• International Journal of Highway Engineering
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• v.7 no.3 s.25
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• pp.31-42
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• 2005

This study evaluates the physical mechanical properties, durability and sound absorbtion of porous concrete for pavement according to content of silica fume and steel fiber to elicit the presentation of data and the way to enhance its function for the practical field application of porous concrete as a material of pavement. The results of the test indicate that in every condition, the void ratio and the coefficient of water permeability of porous concrete for pavement satisfy both the domestic standards and proposition values. Among the properties of strength, the compressive strength satisfies the standards in the specification of Korea National Housing Corporation as for every factor of mixture but in the case of the flexural strength, more than 0.6vol.% of steel fiber satisfied the Japan Concrete Institute proposition values. The mixture of silica fume and steel fiber presents the excellent intensity, though. The case when silica fume and steel fiber are used simultaneously presents the strongest durability because the durability shows the similar tendency to the dynamic characteristics. The case when 10wt.% of silica fume and 0.6vol.% of steel fiber are used at the same time shows that the loss rate of mass by Cantabro test became 27% better and freeze-thaw resistance became 60% better. As for the characteristics of sound absorption of porous concrete for pavement, Noise Reduction Coefficient is 0.48 to prove that it possesses almost 50% sound absorption.

• Journal of the Korea Concrete Institute
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• v.23 no.1
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• pp.99-107
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• 2011

This study is to performed to find the optimum mix proportion of the high strength and self compacting concrete for the above-ground LNG storage tank construction and field application. If LNG storage tank wall thicknesscan be reduced, the construction cost and quality can be improved by using self-compacting high strength concrete with compressive strength 60~80 MPa. For this purpose, low heat cement (Type IV) and class F fly ash are used in concrete mix to control hydration heat, flowability, and viscosity. Mix design variables of unit water, fly ash replacement ratio, water-binder ratio, and fine aggregate ratio are selected and tested for material properties and manufacturing cost of the concrete. Also, fly ash replacement ratio is considered using confined water ratio test. The test results showed that the optimum mix proportion of the self-compacting high strength concrete characteristics are as follows. 1) In case of the concrete with specified compressive strength of 60 MPa, the optimum mix proportion is fly ash replacement ratio of 20% and water- binder ratio of 27~30%. 2) In case of the concrete with the strength of 80 MPa, the optimum mix proportion is fly ash replacement ratio of 10% and water-binder ratio 25%. But unit water and fine aggregate ratio are 165 $kg/m^3$ and $51{\pm}2%$, respectively, regardless of the traget concrete compressive strength range. Also, test results showed that concrete manufacturing cost of 60 MPa and 80 MPa concrete require additional costs of 14~22% and 33%, respectively, compared to the manufacturing cost of 40 MPa concrete. Therefore, application of the self-compacting high strength concrete has proven to be economical in the perspective of the material cost, quality control, and site management.

• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.2
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• pp.97-106
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• 2009

self-loading, various problems related to construction can be solved as well as the save of construction cost. Thus, this study has an aim of applying foam concrete to structural purpose by adding bottom ash as a reinforcing material like fine aggregate, in contrast to conventional non-structural usage such as soundproofing or insulating materials. In addition, it was evaluated in terms of unit volume weight, flow value, air void, water absorption and dosage of foam agent wether replacement of cement by granulated blast furnace slag or fly-ash has an effect on the material characteristics of foam concrete. As results of experiments, it can be found that the increase of fine aggregate ratio, that is to say, the increase of bottom ash results in the increase of unit volume weight, while decreasing air void and flow value. But, appropriate addition of bottom ash to foam concrete makes it easy to control a homogeneous and uniform quality in foam concrete due to less sensitive to bubbles. As the replacement ratio of mineral admixtures such as granulated blast furnace slag and fly-ash increases, as unit volume weight tends to decrease. In the meanwhile, serious effects were shown on fluidity of foam concrete when more than limit of replacement ratio was applied.

• Journal of Korean Tunnelling and Underground Space Association
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• v.24 no.6
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• pp.599-615
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• 2022

In order to excavate underground tunnel most safely such as Han river, the slurry shield TBM method is applied to cope with face of high water pressure for many metro projects. In downtown subway project most of excavated soil is discharged externally whereas in road construction excavated soil is used as filling materials so it becomes important factor for success of the project. After excavated soil, weathered rock and soft rock are discharged with bentonite through discharge pipe to slurry treatment plant then those soils are separated in separation plant according to those size. Fine grained soil has been discarded together with filter cake but it is not toxic and can be mixed with coarse aggregate in proper ratio so this study is performed to find use of qualified filling material to meet quality standard. Therefore, in this study, legal standards and quality standards for the utilization of excavated soil of the slurry shield TBM method were examined and test was conducted to derive recycling way for filter cake and aggregate. And a plan for using it as a filling material for road construction was derived. Because bentonite is a clay composed of montmorillonite, and the excavated soil in the tunnel is also non-toxic, disposal of this material can waste social cost so it is expected to be helpful in the underground space development project that carries out the TBM project by recycling it as a valuable resource.