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This study aimed to address the critical issue of age deterioration in prestressed concrete (PSC) structures by investigating the strengthening of aged PSC structures using a near-surface mounted (NSM) post-tensioned carbon fiber-reinforced polymer (CFRP). A total of nine PSC beams, each with a length of 6.5 m, were fabricated for a four-point bending test. Various experimental parameters were taken into account, including the strengthening method, compressive strength of concrete in the PSC beam, and the prestressing force of the PSC beam. The results indicated that the NSM post-tensioned CFRP strengthening system proved more efficient when compared to the NSM non-post-tensioned CFRP strengthening system. The flexural capacity of the NSM post-tensioned CFRP strengthening system, under the deteriorated low-strength PSC beam, increased by up to 30.9% compared to the PSC reference beam. Additionally, the experimental results were compared to a finite-element analysis, and a parametric study was conducted to examine the material properties of the PSC beam. Consequently, the NSM post-tensioned CFRP strengthening system is expected to be an effective solution for addressing the issue of deteriorated low-strength PSC structures. [ABSTRACT FROM AUTHOR]

This paper describes the first ever reported case in Brazil where delayed ettringite formation (DEF) has been confirmed as the sole cause of deterioration in field concrete. Still under construction and less than 2 years old, numerous cracks were observed in the foundation structures of a building located in Recife, a city known for its history of alkali–aggregate reaction (AAR) cases. In addition to a field survey of cracks, microstructural analyses, tests for residual expansion and compressive strength, a review of the structural design, determination of sulfate content in the groundwater and simplified thermal analysis were carried out. The results confirmed that DEF was the sole cause of the damage present in cast-in-place concrete structures, with no evidence of AAR or any other deterioration process. This work corroborates previously published studies on the high risk of the occurrence of DEF in the region, demonstrating the urgent need for a preventive technical standard in the country, considering the chemical composition of cements and prior thermal analyses to adopt possible preventive measures to limit the maximum internal temperature of concrete. [ABSTRACT FROM AUTHOR]

The high-salinity environments in salt lakes can significantly affect the durability of reinforced concrete. However, there needs to be more reports on the corrosion characteristics of the rebars under salt lake environments, which play a crucial role in studying the deterioration of concrete structures. This study meticulously investigated how temperature variations and changes in water-cement ratios affect the corrosion of rebars in high-salinity lake water conditions, which not only supplements the existing research gap in salt lake conditions but also offers insights for predicting the service life of concrete structures under such circumstances. Reinforced concrete specimens with water-cement ratios of 0.49, 0.54, and 0.60 were tested in both the atmospheric zone and dry–wet cycling zone at temperatures of 15 °C, 30 °C, 35 °C, and 40 °C. A three-electrode system was utilized to monitor the corrosion potentials of the rebars, while the linear polarization method was employed to determine the polarization resistance. The time to corrosion initiation, threshold chloride concentration, and corrosion current density were determined and discussed. The results indicated that temperature and salinity did not significantly affect the corrosion potentials of rebars. However, corrosion initiation occurred much faster under salt lakes than in marine environments, with initiation times averaging around 100 days. Furthermore, it was found that the corrosion rate tended to increase as the temperature and water-cement ratio increased. Additionally, the rebars in the atmospheric zone exhibited lower threshold chloride concentration than those in the dry–wet cycling zone at temperatures of 30 °C, 35 °C, and 40 °C, and higher temperatures corresponded to more significant differences in threshold chloride concentration between the two zones. Lower water-cement ratios were shown to delay corrosion initiation and increase the threshold chloride concentration, suggesting the effectiveness in mitigating rebar corrosion in high-salinity environments. [ABSTRACT FROM AUTHOR]

Laser-induced breakdown spectroscopy (LIBS) is a powerful elemental detection and quantification technique widely employed across various disciplines, including science, engineering, construction, and medicine. This comprehensive review focuses on the recent advancements and challenges in utilizing LIBS for corrosion detection, specifically emphasizing reinforced concrete structures. While LIBS has demonstrated its reliability in corrosion assessment, its adoption as a standardized method is not yet widespread. Identifying and quantifying contaminant elements in targeted structures are crucial steps in corrosion investigation. This review reveals how LIBS can effectively extract elemental contaminants and their relative intensities from samples, establishing correlations with the degree of corrosion. Given that corrosion rate is time-dependent, rapid and accurate techniques like LIBS are essential for timely measurements, enabling multiple instantaneous assessments of contaminant levels. Various calibration techniques and accuracy-enhancing methods are discussed, including calibration curves, chemometrics, and dual-pulsed LIBS approaches for measuring constituent elements. Furthermore, a range of applications for LIBS in concrete technology, cement paste analysis, soil investigations, fluid analysis, and quality control in cement factories are explored. By providing an in-depth understanding of LIBS capabilities and its potential as a reliable and rapid approach for corrosion rate detection in different materials, this study offers valuable insights to researchers, engineers, and industry professionals in pursuing effective corrosion assessment methodologies. [ABSTRACT FROM AUTHOR]

This article provides information on ettringite, a hydrated calcium sulfoaluminate mineral that belongs to the ettringite group. It describes the physical characteristics of ettringite, such as its hexagonal, prismatic crystals and color variations. The article also mentions the origins of the name ettringite and its cotype localities in the Ettringen district of Germany. Additionally, it discusses the village of Ettringen and its association with outdoor activities like rock climbing in basalt quarries. The article further explores the Bellerberg volcanic lava flows and their use in manufacturing querns and millstones. It highlights the Kalahari manganese field in South Africa as the primary natural locality for ettringite specimens, with larger crystals than any others known. The article focuses on the identification and properties of yellow ettringite found in the Kalahari manganese field, emphasizing the challenges in visually distinguishing it from other minerals in the area. It also delves into the role of ettringite in the deterioration of concrete and its stability under different conditions. The research for this article was funded by the National Research Foundation and CIMERA. [Extracted from the article]

Water utilities are facing significant challenges, such as supplying, with less water resources, more and more water due to population growth, amid the current scenario of climate change. In this context, urban water systems represent a crucial component of global public infrastructure for water utilities, with municipalities entrusted with the responsibility of managing and enhancing them for both current and future generations. The main challenge arises when these infrastructures inevitably age and deteriorate, significantly increasing water losses. Since it is unrealistic and unnecessary to rehabilitate and/or replace all pipes in an existing water distribution system, this manuscript is focused on identifying the independent key parameters which can be used to detect reinforced concrete pipe deterioration. To this end, the variables that affect mechanical properties are narrowed down, and the most significant factors crucial for pipe failure are identified. In this process, reinforced concrete pipe samples were collected to characterize them based on a set of potential key parameters. All potential key parameters were analyzed, with the objectives of identifying which key parameters were significant for the model and determining the interactions among them. All data were stored in a dataset which was used to generate a predictive model to estimate average concrete strength and pipe condition assessment versus independent key parameters. The predictive model, utilizing a design of experiments (DoE) and based on the analysis of variance (ANOVA), could estimate the average concrete strength with an accuracy of around 90%, and the external porosity was found to be the main factor. On the other hand, it was also possible to estimate a range of porosity values for the purpose of maintaining the reinforced concrete pipe in optimal condition. [ABSTRACT FROM AUTHOR]

