• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.457-460
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• 2006

Recently ultra high strength concrete is actively being developed and studied, and this trend is explained with the following effects. Technological effects expected from the application of ultra high strength concrete include the reduction of section, the decrease of structure mass and the improvement of workability. Belite cement has properities like low heat of hydration, excellent long term strength, and durablity without admixture. so, Belite cement is suitable for mass structure which is needed high strenghth, high fluidity and heat property. The objective of this study is to examine the suitability of mixture ratio through experiment of basic physical properties and provide materials for the field application of ultra high strength concrete.

• Computers and Concrete
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• v.6 no.6
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• pp.437-450
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• 2009

The effect of six different curing conditions on compressive strength and ultrasonic pulse velocity (UPV) of volcanic pumice concrete (VPC) and normal concrete (NC) has been studied. The curing conditions include water, air, low temperature ($4^{\circ}C$) and different elevated temperatures of up to $110^{\circ}C$. The curing age varies from 3 days to 91 days. The development in the pulse velocity and the compressive strength is found to be higher in full water curing than the other curing conditions. The reduction of pulse velocity and compressive strength is more in high temperature curing conditions and also more in VPC compared to NC. Curing conditions affect the relationship between pulse velocity and compressive strength of both VPC and NC.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.671-674
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• 2005

In this study, it is examined the properties of early strength of concrete mixed with polycarboxylate superplasticizer. For this experiment, it is analyzed that the slump and strength properties according to the mixture factors, compared with cements and superplasticizers of each company and curing temperature($15,\;20^{\circ}C$). (1) The slump loss of concrete used polycarboxylate superplasticizer(rapid strength type) showed $0.5\~1.5cm$, it is judged that slump loss according to the time lapse can be minimized. (2) The performance of polycarboxylate superplasticizer kept up consistency and accelerated strength development. it is possible to reveal 12MPa within $18\~20$hours at $20^{\circ}C$ curing, but impossible within 24hours at $15^{\circ}C$. (3) It is necessary to studies about rapid strength development in the low temperature.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.05a
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• pp.135-136
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• 2023

In this study, a concrete was prepared using an alkaline aqueous solution produced by electrolyzing potassium carbonate in order to improve the low initial strength of concrete using blast furnace slag. In order to confirm the increase in initial strength, the compressive strength of specimens was measured on the age of 7, 28 days. As a result, the blast furnace slag concrete using the electrolysis alkaline aqueous solution as the mixed water show high strength more than the blast furnace slag concrete using the general mixed water.

• Magazine of the Korea Concrete Institute
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• v.8 no.5
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• pp.189-200
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• 1996

The permeability of concrete influences the durability of concrete remarkably. The conventional test method for permeability is very difficult to apply to high strength concrete because of its very low permeability. The present study employs a resonable and realistic test method for permeability of concrete and proposes a very low permeability concrete. To this end, comprehensive tests have been conducted and major test variables include the types and amount of cement. the types and amount of admixtures, and the size of aggregates. The present test results indicate t h a t the permeability decrease with the increase of strength and that the concrete with certain mineral admixtures exhibits very low permeability. The permeability of those high performance concrete is about 1/100 of conventional normal concrete. The present study provides a firm base for the use of very low permeable and hence very durable concrete.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.7
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• pp.113-119
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• 2019

Concrete structures built on reclaimed land are combined with chemical erosion such as chlorine and sulfate ions from seawater. Chloride attack deteriorates the performance of the structure by corroding reinforcing bars. In addition, the waste water treatment structure has a problem that the concrete is deteriorated by the sulfate generated inside. Therefore, in this study, the characteristics and chemical resistance of low heat cement concrete used in wastewater treatment structures constructed on reclaimed land were evaluated. As a result of the experiment, the target slump and air content were satisfied under all the mixing conditions. The slump of low heat cement (LHC) concrete was higher than that of ordinary portland cement (OPC) concrete, while the air content of LHC concrete was smaller than that of OPC concrete with the same mix proportion. As a result of compressive strength test, OPC concrete showed higher strength at younger age compared to 28 days. In contrast, LHC concrete exhibited higher strength than OPC concrete at the age of 56 days. As a result of chlorine ion penetration tests, LHC-B concrete showed chlorine ion penetration resistance performance of the "very low" level at the age of 56 days. As a result of chemical resistance evaluation, when the LHC concrete is applied without epoxy treatment, chemical resistance is improved by about 18% compared to OPC concrete. In testing chemical resistance, the epoxy coated concrete exhibited less than 5% strength reduction when compared to sound concrete.

