• KCI Concrete Journal
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• v.11 no.3
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• pp.19-28
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• 1999

This study treated self-compacting high Performance concrete as two Phase materials of Paste and aggregates and examined the effect of powder and aggregates on self-compacting high performance, since fluidity and segregation resistance of fresh concrete are changed mainly by paste. To improve the fluidity and self-compactibility of concrete, optimum powder ratio of self-compacting high performance concrete using fly ash and blast-furnace slag as powders were calculated. This study was also designed to provide basic materials for suitable design of mix proportion by evaluating fluidity and compactibility by various volume ratios of fine aggregates, paste, and aggregates. As a result, the more fly ash was replaced, the more confined water ratio was reduced because of higher fluidity. The smallest confined water ratio was determined when 15% blast-furnace slag was replaced. The lowest confined water ratio was acquired when 20% fly ash and 15% blast-furnace slag were replaced together. The optimum fine aggregates ratio with the best compactibility was the fine aggregate ratio with the lowest percentage of void in mixing coarse aggregate and fine aggregate In mixing the high performance concrete. Self-compacting high performance concrete with desirable compactibility required more than minimum of unit volume weight. If the unit volume weight used was less than the minimum, concrete had seriously reduced compactibility.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.11a
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• pp.46-47
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• 2018

High performance concrete with low water-to-cement ratio has been widely used with increased demand of high rising buildings and huge scaled structures. Additionally, for high performance concrete, various SCMs are replaced to improve its performance from fresh state to hardened state. With the drawback of increased viscosity of the concrete mixture for high performance concrete, low-viscosity typed high range water reducer is the relatively new admixture. Therefore, as a goal of the research, under using various SCMs with wide range of content, the performance of low-viscosity typed high range water reducer was evaluated. Especially, in this research, the influence of low-viscosity typed high range water reducer on rheological properties including plastic viscosity and yield stress were assessed. As a result of the research, it is expected to provide a fundamental information of low -viscosity typed high ranged water reducer on high performance concrete with various conditions of SCMs.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2004.05a
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• pp.1-4
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• 2004

In this paper. applicability of high early strength type AE water reducing agent(HESAEWA) developed by the authors is discussed by applying Mock-up test. For fresh concrete properties, concrete using existing AE water reducing agent(EAEWRA) and HESAEW A meets the target slump and air content at jobsite. Setting time of concrete using HESAEWA is shorter than that using EAEWRA. Remarkable variance of bleeding and settlement is not observed with type of AE water reducing agent. For hardened concrete properties, use of HESAEW A results in higher strength development compared with that of EAEWRA at standard curing and in field curing condition. Reaching time to accomplish 5MPa of compressive strength. which is possible to remove side form. is taken using HESAEWA earlier than that of EAEWRA by 1day. Therefore, it is confirmed that use of HESAEWA can meet the requirements of general quality of concrete and achieve high early strength development as well as has a desirable field applicability.

• Journal of Korean Tunnelling and Underground Space Association
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• v.17 no.3
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• pp.283-293
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• 2015

In order to evaluate corrosion resistance of steel fiber-reinforced concrete, accelerated chloride migration and surface resistivity tests were conducted. In addition air content of fresh concrete, compressive strength and water absorption were measured for investigating fundamental characteristics of concrete. Two different water-cement ratios(0.44, 0.5) and three steel fiber contents(0.25%, 0.5%, 1%) were considered as variables. Note that all specimens cast with same compaction work. As a results, corrosion resistance decreased as steel fiber contents increased regardless of water-cement ratio when the concrete was compacted with same amount of work done. However, for concrete with same steel fiber content, the lower water-cement ratio showed the better corrosion resistance. It is found that enhancement of fluidity and enough compaction should be done for corrosion resistance of SFRC.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.743-746
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• 2004

This research investigates experimentally an effect on the properties of the high flowing concrete according to variations of concrete materials and site conditions. Variations of sensitivity test are selected items as followings; (1)Concrete temperature, (2)Unit water(Surface moisture of fine aggregate), (3)Fineness modulus of fine aggregate, (4)Addition ratio of high-range water reducing agent. And fresh conditions of the high flowing concrete should be satisfied with required range including slump flow$(65{\pm}5cm)$, 50cm reaching time of slump flow$(4\~10sec)$, V-box flowing time$(10\~20sec)$, U-box height(min.300mm) and air content$(4{\pm}1\%)$. As results of sensitivity test, material variations and site conditions should be satisfied with the range as followings; (1)Concrete temperature is $10\~20^{\circ}C$ (below $30^{\circ}C$), (2)Surface moisture of fine aggregate is within ${\pm}0.6\%$, (3)Fineness modulus of fine aggregate is $2.6{\pm}0.2$ and (4)addition ratio of high range water reducing agent is within $1\%$ considered flow-ability, self-compaction and segregation resistance of the high flowing concrete.

