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The mechanical properties of porous concrete, such as strength and durability, are significantly influenced by moisture transport, particularly in the case of recycled aggregate concretes. The pore distribution and pore size of the concrete, as well as the ambient temperature in the surrounding environment, exert a significant influence on the moisture transport. This paper establishes the fractal Fick’s law, the fractal Darcy law, and the fractal Richards equation. In conclusion, a fractal model for the diffusion and permeability in porous concrete is established. This study examines the mechanisms of moisture diffusion and water permeability in concrete. The comparison of the theoretical prediction with the experimental data indicates a high degree of congruence, thereby suggesting that the concrete’s relative humidity response can be predicted by the established model. This provides a foundation for the optimal design of concrete with required mechanical properties in special applications. [ABSTRACT FROM AUTHOR]

Recycled gypsum powder from waste drywalls is a new alternative that has been recently introduced for partial cement replacement in concrete for construction applications. It has been shown that the recycled gypsum, alongside fly ash, can partially replace cement in concrete to some extent without hurting the required properties of concrete. In this paper, the impact of recycled gypsum content on the durability of concrete (hereafter called gypsum concrete) exposed to different environmental exposures is evaluated. A total of 153 concrete cylinders (100×200 mm) with different recycled gypsum contents (0%, 10%, and 20% of cement replacement) were considered. Each mix was exposed to air-dry, freshwater, seawater, freshwater–air dry cyclic, and seawater–air dry cyclic conditions. The specimens were tested in compression loading after 1,000, 3,000, and 6,000 h of exposure. Recycled gypsum used in this research was in two types of a powder with fine particles only (hereafter called fine gypsum) and in the form of mixed fine, coarse, and paper particles (hereafter called whole gypsum). Other mechanical and physical properties of concrete such as absorption, volume change, and ultrasonic pulse velocity were analyzed. It was observed that the compressive strength of the specimens with 10% and 20% fine gypsum content at Day 28 was about 36% and 40% lower than that of the control specimens, respectively. However, the strength gap was reduced to about 16% and 7% at the end of 6,000 h in the air-dry condition. The specimens submerged in freshwater and seawater showed a rate of strength gain higher than that of the control specimens, bringing the compressive strength of the gypsum concrete specimens slightly higher than that of the control specimens after 6,000 h exposure. Overall, recycled gypsum in combination with fly ash not only does not hurt the long-term strength of concrete but also can enhance the strength under certain conditions, mostly those exposures involving water exposure. [ABSTRACT FROM AUTHOR]

Self-desiccation-induced shrinkage may result in cracking at an early age, which is averse to the durability of concrete. Internal curing (IC) agents, such as superabsorbent polymers (SAP), are normally used for moisture regulation and shrinkage reduction. In addition, the make-up of recycled shale lightweight aggregate (RSLA) results in a good absorbing capacity, which makes it a potential candidate for IC. In this paper, the synergistic effect of SAP and RSLA on the relative humidity (RH) variation in early-age concrete under sealed conditions is investigated experimentally in terms of the setting time, relative humidity, and autogenous shrinkage. The results indicate that adding SAP and presoaked RSLA can significantly postpone the initial and final setting times. The initial setting time of RSLA30 and SAP06 is delayed by 127 and 171 min, respectively, compared to the benchmark mixture. In addition, increasing the amounts of SAP and presoaked RSLA can effectively extend the duration of the vapour-saturated stage, reducing the decrease in RH and autogenous shrinkage at 28 days. When the RSLA dosage increases from 0 to 10%, 20%, and 30%, the duration of the vapour-saturated stage is extended by 2, 9.4, and 26 days, respectively. Moreover, due to different water desorption behaviours, more IC water released by RSLA during the initial stage can slow the water release of SAP and lead to a higher RH level at 28 days. [ABSTRACT FROM AUTHOR]

This paper comprehensively summarizes moisture transport, ion transport, and mechanical damage models applied to concrete under sulfate attack and drying–wetting cycles. It highlights the essential aspects and principles of each model, emphasizing their significance in understanding the movement of moisture and ions, as well as the resulting mechanical damage within the concrete during these degradation processes. The paper critically analyzes the assumptions made in each model, shedding light on their limitations and implications for prediction accuracy. Two primary challenges faced by current models under sulfate attack and drying–wetting cycles are identified: the limited consideration of the coupled effects of chemical and physical attacks from sulfate, and the unclear mechanism of the sulfate attacks. Future research directions are proposed, focusing on exploring the transport mechanism of sulfate ions under various driving forces and further clarifying the crystallization process and expansion damage mechanism in concrete pores. Addressing these research directions will advance our understanding of sulfate attack under drying–wetting cycles, leading to improved models and mitigation strategies for enhancing the durability and performance of concrete structures. [ABSTRACT FROM AUTHOR]

Waste ceramic is produced from different sources and, if not reused, is often disposed of in landfills, contributing to the pressure on landfill capacity and potentially releasing toxins into the surrounding environment as ceramics break down over time. The waste can easily be crushed to the required sizes, which has interested many researchers. It has been used as a replacement for concrete constituents, including cement and aggregates. This offers a promising avenue for reducing the environmental impact and promoting sustainable construction practices by reducing the amount of energy consumed and resources required for concrete production, as well as the amount of waste being sent to landfills. This paper aims to provide a review of the use of waste ceramic in concrete. In essence, the paper is divided into several sections. The first section highlights the current environmental issues associated with concrete production and waste disposal. The second section deals with ceramics, its raw materials, production steps, and the different types of waste ceramic used in concrete. A literature review of the use of waste ceramic in concrete was included in the third section. The study reports different research on the use of waste ceramic and its impacts on the mechanical and durability properties of concrete. [ABSTRACT FROM AUTHOR]

Chloride corrosion is a key factor affecting the life of marine concrete, and surface chloride concentration is the main parameter for analyzing its durability. In this paper, we first introduce six erosion mechanism models for surface chloride ion concentration, reveal the convection effect in the diffusion behavior of chloride ions, and then introduce the corrosion mechanisms that occur in different marine exposure environments. On this basis, the analysis is carried out using empirical formulations and machine learning methods, which provides a clearer understanding of the research characteristics and differences between empirical formulas and emerging machine learning techniques. This paper summarizes the time-varying model and multifactor coupling model on the basis of empirical analysis. It is found that the exponential function and the reciprocal function are more consistent with the distribution law of chloride ion concentration, the multifactor model containing the time-varying law is the most effective, and the Chen model is the most reliable. Machine learning, as an emerging method, has been widely used in concrete durability research. It can make up for the shortcomings of the empirical formula method and solve the multifactor coupling problem of surface chloride ion concentration with strong prediction ability. In addition, the difficulty of data acquisition is also a major problem that restricts the development of machine learning and incorporating concrete maintenance conditions into machine learning is a future development direction. Through this study, researchers can systematically understand the characteristics and differences of different research methods and their respective models and choose appropriate techniques to explore the durability of concrete structures. Moreover, intelligent computing will certainly occupy an increasingly important position in marine concrete research. [ABSTRACT FROM AUTHOR]

