation and thermal expansion, which enhances mechanical interlocking. Conversely, prolonged cycling induces binder phase weakening and pore structure coarsening, resulting in a marginal increase in dilatancy. Building upon a proposed interfacial shear bond strength model that accounts for dilatancy, this work elucidates the coupling effects of hygrothermal exposure and pre-compression on the mechanical performance of ancient masonry. Building upon a modified interfacial shear strength model that accounts for dilatancy, this work elucidates the coupling effects of hygrothermal exposure and pre-compression on the mechanical performance of ancient masonry. The model parameters were calibrated for the specific ancient brick–glutinous rice mortar system investigated in this study, and its applicability should therefore be understood within this material and environmental context. These findings provide a robust theoretical basis for the safety assessment of heritage structures in complex environmental conditions.

Freeze-thaw damage (FTD) prediction is closely related to the durability design of concrete in cold regions. However, current machine learning models for FTD predominantly rely on numerical data, overlooking crucial textual information regarding the FTD process. This limits the prediction accuracy and interpretability of machine learning. To address this, we constructed a comprehensive dataset comprising 1851 samples extracted from 44 publications, which includes both numerical parameters and textual descriptions (i.e., corrosion environments, experimental processes, morphologies, and FTD mechanisms). A multimodal deep learning (MDL) model that integrated natural language processing (NLP) with deep neural networks (DNN) was then developed to predict FTD. The results show that compared with conventional DNN models, the multi-head self-attention model improves the prediction accuracy of concrete mass loss rate and relative dynamic elastic modulus by 8% and 21%, respectively. The visualization indicates that the improvement in the prediction accuracy of the developed MDL model is attributed to the prior knowledge in the textual information.

This study systematically investigates the effects of water-to-binder ratio (W/B), supplementary cementitious materials (SCMs) composition, and calcium sulfoaluminate cement (SAC) substitution on the rheological behavior, shrinkage performance, mechanical properties, and microstructural evolution of sprayed ultra-high-performance concrete (SUHPC). Three W/B, varying proportions of silica fume (SF) and fly ash microspheres (FAM), and different SAC substitution rates were compared. Rheological results indicated that increasing the SF content or partially replacing ordinary Portland cement (OPC) with SAC significantly enhanced the yield stress and plastic viscosity. A 10 % SAC content increased yield stress by 1.8 times and plastic viscosity by 2.6 times. Concentrated early-stage exothermic reactions under a rapid setting induced significant autogenous shrinkage in SUHPC. Replacing 5 % OPC with SAC reduced autogenous shrinkage by 41.6 %. Under accelerated curing conditions, all mixtures achieved compressive strengths exceeding 60 MPa at 1 d and 120 MPa at 28 d. However, excessive SF increased porosity and microcracking, leading to strength reduction. Microstructural analysis revealed: X-ray diffraction (XRD) and thermogravimetric analysis (TGA) confirmed that SAC (at 5 % and 10 % dosages) promoted AFt formation. Mercury intrusion porosimetry (MIP) ndicated that the AFt generated by SAC filled the pore spaces, increasing the gel pores (<10 nm) while reducing the medium capillaries (10-50 nm), thereby mitigating shrinkage. These findings provide theoretical and practical guidance for SUHPC, particularly for underground engineering and repair applications that require high early strength and dimensional stability.

To address the dual challenges of high carbon emissions from the cement industry and the accumulation of regional industrial solid wastes, this study developed an all-solid-waste composite using ground granulated blast-furnace slag (GGBS), fly ash (FA), and coal gangue (CG) as precursors, carbide slag (CCR) as a solid activator, and aeolian sand (AS) as fine aggregate. Systematic experiments were conducted to reveal the effects of activator (CCR versus strong alkaline solution) and binder composition on flowability, strength, hydration kinetics, and microstructure. The results indicate that increasing GGBS content enhances the system’s available Ca2 + for hydration, which promotes gel formation and strength development. FA improves flowability and contributes to later-age strength through pozzolanic reactions. When CG content is below 20%, it enhances heat release and early-age reactivity; excessive CG introduces abundant crystalline phases, restricting gel formation, coarsening the pore structure, and limiting strength gain. CCR provides a highly alkaline environment that effectively facilitates the depolymerization of the glassy phase and activates the hydration reaction. In addition, the CCR-activated system exhibits lower exothermicity and a more moderate reaction kinetics, favoring the formation of C-(A)-S-H gel with an elevated Ca/Si ratio. The optimal binder composition of the CCR system is GGBS:FA:CG = 7:2:1, achieving a 28-day compressive strength of 34.0 MPa. The CCR-activated all-solid-waste based composite can reduce carbon emissions by 91.8% and costs by 62.9% compared with river sand cement mortar. These findings provide new reference for the synergistic high-value utilization of multiple industrial wastes and regional resources.

