• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.525-532
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• 2004

Among soft ground treatment methods with granular soil used in domestic, the sand compaction pile method has been utilized greatly, but, as a result of exhaustion of sand and increase of unit cost, a necessity of an alternative method is suggested. In this study, the static load tests for crushed-stone compaction piles which were constructed on test field were performed. Based on test results, stress concentration ratios between the crushed-stone compaction pile and the soft ground were investigated and estimated. The stress concentration ratio was the range of 1.7 to 3.0 and the higher it was the more replacement rate was increased.

• Computers and Concrete
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• v.25 no.3
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• pp.267-272
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• 2020

This paper investigates the effect of crumb rubber (CR) on compressive behaviour of crumb rubber concrete filled steel tube (CRCFST) stub columns. Therefore, experiments on 16 stub columns subjected to axial loading are carried out. The results show that the failure modes of CRCFST stub columns with different CR replacement ratios and CR size are similar, manifested the buckling of the outer steel tube. The axial bearing capacity and stiffness both decrease with an increase in CR replacement ratio, and with decreasing CR size.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.1193-1198
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• 2008

Shaking table tests were performed to investigate the response of liquefaction mitigation of rammed aggregate piers(RAP) on soft ground. The displacements of the soft ground reinforced by RAP under area replacement ratio 7, 14, 28% during seismic loading were measured. The result of tests showed that effects of liquefaction mitigation were affected various area replacement ratios and ground acceleration on RAP systems.

• Advances in concrete construction
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• v.12 no.5
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• pp.367-375
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• 2021

This study experimentally investigated the improvement of bond strength and durability of concrete containing high volume fly ash. Concrete mixtures made with 0%, 25% and 60% replacement of cement with class F fly ash were prepared. Water-binder ratios ranged from 0.28 to 0.72. The compressive, flexural and pullout bond strength, the resistance to chloride-ion penetration, and the water permeability of concrete were measured and presented. Test results indicate that except for the concretes at early ages, the mechanical properties, bond strength, and the durability-related chloride-ion permeability and water permeability of concrete containing high volume (60% cement replacement) fly ash were obviously superior to the concrete without fly ash at later ages of beyond 56 days. The enhanced bond strength for the high volume fly-ash concrete either with or without steel confinement is a significant finding which might be valuable for the structural application.

• Journal of the Mineralogical Society of Korea
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• v.17 no.3
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• pp.277-288
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• 2004

Alkali-silica reaction (ASR) is a chemical reaction between alkalies in cement and chemically unstable aggregates and causes expansion and cracking of concrete. In the Present study, we studied the effects of metakaolin, which is a newly introduced mineral admixture showing excellent pozzolainc reaction property, on the inhibition of ASR. We prepared mortar-bars of various replacement ratios of metakaolin and conducted alkali-silica reactivity test (ASTM C 1260), compressive strength test and flow test. We also carefully analyzed the mineralogical changes in hydrate cement paste by XRD qualitative analysis. The admixing of metakaolin caused quick pozzolanic reaction and hydration reaction that resulted in a rapid decrease in portlandite content of hydrated cement paste. The expansion by ASR was reduced effectively as metakaolin replaced cement greater than 15%. This resulted in that the amounts of available portlandite decreased to less than 10% in cement paste. It is considered that the inhibition of ASR expansion by admixing of metakaolin was resulted by the combined processes that the formation of deleterious alkali-calcium-silicate gel was inhibited and the penetration of alkali solution into concrete was retarded due to the formation of denser, more homogeneous cement paste caused by pozzolanic effect. Higher early strength (7 days) than normal concrete was developed when the replacement ratios of metakaolin were greater than 15%. And also, late strength (28 days) was far higher than normal concrete for the all the replacement ratios of metakaolin. The development patterns of mechanical strength for metakaolin admixed concretes reflect the rapid pozzolanic reaction and hydration properties of metakaolin.

