• Journal of the Korean Society of Safety
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• v.26 no.5
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• pp.65-72
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• 2011

The use of waste concrete can resolve the environmental pollution and shortage of natural aggregate. However, recycled aggregate includes substantial amount of cement paste. So, these aggregates are more porous, and less resistant to mechanical actions than natural aggregates. So, recently, the new manufacture processes of high quality recycled aggregates were suggested such as heating and solving to acid liquid. But the method of solving to acid liquid is not economical and produces additional environmental pollution. In this paper, for the purpose of manufacture of high quality recycled aggregates, the heating processes was added to the existing process of recycled aggregates. To find the optimum process, the experiment was performed by using the method of statistical experiment design, and the heating temperatures(4 levels : 300, 450, 600 and $750^{\circ}C$) and heating times(4 levels : 5, 20, 40, 60 minute) were main experimental variables. By the test results, the optimum manufacturing condition of coarse recycled aggregate was $600^{\circ}C$ and 40 minute, and for the fine recycled aggregate, a little heating made a satisfaction to the KS standard quality code.

• Advances in concrete construction
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• v.4 no.1
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• pp.49-69
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• 2016

This work investigates the mechanical properties of conventional concrete (CC) and self compacting concrete (SCC) using fine rubber and silpozz were accompanied by a comparative study between conventional rubberized concrete (CRC) and self compacting rubberized concrete (SCRC). Fine rubber (FR) from scrap tires has replaced the fine aggregate (FA) and Silpozz has been used as a replacement of cement at the proportions of 5, 10 and 15%. Silpozz as a partial replacement of cement in addition of superplasticiser (SP) increases the strength of concrete. Fresh concrete properties such as slump test, compaction factor test for CRC, whereas for SCRC slump flow, $T_{500}$, V-funnel, L-box, U-box, J-ring tests were conducted along with the hardened properties tests like compressive, split tensile and flexural strength test at 7, 28 and 90 days of curing. The durability and microstructural behavior for both CRC and SCRC were investigated. FR used in the present study is 4.75 mm passing with fineness modulus 4.74.M30 grade concrete is used with a mix proportion of 1:1.44:2.91 and w/c ratio as 0.43. The results indicate that as FR quantity increases, workability of both CRC and SCRC decreases. The results also show that the replacement of natural fine aggregate (NFA) with FR particles decreases the compressive strength with the increase of flexural strength observed upto 5% replacement of FR. Also replacement of cement with silpozz resulted enhancement of strength in SCRC.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.580-583
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• 2004

Due to the tendency of increase in demolished-concrete produced by alteration and deterioration of concrete structures, recycling of those demolished-concrete is necessary to solve the exhaustion of natural aggregate, in order to save resources and protect environment. In this an experimental study herein, the Chlorine-ion and Carbonation resistance of the recycled aggregate concrete was investigated. Coarse aggregate was replaced with $100\%$ of the recycled aggregate and cement and fine recycled aggregate was replaced with various amount. It was shown that the concrete can obtain resistance of chlorine-ion, when fly ash replaced with up to $30\%$ of cement.

• Computers and Concrete
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• v.21 no.3
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• pp.249-259
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• 2018

The use of recycled aggregate in concrete is gaining much attention due to the growing need for sustainability in construction. In the present study, Self Compacting Concrete (SCC) is made using both natural and recycled aggregate (crushed recycled concrete aggregate from building demolished waste) and performance of recycled aggregate based SCC for the bond behaviour of reinforcement is evaluated. The major factors that influence the bond like concrete compressive strength (Mix-A, B and C), diameter of bar ($D_b=10$, 12 and 16 mm) and embedment length of bar ($L_d=2.5Db$, $5D_b$ and full depth of specimen) are the parameters considered in the present study in addition to type of aggregates (natural and recycled aggregates). The mix proportions of Natural Aggregate SCC (NASCC) are arrived based on the specifications of IS 10262. The mix proportions also satisfy the guidelines of EFNARC. In case of Recycled Aggregate SCC (RASCC), both the natural coarse and fine aggregates are replaced 100% by volume with that of recycled aggregates. These mixes are also evaluated for fresh properties as per EFNARC. The hardened properties like compressive strength, split tensile strength and flexural strength are also determined. The pull-out test is conducted as per the specifications of IS 2770 (Part-1) for determining the bond strength of reinforcement. Bond stress versus slip curves were plotted and a typical comparison of RASCC is made with NASCC. The fracture energy i.e., area under the bond stress slip curve is determined. With the use of recycled aggregates, reduction in maximum bond stress is noticed whereas, the normalised maximum bond stress is higher in case of recycled aggregates. Based on the experimental results, regression analysis is conducted and an equation is proposed to predict the maximum bond stress of RASCC. The equation is in good agreement with the experimental results. The available models in the literature are made use to predict the maximum bond stress and compare the present results.

• International Journal of Highway Engineering
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• v.17 no.2
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• pp.63-70
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• 2015

PURPOSES: As a part of our research into repair techniques for roads that have collapsed as a result of a natural disaster, this study set out to find the optimum mix proportion for gravels to be used to restore a damaged area. METHODS: This study considered flow and strength-development characteristics. The experimental variables were the W/C ratio, the usage of the admixture, the types of cement, and the quantity of fine aggregate over three different experimental stages. The compressive strength was measured at 12 hours, one day, three days, and seven days. RESULTS : The flow varied with the amount of fine aggregate and the use of a high-range water-reducing (HRWR) admixture. The compressive strength also varied with respect to the type of cement and the W/C ratios. The strength satisfied the expected requirement of 21 MPa after one day, provided the mix proportion was appropriate. CONCLUSIONS: A gravel-filling high-flow cement-based mortar exhibited strength and consistency with a W/C ratio in the range of 0.40 to 0.45, assuming the use of HRWR at 0.5 to 0.7% and a fine aggregate/cement ratio of 1.0 to 1.5.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.3
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• pp.133-142
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• 2014

