Search

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]

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]

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]

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]

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]

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]

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]

• Novel analysis of attenuation the growth of Aspergillus tamarii on concrete using radiation in the field of conservation of heritage building. • UVC and gamma irradiation decreased the leaching of calcium ions from concrete when infected with A. tamarii. • Increase in compressive strength of concrete cube was observed to be the most in irradiated cubes. • Effect of A. tamarii and low dose radiation led to less deterioration of concrete (except higher dose) than only exposure to A. tamarii. The conservation of concrete-based deteriorated heritage buildings is a big challenging issue worldwide including in India. This study focused on to prevent fungal biodeterioration in concrete using UVC and gamma radiation. M20 graded concrete cubes (5 cm × 5 cm × 5 cm) were infected with Aspergillus tamarii , which was isolated from a 200 years old historic heritage building. M20 signifies a mixture of cement, sand and aggregate (1:1.5:3), made in such a way that the concrete cube has a compressive strength of 20 N/mm2 when examined after 28 days of curing. The fungal growth appeared clearly as calcium oxalate crystals in the Scanning Electron Microscope (SEM) photographs. Several doses of UVC and gamma radiation were applied on concrete cube. The changes in concrete properties were examined after 30 days in terms of weight, compressive strength, Fourier Transform Infrared Spectroscopy (FTIR) and micro Energy Dispersive X-ray Fluorescence (EDXRF). The results exhibited that compressive strength of control (non-infected and non-irradiated), biodeteriorated (infected), UVC (625 µw/cm² × 300 s) and gamma (0.5 KGy) irradiated infected (inhibition) concrete cubes were 19.74 ± 0.46, 18.88 ± 0.43, 20.20 ± 0.34 and 19.93 ± 0.20 N/mm2 respectively whereas negligible weight losses were observed for inhibition cubes compared to biodeteriorated ones. Calcite (1400, 874 and 705 cm−1), one of the major functional band present in concrete became weak after getting infected by Aspergillus tamarii and strong for inhibition samples irradiated with the above doses. The EDXRF analysis exhibited that mass percentage of calcium ions of the biodeteriorated concrete cubes (49.88 ± 0.65%) was lower than that of UV (75.75 ± 0.16%) and gamma (70.95 ± 0.30%) irradiated infected or inhibition concrete cubes. Altogether, the efficacy of the recommended inhibitory dose of ultraviolet and gamma radiation against concrete deterioration in the field of conservation of heritage building was observed to be positive. [Display omitted] [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]

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]

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]

Reinforcement corrosion is the main cause of performance deterioration of reinforced concrete (RC) structures. Limited research has been performed to investigate the life-cycle cost (LCC) of coastal bridge piers with nonuniform corrosion using different materials. In this study, a reliability-based design optimization (RBDO) procedure is improved for the design of coastal bridge piers using six groups of commonly used materials, i.e., normal performance concrete (NPC) with black steel (BS) rebar, high strength steel (HSS) rebar, epoxy coated (EC) rebar, and stainless steel (SS) rebar (named NPC-BS, NPC-HSS, NPC-EC, and NPC-SS, respectively), NPC with BS with silane soakage on the pier surface (named NPC-Silane), and high-performance concrete (HPC) with BS rebar (named HPC-BS). First, the RBDO procedure is improved for the design optimization of coastal bridge piers, and a bridge is selected to illustrate the procedure. Then, reliability analysis of the pier designed with each group of materials is carried out to obtain the time-dependent reliability in terms of the ultimate and serviceability performances. Next, the repair time of the pier is predicted based on the time-dependent reliability indices. Finally, the time-dependent LCCs for the pier are obtained for the selection of the optimal design. [ABSTRACT FROM AUTHOR]