• Applied Chemistry for Engineering
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• v.25 no.2
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• pp.181-187
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• 2014

In order to use the spherical atomizing reduction steel slag (ladle furnace slag, LFS) instead of the fine aggregate of polymer concrete composites, various specimens were prepared with various replacement ratios of atomizing reduction steel slag and the addition ratios of polymer binder. Physical properties of these specimens were investigated through the absorption test, the compressive strength test, the flexural strength test, the hot water resistance test, the pore analysis and the micro-structure using scanning electron microscope. Results showed that the compressive strength and flexural strength of specimens with 7.5% of polymer binders increased with the increase of replacement ratios of atomizing reduction steel slag, but those of the specimens with 8.0% or more of polymer binders showed a maximum strength at a certain replacement ratio due to the material segregation causing the increase of fluidity. By hot water resistance tests, the compressive strength, flexural strength, average pore diameter, and bulk density decreased but the total pore volume and pore diameter increased. It was concluded that the amount of polymer binders could be reduced by maximum 23.8%, because the workability of the polymer concrete was remarkably improved by using the atomizing reduction steel slag instead of fine aggregate. However, since the use of atomizing reduction steel slag decreased the resistance of the polymer concrete to hot water, further studies are required.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.10a
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• pp.217-222
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• 2002

The purposes of this study are to investigate the material characteristics and strength properties of concrete mixed with waste incinerated bottom ash(BA), and to evaluate the leaching of environmentally harmful heavy metals from the bottom ash itself and from hardened concrete mixed with bottom ash. For this purpose, two reference mixes with W/C ratios of 0.45 and 0.55 were used, and the replacement proportion of BA was varied with the ratios of 0%, 30%, 50%, 70%, and 100% by volume of fine aggregate in the reference mixes. The variation of compressive and splitting tensile strength, workability and unit weight of concrete were considered. Test results showed that the strengths, workability and unit weight decreased with increase in proportion of BA replaced. Leaching test results showed that there would be no environmentally harmful problem from using BA as the substitutes of fine aggregates in concrete.

• Computers and Concrete
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• v.14 no.3
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• pp.247-262
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• 2014

Partial replacement of Portland cement by slag can reduce the energy consumption and $CO_2$ emission therefore is beneficial to circular economy and sustainable development. Compressive strength is the most important engineering property of concrete. This paper presents a numerical procedure to predict the development of compressive strength of slag blended concrete. This numerical procedure starts with a kinetic hydration model for cement-slag blends by considering the production of calcium hydroxide in cement hydration and its consumption in slag reactions. Reaction degrees of cement slag are obtained as accompanied results from the hydration model. Gel-space ratio of hardening slag blended concrete is determined using reaction degrees of cement and slag, mixing proportions of concrete, and volume stoichiometries of cement hydration and slag reaction. Furthermore, the development of compressive strength is evaluated through Powers' gel-space ratio theory considering the contributions of cement hydration and slag reaction. The proposed model is verified through experimental data on concrete with different water-to-binder ratios and slag substitution ratios.

• International Journal of Concrete Structures and Materials
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• v.7 no.4
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• pp.295-301
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• 2013

This paper deals with the interfacial effects of silica fume (SF) and styrene-butadiene rubber (SBR) on compressive strength of concrete. Analyzing the compressive strength results of 32 concrete mixes performed over two water-binder ratios (0.35, 0.45), four percentages replacement of SF (0, 5, 7.5, and 10 %) and four percentages of SBR (0, 5, 10, and 15 %) were investigated. The results of the experiments were showed that in 5 % of SBR, compressive strength rises slightly, but when the polymer/binder materials ratio increases, compressive strength of concrete decreases. A mathematical model based on Abrams' law has been proposed for evaluation strength of SF-SBR concretes. The proposed model provides the opportunity to predict the compressive strength based on time of curing in water (t), and water, SF and SBR to binder materials ratios that they are shown with (w/b), (s) and (p).This understanding model might serve as useful guides for commixture concrete admixtures containing of SF and SBR. The accuracy of the proposed model is investigated. Good agreements between them are observed.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.10a
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• pp.17-22
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• 2002

Chloride ions have a tendency to penetrate into concrete and proceed the corrosion by depassivating rebar surface. Thus the deteriorated concrete is subject to experience severe degrading of durability under marine environment. Physical properties of mortar, such as, compressive strength and penetration depth of chloride ion were investigated. And to investigate the effect of containing SG, FA in mortar, the diffusion coefficient of chloride was measured through an electro - migration test. The diffusion coefficient of chloride was decreased with the increase of replacement ratio of SG compared with plain specimen.