• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.851-854
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• 2008

Using the recycled aggregate not only saves landfill space but also reduces the demand for extraction of natural raw material for new construction activity. However few investigations have been carried out to study the shear behaviors of RC beams with recycled aggregates such as low absorption of recycled aggregate and full-scale specimens. In this study, six reinforced concrete beams were tested to evaluate the effects of shear strength, and shear behavior on the replacement level (0, 30, 60, and 100%) of recycled coarse aggregate and different amounts of shear reinforcement. The results showed that the beams with recycled coarse aggregates present the similar shear strength and deflections as the beam with natural aggregate on an equal amount of shear reinforcement. the reinforced concrete beams with recycled coarse aggregates present the Influence of shear span-to-depth ratio, effective depth, tension reinforcement ratio and compressive strength as the beams with natural aggregate. Shear strength were compared with the provisions in current code (KCI2007) and the equation proposed by Zsutty. The KCI equations were conservative and subsequently can be used for the shear design of recycled aggregate concrete beam.

• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.1
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• pp.1-9
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• 2016

While the amount of construction waste has not been changed much in discharge for last 10 years, the recycled resources refined from construction waste have been mainly applied to low-leveled one such as reclamation, back-fill, road base or subbase and so on. Thus this study addresses the applicability of recycled fine aggregate as a replaceable material in precast concrete. To evaluate the possibility, both of dry and wet processes were adopted as well as steam curing, widely used in the field for rapid producing. Most important experimental parameters were driven through preliminary experiments and were evaluated in terms of concrete properties. It is found from aggregate-replacement tests that all of consistency and strengths of concrete were decreased as the ratio of recycled fine aggregate increased, and the amount of decrease can be estimated using proposed equations. Though the recycled fine aggregate showed a decrease of concrete properties more or less, the applicability in large volume as a constituent of precast product was well noted from experimental results.

• Proceedings of the Korea Concrete Institute Conference
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• 1996.04a
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• pp.388-393
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• 1996

This study evaluated characteristics and performance of recycled concrete as a pavement which was constructed on a low volume road. The recycled concrete was prepared by replacing a half of coarse aggregate with recycled aggregate. Natural sand from a source was used as fine aggregate together with admixtures such as plasticizer and fly ash (0.8% and 5% by wt. of cement, respectively). The length, thickness and width of the pavement were 100mm, 20cm and 3m, respectively. From construction experience, it was found that workability and finishability of the recycled concrete mixture were relatively poor, but strengths were satisfactory. Flexural strength, compressive strength and elastic modulus at 28 days were approximately 45Kg/$\textrm{cm}^2$, 250Kg/$\textrm{cm}^2$, and 240,000 Kg/$\textrm{cm}^2$, respectively. The pavement could be constructed by hand without much difficulty. The surface was finished smoothy by wet fabric and only minor cracks were found on the surface.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.501-504
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• 2006

Recently, the Ceramic Bricks are getting increased due to demolishing aged buildings. But, disposal of the waste ceramic bricks has been relied on just burying into the ground. Regardless they can be used with recycled thick aggregate. Therefore the range of this study includes the experiment of slump test, compression, strength test and stress-strain analysis to the concrete the recycled thick aggregate with made by ceramic bricks. The reducing method of fine aggregate will be reviewed stand on analysis of this experimental result.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.5-8
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• 2008

The use of recycled aggregates is increasing due to problems of lack of natural aggregates. But there are no appropriate design recommendations and basic data for structural members using recycled fine aggregate concrete. This paper is to evaluate compression behavior of reinforced concrete column with displacement level of recycled fine aggregate. For these purpose, four recycled fine aggregate replacement levels (0%, 30%, 60%, 100%) were considered in this paper. Four columns with 400mm${\times}$400mm in cross section are tested under axial load. Experimental results were compared using current code(KCI2007). Compressive strength of reinforced concrete columns with recycled fine aggregate showed higher than that provided in KCI 2007. The KCI provision were conservative and subsequently can be used for design of reinforced recycled fine aggregate concrete column.

• Steel and Composite Structures
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• v.18 no.1
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• pp.213-233
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• 2015

A nonlinear finite element analysis (FEA) model is presented for simulating the behaviour of recycled aggregate concrete-filled steel tube (RACFST) beam-columns subjected to constant axial compressive load and cyclically increasing flexural loading. The FEA model was developed based on ABAQUS software package and a displacement-based approach was used. The proposed engineering stress versus engineering strain relationship of core concrete with the effect of recycled coarse aggregate (RCA) replacement ratio was adopted in the FEA model. The predicted results of the FEA model were compared with the experimental results of several RACFST as well as the corresponding concrete-filled steel tube (CFST) beam-columns under cyclic loading reported in the literature. The comparison results indicated that the proposed FEA model was capable of predicting the load versus deformation relationship, lateral bearing capacity and failure pattern of RACFST beam-columns with an acceptable accuracy. A parametric study was further carried out to investigate the effect of typical parameters on the mechanism of RACFST beam-columns subjected to cyclic loading.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.33-34
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• 2009

In this paper, Recycled aggregate replacement levels were considered. Five columns are tested under axial load. Compressive strength of reinforced concrete columns with recycled aggregate showed higher than that provided in KCI 2007. The KCI provision were conservative and subsequently can be used for design of reinforced recycled aggregate concrete column.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2011.11a
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• pp.101-103
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• 2011

Various desired performances of concrete cannot be always obtained by current conventional mix proportion methods for recycled aggregate concrete (RAC). This paper suggests a new design method of mix proportion for RAC to reduce the number of trial mixes using genetic algorithm (GA) which has been an optimization technique to solve the multi-object problem. In mix design method by GA, several fitness functions for the required properties of concrete, i.e., slump, strength, price, and carbonation speed coefficient were considered based on conventional data or fitness function. As a result, various optimum mix proportions for RAC that meet required performances were obtained and the risk evaluation was also conducted for selected mixtures.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.89-92
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• 2005

An experimental study was conducted to study the mechanical properties of recycled aggregate concrete in accordance with the different replacement ratios of recycled fine and coarse aggregate, ranging from 0$\%$ to 30$\%$ and 0$\%$ to 50$\%$, respectively. According to increase of these replacement ratios, compressive strengths and elastic modulus are reduced down to $10\∼20\%$ and $15\∼30\%$, respectively. The reducing ratios of elastic modulus are more distinct than that of compressive strength. For the selection of replacement ratios of recycled aggregate for structural concrete properly, it is necessary to evaluate the elastic modulus carefully.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.1
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• pp.26-32
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• 2020

Concrete recycling is becoming mandatory rather selective due to depletion of constructional materials and increase of concrete waste. Studies on recycling concrete are conducted in various point of view for long time. However, standard or guideline of many countries for the application of recycled aggregate concrete(RAC) has restrictions such as low replacement rate of coarse aggregate and no fine aggregate allowed due to inferior material properties of recycled aggregate. This study intends to figure out the feasibility of casting natural aggregate concrete(NAC) and RAC separately in a structural member. In making RAC, replacement rate of coarse aggregate was 50, 100% in RAC and treatment of interface of two concretes is introduced. RAC treatment of recycled aggregate or inclusion of additives was not done as it can increase embodied energy of concrete work. Double-shear test with uniformly distributed loading was adopted to evaluate shear strength at the interface of two concretes. After curing it was hard to distinguish interface of two concretes. Experimental result revealed that specimen with higher replacement rate showed higher shear-to-compressive strength ratio, which is possibly attributed to coarse aggregate size and roughness of sheared section. Further study on the effect of various parameters is required and subsequent research activity is on-going.