• Journal of Ocean Engineering and Technology
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• v.25 no.1
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• pp.73-79
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• 2011

The various properties of concrete have been required, as civil engineering structures are getting larger and complicated. Therefore, the high performance of concrete, such as high strength, high fluidity, and low hydration heat, has been investigated largely. In this study, the properties of lightweight concrete-reducing self-weight of structure member have been studied in order to check the applicability of lightweight aggregate concrete to structural material. The experiments on compressive strength, splitting tensile strength, unit weight, and modulus of elasticity have been conducted with varying PLC, LWCI, LWCII, LWCII-SF5, LWCII-SF15 to check the basic properties. The compressive strength of 21MPa was obtained easily by using lightweight aggregate concrete and the addition of silica fume to increase the compressive strength slightly. To use lightweight aggregate concrete for civil engineering structures, systematic and rigorous studies are necessary.

• Computers and Concrete
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• v.20 no.1
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• pp.31-38
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• 2017

In the present study an Artificial Neural Network (ANN) was used to predict the compressive strength of self-compacting concrete. The data developed experimentally for self-compacting concrete and the data sets of a total of 99 concrete samples were used in this work. ANN's are considered as nonlinear statistical data modeling tools where complex relationships between inputs and outputs are modeled or patterns are found. In the present ANN model, eight input parameters are used to predict the compressive strength of self-compacting of concrete. These include varying amounts of cement, coarse aggregate, fine aggregate, fly ash, fiber, water, super plasticizer (SP), viscosity modifying admixture (VMA) while the single output parameter is the compressive strength of concrete. The importance of different input parameters for predicting the strengths at various ages using neural network was discussed in the study. There is a perfect correlation between the experimental and prediction of the compressive strength of SCC based on ANN with very low root mean square errors. Also, the efficiency of ANN model is better compared to the multivariable regression analysis (MRA). Hence it can be concluded that the ANN model has more potential compared to MRA model in developing an optimum mix proportion for predicting the compressive strength of concrete without much loss of material and time.

• Steel and Composite Structures
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• v.39 no.3
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• pp.307-318
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• 2021

Utilizing fibers is an effective way to avoid the brittle behavior of the conventional concrete and can enhance its ductility. In particular, propylene fibers can improve concrete properties, including energy absorption, physical and mechanical properties, controlling shrinkage cracks. The increase of fiber density leads to an increase of the overlapping surface of the fiber of concrete and, in turn, a decrease of cracks developed in the concrete. However, the workability of fiber reinforced concrete tends to be lower than the conventional concrete owing mainly to the hairline thickness and excessive concentration of fibers. The low slump of concrete impedes the construction of reinforced concrete members. In this research, we study if the utilization of magnetic water can alleviate the workability issue of young fiber reinforced concrete. To this end, the compressive and flexural strength of four types of concrete (conventional concrete, fiber reinforced concrete, magnetic concrete, magnetic fiber-reinforced concrete) is studied and compared at three different ages of 7, 14, and 28 days. In order to study the influence of the fiber density and length, a study on specimens with three different fiber density (1, 2, 5 kg of fiber in each cubic meter of concrete) and fiber length (6, 12, 18 mm) is undertaken. The result shows the magnetic fiber concrete can result in an increase of the flexural and compressive strength of concrete at higher ages.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.15-18
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• 2003

Development of the construction industry generally exhausts natural aggregate. Hence it is problem to the lack of supply and quality deterioration, so the resource saving and protection of environment is made an effort through recycling by-product. This study presents that fundamental properties of concrete which used cooper slag as alternate sand of low fineness modulus and plan of cooper slag as concrete aggregate. Testing factors are concrete's slump, air contents, unit weight and compressive strength. The results of this study are as follows; (1) Concrete slump is generally satisfied with the condition but is inferior to the others in substitution rates 30%. Also air contents are 3.1-4.1% and go up according to increase substitution rate. (2) Unit weight increase in 1.1% as the mixing ratio of cooper slag argument 10%. (3) compressive strength of cooper slag concrete is similar to plain and especially higher 11-15% in W/C 45%, 50%. So it seems that aggregate mixed cooper slag is suitable to low water-cement ratio mixture.