• Journal of the Korea Concrete Institute
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• v.13 no.1
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• pp.54-61
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• 2001

As a part of the movement of natural resources conservation, there have been doing many recycling research works for obsolete aged tire, wasted plastic materials, etc. The purpose of this experimental study is to develop glass concrete by recycling wasted glasses as a cementitious constituent in concrete. First of all, the optimum replacement ratio of powdered waste glasses(PWG) can be determined through pilot compressive strength test on normal and high strength concrete cylinders, which have been made in various mix proportions by changing the replacement ratio of PWG. Then, further tests have been done to figure out mechanical properties of most desirable glass concrete with optimum replacement ratio of PWG, such as static modulus of elasticity, compressive and tensile strengths, flexural strength. On the other hand, the alkali-silica reactions by the mortar-bar method(KS F 2546) have been experimentally doing in various grain sizes of PWG, since the alkali in the cement has a tendency to react with the silica in the PWG. In can be confirmed from the test that glass concrete can have better workability than concrete with silica fume, and they are alike in compressive strength. It is concluded that wasted glasses can be used as pratical additives for economic and environmentally friendly concrete.

• Journal of the Korea Concrete Institute
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• v.18 no.6 s.96
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• pp.743-748
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• 2006

This paper presents results of an experimental study conducted to investigate the effect of volume fraction of fibers on the mechanical properties of a fiber-reinforced, lightweight aggregate concrete(FRLAC) that was produced without an autoclave process. The FRLAC enhanced the strength of lightweight, cellular concrete by adding polypropylene fibers and lightweight aggregates. To investigate the effect of volume fraction of fibers on the mechanical behavior of FRLAC and to determine the optimal volume fraction of fibers, a series of compression and flexural strength tests on FRLAC specimens with various fiber volume fractions(0%, 0.10%, 0.25%, 0.50%) were conducted. It was observed from the tests that a 0.25% volume fraction of fibers maximized the increase in the strength of FRLAC and the fibers controlled cracking in FRLAC.

• Resources Recycling
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• v.22 no.1
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• pp.20-28
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• 2013

Recently, as the registration of vehicles increases, the utilization of the waste tires is emerging as environmental issues. Crumb rubber reproduced by scrap tires has been reused up to 25% in the construction field. The purpose of this paper is to investigate the mechanical properties of sulfur-rubber concrete (SRC) and to suggest the optimum mix design in terms of the compressive strength. Specimens were prepared with various mixing parameters: amount of sulfur, rubber, and micro-fillers. Two casting processes were also mentioned; dry process and wet process. The results mainly showed that the compressive strength of SRC decreased with an increment of rubber content. However, adding micro-filler and adjusting sulfur contents could improve the compressive strength of SRC. Optimum values of sulfur and rubber content were selected by workability and compressive strength of SRC. SRC can be applied to road constructions where high strength of concrete is not concerned, to wall panels that require low unit weight, to construction of median in highways to resist high impact load, and in sound barriers to absorb sound waves.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.753-756
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• 2008

HPFRCC (High-Performance Fiber Reinforced Cementitious Composites), which is relatively more ductile and has the characteristic of high toughness with high fiber volume fractions, can be used in structures subjected to extreme loads and exposed to durability problems. In the case of using PVA(polyvinyl alcohol) fibers, it is noted by former studies that around 2% fiber volume fractions contributes to the most effective performance at HPFRCC. In this study, therefore, compressive and flexural tests were implemented to evaluate the compressive and flexural capacities of HPFRCC while the total fiber volume fractions was fixed at 2% and two different PVA fibers were used with variable fiber volume fractions to control the micro-crack and macro-crack with short and long fibers, respectively. Moreover, specimens reinforced with steel and PVA fiber simultaneously were also tested to estimate their behavior and finally find out the optimized mixture. In the result of these experiments, the specimen consists of 1.6% short fibers (REC 15) and 0.4% long fiber (RF4000) outperformed other specimens. When a little steel fibers added to the mixture with 2% PVA fibers, the flexural capacity was increased, however, when high steel fiber volume fractions applied, the flexural capacity was decreased.

