• Advances in concrete construction
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• v.16 no.3
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• pp.141-153
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• 2023

In order to develop and take full advantage of pasture fiber and waste concrete, this article studied how different amounts of pasture fiber influenced the toughness and pore structure of concrete with different replacement rates of recycled fine aggregate. Pasture fiber recycled concrete constitutive equations were established under idealized stiffness and toughness damage rate, based on fracture energy and damage mechanics theories. The relationship between pore structure and toughness was studied utilizing nuclear magnetic resonance and fractal theory. The toughness of text groups (0% (JZ), 10% (ZS10), 20% (ZS20)) first increased and then decreased with increasing amounts of pasture fiber, based on the damage rate of toughness. The toughness of concrete samples with recycled fine aggregate and pasture fiber is negatively correlated to the fractal dimension of small and medium-sized pores with a pore size of 0-500 nm. At a replacement rate of 10% of the recycled fine aggregate, the fractal dimension of the air voids (r: 500-9000 nm, i.e., Lg(r) ∈ [2.7, 3.9]) shows a gradual decrease with the increase of grass fiber dosage, indicating that with such a replacement rate of the recycled fine aggregate, the increase of pasture fiber can reduce the complexity of the pore structure of the air voids (500-9000 nm).

• Proceedings of the Korea Concrete Institute Conference
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• 1997.10a
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• pp.45-50
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• 1997

Recycling of waste concrete will contribute not only to the solution of a growing waste disposal problem, also help to conserve natural resources of aggregate and to secure future supply of reasonably recycled aggregates for building construction purpose within large urban areas. Therefore, the purpose of this study is to analyze the applicability of recycled concrete in the influence of a substitute rate of recycled aggregate. As the result of this study, it is possible to conform that the recycled aggregate concrete substituted by 30~50% of the crushed aggregate can be applicated in site.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2002.05a
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• pp.91-96
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• 2002

This study is to investigate the insulation performance of lightweight concrete using recycled lightweight aggregate, to develop lightweight concrete products which have an excellence on the insulation performance are satisfied with properties of building materials. As a result of this study, recycled EPS aggregate is considered to have an independent pores which is closed by dense partitions. So, it is showed that the insulation performance of lightweight concrete using recycled EPS aggregate are excellent. Especially, in the case of lightweight concrete under conditions of replacement ratio over 100%, it is considered that insulation performance is very excellent as thermal conductivity is showed about 0.2kcal/mh$^{\circ}C$. According to considering the relation between ultrasonic pulse velocity, unit weight and thermal conductivity through the graph, the result of relation between ultrasonic pulse velocity, unit weight and thermal conductivity on the graph expressed their high interaction shown as direct proportion on the graph. So that it is possible to extract the insulation performance of lightweight concrete using recycled EPS aggregate by ultrasonic pulse velocity and unit weight.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.3
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• pp.63-69
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• 2020

The volume of construction waste material from the entire waste material volume in Korea is approximately 47.3% to take the biggest ratio, and from them, the waste concrete takes up approximately 62.8% that recycling is an urgent issue to address. Therefore, the government recommends more diverse and broader facilitation of the recycled aggregate in order to promote recycling the construction waste materials. In addition, when using concrete recycled aggregate in building, building standard such as floor area ratio and building height are being mitigation. The standard is a condition that mitigation the floor area ratio by up to 15% when using up to 25% of concrete recycled aggregate. Therefore, this study reviewed the relaxation of construction of construction standards when using concrete recycled aggregate in order to actively recommend the use of concrete recycled aggregate. And using the recycled coarse aggregate among the recycled aggregate, the appropriate mixing time in the batch plant according to the substitution rate was derived. In addition, using recycled aggregate admixture in order to improve the drying shrinkage, did comparative analysis about physical and mechanical property of concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.04a
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• pp.70-75
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• 1999

The purpose of this study is to recycle the waste concrete which is generated in large quantities as crushed stone in construction works. This study deals with the comparative analysis on the construction works and engineering properties of recycled aggregate concrete through physical experiment. The experimental variables are the kinds of aggregates, some different aggregate composition, and W/C ratio(0.40, 0.45, 0.50). It is able to find from the experimental results that the recycled aggregate concrete is good as general concrete on the construction works and engineering propperties. In addition to, the reliable regression analysis equations between compressive strength and various experimental data for recycled aggregate concrete are presented.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.4
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• pp.229-235
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• 2018

