• Title/Summary/Keyword: recycled-aggregate

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Preliminary Study for Optimum Mix Design of Concrete Incorporation Waste Foundary Sand (폐주물사를 혼입한 콘크리트의 최적 배합설계를 위한 기초적 연구)

  • 백민경;이주형;김태경;윤경구;박제선
    • Proceedings of the Korea Concrete Institute Conference
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    • 1996.10a
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    • pp.58-63
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    • 1996

  • The waste foundry sand might be recycled in concrete, resulting in energy saving and environmental protection. An half Factorial Exprements were performed with the variables of W/C ratio, S/A, Sand/Waste foundry sand ratio and Slump as a preliminary study for optimum mix design of concrete. The results show that the W/C ratio is the most important factor to the concrete strength. The substitute of waste foundry sand up to 30% has little influence, saying that it can substitute the fine aggregate without damaging the concrete properties.

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Effect of Inorganic Impurities on the Properties of Lean Concrete (재생골재중에 포함된 이물질이 빈배합콘크리트 물성에 미치는 영향)

  • Kim Jin-Cheol
    • Proceedings of the Korea Concrete Institute Conference
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    • 2005.05b
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    • pp.81-84
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    • 2005

  • We investigated the effect of inorganic impurities such as clay bricks and asphalt concrete in recycled aggregate on the properties of lean concrete. The optimized moisture content of lean concrete with clay bricks increased, because the absorption ratio of clay bricks is high. On the other hand, lean concrete with asphalt concrete produced an opposite result owing to low absorption ratio. The results showed that inorganic impurities did not have a significant effect on compressive .strength of lean concrete containing below 30$\%$ clay bricks and below 10$\%$ asphalt concrete.

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Effect of Recycled Fine Aggregates and Fly Ash on the Mechanical Properties of PVA Fiber-Reinforced Cement Composites (순환잔골재 및 플라이애시가 PVA 섬유보강 시멘트 복합체의 역학적 특성에 미치는 영향)

  • Nam, Yi-Hyun;Park, Wan-Shin;Jang, Young-Il;Yun, Hyun-Do;Kim, Sun-Woo
    • Journal of the Korea Concrete Institute
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    • v.29 no.2
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    • pp.149-157
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    • 2017

  • As the amount of construction wastes increase, reuse of recycled materials is being considered in research areas. While there are many experimental investigations focusing on development of mortar and concrete using the recycled materials, the studies regarding the fiber-reinforced cement composites (FRCCs) using recycled materials are still limited. In this paper, an experimental attempt has been made to investigate the effect of recycled fine aggregates and fly ash on the mechanical properties of PVA FRCCs. The cement and natural sand were respectively replaced by fly ash and recycled fine aggregates at two content levels, 25% and 50%. Ten types of PVA FRCCs mixes were fabricated and tested to investigate the flexural, compressive and direct tensile behaviors. The test results show that flexural, compressive and direct tensile strength were decreased with increase in fly ash content at all ages. In particular, flexural, compressive and direct tensile strengths of specimens, containing 50% recycled fine aggregates and 50% fly ash, showed the lowest values. The modulus of elasticity of specimens showed similar trend to the 28-day compressive strength. Poisson's ratio was increased with increase in fly ash and recycled fine aggregates content.

  • https://doi.org/10.4334/JKCI.2017.29.2.149 인용 PDF KSCI

Reduction of pH of Recycled Fine Aggregate due to Natural and Artificial Treatment Method (자연 및 인위적 처리방법 변화에 따른 순환잔골재의 pH저감)

  • Han, Cheon-Goo;Han, Min-Cheol;Han, Sang-Yoon
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.6 no.1
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    • pp.103-110
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    • 2011

  • This study is to comparatively analyze the characteristics of pH decrease in recycled fine aggregates for embankment and landfill produced from waste concrete by using natural process and artificial process. The result was as follows In case of recycled fine aggregates left outdoor, it was found that pH level was decreased if the thickness of embankment becomes thinner, or the materials left outdoors owing to high concentration of $CO_2$ in atmosphere caused by respirations of people. When the air was permeated, pH level was decreased more effectively. It was analyzed that this phenomenon was caused by efficient supply of $CO_2$ in the recycled fine aggregates owing to high-pressure ventilators. In case of water spraying treatment, sprayed water facilitated hydration of unhydrated cement to dissolve calcium hydroxides which neutralized $CO_2$ in the atmosphere during desiccation process and decrease pH level by a considerable margin. In case of Immersed treatment, decrease of pH was not sufficient. When facilitating the supply of $CO_2$, pH level of the recycled fine aggregates was decreased by the largest margin. It was analyzed that this phenomenon was caused by efficient supply of $CO_2$. From the above results, it was analyzed that the most effective method of reducing pH level of the recycled fine aggregates from the aspects of pH reduction performance, economic efficiency and workability was repeated wet-dry cycles of spraying water to the aggregates in the proportion of 1:0.5 by weight and then treating by forcefully blowing $CO_2$ gas into the aggregates.

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