• Proceedings of the Korean Institute of Building Construction Conference
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• 2006.05a
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• pp.93-96
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• 2006

As the importance of recycled materials is being emphasized more in the Korean construction market, the production quality has been improved to a significantly high level. Compared to the high quality, however, there are used very limitedly. Among recycled construction materials, recycled aggregates produced through the retreatment of waste concrete are drawing attention because of lack of natural aggregate and heightened consciousness of resource saving and environmental protection and, as a consequence, they are close to natural aggregates in terms of production technology and quality. Despite the high quality and productivity, however, the utilization of recycled aggregates is very low.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2006.05a
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• pp.111-114
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• 2006

Recently, it is increased on the concern for the reuse of waste concrete because of the shortage of natural aggregate and the increase of waste concrete. And recycled coarse aggregate is used variously, but the existing wet method producted recycled fine aggregate has problem like the high price facilities, the long time progress of the work and the poor of recycled fine aggregate. The aim of this study is to investigate outline and performance evaluation of the drying specific gravity separation method to product high duality recycled fine aggregate. Finally, this study is shown investigate process flowing of drying separation type with gravity manufacture, producte system and function of detail devices. The performance of the method of drying specific gravity separation is certificated as the qualities of recycled fine aggregate satisfied the KS

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.4A
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• pp.603-609
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• 2008

The recycled aggregates which were produced from the waste concretes have the disadvantages of inferior properties for natural aggregate. Therefore, in order to reuse the recycled aggregate it must be solved to improve the quality of recycled aggregate. In this study, the quality of recycled aggregate was improved by the surface treatment method using the colloidal silica solution. And, in order to examine the possibility of reusing the surface coated recycled aggregate in constructing concrete structures, we studied the mechanical properties and durability of the concrete using the surface coated recycled aggregates and the other concrete.

• Journal of the Korea Institute of Building Construction
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• v.6 no.2 s.20
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• pp.73-79
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• 2006

The purpose of this study is to enhance the development of construction waste-recycling technologies and its economical efficiency by developing environment-friendly tetrapod, precast concrete, where recycled aggregate is used in order to promote recycling of waste concrete. The results of concrete mechanic characteristics experiments by the circulation coarse aggregate-replacement ratio are as the following. The circulation aggregate is lower and higher than natural aggregate in specific gravity and absorption ratio, respectively so that in case of mix proportioning, unit volume increases, while unit aggregate amount decreases. From the result, sufficient experiments of physical characteristics of circulation aggregate are required to get proper mix proportioning. When circulation aggregate-replacement ratio increases, compressive strength tends to decrease comprehensively, but 50% of replacement ratio is good enough to use. When circulation coarse aggregate's replacement ratio is 0%, drying shrinkage, which causes cracks in concrete and deteriorates durability, shows the minimum length change and the higher the ratio, the larger the length change. Thus. when using circulation coarse aggregate, drying shrinkage should be fairly examined. In freezing-and-thawing resistance, weight loss tends to comprehensively increase its loss at the circulation aggregate-mixed site. And the examination of surface aggregate-omission ratio is further needed and dynamic elastic modulus and durability factor(DF) require more study as well. In order to use circulation aggregate to tetrapod, a clear standard for strength should be first prepared and at the same time, more study about durability is needed.

• Economic and Environmental Geology
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• v.54 no.5
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• pp.515-533
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• 2021

Based on the supply location, demand location, and transportation network, aggregate supply-demand characteristics and aggregate distribution status were analyzed from the results of the closest distance, service areas, and location-allocation scenarios using GIS network analysis. As a result, it was found that the average transport distance of aggregates from the supplier was 6 km on average, the average range of 7 km for sand, and 10 km for gravel was found to reach the destination. In particular, the simulated service area covers about 92% in Seoul-Gyeonggi Province, 85% in Busan-Ulsan-Gyeongnam Province, and more than 90% in Daejeon-Sejong-Chungnam Province. These results have a significant implication in quantitatively interpreting primary data on aggregate supply-demand. Furthermore, these results suggest the possibility of a wide-area quantitative analysis of aggregate supply regions necessary for establishing a basic aggregate plan. The results also evaluated by the site-allocation scenario show that aggregate supply may be possible through companies less than 200 with large-amounts quarries, which is the 700 companies currently supplying small amounts of aggregates on the country. Therefore, in terms of distribution of aggregates, a policy approach is needed to form an appropriate market for regions with high and low density of aggregate supply services, and the necessity of regional distribution and re-evaluation is suggested through an aggregate supply analysis demand across the country. Furthermore, in analyzing the supply-demand network for the aggregate market, additional research is needed to establish long-term policies for the aggregate industry and related industries.