In this study, recycled aggregate and natural aggregate were mixed in advance using an aggregate mixing facility that was developed to improve the quality of recycled aggregate concrete. Then the mixed aggregate was applied and concrete characteristics before and after a mix were considered. Based on the findings extracted, this study aimed to suggest a new direction for quality stabilization and application activation of recycled aggregate. The test results of change rates of mortars and coarse aggregates in fresh concrete mixed by a concrete mixer, before and after mixing aggregates showed that the variations of the mortars and coarse aggregates in the concrete mixed with the aggregates beforehand were decreased than those in the concrete before mixing them. The variation of compressive strength and the mean compressive strength at the ages of 3 and 7 days showed similar results before and after the aggregates were mixed, and the strength at the age of 28 days before and after mixing them showed larger deviation than that at the ages of 3 and 7 days. The use of the mixed aggregates after mixing aggregates beforehand reduced the variation in strength and is believed that it is advantageous for long-age strength development. The above results show that the variations of coarse aggregates and compressive strength in the concrete using the mixed aggregates produced by mixing recycled aggregates and natural aggregates beforehand are reduced so it will be possible to produce the homogeneous concrete by mixing aggregates beforehand.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.368-371
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• 2004

It analyzes the quality of the fine aggregate which is reproduced through a dry production process with cyclone and a wet production process. The conclusions of the study are as follows. 1. The recycled fine aggregate through the dry production process with cyclone shows the low rate of absorption and impurity content after the cyclone process. It shows that its density is 2.37, absorption rate is 4.8 and stability is $5.1\%$ and less. Therefore, it satisfies the standards of KS F 2573(recycled aggregate for concrete) as the first grade. 2. The recycled fine aggregate through the wet production process shows the low rate of absorption and foreign substance content after the process of wash and dehydration. It shows that its density is 2.40, absorption rate is 3.12 and stability is $3.2\%$ and less. Therefore, it satisfies the standards of KS F 2573(recycled aggregate for concrete) as the first grade.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.113-116
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• 2006

After laws for recycling promotion of construction wastes was established on December, 2003, successive technical and institutional measures related to construction wastes are driven. Typically quality standards for recycled aggregate were enacted and officially announced, and recently the quality assurance system for recycled aggregate is promoted to be established. In relation, this study reviewed major factors affecting certification examination necessary to carry out quality assurance system for recycled aggregate and related standards to guarantee the quality of recycled aggregate. More specifically it is suggested that working place examination related to manufacturing facility and planning, quality control manpower and system, environmental and safety control, etc, and quality inspection with classified by for road construction, for concrete, and for asphalt concrete are used as quality assurance standards.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.145-148
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• 2005

Recently, because of the increase of management system about waste concrete and the policy of recycling promotion of government, the use of recycled aggregate is rapidly increasing nowadays. But, due to the poverty of quality and the lack of KS standard, the use of recycled fine aggregate is not active. Therefore, it was intended to compare and investigate effects which types of sand and replacement ratio of recycled fine aggregate. As the result of this study, in the case of the recycled replacement ratio of 25$\%$, fresh and engineering properties were higher than those of natural fing aggregates with the exception of durability. Also, because quality according to types of fine aggregate shows the difference between various properties, it was considered that the profound study for this result would be necessary.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.1
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• pp.117-124
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• 2010

The aggregate, which does not satisfy the standard of KS F 2573, was selected for this investigation. The 28day compressive strength of recycled aggregate concrete without pozzolan material was 21.7MPa, which was less than the strength of concrete made with crushed stone. However, the compressive strength at 28 days was improved by mixing early rapid hardening cement to the cement at the weight ratio of 2.5%. Furthermore, the compressive strength at 91 days and 180 days increased significantly by adding fly ash, slag powder, and diatom powder. The tensile strength of recycled aggregate concrete with pozzolan material also increased about 40% compared to the general concrete. Futhermore, the shrinkage and creep of recycled aggregate concrete with fly ash and slag powder was a little decreased that of recycled aggregate concrete with fly ash and diatom powder. Relationship between compressive strength and creep coefficient was shown to the linear relation like as ${\sigma}_c=-30CF+404$.