Cracks are inevitable in concrete structures, and the deterioration of concrete crack interfaces in intertidal zones is often accelerated due to seawater dry–wet cycles. This paper aims to analyze the morphology and deterioration of crack interfaces under seawater dry–wet cycles. First, concrete crack surface specimens were obtained through splitting tests. Then, the specimens were placed in seawater solutions of different concentrations to undergo seawater dry–wet cycles. Furthermore, three-dimensional (3D) laser surface profile scanning was performed on the specimens after 0, 10, 30, and 60 seawater dry–wet cycles. Finally, the changes in morphological parameters were analyzed and calculated to derive the effect patterns of seawater dry–wet cycles on the 3D morphology of concrete crack interfaces. The results showed that the crack surface deterioration of the specimens in clear water was only affected by the dry–wet cycles, while that in seawater was jointly affected by seawater erosion and dry–wet cycles. The crack surface deterioration of the specimens in seawater can be divided into two stages. In the first 10 seawater dry–wet cycles, the chemical products generated by seawater erosion played a dominant role. The 3D morphological parameters and 3D fractal dimension changes of the specimens in seawater showed opposite trends to those in clear water. From the 10th seawater dry–wet cycle, erosion and flaking by the dry–wet cycles were dominant. The changes in the 3D morphological parameters and 3D fractal dimension of the specimens in seawater were consistent with those in clear water. Moreover, higher seawater concentrations led to more significant trends in the crack surface 3D morphological parameter and 3D fractal dimension changes. Concrete structures are common in marine engineering, such as port wharves, sea crossing bridges, drilling platforms, and island reef revetments. Concrete structures exposed to tides/splashes for long periods are susceptible to seawater dry–wet cycles, which may lead to structural cracking during their service life. To ensure the safety and service life of concrete structures, cracks must be addressed with repairs or reinforcements. Numerous studies have shown that the concrete crack surface morphology determines the repair and reinforcement effects and affects the interfacial bonding performance, mechanical properties, and durability. Therefore, studying the surface morphology variation patterns of concrete cracks under seawater dry–wet cycles is important for concrete repair and reinforcement. In this paper, we produce concrete cracks through splitting and conduct seawater dry–wet cycle tests on concrete crack interfaces under different seawater concentrations to study the 3D morphological characteristics of cracks under seawater dry–wet cycles and provide experimental data to reveal the concrete crack surface changes for future repair. This study could serve as a guideline for repairing cracks in concrete structures in tidal/splash zones. [ABSTRACT FROM AUTHOR]

Natural zeolite is a honeycomb-structured aluminosilicate mineral with an open crystalline structure which makes it suitable for a variety of applications. Given the beneficial effects of zeolites on the properties of cementitious materials, the present paper aims to summarize the recent findings reported in the scientific literature on the use of zeolites in cement-based construction materials. This paper limits the analysis to natural zeolites. The influence of natural zeolites on the workability and setting time of cement-based construction materials revealed that increasing the zeolite content led to a reduction in workability compared to the control mixes. At the same time, the initial and final setting times of cement pastes showed a decreasing trend with an increase in the replacement percentage. The slow pozzolanic reaction of clinoptilolite zeolite results in lower flexural strength and compressive strength values of mortars at the age of 28 days. Blending zeolites with other supplementary cementitious materials resulted in improved values of the mechanical properties of mortar and concrete. The findings regarding the impact of zeolite on the durability of concrete suggest that zeolite shows promise as a viable alternative to cement, with positive effects on various aspects of durability. The majority of the durability factors are interconnected. The presence of conflicting findings is particularly significant in this context, highlighting the need for a comprehensive approach to address these challenges in the future. [ABSTRACT FROM AUTHOR]

Concrete durability is greatly influenced by the transport rate of aggressive chemicals. Moisture diffusion plays a key role in the long-term performance of cementitious materials, as it facilitates the entry of aggressive chemicals into concrete. The pore size distribution plays a critical role in determining moisture diffusivity. However, the characteristics of the concrete pore structure have not been included comprehensively in the material models so far. In this paper, a theoretical model was developed to obtain the pore size volume fractions for each diffusion mechanism including Molecular, Knudsen and Surface diffusions. An effective moisture diffusivity in concrete was then obtained using the weighted average based on the diffusion mechanisms and pore size volume fractions. The model's validity was demonstrated by comparing model predictions with available experimental data. The findings of this study provide valuable insights into the behavior of the concrete pore structure and its impact on moisture diffusivity. [ABSTRACT FROM AUTHOR]

The chloride diffusivity of calcium silicate hydrate (C-S-H), as the main hydration product of cement paste, plays an important role for the durability of concrete structures, especially for low w/c ratio ones. In this paper, in order to measure the chloride diffusion coefficient of C-S-H, a diffusion path conversion method is proposed to convert the primary diffusion path of ions from capillary pores to gel pores. By combining diffusion path conversion method with steady-state migration test, the diffusion coefficients of C-S-H are obtained. Based on 3D nanostructure, which is generated by a hybrid scheme of Grand Canonical Monte Carlo and Molecular Dynamics, the chloride diffusion coefficient of C-S-H is predicted by a 3D diffusive lattice modelling. Results from the experiments and simulation are compared with the data in the literature. Our work contributes to the understanding of C-S-H diffusivity and is of great importance for predicting the long-term durability of concrete structure. [ABSTRACT FROM AUTHOR]

Copyright of Environmental & Social Management Journal / Revista de Gestão Social e Ambiental is the property of Environmental & Social Management Journal and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The alkali–silica reaction significantly impacts the durability of reinforced concrete structures. This paper aims to investigate the structural expansion properties of reinforced concrete beams under different partial alkali–silica reactions. Alkali–silica reaction tests were conducted on four reinforced concrete beams, focusing on immersion depth and NaOH solution position as key parameters. Subsequently, the spatial and temporal distribution characteristics of the beam expansion rate were analyzed. Results indicate notable variations in the expansion's initiation, rate, and final magnitude at different measurement points on the concrete beam, depending on the soaking positions and depths used. The expansion rate was higher in areas directly immersed in the NaOH solution, decreasing near the reinforcement regions. However, strain distribution, along with beam height, satisfied plane-section assumption in the reinforced beam section. Finally, a regional expansion index was established to quantitatively assess the non-uniform damage by alkali aggregates in beams, and the uniaxial restraint mechanism in reinforced concrete structures was also described. [ABSTRACT FROM AUTHOR]

Copyright of Revista Facultad de Ingeniería Universidad de Antioquia is the property of Universidad de Antioquia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Low-Carbon Materials & Green Construction is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper describes a study of the chloride content in the concrete lagging of prestressed concrete elements of the roof structure of an aluminium foundry building. Sources of chloride pollution in industrial facilities are discussed. Methods for collecting dust deposited on the structure and sampling concrete for chloride concentration testing are presented in detail. The test methods used and the apparatus used to assess the chloride content at the thickness of concrete reinforcement lagging are presented. Investigations of the chloride content in the concrete of the reinforcement cover showed a very high concentration of chloride in the near-surface layer, depending on the location of the element in relation to the source of chloride emission into the environment. In contrast, the concrete of the deeper layers of the lagging contained very small amounts of Cl− chlorides. The results of the chloride content of the lagging concrete were plotted against the distance from the surface of the specimen and approximated by the function C(x,t) based on Fick's second law and its solution. A satisfactory fit of the course of this function to the experimental results was obtained. Based on the obtained C(x,t) function, the durability of the main structural components of an aluminium foundry industrial hall operating in a chloride environment was estimated. [ABSTRACT FROM AUTHOR]

