• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.175-178
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• 1999

In most domestic construction fields, excessive cement content has been used because of stubborn official inspection. The purpose of this study is to reduce the cement content of mix proportioning for the decrease of hydration heat, brittleness and drying shrinkage which governs durability of concrete significantly. Parameters includes the compressive strengths, type and dosage rate of chemical and mineral admixtures and types of concrete. It is found that the chemical admixture is efficient to the reduction of cement content for high strength concrete (400kg/$\textrm{cm}^2$) and the effectiveness of mineral admixtures in the low strength concrete is somewhat higher than the high strength concrete.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2022.11a
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• pp.171-172
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• 2022

This study aims to develop the hydration heat reducing material (powder type) to lower the heat of hydration of mass members in the extremely hot weather condition. In this study, we applied the developed material to the concrete that used two kinds of binders with cement and evaluate the concrete properties with it.

• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.2
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• pp.176-183
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• 2022

High-purity waste CNTs were mixed into cement mortar to manufacture heat-generating concrete that can use low voltage power, and carbon fiber and waste cathode materials were also used improve the conductivity of the mortar. The waste CNTs were analyzed to have a high concentration of multi-walled CNTs, and substituted liquid type waste CNTs were used during mortar mixing in order to increase dispersibility. The temperature change of the mortar with CNT was evaluated when using electric power below DC 24 V in order to utilize a small self-generation facility such as small solar power module when the mortar heats up and to minimize electromagnetic waves. When liquid-type waste CNTs were applied and a voltage of DC 24 V was introduced, it rose to 60 ℃ in a 200 × 100 × 50 mm mortar block specimen. The field applicability of self heating mortar with waste CNT was sufficient and also the amount of change in heat energy in mortar with liquid type waste CNT, carbon fiber and waste cathode materials is more effective compared to it of other variables.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2008.11a
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• pp.31-36
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• 2008

This study aims to examine the effects of thickness of the concrete members and curing temperature on the properties of low heat concrete through heat of hydration analysis. Type of the members that was analyzed in the experiment is ternary mixture of ordinary portland cement, blast-furnace slag incorporating ratio(20%) and fly ash incorporating ratio(30%), which formed a mat foundation. Thicknesses of the concrete members were 1, 2 and 3(m) and three levels of curing temperatures were 10, 20 and 30(℃). They were applied to analyze the effects on the temperature and thermal cracking index. As a result, for temperature history, temperature difference between the central area and the surface tended to decrease as the thickness of the concrete members get thinner. For the temperature cracking index, on the other hand, the risk of cracking tended to decrease as the curing temperature gets higher and as the thickness gets thinner.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.935-938
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• 2001

This paper reports the relation of concrete setting characteristic and lateral pressure in mass concrete wall such as side wall of LNG underground storage tank. In order to estimate the lateral pressure, initial setting time of low heat cement concrete with type of mineral admixture was measured for three concrete mixtures(W/P=41.6%) containing limestone powder, fly ash, and slag powder. As a result, the lateral pressure of the concrete containing limestone powder was the smallest than those of other concretes as well as the initial setting time.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.249-252
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• 2008

In recent large-scale structures, as mass concrete type structure is frequently applied to the building, temperature crack due to hydration heat needs to be considered. Since a volume change is internally or externally restricted in a mold after placing concrete, temperature crack of mass concrete takes place. By this reason, the reduction method to control this crack is required. In this study, low heat mixture and hydration heat difference is used to execute the analysis of hydration heat, considering the changes of heat transfer coefficient according to curing conditions and block placement of mass concrete. For the analytical modelling, original portland cement and concrete of low heat mixture are placed in the upper and lower payer, respectively. A convection boundary condition is fixed because mass concrete of block placement is characterized by the difference of mold form and curing condition. Through the analysis results considering the changes of low heat mixture, block placement, and heat transfer coefficient, we check out the temperature and stress distribution and analyze the temperature crack reduction effect.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.637-640
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• 2008

