• Cement Symposium
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• s.39
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• pp.111-119
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• 2012

• Journal of the Korea Concrete Institute
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• v.24 no.1
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• pp.37-44
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• 2012

Recently, due to developments in construction technology, the use of high-performance concrete became popular. High-performance concrete when compared to the ordinary concrete can better satisfy required performances by using mineral admixture and superplasticizer. Various studies on the effect of admixture materials on the quality of high-performance concrete have been reported. But there exist limited number of reported results on the effect of cement qualities, which is the most important constituent material in concrete. Therefore, in this study, the relationship between the quality of cement and the flowability of high flowing concrete is investigated. Qualities of domestically produced cement were identified, and then the influence of the qualities of cement on the flowability of high flowing concrete is evaluated. The result showed that the dosage of required superplasticizer was dependent on cement fineness, to brain, free-CaO, and interstitial phase, which all trigger initial hydration process of cement. Particularly, the results showed that fineness of cement has a high impact on the dosage of the superplasticizer. For strength property of concrete, the dosage of superplasticizer had a significant effect on the early age strength, but had negligible effect in the long term strength.

• Journal of Adhesion and Interface
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• v.7 no.3
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• pp.1-9
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• 2006

To improve the poor mechanical and thermal properties of conventional PMMA bone cement, we impregnated three types of polyethylenes (PE) (200, 3,800, and 8,000 kg/mol). MMA/xylene solution was used to modify the surfaces of PEs and new composite PMMA bone cements were manufactured by impregnating 3 wt% of the surface-modified PEs into conventional PMMA bone cement. As molecuar weigth of PE increased, tensile strengths of the manufactured composite PMMA bone cements were improved. Also, we confirmed that the curing temperatures of the composite PMMA bone cements decreased from near $100^{\circ}C$ to $40^{\circ}C{\sim}80^{\circ}C$.

• Journal of the Korea Concrete Institute
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• v.16 no.1 s.79
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• pp.1-9
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• 2004

This paper represents the permeability of chloride ions and the corrosion performance in the concrete blended with granulate blast furnace slag exposed to chloride environment. An ordinary cement (type I ) and sulfate resisting cement(type V) were used for the experiment. The two cements were combined with $0\%$, $25 \%$, $40\%$, and $55\%$ of the granulated blast furnace slag. The accelerated permeability tests of chloride ions were performed in accordance with ASTM C1202, and the accelerated corrosion tests of steel were carried out by using the method of immersion/drying cycles. After water curing 28 days, 56 days and 91 days, these tests were conducted until 30 cycles. In every cycle, test specimens were wetted in $3\%$ NaCl solution for three days and dried again in $60^{\circ}C$ air for four days. As an experimental results, the diffusion coefficient of chloride ions of the ordinary cement Concrete Combined granulated blast furnace slag was much lower than that of non granulated blast furnace slag concrete. Moreover, the diffusion coefficient of chloride ions of sulfate resisting cement concrete was higher than that of ordinary cement concrete. On the basis of the results of accelerated corrosion tests, corrosion resistance of the concrete mixed with granulated blast furnace slag shows good to corrosion resistance, however, the concrete with sulfate resisting cement shows bad to corrosion resistance.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.1
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• pp.102-112
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• 2019

This paper studies impact fracture behavior under temperature variation and compressive flexural strength of cement composites using VAE(vinyl acetate ethylene) powder polymer and PVA(polyvinyl alcohol) fiber. Impact test were conducted in the temperature range selected for the $-35^{\circ}C$, $0^{\circ}C$ and $35^{\circ}C$. In this experimental study, impact test were carried out using a drop impact testing machine (Ceast 9350) to obtain such as displacement, time, and impact fracture energy of normal specimen and and cement composites specimen. As test results, the use of VAE powder polymer and PVA fiber were observed to enhance the flexural strength of mortar. The compressive strength of PVA fibers reinforced cement composites was slightly decreased at 28 days, but the flexural strength was observed to increase 24.4% of normal mortar strength. As a result of the drop impact tests, PVA fiber reinforced cement composites specimens showed microcracks due to energy dispersion and crack prevention with bridge effect of the fibers, and scabbing or perforation by impact was suppressed. On the other hand, the normal mortar and VAE powder polymer cement composites specimens were carried out to the perforation and macro crack. Most of normal mortar and the cement composites subjected to impact load on specimens shows mostly local brittle failure. The impact resistant performance of the specimen with PVA fiber was greatly improved due to the increase of flexure performance.