• Advances in concrete construction
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• v.7 no.2
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• pp.97-105
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• 2019

In this paper, the workability and static stability were evaluated using a proposed test method. Workability and static stability represent a key property of self-compacting concrete (SCC) in fresh state. A number of standardized test methods were developed to assess these properties. However, no accelerated test method reliably predicts both workability and static stability of SCC. In the present work, a modified K-slump test method was developed to evaluate workability and static stability of SCC. In order to take implicit mixture variations of SCC constituents that can affect fresh SCC properties, a central composite design was adopted to highlight the effect of gravel to sand ratio (G/S), gravel 3/8 to gravel 8/15 ratio (G1/G2), water to cement ratio (W/C), marble powder to cement ratio (MP/C) and superplasticizer content (SP) on workability measured with slump and flow time (T50) tests and static stability measured with sieve stability test (Pi), segregation test index (SSI), Penetration test (Pd) and the proposed K-slump test (Km). The obtained results show that G/S ratio close to 1 and G1/G2 ratio close to 60% can be considered as optimal values to achieve a good workability while ensuring a sufficient static stability of SCC. Acceptable relationships were obtained between Slump flow, Pi, Pd and Km. Results show that the proposed K-slump test allow to assess both workability and static stability of fresh SCC mixtures.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.318-321
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• 2003

Steel slag is produced during steel making process. Compared with the blast furnace slag, converter slag has the expansibility due to the reaction with water and free CaO. Therefore it is specified in Standard Specification for Concrete in Korea that steel slag aggregate must not be used in concrete. In this study, atomized steel slag aggregate is conducted from converter slag by the atomizing method. Atomized steel slag and conventional converter slag are same in its composite by nature in the converter but compounds of the composite become different because of different method of slag treatment. Especially atomized steel slag aggregate overcomes expansibility that is the weak point for usage. It is researched whether it has the possibility, suitability for fine aggregate in concrete. Slump and air content are measured in fresh concrete, compressive and bending strength in hardened concrete. These is compared with control concrete with washed sand.

• Journal of the Korea Concrete Institute
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• v.12 no.5
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• pp.93-99
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• 2000

The physical properties of freshly mixed steel fiber reinforced recycled concrete(SFRRC) were_investigated. Physical state and quality of fresh concrete were monitored batch by batch. the properties of freshly mixed SFRRC were determined in terms of slump, air content, superplasticizer, and bleeding ratio. Concrete mixtures were produced for three kinds of aggregate proportions. So, the experimental variables are various aggregate proportions, steel fiber contents(0, 0.5, 1.0, 1.5%) and steel length(30, 50, 60mm). From experimental results, optimum s/a by various experimental variables, variations of the slump by the air contents, and optimum superplasticizer to decrease unit water were presented.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10a
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• pp.439-444
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• 2000

The purpose of this study is to investigate the possibility of Garnet powder as admixture of high strength concrete. The experiment condition is unit water content 160kg/㎥, W/B=30, 35%, S/A=40, 42, 44% and the cement was replaced with Garnet powder to 0, 10% of cement weight on making specimens. The mechanical properties of the fresh and hardened concrete were given as follows. As the time elapsed, the slump loss of 10% replaced concrete was considerably lower than that of 0% replaced concrete. In compressive strength, the 10% replacement case was nearly the same or somewhat high.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.497-500
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• 2005

This study was performed to evaluate the characteristics which are slump, air content and time of set in fresh concrete and compressive strength of hardened concrete containing slag powder and fly-ash. Replacement rate of FA is fixed on 10$\%$ and replacement rate of slag powder are 0$\%$, 20$\%$ and 30$\%$. Also AE water-reducing agents(standard type, accelerating type) are used. The results were as follows. (1)Slump flow of concrete using AE water-reducing agents is similar. Flowability is incresed when replacement rate of slag powder is increased due to slag powder's ball bearing reaction.(2)Time of set of concrete using accelerating type agent is more faster than that of concrete using standard type agent because of ettringite generation that promote setting.(3)Early strength of three-component concrete using accelerating type agent is higher than that using standard type agent. Therefore cumulative pore is reduced due to ettringite