• Proceedings of the Korea Concrete Institute Conference
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• 1998.04a
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• pp.187-192
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• 1998

Recent construction method in mass concrete structures would depend on the control of hydration heats and thermal stresses by using the low heat cement, optimized block size and a lift height, or both. This experimental study aims at the possibility of thermal cracks according to the different types of cementations material and at the investigation of these effects. Four different types of cements are applied to the mock-up test and are evaluated in terms of temperature rises and thermal stresses with the use of thermocouples, strain gauges and effective stress gauges. As a result of this study, it was found that stresses measured from effective stress gauges agree well with ones form strain gauges, and the trend of stress occurrence can be well evaluated from theoretical analysis.

• Proceedings of the Korea Concrete Institute Conference
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• 1993.10a
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• pp.45-50
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• 1993

This paper describes some results of various tests which were carried out with varying the fineness of salg from 6000 to 10000$\textrm{cm}^2$/g and the slag content in cement from 30 to 50wt% for the perpose of utilizing finely ground blast-furnace slag as an ingredient for high-performance concrete. Test for heat of hydration, microstructural and hydration characteristics in paste, and fluidity and compressive strength in mortar were carried out. From these test results, it was found that, by properly determining the content and fineness of the slag, it is possible to manufacture high-performance concrete that has low heat of hydration, high early strength development, fine pore size and a highly densified microstructure.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.11a
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• pp.29-30
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• 2020

In this study, as part of the foundation for advancing the material compounding aspect to reduce hydration heat cracks in the mat foundation on which the mass concrete is constructed, the degree of concrete varieties of cement is used. The setting time was measured and comparative analysis was performed. Results It was confirmed that the concrete using LHC was more effective than the concrete using OPC in reducing the use of SP, the calorific value of the concrete was low, and it was more effective in preventing cracks. It is also terminated after 10 hours and it is determined that the use of LHC can reduce the cracks caused by the heat of hydration of the mat foundation.

• Journal of the Korea Institute of Building Construction
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• v.22 no.4
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• pp.337-345
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• 2022

The foundation of high-rise concrete building in coastal areas generally must be installed in an integrated manner, not separately, in order to prevent defects caused by stress on the upper and lower parts of the mounting surface and to manage the process smoothly. However, when performing integrated punching, there is a concern that temperature stress cracks may occur due to hydration heat. Due to the large member size, it is difficult to make a sufficient commitment, so it is necessary to mix concrete with high self-charging properties to ensure workability. In this research, the amount of high-performance spray and admixture used was adjusted as experimental variables to satisfy this required performance. Through the analysis of the results for each blending variable, it was found that the unit quantity was 155kg/m³ and the cement ratio in the binder was 18%, and the target values of the pre-concrete properties and compressive strength were satisfied. A four-component binder(18% cement, 50% slag fine powder, 27% fly ash, 5% silica fume) was used.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.2
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• pp.190-197
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• 2020

This paper evaluates the mechanical properties and durability of cement matrix blended with mineral admixtures and ferronickel slag(FNS) powder which is an industrial b y-product during ferronickel smelting process. The hydration heat, pore structure, compressive strength, length change, rapid chloride penetration test(RCPT), and freezing and thawing resistance of ternary blended cement matrix were investigated and compared with ordinary portland cement matrix. The result showed that the compressive strength of ternary blended cement matrix using ferronickel slag powder and mineral mixture was low in strength compared to the reference concrete, but recovered to a certain extent by using alkali activator. Length change of cement mortar using FNS powder have shown less shrinkage occurs than the reference specimen. In addition, irrespective of using the alkali-activators, all ternary mix are indicative of the 'very low' range for chloride ion penetrability according to the ASTM C 1202, and the freeze-thaw resistance also showed excellent results.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.3
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• pp.1059-1065
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• 2010

Very-early strength latex-modified concrete (VES-LMC) was developed for the purpose of fast-track overlay of a concrete bridge deck under heavy traffic, concentrated on the workability, durability, and strength gain so that it can be opened to the traffic only three hours after its placement. The mixture of VES-LMC might accompany very high heat of hydration at early-age because of its inherent rapid hardening property and could have susceptibility to autogenous shrinkage because of its relatively low water-cement ratio. This study evaluated the effect of the latex-cement ratio(L/C) both of the constant and variable slumps on the autogenous shrinkage of VES-LMC by carrying out simple temperature rise test and early-age shrinkage experiment. Test results are as follows: The latex contributes on the enhancement of the concrete durability but has little effect on its hydration and the accompanied heat of hydration in VES-LMC. Autogenous shrinkage increased with the increase in latex-cement ratio at variable slumps and its pattern followed regularly a logarithmic increase. However, the influence of water-cement ratio and latex-cement ratios for the test specimens at constant slump on early-age autogenous shrinkage property was found to be minor due to the simultaneous effect of the two experimental variables.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2016.10a
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• pp.150-151
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• 2016