Soy methyl ester-polystyrene (SME-PS) is a biodegradable and nontoxic blend of soybean oil and waste polystyrene that can be used as a surface treatment to improve concrete deterioration and rebar corrosion caused by freeze–thaw cycles and chloride salt exposures. Although SME-PS has shown promising results for concrete protection, the mechanism by which it protects concrete is relatively unknown. The current study utilizes thermal analysis techniques to explore the physical and chemical protecting mechanism of SME-PS. The potential chemical reaction, reaction rate, and reaction products among SME-PS, hydrated cement paste, and cement hydration products are investigated using isothermal calorimetry and thermogravimetric analysis. Dynamic vapor sorption analysis is conducted to physically evaluate the effect of SME-PS on the pore structure of concrete. The results indicated that the SME-PS can occupy the pores with sizes smaller than 50 nm, physically preventing the ingress of detrimental ions and water into the concrete porous structure. It was also found that SME-PS can chemically interact with cement paste products rapidly occurring at the first 12 min of blending of cement paste powder with SME-PS. The thermogravimetric results indicated the SME-PS reaction mainly occurs among calcium hydroxide, pore solution, and gypsum. Additionally, the hydrophobic nature of SME-PS is beneficial in terms of protecting the cementitious material surface from aggressive chemicals. [ABSTRACT FROM AUTHOR]

In order to study the dynamic mechanical properties of concrete under freeze-thaw cycles, uniaxial impact compression tests were conducted on concrete specimens with different number of freeze-thaw cycles (0, 25, 50, 75, and 100) using a 50 mm diameter split Hopkinson pressure bar (SHPB) test device at an impact air pressure of 0.4 MPa and combined with a CT scanning system to analyze the internal fissures of concrete specimens before and after freeze-thaw cycles. The results showed the following. (1) The concrete specimens were divided into linear elastic stage, plastic stage, and damage stage under the freeze-thaw cycle, and the macroscopic mechanical parameters of the specimens were weakened with the increase of the number of freeze-thaw cycles. (2) Freeze-thaw intensified the expansion and penetration of the internal fracture of the specimens, and the CT scan results showed that the internal fracture parameters of the concrete specimens were increased with the increase of the number of freeze-thaw cycles, and the structural characteristics of the internal fracture show gradually complex expansion and evolution characteristics. (3) The degree of damage was defined at the fine level, which increased with the number of freeze-thaw cycles, establishing an intrinsic link between the fine deterioration of concrete specimens and the loss of macroscopic parameters under freeze-thaw cycles. The results are of great significance to further elucidate the internal structural characteristics of concrete material damage under freeze-thaw conditions and to reveal the damage deterioration mechanism. [ABSTRACT FROM AUTHOR]

A high-performance concrete rapid patching repair material needs to develop high early strength to satisfy traffic opening requirements, yet provides sufficient durability to sustain different environmental conditions and primary deterioration mechanisms for full-depth concrete repair. In this study, a set of experiments was conducted to evaluate the performance of developed pavement repair mixtures subjected to different environmental conditions, including low ambient temperature, highly reactive siliceous aggregate, wet/dry cycling, and moisture loss. Full-scale slab patching was also carried out to assess the rapid patching mixtures' constructability, compatibility, and interface bonding with the concrete substrate. Patching materials with a reduced cement content and Type IP cement exhibited a lower drying shrinkage rate and less deterioration from wet/dry cycles compared with commonly used patching mixtures that typically use high cement content and Type I cement. The tendency of alkali-silica reaction deterioration was reduced significantly by replacing 50% Type III cement with Type IP cement. The rapid patching mixtures generally displayed a high degree of early-age shrinkage but with satisfactory compatibility and good bonding with the concrete substrate. Test results also indicate that Type III cement-based rapid patching mixtures can be a promising option to reduce traffic closure duration at lower ambient temperatures. [ABSTRACT FROM AUTHOR]

Many road agencies worldwide still use the empirical AASHTO 1993 pavement design method. Since the release of the AASHTO 1993 design guide, many aspects of pavement design have changed, including asphalt material properties, traffic, environmental factors, etc. However, many agencies use a single layer coefficient for asphalt mixtures and pavements are currently designed with inaccurate values, as proved by many. This paper presents a four-step procedure (called AASHTO 93 Plus method) to determine structural layer coefficients of asphalt mixtures. The AASHTO 93 Plus method considers viscoelasticity and temperature-dependency of asphalt mixtures to estimate the layer coefficient. Five-hundred-eighteen (518) flexible pavements from USA and Canada roads and 1599 HMAs from the Long-Term Pavement Performance (LTPP) database were analyzed. The results showed that the new material-specific layer coefficients were well above the typical value of 0.44. The total number of 3,726 IRI data records of these 518 pavements were converted to PSI and then compared to those obtained from the traditional AASHTO 93 and AASHTO 93 Plus methods for validation. Results confirmed that the conventional AASHTO 93 method predicts faster deterioration of pavement conditions over time, while the results of AASHTO 93 Plus method better aligned with the field data. [ABSTRACT FROM AUTHOR]