This paper presents experimental testing evaluating the ability of a bridge deck deicing system to mitigate concrete deterioration from thermal stresses, frost action, and early-age cracking. Two experimental bridge deck models were constructed with embedded heat exchanger tubing and instrumented with thermocouples and strain gauges. Model 1 evaluated the efficiency of a deicing system in deicing and mitigating concrete deterioration from thermal stresses and frost action in concrete bridge decks, while Model 2 tested the effect of a deicing system on early-age cracking in bridge decks. The models were tested in a cold chamber laboratory under conditions representative of Montana's winter weather, with the system circulating warm fluid through the decks. Results showed the system succeeded in increasing concrete temperatures at all depths. While the system did not always raise temperatures above freezing, the consistent increases suggested that the system could enable deicing and mitigate frost action given certain conditions and higher inlet fluid temperatures. The system also successfully decreased thermal movement strain by up to 40% and reduced thermal shrinkage by decreasing the difference between peak cured and stabilized temperatures. Although the system did not eliminate thermal gradients, the maximum gradient induced was insignificant. Further testing is needed on strength impacts. Overall, the deicing system showed promise to reduce thermally induced deterioration in concrete bridge decks by regulating temperatures. [ABSTRACT FROM AUTHOR]

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Freeze–thaw damage significantly contributes to the degradation of concrete structures. A critical precondition for concrete to experience frost damage is reaching its critical saturation level. This study conducted freeze–thaw experiments on concrete specimens under both open and sealed moisture conditions to elucidate the mechanisms of freeze–thaw damage and the pivotal role of moisture. The research assessed concrete's water absorption, ultrasonic pulse velocity, and compressive strength under restricted water conditions to study damage accumulation patterns. The findings indicate that implementing water limitation measures during freeze–thaw cycles can regulate concrete's water absorption rate, reduce the loss of ultrasonic pulse velocity, and minimize strength degradation, with an observed strength increase of up to 36.22%. Consequently, these measures protect concrete materials from severe frost damage. Furthermore, a predictive model for concrete freeze–thaw deterioration was established based on regression analysis and relative dynamic modulus theory, confirming the critical role of water limitation in extending the service life of concrete structures in cold regions. [ABSTRACT FROM AUTHOR]

The freeze–thaw effect has a significant impact on the strength deterioration of tunnel-lining concrete in cold regions. Therefore, the strength deterioration characteristics of concrete in a tunnel were studied, and silicone coating materials were used to improve its frost resistance and durability under freeze–thaw cycles. Freeze–thaw cycle tests were conducted on concrete specimens with different coatings. The freeze–thaw damage phenomenon, dynamic elastic modulus, and mass loss of the specimens were used to evaluate the freeze–thaw durability of concrete strengthened with coatings. The results demonstrated that silicone coatings effectively prevented moisture and corrosive substances from infiltrating the concrete, thereby enhancing its durability; the silicone–polyether hybrid had the most significant frost resistance at 500 g/m2 and silane type III at 300 g/m2, with freezing resistance times of 175 and 300, respectively. During the freeze–thaw process, the strength reduction rate of specimens was much greater than the mass loss rate of concrete. Taking into account the water environment surrounding the lining concrete and the site temperature, an equivalent indoor freeze–thaw cycle conversion model was established. The results can provide an experimental basis for selecting better frost-resistant materials for tunnel concrete in cold regions. [ABSTRACT FROM AUTHOR]

An investigation into the effects of external sulfate attack (ESA) on the mechanical and microstructural properties of steel fibre-reinforced sprayed concrete (SFRSC) was conducted. Crimped carbon steel fibres, 40 mm long, were used as reinforcement in three different mixtures with specified fibre contents of 30, 60 and 90 kg/m3. Cylindrical specimens, drilled from SFRSC panels, were subjected to sulfate attack for up to 270 days. Double-punch tests were used to determine the matrix crack strength and the post-crack tensile strength of the SFRSC. The effective fibre content of each specimen was determined by inductive tests and subsequently correlated with the mechanical results. Scanning electron microscopy was used to evaluate the phases formed in the concrete pores during the ESA. The results showed that fibre reinforcement may reduce cracking due to ESA. [ABSTRACT FROM AUTHOR]

This study aims to enhance the durability, cost-effectiveness, and sustainability of recycled fine aggregate concrete (RFAC) subjected to the combined effects of wet-dry cycles and sulfate erosion. Dry–wet cycle tests were conducted in RFAC with different admixtures of biotite metakaolin (MK) and 15% fly ash (FA) mix (M) under 5% sulfate erosion environment. The effect of 0%, 30%, 60% and 90% recycled fine aggregate (RFA) replacement of natural fine aggregate on mass loss, cubic compressive strength, relative dynamic modulus test of RFAC, damage modeling and prediction of damage life of concrete were investigated. The results showed that the concrete cubic compressive strength and relative dynamic modulus were optimal for recycled concrete at 15% MK biotite dosing and 60% RFA substitution, and its maximum service life was accurately predicted to be about 578 cycles under 5% sulfate dry–wet cycling using Weibull function model. This study is pioneering in addressing the durability of RFAC under sulfate attack combined with wet-dry cycling, employing a novel approach of incorporating MK and FA into RFAC. The findings highlight the practical application potential for using MK and FA in RFAC to produce durable and sustainable construction materials, particularly in sulfate-exposed environments. This research addresses a critical challenge in the construction industry, providing valuable insights for developing more durable and eco-friendly construction materials and contributing to long-term sustainability goals. [ABSTRACT FROM AUTHOR]

Corrosion-induced concrete cracking is a significant stage of structural deterioration in prestressed concrete (PC) structures. Most current research predominantly focuses on the corrosion of prestressed steel strands, while paying limited attention to the study of non-prestressed reinforcement corrosion. In this study, an integrated material-structural numerical approach was developed to simulate corroded PC beams, considering corrosion products migration in pores and cracks. The cracking patterns and prestress losses obtained from the simulation results agreed well with experimental observations. Subsequently, using the proposed numerical approach, the interaction mechanism of the prestress level and reinforcement corrosion was investigated. The simulation results indicated that corrosion of longitudinal reinforcement leads to cross-sectional damage, causing the redistribution of stress across the section and increasing long-term deformation, ultimately resulting in prestress losses. Meanwhile, stirrup corrosion leads to an initial increase in prestress due to expansion forces when the degree of corrosion is not so high, but finally it will also lead to a degradation of mechanical performance. [ABSTRACT FROM AUTHOR]

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]

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]

