• Magazine of the Korea Concrete Institute
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• v.8 no.4
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• pp.141-148
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• 1996

The pulished works on Accelerated Curing Effect were generally performed around from 1960 to 1970th century for 18 to 24 hours - total curing periods. It is not possible to define the effect of temperature rise because those results were obtaine mainly by using the manually operated steam-curing tank. Thus, it may not be available to apply those data immediately on the domestic PC wall production line. The testing specimens were made from the standard mix proportion according to those of domestic PC factories to establish a basic data for the Accelerated Curing Effect. The experimental tests were conducted according to the conditions of each sub-curing periods. By comparing the results of compression tests on de-molded and 28-day water-curing specimens, we find that the most effective curing condition to obtain more than the required design strength after 28 day of water curing may be as follows: the presteaming period does not affect seriously and less than$30^{circ}C/hr$- the rate of temperature rise andless than $82^{circ}C$ - maximum temperature are necessary. It seems that post-curing procedure is very important factor to increase the effect of accelerated curing.

• Journal of the Korea Concrete Institute
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• v.15 no.4
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• pp.541-548
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• 2003

This study is to investigate the temperature curve and development of compressive strength due to the curing conditions and to evaluate the optimum curing condition of test specimens showing the same development of strength to that of real structures in cold weather. The results of temperature curve with curing conditions in mock-up tests showed the trend of decrease plain concrete with insulation form, plain concrete with heating, concrete with accelerator for freeze protection, and control concrete in turn. The strength development of plain concrete of inside and outside of shelter showed the very slow strength gains due to early freezing, but that of concrete with accelerator for freeze protection showed the gradual increase of strength with time. From this, it is clear that accelerator for freeze protection has the effects of reducing the freezing temperature and accelerating the hardening under low temperature. Strength test results of small specimens embedded in members and located in insulation boxes at the site are similar to that of cores drilled from the members at the same ages, thus it is clear that these curing methods are effective for evaluation in-place concrete strength.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.5
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• pp.63-71
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• 2010

This paper is about a research of steam curing which is one of the curing methods for accelerating the early-age strength of pre-cast concrete. With cylinder mold and mock-up specimen, the research was executed to study the best cycle of steam curing temperature through quantifying cycle of steam curing and maximum temperature, while the required strength is developed under the early-age. Moreover, causes and measurements for the high temperature of concrete, which is due to the steam curing, and the crack, which occurs when removing steel form, are stated. Ultimately, the economical method of producing, which satisfies early-age strength development and quality assurance while manufacturing PC structure, is stated.

• Journal of the Korea Concrete Institute
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• v.27 no.6
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• pp.669-676
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• 2015

Time dependent model for prediction of compressive strength development of concrete cured by microwave heating form was presented in this study. The presented model is similar to the equation which is given in ACI 209R-92 but the constants which is dependent on cement type and curing method in the presented model are modified by the regression analysis of the experimental data. Laboratory scale concrete specimens were cast and cured by the microwave heating form and drilled cores extracted from the specimens were fractured in compression. The measured core strengths are converted to standard core and in-situ strengths. These in-situ strengths are used for the regression.

• Korean Journal of Agricultural Science
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• v.8 no.2
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• pp.185-194
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• 1981

This study was carried out to determine the effect of accelerated curing on the strength of standard sand mortar and briquette ash mortar. The standard sand mortars and the briquette ash mortars made by mixture of the standard sand:cement and the briquette ash:cement at the ratio of 2 : 1, 3: 1 and 4 : 1, respectively, were cured at 4 different temperature of $20^{\circ}C$, $60^{\circ}C$, $80^{\circ}C$ and $100^{\circ}C$. The compression and tensil strength of mortars were measured at ${\sigma}_3$, ${\sigma}_7$, ${\sigma}_28$. The results obtained are summarized as follows; 1. At each age of curing and each curing temperature, the compression and tensile strength of the mortars made by the mixture of cement and standard sand was significantly higher than that of the mortars made by the mixture of cement and briquette ash. But the increasing rate of strength in compression and tension was significantly higher at the mortars of cement and briquette ash than those of cement and standard sand. 2. The strength of mortars which showed lower strength than Korean Standard at ordinary curing temperature was significantly increased and showed higher value than Korean Standard by the accelerated curing at high temperature. The increasing rate of strength by the accelerated curing was higher at the mortars containing less amount of cement than those containing more cement. The hardening of the mortars containing less amount of cement was significantly promoted by the accelerated curing in high temperature. 3. When the briquette ash was substituted for the materials of cement mortar, decline of the mortar strength is. unavoidable. But the enhancement of the mortar strength is still expected by the experimental results that the strength of cement-briquette ash mortar showed an increase of 137.6% by the accelerated curing at $60^{\circ}C$, 164.1% at $80^{\circ}C$ C and 183.8% at $100^{\circ}C$, respectively, compared with the strength of mortar cured at $20^{\circ}C$ for 28 days. 4. As the strength of cement briquette mortar is lower than that of cement standard sand mortar, the cement briquette ash mortar is expected to be increased in strength by the accelerated curing at high temperature. The cement briquette mortar is expected to be utilized to the production of secondary mortar goods or the constructions which need low strength of mortar.

