• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.359-362
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• 2005

This study was performed to know the properties and estimation of field application of concrete(Bluecon) using fluosilicate salt based admixture made from by-product during phosphoric acid manufacturing process. Mix proportions for experiment were modulated at 0.45 of water-binder ratio and $0.5-2.0\%$ of adding ratio of fluosilicate salt based inorganic compound. Evaluation for Field application of concrete was carried out batch plant test at remicon factory and building construction. According to results. it was found that slump of concrete(Bluecon) using fluosilicate salt based admixture is higher about 10 to 20 mm than plain concrete, and air content is similar to each other. And the water permeability and crack of bluecon is lower than that of plain concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.13-16
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• 2006

This paper investigates the shrinkage behavior of Ultra High Strength(UHSC) having three water-to-cementitious material ratio, 0.20, 0.16, 0.12. All of mixtures have same design compressive strength. Free shrinkage test for autogenous and drying shrinkage using $100{\times}100{\times}400$ prismatic specimen was conducted. On all mixture, Effects of fly ash and blast-furnace slag on each shrinkage test results were also investigated. The largest portion of autogenous shrinkage was observed in UHSC12 (w/b=0.12) and the measured strain was as high as 80% of the total drying shrinkage strain. The autogenous shrinkage of UHSC decreased as the amount of fly ash increased as demonstrated in the literature. However, the results of the effect of blast-furnace slag on autogenous shrinkage were somewhat different from previous researches.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2010.05a
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• pp.229-230
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• 2010

The Carbonation, one of the main deterioration factors of concrete, reduces capacity of members with providing rebar corrosion environment. Consequently it suggested standards of all countries of world, carbonation depth prediction equation of respective researchers and time to rebar corrosion initiation. As a result of carbonation depth prediction equation calculation, difference of time to rebar corrosion initiation is 149 years and difference of carbonation depth prediction equation is 162 years when water cement ratio is 50%. So a study on rebar corrosion with carbonation depth will need existing reliable data and verifications by experiment.

• Journal of the Korean Recycled Construction Resources Institute
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• v.3 no.1
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• pp.64-71
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• 2015

Silica fume is generally adopted as admixture for Ultra High Strength Concrete (UHSC) owing to its remarkable contribution to the strength and durability but increases significantly the fabrication cost of UHSC. Accordingly, this study investigates the replacement of silica fume by blast furnace slag (BS) and fly ash (FA) in order to lower the fabrication cost of 80MPa-UHSC. To that goal, experiment is conducted on the mix proportions of mortar in terms of its binder combination, water-to-binder ratio (W/B) and unit binder content. Based on the experimental data, a mix design of concrete is derived and its properties are verified. The results reveal that a W/B of 21% and unit binder content of $720kg/m^3$ are appropriate to achieve 80MPa-UHSC using a binder composed of 60% of OPC, 30% of BS and 10% of FA. The properties of the corresponding UHSC are seen to be satisfactory with a slump flow of 715mm and compressive strength of 97MPa at 28days. The application of the binder combination derived in this study is analyzed to reduce the cost by 50% of binder compared to the mix using silica fume while realizing equivalent performance.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.04a
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• pp.259-264
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• 1999

The aim of this study of to compare the development of compressive strength of high-strength concrete with maturity and investigate the applicability the strength prediction models. An experiment was attempted on the high-strength concrete mixes using portland cement replaced by silica fume of 10% by weight of cement, the water-binder ratios of mixes being 0.30 and 0.35, the curing temperatures being 30, 20, 10, 5$^{\circ}C$. Test results of mixes are statistically analyzed to infer the correlation coefficient between the maturity and the compressive strength of high-strength concrete. The constant of strength prediction equation were determined from test results, and the equation was adopted to predict the strength of slab(W80$\times$D100$\times$H20cm). The slab was cast in the laboratory from the same batch water-binder ratio of 0.30, and cores were cut from slab in order to estimate the actual strength. These values are used to compare with predicted value. The present study allows more realistic determination of early age compressive strength of high-strength concrete and can be efficiently used to control the quality in actual construction.

