• Computers and Concrete
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• v.31 no.4
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• pp.315-325
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• 2023

Calcium leaching is one of the main deterioration factors in concrete structures contact with water, such as dams, water treatment structures, and radioactive waste structures. It causes a porous microstructure and may be coupled with various harmful factors resulting in mechanical degradation of concrete. Several numerical modeling studies focused on the calcium leaching depth prediction. However, these required a lot of cost and time for many experiments and analyses. This study presents an artificial neural network (ANN) approach to predict the leaching depth quickly and accurately. Totally 132 experimental data are collected for model training and validation. An optimal ANN model was proposed by ANN topology. Results indicate that the model can be applied to estimate the calcium leaching depth, showing the determination coefficient of 0.91. It might be used as a simulation tool for engineering problems focused on durability.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.2
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• pp.74-80
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• 2011

In this study, it is evaluated on the properties of mechanical performance, autogenous shrinkage and chloride resistance for application of high performance concrete for bridge deck overlay used slag powder and fly ash as a representative by-product of industrialization. According to test results, it is evaluated that the durability of concrete is improved the properties of chloride resistance, autogenous shrinkage and alkali aggregate reaction by using hydraulic mineral admixtures. It is considered to have a green construction and an economic feasibility on recycling of by-product as a improved concrete for durability and efficiency in materials and constructions.

• Earthquakes and Structures
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• v.7 no.2
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• pp.179-199
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• 2014

The steel tube-reinforced concrete (ST-RC) composite column is a novel type of composite column, consisting of a steel tube embedded in reinforced concrete. The objective of this paper is to investigate the effect of cumulative damage on the seismic behavior of ST-RC columns through experimental testing. Six large-scale ST-RC column specimens were subjected to high axial forces and cyclic lateral loading. The specimens included two groups, where Group I had a higher amount of transverse reinforcement than Group II. The test results indicate that all specimens failed in a flexural mode, characterized by buckling and yielding of longitudinal rebars, failure of transverse rebars, compressive crushing of concrete, and steel tube buckling at the base of the columns. The number of loading cycles was found to have minimal effect on the strength capacity of the specimens. The number of loading cycles had limited effect on the deformation capacity for the Group I specimens, while an obvious effect on the deformation capacity for the Group II specimens was observed. The Group I specimen showed significantly larger deformation and energy dissipation capacities than the corresponding Group II specimen, for the case where the lateral cyclic loads were repeated ten cycles at each drift level. The ultimate displacement of the Group I specimen was 25% larger than that of the Group II counterpart, and the cumulative energy dissipated by the former was 2.8 times that of the latter. Based on the test results, recommendations are made for the amount of transverse reinforcement required in seismic design of ST-RC columns for ensuring adequate deformation capacity.

• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.2
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• pp.173-180
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• 2005

Metakaolin is a cementitious material for producing high-strength concrete. This material is now used as substitute for silica-fume. In this paper, we did the mechanical and durability test such as compressive/tensile/flexural strength test, chloride ion diffusion, chemical attack and repeated freezing and thawing, carbonation test. In the mechanical tests, 10~15% for binder is optimum substitute rate. And, in the chloride ion diffusion test, according to the increase of substitute of metakaolin & silica-fume for binder, the diffusion coefficient was more reduced. In the chemical attack test, by the filler effect of fine powder such metakaolin and silica-fume, the resistance is more excellent than normal concrete. In the other durability test, the concrete using metakaolin also compared with those of silica-fume substitute concrete. Through these tests, we recognized that metakaolin can be used as a substitute for silica-fume.

• KIEAE Journal
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• v.11 no.4
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• pp.87-94
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• 2011

This study was suggested to develop sustainable durability design system and proposed the plan to evaluate design conditions that meet the intended service life and $LCCO_{2}$ reduction level of reinforced concrete structure easily from the early design stage. For that the W/B and covering depth of the concrete structure were calculated through calculation of service life based on standard specification expression and the quantitative reduction rate of the vertical member of reinforced concrete structure by the calculated W/B was applied. Life cycle of building classified into construction stage, operation stage, maintenance stage, and demolition/disposal stage and the method of $CO_{2}$ evaluation of each stage was proposed. For construction stage, the major construction materials that take up over 80% $CO_{2}$ emitting during building construction were selected and the $CO_{2}$ evaluation method for 5 standard apartment houses was proposed. Also, for operation stage, $CO_{2}$ emission was calculated through calculation of heating load by energy efficiency rating certification system. For maintenance stage, $CO_{2}$ emission was calculated using concept of re-construction by life and for demolition/disposal stage was calculated with the use of construction standard estimate. As a result of the case study by such evaluation methods, 80 years of service life and 17 specifications of sustainable durability design that meet the 40% intended $LCCO_{2}$ reduction level were deduced. The Maximum $LCCO_{2}$ reduction rate was analyzed by 47.2%.

