• Journal of the Korea Institute of Building Construction
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• v.16 no.6
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• pp.479-485
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• 2016

This paper presents an experimental study conducted to investigate the effect of recycled fine aggregate (RFA) on the mechanical properties and chloride diffusion behavior of mortar. The test results revealed that the addition of RFA plays an important role in the mechanical properties and pore structures of the investigated mortar specimens as well as chloride diffusion behavior. The mechanical properties such as compressive strength and flexural strength of recycled fine aggregate mortar (RFAM) were gradually decreased as RFA replacement ratio increase. The pore structure of RFAM was examined by permeability tests. The RFAM showed a increment in the permeability according to replacement ratio increase of RFA. But the chloride diffusion coefficient of RFAM was almost same up to 50% replacement ratio of RFA due to a chloride binding phenomenon of RFAM which may compensate the higher permeability of RFAM.

• Journal of the Korean Recycled Construction Resources Institute
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• v.3 no.2
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• pp.146-151
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• 2015

Recycled aggregate by the recycling construction waste has a lot of advantage such as the developing the alternative resource and protecting of environment. However, recycled aggregate is used as the low quality grade, because it is difficult to remove old mortar from aggregate. To use the recycled aggregate as high quality grade, it is important to develop the technology to produce the high quality recycled aggregate. To manufacture the high quality recycled aggregate, old mortar attached on the aggregates should be removed efficiently. Therefore, in this study, we suggested the optimum condition to remove old mortar effectively using sulfuric acid and low speed wet rotary mill for high quality recycled fine aggregate. The results shows that the recycled aggregate satisfy on the standards of KS F 2573 in density, absorption and solid volume, when adequate condition of sulfuric mole ratio and aggregate ratio are make.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.3
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• pp.253-260
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• 2017

The aim of research is to investigate various physical properties of ultra high strength concrete of 80MPa class using a combination of limestone aggregate and electronic arc furnace oxidizing slag aggregate. For aggregate combinations, granite and limestone are used for coarse aggregate, granite and limestone are also used for fine aggregate. And also, limestone fine aggregate is replaced by electronic arc furnace oxidizing slag aggregate of 25% and 50%. Test results indicated that flowability and compressive strength increased when limestone fine aggregate was used compared to that using granite fine aggregate due to higher modulus of elasticity by limestone. Also substitution of electronic arc furnace oxidizing slag aggregate resulted in a decrease of compressive strength slightly. It is found that the use of electronic arc furnace oxidizing slag aggregate and limestone aggregate would be favorable for reducing the autogenous shrinkage by as much as 9~25%.

• Journal of the Korea Institute of Building Construction
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• v.15 no.6
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• pp.553-559
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• 2015

In this study, to suggest the application method of recycled fine aggregate, the non-cement mortar was prepared and studied with the binders of blast furnace slag, fly ash, and fly ash from combined heat power plant. As a basic experiment, a series of tests was conducted to determine the potions of the binders and types of activator. When the binder was consisted with 20% of fly ash and 40% of fly ash from combined heat power plant, the highest strength of the mortar was obtained, and as an activator, the combination of sodium hydroxide 2.5%, and calcium hydroxide 7.5% showed the highest strength of the mortar. Therefore, this study focuses on engineering properties of mortar contains fly ash from combined heat power plant and recycled fine aggregate according to replacement ratio of recycled fine aggregate based on the optimum mix from the basic experiment. As a result, the best replacement ratio of recycled fine aggregate is 75%.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.485-488
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• 2008

Recycled fine aggregate has low quality because it contains large amount of old mortar. So, its usage is limited to a lower value-add, such as the roadbed material etc. Also, alkaline water occurred from treatment process of the waste concrete is becoming the cause of environmental problem. Accordingly, this study is to develop on the high quality recycled fine aggregate produced by low speed wet abraser using sulphuric. We investigated the properties of compressive strength of the mortar which was manufactured using recycled fine aggregate containing calcined gypsum produced by earlier mentioned process. Test results indicate that mortar using recycled fine aggregate containing calcined gypsum has lowest compressive strength. It seems that low compressive strength is closely associated with the expansion of the specimen by excessive formation of ettringite.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.3
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• pp.88-93
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• 2011

