• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.5
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• pp.106-114
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• 2006

This paper investigates the fundamental properties and shrinkage characteristics of low shrinkage high performance concrete(LSHPC), using mock-up specimens. According to the test results, the most suitable mix proportions of LSHPC need a higher dosage of SP agent and AE agent, in order to obtain the target of slump flow and air content. This is due to reduce fluidity and air content respectively. It also presented earlier setting time than control concrete by 6 hours and exhibited compressive strength of 60MPa at age 28 days. Autogenous shrinkage of LSHPC was the half of the value of control concrete. Drying shrinkage of center section of LSHPC showed similar tendency with autogenous shrinkage, because of no internal moisture movement, while surface section had larger drying shrinkage. The specimen with embedded reinforcing bar had smaller deformation owing to confinement of reinforcing bar.

• KIEAE Journal
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• v.10 no.3
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• pp.89-96
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• 2010

In comparison with ordinary or heavy-weight concrete, light-weight air void concrete has the good aspects in optimizing super tall structure systems for the process of design considering wind load and seismic load by lightening total dead load of buildings and reducing natural resources used. Light-weight air void concrete has excellent properties of heat and sound insulating due to its high amount porosity of air voids. So, it has been used as partition walls and the floor of Ondol which is the traditional Korean floor heating system. Under the condition of which the supply of light-weight aggregates are limited, the development of light-weight concrete using air voids is highly required in the aspects of reduced manufacturing prices and mass production. In this study, we investigated the physical properties and thermal behaviors of specimens that applied different mixing ratios of foaming agent to evaluate the possibility of use in the structural elements. We proposed the estimating equation for compressive strength of each mix having different ratio of foaming agent. We also confirmed that the density of cement matrix is decreased as the mixing amount of foaming agent increase up to 0.6% of foaming agent mixing ratio which was observed by SEM. Based on porosity and compressive strength of control mortar without foaming agent, we built the estimating equations of compressive strength for mortars with foaming agent. The upper limit of use in foaming agent is about 0.6% of the binder amount. Each air void is independent, and size of voids range from 50 to $100{\mu}m$.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.321-324
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• 2008

Recently increasing interest in high-rise building around the world for more than 100 floor, the trend is the increasing use of high-strength and high-flowable concrete so as of productivity improvements and cost savings to improve the performance of the early strength development. This study is to reach the optimal combination by reviewing the performance of high-rise building which is required. The results show that $30.0{\sim}32.5%$ of W/B, $155㎏/m^3$ of unit water and FA10+SP10 is best properties for early strength of concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.673-676
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• 2008

Color concrete utilizes peculiar texture and color sense in external appearance actively as a finish. But, this color concrete is essential use of pigment for required color revelation, and color cone cleat from mixing of this pigment are different existent achromatic color concrete and basic properties of matter. this study progressed slump test and setting time examination through mortar injection resistance examination of mortar that mix Pigment.

• Journal of the Korea Institute of Building Construction
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• v.16 no.6
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• pp.561-569
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• 2016

Concrete is cheap, easy to deal with, and the quality is satisfactory. Also, it is one of the easiest materials to get because chemical composition of cement is similar to chemical composition of surface. On the other hand, it is so vulnerable to transform because of weak binding capacity and low binding energy that it produces cracks. Cracks decline durability, usability, safety of structures and damage exterior. In order to decline drying shrinkage crack, this study used shrinkage reducing typed Superplasticizer, which is combination of and water-reducing agent for convenience, different with existing study using AE agent, water-reducing agent, shrinkage reducing agent,. Considering SRS field application possibility, this study planned to mix concrete and mortar generally used in ready-mixed concrete company and did basic experiment depending on a change of SRS content ratio and admixture. Based on the experiment result. It is judged that SRS admixture 2% is proper ratio when Given the intensity and length change. Also mass combination will conduct follow-up studies.

