Deterioration Of Concrete Structures Research Articles

A robust self-supervised approach for fine-grained crack detection in concrete structures

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.

Study on influencing factors and regularity analysis of eddy current method applied to detection of reinforcement corrosion

Abstract Rebar corrosion is one of the main reasons for the deterioration of concrete structures. In order to ensure the safe operation of reinforced concrete structures, it is necessary to detect the corrosion rate of rebars in time. This article adopts the eddy current method based on electromagnetic induction to detect steel corrosion, studies the mechanism of alternating current (AC) impedance change induced by steel corrosion in coils, and establishes a mathematical model between steel corrosion and coil AC impedance. Meanwhile, the quantitative relationship between excitation signal frequency, concrete thickness, coil parameters, and coil impedance is studied. Through experiments, it was found that in the early stages of steel corrosion, there is a linear relationship between the scanning peak value of the coil impedance and the mass loss rate of the steel bars, and the slope of the fitting curve decays exponentially with the increase of the concrete thickness. The method used in this paper has an absolute error of less than 0.01 and a relative error of less than 8 % in detecting the mass loss rate of rebars at the initial stage of steel corrosion. When the concrete thickness is less than 20 mm, the relative error is lower than 4 %.

Design of Concrete Colour Reference Charts for Monitoring of Deterioration in Concrete Structures

Design of Concrete Colour Reference Charts for Monitoring of Deterioration in Concrete Structures

An investigation of the effect of high temperature on the strength compression and ultrasonic pulse velocity of self-compacting concrete

One of the most significant mechanisms of deterioration in self-compacting concrete (SCC) structures over the course of their service life is exposure to elevated temperatures. For this reason, the effects of elevated temperatures on the residual mechanical properties of SCC made of various cementitious additions (silica fume (SF), limestone filler (LF), and crushed dune sand (SD)) was investigated via partially substituting amount of Portland cement in the SCC. The SCC was formed and heated with the coupling procedure of heating-cooling at ambient temperatures ranging from 20, 150, 400, 600, and 800 °C. The compressive strength (CS) and ultrasonic pulse velocity (UPV) were measured after cooling at room temperature of 20 °C. The findings show that CS and UPV exhibit intriguing outcomes for all self-compacting concretes. Otherwise, the UPV decreases with temperature in the range of 250 and 800 °C. In addition, at 600 °C, SCC-SF and SCC-SD have the highest residual compressive strengths, 31.20 and 23.80 MPa, respectively.

Chloride-induced concrete deterioration monitoring using advanced ultrasonic pulse wave analysis based on convolutional neural network

This research explores the potential of deep learning techniques, specifically the convolutional neural network (CNN) architecture, for classifying concrete crack levels based on an acceptable threshold of concrete cracking. The classification model utilizes ultrasonic pulse wave data collected from concrete cube specimens before and after undergoing an accelerated corrosion process. A total of 108 concrete specimens, representing three different mix designs, three corrosion levels, and four concrete cover thicknesses, were utilized in this study. The collected data was employed to train CNN models, specifically leveraging the GoogLeNet and SqueezeNet architectures. Various input sampling rates, input lengths, and hyperparameters were explored to determine the optimal training setup, yielding the best prediction performance. The results demonstrate that the optimized models achieve an 84% accuracy in distinguishing cracks below and above the acceptable threshold. Therefore, it can be concluded that the CNN method holds potential for in-situ sensors aimed at monitoring chloride-induced deterioration in concrete structures.

Physico-Mechanical Properties of Geopolymer Mortars for Repair Applications: Impact of Binder to Sand Ratio

Deterioration of concrete structures made with ordinary portland cement (OPC) as a binder is inevitable, and this requires repair or rehabilitation using appropriate repair materials. A strong and highly adhesive repair material is very important in order to ascertain the safety of damaged concrete structures. The existing repair materials, especially those that utilized conventional OPC-based materials, appear to require a certain curing condition, which prior studies have revealed to result in a weak link between the repair material and the repaired structures. Hence, an alternative material which is geopolymer mortar was utilized in this study as a repair material, and the impact of geopolymer mortars with various binder-to-sand ratios was evaluated. The physical and mechanical properties of the geopolymer mortars were assessed in addition to their performance as a repair material in terms of their bonding characteristics to conventional concrete. Findings from this study revealed that geopolymer mortar with a binder-to-sand ratio of 1:2 exhibited the highest bonding strength. In addition, geopolymer mortars with a binder-to-sand ratio of 1:3 to 4:1 exhibited better bonding strength compared to when geopolymer paste was used.