• Journal of the Korean Wood Science and Technology
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• v.8 no.1
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• pp.1-12
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• 1980

경화촉진제로서 염화칼슘, 경화억제제로서 수크로오즈를 처리한 포트렌트시멘트의 양생효과를 전자현미경에 의해 관찰한 결과, 경화억제제를 처리한 시멘트는 결정을 이루지 못하고 융기상태로 남아있고, 경화촉진제를 처리한 시멘트는 겔형으로 변한후 육각형의 결정을 이루는 것이 관찰되었다. 또한 시멘트-목재 복합체의 양생은 좀 다른 양상을 보이고있어 경화제가 처리된 WCC는 포플러 스리버 표면에서 작은 융기가 겔상의 표면에 많이 관찰되나 무처리는 거의 일정한 모양의 입자가 관찰되어 시멘트 경화촉진제와 억제제의 효과를 구명하였다.

• Journal of the Korea Concrete Institute
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• v.15 no.2
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• pp.254-262
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• 2003

In this study, the results of applying cold weather concreting mixed with Accelerator for Freeze Protection(AFP) to full scale structures are presented. Since the determination of W/C and amount of AFP significantly have an effect on strength gain and protection of frost damage in early, a full investigation is needed to determine these values at stage of nux design. The flowability of fresh cold weather concreting with AFP was similar to the same W/C. Lower loss of workability and initial slump flow of concrete using superplasticizer of polycarboxylic ester than that of melamine sulphonate showed that polycarboxylic ester was more effective on elapsed time. Temperature histories of specimens located in insulation boxes at the site was similar to that of structures. Thus, it is cleared that simple adiabatic curing method is effective for evaluating in-place concrete strength than specimens cured by sealing method. The investigation results of development of compressive strength of cold weather concreting included AFP with curing methods by logistic curves indicated that AFP can be effective to gain strength at lower temperature than normal curing temperature. In field testing, vinyl sheets were placed over the concrete sections and AFP enabled concrete to gain $5N/{mm}^2$ to protect frost damage in early ages and specified compressive strength of concrete at 28 days under average temperature of $-2^{\circ}C$ (lowest temperature was $-12^{\circ}C$) during site application.

• Journal of the Korea Concrete Institute
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• v.14 no.6
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• pp.942-948
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• 2002

When fresh concrete is exposed to low temperature, the concrete may suffer frost damage due to freezing at early ages and the strength development may be delayed. One of the solution methods to resolve these problems is to reduce freezing temperature of concrete by the use of chemical admixture called Accelerator for freeze protection. In this study we Investigate the effect on the strength development of cement mortar using accelerator for freeze protection with the variable curing condition. As the result of this study, the mortar using accelerator for freeze protection show continuously the strength development in curing condition of -5$^{\circ}C$. And the compressive strength under variable temperature condition was higher than constant temperature condition in same maturity.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.7 no.3
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• pp.203-212
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• 1987

The hydration and strength of concrete are affected by curing conditions, especially curing temperature. In this paper, the hydration temperature of heated curing concrete specimen are measured by thermo-couples instead of conduction calorimeter, and strengths of concrete are tested. The results of this study show that the compressive strengths of concrete are especially dependent on the curing temperature. And the strength results of concrete agree approximately with the results of approach to the hydration process of cement concrete.

• Journal of the Korea Concrete Institute
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• v.28 no.3
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• pp.309-316
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• 2016

In this study, performance of hardening accelerator types which promote setting and hardening of cement has been reviewed in order to develop early age strength of concrete with compressive strength of 21~27 MPa after examination of strength development of the concrete at early age according to curing temperature and unit cement(binder) content. As results, soluble mineral salt showed better hardening acceleration effect than organic salt in the scope of this study. Also, hydration reaction accelerating effect of $C_3S$ by Soluble mineral salt is effective on development of early age compressive strength and it was shown that the Pt's hydration reaction accelerating effect was the best. Construction duration reduction can be expected by securing compressive strength for prevention of early aged freezing damage in 25hour-curing time under curing temperature at $15^{\circ}C$. Also, it was shown that compressive strength of specimen cured at $5^{\circ}C$ was similar with plain specimen cured at $10^{\circ}C$. Therefore, it is expected that fuel costs and carbon dioxide can be reduced when the same construction duration is considered.