• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.133-136
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• 2006

This study tested gravity separation with heavy-medium to produce structural recycled aggregates. A result that could produce recycled aggregates attached mortar hardly.

• The Journal of Engineering Geology
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• v.17 no.4
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• pp.589-599
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• 2007

For the preliminary judgement on the chemical stability of concrete aggregates mixed with cement paste, ASTM C 295 method can be applied prior to the long-term chemical test methods. By using this standard test method, the petrographic study on the appropriateness of natural KEDO aggregates for concrete was carried out. With the natural gravel and sand aggregates, the polarized microscope, stereoscopic microscope, and X-ray diffractometer were used for examination. The result shows the 23% of gravel aggregates and 5.1% of sand aggregates are chemically unstable. To select the favorable KEDO concrete aggregates, it is required to exclude the highly metamorphosed rocks, acidic volcanic rocks, highly foliated rocks, and expansive rocks identified from mortar-bar test. Further chemical test and mortar-bar test method integrated with this study is recommended for the suitability assessment of natural KEDO concrete aggregates.

• Journal of the Korea Concrete Institute
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• v.14 no.1
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• pp.16-23
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• 2002

In construction field, million tons of demolished concrete are produced in korea. It is urgently needed that they are used as recycled materials in order to prevent environment pollution and gain economic profits. However, existing recycling methods of demolished concrete have their limits for wide application. They have been only focused on the burying and banking. Therefore, in this paper, physical and mechanical properties of planting concrete using construction wastes for aggregates are described in order to investigate the validities of demolished concrete as recycled aggregates. The Properties of strength and durability are tested. According to the experimental results, compressive strength and freeze-thaw resistance of planting concrete using recycled aggregates shows worse performance than those using crushed stone concrete. But, it shows positive performance on the absorption ratio and thermal conductivity. Especially, considering the side of recycling of concrete wastes, it is recommended that recycled aggregates made with construction wastes is applied to planting concrete.

• Advances in concrete construction
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• v.8 no.2
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• pp.127-137
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• 2019

Roller Compacted Concrete (RCC) is a zero slump concrete consisting of a mixture of cementitious materials, sand, dense graded aggregates and water. In this study, an attempt has been made to investigate the effect of aggregate type on strength and abrasion resistance of RCC made by using granulated blast furnace slag (GGBS) as partial replacement of cement. Mix proportions of RCC were finalized based upon the optimum water content achieved in compaction test. Two different series of RCC mixes were prepared with two different aggregates: crushed gravel and limestone aggregates. In both series, cement was partially replaced with GGBS at a replacement level of 20%, 40% and 60%. Strength Properties and abrasion resistance of the resultant mixes was investigated. Abrasion resistance becomes an essential parameter for understanding the acceptability of RCC for rigid pavements. Experimental results show that limestone aggregates, with optimum percentage of GGBS, perform better in compressive strength and abrasion resistance as compared to the use of crushed gravel aggregates. Observed results are further supported by stoichiometric analysis of the mixes by using basic stoichiometric equations for hydration of major cement compounds.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.243-248
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• 2003

To select the proper material for lean concrete, the recycled aggregates produced by 3 crushers, such as jaw, impact and mill-treated, were investigated for the gradation and the compaction, and strength of concrete made of them. The experiments for all the recycled aggregates used, showed that the cylinders made of them had 7-day compressive strengths over 50kgf/$cm_2$, the provision of qualification, and the OMCs are in the range 5.7% to 6.8%. Also, the unit cement contents for the impact-crushed are 158kg/$cm_2$.

• Advances in concrete construction
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• v.2 no.2
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• pp.77-89
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• 2014

The properties of fresh and hardened concrete made using three types of artificial cold bonded aggregates are determined. The properties, namely, slump, water absorption, compressive strength and splitting tensile strength of concrete containing artificial aggregate are reported. The variables considered are aggregate type and water-to-cement ratio. Three types of cold bonded aggregates are prepared using fly ash and quarry dust. The water-to-cement ratio of 0.35, 0.45, 0.55 and 0.65 is used. The test result indicates that artificial aggregates can be recommended for making the concrete up to a strength grade of 38 MPa. The use of quarry dust in the production of artificial aggregate mitigates environmental concerns on disposal problems of the dust. Hence, the alternate material proposed in this study is a green technology in concrete production.

