• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.4_1
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• pp.33-41
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• 1992

For the purpose of improving the strength of Concrete, Silica Fume which has $SiO_2$ content of 90% and average particle diameter of $0.2{\mu}m$ was substituted to some extent as a cementious material of concrete. By means of using high range water reducing admixture and reducing water-cementions material ratio, the high strength mortar and concrete which have compressive strength of $865kg/cm^2$, $725kg/cm^2$, respectively were acquired. But the fact that the slump loss according to elapsed time was high and the tensile strength and elastic modulus were not improved sufficiently was the problem to be solved.

• Journal of the Korea Institute of Building Construction
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• v.14 no.4
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• pp.322-328
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• 2014

In this study, revelation performance of concrete at early age according to types of cement, water reducing ratio of high performance superplasticizer and mixing of accelerator for early hydration was examined aiming for reduction of construction period of framework through securing strength at early age of concrete. It was observed that strength at early age, 5MPa in 12hours, 14MPa in 18hours, is secured by early strength improvement type cement and using promotion admixture for early hydration which are Sodium persulfate, Potassium hydroxide. Therefore cost reduction is expected to be possible in construction site by reducing construction period of frame work.

• Journal of the Korean GEO-environmental Society
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• v.24 no.6
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• pp.13-20
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• 2023

This paper is aimed to evaluate the mechanical properties and durability of high-flowable retaining wall material (RWM) with different levels of steel fiber (SF) content. To produce the specimens of RWM, some chemical agents such as superplasticizer (SP), air-entrained agent (AEA) and viscosity modifying agent (VMA) were added in the fresh RWM. The compressive and split tensile strength measurements were performed on the hardened RWM specimens at the predetermined periods. Additionally, surface electric resistivity and absorption tests according to ASTM standards were carried out to examine mechanical properties of RWM mixes. The durable performances such as chloride ions penetrability and freezing-thawing resistance of RWM mixes were experimentally investigated. As resutls, it was found that the performance of RWM mix with SF were much better than that without SF, especially at the 2% addition of SF. Thus, it is noted that the proper addition of SF in the RWM mix may have a beneficial effect to improve mechanical properties and durability of RWM mixes.

• Journal of the Korean GEO-environmental Society
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• v.23 no.11
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• pp.5-11
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• 2022

The objective of this study is to evaluate the mechanical properties of high-flowable retaining wall material (RWM) incorporated with ground granulated blast-furnace slag (SG) and steel fiber (SF) based on a comparison with those of ordinary portland cement (OPC). To produce the specimens of RWM, some chemical agents such as superplasticizer (SP), air-entrained agent (AEA) and viscosity modifying agent (VMA) are added in the fresh RWM. The compressive, split tensile and flexural strength measurements were performed on the hardened RWM specimens. Additionally, surface electric resistivity and absorption tests according to ASTM standards were carried out at predetermined periods after water curing. It was found that the mechanical properties of slag cement concrete (SGC) RWM mix are better than those ordinary portland cement concrete (OPC) RWM mix. The effect of SF is remarkable to improve the mechanical properties of RWM mixes. It is noted that the usage of SG shows a beneficial effect to resist water penetration as well as long-term strength development of RWM mixes.

• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.4
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• pp.105-110
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• 2009

It's important to study about suitable substitutional material of expensive silica fume because it used widely for silica fume as a high-strength mortar binding agent. The main purpose of this study is to check which is the most efficient binder for the expensive silica fume's alternative material. And this study also present basic data about to make high-strength mortar when we use alternative material instead of silica fume through research outcome. Also writers analzed flow properties respectively, so it was founded out the substitutional goods fare like meta-kaolin, HMBA which are less expensive than silica fume because they are in domestic enough.