Ancient brick masonry structures exhibit damage and deterioration under the action of a hygrothermal environment, ultimately causing complete failure and destruction. To investigate the damage characteristics of ancient Chinese brick masonry subjected to fatigue loading after hygrothermal exposure, ancient brick masonry specimens were selected as the research object and first subjected to accelerated hygrothermal aging. Uniaxial cyclic loading-unloading tests were then combined with nuclear magnetic resonance (NMR) and scanning electron microscopy (SEM) to examine the effects of fatigue loading on the deformation behavior and energy-evolution characteristics of the specimens. The results show that, under hygrothermal conditions, the stress-strain response of ancient masonry still exhibits a distinct three-stage development pattern of "sparseness-denseness-sparseness." The pore evolution of ancient masonry is essentially a dynamic transformation from pore compaction to interconnection and penetration under fatigue loading, reflecting the progressive accumulation of fatigue damage. Furthermore, grey relational entropy analysis statistically confirms the intrinsic consistency between pore evolution and energy dissipation. The results demonstrate that the energy-evolution behavior is highly consistent with the mesoscopic damage mechanisms revealed by NMR and SEM, as well as with the macroscopic deformation characteristics obtained from VIC, and accurately captures the intrinsic relationship of energy transformation during the fatigue-damage process of brick masonry. These findings provide an energy-based interpretive framework for a deeper understanding of the fatigue deterioration mechanism of ancient brick masonry.

Chloride-induced rebar corrosion is the primary cause of durability degradation in reinforced concrete structures. Developing highly efficient chloride-adsorbing corrosion inhibitors is crucial for extending the service life of engineering structures. In this study, a novel highly dispersible chloride-adsorbing corrosion inhibitor (LDHs-TTA-PCE) was synthesized via the calcination-reduction method. Combined with experimental characterization, density functional theory (DFT) and molecular dynamics (MD) simulations, its Cl- adsorption mechanism, TTA(-) release behavior, and film formation mechanism on rebar surfaces in simulated concrete pore solutions (SCPs) were systematically investigated. The results show that LDHs-TTA-PCE exhibits excellent Cl- adsorption performance in both deionized water (DIW) and SCPs, with a theoretical maximum adsorption capacity (Q(m)) of 5.284 mmol/g in DIW, significantly exceeding the reported values of existing LDHs-based corrosion inhibitors. In SCPs, OH- induces partial premature release of TTA(-) at low Cl- concentrations (<0.4 mol/L), while exerting negligible influence at high Cl- concentrations (>0.4 mol/L). Electrochemical tests confirm that LDHs-TTA-PCE increases the critical Cl- concentration for rebar corrosion from 0.02 mol/L (control group) to 0.16 mol/L, significantly retarding chloride-induced corrosion. DFT and MD simulations reveal that the binding energy of LDHs with TTA(-) is higher than that with Cl-, promoting ion exchange. The released TTA(-) forms stable FeN coordination bonds with Fe atoms via N atoms, regulating charge transfer and weakening the interaction between Cl- and Fe. This study provides novel strategies and theoretical support for developing highly dispersible, high-performance rebar corrosion-resistant materials, with significant application prospects in concrete structures in marine, coastal, and other chloride-rich environments.

