• Proceedings of the Korea Concrete Institute Conference
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• 1995.04a
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• pp.164-169
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• 1995

Cracks in the concrete structure are known to develope by various mechani는, including an alkali-aggregate reaction. The alkali-silicate reaction between aggregates and cement is studied using polarized microscope, electron probe microanalyser and electron microscope. Metamorphosed, biaxial quartz and feldspars grains appear to have reacted readily with alkali from cement. For a given mineral, fine-grained minerals tend to react readily over the coarse-grained ones. A chemical analysis shows that the elements K, Na, Ca, and Si migrated, in most cases, fro the portion of h호 concentration to the low, Some clay minerals, including smectite and illite are newly formed as one of the reaction products. The continual expansion and shrinkage of the expandible clay minerals, probably due to repeated absorption and loss of water within the structure, plays an important role in the development of cracks within the concrete structure.

• Journal of the Korea Institute of Building Construction
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• v.3 no.3
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• pp.73-81
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• 2003

In this paper, salt damage resistance of high durable concrete was tested. High durable concrete was made by using low water cement ratio, chemical admixture called super-durable admixture and mineral admixtures such as fly-ash, ground granulated blast-furnace slag, silica fume. Two kinds of salt damage resistance test were carried out. One method is chloride ion penetration test(ASTM C1202), and the other one is depth of chloride penetration test in saline solution. Test results were as followers: 1) The depth of chloride ion penetration increased exponentially as water cement ratio was increased and time passed. 2) Super-durable admixture had little effect on the improvement of salt damage resistance of concrete. 3) Silica fume and ground granulated blast-furnace slag were effective on salt damage resistance because of pozzolanic reaction, but fly-ash had a little effect.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.919-924
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• 2001

The purpose of this study is to prepare the basic data for the development of building board with expanded perlite. Each paste was mixed with four levels of water cement ratio(30, 40, 50, 60%), and expanded perlite was substituted with four levels of substitutive ratio(20, 40, 60, 80%) for the each paste. The physical property, compressive strength, bending strength and thermal conductivity of each cement composite which is made through previously described method were analyzed and the result was as follow. In the case of 80 percent substitutive ratio, the cement composite had a mechanical defect which was resulted from lack of paste content. In the case of 40 and 60percent substitutive ratio, the cement composite had sufficient strength, light weight and low thermal conductivity for application to fire resisting board.

• Journal of the Korea Concrete Institute
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• v.17 no.5 s.89
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• pp.853-856
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• 2005

A low water/cement ratio leads to autogenous shrinkage of cement paste at an early age. This autogenous shrinkage is related to the change of relative humidity in the pore structure that is formed during the hydration process. The relationship between autogenous shrinkage and relative humidity change are relatively well defined today, but the effects of temperature on autogenous shrinkage, relative humidity, and pore structures have been studied less systematically. This study focused on correlating alterations of these properties of cement paste hydrated at constant temperatures of 20, 40, and $60^{\circ}C$. The test results clearly indicate that increasing curing temperature resulted in increased porosity, particularly for pores between 5 to 50 nm as measured by MIP, and increased autogenous shrinkages, as a consequence of a reduction of relative humidity at early ages.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.04a
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• pp.64-69
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• 1999

Slags are by-products of the metallurgical industry. The most important slag from the standpoint of the quantity used as building material is iron blastfurnace slag. Slags are either crystalline stable solid used as aggregates or glassy material used as hydraulic binder. Slag cements are low heat of hydration cements. Slags react more slowly with than portland cement but they can be activated chemically. Activatiors can be either alkaline activators such as soda, lime, sodium carbonate, sodium silicate or sulphate activators such as calcium sulphate or phosphogypsum. So, in this study slaked lime was used as an activator that the compressive strength of this modified cement(M1 type) is high range in early age. And initial setting time of M1 type cement was shorter than conventional cements.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.11a
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• pp.23-24
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• 2018

Reinforced concrete is a building material that is generally used in modern society. Also, reinforced concrete structures in high salinity environments have low durability due to corrosion of reinforcing bars due to infiltrated chlorine ions. Anion exchange resins have an ability to immobilize chlorine ions in the resin while releasing their anions. As a material, it has already been shown that it is possible to fix the chloride ion inside the cementitious material through the cement mortar experiment. The purpose of this study is to confirm the compressive strength of cement mortar using powdered anion exchange resin after powdering an anion exchange resin. In order to confirm the chloride ion fixation ability of the powder anion exchange resin, chlorine ion penetration resistance test was carried out.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.725-728
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• 2006

This research investigates the characteristics of chloride fixation in non-sintering cement(NSC) matrix. NSC was manufactured by adding phosphogypsum and slack lime to granulated blast furnace slag as sulfate and alkali activators. As a result, the concentration of chloride ion in pore solution of NSC-solidified matrix is more low than that of OPC-solidified matrix containing the same chloride content in cement paste. Also, the concentration of chloride ion in pore solution of NSC-solidified matrix is similar with that of BSC-solidified matrix containing the same chloride content in cement paste.

• Proceedings of the Korea Concrete Institute Conference
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• 1992.04a
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• pp.1-6
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• 1992

The objective of this report is to investigate and analyze the influnce of the different base concrete in consistency for the good production of superplasticized concrete (SPC) on the basis of the experimental results. The principal conclusions are summarized as follows. 1. SPC exhibited only slight bleeding in both cases of low and medium consistency of the base concrete, compared to the conventional concrete, compared to the coventional concrete. 2. SPC lost slump and flow value at a much faster rate than the conventional concrete with an equivalent water/cement ratio and initial consistency. 3. The compressive strength of SPC was fount to be higher than that of base and conventional concrete, and the case of base concrete with medium consistency showed a little more incretment than low consistency

• International Journal of Concrete Structures and Materials
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• v.7 no.4
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• pp.287-293
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• 2013

Strength and some durability properties of concrete containing rice husk ash (RHA) predominantly composed of amorphous silica at a specific surface of 235 $m^2/kg$ produced using a charcoal incinerator were determined. The maximum ordinary Portland cement (OPC) replacement with the RHA increased with increase in water/binder (w/b) ratio of the concrete mixes. The results show that 15 % OPC could be substituted by the RHAwithout strength loss at w/b ratio of 0.50. The split tensile strength generally increased with increase in RHA content for the mixes.

• Journal of the Korea Institute of Building Construction
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• v.15 no.4
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• pp.367-373
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• 2015

In this study, fundamental properties of cement were reviewed to apply high fineness cement at low temperature environment. The classified high fineness cement has large proportion of particles below $10{\mu}m$ which affects early hydration: an overall reaction of cement hydration faster. As a result of using high fineness cement, setting time of concrete was reduced and compressive strength was higher than OPC at all ages. Especially, compressive strength was more than double its value compared with OPC after three days curing in low temperature. Faster reaction and higher heat of hydration was verified by calorimetry early and maximum heat of hydration was analyzed by adiabatic temperature raising test. The analysis of this study confirmed that high fineness cement can be suitable to be used in low temperature environment.