A coupled thermo-hydro-mechanical framework for simulating the failure response of asphalt concrete under freezing conditions

Freezing-induced damage occurs in extremely cold regions in the form of sudden and simultaneous formation of cracks in dry and wet asphalt concrete. This work investigates the mechanical response, up to and including final failure, of dry and partially saturated asphalt concrete at freezing temperatures as low as −30° (−22 °F). A coupled thermo-hydro-mechanical constitutive framework is proposed within the context of finite element simulation. The framework contains nonlinear viscoelastic-viscodamage constitutive equations, the swelling strain effect associated with the freezing of water content, and the moisture damage constitutive equation. The stress induced in dry and partially saturated asphalt concrete samples due to reducing temperatures is simulated and compared with those of a studied experiment, and an excellent agreement is achieved in terms of the critical features, including the final brittle failure and the swelling effect. A parametric study is then performed to discover the effects of the microstructural constituents of asphalt concrete on its mechanical response under freezing conditions. This work provides a reliable computational framework that can predict deterioration and damage in asphalt concrete structures in extremely cold weather and further leads to the development of novel construction materials that can resist the negative effects of cold temperatures, e.g., in the Arctic.

Experimental based time-dependent reliability assessment of corrosion initiation for PC girders in frozen marine environment

Chloride induced corrosion is the main reason for the deterioration of concrete structures in marine environments, and the prediction of corrosion initiation life is one of the greatest challenges for preventative maintenance. To conduct a corrosion initiation assessment of PC girders in frozen marine environment and support preventative maintenance, a time-dependent reliability assessment method is developed. Long-term exposure experiments and in-house tests are combined to calibrate the chloride diffusion model, and then a probabilistic diffusion model is proposed based on the randomness of the key model parameters. Through the analysis of the target reliability index of corrosion initiation, the risk-function based time-dependent reliability assessment method is developed. Finally, a case study is introduced to illustrate the application of the proposed method. It is found that the surface chloride concentration on concrete structures in frozen marine environments increases at the beginning of service life and it tends to be stabilize when the service time is around 9–10 years. The age reduction factor of chloride diffusion can be described as the linear function of cementitious composition. The target reliability indices of corrosion initiation are suggested as 2.46, 1.50 and 1.13 for the referenced periods of 1, 10 and 20 years. The corrosion initiation life is very sensitive to the tensile stress level of concrete, and it decreases linearly with the increasement in tensile stress when the stress is not higher than 2 MPa.

Enhancing the hydrophobicity of cement-based materials by fabricating microstructured surfaces: Experimental and numerical study

In cold and humid regions, deterioration and failure of concrete structures are usually closely related to the entry of external water. Increasing attention is being paid to hydrophobic surfaces to reduce the entry of external water and thus improve the durability of concrete structures. In this manuscript, the effect of microstructure on the surface hydrophobicity of hydrophobic rubberized concrete was investigated by wettability tests, and the optimal microstructure morphology that can further improve the surface hydrophobicity was derived. In addition, the multiple-relaxation-time lattice Boltzmann method was used to investigate the wettability of microstructured surfaces of hydrophobic rubberized concrete, and the effect of different microstructures on the contact angle of water droplets on concrete surface was investigated by numerical simulations. The predicted results obtained from the numerical simulations were compared with the analytical and experimental results to verify the accuracy of the numerical models.1.

A Micromechanical-Based Semi-Empirical Model for Predicting the Compressive Strength Degradation of Concrete under External Sulfate Attack.

As one of the most harmful ions in the environment, sulfate could cause the deformation and material deterioration of concrete structures. Models that accurately describe the whole chemo-transport-mechanical process of an external sulfate attack (ESA) require substantial computational work and contain complex parameters. This paper proposes a semi-empirical model based on micromechanical theory for predicting the compressive strength degradation of concrete under an ESA with basic properties of the undamaged material and limited computational effort. A simplified exponential function is developed for the total amount of the invading sulfate, and a second-order equation governs the chemical reaction. A micromechanical model is implemented to solve the mechanical response caused by an ESA. The model is able to describe the compressive stress-strain behavior of concrete subject to uniaxial loading in good agreement with the experimental results. For the case of a sulfate-attacked material, the relationship between compressive strength and expansion is calculated and validated by the test results. Finally, the deterioration process of compressive strength is predicted with the test results of deformation.