• Proceedings of the Korea Concrete Institute Conference
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• 1995.04a
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• pp.142-147
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• 1995

In this study, styrene-maleic anhydride copolymer (SMA) was synthesized from styrene and maleic anhydride and further reacted with sulfuric acid to obtain water-soluble SMA and the flow and strength tests of cement mortar mixed with copolymers were carried out to evaluate the capability of copolymers as high range water reducer for the concrete. It was found from flow experiment that the fluidity of cement mortar mixed with sulfonated SMA (SSMA) was larger than that miced with aminophenol-substituted SSMA (SmSMA). The decreasing rate of the flow of cement mortar mixed with SSMA and SmSMA was decreasing rate of the flow of cement mortar mixed with SSMA and SmSMA was significantly lower than that mixed with naphthalene condensate (NSC). The compressive strength of the hardened cement mortars containing 0.5% copolymers after 28 days curing was examined. The compressive strength of hardened cement mortar containing SSMA and SmSMA was increased up to 32% and 13%, respectively, when compared to the plain. As the results, the copolymers (SSMA and SmSMA) used in this study are greatly expected as a good high range water reducers for the concrete.

• Journal of the Korea institute for structural maintenance and inspection
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• v.8 no.4
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• pp.195-202
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• 2004

In this study, it was founded to make the optimal mixture for producing concrete which is self-compacting, yet, and generates low heat of hydration by using flyash, blast furnace slags and limestone powders as binders in addition to cement while using super-plasticizers and viscosity agents as admixture agents. The structural behaviors of the concrete produced with the selected mixture were compared with those of the concrete currently using for construction of nuclear power plants. The study shows that the blended high fluidity concrete including limestone is better in workability and durability than the concrete currently in use for nuclear power plants.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.741-744
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• 2008

There are two ways to reduce cement content for a given quality level(strength, workability etc.) in concrete. First, reducing the required paste volume by varying the shape or the grading of aggregates. Secondly, holding the paste volume constant while replacing cement volume with mineral admixtures or mineral fillers. And It will also be proved that the required minimum paste volume is independent of the paste composition, provided the paste composition is in a reasonable range. In this study, therefore, we have an object to determine the required minimum paste volume for a given workability level. For this purpose, we tried the following experiments: vary the paste volume for the three different grading of aggregates and determine the minimum paste volume to achieve a certain level of workability with high-range water reducing admixture.

• Journal of the Korean Ceramic Society
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• v.47 no.5
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• pp.387-393
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• 2010

To improve concrete quality one of the most widely used chemical admixtures is polycarboxylate type superplasticizer. Unlike lignosulfonate and naphthalene-sulfonate, it has high dispersion property and excellent sustainable dispersion property for cement and concrete. Thus, polycarboxylate type superplasticizer has been widely used as a high-performance water reducing admixture together with silica fume in high-performance concrete and other applications for the dispersion of high-strength concrete over 100 MPa. However, even though there have been many studied on the dispersion of concrete by the structure of polycarboxylate type superplasticizer, there have a few studied that clarified the relationships between its rheological properties and microstructure properties in the early hydration behavior of ordinary portland cement. To investigate the correlations between the rheological properties and microstructure of cementitious materials with polycarboxylate type superplasticizer, this study experimented on the rheology, pore structure, heat evolution, and consistency in early hydration as well as on the compressive strength by early dispersion characteristics.

• Magazine of the Korea Concrete Institute
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• v.7 no.2
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• pp.155-164
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• 1995

This study was performed to get high strength of the precase concrete adopting a steam curing by using a gypsum-admixture for the high strength concrete. The superplasticizer was used to compensate low slump of base concrete keeping its slump up about $6{\pm}1cm$. To examine the property for strength revelation of concrete using admixtures for a high strength concrete, steam and standard curing were compared each other. Test results were shown that admixtures for high strength concrete were more effective in steam curing than standard curing. On the condition that the unit cement content is about $530{\sim}600kg/m^3$, the compressive strength of concrete replacing by 10% of the admixture was obtained over $65Okgf/cm^2$, which was increased as 1.3 times as that for the nonreplacement. When the admixture was replaced to 15-30%, the compressive strengh was obtained over $700kgf/cm^2$ which was increased as 1.4 - 1.5 times. Therefore, the admixture for high strength concrete, being effective in steam curing, was more efficient to get a high strength concrete using only steam curing instead of an autoclave curing for the secondary products of cement.