Durability Of Reinforced Concrete Research Articles

Prediction of durability of reinforced concrete based on hybrid-Bp neural network

Mix proportion design has a significant influence on the durability of reinforced concrete (RC). Conventional simple equations encounter challenges in effectively guiding the enhancement of durability in the design process. To address this issue, a backpropagation neural network (BPNN) model with a topological structure of 6–16–2 is devised to build a prediction model for RC durability, offering both forward design and reverse guidance for determining optimal mix proportion. Moreover, the model is optimized by the Bat Algorithm (BA), Ant Colony Optimization Algorithm (ACO), and Particle Swarm Optimization (PSO) Algorithm. The input layer parameters of the model consist the water-binder ratio and the quantity of cement, coarse aggregate, river sand (RS), fly ash (FA), slag, while the output layer parameters include the failure time for corrosion current density of reinforcement (T1) and the failure time for concrete damage degree (T2). The dataset for the model comprises 100*2 sets, which are divided into 70*2 sets for training data, 15*2 sets for validation data, and 15*2 sets for testing data. The relationship between the experimental raw materials and the durability of RC was determined through correlation analysis, and comparative analysis was conducted on the durability evaluation indices for RC. The results indicate a positive correlation between cement content and the durability of RC, whereas the content of RS, coarse aggregate, FA and slag, and water-binder ratio exhibit negative correlation with concrete durability. Among the RC groups, the A3 group demonstrated the highest performance, and the D group stood out as the optimal mineral admixture group. Utilizing the PSO-BPNN model, the following performance indices were predicted for T1: R2=0.850, MAE=38.14, MAPE=0.094, RMSE=47.218, and for T2: R2=0.872, MAE=34.541, MAPE=0.071, RMSE=42.355. Consequently, the PSO-BPNN model demonstrates the highest accuracy in predicting the correlation between concrete mix proportions and the durability of RC, thereby offering valuable guidance for the mix proportion design of RC.

Analysis of Reinforced Concrete Durability Against Corrosion Due to Chloride Penetration

Corrosion in reinforced concrete is a serious problem in the construction industry as it can reduce the strength and service life of concrete. Chloride penetration has been identified as one of the main causes of corrosion in reinforced concrete. Therefore, in this study, an analysis of the resistance of reinforced concrete to corrosion due to chloride penetration was conducted. The testing method included varying the concentration of chloride in seawater and testing the compressive strength of reinforced concrete after exposure to chloride for a certain period of time. The results showed that the higher the concentration of chloride, the faster the corrosion occurred and the lower the compressive strength of reinforced concrete. Therefore, prevention efforts are needed by using additives such as corrosion inhibitors or reducing the chloride content in the concrete mix to increase the resistance of reinforced concrete to corrosion due to chloride penetration. From the test results, the use of 5% silica fume by weight of concrete increased the compressive strength of concrete by 13% and reduced the rate of chloride penetration by 30%, as assessed from the chloride ion penetrability value.

Effect of fly ash on compressive strength, carbonation and corrosion resistance of reinforced concrete: a systematic review

Purpose The purpose of this paper is to study and analyze the effects of fly ash (FA) as a mineral admixture on compressive strength (CS), carbonation resistance and corrosion resistance of reinforced concrete (RC). In addition, the utilization of inexpensive and abundantly available FA as a cement replacement in concrete has several benefits including reduced OPC usage and elimination of the FA disposal problem. Design/methodology/approach Reinforcement corrosion and carbonation significantly affect the strength and durability of the RC structures. Also, the utilization of FA as green corrosion inhibitors, which are nontoxic and environmentally friendly alternatives. This review discusses the effects of FA on the mechanical characteristics of concrete. Also, this review analyzes the impact of FA as a partial replacement of cement in concrete and its effect on the depth of carbonation in concrete elements and the corrosion rate of embedded steel as well as the chemical composition and microstructure (X-ray diffraction analysis and scanning electron microscopy) of FA concrete were also reviewed. Findings This review provides a clear analysis of the available study, providing a thorough overview of the current state of knowledge on this topic. Regarding concrete CS, the findings indicate that the incorporation of FA often leads to a loss in early-age strength. However, as the curing period increased, the strength of fly ash concrete (FAC) increased with or even surpassed that of conventional concrete. Analysis of the accelerated carbonation test revealed that incorporating FA into the concrete mix led to a shallower carbonation depth and slower diffusion of carbon dioxide (CO2) into the concrete. Furthermore, the half-cell potential test shows that the inclusion of FA increases the durability of RC by slowing the rate of steel-reinforcement corrosion. Originality/value This systematic review analyzes a wide range of existing studies on the topic, providing a comprehensive overview of the research conducted so far. This review intends to critically assess the enhancements in mechanical and durability attributes (such as CS, carbonation and corrosion resistance) of FAC and FA-RC. This systematic review has practical implications for the construction and engineering industries. This can support engineers and designers in making informed decisions regarding the use of FA in concrete mixtures, considering both its benefits and potential drawbacks.