Two-stage deterioration model updating of RC structures in marine environment using long-term field inspection data

For the deterioration of reinforcement concrete (RC) structures in marine environment at various stages, models on chloride penetration, crack initiation and crack propagation have been proposed and studied in literature. However, to be applied to real existing structures, these models, usually associated with significant uncertainties, have to be calibrated and modified with long-term in-situ inspection data. Toward this goal, this paper develops a two-stage updating framework to incorporate measured data into existing models to achieve a more realistic modeling of deterioration process. To improve the computation efficiency, the framework can be integrated with simple rejection sampling and other advanced sampling techniques such as the modified sequential adaptive importance sampling (SAIS). A real case study of high-pile wharf structure in Guangzhou Port is carried out to demonstrate the updating effect of the proposed framework. The observed data of chloride content profile and steel bar corrosion depths from one field inspection are used to construct the likelihood functions in the two updating stages. Comparison between the results of the first and second updating stages is made, and the sensitivities of different parameters to the data are analyzed, subsequently the year of reinforcement corrosion initiation and the evolution of corrosion depth are inferred using these results. At last, the data from an early inspection are also incorporated to investigate the impact of two inspections on updating effects.

Infrared imaging for detection of defects in concrete structures

Deterioration of concrete structures is an issue that affects the entire world and is brought on by various causes like climatic conditions, aging, attack of aggressive media, etc. Periodic inspections and proper maintenance are crucial to prevent the degradation of structures. Conventionally, the condition of the structures is monitored visually but over a while, non-destructive evaluation (NDE) technologies have gained significance and are expected to be successfully used for the inspection and management of civil structures. Infrared imaging is an effective NDT tool to monitor the health of civil structures. In this study, Infrared Thermography (IRT), an image-based method, is introduced and implemented for the assessment of concrete structures. Experiments on cement concrete cubes were conducted to investigate and enhance the applicability of the infrared thermography technique. The results are quite promising and helps to detect defects like delamination, voids, and cracks, etc. as the IR camera can pick-up the difference in temperature between sound and defective regions. However, the utilization of IRT for inspection poses many challenges but they can be overcome by combining it with other techniques like finite element method, acoustic emission and ultrasonic guided waves. Hence, the infra-red thermography technique is an excellent technology for practically evaluating concrete structures.

PH sensor using aniline blue and functionalized nylon for monitoring the final stage of concrete carbonation

The construction industry is one of the most significant contributors to global warming, with 5% of the world’s CO2 emissions coming from the manufacturing process of cement. Therefore, to slow the rate of global warming, efforts are needed to increase the lifespan of infrastructure via structural health monitoring and timely repair. Carbonation is often cited as a significant cause of the deterioration of concrete structures and is measured using a destructive testing in the current structural code. However, since this method is time-consuming, costly, and labor-intensive, the development of pH sensors has been required for monitoring carbonation. Most pH sensors developed so far were manufactured using a physical entrapment method, so they are vulnerable to leaching and cannot guarantee long-term durability. A few pH sensors ensuring durability through covalent immobilization have also been proposed, but they pose limitations since most of them can only monitor the early stage of carbonation. Therefore, this study sought to develop a pH sensor that can be used to measure the final stage of carbonation. The sensor was manufactured via functionalization of nylon using formaldehyde and chloroacetyl chloride and then covalent bonding with aniline blue. The sensor showed a significant color change in the pH ranging from 5 to 10 and exhibited sufficient response within 30 min and reversibility. In addition, the sensor was stable even in high pH environments such as concrete, and its applicability was verified inside the concrete.

Experimental Investigation on a Novel Temperature-Controlled Phase Change Aggregate Concrete: Thermo-Mechanical Properties and Hydration Heat Control.

To reduce the structural deterioration of mass concrete structures from temperature cracks, and lower energy consumption caused by the traditional mass concrete hydration heat cooling process, this paper reports the preparation of concrete temperature-controlled phase change aggregate (PCA) by a vacuum compaction method using light and high-strength black ceramite and No. 58 fully refined paraffin wax as phase change material (PCM), and the encapsulation technology of the aggregate by using superfine cement and epoxy resin. Further, through laboratory tests, the cylinder compressive strength, thermal stability and mixing breakage rate of the encapsulated PCA were tested, and the differences in mechanical properties such as compressive strength, flexural strength and splitting tensile strength between phase change aggregate concrete (PCAC) and ordinary concrete were studied. A test method was designed to test the heat storage effect of PCA, and the temperature control effect of PCAC was analyzed based on the law of conservation of energy. The research conclusions are as follows: (1) Both superfine cement and epoxy resin shells increase the strength of the aggregate, with the epoxy resin increasing it more than the superfine cement. The thermal stabilization of the PCA is good after encapsulation of superfine cement and epoxy resin. However, PCA encapsulated in superfine cement is more easily crushed than that encapsulated in epoxy resin. (2) Under the condition of water bath heating and semi-insulation, when the water bath temperature reaches 85 °C, the temperature difference between the PCA and the common stone aggregate can be up to 6 °C. Based on the law of energy conservation, the test results will be converted to mass concrete with the same volume of aggregate mixture;, the difference of PCAC and ordinary concrete temperature can be up to 10 °C, so the temperature control effect is significant. (3) The mechanical properties of PCAC with 100% aggregate replacement rate compared to ordinary concrete are reduced to varying degrees, and the performance decline of the epoxy-encapsulated PCA is smaller than that encapsulated with superfine cement; in an actual project, it is possible to improve the concrete grade to make up for this defect.

