• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.165-168
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• 2005

This paper investigated the effect of W/C and the kinds of cement on the chloride invasion resistance of the offshore concrete. W/C set up 0.30, 0.35, 0.40 and The kinds of cement were used four(ordinary portland cement, ground granulated blast-furnace slag cement, belite cement, low heat portland cement). For the electrical migration test, NT BUILD 492's method was used to estimate the migration coefficient of chloride ion. As a result, the migration coefficients of chloride ion of concrete according to w/c were shown reducing with the w/c increasing, and according to kinds of cement were shown discrepancy in chloride invasion resistance. Especially blast-furnace slag cement was most low it. In the each cement, the compressive strength was shown related to the migration coefficient.

• Advances in concrete construction
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• v.5 no.2
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• pp.101-115
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• 2017

Cement kiln dust (CKD) is one of the most important waste materials in the cement industry. The large amount of this material, has encouraged researchers to propose new ways to recycle and reuse it. In this paper, effects of adding cement kiln dust to the ordinary Portland cement, on the physical and mechanical properties of ordinary and lightweight concrete were investigated. Results showed that concrete containing CKD, presents lower workability and modulus of elasticity; however, improvements in strength was observed by adding particular amounts of CKD. Eventually, it was found that adding 10% of cement weight CKD is the appropriate percentage for utilizing in manufacturing ordinary and lightweight concrete.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2005.05a
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• pp.61-64
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• 2005

Recently, there have been many studies about recycling cementitious powder from concrete waste(hereinafter referred to as waste powder), generated after recycle aggregate production. Previous studies showed that when the heating process of waste powder at $700^{\circ}C,\;Ca(OH)_2$ in paste is dehydrated making possible the restoration of hydraulic properties. Recycled cement with hydraulic properties restored is thought to be re-hydrated through the mechanism of hydration, which is almost similar in Portland cement. This clearly suggests that the hydrate of recycled cement is alkali in type. Like in general concrete, if recycled cement is used as a structural material, resistance performance against carbonation or neutralization by $CaCO_3$ in air probably would be most influential to the life of steel-reinforced concrete structure. Thus the purpose of this study is to make an experimental review on chemical properties of recycled cement, manufactured with concrete waste as base material, and investigate the durability of concrete using recycled cement through evaluating the cement s performance of resistance to carbonation in accordance with its accelerating age. Based on its results, further, the study seeks to provide basic information about ways of utilizing recycled cement.

• Journal of the Korea Institute of Building Construction
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• v.6 no.4 s.22
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• pp.61-68
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• 2006

Recently, there have been many studies about recycling cementitious powder from concrete waste(hereinafter referred to as waste powder), generated after recycle aggregate production. Previous studies showed that when the heating process of waste powder at $700^{\circ}C,\;Ca(OH)_2$ in paste is dehydrated making possible the restoration of hydraulic properties. Recycled cement with hydraulic properties restored is thought to be re-hydrated through the mechanism of hydration, which is almost similar in Portland cement. This clearly suggests that the hydrate of recycled cement is alkali in type. Like in general concrete, if recycled cement is used as a structural material, resistance performance against carbonation or neutralization by $CaCO_3$ in air probably would be most influential to the life of steel-reinforced concrete structure. Thus the purpose of this study is to make an experimental review on chemical properties of recycled cement, manufactured with concrete waste as base material, and investigate the durability of concrete using recycled cement through evaluating the cement's performance of resistance to carbonation in accordance with its accelerating age. Based on its results, further, the study seeks to provide basic information about ways of utilizing recycled cement.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.607-612
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• 2002

In road pavements, it is known that cement concrete pavement has superior durability, safety compared. But in repairing pavement, cement concrete pavement is not usually applied because of the length of time while the road is interrupted when using Ordinary and Rapid-hardening Portland Cement. And Super High Early Strength Cement and Ultra Super High Early Strength Cement are not favorable for ready mixed concrete because of rapid setting time, high slump loss and other restrictions. We developed special cement developing 1 day strength of over 30.0N/mm$^2$ to open the road within 1 day and workable time is maintained over 1 hour so that it can be used as ready mixed concrete. We performed experimental overlay construction with the cement and evaluated the mechanical property and the durability. At curing temperature of 8-l8$^{\circ}C$,the flexural strength was 6.4N/mm$^2$at 1 day, so that the road can be open to traffic within 1 day. In durability test, the hardened concrete showed higher durability than Portland cement concrete.