The durability of concrete under combined acidic exposure and flexural loading was studied. Concrete specimens were made and subjected to up to 168 days of exposure to flexural loading (stress levels of 0, 0.35 and 0.50 of the 28 day flexural strength) and an acidic environment. Concrete properties such as neutralisation depth, mass change, compressive strength and flexural strength were measured. The compositions of different samples were determined by means of X-ray diffraction and chemical analysis and the microstructure of samples was examined using scanning electron microscopy. The results showed that, with an increase in stress level from 0 to 0.50, the performance of the concrete deteriorated gradually and the deterioration in the tension zone was greater than that in the compression zone. The concrete performance improved within 28 days but deteriorated dramatically afterwards. The acidic solution reacted with the cement paste, leading to the formation of harmful gypsum and the decomposition and dissolution of cement hydration products. An increase in stress level increased the porosity of the concrete, accelerating the rate of acid erosion, which led to a deterioration of concrete performance. [ABSTRACT FROM AUTHOR]

Cracks in concrete structures are unavoidable, resulting in the deterioration of concrete structures. An effective way to heal cracks, integrated with a suitable monitoring method, is of great significance. This research explores and demonstrates the autonomic healing and simultaneous ultrasonic monitoring of thin cracks using silica-based chemical agents. The sensitivity of ultrasonic waves to the change in the elastic properties of the medium through which it propagates is used to monitor the progressive healing of cracks in concrete. An increase in the ultrasonic pulse transmission (UPT) signal strength with the progression of healing in cracked concrete was used to interpret the condition of the crack. The ultrasonic results were validated by visual observations, an increase in compressive strength and a reduction in water permeability. Further, the efficacy of silica-based chemical healing agents in crack-healing concrete was also verified by microstructural scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) tests. The study successfully demonstrates the efficacy of sodium silicate as an effective chemical healing agent in cementitious materials, with the healing process well picked up by ultrasonic pulse transmission measurements. Practical Applications: The results of the study indicate that the utilization of sodium silicate as a healing agent in civil structures, integrated with the nondestructive monitoring of the healing process using the ultrasonic pulse transmission technique, represents an innovative approach to enhancing the durability and sustainability of concrete structures. Some practical applications include the following (1) the strength and life span of concrete bridges can be improved by integrating a crack repairing system with sodium silicate and monitoring through ultrasonic methods; (2) a sodium silicate solution can be injected into masonry substrate and mortar joints of historical buildings where cracks and weathering action have compromised the structural stability, and ultrasonic transducers can be strategically placed to monitor the healing progression and restoration process; and (3) this technique can be used to improve the resilience of marine structures by using sodium silicate as a healing solution in underwater concrete structures and combining it with ultrasonic monitoring. [ABSTRACT FROM AUTHOR]

Concrete bridge decks are critical transportation infrastructure components where deterioration can compromise structural integrity and public safety. This study develops machine learning (ML) models using the National Bridge Inventory (NBI) to classify deck conditions and predict deterioration trajectories. Models were tested and trained on inspection records from over 28,786 bridges in Michigan over 23 years, from 1992 to 2015. Eleven approaches were evaluated after hyperparameter optimization, based on 10-fold cross-validation, including logistic regression, gradient boosting, AdaBoost, random forest, extra trees, K-nearest neighbors, naive Bayes, decision tree, LightGBM, CatBoost, and bagging. Model effectiveness was assessed using accuracy, recall, F1-score, and area under the curve. Results indicate the optimized CatBoost classifier achieved 96.66% testing accuracy in rating deck conditions. The incorporation of hyperparameter optimization has significantly enhanced the overall predictive performance of the models, ensuring robust and reliable deterioration forecasting. The research sheds light on crucial factors such as deck age, area, and average daily traffic, contributing to a more comprehensive understanding of the factors influencing bridge deck condition ratings. These insights inform preventative maintenance planning to extend service life. This work pioneers a data-driven framework to forecast concrete deterioration, empowering officials with precise predictions to optimize infrastructure management under budget constraints. The approach provides a promising decision-support tool for sustainable infrastructure. This paper explores the use of machine learning techniques for the deterioration prediction of concrete bridge decks to estimate the remaining service life of bridges. These models will contribute to the safety, efficiency, and sustainability of bridge infrastructure by providing timely information and evidence-based decision making for bridge maintenance and management. Such prediction models have several practical applications such as (1) predicting when maintenance or repairs are likely to be needed; (2) assessing the risk of failure or deterioration of different components of a bridge; (3) effectively managing the bridge life cycle by providing insights into the aging process and helping authorities plan for rehabilitation or replacement strategies; (4) enabling ongoing monitoring of the performance of a bridge under various conditions such as heavy traffic loads, environmental factors, and seismic events; and (5) assisting in effective asset management by allowing for the prioritization of investments, the efficient allocation of budgets, and the planning for the long-term sustainability of the bridge infrastructure. [ABSTRACT FROM AUTHOR]

This work addresses a critical issue: the deterioration of concrete structures due to fine-grained cracks, which compromises their strength and longevity. To tackle this problem, experts have turned to computer vision (CV) based automated strategies, incorporating object detection and image segmentation techniques. Recent efforts have integrated complex techniques such as deep convolutional neural networks (DCNNs) and transformers for this task. However, these techniques encounter challenges in localizing fine-grained cracks. This paper presents a self-supervised 'you only look once' (SS-YOLO) approach that utilizes a YOLOv8 model. The novel methodology amalgamates different attention approaches and pseudo-labeling techniques, effectively addressing challenges in fine-grained crack detection and segmentation in concrete structures. It utilizes convolution block attention (CBAM) and Gaussian adaptive weight distribution multi-head self-attention (GAWD-MHSA) modules to accurately identify and segment fine-grained cracks in concrete buildings. Additionally, the assimilation of curriculum learning-based self-supervised pseudo-labeling (CL-SSPL) enhances the model's ability when applied to limited-size data. The efficacy and viability of the proposed approach are demonstrated through experimentation, results, and ablation analysis. Experimental results indicate a mean average precision (mAP) of at least 90.01%, an F1 score of 87%, and an intersection over union threshold greater than 85%. It is evident from the results that the proposed method yielded at least 2.62% and 4.40% improvement in mAP and F1 values, respectively, when tested on three diverse datasets. Moreover, the inference time taken per image is 2 ms less than that of the compared methods. [ABSTRACT FROM AUTHOR]

The integration of steel fibers into high-strength concrete (HSC) offers a solution to address the brittleness and limited ductility typically associated with conventional HSC structures. To investigate the bonding properties between shaped steel and high-strength concrete with steel fiber (SFRC), thirteen tests of the shaped steel/SFRC specimens are conducted to explore the effects of various factors such as steel fiber volume ratio, concrete strength grade, reinforcement ratio, steel embedment depth, and cover thickness on bond–slip behavior. Three distinct failure modes, such as pushout failure, bond splitting, and yielding failure of steel, are identified during the pushout tests. Three different types of bond strength, such as the initial bond strength, the ultimate bond strength, and the residual bond strength, are observed from the load–slip curves between the shaped steel and concrete. By incorporating nonlinear spring elements, a numerical model for accurately simulating the bond performance between the shaped steel and SFRC specimens is developed. The bond strength between the shaped steel and concrete increase as the concrete strength, cover thickness, steel fiber volume ratio, and stirrup ratio increase, while it decreases as the steel embedment depth increases. A model for the bond strength between shaped steel and SFRC is developed, and it agrees well with the test data. [ABSTRACT FROM AUTHOR]