• Computers and Concrete
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• v.19 no.5
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• pp.489-499
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• 2017

Self-Compacting Concrete (SCC) is a new technology capable to flow without segregation or any addition of energy which leads to efficient construction and cost savings. In this study, the effect of replacing the Ordinary Portland Cement (OPC) with Fly Ash (FA) on the strength, durability of the concrete was investigated experimentally, and carbon footprint and cost were also assessed. Four different replacement FA ratios (0%, 20%, 40% and 60%) were used to create four SCC mixes. Standard test methods were used to determine the workability, strength, and durability of the SCC mixes including resist chloride ion penetration, water permeability, water absorption, and initial surface absorption. The axial cube compressive strength tests were performed on the SCC mixes at 1, 7, 14, 28 and 35 days. Replacing the OPC with FA had a significant positive impact on chloride iron penetration resistance and water absorption but had a considerable negative impact on the compressive strength. The SCC mix with 60% FA had 36.7% and 15.8% enhancement in the resistance to chloride ion penetration and water absorption, respectively. Evaluation of the carbon footprint and the cost of each SCC mixes showed the $CO_2$ emissions mixes 1, 2, 3 and 4 were significantly reduced by increasing the FA content from 0% to 60%. Compared with the control mix, the cost of all mixes increased when the FA content increased, but no significant differences were seen between the estimated costs of all four mixes.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.5
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• pp.59-67
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• 2012

During the manufacturing of Portland cement, CO2 gas is also necessarily produced through both decarbonation of calcium carbonate and kiln burning. By partially replacing the Portland cement with limestone powder, which is an inert filler in a concrete mixture, CO2 consumption can be reduced in a construction field. This study is to investigate the fundamental durability characteristics of limestone powder added concrete. Experimental variable was the replacement ratio of limestone powder from 0% to 25% with 5% increment. Durability characteristics were investigated by resistance to freeze-thaw, alkali-silica reaction and de-icing chemical in addition to the properties of fresh concrete. From test results, it was observed that the addition of limestone powder did not significantly affect the resistance to freeze-thaw reaction and de-icing chemical. The addition of limestone powder reduced the occurrence potential of alkali-silica reaction by reducing an alkali content in Portland cement.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.497-500
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• 2008

In order to prevent deterioration of reinforced concrete structures exposed to marine environment, performance based durability design than the design by conventional deemed-to-satisfy rule should be concerned. For example, even though chloride threshold level, which is a major parameter for durability design, is defined as a 1.2 $kg/m^3$ in the Korean concrete specification, it shows that the chloride threshold level leads to over design in its real application so that realistic value should be determined for the performance design. In this paper, not only the probabilistic properties of chloride threshold level obtained from published data are taken into account, but also the experimental results of the probabilistic properties using surface chloride content, diffusion coefficient, cover depth are considered in the assessment utilizing the concept of performance based durability design. In computation, the Monte Carlo Simulation (MCS) is used to perform an assessment due to chloride attack for a target submerged tunnel box. This study found that the specification on current chloride threshold level should be modified for more rational and accurate assessment and design.

• Advances in concrete construction
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• v.14 no.3
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• pp.185-194
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• 2022

For producing cement and concrete, the construction field has been encouraged by the usage of industrial soil waste (or) secondary materials since it decreases the utilization of natural resources. Simultaneously, for ensuring the quality, the analyses of the strength along with durability properties of that sort of cement and concrete are required. The prediction of strength along with other properties of High-Performance Concrete (HPC) by optimization and machine learning algorithms are focused by already available research methods. However, an error and accuracy issue are possessed. Therefore, the Enhanced Deep Neural Network (EDNN) based strength along with durability prediction of HPC was utilized by this research method. Initially, the data is gathered in the proposed work. Then, the data's pre-processing is done by the elimination of missing data along with normalization. Next, from the pre-processed data, the features are extracted. Hence, the data input to the EDNN algorithm which predicts the strength along with durability properties of the specific mixing input designs. Using the Switched Multi-Objective Jellyfish Optimization (SMOJO) algorithm, the weight value is initialized in the EDNN. The Gaussian radial function is utilized as the activation function. The proposed EDNN's performance is examined with the already available algorithms in the experimental analysis. Based on the RMSE, MAE, MAPE, and R² metrics, the performance of the proposed EDNN is compared to the existing DNN, CNN, ANN, and SVM methods. Further, according to the metrices, the proposed EDNN performs better. Moreover, the effectiveness of proposed EDNN is examined based on the accuracy, precision, recall, and F-Measure metrics. With the already-existing algorithms i.e., JO, GWO, PSO, and GA, the fitness for the proposed SMOJO algorithm is also examined. The proposed SMOJO algorithm achieves a higher fitness value than the already available algorithm.

• Journal of the Korea Institute of Building Construction
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• v.23 no.3
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• pp.285-293
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• 2023

In this research, we embarked on a meticulous analysis of the challenges inherent in real-world scenarios relating to the durability design standards of engineered concrete structures and the assessment of carbonation durability in concrete guidelines. Our investigation brought to light substantial issues concerning constructability and quality assurance. The genesis of these problems is the exclusive application of prescribed strength to exterior walls, neglecting other elements to facilitate smoother licensing procedures. While this methodology aims to mitigate financial constraints in alignment with enhanced standards, it invariably invites complications. Furthermore, it is imperative to resolve the uncertainty surrounding durability evaluations by establishing a clear and definitive objective. Alongside this, actionable steps must be formulated to forestall the emergence of fissures between the floors of residential buildings, particularly apartment complexes. It is equally essential to tackle issues connected to application by devising a comprehensive management strategy for potential cracking during the phase of maintenance.