• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.521-524
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• 2011

본 논문에서는 순환골재에 대하여 구조용 적용성 검증을 목표로 하였으며, 천연골재와 순환골재 치환율에 따른 압축파괴강도와 압축강도증가에 따른 파속도의 상관관계를 비교 분석하였다. 설계기준강도 21, 27, 35MPa에 순환굵은골재 치환율 0, 30, 50, 100%를 적용하여 설계기준강도에 따른 순환굵은골재 치환율의 배합을 총 12가지로 설정하였다. 재령160일까지의 압축파괴강도의 변화를 대기양생 공시체, 수중 양생공시체 그리고 코어공시체를 이용하여 비교하였고, 모의부재(800${\times}$800${\times}$200mm)를 통하여 재령160일까지의 초음파속도를 측정하였다. 압축파괴실험을 통하여 취득한 데이터를 비교해 본 결과 순환굵은골재 치환율에 따른 강도저하현상은 나타나지 않았다. 또한, 재령일에 따른 강도 증가와 함께 파속도도 같이 증가함을 알 수 있었다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.1A
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• pp.213-218
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• 2006

As a manufacturing process of recycled aggregate improves the quality of recycled aggregate shall be sufficient enough to be used for structural concrete. This study characterized compressive strength and elastic modulus of concrete that used recycled coarse and fine aggregate. Before the strength tests, the fundamental characteristics of recycled aggregate were preliminarily analyzed and the recycled aggregate satisfied the class 1 requirements in KS F 2573. As the replacement ratio increased, the compressive strength and elastic modulus of recycled aggregate concrete decreased. When the coarse and fine aggregates were completely replaced with the recycled, the compressive strength and elastic modulus were decreased by 13% and 31%, respectively. Based on the test results, this study suggests equations for predicting the compressive strength and elastic modulus of the recycled aggregate concrete with respect to the replacement ratio. The values from the equations were in good agreement with the test data from this study and others.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.4
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• pp.359-365
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• 2017

This study examined concrete characteristics depending on the replacement ratio of recycled fine aggregates, which suits the KS F 2573 concrete recycled aggregate standard. As physical properties, slump, air content, changes in the elapse of time and compressive strength were studied in order to provide basic data for activation of recycled fine aggregate recycling. As a result of experimenting recycled fine aggregate concrete, the increase in the replacement ratio of recycled aggregates led to the increase in slump and air content. Also, when the replacement ratio of recycled fine aggregates was 30%, it was judged that there was no problem with constructability. When the replacement ratio was 30%, recycled fine aggregate concrete had a similar tendency to natural aggregate concrete at a compressive strength of 24MPa. When the replacement ratio was 30%, at a target strength of 24MPa, recycled fine aggregate concrete had the same physical characteristics as natural aggregate concrete. This means that a replacement ratio of 30% is appropriate for replacement of recycled fine aggregates. In future, there will be a need to improve the quality of recycled fine aggregates for activating the use of recycled fine aggregates and further research will have to evaluate physical properties of recycled fine aggregate concrete using improved recycled fine aggregates.

• 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.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.2
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• pp.144-151
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• 2017

The mechanical properties such as compressive strength and elastic modulus of recycled aggregate concrete containing fly ash are investigated in this study. The experimental parameters were replacement ratio of recycled coarse aggregate(RCA) and fly ash. Replacement ratio of RCA was 0, 30, 50, and 70% and replacement ratio of fly ash was 0, 15, 30%. The experimental results were extensively discussed about compressive strength and elastic modulus of concrete at ages of 7, 28 and 91 days. Compared with concrete not containing fly ash, the decrease of compressive strength and elastic modulus of concrete containing fly ash with the replacement ratio of 30% was significant. Therefore, the test results represented that the fly ash replacement ratio of less than 30% was favorable in terms of mechanical properties of recycled coarse aggregate concrete.

• Journal of the Korea Concrete Institute
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• v.17 no.4 s.88
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• pp.613-620
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• 2005

There are some problems in utilizing recycled concrete aggregate go structural use because of the difficulties concerning about quality control and durability. It seems to be possible to utilize recycled concrete aggregate for making concrete products because quality control of concrete products is easier than ready-mixed concrete, but there are little studies about the properties of the steam-cured recycled aggregate concrete. In this study, various tests were performed such as compressive strength, flexural strength, splitting tensile strength, bonding strength and chloride ion penetration test to evaluate the effect of substitution of recycled concrete aggregate. The results of strength test showed that the concrete strength decreased with the increase of the substitution ratio of recycled concrete aggregate, but it was in the reasonable range and almost equal to that of normal concrete below the substitution ratio of $50\%$. On the other hand, strength test of furnace slag cement concrete shows that the strength of recycled concrete with furnace slag cement under curing condition lower than that of recycled concrete with ordinary portland cement under same condition. From the result of this study, it can be concluded that recycled concrete aggregate is able to be utilized for structural use but substitution ratio should be decided with care in each case. The result of this study could be used as the basic data for the structural use of recycled concrete aggregate.

• 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.

• 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.12 no.2
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• pp.178-187
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• 2024

In this study, it was determined that it was necessary to consider the replacement rate when applying recycled coarse aggregate to concrete, so data on existing research trends and results were collected and the mechanical properties of concrete according to the replacement rate of recycled coarse aggregate were analyzed. In collecting data on recycled coarse aggregate, data without processes such as compressive strength and removal of residual mortar attached to recycled coarse aggregate were collected among the concrete measurement items. In the case of concrete with 50 % and 100 % replacement of recycled coarse aggregate, it was confirmed that the mechanical properties were lower or higher than ordinary concrete by -36.0 ~ 9.9 % and -40.0 ~ 10.4 %, respectively, on average. Accordingly, it is judged that additional water should be mixed in consideration of the absorption rate when mixing, and the replacement rate of recycled coarse aggregate, which has mechanical properties of 80 % or more compared to ordinary concrete, should be less than 50 %.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.2
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• pp.51-58
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• 2018

This study was a basic research for actual production of recycled aggregate concrete, and experiments were carried out on the change of water cement ratio and physical properties of recycled aggregate concrete with fixed slump. Results were as follows. Concrete using recycled aggregate were required increased water to maintain the target slump, and the recycled fine aggregate are necessary more increased water more than the recycled coarse aggregate. The replacement ratio of recycled fine aggregate be less than 60%, would be possible to obtain the air content volume that did not deviate from the concrete quality specification. The compressive strength of concrete using recycled aggregate decreased with increasing the replacement of recycled aggregate, and compressive strength decreased by 25% when 100% recycled fine aggregate were replaced. As a result of analyzing the correlation of compressive strength according to the mixing factors of concrete, it was found that replacement of recycled fine aggregate> water cement ratio> air content volume were influenced in order.