MgO expansive agents (MEA) and fly ash are commonly used in cementitious materials because they have the characteristics of long-term shrinkage compensation and structural optimization, respectively. However, the mechanism of synergy between MEA and fly ash remains unclear for cementitious materials under conditions of sustained high temperatures. Therefore, a cementitious system with MEA and fly ash was investigated through macroscopic and microscopic experiments under sustained exposure to elevated temperatures of 120, 160, and 200 ℃. The restrained expansion ratio decreased from 3.04 × 10-4 to 0.30 × 10-4–0.39 × 10-4 after 1 d of elevated-temperature exposure and remained positive throughout 60 d, demonstrating sustained shrinkage compensation. Compressive and flexural strengths initially increased, then decreased and stabilized; compressive strength peaked at 87.0 MPa after 14 d at 120 ℃, 79.6 MPa after 7 d at 160 ℃, and 79.3 MPa after 3 d at 200 ℃. Thus, higher temperature accelerated early strength development but reduced peak strength and long-term retention. Short-term elevated-temperature exposure increased stiffness and peak stress while promoting earlier strain localization and a stronger brittle-failure tendency. Meanwhile, the elevated temperature promoted further hydration of residual cement and MEA and activated the reaction of pozzolanic for fly ash, increasing the contents of Mg(OH)2 and Ca(OH)2. However, rapid moisture loss and hydrate dehydration coarsened the pore structure, increasing total pore volume from 0.099 to 0.190–0.200 mL/g after 1 d. Finally, a conceptual mechanism was proposed, highlighting that the elevated-temperature exposure activated pozzolanic reaction and ongoing MEA hydration partially offset the matrix coarsening induced by thermal dehydration.

Existing low-carbon concrete optimization approaches typically treat performance indicators such as compressive strength and durability as optimization objectives. However, in engineering practice, these indicators are required only to meet design code specifications and service-life requirements rather than to be continuously improved. This study proposes a multi-objective optimization framework for concrete under chloride environments, in which compressive strength and chloride diffusivity are treated as constraints rather than optimization objectives, while carbon emissions and cost are minimized as the primary objectives. In this framework, deep neural network (DNN) was employed to predict the compressive strength of concrete. Given the complexity of factors influencing chloride diffusion in concrete, including material properties and environmental conditions that are difficult to quantify and often described in textual form, this study developed a text-enhanced deep learning model to accurately predict the chloride diffusivity. The results demonstrate that both models can effectively capture the nonlinear relationships between the input variables and compressive strength/chloride diffusivity. Subsequently, the constraint-handled non-dominated sorting genetic algorithm II (NSGA-II) and technique for order preference by similarity to ideal solution (TOPSIS) were adopted to obtain the optimal solution. The optimization results of the concrete with low-carbon raw materials indicate that reductions of 20.35% in carbon emissions and 12.18% in cost can be achieved. In the benchmark case based on pier concrete from the Hong Kong-Zhuhai-Macao Bridge, the optimized concrete mix can reduce carbon emissions and cost by 17.34% and 3.00%, respectively.

In this study, CO2-cured reinforced mortar specimens with surface carbonation and sufficient carbonation were prepared, representing insufficient and sufficient CO2 sequestrations, respectively. The corrosion development of reinforcing steel under chloride drying-wetting cycles was investigated using electrochemical techniques, such as electrochemical impedance spectroscopy, potentiodynamic polarization, and galvanostatic/potentiostatic steps, etc. Meanwhile, scanning electron microscopy and Raman spectroscopy were employed to examine the microstructure and chemical compositions of corrosion products. Electrochemical results show that the specimens with surface carbonation maintain a relatively low corrosion rate (approximately 0.0024 mm/a) throughout the drying-wetting cycle process. Although the specimens with sufficient CO2 sequestration (approximately 0.0032 mm/a) exhibit a slightly higher corrosion rate than standard-cured specimens (approximately 0.0024 mm/a) in the early stage of the chloride drying-wetting cycles, their (approximately 0.0069 mm/a) corrosion rate becomes significantly lower than the standard-cured specimens (approximately 0.0118 mm/a) in the later stage, indicating a slower corrosion development. Compared with standard-cured specimens, the corrosion products in specimens with CO2 sequestration show less cracks and consist mainly of alpha-FeOOH, gamma-Fe2O3, and Fe3O4. In contrast, the corrosion products in specimens without CO2 sequestration are dominated by crystalline gamma-FeOOH and alpha-Fe2O3. These characteristics are identified as the main factors contributing to the retarded corrosion development in sufficiently carbonated specimens.