Reinforced Concrete Durability Design Through a Semi-probabilistic Approach

This study provides a semi-probabilistic approach to durability design of reinforced concrete structures, subjected to carbonation-induced corrosion. The method was developed from an existing approach and using comprehensive data collated from the literature. A statistical model for predicting accelerated carbonation coefficient, using as input variables mix proportions and test conditions was also generated. The performance of the proposed method was assessed and proved appropriate. Besides delivering a more consistent semi-probabilistic method to design for the avoidance of unforeseen carbonation-induced corrosion problems, the developed statistical model to estimate the accelerated carbonation coefficient is a useful tool on the mix design, from the standpoint of conforming with the accelerated carbonation coefficients obtained through the semi-probabilistic method.

Limitations in Modelling Reinforced Concrete Durability

The design processes for reinforced concrete are changing. More often, durability targets are being achieved by using modelling. This paper compares some of the models available and the precision undertaken to obtain the data that underpins the calculations, and it reflects on the change in the environment that is known to be occurring. In addition, a review of the sustainability implications of durability is considered. It is concluded that there may be more sustainable methods to achieve a long life than simply increasing cement contents and covers.

Influence of deicing salt on the surface properties of concrete specimens after 20 years

The low temperature of ice and snow all year round in Sweden leads to the common use of deicing salt to melt the roads, but the splash of the deicing salt on the reinforced concrete (RC) on both sides of the roads brings about the deterioration of the durability of RC components. The chloride ions diffusion coefficient is an important parameter to evaluate the durability of RC. By adopting the rapid chloride migration method (RCM) and replacing chloride ions with iodide ions, the samples of concrete blocks exposed on the side of the highway for 20 years were taken. This is directly beneficial to study the influence of the type, content, and water-cement ratio of mineral additions on the diffusion and distribution of iodide ions in concrete and analyze the surface environmental effect depth of concrete. The influence of chloride ions on the pore structure and microscopic morphology of concrete also were studied by scanning electron microscope-energy dispersive spectrum and X-ray diffractometer. The results show that as the water-cement ratio increases, the surface environmental effect depth of concrete and the diffusion area of iodide ions gradually increase. Silica fume and ground granulated blast furnace slag (GGBF slag) have an impediment to the diffusion of iodide ions, especially with the high volume of the GGBF slag (about 50%), the diffusion of iodide ions is very low. In general, this research is helpful to provide some empirical ideas and suggestions for the manufacturing and durability design of concrete structures in marine environments or deicing salt road environments.

Reinforced Concrete Durability in Marine Environments DURACON Project: Long-Term Exposure

This paper presents the results, after a long-term evaluation in marine environments, from an Ibero-American project called “Effect of the environment on reinforcement durability” (DURACON). This p...

Reinforced Concrete Durability in Response to Aggregate Proportioning

Reinforced Concrete Durability in Response to Aggregate Proportioning

Research on Factors Affecting Reinforced Concrete Durability

Reinforced concrete is widely used in building structures. However, due to its corrosion, deterioration loss is more and more outstanding. Therefore, besides building material mechanical properties and the cost, the structural designer also need to focus on the durability of reinforced concrete. Effects of reinforced concrete durability factors mainly include corrosion of steel in reinforced concrete, freeze-thaw cycle, soft water, high temperature and chemical erosion. Understanding the influencing factors will help control the concrete deterioration, reduce the structural reparation and maintenance costs, and thereby reduce the life cycle cost of structure.