To resolve the problem which is demand and supply imbalance of fine aggregate by the shortage of natural fine aggregate and the environment regulations, the studies for the application of recycled fine aggregate made from waste concrete have been recently carried out. The objective of this study is to shed light on the mechanical properties and durability performance of concrete using recycle fine aggregate with various water to cement ratios and unit water contents. And it is intend to propose the fundamental data for structural application of recycled concrete. In particular, the effects according to the variations of water to cement ratios and unit water contents in recycled concrete with recycled fine aggregate replacement of 100 percent are discussed by the test results, such as air content, slump, time of set, compressive strength, tensile strength, carbonation, chloride penetration.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.4
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• pp.490-497
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• 2020

This work has been initiated to find possibility whether recycled fine aggregate can be used as a source of aggregate for structural concrete or not. Two-stage mixing approach was chosen in order to maximize strength potential from recycled fine aggregate. Moisture content of the recycled fine aggregate was changed, and two different types of two-stage mixing approaches were applied to produce cement mortar. The strength of mortar made of 100% recycled fine aggregate by two-stage mixing approaches was compared to that of mortar made of 100% washed sea sand. According to the results, the effect of moisture content on compressive strength was observed from low water cement mortar(W/C 0.3). In case of W/C 0.5 cement mortar, no clear relationship was observed between moisture content and strength development. It was found that two-stage mixing approach has a potential to increase the strength of mortar made of 100% recycled fine aggregate. In case of modified version of two-stage mixing approach which first prepares cement paste and pours recycled fine aggregate into the cement paste, was more effective to increase the strength of mortar made of 100% recycled fine aggregate.

• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.4
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• pp.383-388
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• 2019

The present study evaluated experimentally the effects of the type and content of plastic fine aggregates on cement mortar in order to utilize waste platics as raw materials of concrete. The two kinds of plastics, LLDPE and HDPE were used, and the mixing rate of plastic fine aggregates was increased 0, 25, 50, 75, 100%. The mortar of LLDPE fine aggregate and HDPE fine aggregate showed similar tendency in flow and material separation resistance, density and water absorption, compressive strength and flexural strength by age. The flowability of mortar mixed with plastic fine aggregates was increased up to 50% but decreased at 75% or more. The material separation resistance of mortar with plastic fine aggregates was also dramatically decreased. On the other hand, due to the low density of plastics, the density of mortar decreased with the mixing of plastic fine aggregates. Due to the low adhesion between plastic fine aggregates and cement, the compressive strength by age was decreased in proportion to the mixing ratio of plastic aggregate, but the flexural strength of each age decreased with maintaining a certain level at 50% or more of plastic fine aggregate content.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.205-208
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• 2008

Using the recycled aggregate can reduces the landfill space, the demand for natural raw material for new construction. Some investigations have been carried out to study the shear behaviors of RC beams with recycled aggregates. But these have some limitation due to the use of low quality recycled aggregates and small-scale specimens in the laboratory. In this study, four full-scaled RC beams were tested to evaluate the effects of replacement level (0,30, 60, and 100%) of recycled fine aggregate on shear behavior of RC beams. The results showed that the beams with recycled fine aggregates show similar crack pattern and failure mode compared with the beam with natural aggregate. Also, the beams with recycled fine aggregates present the similar shear strength except the one with the replacement level of 100% recycled fine aggregates. Shear strength were compared with the provisions in current code (KCI2007) and the equation proposed by Zsutty. The KCI equations were conservative and subsequently can be used for the shear design of recycled aggregate concrete beam.

• Journal of the Korean Recycled Construction Resources Institute
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• v.2 no.2
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• pp.145-151
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• 2014

This paper evaluated the quality properties of Finex Water Granulated Slag fine aggregate as part of a study to recycle the Finex Water Granulated Slag generated in korea, and examined the availability as fine aggregate for concrete by comparing properties (properties of fresh concrete, mechanical properties of hardened concrete) of concrete using Finex Water Granulated Slag fine aggregate with properties of concrete using river sand as fine aggregate. From the results of this study, it was found that quality properties of concrete using finex water granulated slag as fine aggregate and concrete using river sand as fine aggregate are equivalent level.