• Journal of the Korea Concrete Institute
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• v.16 no.3 s.81
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• pp.303-310
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• 2004

The purpose of this study was to investigate the effect of using method and replacement ratio of limestone powder and water-cement ratio on the compressive strength and the resistance to sulfate attack of mortar incorporating limestone powder as fundamental study to use limestone powder as an addition for concrete. As a results, The method using limestone powder as a part of cement showed decrease of the compressive strength of mortar. The strength of mortar incorporating limestone powder almost decided upon unit cement content. It was recognized that the method replacing limestone powder as a part of cement was effective to decrease the heat of hydration in concrete. The method using limestone powder as a part of fine aggregate showed the considerable increase of the strength and resistance to sulfate attack of concrete. Furthermore, it was recognized that the method using limestone powder as a part of fine aggregate were effective materials as an addition for concrete in view of the improvement of strength and resistance to sulfate attack.

• Journal of the Korea Concrete Institute
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• v.18 no.6 s.96
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• pp.769-776
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• 2006

Recently, owing to the development of industry and the improvement of building techniques, concrete structures are becoming larger and higher. In hardening of these large connote structures, the heat of hydration gives rise to considerable thermal stress depending on the size and environmental condition of concrete, which might cause thermal cracking. Especially, the crack may cause severe damage to the safety and the durability of concrete structure. This study investigates the thermal properties of concrete according to several binder conditions, such as OPC, Belite rich cement(BRC), slag cement(SC), blast furnace slag(B) added cement fly ash(F) added cement and blast-furnace-slag and fly ash added cement. As a result of this study, the properly of concrete is most better BRC than others, and fly ash(25%) added cement and BFS(35%)-fly ash(15%) added cement gets superior effect in the control of heat hydration. But synthetically considered properties of concrete, workablity, strength heat hydration, etc, it is more effective to use mineral admixture. Especially, to be used Blast Furnace slag is more effective.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.1
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• pp.88-94
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• 2011

To make recycling aggregate, quantity of fine particles increase due to multi-crushing. Though this particles were mixed with recycling aggregate, those have to be disparted from aggregate in the high quality recycling aggregate, because of the cause of low quality. Considering reactivity, fine particles is better than coarse one. Therefore, it needs to develop suitable usage. We try to make cement extruding material by using the fine particles from concrete recycling, as a silicious replacement. Test results are as follows ; 1) Waste concrete powder has major ingredients such as $SiO_2$ and CaO, its density is $2.45g/cm^3$ being similar to silica powder, its diameter is range 13 to $141{\mu}m$. 2) Considering to strength properties according to particle size, specimen was made using small particles is higher strength than large one. 3) Despite of exception in the autoclaved curing, when the replacement of waste fine particle increase, strength of extruding panel shows almost same level.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.2
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• pp.177-184
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• 2021

In this study, the effects of ground granulated blast furnace slag(GGBFS) and expansive additive(EA) on early strength mortar were examined for the purpose of reducing carbon and improving cement performance. As a result, ealry strength Portland cement(EPC) tended to decrease in flow compared to ordinary Portland cement(OPC), but binder with EPC and GGBFS was possible to obtain higher liquidity than OPC. EPC showed higher compressive strength and shrinkage than OPC. The compressive strength of specimen with EPC and GGBFS was reduced proportionally to the replacement ratio of GGBFS. The replacement ratio of GGBFS above the compressive strength equivalent to OPC was higher under low temperature conditions. The use of GGBFS resulted in high shrinkage compared to OPC, and this characteristic was even greater under low temperature conditions. The shrinkage of specimen with EA was decreased in early ages, but was higher than the OPC in long-term ages.

• Journal of the Korean Ceramic Society
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• v.39 no.1
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• pp.99-107
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• 2002

Impedance Spectroscopy (IS) has been used to study microstructure and hydration mechanism of cement pastes. In this work, the early hydration behaviour of portland cement paste with different blame values and contents of blast-furnace slag was investigated by IS. As slag was added to portland cement, the values of $R_{t(s+1)}$ (the solid-liquid phase resistance) and $R_{t(int)}$ were decreased in the early hydration period. It showed that hydration of cement paste containing slag was slower than it of the reference cement paste. As the content of slag was increased, the values of $R_{t(s+1)}$ was decreased. Furthermore, the diameter of semicircle, $R_{t(int)}$ observed at 72 hours was decreased with the increment of slag content. However, the values of $R_{t(s+1)}$ and $R_{t(int)}$ were increased with blame value of slag from the early hydration period.