Approximating Dynamic Elastic Modulus of Concrete for an Old Aqueduct Using Dynamic Tests and BP Neural Network

Monitoring the degradation of the dynamic elastic modulus (Ed) of concrete is of great importance to track the durability deterioration for hydraulic concrete structures. For the aqueduct under investigation in this study, the dynamic elastic modulus of bent frames and moment frame supports (Ed-frame), the dynamic elastic modulus of arch trusses (Ed-arch) and the shear stiffnesses of the asphaltic bearings of U-shaped flumes (Kflume) are the main parameters to define the dynamic behavior of the structure, which have direct correlation with its vibrational characteristics and thus practicably can be estimated by a BP (back-propagation) neural network using modal frequencies as inputs. Since it is impossible to obtain sufficient experimental field data to train the network, a full-scale 3D FE model of the entire aqueduct is created, and modal analyses under different combinations of Kflume, Ed-arch and Ed-frame are conducted to generate the analytical dataset for the network. After the network’s architecture is refined by the cross-validation process and its modeling accuracy verified by the test procedure, the primary modal frequencies of the aqueduct obtained from in situ dynamic tests are put into the network to obtain the final approximations for Kflume, Ed-arch and Ed-frame, which sets an evaluation baseline of the general concrete Ed status for the aqueduct and indicates that the makeshift asphaltic bearings of U-shaped flumes basically can be treated as a three-directional hinge in the FE model. It is also found that more inputs of modal frequencies can improve the prediction accuracy of the BP neural network.

Effects of Bamboo Leaf Ash on Alkali-Silica Reaction in Concrete

The construction industry is generally faced with so many challenges of which deterioration in concrete structures caused by Alkali-silica reaction (ASR) is one of the pressing challenges. This reaction induces expansion in concrete, resulting in its eventual cracking and subsequent failure. Research direction is being geared towards obtaining properties of pozzolanic concrete of recently discovered different biogenic pozzolans such as bamboo leaf ash (BLA). BLA has been proven to be acceptable in terms of compressive strength and some other properties but few researches have been performed on the impacts of ASR on BLA concrete structures. This research work focuses on investigating the properties of BLA through X-ray diffraction and fluorescence analyses, and its effectiveness in resisting or eliminating ASR that may be present in concrete. Tests were performed on concrete bars soaked in NaOH at a temperature of 80 oC to determine the possible reactivity of aggregates to ASR. In addition, workability and the compressive strengths of BLA concrete at different percentage levels were determined after curing for 7, 28 and 56 days. The findings of the research show that BLA improves the workability of fresh concrete, however, it causes a decline in the compressive strength of concrete when compared with the strength of conventional concrete. Also, BLA has no detrimental effect on the linear expansion of concrete. This study recommends that a 5% partial replacement of cement with BLA will give effective performance when used in areas where strength is not the major priority. Alkali-silica reaction, bamboo leaf ash, compressive strength, concrete, construction, linear expansion, pozzolans

A comprehensive assessment of durability and service life prediction of concrete structures in the simulated tidal zone of the South China Sea considering measures to enhance concrete durability