• Journal of Korean Society on Water Environment
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• v.25 no.4
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• pp.515-521
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• 2009

In this study, the applicability of $CaCO_3$ as a seed material for crystallization reaction was tested. $CaCO_3$ was ground to lesser than 425 mesh and was made to media mixed with binder. Batch experiment was to investigate the ${PO_4}^{3-}-P$ removal efficiency of different parameters such as $CaCO_3$ dosage and binder ratio, size, type and mass of media. In addition, the effect of phosphorus removal from wastewater was tested using a lab-scaled crystallization reactor. At the results of the batch test, phosphorus removals were improved with increasing $CaCO_3$ dosage and media mass but were decreased with increasing media size. Moreover, phosphorus removals were influenced by specific surface area but media type. The average T-P and ${PO_4}^{3-}-P$ removal efficiency in a lab-scaled crystallization reactor with $CaCO_3$ media for wastewater were shown to be 60.2% and 60.3% for 18 days of operation time.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.577-580
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• 2006

This paper presents the experimental results of frost durability characteristics including freezing-thawing and de-icing salt scaling of the concrete used for gutter of the road. Mixtures were proportioned with the three level of water-binder ratio (W/B), 0.58, 0.53, and 0.48, and two binder compositions corresponding to Type I cement without any supplementary cementitious materials (OPC) and Type I cement with 30% blast-furnace slag replacement (Slag30). Also, two different solutions of calcium chloride and water that contains 0 and 8g of anhydrous calcium chloride in each 100 mL of solution, respectively, were used to evaluate their effect on the frost durability resistance. Test results showed that the Slag30 mixture exhibited higher durability factor and lower mass loss values than those made with OPC. Among the mixture tested in this work, the mixtures (OPC and Slag30) made with a relatively higher W/B of 0.58 exhibited large amount of the de-icing salt scaling regardless of calcium chloride concentration. Finally, the use of slag can be used effectively in terms of economy and frost durability of the concrete designated for gutter.

• Journal of Industrial Technology
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• v.41 no.1
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• pp.1-6
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• 2021

Fly ash and silica fume belong to industry by-products that can be used to produce concrete. This study shows the model of a neural network to evaluate the strength development of blended concrete containing fly ash and silica fume. The neural network model has four input parameters, such as fly ash replacement content, silica fume replacement content, water/binder ratio, and ages. Strength is the output variable of neural network. Based on the backpropagation algorithm, the values of elements in the hidden layer of neural network are determined. The number of neurons in the hidden layer is confirmed based on trial calculations. We find (1) neural network can give a reasonable evaluation of the strength development of composite concrete. Neural network can reflect the improvement of strength due to silica fume additions and can consider the reductions of strength as water/binder increases. (2) When the number of neurons in the hidden layer is five, the prediction results show more accuracy than four neurons in the hidden layer. Moreover, five neurons in the hidden layer can reproduce the strength crossover between fly ash concrete and plain concrete. Summarily, the neural network-based model is valuable for design sustainable composite concrete containing silica fume and fly ash.

• Computers and Concrete
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• v.32 no.2
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• pp.185-206
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• 2023

This article aimed to explore the optimization of mineral admixtures and retarding admixture for high-performance concrete. In essence, fresh concrete can be regarded as a mixture in which both coarse and fine aggregates are suspended in a cement-based matrix paste. Based on this view, the test procedure was divided into three progressive stages of binder paste, mortar, and concrete to explore their rheological behavior and mechanical properties respectively. At each stage, there were four experimental control factors, and each factor had three levels. In order to reduce the workload of the experiment, the Taguchi method with an L9(3⁴) orthogonal array and four controllable three-level factors was adopted. The test results show that the use of the Taguchi method effectively optimized the composition of high-performance concrete. The slump of the prepared concrete was above 18 cm, and the slump flow was above 50 cm, indicating that it had good workability. On the other hand, the 28-day compressive strength of the hardened concretes was between 31.3-59.8 MPa. Furthermore, the analysis of variance (ANOVA) results showed that the most significant factor affecting the initial setting time of the fresh concretes was the retarder dosage, and its contribution percentage was 62.66%. On the other hand, the ANOVA results show that the most significant factor affecting the 28-day compressive strength of the hardened concretes was the water to binder ratio, and its contribution percentage was 79.05%.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10a
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• pp.433-438
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• 2000

The purpose of this study is to examine the resistance of water-permeable concretes to freezing and thawing action. The water-permeable concretes with cement-aggregate ratio of 1:5.5(by weight) and two kinds of admixture content [SP : superplasticizer(0, 1.0%), HPAE : high performance air entraining agent(0.5, 1%)] used OPC(ordinary portland cement) as binder were prepared, and then tested for relative dynamic modulus of elasiticity, mass change, length change and durablity factor. It's been concluded from the test results that the superior relative dynamic modulus of elasiticity and durability factor of water-permeable concretes were obtained at superplaciticizer 1.0% after 300 cycles. The water-permeable concretes used superplasiticizer 1.0% having relative durability factor of 88% after 300 cycles.