The study presented in the paper evaluated the properties of pavement quality concrete (PQC) containing coarse aggregates made from aged and unaged basic oxygen furnace (BOF) slag. Workability, air content, strength, drying shrinkage, expansion, abrasion resistance and expansive potential of PQC were evaluated. Air content and workability of fresh slag concrete increased marginally. Compressive and flexural strength of the concrete containing aggregates of aged and unaged slag was observed to be less than the strength of normal concrete. The reduction in strength of concrete containing aged slag aggregates was more as compared to the concrete containing unaged slag aggregates due to the presence of a dusty coating around the aged aggregates. The drying shrinkage of the concrete increased with the content of steel slag aggregates. The abrasion resistance of the slag concrete was found to be better than the abrasion resistance of conventional concrete. Deterioration of slag concrete was not observed due to normal water curing up to 90 days. However, accelerated aging of concrete in water at 70°C resulted in the localised cracking and eruptions due to expansion. The study showed that, aged as well as unaged slag aggregates may be used for the preparation of concrete mixtures of required properties for road construction. [ABSTRACT FROM AUTHOR]

Digital twins have been developed in the oil and gas industry to support a more precise risk assessment that enables performance improvement of offshore structures throughout their life span. Usually, a floating, production, storage and offloading (FPSO) unit is required to exploit oil fields in deep and ultra-deepwater with the postponement of the decommissioning stage, leading to increasing maintenance costs due to aging effects. This paper proposes an adaptive methodology for the development of a digital twin that performs automated numerical analysis via finite element model updating (FEMU) based on coupled systems of a high-fidelity FPSO hull model. The methodology employs a three-cargo tank length finite element (FE) model to receive data and automatically solve multiple numerical analyses. If during results checking any alert level is reached by any structural component, a more complex structural reliability method is applied to provide failure probability considering material strength statistical distribution. The application herein investigates the effects of corrosion, but other phenomena can be considered within the developed framework. A corrosion prediction model is used to create different hypotheses of degradation for bottom plates, while data provided from coupled systems are considered to investigate the effect of deterioration. The results demonstrate a consistent probability of failure when compared to the evolution of the predicted corrosion during service life. [ABSTRACT FROM AUTHOR]

This study focuses on the measurement of concrete cracks in three dimensions (3D) using the particle swarm optimization-based projection algorithm, OpenCV technique, and X-ray computerized tomography (CT) images. The primary objective is to visualize the development of cracks in fire-damaged concrete. The data for X-ray CT imaging were collected, consisting of 3,011 CT images obtained from damaged specimens. The sampling criteria employed ensured a convenient sampling process with a 95% confidence level and 5% limits of errors in the 50–50 category. The results reveal that the undamaged specimens exhibited an average of 406 smaller-sized pores, whereas the fire-damaged specimens, which were subjected to a temperature of 900°C for 1 h, displayed a significant increase in the number of pores and cracks. The proposed method successfully enables the plotting of 3D measurements of concrete crack development. This achievement has practical implications for practitioners, as it allows for (1) visualizing crack development as an initial step toward analyzing deterioration patterns in concrete, and (2) conducting an analysis of concrete failure in structures following fire scenario simulations. Overall, the findings of this study contribute to a better understanding of concrete crack development and offer valuable insights for practitioners in the field. [ABSTRACT FROM AUTHOR]

The durability of reinforced concrete (RC) structures and infrastructure has been the subject of significant attention from the engineering research community in recent years, mainly owing to the deterioration of RC elements due to corrosion of the embedded steel reinforcement. In this context, stainless steel reinforcement can provide an efficient solution to enhance the expected lifetime of concrete structures, reducing the damage due to corrosion of the reinforcement and carbonation and deterioration of the concrete. However, current international design standards for reinforced concrete structures do not include appropriate guidance for stainless steel reinforced concrete (SSRC). In order to investigate the behaviour of stainless steel RC beams, a series of six beam tests was conducted and is discussed herein. The key performance measures for RC beams such as load-deflection response, cracking behaviour and deflections at service load are assessed. The validity and applicability of existing design rules, which were developed for carbon steel RC, are also examined for stainless steel reinforced concrete members. Other recently developed design procedures, based on the Continuous Strength Method and including an accurate material model for the stainless steel bars, are also examined. [ABSTRACT FROM AUTHOR]