The island and reef area in the South China Sea is characterized by high temperature, high salinity, high humidity and windiness, which can accelerate the deterioration of concrete structures, requiring some measures to improve the durability of concrete. To improve the poor durability of concrete structures in the tidal zone of island and reef area in the South China Sea, the influence of multiple factors on concrete structures is investigated. The tests of mass, ultrasonic velocity, flexural strength and chloride ion content are used to analyze the deterioration of concrete and the service life of concrete structures. The results show that the performance of concrete under the simulated tidal environment of island and reef area is enhanced first and then attenuated, and the relationship of the mass retention, relative dynamic elastic modulus and strength retention between any two parameters is linear. Compared with concrete with a water cement ratio of 0.53 (C(-0.53)) in the paper, the deterioration degrees of C(-0.53) with calcium nitrite (CN), C(-0.53) with amino alcohol corrosion inhibitor (AA), C(-0.53) with hydrophobic pore-blocking ingredient corrosion inhibitor (HPA), C(-0.53) with salt crystallization inhibition (UMP), concrete with a water cement ratio of 0.31 (C-0.31) and concrete with a water cement ratio of 0.26 (C-0.26) decrease by 0.5%, 1.0%, 1.5%, 1.8%, 4.5% and 9.1% respectively. In addition, compared with only chloride diffusion coefficient, the multiparameter evaluation is more suitable for the chloride diffusion behavior in concrete under the simulated tidal environment of island and reef area. Compared with C(-0.53), the service life of CN, AA, HPA, UMP, C-0.31 and C-0.26 increase by at least 1.3 times, 1.9 times, 1.7 times, 6.7 times, 3.3 times and 5.5 times respectively. This study provides theoretical guidance and technical support for the durability of island and reef engineering.

Chloride diffusion modeling of concrete using tree‐based forest models

AbstractReinforced concrete structures can experience various harsh environments during their service life, among which chloride ion exposure, especially in marine environments, can cause the durability reduction and deterioration of concrete structures. Artificial intelligence (AI)‐based modeling of the non‐steady‐state apparent chloride diffusion coefficient (DC) of concrete for a long exposure time using the experimental field results can assist in identifying the influential factors and better estimating the service life of a concrete structure. In this study, two novel extensions of ensemble AI algorithms, including genetic programming forest (GPF) and linear genetic programming forest (LGPF) algorithms, were proposed to model the DC of concrete. The experimental field data were gathered from the literature. Different structures of the proposed ensemble methods were developed and examined, and the best‐developed model was selected for further analysis, including sensitivity analysis and parametric study. In addition, the random forest (RF) method was used as the control ensemble technique to have a comparison. The results show that the best LGPF model possesses superior performance than the best‐developed GPF and RF models. In addition, the results show that silica fume‐to‐binder ratio, exposure time, and exposure conditions have the most significant impacts on the DC of concrete. This study contributes to the civil engineering practice by developing a new tool to model the DC of concrete that facilitates the durability assessment of concrete structures.

Impact of elevated temperatures on properties of concrete with blast furnace slag as partial replacement of fine aggregate as green building material

Concrete is widely used as construction material because it’s high durability and fire resistance. When any structures exposed to fire, its room temperature will raise continually, which cause deterioration of concrete structures. During high temperatures concrete loss it structural capacity and it may require strengthen and rehabilitations. This paper is an efforts to investigate the effect of elevated temperature on conventional concrete and concrete with granulated blast furnace slag( GBFS) as partial replacement of fine aggregate in proportions of 20%, 40 % and 60 % and 1 % steel fibers. The strength parameter was determine and compared with conventional concrete at controlled elevated temperatures like 200°C, 400°C, 600°C, 800°C, 1000°C for 0.5 hour, 1 hour and 1.5 hour constant heating and tested after 1.0 hours of natural cooling. This experimentation shown the strength of concrete with GBFS 40 performs well at all elevated temperatures as compared with conventional concrete.

Exploring capillary adsorption of corrosive medium in epoxy resin-modified calcium-silicate-hydrate channels

In coastal environment development and island construction, cement-based materials are crucial, but they are exposed to high temperatures, humidity, salt, and weathering in marine environments, leading to the deterioration of offshore concrete structures' durability. To mitigate these effects, epoxy resin, a polymer material with excellent adhesion with cement-based materials and chemical corrosion resistance, can slow down harmful ion erosion and improve concrete structure durability. This paper proposes a molecular dynamics simulation model to investigate the transport of pure water and NaCl solution in calcium-silicate-hydrate (C-S-H) gel pore channels with and without epoxy coating. The study demonstrates that epoxy resin can effectively slow down water molecule and ion transport in the C-S-H channels. When the solution passes through the C-S-H gel pore channel, the water molecules occupy the adsorption sites of the epoxy molecules, resulting in partial exfoliation of the epoxy resin. The exfoliated epoxy resin forms an enhanced hydrogen bonding network with the water molecules and forms ion pairs with the ions, which induces the ions and water molecules to gather around the epoxy molecules and form a larger cluster structure, thus slowing down the migration of ions and water molecules in the C-S-H pore channel.