• Journal of the Korean Recycled Construction Resources Institute
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• v.3 no.4
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• pp.307-312
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• 2015

This paper addresses mechanical properties and length change performance of the recycled aggregate concretes(RAC) in which natural coarse was replaced by recycled coarse aggregate(RCA) by compressive strength levels(20, 35, 50 MPa). A total of 9 RAC were produced and classified into three series, each of which included three mixes designed with three compressive strength levels of 20 MPa, 35 MPa and 50 MPa and three RCA replacement ratios of 0, 50 and 100%. Physical/Mechanical properties of RAC were tested for slump test, compressive strength, and length change. The test results indicated that the workability of RC could be improved or same by RCA replacement ratios, when compared with that containing no RCA. This is probably because of the RCA shape improving the workability of RAC. Also, the test results showed that the compressive strength was decreased by 9~10% as the RCA replacement ratios increase. However, the length change ratio by the RCA replacement ratios increased regardless of compressive strength levels. At 20 MPa level, the length change ratio was 8~40% which was much higher than that of 4~17% at both 35 and 50 MPa levels. Therefore, it was considered that such admixture addition preventing dry shrinkage is required in order to improve the properties of the RAC at 20 MPa level.

• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.1
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• pp.50-56
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• 2019

This study aims to make artificial stone by recycling blast furnace slag powder, red mud and recycled aggregate, which are known as industrial waste. Recycled aggregate is a typical construction waste, and various recycled products such as concrete block are being sold. In this study, we tried to make artificial stone mixed with waste such as recycled aggregate, and experimented with the use of artificial stone and further study. As the red mud replacement ratio increased, the absorption ratio, fluidity and air content of the matrix were measured to be decreased, and the strength and density were found to increase. The fluidity and absorption ratio decreased with increasing the replacement ratio of recycled aggregate, and the air quantity, rate of aggregate on the surface, density and intensity increased to a certain level. Therefore, this study intends to make artificial stone using recycled resources and conducted basic experiments for further study.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.1
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• pp.8-15
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• 2018

Waste concrete accounts for the largest portion of construction waste, and the supply of natural aggregate is unstable. Therefore, importance of using recycled aggregate is emphasized. The purpose of this study is to investigate the mechanical properties of high strength concrete according to the replacement rate of recycled coarse aggregate. For this purpose, the target design compressive strength was set to 40MPa, and the substitution rates of the recycled coarse aggregate were set to 0%, 30%, 60%, and 100%, respectively. Through experiments on the unreinforced concrete and hardened concrete, The validity of the use was confirmed. In addition, LCA method was used to evaluate the environmental impact of recycled aggregates and to compare and analyze the environmental impacts of the aggregates.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.1097-1100
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• 2008

The purpose of this study to investigate the bond strength of recycled coarse aggregate concrete deteriorated by freezing and thawing. Concrete specimens with recycled coarse aggregate representing lower limit of the quality standard (water absorption : 3.0%, specific gravity : $2.5g.cm^3$) were manufactured and tested. The replacement ratio (0, 30, 60 and 100%) of recycled coarse aggregate and freezing-thawing cycles were considered in this test. From the test results, it was found that the bond strength of normal strength concrete is not affected by the replacement ratio of recycled coarse aggregate under freezing and thawing conditions. Also, the bond strength of the natural and recycled coarse aggregate concrete using AE admixtures was not decreased by frost action.

• Journal of the Korea Concrete Institute
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• v.20 no.2
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• pp.165-173
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• 2008

One of the most important requirements for reinforced concrete constructions is the bond behavior between concrete and reinforcement. For practical application, it is very important to study bond behavior of reinforcing bars in recycled aggregate concrete (RAC). Thirty six pull-out tests were carried out in order to investigate the bond behaviour between recycled coarse aggregate concrete (RCAC) and deformed bars. RCA replacement ratios (i.e., 0%, 30%, 60% and 100%) and positions of deformed bar (i.e., vertical and horizontal position) were considered as variables in this paper. Each specimen was in the form of a cube, with edges of 150 mm in length and for the pull-out tests, a deformed bar, 13 mm in diameter, was embedded in the center of each specimen. Based on the test results, the bond strength between the RCAC and deformed bars were influenced by both RCA replacement ratios and positions of deformed bars. It was found that under the equivalent mix proportion (i.e., the mix proportions are the same, except for different RCA replacement ratios), the bond strength between the RCAC and the ribbed bar has no obvious relation with the RCA replacement ratio, whereas the positions of deformed bars have a significant effect on the bond behavior between the RCAC and deformed bars. Under the condition of same RCA replacement ratio, the specimen of horizontal reinforcement at upper position (HU type) appear considerably low bond stress.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.97-100
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• 2008

In order to recycled wast concrete which is occurred from demolition of the old building, it is effective that the recycled aggregate used as structural concrete aggregate. For used recycled aggregate with structural concrete, the structural capacity must be confirmed. This Study investigated bond capacity which follows in difference of absorption of the aggregate between rebar and concrete. Test results show that there are not a difference of bond strength and slip behavior according to absorption ratio of natural and recycled coarse aggregate.

• 레미콘
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• no.1 s.86
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• pp.42-54
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• 2006

• KSCE Journal of Civil and Environmental Engineering Research
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• v.39 no.4
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• pp.485-492
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• 2019

In this study, the effect of moisture conditions of recycled coarse aggregates on the compressive strength of concrete was evaluated with the water/binder ratios and the curing conditions. The saturated recycled aggregates seemed to have the negative effect on the strength development of concrete. This is the because of the decrease in bond strength between aggregate and cement paste due to the increase of surface water according to the high absorption of recycled aggregates. The effect of types and moisture conditions of aggregates according to the change of water/binder ratio was similar. However, the curing conditions had a significant effect on the compressive strength of the concrete with the different types of aggregates. In the case of curing in air, the recycled aggregates with high absorption reduced the moisture required for hydration and increased the rate of vaporizing, and these result in interfering strength development. The moisture conditions of the recycled aggregates have a considerable effect on the compressive strength of the concrete, and it is necessary to control the moisture conditions of aggregates in the production of concrete with recycled coarse aggregate. And the control of the curing condition is very important for the concrete with recycled aggregate.

• Journal of the Korea Concrete Institute
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• v.28 no.1
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• pp.105-113
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• 2016

Most studies on mechanical properties of concrete with recycled aggregate was focused on the concrete with compressive strength of less than 40 MPa. Therefore, this paper concerns the compressive strength and mechanical properties of concrete with compressive strength of greater than 40 MPa containing recycled coarse aggregate (RCA). The experimental parameters were compressive strength level and replacement ratio of RCA. Compressive strength level was 45 and 60 MPa, and replacement ratio of RCA was 30, 50, 70 and 100%. The results of the test were discussed: compressive strength, elastic modulus, split tensile strength and modulus of rupture. Test results of elastic modulus were compared to the design code predictions. The design code predictions for elastic modulus overestimated the experimental results. However, the design code predictions for modulus of rupture were generally in agreement with the measured values.

• Resources Recycling
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• v.18 no.3
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• pp.20-26
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• 2009

The objective of this study is to investigate the properties of fresh concrete with recycled coarse and fine aggregates. Four different kinds of aggregate with natural, recycled aggregates were prepared. The concrete mixtures were produced with test parameters of replacement ratio of recycled 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 concrete with constant slump is not affected by the replacement ratio of recycled aggregate. Also the practical way for the quality control of recycled aggregate concrete is to maintain the constant total mixing water.