The study presented in the paper evaluated the properties of pavement quality concrete (PQC) containing coarse aggregates made from aged and unaged basic oxygen furnace (BOF) slag. Workability, air content, strength, drying shrinkage, expansion, abrasion resistance and expansive potential of PQC were evaluated. Air content and workability of fresh slag concrete increased marginally. Compressive and flexural strength of the concrete containing aggregates of aged and unaged slag was observed to be less than the strength of normal concrete. The reduction in strength of concrete containing aged slag aggregates was more as compared to the concrete containing unaged slag aggregates due to the presence of a dusty coating around the aged aggregates. The drying shrinkage of the concrete increased with the content of steel slag aggregates. The abrasion resistance of the slag concrete was found to be better than the abrasion resistance of conventional concrete. Deterioration of slag concrete was not observed due to normal water curing up to 90 days. However, accelerated aging of concrete in water at 70°C resulted in the localised cracking and eruptions due to expansion. The study showed that, aged as well as unaged slag aggregates may be used for the preparation of concrete mixtures of required properties for road construction. [ABSTRACT FROM AUTHOR]

Limited information is available on the transport behaviour of concrete after being exposed to carbon dioxide, which is one of the major reasons for the premature deterioration of reinforced concrete structures. This study investigates the changes induced in the transport characteristics of concrete after carbonation through conventional tests on concrete such as porosity, sorptivity, oxygen permeability and resistivity. A total of 10 concrete mixes were prepared using five supplementary cementitious materials (SCMs) (Class C fly ash, Class F fly ash, pumice, perlite and calcined clay) at the 30% cement replacement level and two water to binder ratios. The concrete samples were cured for 28 days in water and were subsequently placed under three different exposure conditions (2.5% CO2, oven 50°C and under water) for 60 days. In general, a reduction in porosity was observed on carbonation in all the concrete mixes. However, for SCM-incorporated concrete mixes, an inferior sorptivity, permeability and resistivity performance were observed specifically for lower compressive strength concrete mixes and clay mixes. [ABSTRACT FROM AUTHOR]

This study investigates the feasibility of an alternative structural health monitoring (SHM) technique for an existing, post-tensioned, prestressed concrete bridge in Niigata, Japan. Currently, a static SHM system is in place to detect the progress of damages within the bridge. However, the existing system cannot properly monitor the structural health of the bridge including the periodic vibration, which is one of the damage-sensitive features of interest. Therefore, to effectively detect the real-time performances of the bridge, a three-dimensional (3D) Finite Element (FE) model was developed as a reference and verified using on-site loaddeflection test results. After validating the reference FE model, different damage scenarios, such as degradation of concrete, corrosion & rupture of steel tendons and missing tendons, were incorporated in the FE models. Based on non-linear structural and Eigenvalue analyses, natural frequencies and mode shapes of the bridge remain constant even after careful consideration of all types of damages in the FE model. However, vertical displacements are observed to increase for the damage scenarios. Although the effect of tendon rupture and corrosion showed negligible influences on the vertical displacement, the deterioration of the concrete largely influenced the vertical displacement. Additionally, crack widths were found to vary with damage types. Brifely, this study recommends some effective indicators to monitor the structural conditions of the bridge using FE analysis (FEA). [ABSTRACT FROM AUTHOR]

Recycled aggregates, especially the fine (0–4 mm) fraction, are often contaminated with sulfates coming from gypsum residues on demolition sites. When these aggregates are used in concrete, the sulfates can induce internal sulfate attack which causes expansion of the concrete. European standard EN 206:2013 sets the water-soluble sulfate limit at 0.2% by weight of the aggregate, but other studies suggest this limit could be safely increased. In addition to the sulfate content, other parameters, such as the porosity and alkalinity of the mix, have been shown to influence the swelling results. In this study, different proposed sulfate limits were evaluated on concrete made with 100% fine recycled aggregates (FRA). It was also researched whether the mixing parameters could change the swelling amount regardless of the sulfate content. The results showed that the incorporation of FRA with sulfate contents up to 0.8 wt% is safe when combined with coarse natural aggregates. If coarse recycled aggregates are used in the mix, the sulfate content of FRA can be up to 0.3%. The swelling caused by these sulfate levels was not high enough to be influenced by the porosity or alkalinity of the mix. [ABSTRACT FROM AUTHOR]