Polypropylene fiber reinforcement is an effective method to enhance the durability of concrete structures. With the increasing public interest in the widespread use of polypropylene fiber reinforced concrete (PFRC), the necessity of evaluating the mechanism of polypropylene fiber (PF) on the permeability of concrete has become prominent. This paper describes the influence of PF on the concrete permeability exposed to freeze-thaw cycles under compressive and tensile stress. The permeability of PFRC under compressive and tensile loads is accurately measured by a specialized permeability setup. The permeability of PFRC under compressive and tensile loads, the volume change of PFRC under compressive load, and the relationship between compressive stress levels at minimum permeability and minimum volume points of PFRC are discussed. The results indicate that the addition of PF adversely affects the permeability of concrete without freeze-thaw damage and cracks. However, it decreases the permeability of concrete specimens exposed to freeze-thaw cycles and cracking. Under compressive load, the permeability of PFRC initially decreases slowly and follows by a significant increase as the compressive stress level increases. This phenomenon correlates with the volume change of the specimen. The compressive stress level of the minimum permeability point and compressive stress level of the minimum volume point of PFRC exhibit a linear correlation, with a fitted proportional function parameter γ ≈ 0.98872. Under tensile load, the permeability of PFRC increases gradually with radial deformation and follows by a significant increase. The strain-permeability curves of PFRC under loading are studied and consist of two stages. In stage I, the permeability of PFRC gradually decreases with the increase of strain under compressive load, while the permeability increases with the increase of strain under tensile load. In stage II, under compressive load, the permeability of PFRC increases with the increase of freeze-thaw cycles, whereas under tensile load, the permeability gradually decreases with the increase of freeze-thaw cycles. The reduction of PF on the permeability of PFRC under tensile load is greater than that under compressive load. In future research, the relationship between strain and permeability of PFRC can be integrated with its constitutive relationship between stress and strain to provide a reference for the application of PF in the waterproofing of concrete structures. [ABSTRACT FROM AUTHOR]

This study investigates on the impact of basalt fiber reinforcement concrete in protected building and structures. Basalt fibers, derived from the melting of basalt rock at temperatures ranging from 1,500 to 1700°C, are recognized as sustainable and environmentally friendly fiber materials. Various studies have revealed differing optimal percentages of basalt fibers for enhancing the mechanical and chemical properties of concrete. The objectives of this paper are to investigate the effects of basalt fibre reinforcement on mechanical properties like tensile, compressive, and bending strengths. Additionally, performance indicators like void content, water absorption, chloride ion permeability, alkali and slag resistance, temperature stability, shrinkage characteristics, and abrasion resistance will be evaluated. Basalt fibre is typically utilised to increase the mechanical properties and durability of concrete, which has an impact in the effect on protected buildings and structures. The findings indicate that the most effective percentage range for improving mechanical properties lies between 0.1% and 0.3% of basalt fibers. Notably, concrete reinforced with basalt fibers demonstrates superior mechanical and chemical performance in alkaline environments compared to other fiber types. Moreover, the addition of 0.5% basalt fibers to concrete has been shown to significantly reduce chloride ion penetration, as evidenced by a decrease in RCPT load from 2,500 (C) to 1900 (C), indicative of enhanced chloride resistance. Reinforced concrete containing basalt fibers exhibits remarkable temperature resistance, withstanding temperatures exceeding 800°C due to its high-water absorption capacity. Additionally, basalt fibers exhibit resilience at temperatures up to 200°C. However, it is noted that the introduction of 0.14% basalt fibers leads to a slight increase in water absorption from 4.08 to 4.28. In general, basalt fibres are beneficial to many aspects of concrete; they strengthen resistance to temperature, alkali, acid exposure, and chloride while also improving mechanical qualities such as bending and tensile strength. The development of basalt fibres that extend building lifespans and improve concrete quality for structural engineering applications is making encouraging strides, according to all the results. [ABSTRACT FROM AUTHOR]

In this paper, a novel numerical model for characterizing the seepage and dissolution coupling effect on the durability of anti-seepage walls of earth-rock dams is proposed. The model considers the influence of hydraulic gradient-driven seepage on the non-equilibrium decomposition of the calcium dissolution in concrete, as well as the effects of seepage dissolution on pore structure, permeability, and diffusivity. The reasonableness of the model is validated by experimental and literature data, which is then applied to analyze the deterioration and failure processes of a concrete cutoff wall of an earth-rock dam in Zhejiang Province, China. On this basis, the seepage dissolution durability control indices of anti-seepage walls are identified. The findings demonstrate that the suggested method accurately explains the calcium leaching process in concrete. Under the seepage and dissolution coupling effect, calcium in the wall continuously decomposes and precipitates, leading to varying degrees of increases in structural performance parameters, which weaken the seepage control performance of the walls and consequently result in an increase in seepage discharge and hydraulic gradient. By proposing the critical hydraulic gradient as a criterion, the service life of the wall is projected to be 42.8 years. Additionally, the upstream hydraulic head, the initial permeability coefficient, and the calcium hydroxide (CH) content are three crucial indices affecting the durability of walls, and these indices should be reasonably controlled during the engineering design, construction, and operational phases. [ABSTRACT FROM AUTHOR]

In order to deal with the problem that the marine concrete with large dosage of mineral admixture in the actual project faces the harsh marine environment prematurely and is easy to be eroded by chlorine salt, this paper proposed to use magnetized water instead of tap water to prepare marine concrete, studied the influence law of magnetized water on the mechanical properties and durability of marine concrete at different ages, and analyzed the microstructure of marine concrete using the mercury instrusion porosimetry and scanning electron microscope. The study shows that magnetized water improves the workability of marine concrete. Compared with tap water, magnetized water has obvious improvement on the early mechanical properties of marine concrete, in which the compressive strength and splitting tensile strength of C50 marine concrete with a curing age of 7 d increase by 17.9% and 16.5%, respectively. Regardless of different curing ages, the resistance to carbonation and chloride ion penetration of magnetized water marine concrete are better than tap water marine concrete. The degree of reaction of cementitious materials in magnetized water marine concrete is higher, with fewer cracks, and the microstructure between cementitious materials and aggregates is more compact. The overall porosity is lower, with more harmless pores and fewer harmful pores, leading to a denser microstructure. Thus the mechanical properties and durability of marine concrete are improved. [ABSTRACT FROM AUTHOR]

Rubber concrete has been applied to a certain extent in fatigue-resistant structures due to its good durability. Based on a cohesive model of rubber composed of a five-phase material containing mortar, aggregate, rubber, aggregate-mortar interfacial transition zone (ITZ), and rubber-mortar ITZ, this paper studies the influence of the cohesive parameters in the rubber-mortar ITZ on the fatigue problem of rubber concrete on the mesoscopic scale. As the weak part of cement-based composite materials, the ITZ has a great influence on the mechanical properties and durability of concrete, but the performance of the ITZ is difficult to test in macro experiments, resulting in difficulties in determining its simulation parameters. Based on the cohesive model with a rubber content of 5%, this study uses Monofactor analysis and the Plackett-Burman test to quickly and effectively determine the primary and secondary influences of the cohesive model parameters in the rubber-mortar ITZ; further, the response surface method is used to optimize the cohesive parameters in the rubber-mortar ITZ, and the numerical simulation results after optimizing the cohesive parameters are compared and analyzed with the simulation results before optimization. The results show that, under the setting of the optimized parameters, the simulation results of each item of the optimal cohesive model parameters in the rubber-mortar ITZ are in line with the reality and closer to the experimental data, and they are also applicable to rubber concrete models with different rubber dosing. [ABSTRACT FROM AUTHOR]

