• Restorative Dentistry and Endodontics
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• v.34 no.2
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• pp.130-136
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• 2009

The aim of this study was to develop a method for measuring the slumping resistance of flowable resin composites and to evaluate the efficacy using rheological methodology. Five commercial flowable composites (Aelitefil flow:AF, Filtek flow:FF, DenFil flow:DF, Tetric flow:TF and Revolution:RV) were used. Same volume of composites in a syringe was extruded on a glass slide using a custom-made loading device. The resin composites were allowed to slump for 10 seconds at $25^{\circ}C$ and light cured. The aspect ratio (height/diameter) of cone or dome shaped specimen was measured for estimating the slumping tendency of composites. The complex viscosity of each composite was measured by a dynamic oscillatory shear test as a function of angular frequency using a rheometer. To compare the slumping tendency of composites, one way-ANOVA and Turkey's post hoc test was performed for the aspect ratio at 95% confidence level. Regression analysis was performed to investigate the relationship between the complex viscosity and the aspect ratio. The results were as follows. 1. Slumping tendency based on the aspect ratio varied among the five materials (AF

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.5
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• pp.106-114
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• 2006

This paper investigates the fundamental properties and shrinkage characteristics of low shrinkage high performance concrete(LSHPC), using mock-up specimens. According to the test results, the most suitable mix proportions of LSHPC need a higher dosage of SP agent and AE agent, in order to obtain the target of slump flow and air content. This is due to reduce fluidity and air content respectively. It also presented earlier setting time than control concrete by 6 hours and exhibited compressive strength of 60MPa at age 28 days. Autogenous shrinkage of LSHPC was the half of the value of control concrete. Drying shrinkage of center section of LSHPC showed similar tendency with autogenous shrinkage, because of no internal moisture movement, while surface section had larger drying shrinkage. The specimen with embedded reinforcing bar had smaller deformation owing to confinement of reinforcing bar.

• Magazine of the Korea Concrete Institute
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• v.8 no.3
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• pp.135-146
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• 1996

In this study, the properties of super flowing concrete containing fly ash were experimentally investigated and compared with those of ordinary concrete. Tests were carried out on five types of super flowing concrete mixes containing fly ash and three types of ordinary concrete mixes without fly ash. Flow test, 0-funnel test, box test, L type test and slump test were carried out to obtain the properties for flowability and workability of fresh concrete. The mechanical properties of hardened concrete were also investigated in terms of compressive strength, splitting tensile strength, modulus of elasticity, creep and drying shrinkage. In fresh concrete, it was found that super flowing concrete had excellent workability and flowability compared with ordinary concrete, and had self-compactable performance. Super flowing concrete *also had good mechanical properties at both early and late ages with compressive strength reaching as high as 40 MPa at 28 days. The creep deformation of super flowing concrete investigated was relatively lower than that of ordinary concrete, but drying shrinkage was much higher.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.405-408
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• 2008

This study, as mock-up test for applying Polylon Fiber engineering method to the field, analyzed the fundamental characteristics and the fireproof characteristics of high strength concrete mixed with Polylon Fiber 0.05% and the results are summarized as followings. From the characteristic of the fresh concrete, both slump flow and air content were appeared to satisfy target range. And from the characteristic of hardened concrete, all compressive strengths according to the curing conditions were appeared to satisfy design standard strength of 60 MPa. From the fireproof characteristic, small scaling and spalling phenomenon were partially appeared on the surface part of specimens, but generally the excellent fireproof capacities were appeared. From the characteristic of temperature hysteresis, the highest temperature and the average temperature of reinforcing part after fire-resistant test for 3 hours were $531^{\circ}C$ and $405{\circ}C$, respectively and then satisfied fireproof standard of the Ministry of Land Transportation and Maritime Affairs.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.4
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• pp.97-103
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• 2017

As the shortage of concrete aggregates is intensifying, the development of alternative resources is urgent. As the amount of steel slag increases year by year, attempts are being made to recycle slag into high-value-added products in order to develop an efficient resource recycling industry based on slag and to obtain economic benefits. However, the use of electric arc furnace oxidizing slag (EOS) as building materials is practically limited because it contains unstable materials. In this paper, physical properties of concrete were evaluated by using electric arc furnace slag aggregate. It has been produced with two levels of general strength area W / C 45% and high strength area W / C 30%. Fresh concrete has been tested in air content, flow and slump, unit weight. The properties of the cured concrete were investigated by compressive strength, bending strength and unit volume weight. As a result of this study, strength of concrete increased with increasing EOS aggregate mixture.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2005.11a
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• pp.183-186
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• 2005