To mitigate issues pertaining to reinforced concrete damage under the action of various strong corrosive ions in saline soil areas, the corrosion characteristics of reinforced concrete are investigated via electrochemical tests [performed based on electrochemical impedance spectroscopy (EIS) and polarization curves] and chloride ion concentration tests, as well as based on the degree of concrete damage. The morphology and microstructure of the reinforced concrete are characterized via field emission scanning electron microscopy and X-ray photoelectron spectroscopy. Two deterioration indices, i.e., the reinforcement corrosion current and concrete damage degree, are selected to establish a deterioration model of reinforced concrete based on the Weibull distribution function and to conduct a competitive failure analysis. The results show that the degree of deterioration of reinforced concrete increases nonlinearly with time. A surface crack was first observed in a specimen with 3.0% mass loss rate (MLR). The surface crack of the specimen and the corrosion depth of the internal steel bars expanded from 0.02 to 0.27 mm and from 55 to 130 μm , respectively, when the MLR increased from 3.0% to 4.5%. Based on the results, the corrosion current density and concrete damage degree can be used as effective indices for evaluating deterioration in reinforced concrete, and the changes with time in saline soil environment are in accordance with the Weibull distribution function. [ABSTRACT FROM AUTHOR]

Against the backdrop of escalating infrastructure budgets worldwide, a notable portion—up to 45%—is allocated to maintenance endeavors rather than innovative infrastructure development. A substantial fraction of this maintenance commitment involves combatting concrete degradation due to microbial attacks. In response, this study endeavors to propose a remedial strategy employing nano metals and repurposed materials within cement mortar. The methodology entails the adsorption onto eggshell membranes (ESM) of silver nitrate (ESM/AgNO3) or silver nanoparticles (ESM/AgNPs) yielding silver–eggshell membrane composites. Subsequently, the resulting silver–eggshell membrane composites were introduced in different proportions to replace cement, resulting in the formulation of ten distinct mortar compositions. A thorough analysis encompassing a range of techniques, such as spectrophotometry, scanning electron microscopy, thermogravimetric analysis, X-ray fluorescence analysis, X-ray diffraction (XRD), and MTT assay, was performed on these composite blends. Additionally, evaluations of both compressive and tensile strengths were carried out. The mortar blends 3, 5, and 6, characterized by 2% ESM/AgNO3, 1% ESM/AgNPs, and 2% ESM/AgNPs cement replacement, respectively, exhibited remarkable antimicrobial efficacy, manifesting in substantial reduction in microbial cell viability (up to 50%) of typical waste activated sludge. Concurrently, a marginal reduction of approximately 10% in compressive strength was noted, juxtaposed with an insignificant change in tensile strength. This investigation sheds light on a promising avenue for addressing concrete deterioration while navigating the balance between material performance and structural integrity. [ABSTRACT FROM AUTHOR]

Mud powders in aggregates are often found to cause deterioration of concrete properties. Based on a study of the mechanical properties of bridge deck leveling concrete (BDLC) containing different mud powders at various ages, the effects of mud powders on concrete durability were evaluated through rapid chloride permeability testing, freeze–thaw testing, and the coupling of salt solution and a freeze–thaw test. The properties of the interfacial transition zone (ITZ) were also investigated via microhardness testing. The test results showed that mud powder reduced the compressive strength, static compressive elastic modulus, and bond strength at early stages of curing. Moreover, mud powder was found to reduce the tensile properties and durability of concrete, with clay powder causing a greater reduction than mud powder in river sands and coarse aggregate. In addition, the width of the ITZ of concrete containing mud powder was found to increase by 23.1–48.3%. A significant correlation between the ITZ and the tensile properties, as well as the durability of concrete, was also observed. Therefore, in order to improve the tensile properties and durability of BDLC in seasonally frozen regions, the content of mud powder in the aggregates should be minimized according to the different compositions of mud powders. The coupling effect of salt solution and a freeze–thaw cycle should also be taken into consideration. [ABSTRACT FROM AUTHOR]