This work examined the performance of self-heating concrete under laboratory thermal conditions and outdoor real-time conditions during the fall and winter seasons. Snow-melting and freeze–thaw performance of low-temperature phase change materials (PCM) incorporated self-heating concrete slabs in various scales were evaluated. PCM exhibited high enthalpy of fusion (ΔHf≈170–180 J/g), long-term thermal stability, and desirable supercooling. The experimental program included (1) optimization of concrete mix designs for maximum PCM incorporation, (2) characterization of thermal properties of PCM-mortar specimens using longitudinal guarded comparative calorimetry (LGCC), and (3) large-scale PCM concrete slabs in outdoor conditions to evaluate the real-time thermal performance against freeze–thaw events and snow-melting efficiency. Two different approaches were used to incorporate PCM in concrete: (1) submersion of liquid PCM in porous lightweight aggregates (PCM-LWA); and (2) microencapsulated PCM (MPCM). Both PCM-LWA and MPCM concrete not only exhibited promising snow-melting capabilities but also lowered the number of freeze–thaw cycles during cold seasons. PCM-LWA concrete performed better in decreasing the number of freeze–thaw (F-T) cycles due to the undercooling phenomenon created by the LWA pore network confinement pressure, allowing gradual latent heat release; the undercooling phenomenon in PCM-LWA results in phase transformation in a wider low-temperature range (i.e., 3.94°C to −13.04°C). Therefore, the PCM-LWA concrete was effective in melting snow within a wider range of low temperatures. MPCM concrete was found to provide a rapid melting capability during a snowfall event due to its "one-shot" heat release phenomenon. Both LWA-PCM and MPCM concrete slabs demonstrated promising heat response and snow-melting capability. Snowfall and freeze–thaw cycles occur frequently during winter seasons in North American regions with cold climate, resulting in snow accumulation on concrete roads and flatworks as well as concrete freeze–thaw damage. In this paper, a "self-heating" concrete was developed via incorporation of low-temperature phase change material (PCM), and its promising snow removal and freeze–thaw improvements were validated. The self-heating concrete can be used to construct pavements, driveways, bridge decks, and any other types of flatworks. When the ambient temperature falls to ∼0°C , PCM will release desirable amounts of heat energy (ΔHf=170–180 J per g of PCM added) by changing its phase from liquid to solid. As a result, the accumulated snow and ice melts at a gradual pace. In addition, heat release from the incorporated PCM lowers the number of freeze–thaw cycles, improving freeze–thaw performance of concrete made elements in cold regions, which in turn improves concrete durability and service life by minimizing the susceptibility to freeze–thaw scaling and spalling. [ABSTRACT FROM AUTHOR]

This paper explores the potential of a new source of fly ash, deposited on the site of a coal-fired power plant in Ireland dating from 1985 to 1995, as a cement replacement material. A series of X-ray diffraction (XRD) analyses on binder samples with cement replacement levels of 0, 10, 25 and 35% was undertaken to determine the fly ash's mineralogical composition and to determine its suitability as a supplemental cementitious material (SCM). The XRD results reveal a unique mineral composition with promising characteristics for enhancing the strength and durability of concrete. The experimental results were used to calibrate a thermodynamic model to predict changing phase assemblage and hydration behaviour over time and per replacement level. Thermodynamic models have been shown to give credible predictions of the long-term performance of cements, including SCMs. The initial experimental results' thermodynamic modelling demonstrates the feasibility of this fly ash source as a sustainable alternative to traditional cement, paving the way for more eco-friendly construction. Ash deposits dating from 1995 to 2005 and from 2005 to the present will be presented in subsequent publications. [ABSTRACT FROM AUTHOR]

The hydraulic concrete in the alpine region is subjected to alternating actions of freeze–thaw (F) and abrasion (W) during operation, resulting in significant deterioration of concrete durability. In this paper, the water/binder ratio (W/B) was employed as the test variable, the working condition F group and W group were set as the control group, and the working condition F-W group was used as the test group. Fast-freezing and underwater methods are used for the alternating test. By measuring the mass loss, relative dynamic elastic modulus (RDEM), surface morphological characteristics, fractal dimension of concrete in each alternating cycle, and the evolution law of concrete performance under the alternating action of F and W was explored. The results show that compared with the control group, the alternating action will accelerate the mass loss of concrete, reduce the RDEM, and cause the deterioration of surface wear. The maximum increase in mass loss and RDEM of concrete is 1.92% and 20.11%, respectively. During this process, the fractal dimension of the concrete increases as the number of alternating cycles increases, but it still does not exceed the limit of 2.4. In addition, a relationship function between the fractal dimension and the mass loss rate, volume loss, was established. It was found that the experimental group had a good linear correlation, and the correlation was close to 95%, which was about 20% higher than that of the control group. [ABSTRACT FROM AUTHOR]

Research on the combined substitution of supplementary cementitious materials (SCMs) has already demonstrated that it might be one of the few viable options to produce low-carbon concrete at scale. This paper presents an experimental investigation on the performance and durability of rice husk ash (RHA) and calcined clay (CC) in ternary blended concrete exposed to chloride attacks under wet/dry cycles. Portland cement (PC) was replaced by RHA and CC up to 50% by weight to produce low-carbon concrete. Samples were subjected to wet/dry cycles in 3.5% NaCl water, with mineralogical composition and microstructure development before and after exposure analysed by TGA-DSC, MIP, XRD, and SEM. The durability of the concrete against wet/dry cycles was investigated in terms of compressive strength, water absorption, open porosity, density, thermal conductivity, and electrical resistivity. The results showed that concrete mixes with CC and RHA up to 60% exhibited an increase of 33% in compressive strength, followed by minimal changes in water absorption. While a decrease in electrical resistivity was measured in all samples with RHA and CC, increasing the CC content to 50% resulted in improved resistance to chloride penetration. Increasing the CC content resulted in a more refined microstructure, with an overall decrease in porosity of up to 32% compared to the control series. While RHA alone did not contribute to significant improvements after wet/dry cycles, the combined substitution of RHA and CC at SCM replacement levels of 60% showed an overall improvement in hardened properties and durability. This investigation provides valuable insights into the long-term performance and strength of innovative low-carbon concrete. [ABSTRACT FROM AUTHOR]

Organic corrosion inhibitors (OCI) have been widely accepted as a reliable method for enhancing the durability of marine reinforced concrete structures. However, the effect of OCI on steel corrosion is not clear in the case of cracks appearing in the concrete cover. In this paper, steel corrosion behaviors in cracked concrete with different crack widths, intact concrete containing OCI, and cracked concrete containing the OCI exposed to the marine tidal zone were investigated through open-circuit potential tests and EIS measurements. The obtained results illustrate that the corrosion rate of steel in cracked concrete is reduced with the decrease of crack width having an initial width of less than less than or equal to 200 μm in the marine tidal zone. Based on the Rf and Rct values, it is found that the alcohol amine-based OCIs can improve the corrosion resistance of steel in intact concrete and concrete with microcracks (with a width of less than 100 μm) exposed to the marine tidal zone. The carboxylic acid-based OCIs aggravate the steel corrosion due to the hydrophobicity provided by carboxylic acids for seawater transport through cracks. The ester-based OCIs also increase the steel corrosion rate as it accelerates concrete carbonation. [ABSTRACT FROM AUTHOR]

This paper presents a study focused on two pivotal innovations in the field of fibre-reinforced concrete (FRC) to significantly enhance its durability and sustainability in construction. First, our research investigates the application of advanced self-healing mechanisms in FRC. By embedding microcapsules containing healing agents within the concrete matrix, we achieved a remarkable reduction in crack propagation and improved structural integrity. Our results demonstrate that the self-healing FRC exhibited a 30% increase in compressive strength and a 40% reduction in crack width, leading to a longer service life for concrete structures. Second, we explore the integration of sustainable materials in FRC production. By incorporating locally sourced and recycled materials, we successfully reduced the environmental impact associated with FRC manufacturing. Our findings reveal a substantial reduction in carbon emissions, with a 25% decrease in the overall carbon footprint of FRC production. This innovation not only contributes to a greener construction industry but also aligns with sustainability goals and regulations. This research underscores the transformative potential of self-healing mechanisms and sustainable material integration in FRC, offering tangible results in terms of increased durability and reduced environmental impact. These innovations promise to reshape the construction landscape, aligning it with the principles of sustainability and long-term structural resilience. [ABSTRACT FROM AUTHOR]