• Journal of the Korea Concrete Institute
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• v.20 no.6
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• pp.773-784
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• 2008

Even if the exploitation of copper slag produced during the smelting process of copper as aggregate for construction purpose has been permitted since 2004 in Korea, the lack of sufficient data enabling to evaluate its long-term stability that is its durability has to date impeded its application. This study intends to investigate experimentally the durability characteristics of 18 and 27 MPa-class commercial concretes in which natural sand (fine aggregates) has been partially replaced by copper slag through accelerated and exposure tests so as to provide bases promoting the application of copper slag concrete. The experimental results revealed insignificant difference of the durability characteristics in most of the mix proportions in which 30% of natural sand was replaced by copper slag. In the case where crushed sand was adopted, tests verified similar characteristics for replacement ratio of 50%. Particularly, the results of the exposure test conducted during 8 years demonstrated that equivalent level of durability was secured compared to the case using natural sand. In the case of 18MPa-class lower grade concrete, exposure test verified also that the physical lifetime similar to 50 years could be secured until carbonation reaches cover depth of 20 mm.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.1
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• pp.109-119
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• 2015

In recent years, a rapid growth in the population and urbanization led to an increasing industrial growth. The inadequate treated-wasted water from industry and various non-point sources causes significant negative effects on the stream water. For past few decades, extensive researches have been performed on water purification process. The purpose of this study is to investigate mechanical performance and water purification properties of porous concrete by using effective microorganisms through the site assessment test. The mechanical performance evaluation results showed that the increase void ration caused an decrease in the strength. The optimal mix rate was found to be 15% void rate From the site assessment, it was evaluated that the porous concrete improved the quality of the water and the purification ratios are 34.1 for SS, 14.6% for BOD, 34.9% for COD, 11.4% for T-N, and 12.6% for T-P. The porous concrete and the related purification technique can reduce the non-point pollution sources flowing into the river.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.4
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• pp.110-115
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• 2017

This research was performed to investigate the mechanical performance of lightweight concrete including phase changing material(Low temperature PCM). Micro capsulised PCM consisted of wax type core and melamine based wall. Also, for PCM of one single kind, paraffin wax was inserted into Vermiculite and the surface was coated with melamine resin. Interfacial polymerization is based on the principle that macromolecule reaction takes place on the surfaces between 1-dodecanol(core material) and water (solvent) to form the wall material. Lightweight concrete has compressive strength of 10 MPa, tensile strength of 1.5 MPa, and oven dried density of 1.0kg/liter which included 10%, 20%, or 30% PCM by weight. To do so, this study fabricated light-weight foamed concrete ($1.0kg/m^3$) in pre-foaming method and mixed it with PCM micro capsule of 1-dodecanol and melamine to examine its physical properties.

• International Journal of Highway Engineering
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• v.15 no.4
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• pp.65-73
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• 2013

PURPOSES : As a research to develop a cement treated base course for an airport pavement which can enhance its drainage, this paper investigated the strength, infiltration performance and durability of the pervious concrete with respect to maximum coarse aggregate sizes and compaction methods. METHODS : This study measured compressive strength, infiltration rate, continuous porosity and freeze-thaw resistance of pervious concrete specimens, which were fabricated with five different compaction methods and different maximum aggregate sizes. In addition, in order to reduce the usage of Portland cement content and to enhance environment-friendliness, a portion of the cement was replaced with Ground Granulated Blast Furnace Slag (GGBS). RESULTS: Compressive strength requirement, 5 MPa at 7 days, was met for all applied compaction methods and aggregate sizes, except for the case of self-compaction. Infiltration rate became increased as the size of aggregate increased. The measured continuous porosities varied with the different compaction methods but the variation was not significant. When GGBS was incorporated, the strength requirement was successfully satisfied and the resistance to freezing-thawing was also superior to the required limit. CONCLUSIONS: The infiltration rate increased as the maximum size of aggregate increased but considering construct ability and supply of course aggregate, its size is recommended to be 25mm. With the suggested mix proportions, the developed pervious concrete is expected to successfully meet requirements for strength, drainage and durability for cement treated base or subbase course of an airport pavement.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.1005-1008
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• 2008

The purpose of this study is to estimate basic mechanical properties of alkali-activated concretes based on GGBS(Ground Granulated Blast Furnace Slag). In this study, various mix ratios of alkali activated concretes based on sodium silicate and GGBS were set to evaluate concrete's compressive strengths and strains on the basis of results of existing alkali-activated cements and preliminary concrete tests, which were already performed by authors [Ref. 1]. Compressive strengths of concretes of ages 1, 3, 7, 28, 56 and 91 days were tested and investigated, respectively, and at early ages (< 7days) alkali-activated slag concrete (AASC) showed a high strength development, compared to that of Ordinary Portland Cement (OPC). A compressive strengths of AASC at age-3days range between 18 and 24 MPa, while those of OPC range 12 and 15 MPa. The stress-strain curve after maximum stress, on the other hand, is approximately reached at a compressive strain between 0.002 and 0.0025, which mechanical property is very similar to that of OPC.