Alleviating cracks induced by the temperature rise in mass concrete has always been a research hotspot and engineering problem. In this study, a type of energy storage phase change low‐temperature rising concrete was designed and prepared to reduce the cracking risk of mass concrete. First, a type of energy storage coarse aggregate (ESA) was prepared using a semi‐dry method with cement and fly ash as matrix materials, mixed with carbon black (CB), carbon fiber (CF), and phase change material (PCM). Furthermore, the influence of these materials on the mechanical properties, microstructure, and pore structure of the ESA was studied. Subsequently, ESA was used to prepare phase change low‐temperature rising concrete, and its mechanical properties, thermal conductivity (TC), and internal temperature rise were investigated. The research results show that, except for the compressive strength of PCM‐15‐ESA, which is only 7% lower than that of the control, PC‐P0, other samples have no mechanical property deterioration. The double‐layer protection measures can effectively avoid the mechanical property deterioration of concrete induced by PCM leakage. The maximum internal temperature rise of concrete is reduced by 9.8°C, which greatly reduces the risk of cracking of concrete. [ABSTRACT FROM AUTHOR]

Among the construction processes of Portland cement concrete pavement (PCCP), the curing compound spraying process is one of the most important processes. If the curing compound spraying amount does not meet the standard or if the curing compound is not applied evenly, distresses occur at the early age of construction, ultimately causing deterioration in concrete pavement performance. The purpose of this study is to develop a real-time monitoring system for a curing compound spraying process based on the Internet of Things (IoT) and sensing technologies to improve the construction quality of concrete pavement. To achieve the goal of this research, we conducted various laboratory and field experiments. The curing compound spraying amount and sprayed status were measured and analyzed using flowmeters, image acquisition sensors, and an image processing program, and the data were provided to workers in real time and simultaneously transmitted to the IoT cloud to form a database. From this study, it is confirmed that the IoT-technology-based curing compound spraying amount and sprayed status monitoring systems can be successfully established to manage construction quality related to the curing of concrete pavement. [ABSTRACT FROM AUTHOR]

Pullout tests were performed on ordinary concrete (OC) specimens and basalt fiber–reinforced concrete (BFRC) specimens after exposure to high temperatures (20°C, 100°C, 300°C, 500°C, and 700°C). The effect of temperature on the bond property between rebars and concrete was studied. The measured data indicated that temperature below 300°C generates little damage to the bond performance for both OC and BFRC, while a temperature exceeding 500°C leads to sharp deterioration, which is similar to the changing pattern of concrete strength. The deterioration degree of bond strength and bond stiffness of BFRC specimens after exposure to high temperatures is lower than that of OC, while the deformation ability is better. In the end, a practical bond strength–slip constitutive model was established, taking account of the temperature in coefficients. [ABSTRACT FROM AUTHOR]

One of the most relevant deterioration mechanisms of reinforced concrete (RC) structures is the corrosion of steel bars by chloride ions. The service life of structures could be extended by monitoring this process. The lack of correlation data between chloride ion diffusion and the electrical field has meant that alternative methods have been developed in this paper. One such method considers diffusivity and the electrical field as non-constant, although they are usually assumed constant, that is, without there being any variability of the involved factors. Therefore, a multi-factorial diffusivity that accounts for the material characteristics and environmental variations is adopted. In addition, an innovative stochastic approach to evaluate the variation of the electrical field while accounting for the non-linear voltage distortion, which considers a multispecies model, has been proposed. More complete 1D/2D electro-mechanical models that are solved by advanced numerical and analytical solutions for electro-mechanical diffusion have been developed. Results show that spatiotemporal numerical models estimate the chloride concentration well, estimating more reliable scenarios to provide information on the safety situation of the structure and make it more sustainable by employing successful preventive treatments. [ABSTRACT FROM AUTHOR]

The primary cause of concrete deterioration is water permeability through it, which is typically studied using different codes of practices (German, European, and Indian standard codes). It has limitations such as long testing duration, equipment consuming large space, full penetration for low-strength concrete, and undetectable penetration for high-strength concrete. As a result of recognizing the need for a new method for testing low-strength concrete, this article presents a new approach called "Modified water permeability". To check the viability of the Modified method, the concrete mix is designed with and without fly ash based on cementing efficiency approach. The addition of fly ash has shown enhancement in resisting water penetration through concrete. The water penetration depth was reduced by around 10–48% with the addition of different percentages of fly ash, for effective w/c between 0.33 and 0.54. However, for low-strength concrete, the traditional method has shown complete water penetration. These specimens were tested effectively using a modified method. The improvement due to the addition of fly ash was observed in all strength ranges. For validation, the traditional and modified water permeability test results of standard concrete were correlated, which reveals a significant and logical trend. Moreover, the results revealed that the modified method is appropriate for both ordinary and standard concrete. [ABSTRACT FROM AUTHOR]