This paper examines the cracking behaviour of reinforced concrete beams strengthened by externally bonded fiber-reinforced polymer. The crack opening of RC structures is a key parameter for the durability of concrete structures. It is of vital importance for designers to be able to make correct estimations of the crack opening values of strengthened structures. FRP strengthening affects the cracking behaviour of RC beams with different steel percentages. Beams have been tested under four-point bending mechanical tests until failure with three steel ratios and two layers of externally bonded wet carbon fibers (CFRP). In order to measure the crack opening during loading, Digital Image Correlation is used to obtain the crack opening along the beam during load functioning. The results allow for a comparison of the RC beams with and without FRP and enhance the effect of FRP on crack opening. The crack width was compared with the theoretical values obtained based on the relation proposed by Eurocode 2 (EC2). The comparison enhanced the need to propose a modified relation. Subsequently, an empirical model was established as a modification of EC2, considering the presence of a CFRP system. The corresponding results were compared and discussed to validate the model. For the same level of loads, the crack opening can be reduced by 20 to 50% depending on the level of steel ratio. [ABSTRACT FROM AUTHOR]

As a pozzolan, waste glass powder (WGP) can improve the mechanical properties and durability of concrete, especially at a later age. However, the modification mechanisms should be fully understood and discussed. One of the effective approaches is to investigate the improvement in interfacial transition zones (ITZs) between aggregate and mortar matrix. In this paper, soda-lime WGP was used as a supplementary cementitious material and replaced 20% by weight cement in the sample with modeled aggregate. The phases and chemical composition within the ITZs and the adjacent mortar matrix were investigated by backscattered electron (BSE) imaging combined with image analysis. Advanced nanomechanical techniques were simultaneously applied, and the results obtained from nanoindentation and nanoscratch were compared. The results show that WGP can significantly reduce the width of ITZs and increase the content of calcium-silicate-hydrate (C-S-H) and Si/Ca ratio in both ITZs and matrix. The high heterogeneity of ITZ with WGP made it susceptible to errors caused by unreacted WGP during the measurement of C-S-H nano- and micromechanical properties. For the control group without WGP, the test results of nanoindentation and nanoscratch showed a high degree of consistency. However, for the samples with 20% by weight WGP, there are some differences in the test results between nanoindentation and nanoscratch. Nanoscratch was able to acquire abundant data in a short testing time and proved more suitable for the tests of homogeneous materials. On the other hand, for the sample with 20% by weight WGP, nanoindentation was found to more likely to reflect the real micromechanical properties of ITZs based on abundant indentation tests. [ABSTRACT FROM AUTHOR]

The porosity of concrete affects the durability of reinforced concrete structures, wherein high levels of porosity are linked to a shorter service life. Recent works have noted that high porosity levels naturally exist in the aftermath of a fire exposure - especially when concrete is classified as high strength concrete (HSC). To shed more light into this phenomenon, this paper showcases a method for measuring the porosity of HSC under elevated temperatures through scanning electron microscopy (SEM). In this method, SEMbased images were examined to quantify the surface porosity of fire-affected HSC. Detailed image analysis was performed for HSC exposed to various heating durations. The study concludes that the surface porosity obtained via the SEM processing method is in good agreement with that from the SEM-based method (with a minor average difference of 3.8%). As such, the proposed method is expected to be reliable for the porosity analysis of fire-damaged concrete. [ABSTRACT FROM AUTHOR]

This paper presents an evaluation study of crack limit states according to design codes and previous research. It aims primarily to relate research findings to design code similarities. Cracks in reinforced concrete structures are still a challenging problem for researchers, especially in one-way plate structures where there is still a lot of damage and corrosion in the reinforcement due to cracks. Finding the right formula will make it easier for practitioners to design these structures, and the problem of durability in reinforced concrete plates can be overcome. From this research, an approach is proposed on how to predict the maximum crack width formula in one-way reinforced concrete slabs with different thicknesses. Plates use a variety of thicknesses, including 125 mm, 150 mm, 175 mm, and 200 mm. The test specimens have the same dimensions and steel reinforcement, a slab width of 0.6 m and a length of 2 m. From a literature study of prediction formulas from previous research works and codes, namely wmax(prop)=7.5*10-3 fsh-0.333, it was found that thickness (h) has little influence on maximum crack width. The results from both approaches in this analysis are overall in accordance with the observed experimental tests and the proposed formula. Based on these observations, increasing the thickness of the reinforced concrete slab has significantly reduced the maximum crack width so that the experimental formula is obtained, namely wmax(exp)=0.32*fsh-1.113. Therefore, a constant is needed to evaluate the influence of thickness parameters for slabs with a thickness less than 200 mm on the maximum crack width formula for reinforced concrete slabs, and a special approximation formula has been obtained. In practical use, the crack width formula can only be used for one-way slabs [ABSTRACT FROM AUTHOR]

The moisture content within the concrete pore network significantly influences the mechanical, thermal, and durability characteristics of concrete structures. This paper introduces a novel fully embedded wireless temperature and relative humidity sensor connected to an automatic acquisition system designed for continuous concrete monitoring. Relative humidity measurements from this new sensor are compared with those obtained by a commercial system based on the borehole method at different depths (2.5 and 4.0 cm) and exposure conditions (oven drying and humid chamber). The results allow for proving that both systems provide consistent internal relative humidity measurements aligned with the exposure conditions and highlight the capability of fully embedded wireless sensors as a practical and reliable alternative to the conventional borehole method. Additionally, the continuous monitoring of the wireless cast-in sensor exhibits reliability during unintended temperature fluctuations, emphasizing the effectiveness of permanently installed sensors in promptly detecting unintended curing variations in real time. The continuous real-time information provided combined with the practicality of these sensors might assist construction managers to improve the quality control of the concrete curing process and shrinkage behavior, and ensure the integrity of concrete surface finishing. [ABSTRACT FROM AUTHOR]

Chloride ion corrosion has been considered to be one of the main reasons for durability deterioration of reinforced concrete structures in marine or chlorine-containing deicing salt environments. This paper studies the relationship between the amount of fly ash and the durability of concrete, especially the resistance to chloride ion erosion. The heat trend map of total chloride ion factor correlation displayed that the ranking of factor correlations was as follows: sampling depth > cement dosage > fly ash dosage. In order to verify the effect of fly ash dosage on chloride ion resistance, three different machine learning algorithms (RF, GBR, DT) are employed to predict the total chloride content of fly ash proportioned concrete with varying admixture ratios, which are evaluated based on R2, MSE, RMSE, and MAE. The results predicted by the RF model show that the threshold of fly ash admixture in chlorinated salt environments is 30–40%. Replacing part of cement with fly ash in the mixture of concrete below this threshold of fly ash, it could change the phase structure and pore structure, which could improve the permeability of fly ash concrete and reduce the content of free chloride ions in the system. Machine learning modeling using sample data can accurately predict concrete properties, which effectively reduce engineering tests. The development of machine learning models is essential for the decarbonization and intelligence of engineering. [ABSTRACT FROM AUTHOR]

