• Proceedings of the Korean Institute of Building Construction Conference
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• 2022.04a
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• pp.19-20
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• 2022

Portland Limestone Cement (PLC) is a blended cement using limestone powder as SCMs (Supplementary Cementitious Materials), and is currently regarded as an essential means for achieving carbon neutral in the cement industry. This study was performed to investigate the fresh and hardened properties of cement mortar according to the fineness and replacement ratio of limestone powder. As a result, the compressive strength of mortar used high blaine limestone powder were equivalent level of that of OPC.

• Magazine of the Korea Concrete Institute
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• v.10 no.4
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• pp.195-204
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• 1998

Generally, in order to maintain high strength in concrete, it needs high cement content and low water-cement ratio.makes internal temperature rising after concrete placing inevitably, and happens temperature stress that makes initial cracks of concrete structure. Therefore, to control the thermal stress of high-strength concrete, we made 3 types of the fineness of ground granulated blast-furnace slag and 4 steps replacement. and then measured an amount of temperature rising and elapsed time of maximum temperature and strength of concrete. Also we considered the test results of heat evolution amount and heat evolution of cement paste made with 5 steps replacement by GGBF slag.As result of this study, in case of the 50% of replacement and the 6,000$\textrm{cm}^2$/g of fineness, we obtained satisfactory results that not only the controlled effect of temperature rising but strength at early ages.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2013.11a
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• pp.186-187
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• 2013

Recently, high fluidity concrete is becoming more prevalent. High fluidity concrete uses admixture or thickener in order to prevent separation of materials due to increased fluidity, and, especially, BS is becoming more use for reduced heat of hydration and improved long-term strength. This study examined the effect of BS on fluidity of cement paste from a rheological viewpoint. As for BS types, materials equivalent to 1 types of KS F 2563 and the cement mass was substituted by 20, 40, 60, 80%.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.11a
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• pp.150-151
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• 2021

This study aims to achieve an enhancement in the quality of high strength concrete through a reduction in autogenous shrinkage by supplying the moisture needed for hydration through recycled aggregates that retain high amounts of moisture. The result showed that, moisture supply increased with the higher replacement rate, autogenous shrinkage dropped by up to 45 percent.

• Journal of the Korea Concrete Institute
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• v.26 no.3
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• pp.277-285
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• 2014

The purpose of this study is to investigate experimentally the variation factors range having influence on the rheological properties of the combined self-compacting concrete according to materials quality, weighting error and site conditions. Two types cement (blast-furnace slag cement and belite cement), lime stone powder as binder and the optimum mix proportions in the preceded study are selected for this study. Also, variations for sensitivity test are as followings; (1) Concrete temperature 3 cases (2) Surface moisture of sand 5cases (3) Fineness modulus of sand 5cases (4) Specific surface of lime stone powder 3cases (5) Dosage of chemical admixture 5cases. Slump flow ($650{\pm}50mm$), 500 mm reaching time (($7{\pm}3sec$), V-type flowing time ($15{\pm}5sec$) and U-box height (min. 300 mm) are tested for sensitivity. As test results, the variations range for quality control are as followings. (1) Concrete temperature; $10{\sim}20^{\circ}C$(below $30^{\circ}C$) (2) Surface moisture of sand; $base{\pm}0.6%$ (3) Fineness modulus of sand; $2.6{\pm}0.2$ (4) Dosage of chemical admixture; $base{\pm}0.2%$ (5) Specific surface of lime stone powder $6000cm^2/g$. Compared with two types cement including based belite cement (binary type) and based slag cement (ternary type), the combined self-compacting concrete used belite cement type is most stable in the quality control because of high contents for lime stone powder and $C_2S$. It is to propose a control scheme of the combined self-compacting concrete in the actual construction work.