In previous study, researchers studied development of early anti-freezing cement at low temperature (-5℃) using hydration characteristics of reduction slag. In this study, the durability of concrete using reduction slag was conducted. The experiment result, reduction slag makes high temperature and improves compressive strength due to quick setting. And then result of durability show that it is no problem. However, it is considered that further study is needed about high shrinkages which was indicated in dry shrinkage.

• Journal of the Korea Concrete Institute
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• v.20 no.6
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• pp.797-807
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• 2008

For this study, the semi-adiabatic temperature rising test is accomplished by using ternary system cement (OPC, BFS, FA) reducing temperature crack. Two tests are conducted; one is for the paste test, and the other is for the concrete test. As the results of paste tests, using fly ash is better to reduce hydration temperature than doing blast furnace slag. In the case of the paste mixed ternary system cement, the more fly ash is mixed and the less blast furnace slag is used, the lower the temperature is. The less the mixture ratio of blast furnace slag is and the more the mixture ratio of fly ash is, the later the temperature rising velocity and descending velocity are. Besides, the temperature is lower if water/binder ratio is high. The use of ternary system cement has the retardation effect of temperature rising because the time to reach the maximum temperature is in the order of OPC100, binary system cement, and ternary system cement. From the test, the maximum temperature of concrete used ternary system cement is $8{\sim}11^{\circ}C$ lower than that of concrete used OPC100. Moreover, temperatures rising velocity and descending velocity of ternary system cement range $47{\sim}51%$ and $37{\sim}42%$ compared with OPC100. The specimen of concrete shows remarkable low internal temperature and slow temperature rising velocity and descending velocity compared with the specimen of paste because it is that temperature loss of concrete is much more than paste specimen according to aggregates.

• Korean Journal of Materials Research
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• v.26 no.10
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• pp.521-527
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• 2016

Geopolymers have many advantages over Portland cement, including energy efficiency, reduced greenhouse gas emissions, high strength at early age and improved thermal resistance. Alkali activated geopolymers made from waste materials such as fly ash or blast furnace slag are particularly advantageous because of their environmental sustainability and low cost. However, their durability and functionality remain subjects for further study. Geopolymer materials can be used in various applications such as fire and heat resistant fiber composites, sealants, concretes, ceramics, etc., depending on the chemical composition of the source materials and the activators. In this study, we investigated the thermal properties and microstructure of fly ash and blast furnace slag based geopolymers in order to develop eco-friendly construction materials with excellent energy efficiency, sound insulation properties and good heat resistance. With different curing times, specimens of various compositions were investigated in terms of compressive strength, X-ray diffraction, thermal property and microstructure. In addition, we investigated changes in X-ray diffraction and microstructure for geopolymers exposed to $1,000^{\circ}C$ heat.

• Journal of the Korea Institute of Building Construction
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• v.20 no.6
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• pp.489-495
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• 2020

Whereas the control of the hydration heat in mass concrete has been important as the concrete structures enlarge, many conventional strategies show some limitations in their effectiveness and practicality. Therefore, In this study, as a solution of controling the heat of hydration of mass concrete, a method to reduce the heat of hydration by controlling the hardening of cement was examined. The reduction of the hydration heat by the developed Phosphate Inorganic Salt was basically verified in the insulated boxes filled with binder paste or concrete mixture. That is, the effects of the Phosphate Inorganic Salt on the hydration heat, flow or slump, and compressive strength were analyzed in binary and ternary blended cement which is generally used for low heat. As a result, the internal maximum temperature rise induced by the hydration heat was decreased by 9.5~10.6% and 10.1~11.7% for binder paste and concrete mixed with the Phosphate Inorganic Salt, respectively. Besides, the delay of the time corresponding to the peak temperature was apparently observed, which is beneficial to the emission of the internal hydration heat in real structures. The Phosphate Inorganic Salt that was developed and verified by a series of the aforementioned experiments showed better performance than the existing ones in terms of the control of the hydration heat and other performance. It can be used for the purpose of hydration heat of mass concrete in the future.