The durability of concrete is critical for the service life of concrete structures, and it is influenced by various factors. This paper investigates the impact of the relative humidity (RH) of the curing environment on the durability of five different concrete types. The aim is to determine a suitable approach for designing concrete that is well-suited for use in the salt lake region of Inner Mongolia. The concrete types comprise ordinary Portland cement (OPC), high-strength expansive concrete (HSEC), high-strength expansive concrete incorporating silica fume, fly ash, and blast furnace slag (HSEC-SFB), steel fiber-reinforced high-strength expansive concrete (SFRHSEC), and high elastic modulus polyethylene fiber-reinforced high-strength expansive concrete (HFRHSEC). All these concrete types underwent a 180-day curing process at three distinct relative humidities (RH = 30%, 50%, and 95%) before being subjected to freeze–thaw cycles in the Inner Mongolia salt lake brine. The curing environment with a 95% RH is referred to as the standard condition. The experimental results reveal that the durability of OPC and HSEC decreases significantly with increasing relative humidity. In comparison with the control sample cured in 95% RH, the maximum freeze–thaw cycles for concrete cured in lower RHs are only 31% to 76% for OPC and 66% to 77% for HSEC. However, the sensitivity of the durability of HSEC-SFB, SFRHSEC, and HFRHSEC to variations in RH in the curing environment diminishes. In comparison with the corresponding reference value, the maximum freeze–thaw cycles for samples cured in dry conditions increase by 14% to 17% for HSEC-SFB and 21% for SFRHSEC. Specifically, the service life of HFRHSEC cured in a low RH is 25% to 46% higher than the reference value. The durability of HSEC-SFB, SFRHSEC, and HFRHSEC has been proven to be appropriate for structures located in the salt lake region of Inner Mongolia. [ABSTRACT FROM AUTHOR]

The widespread use of carpets in residential and commercial buildings and their relatively short life span result in large volumes of carpet being landfilled. A potential solution to this problem is the use of post-consumer carpet fibers in concrete. To this end, this paper systematically identifies the common fiber types in a typical post-consumer carpet fiber bale and evaluates their durability under exposure to varying levels of alkalinity. The tensile strengths and toughness of the fibers belonging to the nylon and polyethylene terephthalate (PET) families (the dominant fibers in most post-consumer carpets) are reduced by up to 50% following exposure to extreme alkalinity, the reasons for which are determined using spectroscopic and microscopic evaluations. The chloride ion transport resistance of concretes (~40 MPa strength) containing 2.5% carpet fibers by volume (~25 kg of fibers per cubic meter of concrete) is comparable to that of the control mixture, while mortar mixtures containing the same volume fraction of carpet fibers demonstrate negligible enhancement in expansion and loss of strength when exposed to 1 N NaOH. This study shows that moderate-strength concretes (~40 MPa) for conventional building and infrastructure applications can be proportioned using the chosen volume of carpet fibers without an appreciable loss of performance. Consideration of low volume fractions of carpet fibers in low-to-moderate-strength concretes thus provides a sustainable avenue for the use of these otherwise landfilled materials in construction applications. [ABSTRACT FROM AUTHOR]

The paper concerns destructive and non-destructive (NDT) evaluation of the effect of the addition of superabsorbent polymer (SAP) used as a carrier of mixing water and a means of internal curing on the durability of concrete. The research concerns testing of five concretes—an ordinary reference concrete and four concretes differing in the content of mixing water introduced into the concrete mix in the form of pre-saturated SAP particles (25%, two variants of 50% and 75% of the total mixing water in the form of SAP hydrogel). The research consisted of 4 stages of tests. The subsequent stages involved the analysis of the effect of using SAP as a carrier of mixing water on the particular characteristics of concrete mix and hardened concrete, i.e., consistency and density of concrete mix (1st stage), carbonation tested using two indicators—phenolphthalein and thymol phenolphthalein (2nd stage), and finally: the homogeneity of the concretes' structure by means of ultrasonic method (determination of ultrasonic pulse velocity) 28 days after production (3rd stage) and 3 years after production (4th stage). The ultrasonic pulse (or wave) velocity was then correlated with the content of water applied in the form of SAP hydrogel. The statistical analysis of results showed that the method of introducing the mixing water into the concrete mix in the form of pre-absorbed superabsorbent polymer, although it changed the concrete mix consistency, did not significantly affect the concrete ability to resist carbonation. Meanwhile, after 3 years, the densification of the microstructure of concrete with SAP has been observed. [ABSTRACT FROM AUTHOR]

The objective of this paper is to present the methodology used to validate the threshold levels of durability indicators from data acquired from existing reinforced concrete structures that may present corrosion problems resulting from carbonation or chloride ingress. This study was conducted in the framework of the French National Project PERFDUB in close collaboration with the MODEVIE ANR project. Durability tests form the basis of a performance‐based approach for the durability of concrete structures, and in order to set the threshold level for each of these durability indicators, it is important to take into account the experience feedback that can be obtained from the actual behavior of existing structures. This paper presents the investigations carried out on eight reinforced concrete structures, all of them having an age well in excess of 50 years, and the main data gathered on some relevant durability and lifetime indicators. Based on all these data, predictive models of carbonation and chloride penetration are applied in order to validate the threshold levels to be adopted for the durability indicators, and several other conclusions are drawn. [ABSTRACT FROM AUTHOR]

The present paper highlight upon research work is that curing is one of most important aspect of construction. The life of concrete and its serviceability depends heavily on curing. The method of curing applied on concrete will affect its final strength and durability. Owing to this fact this paper contains the research done on concrete under various curing methods. The standard method of curing concrete is done by water and results wastage of a lot of water. With the increase in the deficiency of availability of water, curing becomes a problem. Hence this research aims at providing better methods of curing which will not only improve the strength and durability of concrete but will also save water. The various methods that have been researched upon are plastic covered curing, addition of sodium silicate to curing water, and addition of curing compounds to curing water. The tests are carried on concrete with desirable strengths of M15 and M20. In this research the fine aggregate used in making of M15 and M20 concrete consists of a mixture of sand and crusher dust. Two mixes of ratio 50:50 and 60:40, sand to crusher dust have been taken and the effects of curing on these mixes are considered. Plastic curing is done by covering the concrete with plastic soon after demolding. Hence minimum water is required. The curing done by sodium silicate is done by adding 2% by weight of sodium silicate to curing water. Concrete is submerged in water containing sodium silicate. Once the concrete is cured, this water mix can be reused to cure freshly cast concrete, thereby saving more water. Curing by curing compounds is done in a similar way as that of curing with sodium silicate, only that instead of sodium silicate, curing compounds are used. The effect of these three methods on concrete is studied and discussions are made. [ABSTRACT FROM AUTHOR]

The RC structural elements are of the utmost significance in any structure to bear the loads and transfer, while concrete is a brittle material that can bear deformations to some extent. In order to withstand large deformations, various types of wrapping techniques have been introduced, and because of their high load bearing capacity, they have been widely used in RC structures. This review study focuses on the wrapping strategies that are appropriate for RC beam elements, as well as the nature of nano failure cracks. The construction can be earthquake resistant by adopting various wrapping techniques such as BFRP, CFRP, GFRP, AFRP, and so on. The RC beam subjected to various loads such as blast loads, dynamic loads are discussed in this paper. Wrapping approaches have developed as a viable solution for managing restrictions without requiring significant changes to the structural elements. Wrapping approaches are mostly focused on RC beam elements, and numerous methodologies are explored. [ABSTRACT FROM AUTHOR]