• Resources Recycling
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• v.29 no.1
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• pp.43-52
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• 2020

The objectives of this study were to identify the optimal mix of foam concrete with the low-strength and high-flow for the repairing ground subsidence situation emergently by utilizing a large amount of industrial by-products and evaluate the possibility by applying it to the site. The factors of the experiment were the mixing ratio of mixing water and a foaming agent and the mixing ratio of foam over paste volume. The optimal mix identified by the experiment was applied to the field and basic properties were evaluated. The results of the experiment showed that the optimal mixing ratio of mixing water and the foaming agent was 10%. Moreover, when the mixing ratio of pre-foam over paste volume was 170%, it satisfied the target. However, to ensure stable quality when applying to the field, the foam mixing ratio was set 140% for the field application. The field application test of foam concrete with the low-strength and high-flow using an eco-friendly binder satisfied all target performances. Therefore, the possibility of using it as a mixture and construction method for a ground repair system is confirmed. However, there was a quality deviation between the upper part and the lower part due to the separation between foam and paste. Consequently, further studies are needed to improve it.

• Journal of the Korea Concrete Institute
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• v.18 no.3 s.93
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• pp.397-404
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• 2006

This paper investigates experimentally the effect of combined addition of expansive additive and shrinkage reducing agent(SRA) on setting time, compressive strength and drying shrinkage of concrete. An increase of EA and SRA content leads to a reduction in flowability, which causes the increase of superplasticizer dosage, while air content increases. For setting time, in spite of increased superplasticizer dosage, with the increase of EA and SRA, setting time shortens. This is due to the presence of alkali ion by SRA and the faster formation of ettringite. At dosage of 5.0% of EA, concrete has the highest compressive strength and above that dosage, compressive strength decreased. On the contrary, the increase of SRA dosage results in a decrease in compressive strength. Combined addition of EA of 5.0% and SRA of 1.0% shows a comparable strength with control concrete. For drying shrinkage, as expected, the increase of EA and SRA dosage leads to reduction of drying shrinkage markedly. Moreover, combined addition of EA and SRA has better drying shrinkage reduction effect than individual use of EA and SRA by as much as $5{\sim}16%$. Optimal combination of EA and SRA is fixed at 5.0% of EA and 0.5% of SRA based on the consideration of the effect of EA and SRA on fresh state, compressive strength and shrinkage of concrete.

• Journal of the Korea Institute of Building Construction
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• v.23 no.2
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• pp.133-142
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• 2023

In this study, the fire resistance capabilities of polypropylene fiber-reinforced polymer-modified cement mortar were assessed to guarantee the fire resistance fo this materials, commonly employed in the repair of concrete structures. Experimental outcomes revealed that an increased water and polymer content heightened the likelihood of spalling, while longer polypropylene fibers and elevated polymer concentrations proved more effective in mitigating spalling.

• Magazine of the Korea Concrete Institute
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• v.11 no.2
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• pp.115-125
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• 1999

The purpose of this experimental research is to investigate the properties of workability and strength of the concrete containing admixtures such as silica fume, fly ash, ground granulated blast-furnace slag, and rice husk ash. For this purpose, the workability and the strength of the concrete containing each admixture were tested and analyzed according to the unit weight of binder and the replacement ratio of each admixture. As a result, considering their workability and strength, the existence of minimum binder weight and optimum replacement ratio of concrete containing admixture to plain concrete were obtained for each admixture.

• Journal of the Korea Concrete Institute
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• v.18 no.5 s.95
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• pp.649-656
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• 2006

In this study, powered superplasticizer(PSP) agents to improve the slump loss rate of recycled aggregate concrete were developed. To evaluate the variation of fluidity against elapsed time and the mechanical properties, twenty four specimens whose main variables had the mixing condition of aggregates, such as natural and recycled gravels, and natural and recycled fine aggregates, were tested. The concrete slump with a liquid superplasticizer greatly decreased against the elapsed time and dropped by less than 50% of initial slump after two hours. However the concrete slump with the PSP agents hardly varied until after half an hour and maintained more than 85% of initial slump even after an hour. Also the PSP agents made the compressive, splitting tensile, and flexural strength of concrete increased and the shrinkage strain decreased. Considering the properties improvement of concrete, it can be recommended that optimum mixing amount of the PSP agents should be 5% of the amount of cement.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.4
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• pp.783-794
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• 1994

Recently, several failure cases of concrete structures during construction have been reported. The main reason for these failures is attributed to the poor quality of concrete during construction. It is, therefore. necessary to develop and use high quality concrete. The purpose of the present study is to explore the characteristics of superplasticized concrete, especially the effects of mineral admixtures on the fluidity and strength characteristics of high performance concrete. The mineral admixtures considered in the present study are fly ash, blast furnace slag and silica fume, respectively. The major test variables include the amount of these mineral admixtures, cement contents and water-cement ratios. The compressive strengths for various cases were measured and reported. Optimum contents of mineral admixtures for strength development were derived. The corrosion phenomena of reinforcements embedded in various concrete specimens have been also studied. The present study provides useful basis to apply high-performance concrete to actual structures.