The backfill area of tunnel projects may deform or collapse due to the cyclic disturbance of groundwater and train loads. Hence, the anti-deformation and crack resistance performance of backfill materials under cyclic disturbance is critical to engineering safety. In this paper, concrete was produced by mixing 0.85 mm, 1–3 mm and 3–6 mm rubber particles instead of 10% sand, and tested to discuss the effect of rubber particle size on the deterioration of concrete material properties (compressive characteristics and energy dissipation) after bearing cyclic loading. The stress–strain curve and various parameters obtained through the uniaxial compression test and cyclic load test were used to explore the optimal grain size that can be applied to the tunnel engineering backfill area, and numerical simulation was adopted to calculate the deformation of the surrounding rock and the structural stress of different backfill materials. Research shows that the increase in particle size lessens the compressive strength, deformation resistance and cracking resistance of specimens, but after the cyclic loading test, the concrete material deterioration analysis indicates that rubber concrete has lesser and more stable losses compared to ordinary concrete, so the optimum rubber particle size is 0.85 mm. Numerical calculations show that RC-1 reduces the arch top displacement by 0.4 mm, increases the arch bottom displacement by 0.6 mm and increases the maximum principal stress by 11.5% compared to OC. Therefore, rubber concrete can ensure the strength and stability requirements of tunnel structures, which can provide a reference for similar projects. [ABSTRACT FROM AUTHOR]

The poor early shrinkage and cracking performances of manufactured sand concrete, waste powder concrete, and recycled aggregate concrete are the main difficulties in engineering applications. To solve these problems, early shrinkage and cracking, strength, and impermeability tests were performed on high-volume stone powder manufactured sand concrete mixed with fly ash and slag powder (FS), a shrinkage-reducing agent (SRA), polyvinyl alcohol (PVA) fibers, and a superabsorbent polymer (SAP). Furthermore, the microstructures and pore structures of these concretes were revealed using nuclear magnetic resonance (NMR) and scanning electron microscopy (SEM). The results showed that the mixture of FS, SRA, PVA fibers, and SAP could effectively inhibit the shrinkage strain and cracking area of the concrete. The effect of the SAP on reducing the early shrinkage of the concrete is the greatest, and the shrinkage strain can be reduced by 76.49%. The PVA fibers had the most obvious effect on inhibiting the early cracking of the concrete, and the total cracking area was reduced by 66.91%. Significantly, the incorporation of the FS can improve the particle gradation and the pore structure and improve its compactness. The PVA fibers not only provide good carriers for cement-based materials but also enhance the bonding force between the particles inside the concrete, filling the pores inside the concrete, inhibiting the loss of water, and reducing the generation of internal microcracks. The FS and PVA can reduce the shrinkage and cracking risk and improve the strength and impermeability of the concrete. Although the SRA and SAP can reduce the shrinkage and cracking risks, it will lead to a significant decrease in the later strength and impermeability. The main reason is that the SRA leads to an increase in micropores in the matrix and microcracks near the aggregate, which are not conducive to the development of the strength and penetration resistance of the MS. Similarly, the SAP can promote the rapid formation of ettringite (Aft) at an early age and improve the early shrinkage, early cracking, and early strength of the concrete. However, with an increase in age, the residual pores, after SAP dehydration, will cause the deterioration of the concrete pore structure, resulting in the deterioration of the strength and impermeability. [ABSTRACT FROM AUTHOR]

Concrete prepared using Gobi sand and gravel instead of ordinary sand and gravel is referred to as Gobi concrete. In order to explore the effect of fibers on the frost resistance of Gobi concrete, as well as to enhance the service life of Gobi aggregate concrete in Northwest China, experiments were conducted with fiber types (polypropylene fibers, basalt fibers, polypropylene–basalt fibers) and fiber volume fractions (0%, 0.1%, 0.2%, 0.3%) as variable parameters. This study investigated the surface morphology, mass loss rate, and relative dynamic elastic modulus of fiber-reinforced Gobi concrete after different freeze–thaw cycles (0, 25, 50, 75, 100). Corresponding frost damage deterioration models were proposed. The results indicate that fibers have a favorable effect on the anti-peeling performance, mass loss rate, and dynamic elastic modulus of Gobi aggregate concrete. The improvement levels of different fiber types are in the following order: 0.1% basalt-polypropylene fibers, 0.2% polypropylene fibers, and 0.3% basalt fibers. Compared to Gobi concrete exposed to natural environmental conditions, the freeze–thaw cycle numbers increased by 343, 79, and 69 times, respectively. A quadratic polynomial damage model for fiber-reinforced Gobi concrete, using relative dynamic elastic modulus as the damage variable, was established and demonstrated good predictive performance. [ABSTRACT FROM AUTHOR]

In this paper, four water–binder ratios (w/b) of 0.29, 0.33, 0.39, and 0.46 were designed. A variable test temperature was implemented in the drying–wetting cycle test according to the temperature fluctuations in the actual service environment, and the constant temperature test was established as the control group. The mechanical properties and chloride corrosion resistance of concrete with different w/b ratios under variable temperature drying–wetting cycles, as well as the microstructure changes, phase composition, and damage mechanism inside the concrete, were investigated. The results showed that the mechanical properties of concrete increased first and then decreased with drying–wetting cycles increasing, whereas the chloride corrosion resistance continued to decline. A higher w/b exacerbated the deterioration of the concrete performance. A higher w/b increased the porosity, chloride diffusion depth, and chloride content, thus reducing the resistance of chloride corrosion. Compared with w/b = 0.29, the compressive strength, splitting tensile strength, mass, and relative dynamic elasticity modulus of w/b = 0.46 exposed to 60 drying–wetting cycles decreased by 54.50%, 52.44%, 0.96%, and 6.50%, respectively, while the porosity, peak chloride content, and erosion depth increased by 45.12%, 70.45%, and 45.00%. Compared with the drying–wetting cycle with a constant temperature, the cumulative damage caused by the drying–wetting cycle with a variable temperature was greater, resulting in more severe deterioration of concrete performance. The increase in the test temperature significantly accelerated the diffusion rate, penetration depth, and chemical binding capacity of chloride ions. After 60 drying–wetting cycles, the peak chlorine content and erosion depth of w/b = 0.46 under variable temperature cycles were 15.38% and 10.32% higher than those under a constant temperature, while the compressive strength, splitting tensile strength, mass, and relative dynamic elastic modulus were reduced by 7.76%, 14.81%, 0.33%, and 2.40%, respectively. Microscopic analysis confirmed that higher w/b and variable temperature cycles accelerated the decay of mechanical properties and the decline of chloride corrosion resistance. According to the numerical fitting analysis, the w/b should be 0.29~0.39 under the condition that the mechanical properties and chloride corrosion resistance of concrete are met. [ABSTRACT FROM AUTHOR]