• Journal of the Korean Recycled Construction Resources Institute
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• v.2 no.2
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• pp.76-82
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• 2006

High-strength, High-durability concrete appearance was embossed by benevolence who quality for each raw material that become factor that is direct in concrete manufacture and the special quality is very important and request properties of matter were also strengthened more. Specially, natural resources of good quality were abundant past in occasion of aggregate and unlike concrete request strength past that the importance was less relatively the quality enemy than cement because is also not big, importance of aggregate quality great veried as concrete strength and request properties of matter about durability are strengthened more on extreme displacement. Mixing four who is original and mixs special quality examination of domestic three Four-Stick Games by Chaechwiwon and age Four-Stick Games and crushed sand examined concrete quality characteristic that use mortar and concrete quality characteristic, special quality of North Korea sun guardian mountain three Four-Stick Games that is imported from the North Korea, North Korea sun guardian mountain three Four-Stick Games etc..

• Proceedings of the Korea Concrete Institute Conference
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• 1993.04a
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• pp.12-15
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• 1993

Critical shortage of natural aggregate for production of concrete is developing in many urban area. At the same time increasing quantities of demolished concrete form deteriorated and obsolete structures are generated as a waste material in the same areas. The reuse of a waste concrete may settle the problems of environmental pollution and shortage of adquate aggregate, Therefore, this study is to reuse a waste concrete as aggregate for concrete, It is the purpose of this present study to investigate and analyze how the addition rates of superplasticizer and curing condition affect the properties of fresh and hardened recycled aggregate concrete comparing with those of ordinary concrete and crushed stone concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.217-220
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• 2001

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, especially being want of resources in Korea. For this purpose, concrete made with the pozzolanic cement and recycled aggregate was tested for compressive and tensile strength. The pozzolanic cement was a mixture of OPC(Ordinary Portland Cement) and pozzolans such as fly ash, other siliceous materials and early rapid hardening cement(ERC). It was found that the compressive strength of the pozzolanic cement was enhanced when 0.75% of ERC was dozed, as compared with OPC mortar. It was also shown that compressive and tensile strength of concrete with recycled aggregate and pozzolanic cement were higher than those of concrete with crushed stones and OPC. It was concluded that the pozzolanic cement influenced on the increase of concrete strengths with recycled aggregate.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.373-376
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• 2008

The objective of this study is to investigate the properties of fresh concrete with recycled fine aggregates. Three different kinds of fine aggregate with natural, high and low quality recycled aggregates were prepared. The concrete mixtures were produced with test parameters of replacement ratio of recycled fine aggregate. The properties of the fresh concrete were measured by means of slump and air content according to elapsed time. Quality control method to maintain the constant total mixing water for recycled aggregate concrete was suggested. The all concrete mixtures were produced with approximately the same slump on the job site after an hour. Test results indicated that compressive strength of the concrete mixtures with constant slump is not affected by the replacement ratio of recycled fine aggregate. Therefore, the practical way for the quality control of recycled aggregate concrete is to maintain the constant total mixing water.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.223-228
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• 2003

Recently, owing to the deterioration of reconstruction and the construction, much of the construction waste is discharged in our construction field, and the amount of construction waste is rapidly increased. These waste are raised to financial and environmental problems, so the method of reusing waste concretes has been studied and carried out many direction. Especially being want of resources, if waste concrete could be recycled as aggregates for concrete, it will contribute to solve the exhaustion of natural aggregate, in terms of saving resources and protecting environment. This study is that the mechanical properties of concrete with recycled coarse aggregate were investigated for types of mineral admixture and the substitution of recycled coarse aggregate. The result of this study, in case of using mineral admixture, the property of fresh concrete was rised. And the property of harden concrete for the substitution ratio of recycled coarse aggregate was decreased. But the property of concrete with mineral admixture was better than that of concrete used only cement.