• Advances in concrete construction
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• v.4 no.3
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• pp.221-230
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• 2016

This paper presents a preliminary study on the influence of laterite soil replacing conventional fine aggregates on the strength properties of GGBS-blended-concrete. For this purpose, GGBS-blended-concrete samples with 40% GGBS, 60% Portland cement (PC), and locally available laterite soil was used. Laterite soils at 0, 25, 50 and 75% by weight were used in trails to replace the conventional fine aggregates. A control mix using only PC, river sand, course aggregates and water served as bench mark in comparing the performance of the composite concrete mix. Test blocks including 60 cubes for compression test; 20 cylinders for split tensile test; and 20 beams for flexural strength test were prepared in the laboratory. Results showed decreasing trends in strength parameters with increasing laterite content in GGBS-blended-concrete. 25% and 50% laterite replacement showed convincing strength (with small decrease) after 28 day curing, which is about 87-90% and 72-85% respectively in comparison to that achieved by the control mix.

• Resources Recycling
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• v.24 no.5
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• pp.63-71
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• 2015

The purpose of this study is to investigate the optimum replacement rate and material properties of eco-friendly recycled concrete using recycled coarse aggregates and rapid-chilled steel slag fine aggregates. The replacement rate of recycled coarse aggregates was increased from 30% to 50% of total volume of coarse aggregates and the rapid-chilled steel slag aggregates were substituted for 10% to 50% of total volume of fine aggregates. As a result, the increment of recycled coarse aggregates in concrete caused the reduction of the compressive strength. On the other hand, as increasing the replacement ratio of rapid chilled steel slag aggregates, the compressive strength was enhanced. Furthermore, the optimum use of rapid chilled steel slag aggregates was suggested up to 20~30% of fine aggregates and the use of it could be helpful to expand the replacement rate of recycled aggregates.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.76-79
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• 2004

The use of recycled aggregate concrete is increasing faster than the development of appropriate design recommendations. This paper is making advances in the recycling of waste concrete material for use as recycled aggregate to make secondary concrete product. Using recycled aggregates from demolished concrete, we manufactured concrete blocks to experiment overall performance in feasible performances. This paper reports limited experimental data on the structural performance of shear wall used concrete blocks made in recycled aggregates. Reinforced concrete frame and shear walls were tested to determine their diagonal cracking and ultimate shear behavior. The variable in the test program was the existence of infilled wall used concrete blocks Made in recycled aggregates. Based on the experimental results, Infilled wall has a high influence on the maximum strength and initial stiffness of reinforced concrete frame. Structural performance of specimen WSB1 and WSB2 is quite different from RCF specimen, particularly strength, stiffness and energy dissipation capacity.

• Proceedings of the Korea Concrete Institute Conference
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• 1996.04a
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• pp.172-179
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• 1996

Recently, the broken concrete lumps resulting from the demolition of concrete structures are creshed for reuse as aggregates(i.e. recycled fine and gravel). And also, in the processing of crusing, the recycled powder of an equivalent of between 20% to 30% by wt.% of the broken concrete lumps is generated. The extensive research of recycled concrete aggregates has been carried out in various parts of the world. But less reseatch on the reuse of recycled concrete powder has been carried out. It is the purpose of this report that the study on the quality evaluation of recycled aggregates for recycled concrete. In specially, this report deals with the properties such as flow, compressive strength, bending strength, drying shrinkage and wight loss rate of mortars replaced standard fine aggregate with recycled powders at the rate of 3, 7, 15, 20 and 30 wt.%. Since the characteristics of recycled mortars with the recycled powders were comparable to those of the normal mortar without the recycled powders as described above, its concretes could be found extensive application in such field as concrete products.