CO2 curing has a great influence on the phase assemblages and pore structure in cement-based materials, thereby altering their moisture transport behaviors. However, the effect of CO2 curing on the moisture transport in cement-based materials still remains unclear. In this study, the water vapor sorption isotherms (WVSIs), capillary water absorption, and drying kinetics of Ordinary Portland cement (OPC) and slag cement materials under CO2 curing with sufficient carbonation were investigated. The variations in the pore structure caused by CO2 curing were also examined by employing the surface fractal dimension based on MIP results. The WVSIs results indicate that the hysteresis phenomenon diminishes in CO2-cured materials compared to standard-cured materials, which is attributed to the fact that CO2 curing reduces the content of C-S-H gel and the amount of “ink-bottle” pores. CO2 curing can lead to an increase in the capillary water absorption capacity of cement-based materials and a decrease in its moisture retention capacity due to the alteration in the pore structure. In addition, the drying kinetics results demonstrate that CO2 curing leads to greater mass loss at a given RH. The inverse calculation shows an increase in the intrinsic permeability (Kl) of CO2-cured specimens, and the Kl increases further with higher slag content. This trend is consistent with the observed increases in the water absorption coefficients and the reductions in the moisture retention capacity.

Coastal concrete structures and drainage pipes are prone to microbially influenced deterioration. However, differences in microbial communities and their corrosion/healing potentials between these habitats remain unclear. Here, we compared bacterial(16S), fungal (ITS) and algal(18S) communities on coastal concrete(C) and drainage pipe(P) surfaces. Fungal and algal α-diversity were significantly higher in P than in C, while bacterial diversity did not differ. β-Diversity strongly separated bacterial and algal communities between habitats, but not fungi. A shared core “seed bank” of 575 bacterial, 520 fungal and 40 algal ASVs was identified. Student’s t-test revealed that P enriched oligotrophic degraders (Sphingomonas) and acid-producing fungi (Arxiella, Bisifusarium), whereas C selected for halotolerant EPS-producing bacteria (Tunicatimonas, Muricauda) and the extremotolerant alga Coelastrella. db-RDA linked these differences to salinity, NH4+-N, NO3--N, and COD. Functional prediction indicated a shift from metabolism pathways in C to signaling in P. Co?occurrence networks revealed cross-kingdom competition and within-kingdom cooperation, especially among algae. Importantly, both habitats harbored microorganisms with documented corrosion and healing potentials, but under natural conditions, net deterioration dominated, microbial healing is hardly to counteract the negative effects. This study provides a functional taxonomic framework for understanding and managing concrete microbiomes in coastal and sewer infrastructure.

Graphene oxide (GO) had great potential in improving the performance of cement-based materials. However, the strong interaction between GO sheets was easy to cause agglomeration, which seriously limited the full play of its enhancement effect. To address this issue, this study proposed a novel strategy using manganese-zinc ferrite (MZF) to assist the dispersion of GO, aiming to solve the key problems of uneven dispersion and poor stability of GO in cement-based materials. In this study, MZF@GO materials with different composite ratios (MZF: GO = 2:1, 5:1, 10:1) were prepared. The dispersion behavior of MZF@GO was discussed. The effects of MZF@GO on the hydration process, macroscopic properties, and microstructure of cement composites were systematically studied. The results showed that MZF formed strong interfacial bonding with GO through chemical coordination, exhibiting excellent dispersion stability in simulated cement pore solution. After adding cement, MZF@GO accelerated the hydration heat release of cement, and the peak heat flow of MZF-5@GO was the highest (2.1mW/g). Compared with the JZ group (curing 28 days), the compressive strength of MZF-2@GO, MZF-5@GO, and MZF-10@GO samples increased by 9.39%, 16.18%, and 8.87%, respectively, while the flexural strength increased by 22.67%, 32.86% and 26.03%, respectively. Meanwhile, the total porosity of the MZF-5@GO group decreased by about 13.26%, indicating that the dispersed GO could effectively promote the growth of hydration products and reduce harmful pores, whereas MZF primarily contributed through physical filling. MZF@GO did not significantly reduce the resistivity of cement composites. Overall, MZF served as an effective dispersing medium for GO and provided a new approach for its efficient application in cement-based materials.