Corrosion of reinforcement is the primary causal factor for premature deterioration of reinforced concrete (RC) structures. Exposure to elevated temperatures such as fire events can further exacerbate the integrity of the structure. The cumulative impact of the presence of corrosion and exposure to elevated temperatures on the behaviour of short RC columns constitutes the objective of present study. An experimental investigation was conducted to evaluate the effect of the degree of corrosion on the behaviour of RC short columns exposed to elevated temperatures. Total twenty-one RC short square column specimens were cast. Twelve columns were corroded to 10% and 20% degree of corrosion in accelerated corrosion process. Subsequent to completion of the corrosion process, columns were subjected to elevated temperature exposure (500°C and 800°C) in an electric furnace. Uncorroded specimens underwent the same thermal exposure regime. Afterwards uniaxial compression test was carried out. The results indicated that corrosion had pronounced effect on the ductility and residual load-bearing capacity of the columns upon exposure to high temperatures. Significant loss of cross section in the transverse reinforcements led to compromised lateral restraint in corroded columns. Columns with 20% corrosion had brittle failure. Role of stirrup design and layout in this aspect should be further investigated. Further research is recommended for detailed studies on the heat transfer mechanism in corroded RC columns when exposed to high temperatures. [ABSTRACT FROM AUTHOR]

Microbial-induced carbonate precipitation (MICP) is a promising process with applications in various industries, including soil improvement, bioremediation, and concrete repair. However, comprehensive bibliometric analyses focusing on MICP research in hydrodynamics are lacking. This study analyses 1098 articles from the Scopus database (1999–2024) using VOSviewer and R Studio, identifying information on publications, citations, authors, countries, journals, keyword hotspots, and research terms. Global participation from 66 countries is noted, with China and the United States leading in terms of contributions. The top-cited papers discuss the utilisation of ureolytic microorganisms to enhance soil properties, MICP mechanisms, concrete deterioration mitigation, soil and groundwater flow enhancement, biomineral distribution, and MICP treatment effects on soil hydraulic properties under varying conditions. Keywords like calcium carbonate, permeability, and Sporosarcina pasteurii are pivotal in MICP research. The co-occurrence analysis reveals thematic clusters like microbial cementation and geological properties, advancing our understanding of MICP's interdisciplinary nature and its role in addressing environmental challenges. [ABSTRACT FROM AUTHOR]

Forest plantations can be established in order to restore degraded areas. Acoustic tomography, which is of increasing importance in forest management, was used in the present study to obtain information for managing plantations of Cedrelinga cateniformis Ducke in the Peruvian Amazon. The species is valuable in the timber sector of Peru, but the core wood tends to deteriorate and develop cavities. The main objective of the study was to model wood deterioration in Cedrelinga cateniformis Ducke using the data obtained through acoustic tomography. Eight plantations of varying ages were analyzed using acoustic tomography in order to obtain indicators of wood deterioration. Biometric, climatic, and edaphic data (explanatory variables) were also measured in each plantation. The indicator variables and explanatory variables were compared and evaluated using correlation and principal component analysis. Wood deterioration was modelled using stepwise regression. The indicator variables differed significantly between plantations and were mainly correlated with the biometric variables (age and diameter at breast height). The models explained 81% of the variability of pith rot. The percentage rotten area was minimal in young plantations (1%), and the opposite was observed in mature trees (21.5 to 25.6%). The study findings provide valuable information, enabling foresters to determine the optimal age and diameter for felling Cedrelinga cateniformis in plantations in the Peruvian Amazon. [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]

Creating the openings in the existing reinforced concrete (RC) beams causes sudden deterioration, especially in the shear zone. This study investigates the effectiveness of a novel strengthening technology using externally reinforced fibre-reinforced polymer (FRP) strips in groves (EBRIG) on the shear behaviour of RC beams, compares it to that of externally reinforced (EBR) strips, and uses hybridisation between them to address the weakness brought on by the presence of an opening in the shear zone. Also, an innovative anchorage mechanism is suggested and studied to postpone the beginning of the strengthening system's debonding. The strengthening material used in this research is glass fibre-reinforced polymers (GFRPs). For this study, 11 RC beams with an opening and a control beam without an opening, each measuring 120 × 300 × 2600 mm in size, were cast and subjected to the four-point loading test. All test beams had the same geometry and reinforcement details. The effect of the following parameters was investigated in this study: the dimension of the opening (square '150 × 150' or rectangle '100 × 300' mm), the strengthening technique used (externally bonded reinforcement [EBR], EBRIG and hybrid technique 'EBRIG + EBR') and the wrapping configuration of the strengthening (fully warped strips or U-shaped sheets with anchors). All techniques used raised the efficiency of shear resistance to approximate the fading effect of the opening, especially the technique of hybridising EBRIG and EBR. All strengthened beams showed an increase in the ultimate shear capacity ranging from 74% to 142% compared with the reference beams with the opening. The EBRIG technique shows numerous advantages over the EB system and can employ the strength of FRP materials. It also deals with the problems of weather factors that were facing EBR, and this is because of the covering that protects in the EBRIG technique. The technique to hybridize EBRIG and EBR was more effective at withstanding shear. [ABSTRACT FROM AUTHOR]

The use of seawater and sea sand as replacements for fresh water and river sand in the preparation of seawater and sea sand concrete can effectively address issues such as high transportation costs, extended construction periods, and resource wastage. Nevertheless, in northern coastal areas, the problem of concrete durability in the complex and changing marine environment is more prominent. Research on the durability of seawater sea sand concrete is beneficial to the widening of its application range. To investigate the impact of glass fiber (GF) and polyvinyl alcohol fiber (PVA) with different blending methods on the seawater freeze–thaw resistance of seawater sea sand concrete (SSC), corresponding specimens were prepared, and seawater freeze–thaw cycling tests were conducted. By adopting the slow-freezing method and combining macro-structure and micro-morphology, the damage mechanism and the deterioration law of fiber-reinforced SSC under seawater freezing and thawing were investigated. The results indicate that, macroscopically, the incorporation of GF and PVA can effectively mitigate the damage to the matrix and reduce the effects of external erosive substances on the rate of strength loss, the rate of mass loss, and the relative dynamic elastic modulus. After 75 cycles, the SSC with a total volume doping of 0.3% and a blending ratio of 1:1 showed a 41.23% and 27.55% reduction in mass loss and strength loss, respectively, and a 29.9% improvement in relative dynamic elastic modulus compared with the basic group. Microscopic analysis reveals that the combined effect of freezing and expansion forces, the expansive substances generated by seawater intrusion into the interior of the matrix, and salt crystallization all weaken the bond between aggregate and mortar, leading to accelerated deterioration of the concrete. The incorporation of fibers enables the matrix to become denser and improves its crack-resistant properties, resulting in a better durability than that of the basic group. The damage prediction model established by the NSGM(1,N) model of gray system theory exhibits high accuracy and is suitable for long-term prediction, accurately predicting the damage of seawater sea sand concrete under seawater freeze–thaw coupling. [ABSTRACT FROM AUTHOR]