Calcium–silicate–hydrate (C–S–H), the most important phase of hydrated portland cement, is responsible for the cementitious system's mechanical properties performance and durability. In a severe environment, C–S–H often suffers from sulphate attack, leading to severe concrete deterioration. The present work describes a detailed mechanism of sulphate attack on C–S–H from 28 to 270 days of sulphate curing (10% Na2SO4 solution) using XRD, TGA, FTIR, 29Si-NMR and FESEM/EDX techniques. The results show that gypsum is the only sulphate-bearing product formed by decalcification of calcium hydroxide first and then of C–S–H. Decalcification enhances polymerization in the C–S–H structure as an additional Q3 peak was observed in FTIR and 29Si-NMR analysis. The microstructure of C–S–H becomes more crystalline as the sulphate curing period increases, as observed in FESEM micrographs. In addition, sulphate adsorption on C–S–H was identified through FESEM/EDX, which could play an important role in the deterioration of cementitious materials. [ABSTRACT FROM AUTHOR]

Purpose: The main purpose of this study is to examine the damage behavior of flexural members under different loading conditions. The finite element model is proposed for the prediction of modal parameters, damage assessment and damage detection of flexural members. Moreover, the analysis of flexural members has been done for the sensor arrangement to accurately predict the damage parameters without the laborious work of experimentation in the laboratory. Design/methodology/approach: Beam-like structures are structures that are subjected to flexural loadings that are involved in almost every type of civil engineering construction like buildings, bridges, etc. Experimental Modal Analysis (EMA) is a popular technique to detect damages in structures without requiring tough and complex methods. Experimental work conducted in this study concludes that a structure experiences high changes in modal properties once when cracking occurs and then at the stage where cracks start at the critical neutral axis. Moreover, among the various modal parameters of the flexural members, natural frequency and mode shapes are the viable parameters for the damage detection. Findings: For torsional mode, drop in natural frequency is high for higher damages as compared to low levels. This is because of the opening and closing of cracks in modal testing. When damage occurs in the structure, there is a reduction in the magnitude of the FRF plot. The measure of this drop can also lead to damage assessment in addition to damage detection. The natural frequency of the system is the most reliable modal parameter in detecting damages. However, for damage localization, the next step after damage assessment, mode shapes can be more helpful as compared to all other parameters. Originality/value: Effect on Dynamic Properties of Flexural Members during the Progressive Deterioration of Reinforced Concrete Structures is studied. [ABSTRACT FROM AUTHOR]

To evaluate influence of blast vibrations on the long-term mechanical deterioration and damage anisotropy of fresh concrete, blast vibration tests were conducted by preparing concrete test blocks at different curing ages. On this basis, the internal relationships of factors including the curing age during vibrations, vibration blast velocity, and number of blast vibrations with the damage evolution were investigated. The results show that fresh concrete is more susceptible to blasting vibration in the initial setting stage, which changes the bonding performance between cementing materials and aggregates. Then irreversible damage is generated along the main direction of vibration, and cumulative damage occurs with the increasing number of blast vibrations. Fresh concrete was affected most by blasting vibration at an age of 1 day, and the compressive strength at 28 days was reduced by 44.17% under a single vibration event. The damage increased slowly in the concrete at curing ages from 1 to 7 day. Blast vibrations with a velocity of less than 96.2 mm/s had a slight influence on changes in the compressive strength of concrete cured for 28 days. As the blast vibration velocity increased from 96.2 to 180.6 mm/s , the decrease rate of compressive strength in various directions accelerated and the strength decreased by as much as 40.59%. Therefore, it is suggested that the influence of the blast vibration velocity and the number of blast vibrations should be considered in alternating and parallel construction of blasting and concrete pouring work. Furthermore, blast vibration velocity, number of blast vibrations, and maximum attenuation coefficients of longitudinal wave velocities of vibrated concrete test blocks with the same curing age during vibrations differed along three directions, showing anisotropic characteristics. As the velocity and number of blast vibrations increased, the damage anisotropy became more significant. Therefore, the influence of anisotropy of cumulative damage evolution should be considered when establishing the safety criteria for fresh concrete subjected to blast vibrations. [ABSTRACT FROM AUTHOR]