In this study, the characteristics of strength development on high volume fly ash concrete(HVFAC)with Type 4 cement was experimentally investigated. Three levels of W/B were selected. Four levels of fly ash replacement ratios and two levels of silica fume replacement ratios were adopted. In the concrete mix, the water content of 125kg/m$^3$ was used, which is less than that of usual water content. As a result, it appeared that the compressive strength gradually decreased with increasing fly ash replacement ratio until 91days. However, regarding the compressive strength, the proper replacement ratio is about 20%, which is low compared to Type I cement case. It was observed that the tensile strength is proportional to the 0.72 power of the compressive strength. It appears that the prediction equation presented in Concrete Standard Specification overestimate the tensile strength in the low strength range, underestimate the tensile strength in the hi호 strength range.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.1035-1040
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• 2003

This research investigates the actual data and construction technology of the massive bottom slab placed by $23,000m^3$ concrete quantity in site of the in-ground type LNG receiving terminal having 20,000kl storage capacity. The purpose of this study is to determine the optimum mix design and control the actual concreting procedures including concrete production, transportation, placement, vibrating and curing in site. For this purpose, the optimum mix design using ternary blended cement(furnace slag cement＋fly ash) and under piping method having 11 gates and 7 distributors are selected. As test results of actual construction, concrete placement is finished during 68hours with good success and obtained the good quality of the fresh and hardened concrete including slump, air contents, no-segregation, compressive strength and low hydration heat. Also, actual data for all of concrete procedures are proved successful and satisfied with our specifications.

• Journal of the Korea Concrete Institute
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• v.24 no.6
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• pp.659-666
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• 2012

To secure the thermal crack resistance of mass concrete, researches and the field applications of low heat portland cement (LPC), ternary blended cement (TBC) which is produced by blending ordinary portland cement with blast furnace slag and fly ash, and early strength low heat blended cement (EBC) increased in recent years. Although the model for adiabatic temperature rise is necessary for estimating the risk of thermal cracking of concrete structures, sufficient data have not been accumulated for these mixtures. In addition, the differences in adiabatic test results have been reported for the volume of test specimens. Therefore, the present study evaluated the characteristics of adiabatic temperature rise based on the type of binder and the volume of the adiabatic test specimen. Test results indicated that the maximum temperature rise ($Q_{\infty}$) and the reaction factor (r) of TBC were the lowest. Test results also showed that $Q_{\infty}$ and r changed with respect to the volume of test specimen. $Q_{\infty}$ and r obtained from 6l equipment were lower than those of 50l equipment. Therefore, corrections with respect to this phenomenon was confirmed and the corrections factors are presented.

• Journal of the Korean Ceramic Society
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• v.19 no.2
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• pp.133-138
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• 1982

Two kinds of clinker liquid melts, one containing 2.0% of $K_2O$ and the other without $K_2O$, were prepared with the similar composition as those developed during the firing of portland cement clinker. One portion of melt was quenched and found to consist of glass together with traces of proto-$C_3A$, and the other portion was allowed to cool spontaneously to crystallize $C_3A$ and calciumferrite well. The product obtained by crystallization of the melt without $K_2O$showed cubic $C_3A$, while orthorhombic $C_3A$ was formed from the crystallized product containing $K_2O$. Studies on the hydration behavior of the samples made from the melts with 30% of gypsum were carried out for 24 hours by observation at regular intervals ettringite, monosulphate hydrates and gypsum which were formed or consumed during hydration. The samples without $K_2O$ in the melts were hydrated wth addition of proper amount of $K_2SO_4$ in the water for hydration. Hydration behavior of glassified $C_3A$ showed that it has low reactivity relative to crystallized $C_3A$, and also hydration reactivity of orthorhombic $C_3A$ was much lower than that of cubic $C_3A$ in 60 minutes. Potassium sulphate in the solution reduced the hydration reactivity of $C_3A$ . Evolution peaks of hydration heat examined by twin-type conduction micro-calorimeter showed that glassified $C_3A$ without $K_2O$ had secondary peak after 9 hours and $C_3A$ containing $K_2O$ after 12 hours. When crystallized $C_3A$ was hydrated, initial peaks of hydration heat were considerably high and there was no secondary peak for cubic $C_3A$ but the secondary peak of orthorhombic $C_3A$ appeared after 4 hours.