Recently, more focus is shift to imbalances in aggregate market supply and demand and an exhaustion of natural resources. In this situation, Electric arc furnace oxidizing slag (EAF Slag) has high application possibility as aggregate for concrete due to similar property with general aggregate. In this study, We've got the plan to assure the chemical stability of EAF Slag, and then experimentally tested the mechanical performance and durability for the fine aggregate used EAF Slag. On this test result, we suggest the application plan. At the result of this study, it shows that EAF slag would reduce the surface defect such as pop-out due to natural aging for the fixed hour and adjustment the grain size of EAF Slag. And mechanical performance and durability according to the replacement rate of concrete service, were revealed more than equal or equal compare to general aggregate. Hereafter, quality control must precede not to impede the beauty of concrete surface as assure the safety for aging and processing. And, to establish the environmental resource recycling system for by-products of steel, it should be made development of various application and guideline of quality control for the EAF slag aggregate. Moreover, it must be constantly studied all kind of engineering performance and durability for related to this study.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.213-216
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• 2004

Aggregate occupies about 70 to 80 percent by volume in concrete as skeleton of concrete, but recently, it has been insufficient in quantity to collect good natural aggregate because of exhaustion of aggregate resources. In case of Korea, in 2002, the using ratio of crushed stone occupies about $97\%$ of whole coarse aggregate, and ratio of crushed sand occupies about $18.3\%$ of whole fine aggregate. This is an experimental study to compare and analyze the properties of concrete according to the grading of crushed stone to improve quality and mix design of concrete using crushed stone. According to results, it was found that grading level of crushed stone in the range of G42 to G60 was better than any other grading level in terms of fluidity and compressive strength. And it is considered to be in the range of 6.52 to 6.85 in terms of FM.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.4
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• pp.101-108
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• 2015

The quantities of heavy weight waste glass have been progressively increased because of the rapid industrialization and the change of quality of life. And, the most of them are not recycled. The heavy weight waste glass have been treated by illegal dumping or being buried in landfills. Meanwhile, in order to ensure the safety of nuclear power plant structure, the excellent construction materials are socially required for shielding performance. Concrete is the most widely used construction material, the huge amounts of natural resources are required to make concrete. So, it is needed to investigate the possibility of recycling of heavy weight waste glass as concrete material ingredient. In this study, the heavy weight waste glass was evaluated for the applicability as fine aggregate of shielding concrete. From the results, when heavy weight waste glass was replaced as fine aggregate of mortar, shielding performance can be improved due to increasing in unit weight of mortar. It showed that the strength decreased according to mixing of heavy weight waste glass, Non-Washed heavy weight waste glass is more advantageous in the strength development than Washed case.

• Journal of the Korean Recycled Construction Resources Institute
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• v.2 no.1
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• pp.103-112
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• 2006

Along with recent improvement of recycling technique, the quality of the recycled concrete aggregate have become very competitive to the natural concrete aggregate. Therefore, a practical use of the recycled concrete aggregate may be possible for structural members. Majority studies about the recycled concrete aggregate was emphasized a limitation of fundamental study concerned with a strength characteristics and durability of the recycled aggregate concrete, there is use for the structural members. Therefore, for the extension of application of recycled concrete aggregate, this investigation verifies the strength characteristics recycled concrete aggregate of the spun-concrete products with various coarse and fine recycled aggregate replacement ratio(coarse recycled aggregate: 0%, 20%, 40%, 60%, 100%; fine recycled aggregate: 0%, 30%, 60%, 100%) and with addition of cellulose fibers(0%, 0.01%, 0.03%, 0.05%, 0.08%). From the test results, The strength of spun concrete used with recycled aggregate [NR specimen], was measured as 72MPa, was found to be very approximately to the strength of spun concrete used with the natural aggregate(NN specimen), was measured as 74MPa, when only fine aggregate was replaced with the recycled. Therefore, the fine recycled concrete aggregate can be successfully used in the spun high strength concrete product. The compressive strength of all specimens used the specialty cellulose fiber were measured as about 70M Pa, however, the increasement of the specialty cellulose fiber content is showed to decrease compressive strength of spun concrete. Therefore, it is anticipated that the specialty cellulose fiber can be applied to the various spun concrete products.

• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.2
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• pp.101-108
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• 2019

This study is analysis of the utilization as a concrete fine aggregate on CGS, a by-product of Integrated coal gasification combined cycle(IGCC). That is, in KS F 2527 "Concrete aggregate," properties of 1~12times to CGS were evaluated, focusing on quality items corresponding to natural aggregate sand(NS) and melted slag aggregate sand(MS). As a result, the distribution of grain shape, safety and expansion were all satisfied with KS standards by physical properties, but the quality was unstable at 7~12times of water absorption ratio and absolute dry density. The particle size distribution was unstable due to asymmetry distribution of coarse particles, and particles were too thick for 7~12times. The passing ratio of 0.08mm sieve was also out of the KS standard at part factor of 7~12times, but chloride content, clay contents, coal and lignite were all satisfactory. Meanwhile, chemical composition was satisfactory except for $SO_3$ in 1~6times, and content and amount of harmful substances were all within the specified value except for F in 7~12times. As a result of SEM analysis, the surface quality and porosity were 7~12times more than 1~6times, and it was the quality was degraded. Therefore, it is necessary to reduce the quality deviation by using separate measures in order to utilize it as concrete aggregate in the future, and if it is premixed with fine quality aggregate, it will contribute positively to solve aggregate supply shortage and utilize circulation resources.