The Study of Steel Fiber Reinforced Concrete Durability Based on Damage Mechanics

In order to substitute steel reinforcement with steel fiber reinforced concrete, this paper studied steel fiber reinforced concrete durability based on damage mechanics. During recent years, steel fiber reinforced concrete has gradually advanced from a new, rather unproven material to one which has now attained acknowledgment in numerous engineering applications. The use of randomly distributed short fibers to improve the physical properties of a brittle or quasi-brittle matrix is an old concept. Most of the steel fiber reinforced concrete durability research just to solve a specific problem and no system of the structure performance degradation in certain circumstances. A formulation to model the mechanical behavior of high performance fiber reinforced cement composites with arbitrarily oriented short fibers. The formulation can be considered as a two scale approach, in which the macroscopic model, at the structural level, takes into account the micro-structural phenomenon associated with the fiber-matrix interface bond/slip process.

Influence of Additives on Reinforced Concrete Durability

The article presents the results of the research on carbonation and chloride induced corrosion mechanisms in reinforced concrete structures, based on three commercially available concrete admixtures: Xypex Admix C-1000, Penetron Admix and Elkem Microsilica. Carbonation takes place due to carbon dioxide diffusion, which in the required amount is present in the air. Chlorides penetrate concrete in case of the use of deicing salt or structure exploitation in marine atmosphere. Based on the implemented research, Elkem Microsilica is the recommended additive for the use in aggressive environmental conditions. Use of Xypex Admix C-1000 and Penetron Admix have only average resistance to the aggressive environmental impact.

Influence of global warming on durability of corroding RC structures: A probabilistic approach

Chloride ingress and carbonation cause corrosion of reinforced concrete (RC) structures affecting its operational life. Experimental evidence indicates that these deterioration processes are highly influenced by CO2 emissions and climatic conditions in the surrounding environment – i.e., temperature, humidity, etc. Since studies on global warming announce changes in climate, the impact of changing climate on RC durability should also be considered. This paper links RC deterioration mechanisms to CO2 emissions and global warming. Based on various studies on climate change, models for estimating the effect of CO2 emissions and temperature/humidity changes due to global warming are described. Furthermore, various scenarios of global warming that can be used to assess the effect of climate change in structural reliability are proposed. The proposed approach is then illustrated with a numerical example that calculates the probability of failure of a RC bridge beam for future climate scenarios. The paper then outlines some adaptation strategies, particularly focusing on the needs for risk-based selection of optimal adaptation measures.

Stochastic improvement of inspection and maintenance of corroding reinforced concrete structures placed in unsaturated environments

Multiple constraints imposed by economic, social and environmental considerations lead maintenance planning optimization to a major challenge for designers, owners and users of infrastructure. This study focuses on the management of reinforced concrete (RC) structures placed in chloride-contaminated atmospheres. Under these exposure conditions, chloride penetration generates corrosion of the reinforcing bars reducing the RC durability. Therefore, modeling the deterioration process as well as the maintenance actions carried out during the operational life becomes paramount for the formulation of a comprehensive maintenance strategy. This paper presents a new methodology for improving the performance of maintenance strategies for corroding RC structures. The proposed approach is based on preventive maintenance and combines: a numerical model of chloride penetration, Markov processes and decision theory. The uncertainty related to material properties, model and environmental actions as well as the effect of imperfect inspections are also integrated in the model. The aforementioned points are illustrated with a numerical example. In general, the overall results indicate that the proposed methodology can be useful to improve the costs of a given maintenance strategy by ensuring appropriate levels of serviceability and safety.