• Journal of the Korea Concrete Institute
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• v.11 no.4
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• pp.21-29
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• 1999

In this study, an experiment was performed to analyze the influence of water-cement ratio on the fundamental characteristics of antiwashout underwater concrete using blended sand (sea sand:river sand = 1:1). The water-cement ratio (45%, 50%, 55%, 60%), andtiwashout underwater agent contents (0.82%, 1.00%, 1.14% of water contents per unit volume of concrete), and superplasticizer contents (1.5%, 2.0%, 2.5% of cement contents per unit volume of concrete) were chosen as the experimental parameters. The experimental results show that the underwater segregation resistance, unit weight of hardening concrete and compressive strength were increased as the water-cement ratio decreased and as the antiwashout underwater agent contents increased. On the other hand, the flowability(slump flow) was increased to the 55% of the increase of water-cement ratio, however, it was decreased at the ratio of 60%. From this study, the antiwashout underwater concrete can potentially be used as a materials underwater work of ocean if the water-cement ratio and chemical admixture contents for the suitable balance between cost and performance are properly selected.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.297-302
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• 2001

SRC pier at KTE 6-1 construction area is a very important structure. Precise control of quality is needed. This pier has 3.50m$\times$3.73m section and 38.20m length. So this structure must be treated as mass concrete and thermal crack caused by hydration heat should be controled. In this project belite cement concrete is used to control the thermal crack. As a result of adapting belite cement concrete perfect control is achieved. Finally, hydration heat FEM analysis of horizontal element is executed for Ordinary Portland Cement concrete and belite cement concrete. In comparison of two results, it is confirmed that using low heat portland cement concrete is necessary.

• Computers and Concrete
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• v.13 no.1
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• pp.97-115
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• 2014

Silica fume is a by-product of induction arc furnaces and has long been used as a mineral admixture to produce high-strength, high-performance concrete. Due to the pozzolanic reaction between calcium hydroxide and silica fume, compared with that of Portland cement, the hydration of concrete containing silica fume is much more complex. In this paper, by considering the production of calcium hydroxide in cement hydration and its consumption in the pozzolanic reaction, a numerical model is proposed to simulate the hydration of concrete containing silica fume. The heat evolution rate of silica fume concrete is determined from the contribution of cement hydration and the pozzolanic reaction. Furthermore, the temperature distribution and temperature history in hardening blended concrete are evaluated based on the degree of hydration of the cement and the mineral admixtures. The proposed model is verified through experimental data on concrete with different water-to-cement ratios and mineral admixture substitution ratios.

• Proceedings of the Korea Concrete Institute Conference
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• 1995.10a
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• pp.14-18
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• 1995

Since cement is one of materials of concrete and have an important effect upon physical properties of concrete, the quality characteristics of ordinary portland cement in domestic market are evaluated in this study. For this purpose, eight kinds of cement are selected and tested on the specific gravity, normal consistency, setting time, fincness, and compressive strength of cement ranged from 300kg/$\textrm{m}^3$ to 600kg/$\textrm{m}^3$ are tested for each kind of cement. As a result,ordinary portland cement in domestic market are satisfied with physical performance prescribed by KS L 5201(Portland Cement) and when unit weight of cement is 300~600kg/$\textrm{m}^3$, the maximum compressive strength of concrete cylinder is showed to be about 440-540kgf/$\textrm{cm}^2$.

• International Journal of Concrete Structures and Materials
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• v.11 no.1
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• pp.59-68
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• 2017

Mercury intrusion and nitrogen sorption porosimetry were employed to investigate the pore structure of calcium sulfoaluminate ($C{\bar{S}}A$) and portland cement pastes with cement-to-water ratio (w/c) of 0.40, 0.50, and 0.60. A unimodal distribution of pore size was drawn for $C{\bar{S}}A$ cement pastes, whereas a bimodal distribution was established for the portland cement pastes through analysis of mercury intrusion porosimetry. For the experimental results generated by nitrogen sorption porosimetry, the $C{\bar{S}}A$ cement pastes have a smaller and coarser pore volume than cement paste samples under the same w/c condition. The relative dynamic modulus and percentage weight loss were used for investigation of the concrete durability in freeze-thaw condition. When coarse aggregate with good freeze-thaw durability was mixed, air entrained portland cement concrete has the same durability in terms of relative dynamic modulus as $C{\bar{S}}A$ cement concrete in a freeze-thaw environment. The $C{\bar{S}}A$ cement concrete with poor performance of durability in a freeze-thaw environment demonstrates the improved durability by 300 % over portland cement concrete. The $C{\bar{S}}A$ concrete with good performance aggregate also exhibits less surface scaling in a freeze-thaw environment, losing 11 % less mass after 297 cycles.