A large number of waste tires are discarded every year. These waste tires will have a great impact on the environment. If they can be recycled, environmental and economic benefits can be obtained. In this paper, rubber powder is added to concrete, and a variety of analytical methods are used to study the effect of rubber powder on the performance of concrete. Experiments show that the slump of concrete decreases with the increase of rubber powder substitution rate, and the rheological performance results show that the friction force increases with the increase of rubber powder substitution rate. The compressive strength of concrete decreases with the increase of substitution rate. The results of ICP show that rubber powder will adsorb cations to affect cement hydration. Nanoindentation shows that the addition of rubber powder leads to the decrease of high-density hydration products. The results of SEM-EDS show that rubber powder will affect the Si/Ca of hydration products. The results of UPV and MIP are similar. The hydrophobicity of rubber powder and the poor compatibility with hydration products are the key factors affecting the durability of concrete. Because the rubber powder only needs to be ground to avoid the related process of cement, it can obtain good economic and environmental benefits. In practical engineering, rubber powder can be added appropriately. [ABSTRACT FROM AUTHOR]

Recent research on self-healing concrete has shown some drawbacks and conflicts between the different techniques such as difficulty in casting, healing agent release, preparation complexity, high safety requirements against bacteria protection, undesirable expansion, and uncertainty in healing product generation. Despite these limitations, the hybrid technique was suggested and showed promising results. This paper explores the hybridization of the two techniques; autonomous and autogenous by utilizing the B. subtilis bacteria, mineral admixtures like fly ash, and polyvinyl alcohol fibers (PVA) together. The experimental program involves assessing the self-healing efficiency when coupling the bacteria, fly ash, and PVA fiber by assigning six mixtures, including a control OPC. The six mixtures encountered the bacteria addition at certain concentrations and varying PVA fiber percentages; 1, 1.5, and 2% while partially replacing the cement replacement with 20% fly ash, while the last mixture combines both the bacteria, fly ash, and 1% PVA fiber. Mechanical properties such as compressive and flexural strength, in addition to, water absorption and sorptivity as transport properties were examined for concrete repair and restoration purposes. The results reveal that the B. subtilis bacteria significantly enhance the compressive and flexural strength recovery along with lowering sorptivity and absorption rate compared to those with PVA addition when exposed to wet and dry cycles of curing at 28 days of age. The coupling effect, on the other hand, provides a substantial gain in strength of 63% at a longer age (56 days), indicating the potential of this approach for long-term concrete repair. Despite the challenges of the B. subtilis survival bacteria, the coupling of both bacteria and PVA fiber demonstrates superior performance in maintaining the durability of repaired concrete in the long term. [ABSTRACT FROM AUTHOR]

The durability of concrete structures, which are designed for long- -term use is predominantly determined by the resistance to chemical influences, i.e., the concrete's ability to protect the reinforcement steel. The carbonation and the chloride ingress into concrete are the most significant causes of steel corrosion and the potential failure of the structure. The primary goal is to ensure that any significant damage does not occur during the structure's service life, primarily achieved by selecting an adequate thickness of the concrete cover. The issue is approached through calculations based on performance analyses, and the use of appropriate models for these chemical phenomena. The paper provides a brief overview and the methodology for analysing the impact on the durability of concrete structures in accordance with the leading international normative documents. The emphasis is on the recent changes introduced in second generation of European Eurocode standards. The consequences of the analysed phenomena are presented through the results of field tests conducted at salt factories, coke industries, and thermal power plants, and through laboratory tests. The tests were performed in order to develop a rapid prediction method for the measure of chloride ingress into concrete without the stimulating chloride ion migration by electricity, as an alternative to standardized tests. [ABSTRACT FROM AUTHOR]

Durability plays a crucial role in maintaining the service life of a structure. This paper focuses on examining the durability of a building with a reinforced concrete structure that has been exposed to an offshore environment for 35 years. The study involved on-site inspections to assess external damage, including testing parameters such as the compressive strength of the concrete material and the overall tilt of the building. Additionally, microscopic inspection techniques, such as X-ray fluorescence (XRF), thermogravimetry-differential scanning calorimetry (TG-DSC), X-ray diffraction (XRD), and scanning electron microscopy (SEM), were employed to analyze the corrosion products and microstructure associated with the damage mechanism. Based on the data obtained from the on-site inspections, structural calculation software was used to calculate and verify the overall load-bearing capacity of the building, aiming to determine its safety level. The evaluation results revealed severe safety issues within the building, despite it not having reached its designed service life, particularly in relation to reinforcement corrosion. [ABSTRACT FROM AUTHOR]

Carbonization is the main cause of corrosion and decrease in bearing capacity of internal steel bars in concrete structures. Conducting durability assessment and remaining life prediction for existing railway bridges is of great significance for their subsequent maintenance and reinforcement. This paper evaluated the durability of several prestressed concrete beams in experimental railway super large bridges, and tested their concrete strength, carbonization depth, and protective layer thickness. Combined with measured data and durability models, the remaining durability life of the bridge was predicted. The results show that the average strength of prestressed concrete with a service life of 32 years is around 38.5 MPa, and the average carbonization depth is around 10 mm. Compared to the flange and web plates, the actual thickness of the protective layer at the bottom of the beam is relatively small, and the probability of corrosion of the internal steel bars here is higher. The durability model based on in-situ testing and carbonation depth correction indicates that the bottom of the prestressed beam began to experience steel corrosion after 29.5 years of service. Finally, based on the durability criterion of 7% critical steel corrosion rate, the service life of different parts of the prestressed bridge was predicted. [ABSTRACT FROM AUTHOR]

• An original multielectrode embedded capacitive sensor is developed. • Multielectrode embedded capacitive sensor allows to assess permittivity in concrete. • Optimum dimensions chosen for capacitive electrodes are rectangular 30 × 10 mm2. • Measurements in liquids and concrete show a very repeatable and reproducible system. • Permittivities obtained with the developed embedded sensor are validated. This paper discusses the development of a capacitive sensor embedded within concrete blocks in order to continuously monitor water content, which is a crucial parameter in the assessment of concrete degradation. The embedded capacitive sensor undergoes continuous interrogation by an automatic monitoring system, in order to track permittivity changes over time through a frequency measurement system. The methodology involves a two-step calibration process: first, obtaining permittivity from frequency, then converting permittivity profiles into water content profiles. This paper focuses on the sensor design and first calibration in the aim of assessing permittivity profiles. Numerical methods enable optimizing both electrode geometry and design of the embedded capacitive sensor. Experimental validation of the sensor in liquid and concrete environments, along with a metrological validation, reveals the sensor's ability to monitor permittivity profiles as well as its uncertainty at 8 different depths inside the concrete structure. Permittivity measurements were also conducted using reference methods. The results demonstrate very good agreement with less than 10% difference between the embedded sensor and the reference results. This step provides insights into its applicability and potential perspectives for future research. [ABSTRACT FROM AUTHOR]

Experiments and field observations have shown that supplementary cementitious materials (SCMs) mitigate the risk of alkali-silica reaction (ASR) in Portland cement blends, but this is difficult to describe thermodynamically due to the lack of appropriate thermodynamic database information, and challenges in defining the kinetic factors. This paper examines how four well-known SCMs (namely ground granulated blast furnace slag, silica fume, metakaolin, and fly ash) mitigate ASR, by using a multi-stage simulation and a newly extended thermodynamic database. Calcium hydroxide consumption by SCM hydration, dilution of available alkalis, and alkali binding in calcium-alkali-aluminosilicate hydrate solid solutions, play pivotal roles in understanding the influence of SCMs in ASRs. Blending aluminium-rich SCMs in ASR-prone systems appears to act by preventing the dissolution of reactive silica in aggregates rather than by suppressing the formation of ASR products. This paper provides new thermodynamic insights into the mechanisms by which SCMs enhance concrete durability against ASR. [ABSTRACT FROM AUTHOR]