• Journal of the Korea Concrete Institute
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• v.21 no.1
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• pp.29-35
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• 2009

Recently, the press and institute recognized fly ash as it had excellent performance. Its research and applications are on the rise largely as a substitute for cement. On the contrary, it is in a situation that the regulation of high fineness fly ash remains at a low level. As for the fly ash in $3,000{\sim}4,500\;cm^2/g$ class fineness regulated in KS L 5405, it is used by substituting it around the unit weight of cement 20%. Accordingly, the regulation in upper classification is in a situation of being insufficient. Therefore, this study aimed to establish 4000, 6000, and 8000 class of fineness of fly ash and three levels of substitute like 15%, 30%, and 45% in order to analyze the substitute and effect of water-binder ratio for fly ash that affected the properties of ternary system concrete. As a result of experiment by planning water-binder ratio for two levels like 40% and 50%, the more replacement ratio and fineness of fly ash increased in the performance not hardened, the more the fluidity increased. This study has found out that the air content decreased, and that there was setting acceleration and it decreased the heat of hydration. In addition, as for the strength properties in a state of performance hardened concrete, the more the replacement ratio and the ratio of water-binding materials increased, the more it had a tendency of being decreased.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10a
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• pp.567-570
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• 2000

This study is designed to manufacture the continuous foamed concrete and the sound absorption characteristics investigation due to continuous voids ratio. According to the results of experiment, it was shown that continuous voids of the foamed concrete has the influence of the amount used of foaming agent, the viscosity and flowability of cement paste, and also is shaped by cohesive power of bubbles. Also the sound absorption ratio of the foamed concrete is subject to increase as the density becomes low by raising the continuous voids ratio. The cement paste with low water-cement ratio and high cement fineness are very effective to prevent weak strength of formed concrete caused by the increase of the porosity.

• Computers and Concrete
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• v.8 no.5
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• pp.583-595
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• 2011

This paper studied the cement efficiency factor (k factor) of high calcium Class F fly ash. This k factor represents a unit of fly ash with efficiency equivalent to k unit of cement. The high calcium Class F fly ash was used to replace cement in concrete. The modified Bolomey's law with linear relationship was used for the analysis of the result of compressive strength, cement to water ratio (c/w) and fly ash to water ratio (f/w) by using the multi-linear regression to determine the k factor and other constants in the equations. The results of analysis were compared with the results from other researcher and showed that the k factor of high calcium Class F fly ash depends on the fineness of fly ash, replacement level and curing age. While the amount of CaO content in Class F fly ash not evident. Furthermore, necessary criteria and variables for the determination of the k factor including the use of the k factor in concrete mix design containing fly ash were proposed.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.3
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• pp.313-319
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• 2017

In general, various factors such as grain size, chemical composition, amorphous amount, amorphous Si and Al content of fly ash affect the reaction with cement. In this study, we investigate the effect of fly ash particle characteristics on compressive strength. The standard sand was pulverized to a particle size similar to that of fly ash and the compressive strength was measured by blending with the cement as in fly. Using the measured compressive strength results, strength enhancement by cement hydration reaction and strength enhancement by particle filling effect were confirmed. Strength increment by pozzolanic reaction of fly ash was calculated by using the compressive strength results of mortar substituted with standard powder. As a result of comparison between compressive strengths and the particle characteristics of fly ash, the blaine showed a weak correlation with the compressive strength and the PI(Pozzolanic Index) showed good correlation with the 10% penetration diameter(D10) and the 50% Respectively. Therefore, it is expected that PI will be a good means to evaluate the fly ash characteristics together with the chemical characteristics of fly ash.

• Magazine of the Korea Concrete Institute
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• v.8 no.3
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• pp.167-175
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• 1996

Recently, the mortar crack on floor is very serious in construction field, e.g. the crack due to plastic shrinkage and the crack due to drying shrinkage. To prevent this kind of crack, optimum mix proportions not only satisfying the required workability but also minimizing the unit water content were selected. And the expansion admixtures were used to compensate shrmkage of mortar. The water /cement ratio used in construction field is about 64% by the investigation. Even if the water /cement ratio of mortar is reduced, floor mortar is still able to have the required workability by the appropriate use of the fine aggregate with high fineness mo'dulus and superplastizer. The equations hetween mortar flow and water /cement ratio, sand /cement ratio, fineness modulus of fine aggregate were proposed in this study. And the proposed equation may provide available mix proportions of floor mortar.