• Journal of the Korean Recycled Construction Resources Institute
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• v.2 no.1
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• pp.103-112
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• 2006

Along with recent improvement of recycling technique, the quality of the recycled concrete aggregate have become very competitive to the natural concrete aggregate. Therefore, a practical use of the recycled concrete aggregate may be possible for structural members. Majority studies about the recycled concrete aggregate was emphasized a limitation of fundamental study concerned with a strength characteristics and durability of the recycled aggregate concrete, there is use for the structural members. Therefore, for the extension of application of recycled concrete aggregate, this investigation verifies the strength characteristics recycled concrete aggregate of the spun-concrete products with various coarse and fine recycled aggregate replacement ratio(coarse recycled aggregate: 0%, 20%, 40%, 60%, 100%; fine recycled aggregate: 0%, 30%, 60%, 100%) and with addition of cellulose fibers(0%, 0.01%, 0.03%, 0.05%, 0.08%). From the test results, The strength of spun concrete used with recycled aggregate [NR specimen], was measured as 72MPa, was found to be very approximately to the strength of spun concrete used with the natural aggregate(NN specimen), was measured as 74MPa, when only fine aggregate was replaced with the recycled. Therefore, the fine recycled concrete aggregate can be successfully used in the spun high strength concrete product. The compressive strength of all specimens used the specialty cellulose fiber were measured as about 70M Pa, however, the increasement of the specialty cellulose fiber content is showed to decrease compressive strength of spun concrete. Therefore, it is anticipated that the specialty cellulose fiber can be applied to the various spun concrete products.

• 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 Korean Institute of Building Construction Conference
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• 2015.11a
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• pp.47-48
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• 2015

Recycled aggregate used in a site is strong alkali due to calcium hydroxide attached on its surface. Accordingly, many environmental problems arise. Therefore, as basic research to reduce pH of recycled aggregate, this study tries to reduce the strong alkalinity of recycled aggregate by using mixture solution based on sodium phosphate and ammonium chloride. As a result, original aggregate has the strong alkalinity of pH 11.23, whereas pH of recycled aggregate immersed in mixture solution decreased as more mixture rate increased, and mostly pH 9.8 or less was found.

• Proceedings of the Korea Concrete Institute Conference
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• 1993.04a
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• pp.26-29
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• 1993

To analyze the using of recycled aggregate on concrete as the substitude aggregate is important problem for the reuse of waste matter and prevention of environmental pollution. Therefore, this study is designed for investigating and analyzing the mechanical properties and early estimational properties of strength on concrete using aggregate of the waste concrete. And is aimed to provide the fundamental data for recycled aggregate.

• Proceedings of the Korea Concrete Institute Conference
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• 1993.10a
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• pp.57-60
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• 1993

To analyze the using of recycled aggregate on concrete as the substitude aggregate is important problem for the reuse of waste matter and prevention of environmental pollution. Therefore, this study is designed for investigation and analyzing the mechanical properties and early estimational factors of strength on concrete sing aggregate of the waste concrete. And is aimed to provide the fundamental data for recycled aggregate.

• Journal of the Korea Concrete Institute
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• v.16 no.4 s.82
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• pp.541-548
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• 2004

This study peformed an evaluation of the physical and mechanical properties and sound absorption characteristics of porous concrete according to the target void ratio and content of the recycled aggregate in order to reduce the noise generated in roads, railroads, residential areas and downtown areas and effectively utilize the recycled waste concrete aggregate generated as a byproduct of construction. The test results demonstrated that the difference between the target void ratio and the actual measured void ratio was less than 1.7% and that the tendency of the compression strength was to reduce rapidly when the target void ratio and the content of the recycled aggregate exceeded 25% and 50%, respectively. In addition, the sound absorption characteristics of the porous concrete using recycled waste concrete aggregate showed that the NRC was the highest at the target void ratio of 25% and the content of the recycled aggregate had very little influence on the NRC. Therefore, when considering the compression strength and the sound absorption characteristics of porous concrete, the proper target void ratio and the content of the recycled waste concrete aggregate are thought to be 25% and 50%, respectively

• Journal of the Korea Institute of Building Construction
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• v.17 no.1
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• pp.23-30
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• 2017

The aim of the research is to suggest an economical and sustainable method of reducing pH of recycled aggregate as an embanking and a covering materials. Because of the unhydrated cement based materials on the surface of the recycled aggregate, it causes a severe problem on environment with leaked high alkali water from embankment and covering by using recycled aggregate. In this research, to reduce the pH of recycled aggregate, regarding the recycled fine aggregate, eight different methods were tested and analyzed with three different categorized: natural treatment, artificial treatment, and chemical treatment. From the results of experiment, it was considered that the most efficient method of reducing pH of recycled aggregate was the chemical treatment using acid such as $CO_2$ acceleration or monoammonium phosphate (MAP), and diammonium phosphate (DAP). Especially, using MAP and DAP, fertilizers, is the most efficient method of reducing pH with its time duration and performance.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.1
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• pp.95-102
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• 2011

Vicker's hardness and pore size distribution of mortar adhered to the recycled coarse aggregate were tested according to the strength level of original concrete of recycled coarse aggregate to find the change of mortar adhered to the recycled coarse aggregate in cement paste. The strength levels of original concrete of recycled coarse aggregate were 25.5MPa, 41.7MPa and 60.1MPa and the aggregates were used at the state of saturated surface dry condition and oven dry condition. The results of this experimentation indicated that the mean value of Vicker's hardness was increased according to age and strength of original concrete of recycled aggregate. Porosity of $100nm{\sim}10{\mu}m$ size was reduced and porosity of 6nm~100nm size was increased in cement paste.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.3
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• pp.199-206
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• 2018

Due to the advantages of less raw materials and fossil fuel consumption, lower carbon footprint, and the capability of pavement performance improvement, the recycling technology of asphalt is developed and applied for road rehabilitation and construction in the western countries over the past two decades. Cold recycled asphalt mixtures are bituminous materials normally made by mixing recycled aggregate from wasted asphalt with an asphalt emulsion and water at room temperature. This paper aims at investigating the properties of cold recycled asphalt mixture with alkali-activated filler according to wasted asphalt aggregate content. As a result, as the content of wasted asphalt aggregate increased, the marshall stability of cold recycled asphalt mixture decreased and void ratio increased. Also, grading curves for cold recycled asphalt mixture as specified in GR criteria were satisfied in all aggregate mixing conditions regardless of the wasted asphalt aggregate content.

• 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.