• Proceedings of the Korea Concrete Institute Conference
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• 1998.10a
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• pp.501-506
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• 1998

This paper is an experimental study on the flexural strength and ductility capacity of reinforced high performance concrete beams with the concrete which has compressive strength of 600~700kg/$\textrm{cm}^2$, slump value of 20~25cm and slump-flow value of 60~70cm. Total 8 beams with different tensile reinforcement ratio and pattern of loading were tested. Form the results of reinforced high performance concrete beams, the equivalent stress block parameters proposed by MacGregor et al. or New Zealand code are recommended to use. Also, an extreme fiber concrete compressive strain of reinforced high performance concrete beams are distributed 0.0033~0.0048. In reinforced high performance concrete beams, reinforcement ratio in order to insure curvature ductility index 2 and 4 propose by ACI code should be less than those of reinforced normal strength concrete beams.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2002.11a
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• pp.77-86
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• 2002

In this study we intended to investigate properties of cement mortar with recycled PET fiber, PE fiber, and PP fiber such as slump flow, compressive strength, tensile strength, and flexural strength. As results of experiment, several properties of specimen with recycled PET fiber were little low comparing those of specimen with PE fiber and PP fiber. But if we see from point of economy and recycle of industrial wastes, it has enough reason to be used. Compressive strength of specimen with recycled PET fiber at 56 days was about 10% higher, but tensile strength and flexural strength were lower than that of no-fiber.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.3
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• pp.21-27
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• 1997

This paper aims to clarify the effects of grinding conditions in form grinding of Sr-ferrite with the electro-plated diamond wheel. The main conclusions obtained were as follows. (1) The flexural strength and surface roughness of ferrite became the best at the peripheral wheel speed of 1700 m/min. (2) In the case of the depth of cut larger than 0.4mm, crack layers is induced in the ground surface, and the fracture type of chips exhibits slight ductile mode in the depth of cut smaller than 0.2mm. (3) Whe the depth of cut exceeds 0.6mm, the wheel life becomes extremely severe due to the large chipping and brack- age in the diamond grains. However, at the depth of cut .leq. 0.05mm, the diamond grain shows abrasive wear. (4) The decrease of flexural strength and the increase of surface roughness is in proportion to the increase of the feed rate. (5) Most effective nozzle setting angles with various delivery conditions of the grinding fluid, such as nozzle position .PHI. , flow rate Q, etc., were made clear.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.04a
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• pp.301-307
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• 1997

This paper is evaluated for properties of aggregate and antiwashout admixture not only to minimize segregation and water contamination of underwater concrete but also to meet concrete quality required. Two antiwashout admixtures used in this study were available domestically and slump flow, pH, setting time, and filing property of fresh concrete and the compressive strength, flexural strength under water and in the air under 2 different curing conditions ($10^{\cire}C$ and $20^{\cire}C$ ) were measured. Compressive strength ratio of specimens cured in and water temperature $10^{\cire}C$ /$20^{\cire}C$ added HPEC and HPMC was 64% and 89%, respectively. Relative compressive strength of 2 kinds observed higher concrete added HPEC, 3% at $10^{\cire}C$ curing temperature, 34% at $20^{\cire}C$ . The flexural strength of specimens made under water was 1/4~1/6 of compressive strength similar to the existing data in the literature.

• Journal of the Korea Institute of Building Construction
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• v.2 no.4
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• pp.113-122
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• 2002

In this study we intended to investigate properties of cement mortar with recycled PET fiber, PE fiber. and PP fiber such as slump flow, compressive strength, tensile strength, and flexural strength. At results of experiment. several properties of specimen with recycled PET fiber were little low comparing those of specimen with PE fiber and PP fiber. But if we see from point of economy and recycle of industrial wastes, it has enough reason to be used. Compressive strength of specimen with recycled PET fiber at 55 days was about 10% higher. but tensile strength and flexural strength were lower than that of no-fiber.

• Advances in concrete construction
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• v.13 no.5
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• pp.349-360
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• 2022

The rising prices of landfills and the lack of cement production are motivating researchers to be more interested in using wastes to produce concrete mixtures materials. The use of waste materials such as eggshell and matakoline waste not only reduces landfill costs and space, but also reduces the cost of cement production for the concrete mixture. However, recycling waste materials has become critical in order to effectively manage environmental sustainability. The purpose of this paper is to investigate the appropriate properties of self-compacting concrete (SCC) by incorporating waste materials such as crushed ceramics as coarse aggregate and nano egg shell (NES) and nanoclay (NC) as cement replacements. Fresh properties of SCC, such as segregation, flow time and diameter, V-funnel, H2/H1 ratio, and fresh unit weight of concrete mixtures, as well as hardened properties, such as 7, 14, and 28 days compressive strength and 28 and 90 days flexural strength, were measured for this purpose. The presence of NC in the SCC mixture enhanced the compressive strength of the concrete when 5% of NES was added or in the case without the addition of NES compared to the control mixture. The flexural strength enhanced with the incorporation of NC in the SCC increased the flexural strength of the concrete compared to the control mixture, but the incorporation of 5% of NES decreased the flexural strength compared to the mixtures with NC. These results prove the possibility of using crushed ceramics as the coarse aggregate, and NES and NC as substitutes for 5, 7, and 10% of the cement in SCC, because the properties of such SCC in hardened and fresh states are satisfactory.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.431-436
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• 2001

Lateral confining effect due to the existence of the shear reinforcements in R.C. beam is investigate in a numerical way. For the purpose, a three dimensional constitutive model of concrete is developed based on the elasto-plasticity using non-associated plastic flow rule to control the excessive inelastic dilatancy. The plastic flow direction is determined based on the associated plastic flow direction in a way to adjust the directional angle between the two normal vector components along the hydrostatic and deviatoric axis in a meridian plane in which the loading function prescribed. The current formulation is combined with the four parameter elasto-plastic triaxial concrete model recently developed. The resulting elasto-plastic triaxial concrete model predicts the fundamental behaviors of concrete under different confining levels and the 4-points flexural test of a beam with shear reinforcements, compares with the experimental results.

• Proceedings of the Korea Concrete Institute Conference
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• 1996.04a
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• pp.65-68
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• 1996

As a fundamental study on the quality control according to the freezing of admixture agent for concrete, this study instends to investigate the variation of quality of admixture according to the freezing by analyzing flow, unit weight, and compressive, tensil, flexural strength of cement mortar using admixture agent before and after freezing.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.327-332
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• 2000

The objective of this study was to improve the defects of lightweight cement concrete by treating with redispersible polymer powders. The statistical relationships of water-cement ratios, contents of lightweight aggregates and polymer powers and be used for predicting the concrete strength. It was found that the varieties and techniques adopted in this experiment were capable of identifying the influence of various tested for air contents, flow test, water absorption, specific gravity, flexural and compressive strength. This study showed that fundamental properties were very affected by cement- lightweight aggregate ratio, polymer-cement ratio and water-cement ratio.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.11a
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• pp.215-216
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• 2023

Leakage in the structure due to the irregular flow of groundwater in the underground structure penetrates into internal spaces such as underground parking lots and basement through underground walls, which is expensive in terms of maintenance of the building. In this study, various composite waterproofing methods installed on the outer walls of underground structures were selected to evaluate the structural performance of composite specimens due to bending behavior through experiments and analysis on bending test behavior on concrete attachment surfaces.