This study investigates material properties of epoxy resins and reinforced materials for adhesion repairing-reinforced of RC construction. According to the test. elasticity modulus of mortar indicated 16-26(GPa) and that of concrete was 18-27(GPa). It became decreased as mixture proportion, W/C and fluidity of both mortar and concrete increased In addition the elasticity modulus of epoxy resins exhibited around 45.3-220(GPa), while that of steel plate and Carbon Bar indicated 338(GPa) and 34.1 (GPa), respectively. It is obvious that individual materials had big different value of elasticity modulus. Meanwhile, thermal expansion coefficients of mortar was 10-13 ${\mu}\varepsilon$ /$^{\circ}C$ and that of concrete was 9-11 $\mu \varepsilon$ /$^{\circ}C$ The increase of mixture Voportion and W/C resulted in lower value of thermal expansion coefficients and the increase of flow and slump exhibited slightly higher value. The epoxy resin indicated 41-54 ${\mu}\varepsilon$ /$^{\circ}C$ which is 4-5 times larger value than concrete and steel plate and Carbon Bar was 11.93 ${\mu}\varepsilon$ /$^{\circ}C$ and -1.68 ${\mu}\varepsilon$ /$^{\circ}C$ respectively. Hence, the adhesion strength of the epoxy resins should be considered before it is used in field condition, due to different thermal expansion coefficient of each material.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2007.04a
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• pp.33-36
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• 2007

In order to select the optimum mix for the required fluidity and strength of mass concrete which is applied to transfer girder and to choose the optimum curing method depending on circumstances through hydration heat analysis of mass concrete, this study examined slump flow, air content and elapsed variation (0, 30, 60, 90) in unhardened concrete properties and reviewed compressive strength characteristics in hardening properties. And hydration heat analysis results through simulation are as follows; 1) Fluidity changes of unhardened concrete showed no significant difference, and those of elapsed variation also showed no difference but a bit of tendency to increase in comparison with the initial properties. 2) The higher the water-binder ratio was, the lower the compressive strength properties were, and the higher the fly ash replacement rate was, the lower the compressive strength development was. 3) In case of $Fc=40N/mm^2$, the optimum mix was fly ash replacement rate of 15% from water-binder ratio of 33.0%. 4) Hydration heat analysis results showed that in case of bundle cast, concrete temperature profile characteristics around transfer girder was unfavorable, and in case of separate cast, constant curing for at least seven days guaranteed thermal cracking index of 1.2.

• Land and Housing Review
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• v.3 no.3
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• pp.287-297
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• 2012

To develop 80MPa-high strength concrete with ternary cement used in OPC, blast-furnance slag, and fly ash, mixing ratio of blast-furnace slag and fly ash was evaluated in material characteristics before and after hardening of the high strength concrete. According to the evaluated results of material characteristics before and after hardening of the high strength concrete, the flowability and long-term compressive strength increase up to 30% mixing ratio of blast-furnace slag and fly ash. Also, it is superior to characteristics of length change and neutralization due to the use of mineral admixture when compared in test sample mixed with OPC. The evaluated results show that material characteristics of the high strength concrete was the most outstanding performance at blast-furnace slag of 25% and fly ash of 15%. The result of this study will be useful for the development of high strength concrete as a substitute of costly silica fume in the near future.

• Journal of the Korea Concrete Institute
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• v.14 no.3
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• pp.409-419
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• 2002

Nowadays, antiwashout underwater concrete is widely used for constructing underwater concrete structures but they, especially placed in marine environment, can be easily attacked by chemical ions such as SO$\^$2-/$\_$4/ Cl$\^$-/ and Mg$\^$2＋/, so the quality and capability of concrete structures go down. In this paper, to solve and improve those matters, flyash and GGBFS(ground granulated blast furnace slag) were used as partial replacements for ordinary portland cement. As results of experiments for fundamental properties of antiwashout underwater concrete containing 10, 20, 30％ of flyash and 40, 50, 60 ％ of GGBFS respectively, setting time, air contents, suspended solids and pH value were satisfied with the "Standard Specification of Antiwashout Admixtures for Concrete" prescribed by KSCE, and also slump flow, efflux time and elevation of head were more improved than that of control concrete. From the compressive strength test, it was revealed that the antiwashout underwater concrete containing mineral admixtures(flyash and GGBFS) is more effective for long term compressive strength than control concrete. An attempt to know how durable when they are under chemical attack has also been done by immersing in chemical solutions that were x2 artificial seawater, 5 ％ sulphuric acid solution, 10％, sodium sulfate solution and 10％ calcium chloride solution. After immersion test for 91days, XRD analysis was carried out to investigate the reactants between cement hydrates and chemical ions and some crystalline such as gypsum ettringite and Fridel′s salt were confirmed.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.425-428
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• 2008

To use lightweight aggregate concrete with the structural material, it was need to evaluate property of mechanic and drying shrinkage and creep of the lightweight aggregate concrete, but these weren't. So the purpose of this study which it sees follows the mechanical property of the eco lightweight aggregate concrete according to the water binder ration in the high strength concrete. Eco lightweight aggregate was made with clay and crushed rock in this study. To make experiment, water binder ratio was divided 35% and 39%. And the fresh concrete properties were that slump flow was 500${\pm}$50mm, air contents was 2.0${\pm}$1.0%. It evaluated the hold a drying shrinkage and the creep the effect, it analyzed quality and reliability of the eco lightweight aggregate concrete.