Glass Fiber-Reinforced Polymer (GFRP) bars can enhance the flexural bearing capacity and durability of concrete beam members under sustained loading and alkaline environment over an extended period. However, addressing the challenges related to durability and deformation resistance remains crucial for long-term service. In this paper, the flexural performance of GFRP-reinforced concrete beams with different glass fiber contents under the coupling action of the alkaline environment and continuous load is studied, and the mechanism of improving the flexural performance of GFRP-reinforced concrete beams by dispersed fibers is analyzed from a microscopic point of view by scanning electron microscope (SEM) test. In addition, the finite element analysis software was used to simulate and verify the improvement effect of singly dispersed fiber on the bending of GFRP-reinforced concrete beams. The results demonstrate that GFRP-RC beams containing 0.5%, 1.0%, or 1.5% glass fiber exhibit a reduction in deflection ranging from 11% to 23% compared GFRP-RC beams without glass fiber, thereby improving their deformation resistance. The optimal glass fiber content is 1.5%. Simulation analysis demonstrates that the model exhibits enhanced resistance to deformation when the glass fibers are randomly dispersed. Specifically, increasing the random scattering of fibers at the bottom of the beam by two to three times results in a reduction of 7%-12% in mid-span displacement of the model. Additionally, within the cracked area, the fibers bear greater tensile stress compared to those in other uncracked regions, effectively preventing further cracking of GFRP-RC beams. This study offers valuable design guidance for enhancing performance of GFRP-RC members during long-term service. • This paper studied glass fiber GFRP-RC beams. • The working condition is the coupling of sustained loading and alkaline environment. • The influence of fiber on the flexural property of beam was investigated by finite element method. • The corrosion age of alkaline environment is 450 d. [ABSTRACT FROM AUTHOR]

This paper presents a study on the durability testing of a concrete facility located within the North Bay Port region, which has been in service for 200 months. Based on the results of 20 sets of concrete samples, an improved Kolmogorov-Smirnov (K-S) test method and gross error discrimination method are proposed to analyze the random distribution functions of the apparent chloride diffusion coefficient (D app) and the apparent surface chloride concentration (C s), and further explore the time-varying characteristics of chloride ion transmission in concrete. The research shows that the improved K-S method presented in this paper can effectively reduce the probability of type II errors by selecting a rational sample size, which can also improve detection efficiency. When the sample size does not exceed 10, the 2 σ criterion proposed in this paper can effectively identify and eliminate gross errors. In general, D app and C s follow the log-normal distribution, while the time factor (m) follows a normal distribution parameter. The value of C s basically stabilized after exposure to 80 months, whereas D app tended to stabilize after exposure to 100 months. The value of m obtained through fitting short-term experimental data is typically overestimated, and its value decreases as the exposure time prolongs. Therefore, m should also be considered a time-varying parameter that decreases with time. The tested RC structure will begin to experience rebar corrosion after 48.5–60 years of exposure to the marine environment based on the probabilistic assessment. • The 2 σ criterion was introduced to identify and rectify significant errors. • The improved K-S method was developed to minimize the likelihood of type II errors. • Chloride profiles were extracted from 200 months aged harbor concrete structures. • Both D app and C s demonstrated a good fit with the log-normal distribution. [ABSTRACT FROM AUTHOR]

The use of corrosion inhibitors for steel rebar in concrete is one of the best-demonstrated methods to mitigate the corrosion process and extend the service life of reinforced concrete structures exposed to chloride laden environment. However, the research progress on corrosion inhibitors for reinforcing steel is slow and classical, as the traditional experimental methods revealed. Recently, the application of computational methods, such as density functional theory (DFT) and molecular dynamics (MD) simulation, to corrosion research has become an essential area for gaining more insights into the detailed mechanisms of corrosion as well as identifying ways and means of technological innovation. This paper presents a systematic review of the research progress and advances in the molecular simulation of corrosion inhibitors for steel in concrete. The DFT calculations conducted on different inhibitor molecules were reviewed, and the related theoretical chemical reactivity parameters along with the donor-acceptor process were discussed. In addition, the MD simulations of various molecule/surface adsorption systems were studied, considering different steel substrates. The valuable insights gained from the computational models were introduced and consolidated into the experimental inhibition efficiency. Finally, the challenges and future perspectives of the research topic are highlighted. This paper is believed to promote the utilization of theoretical methods in corrosion research of reinforcing steel for a deep understanding of the corrosion process at the atomic level and innovative design of corrosion-resistance materials. [Display omitted] • Atomistic modeling and simulation of corrosion inhibitors for reinforcing steel are reviewed. • Research progress and advances are highlighted. • Theoretical reactivity parameters and adsorption behavior are correlated to experimental inhibition efficiency. • Molecular modeling provides a fundamental understanding of the corrosion mechanism. • Computational methods can derive the innovation process for corrosion-resistance materials. [ABSTRACT FROM AUTHOR]

The disposal of steel slag in landfills not only squanders precious landfill resources but also results in significant environmental contamination. Steel slag can be used to replace cement and natural aggregates in concrete. Nonetheless, utilizing untreated steel slag directly presents a substantial hazard to the structural characteristics and durability of concrete. To avoid this problem, study on accelerated carbonation of steel slag as construction materials has been extensively conducted. This review paper begins by introducing the classification and physicochemical properties of steel slag; it then describes the typical approaches of steel slag carbonation, including direct carbonation (dry carbonation, wet carbonation) and indirect carbonation (pH-swing, microbial carbonation), along with their processes and carbonation mechanisms. Furthermore, based on the reviewed literature, the influences of various reaction parameters such as reaction time, liquid-to-solid ratio, temperature, additives, CO 2 concentration, pressure, pH on carbonation effectiveness are analyzed. Also, the impact of carbonated steel slag on the micro-pore structure, stability, workability, and mechanical properties of concrete is discussed. Finally, the challenges and future work of using carbonated steel slag as construction materials are provided. • The current papers on steel slag classification, physicochemical properties, and methods for accelerated carbonation are reviewed. • The traditional carbonation methods, as well as recently proposed microbial carbonation methods are analyzed. • The factors influencing the efficiency of steel slag carbonation are summarized. • The impact of carbonated steel slag on concrete properties are concluded. • Insights into accelerated carbonation methods for steel slag and future work are provided. [ABSTRACT FROM AUTHOR]

The corrosion of reinforcement embedded in concrete caused by chloride attack is the main factor leading to the durability failure of reinforced concrete (RC) structures. A novel method of embedding diaphragm to effectively delay the corrosion of reinforcement is proposed in this paper. Furthermore, the mechanism of the diaphragm hindering chloride diffusion is revealed and the shape of the diaphragm is optimized and designed through numerical simulation. The results show that the diaphragm can effectively delay the accumulation of chloride on the surface of reinforcement, and the geometry of diaphragm has a great influence on the delay effect, and the best geometry is semicircular. Mover, the radius of diaphragm and the distance between diaphragm and reinforcement surface have nonlinear effects on the service life of reinforced concrete. The diaphragm configuration proposed in this paper provides a novel idea to solve the problem of reinforcement corrosion caused by chloride attack. • A novel method of embedding diaphragm is proposed to effectively delay the corrosion of reinforcement. • The mechanism of diaphragm blocking chloride transport is revealed through chloride transport streamline. • The geometry of each diaphragm is optimized to determine the best shape of the diaphragm. [ABSTRACT FROM AUTHOR]