Durability design of reinforced concrete structures: a comparison of the use of durability indexes in the deemed-to-satisfy approach and the full-probabilistic approach

To show the application of the chloride conductivity index test in service life prediction (SLP) using both the deemed-to-satisfy and probabilistic approaches to performance-based durability design. It is desirable to adopt a performance-based approach with respect to durability design of reinforced concrete (RC) structures. This is based on the perception that the durability of RC is achieved when the limiting value from an established test method is met. In South Africa, the durability index (DI) approach has been developed, which permits performance-based specifications for durability of RC. This approach involves the application of a test method together with a SLP model. This integrated approach links material properties directly with the expected service life of RC structures and environmental conditions. Two DIs are relevant to degradation processes in RC: the chloride conductivity index which is related to chloride ingress, and the oxygen permeability index related to carbonation. The study presented here focuses on the application of the chloride conductivity index as the main input parameter of a SLP model concerned with chloride-induced reinforcement corrosion. The methodology and output of the SLP model as applied in the deemed-to-satisfy approach are compared with those of the probabilistic approach. Both approaches are exemplified using a concrete pier cast in situ in a marine environment. The performance-based durability specifications from the deemed-to-satisfy approach are found to be more conservative compared to those of the probabilistic approach.

The Reinforced Concrete Durability and Rebar Erosion Monitoring

On the basis of the advantages of low construction cost, remarkable dynamics property, easy cast moulding and more controllable construction, the reinforced concrete construct are widely applied in buildings and main structures of constructions in China. However, the reinforced concrete is found more or less aging after many years’ utilization and erosion from the environment, which will lead to a hidden risk to affect its functions. After technical development for decades, the concrete can assure its durability under normal situation, yet the function would be deteriorated due to the erosion from the complex and harsh environment to make it hardly reach its designed service life. With the assist of CorroWatch erosion monitor system, the concrete structures’ erosion can kept watched on to obtain the depassivation development and information feedback of some key data dynamically and in long term so as to foresee precisely the erosion starting time. The newly cast concrete depassivation frontline is located on concrete surface and will tend to go through the protective layer and penetrate towards rebar as time goes on. Its structure service life can be enhanced with the re-designed durability in terms of the mentioned characters and do well the erosion proof measures.

The Reinforced Concrete Durability and Rebar Erosion Monitoring

On the basis of the advantages of low construction cost, remarkable dynamics property, easy cast moulding and more controllable construction, the reinforced concrete construct are widely applied in buildings and main structures of constructions in China. However, the reinforced concrete is found more or less aging after many years’ utilization and erosion from the environment, which will lead to a hidden risk to affect its functions. After technical development for decades, the concrete can assure its durability under normal situation, yet the function would be deteriorated due to the erosion from the complex and harsh environment to make it hardly reach its designed service life. With the assist of CorroWatch erosion monitor system, the concrete structures’ erosion can kept watched on to obtain the depassivation development and information feedback of some key data dynamically and in long term so as to foresee precisely the erosion starting time. The newly cast concrete depassivation frontline is located on concrete surface and will tend to go through the protective layer and penetrate towards rebar as time goes on. Its structure service life can be enhanced with the re-designed durability in terms of the mentioned characters and do well the erosion proof measures.

The Study of Fuzzy Reliability of Concrete Durability after Corrosion of Steel-Bars

Based on the mechanism, influencing factors and their fuzziness of reinforced concrete (RC) cracking caused by corrosion of steel bars, fuzzy reliability of RC durability failure due to corrosion expansion of steel bars is analyzed adopting the mathematic model of fuzzy probability. The method having the advantages of explicit concept, convenient calculation and stable results which is proved by the examples accords with the actual situation and can be applied to the engineering practice.

Behaviour of corroded steel in a Ca(OH)<sub>2</sub>-saturated solution and in cement mortar. Possibility of rehabilitation

The present study compared the response of rust-free and corroded steel electrodes in Ca(OH)2-saturated solutions and in cement mortar, essentially defined in terms of polarization resistance as measured with gravimetric, metallographic and electrochemical methods. Answers were sought for the following questions, which persist despite the use of reinforced concrete (RC) in building for over a century: At what corrosion rate is RC durability seriously compromised? Does restoration of the initial conditions in properly manufactured concrete guarantee repassivation of corroded steel? Does the use of inhibitors enhance repassivation? Does the nature of the corrosion products have any significant effect on the response of corroded steel reinforcement? The results obtained in indicated that the effectiveness of preventive methods is much more closely related to the degree of existing corrosion than to the nature of the corrosion products.