Staged construction is often used for bridges, in which a portion of a bridge remains open to traffic while another portion is closed for construction. Although staged construction reduces delays and the need for detours, subjecting the partially constructed bridge to dead and vehicular live loading can lead to damage and subsequent deterioration, including compromised longitudinal construction joints and transverse deck cracking. Despite past studies and best practices, transverse cracking persists and is often observed more on one side of the deck during construction, and no definitive explanation has been provided. As such, the objective of this study is to present a mechanics-based method for assessing transverse deck cracking in bridges during staged construction. Demonstrated on two bridges that underwent staged construction, the assessment method provides insights into the persistence of the issue and provides a mechanics-based explanation for observations of transverse cracking sometimes being observed only on one side of the bridge. The method, based on the superposition of strains, considers the sequence of steps in the construction process and estimates strain demands in the concrete decks at each stage, considering variations of the structural configuration, applied loads, and time-dependent behaviors. The results of the assessment agree with finite-element analysis results while requiring less model development and computational effort. The estimated strain history is then used to assess whether transverse cracking occurs by comparing the demand to the concrete's tensile strength in time. The method is demonstrated on a new bridge constructed in stages and an existing bridge that underwent rehabilitation via staged construction. The results of the demonstrations suggest the importance of evaluating both the open and closed portions of bridge decks at each stage, as each portion has different structural and mechanical properties and loading demands. The assessment results are qualitatively validated based upon information from postconstruction bridge inspections. Furthermore, the method can be used to gain insight into mitigating transverse deck cracking and support decision-making for bridge construction practices. [ABSTRACT FROM AUTHOR]

Water plays a significant role in the deterioration of reinforced concrete buildings; therefore, it is essential to evaluate the water content of the cover concrete. This study explores a novel non-destructive method for assessing the water content using sub-terahertz (sub-THz) waves. Among the four frequencies selected to evaluate the water content, an increase in reflectance was observed as the unit volume water content increased, and smaller data scatter was confirmed as the frequency increased. The derived empirical equation can classify the corrosion risk of the rebar environment based on the water content obtained using reflectance measurements. In other words, it can contribute to the diagnosis of the building integrity associated with rebar corrosion. [ABSTRACT FROM AUTHOR]

Corrosion may cause uniform or localized deterioration to steel bridges, which could gradually diminish carrying capacity as the damage worsens. Carbon fiber reinforced polymer (CFRP) has immense promise due to its low weight and excellent durability, elasticity, and strength. This paper investigates the effectiveness of CFRP as a repair for corroded steel I-girder ends in terms of shear and end-bearing capacities. First, this study presents finite element validation of corrosion and CFRP modeling; based on the result, the setting and analysis process can be implemented in the case study. Then, the simulation of five cases of uniform corrosion involves a range of corrosion damage situations, encompassing corrosion heights, widths, and thickness loss. The stiffener, end web, and inner web simulate the corroded part. Finite element analysis (FEA) uses nonlinearity buckling analysis and assigns the Shell S4R element type steel. The constitutive isotropic elastic model is applied to steel, while CFRP utilizes an orthotropic lamina. The CFRP failure pattern uses the Hashin Damage Criterion model constitutive. Three layers are applied to each side of the model. Analysis shows CFRP in stiffener corroded area significantly increases remaining shear capacity by 0-11.8% for one side and 0-19% for both sides, in bearing capacity by 0-8.4% and 0-17.3%, respectively. Its efficacy in end-bearing is 0-6.3% in the end web, inner web, and combination areas. End web shear capacity increased slightly, while inner and combination web capacity decreased by 0-2% from the health model. [ABSTRACT FROM AUTHOR]

This paper presents the results of a study conducted to investigate the properties of alkali-activated concrete (AAC) mixtures prepared using the optimum combinations of four precursor materials (red mud, limestone powder, silicomanganese fume, and natural pozzolana) and four activation parameters (activator to precursor ratio, silica modulus, sodium hydroxide molarity, and water to precursor ratio). In order to examine the beneficial effects of inclusion of ordinary portland cement (OPC) and curing regimes on the properties of AAC, three dosages of OPC (in the range of 10% to 30% by weight) and two types of curing (steam and air curing) were considered. Tests were conducted on the mixtures of AAC to determine different properties that included the density, void ratio, water absorption, compressive and tensile strengths, modulus of elasticity, drying shrinkage, and loss of weight and strength after exposure to acid and sulfate salt solutions. Additionally, microstructural investigations (x-ray diffraction and scanning electron microscopy with energy dispersive spectroscopy) were conducted on the alkali-activated binders to justify the trends of the experimental data pertaining to different properties of the AAC mixtures. The results of the tests indicated that the properties of AAC were significantly affected by inclusion of OPC and curing regimes. It was found that almost all properties of the AAC were significantly enhanced when the OPC dosage was increased from 10% to 20%. Further, the AAC mixtures having more than 10% OPC exhibited better properties as compared to the traditional OPC concrete mixture. The use of OPC as a construction material is one of the major contributing factors to environmental damage. Multiple alternative materials have been suggested as a replacement for OPC such as alkali-activated industrial byproducts and natural minerals. However, these possible materials are not as well studied as OPC in terms of their strength development, volumetric stability, and resistance to extreme environments. In this work, the performance of different AAC made with natural minerals and industrial waste materials was evaluated, and we compared their performance to typical OPC concrete. The present investigation shows that the developed alternative concrete mixtures perform in a comparable or better manner to OPC concrete mixtures in terms of strength, volume change with age, acid resistance, and sulfate resistance while reducing the OPC content by 70% to 90%. The study scope, however, does not extend to study the economic viability and carbon footprint of the proposed AAC mixtures. [ABSTRACT FROM AUTHOR]

Water plays a vital role in deteriorating stone heritage, especially those carved into vertical rock slopes. Southeast China is home to numerous limestone rock-hewn heritages, many of which showcase diverse deterioration patterns on their facades. Nevertheless, due to the large scale of this heritage and the limitations imposed by the principle of minimal intervention in practices, there is still a lack of practical strategies for understanding moisture distribution. Therefore, this study aims to analyse the moisture distribution of limestone rock-hewn statues via in situ detection employing a portable hygrometer and laboratory calibration based on the gravimetric method and regression analysis. The in situ determination was conducted in the Ciyunling statues niche 1 (World Heritage Site), which was hewn in the Wuyue states (942 CE). Thirty-six measuring areas were evenly planned on the niche's façade, with 20 moisture readings obtained from each measuring area. Additionally, the surface hardness of the typical area of statues was examined using a non-invasive Leeb hardness tester and Kruskal–Wallis H test to assess the impact of moisture on deterioration. The findings reveal that the statues' moisture content is higher than the background wall between the statues, signalling a greater potential for deterioration on the surface of the limestone statue. The primary source of moisture appears to be gaseous water in the atmosphere, which accumulates in the micropores through capillary condensation. Furthermore, the statistically significant differences in surface hardness between the chest/shoulder of statues and the root of the façade highlight the softening effect of moisture on the foundation of the limestone statues. Hence, the methodology utilised in this study serves as a viable approach for examining moisture levels and the extent of deterioration in rock-hewn heritage structures. Highlights: Systematic in situ measurement of moisture distribution on the facades of limestone rock-hewn heritage. A linear regression equation between limestone's electrical resistance-based moisture content (ωc) and the gravimetric moisture content (ωo) was obtained. The surface of the limestone statues contains more moisture signalling a greater potential for water-induced weathering. the surface hardness of the limestone facade significantly diminishes as the height decreases according to Kruskal–Wallis H test. [ABSTRACT FROM AUTHOR]

