• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.687-690
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• 2005

Recently, to consider financial and constructive aspect, usage of Admixture, like Blast- Furnace Slag and Fly-Ash, are increased. These mineral admixtures, a by-product of steel industry, have many advantage, to reduce the heat of hydration, increase in ultimate strength, improve workability and etc. But it also reduces early-age strength, so it is prevented from using of Blast-Furnace Slag at cold-weather-concrete. In this study, for the purpose of increasing usage of mineral admixtures, like Blast-Furnace Slag and Fly ash, it is investigated the strength properties of concrete subjected to under low temperature According to this study, if early curing is carried out before having frost damage, the strength of concrete, subjected to frost damage, is recovered. And to consider increasing effect of strength, it is more effective to use of mineral admixtures, especially to use blast furance slag.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.707-710
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• 2005

This experimental study investigate temperature dependency affecting setting and strength development of concrete using mineral admixtures such as CKD, FA and BS. For the properties of setting at $5^{\circ}C$, setting time of concrete with mineral admixture was delayed about $3\~14$ hour compared with that of plain concrete. Use of CKD had a desirable effect on reducing setting retard under $5^{\circ}C$ because of $CaCO_3$ of CKD while use of FA and BS retarded setting time greatly. For compressive strength under $5^{\circ}C$, concrete with CKD had the most compressive strength in early age compared with the other mineral admixtures but exhibited slight strength loss in $-5^{\circ}C$ at 28days. Especially, concrete with FA and BS was observed in early stage at low curing temperature because of strength loss remarkably in $-5^{\circ}C$.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.469-472
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• 2006

Amount used of admixture fare is increasing for concrete economic efficiency and ability security. Security of economic efficiency and ability can expect by use of this admixture fare but is displaying a lot of problems on early age strength hold by hydrate delay relatively. Specially, in the case of construction site, concrete strength can speak that interrelation is high with mold removal of forms time. Therefore, is economical and need examination of plan that can secure robber within 3 days using admixture fare such as fly ash and blast furnace slage differential speech to secure function. In this study, adding liquid admixture within 1% of a binding agent quantity to examine these problem with physical characteristic after hardening ago specially, strength change at standard and air dry curing of observed change in priority. Air dried and water curing total strength enhancement effects appeared by thing which is in case of add test result liquid admixture by below 1% and strength deputy by passage of age could know is not big.

• 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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• 2018.05a
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• pp.214-215
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• 2018

This paper has been researched that the earlier compressive strength of the cement pastes containing nano-TiO₂ particle curing 1day, 3days and 7days. For the compressive strength measurements, all samples(dimensions 50×50×50mm) were prepared in accordance with ASTM C109. The compressive strength of the specimens with nano-TiO₂ at the early age(1day, 3days and 7days) stage was lower than that of the reference group. Therefore, nano-TiO₂ has little positive effect on the improvement of the compressive strength of cement pastes during early ages.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.05a
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• pp.54-55
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• 2018

Reinforced concrete is a building material that is generally used in modern society. Securing the performance of reinforced concrete is directly connected to the durability and longevity of the building. One of the major factors that deteriorate the durability of concrete is harmful ion. Recently, the quality and improvement method of reinforced concrete for penetration of harmful ion has been studied. In this study, the bead type ion exchange resin is substituted for 0%, 3%, and 6% of the fine aggregate volume in the mortar. The speciments underwent underwater curing and were checked for compressive strengths of 3 days and 28 days. From the results of compressive strength, it can be seen that the higher the substitution ratio of the ion exchange resin, the lower the early strength and long-term strength development, especially the early strength development.

• Journal of Environmental Science International
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• v.19 no.1
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• pp.105-114
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• 2010

The objective of the paper is to experimentally investigate the compressive strength of the concrete incorporating fly ash. Ordinary Portland cement(OPC). Water to binder ratio(W/B) ranging from 30% to 60% and curing temperature ranging from $-10^{\circ}{\sim}65^{\circ}C$ were also adopted for experimental parameters. Fly ash was replaced by 30% of cement contents. According to the results, strength development of concrete contained with fly ash is lower than that of plain concrete in low temperature at early age and maturity. In high curing temperature, the concrete with fly ash has higher strength development than that of low temperature regardless of the elapse of age and maturity. Fly ash can have much effect on the strength development of concrete at the condition of mass concrete, hot weather concreting and the concrete products for the steam curing.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.11a
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• pp.131-132
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• 2021

According to the domestic specification, the curing of the specimen for strength management used to determine the time of the mold deformity of the structure concrete in early spring and early autumn is cured in the field structure condition. However, when the seal curing is performed in the field, the temperature of the specimen is very low compared to the temperature of the actual structure, so the strength of the structure concrete predicted based on the strength of the specimen is much undervalued than the actual one, which causes the mold to be deformed. Therefore, this study analyzed the temperature history and compressive strength characteristics of the specimen for strength management through other sealing curing at 5℃ and concrete of the actual structure, and presented the most suitable curing method.

• Journal of Industrial Technology
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• v.23 no.A
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• pp.165-173
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• 2003

The purpose of this paper is to analysis of initial behavior of concrete pavement with initial measurement strain gauge for concrete pavement at field, and to investigate the field test results for field applicability testing. The early-age behaviors of concrete pavement slabs were measured using the strain gauges. From the slab depths and positions, the outputs from each gauges were recorded at initial curing period. The initial measurement of concrete pavement and check of crack at the joint were performed, the results could be summarized as follows. From the results of concrete strength, compressive strength and flexural strength were showed $271kgf/cm^2$, $43kgf/cm^2$ respectively. From the tests of early-age strain measurement, it was found that the strain varied at the maximum value of $150{\mu}{\varepsilon}$ and early behavior of concrete slab was showed a tensile strain. However, for long-term was showed a compressive strain due to dry-shrinkage.

• Journal of Industrial Technology
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• v.27 no.A
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• pp.103-110
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• 2007

Concrete is a material that will crack during its service life by its very nature. For bridge decks this is especially significant as these cracks allow accelerated ingress of chlorides and the subsequent corrosion of the reinforcing steel and deck deterioration. Very-early strength latex-modified concrete (below ; VES-LMC) was developed in order to realize early-opening-to-traffic bridge deck concrete. Although there has been little research to document the degree of cracking in VES-LMC overlay, there has been a general perception among highway agencies that overlay cracking of VES-LMC, particularly early-age cracking, is a one of problems which should be solved. The purpose of this study was to analyze the cause of map, transverse and longitudinal cracking in VES-LMC and to provide a control methods for minimizing the occurrence of cracks. The proposed prevention against map and transverse cracking was verified by field applications. VES cement was modified, the unit cement contents was reduced into $360kg/m^3$ from $390kg/m^3$, the maximum size of coarse aggregate was increase into 19mm from 13mm, wire mesh and steel fibers were incorporated in concrete mixture.