• Structural Engineering and Mechanics
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• v.82 no.1
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• pp.93-105
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• 2022

The brittleness of concrete can be overcome by fiber reinforcement that controls the crack mechanisms of concrete. Corrosion-related durability issues can be prevented by synthetic fibers (SFs), while macro synthetic fibers have proven to be particularly effective to provide ductility and toughness after cracks. This experimental study has been performed to investigate the comparative flexural and mechanical behavior of four different macro-synthetic fiber-reinforced concretes (SFRCs). Two polyamide fibers (SF1 and SF2) with different aspect ratios and two different polypropylene fiber types (SF3 and SF4) were used in production of SFRCs. Four different SFRCs and reference concrete were compared for their influences on the toughness, compressive strength, elastic modulus, flexural strength, residual strength and splitting tensile strength. The outcomes of the study reveal that the flowability of reference mixture decreases after addition of SFs and the air voids of all SFRC mixtures increased with the addition of macro-synthetic fibers except SFRC2 mixture whose air content is the same as the reference mixture. The results also revealed that with the inclusion of SFs, 11.34% reduction in the cube compressive strength was noted for SFRC4 based on that of reference specimens and both reference concrete and SFRC exhibited nearly similar cylindrical compressive strength. Results illustrated that SFRC1 and SFRC4 mixtures consistently provide the highest and lowest flexural toughness values of 36.4 joule and 27.7 joule respectively. The toughness values of SFRC3 and SFRC4 are very near to each other.

• Resources Recycling
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• v.16 no.2 s.76
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• pp.17-22
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• 2007

The report of an investigation into the performance of mortar specimens made with recycled fine aggregate (RA) exposed to sodium sulfate solution for 360 days is presented in this paper. Mechanical properties of mortar specimens such as visual examination, compressive strength, expansion and mass loss were periodically monitored. From the test results, it was found that mortar specimens with higher replacement levels of Rh exhibited poor performance in sodium sulfate solution. However, compared to mortar specimens without RA, those with lower replacement levels of RA (up to 50% by mass) was more resistant to sulfate attack. Through the x-ray diffraction analysis, it was confirmed that the main products causing sulfate deterioration in RA mortar specimens were the formation of gypsum and thaumasite.

• Computers and Concrete
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• v.6 no.2
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• pp.155-165
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• 2009

Splitting tensile strength (STS) of high-performance concrete (HPC) is one of the important mechanical properties for structural design. This property is related to compressive strength (CS), water/binder (W/B) ratio and concrete age. This paper presents a clustering-based fuzzy model for the prediction of STS based on the CS and (W/B) at a fixed age (28 days). The data driven fuzzy model consists of three main steps: fuzzy clustering, inference system, and prediction. The system can be analyzed directly by the model from measured data. The performance evaluations showed that the fuzzy model is more accurate than the other prediction models concerned.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.409-410
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• 2009

The eco-cement concrete using fly-ash was produced for the improvement of the compressive strength of the eco-cement concrete under the long term age, and compressive strength test, drying shrinkage test, uniaxial restraint shrinkage cracking test, and bond test were carried out. In this study, the cracking resistance performance was investigated.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2017.05a
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• pp.120-121
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• 2017

Generally, slump of plain concrete slab is about 120~150mm and slump loss is easy to occur. So, water is added to concrete because this method is convenient for Placing. In order to solve this problem, performance evaluation of concrete using improvement type PC admixture was carried out. Target slump is 210mm and compressive strength is 18MPa. As a result, slump reference value was satisfied 60 minutes after placing and 7-day compressive strength was 21~25MPa.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.13-16
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• 2005

Nanoscale materials are of great interest due to their unique optical, electrical and magnetic properties. Due to the recent amazing achievements in nano technology, new materials were developed. But these nano technology is not apply to the construction part in spite of exellent properties of nano size material. The purpose of this study is to apply to nano technology into building materials. To develop the high performance concrete, nano cement particles is prepared by mechanical method. In the results of this study, the nano silica powder increase effect according to increase of the mixing amount, appeared that compressive strength increased but is limit in increment. For the production of high-strength concrete, nano silica powder was suitable the binder ratio from 20$\%$. And, the compressive strength of concrete are especially dependent on the curing temperature.

• Steel and Composite Structures
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• v.14 no.5
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• pp.473-491
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• 2013

The primary objectives of this paper are to describe the buckling patterns and to determine the squash load of steel plate-concrete (SC) walls. The major variables in this study were the width-thickness (B/t) ratio and yield strength of surface steel plates. Six SC walls were tested, and the results include the maximum strength, buckling pattern of steel plates, strength of headed studs, and behavior of headed studs. Based on the test results, the effects of the B/t ratio on the compressive strength are also discussed. The paper also presents recommended effective length coefficients and discusses the effects of varying the yield strength of the steel plate, and the effects of headed studs on the performance of SC structures based on the test results and analysis.

• Structural Engineering and Mechanics
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• v.82 no.2
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• pp.133-149
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• 2022

This study investigates the resistance of sustainable ultra-high performance concrete (UHPC) on steel reinforcement corrosion. For enhancing the sustainability of UHPC, concrete mixes were prepared with ordinary Portland cement main binder, and mixes with moderate to high percentages of blast furnace cement (CEM III), fly ash (FA), and slag cement as partial replacements of the full quantity of the used cement. Linear polarization resistance technique was employed to estimate the electrochemical behavior of the concrete specimens. Results showed that the compressive strength and the resistance of steel to corrosion in marine environments can be enhanced by improving the sustainability of UHPC through incorporation of CEM III, FA, and slag cement. FA replacement of up to 50% with the addition of 15% SF content produced better compressive strength and steel corrosion resistance than slag cement whether with the use of ordinary Portland cement or blast furnace cement as the main binder.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2022.11a
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• pp.65-66
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• 2022

In this study, the setting characteristics of the high range water reducing agent to minimize the retardation of UHPC were confirmed to minimize the setting time in the hardening of UHPC. As a result of the study, there was a slight change depending on the difference in the type of Superplasticizer, K > P > D = S > E in the order of condensation promotion, and E > S = D = K > P on the 28th day.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.11a
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• pp.149-150
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• 2023

This study proposes the most suitable strength prediction model equation for UHPC by calculating the apparent activation energy of UHPC according to the curing temperature and deriving the integrated temperature and compressive strength prediction equation. The results are summarized as follows. The apparent activation energy was calculated using the Arrhenius function, which was calculated as 21.09 KJ/mol. A model equation suitable for UHPC was calculated, and when the Flowman model equation was used, it was confirmed that it was suitable for the properties of UHPC using a condensation promoting super plasticizing agent.