Mineral transformations often induce microstructural deteriorations during temperature variations. Hence, it is crucial to understand why and how this microstructure weakens due to mineral alteration with temperature and the correlated physical and mechanical responses. Therefore, in this study, physical, chemical, thermal, petrographic, and mechanical analyses were carried out to comprehend better the thermal behaviors of Egyptian granodiorite exposed to temperatures as high as 800 °C. The experimental results indicate that the examined attributes change in three distinct temperature phases. Strength zone (up to 200 °C): During this phase, the temperature only slightly impacts the granodiorite mass loss and porosity, and the P-wave velocity and E slightly decrease. However, the rock structure was densified, which resulted in a minor increase in strength. After that, the transition zone (200–400 °C) was distinguished by the stability of most studied parameters. For instance, mass and porosity did not significantly alter, and the uniaxial compressive strength steadily increased with an axial failure mode. When the temperature rises, transgranular cracks cause the P-wave velocity and elastic modulus to decrease moderately. The decay zone started after 400 °C and continued to 800 °C. This zone is characterized by complicated factors that worsen the granodiorite properties, lead to color shift, and produce a shear failure mode. The properties of granodiorite became worse because of chemical reactions, structural and crystal water evaporation, rising thermal expansion coefficient variation, and quartz inversion at 575 °C (α to β, according to the differential thermal analysis). Thermal damage greatly affected granodiorite's physical and mechanical properties and microstructure at 800 °C. As a result, UCS measurements were extremely small with a complex failure pattern, making Vp and E unattainable. [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.)

Purpose: The dynamic responses of a concrete machine foundation under impact load type were studied considering the deterioration of concrete due to chemo-mechanical actions over the ages. This investigation was furtherly implemented considering different soil types from soft to hard types. Methods: The two-dimensional plain-strain finite element formulations of this coupled problem were written in FORTRAN 90 and MATLAB programming language. The coupled equation of motion for soil–machine foundation interaction problem has been analyzed by direct method. The soil medium was divided into near and far-field domains, where the far-field soil domain included the radiation of reflected dynamic waves discretizing with infinite solid elements. Results: The dynamic responses of machine foundation are significantly affected by the deterioration of concrete over the ages. The area of extreme stress responses at the foundation increases according to the increments of deterioration in concrete. According to 0 and 50 years age, the stress responses of machine foundation for medium soil type were seen to be decreased to 32.6%. Moreover, the displacement responses of machine foundations increase when the soil type properties vary from hard to soft type. Conclusion: The deterioration of concrete and the existence of different soil medium have significant effect on the dynamic responses of machine foundations that should be considered in analysis and design. [ABSTRACT FROM AUTHOR]

The corrosion of alkaline concrete materials exposed to a sulfuric acid environment is becoming more and more prevalent, and its damage assessment is becoming more and more imperative. This study aims to describe the corroded surfaces of concrete with different strength grades (C30, C50, C80) in sulfuric acid environments in terms of their three-dimensional fractal dimension. Three kinds of concrete with varying strength grades, namely C30, C50, and C80, were immersed in a sulfuric acid solution with pH ≈ 0.85 for four distinct corrosion durations, specifically 0, 28, 56, and 165 days, in accelerated corrosion tests. The 3D laser scanning technique was utilized to capture the 3D coordinates of the surface points of the concrete cylinder before and after corrosion. The fractal dimension of concrete's uneven surface before and after corrosion was computed via the cube covering method, and the mass loss of the concrete specimen was also obtained. The outcomes demonstrate that the three-dimensional fractal dimension provides a new method for characterizing the degree of corrosion deterioration of concrete samples affected by sulfuric acid via laser scanning technology. From the perspective of the appearance, mass loss, and fractal dimension of a rough surface in the sulfuric acid environment at a pH level of approximately 0.85, the degree of the corrosion deterioration of concrete is ranked from high to low as C80 > C50 > C30. These fractal dimensions of the concrete's corroded surfaces with various strength grades increase rapidly in the initial period. However, as the corrosion time progresses, the growth rate of the corroded surface fractal dimension gradually decelerates and tends towards stability, which accords with the law of exponential function. The widespread belief is that the higher the strength grade of concrete, the better its durability; however, this pattern varies in sulfuric acid corrosive environments. Therefore, based on this research, it is recommended that in extremely acidic environments (i.e., very low pH), more attention should be paid to high-strength grades of concrete. [ABSTRACT FROM AUTHOR]

The durability of bridges plays a vital role in their regular operation and transportation, particularly as service life increases. The ability of a bridge to reach its expected service life is closely linked to its durability. In cold regions, the deterioration of bridge concrete durability due to freeze-thaw damage is a common cause of failure, posing a threat to structural safety. In this study, a highway bridge over a sluice that was built 63 years ago was selected for coring and freeze-thaw testing. Two nondestructive testing methods were employed: three-dimensional optical scanning and X-ray computed tomography (X-CT). The former was used to observe and analyze the external surface of the concrete, while the latter was used to analyze its internal structure. The surface morphology was characterized using height, spatial, hybrid parameters, and fractal dimension, and the Abbott–Firestone curve reflected the profile characteristics of the material surface. Moreover, the internal components of concrete were identified and reconstructed in three dimensions based on threshold segmentation, and the changes in internal porosity, pore fractal dimension, and pore size distribution were calculated. Finally, the evolution of bandwidth in the color heat map was analyzed, combining the gray level cooccurrence matrix (GLCM) to reflect the growth of cracks and defects with freeze-thaw cycles. [ABSTRACT FROM AUTHOR]

Concrete deterioration due to sulfate attack is one of the factors for early failure. Considering that sulfates in aggregates are the most important problem related to concrete in the cities of the Middle East and especially Iraq, so there was a need to develop a device to enhance the strength of concrete. In the current experimental research, we sought to discover how to treat and improve the performance of fresh concrete containing high percentages of sulfate salts in sand, using a magnetic field generation device with an electrical principle made locally. The work included the beginning of casting 27 models of concrete cubes that were treated using different magnetic intensities and examined to select the highest strength, which was 3000 Gauss, which was adopted in this research. Two groups of mixtures were prepared and poured using 72 cubes and prisms. The first group was divided into two reference mixtures not treated with a magnetic field. Two types of sand with different sulfate ratios with resistant Portland cement were used. The second group was prepared using the same method and working conditions, except for treating the concrete mixture with electromagnetic fields. The results showed an encouraging improvement in the compressive strength of magnetically treated concrete, where the rates of increase in compressive strength were (5.45, 5.5, 5.7%) with 0.15% SO3, and (7.2.7, 4.6%) with 0.6%. SO3 for a period of (7.28 and 90) days, respectively, compared to control mixtures. This technology can be applied during the pouring process on job sites. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Harbin Institute of Technology. Social Sciences Edition / Haerbin Gongye Daxue Xuebao. Shehui Kexue Ban is the property of Harbin Institute of Technology 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.)

An Engineered Cementitious Composites (ECC)-Reinforced Concrete (RC) composite pier with high-strength steel bars was developed to address various deterioration concerns in bridges, such as reinforcement bar corrosion, decreased concrete strength, and inadequate seismic performance of RC piers. This paper focuses on the seismic performance of the bridge with ECC-RC composite piers with high-strength steel bars. The nonlinear finite element models of bridges with common RC piers and ECC-RC composite piers with high-strength steel bars are established using OpenSees. Considering the effect of chloride erosion during bridge service and the damage and repair of concrete cover, time-varying fragility curves for bridge piers, bearings, and the bridge system were established based on the Incremental Dynamic Analysis (IDA) and the Capacity Demand Ratio (CDR) analysis method, followed by a comprehensive analysis. The results show that when ECC with high-strength steel bars is adopted in the plastic hinge area of bridge piers, the exceeding probability of ECC-RC composite piers with high-strength steel bars is significantly reduced. However, it has minimal impact on the seismic fragility of the bearings. When the bridge was in service for 100 years, the exceeding probability of the ECC-RC composite bridge system with high-strength steel bars was reduced by 18.79%, 51.33%, 49.38%, and 19.5%, respectively, under four different damage states. [ABSTRACT FROM AUTHOR]

Industrial waste locks are used as raw materials to reduce harmful effects on the environment and improve environmental performance. Marble clay powder can be used as a filling aid and can fill voids in concrete structures. This article will show you how to use a maximum natural sand alternative in concrete with marble powder and quarry dust. The challenge of the 21st century is to change to a new form that can support the natural system. This necessitates a radical rethinking of how to give the community infrastructure and housing. Making a concerted effort to develop novel, innovative, and alternative construction materials may be necessary. Jungles of concrete around cause's impact on the Environment and it would result in climate change. Mankind must avoid the use of things that are detrimental to the environment. So in this paper, it is decided to address the issue by adopting the use of the green concrete concept which is environmentally friendly. Green concrete is concrete made up using industrial wastes such as marble powder, quarry dust, wood ash, paper pulp, etc. Green concrete, which is capable of sustainable development, helps to reduce the consumption of natural resources, energy use, and environmental pollution. Green concrete is more cost‐effective than ordinary concrete and reduces the cost of resultant concrete by 14%–20%. It is also observed that the alkali‐aggregate reaction and sulfate attack resistance of concrete are both significantly improved. Green concrete is a useful tool for lowering environmental pollution and enhancing concrete's resistance to harsh conditions. All stages of infrastructure construction and rehabilitation will follow this trend of using new cement and techniques. Green concrete's adaptability and its performance derivatives will meet a variety of future needs. [ABSTRACT FROM AUTHOR]

This study introduces precast concrete beam–column connections comprised of composite beams, precast columns, and a monolithic joint core. The composite beams consist of U-shaped beams and floor slabs, leveraging the U-shaped beams for their lightweight nature, acceptable stiffness, and reduced demand for on-site support systems. To mitigate reinforcement congestion in the joint core, the precast connections incorporate large-diameter rebars (greater than 25 mm). This study conducted cyclic loading tests on four full-scale beam–column connections under 0.3 normalized compression, encompassing precast interior and exterior connections, along with two monolithic reference specimens, to investigate their behavior under seismic actions. The results revealed that all specimens exhibited bending failure at the beam ends, with minimal concrete deterioration observed in the joint core areas and columns. The hysteresis curves of the precast specimens and the monolithic connections exhibited a slight pinching effect. The strengths of the interior and exterior precast specimens were 13.3% and 7.8% lower than those of the reference monolithic connections, respectively. The ductility of interior precast connections and monolithic specimens stood at 2.36 and 2.23, respectively, indicating a negligible difference of less than 5%. Meanwhile, the positive and negative ductility of exterior precast connections were 3.06 and 2.34, which was approximately 8% lower than that of the reference connections. Furthermore, the stiffness degradation and energy dissipation capacity of the precast specimens aligned closely with the performance of the reference monolithic ones. [ABSTRACT FROM AUTHOR]

Corrosive chloride (Cl-) and sulfate (SO42-) in sabkha are major environmental factors accelerating the deterioration of concrete structures with steel rebars or steel structures through long-term exposure. The dissolution of these corrosive anions from the surrounding soil must be reduced to increase the lifespan and durability and to ensure the protection of such structures. This study investigated the impact of bitumen addition on the amount of leached corrosive Cl- and SO42- in terms of quantity and rate as the percentage of total dissolved solids. Representative sabkha soil samples obtained from southern Kuwait were blended with various bitumen contents and leached with distilled water for more than 25 days, and the leached pore volumes were examined for the detected anions. Bitumen percentages of 0%, 4%, and 12% (by dry weight of sabkha) were selected as the mixing percentages based on geotechnical testing (density results obtained via modified Proctor tests) below and above the optimum bitumen contents. Results show that corrosive anion dissolution is reduced more in the bitumen-mixed sabkha than in the natural soil samples. The SO42-and Cl- concentrations almost diminish at the early leaching stages in the 12% bitumen-mixed sabkha sample, showing a strong reduction trend in the corrosive anion concentration. These findings highlight the importance of the waterproofing effect of bitumen in reducing corrosive anion dissolution from sabkha soil, which will reduce the impact of these soils on various structures, particularly buried gas, or oil steel pipes, and improve the effectiveness of other protective methods used for these structures. [ABSTRACT FROM AUTHOR]

Concrete structures partially immersed in seawater will be subjected to severe chloride and sulfate erosion under the capillary and diffusion actions. Nevertheless, the present studies only discuss the capillary action in a static water level environment, without considering the capillary action in a water level fluctuating environment. In this paper, the mechanical properties and ions transmission law of concrete under the capillary and diffusion actions in water level fluctuating environment were investigated through a series of indoor exposure tests. Three erosion solutions were set to study the interaction effects of chloride, sulfate, and magnesium within concrete. Based on the compressive strength tests, the mechanical properties of concrete in a water level fluctuating environment were explored. The natural diffusion tests were carried out to research the sulfate and chloride transmission law within concrete above and in the water level fluctuating zone (WLFZ). Scanning electronic microscopy (SEM), X-ray diffractometer (XRD), and mercury injection porosimeter (MIP) measurements were conducted to analyze the microstructures at various zones of concrete under different erosion solutions. The results show that the concrete partially immersed in WLFZ suffers from severe sulfate attack on mechanical properties due to the dual influences of sulfate chemical and physical crystallization attack. The chloride concentration within concrete above WLFZ is significantly higher under the capillary action. The sulfate concentration within concrete above WLFZ is lower because of the chemical binding of sulfate within concrete. The higher porosity and more capillary pores exist in concrete above WLFZ due to the carbonization and water evaporation. By decreasing the porosity of concrete, sulfate will inhibit the chloride transmission and magnesium will restrain the sulfate and chloride transmission. The transmission mechanisms of erosion ions within concrete above WLFZ consist of vertical transmission under the capillary action and lateral transmission under the diffusion action and water evaporation. [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]