• Magazine of the Korean Society of Agricultural Engineers
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• v.37 no.1
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• pp.73-80
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• 1995

This study was carried out to investigate the engineering properties of no-fines con- crete, consisting only of coarse aggregate, cement and water. The used coarse aggregates were two, one is natural coarse aggregate grading 4.75~ lOmm, the other is synthetic lightweight coarse aggregate grading 3~8mm. The results of this study are summarized as follows; 1. The W/C ratio of each type was increased with increase of additional amount of coarse aggregate. 2. The unit weight of used ndtural coarse aggregate was shown 1.762~2.184g/cm$^3$, and synthetic lightweight coarse aggregate was shown 0.756 ~ 1 .348g/cm$^3$. 3. The ahsorption rate of used natural coarse aggregate was shown 8.4 ~ 9.4 %, and synthetic lightweight coarse aggregate was shown 17.0~42.4%. 4. The compressive, tensile and hending strength was decreased with increase of coarse aggregate, respectively. The compressive strength of natural coarse aggregate 1:3 was shown 309kg/cm$^2$. 5. The ultrasonic pulse velocity and dynamic medulus of elasticity of each type was de- creased with increase coarse aggregate, respectively. Also, the decreasing rate of the natural aggregate was larger than that of the synthetic lightweight coarse ag- gregate.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2013.11a
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• pp.19-20
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• 2013

Consider about aggregate's price, coarse aggregates from 13 to 25mm were widely used in ready mixed concrete company. But if only use 13 to 25mm aggregates in the concrete, gap grading problem would be occurred. When recycled aggregates from 13 to 25mm was used, continuous grading would increase the durability and strength for the concrete, meanwhile the construction waste materials would also be reused. In this paper, 5-13mm recycled aggregates was utilized, to analyse the fundamental properties for concrete, strength has been tested to evaluate the quality and reusing effect of the recycled materials.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2014.11a
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• pp.137-138
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• 2014

The aim of this research is suggesting the method of obtaining well-graded aggregates for concrete replacing the recycled aggregate which size range is from 5 to 13 mm to currently used gap-graded natural aggregates which size range is only 13 to 25 mm. according to the tests results, the workability of concrete was improved with replacing the aggregates of 5 to 13 mm of size range because of compensating gap-grading. Furthermore, there was an improvement in compressive strength when the aggregates of 5 to 13 mm of size range was replaced because obtained well-graded aggregates contributed on increasing adhesiveness and filling internal pore system. Comparing replacing recycled aggregate to natural aggregate, there was no significant difference on the performances.

• Journal of the Korea Institute of Building Construction
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• v.17 no.1
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• pp.55-61
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• 2017

This paper is to investigate experimentally the effect of substitution of recycled coarse aggregate(RCA) under 13mm on the engineering properties of the concrete using gap graded coarse aggregates. Concretes with 0.4 of water to cement ratio(W/C) were fabricated to achieve 30MPa of design strength with coarse aggregate over 13mm in size with the maximum size of 25mm. RCA was substituted for coarse aggregate over 13mm from 10% to 50% and crushed coarse aggregate under 13mm was also substituted for coarse aggregate over 13mm from 20% to 40%, respectively. Test results indicated that the replacement of RCA up to 20% resulted in an increase of fluidity and strength. It also caused a decrease in the drying shrinkage due to dense packing effect by achieving continuous grading of mixed aggregates. For practical application of RCA, when properly substituted, the use of RCA enabled the concrete to reduce water contents and sand to aggregate ratio in mixing design stage of the concrete. And, it can also enhance the compressive strength of the concrete.

• Journal of the Korea Institute of Building Construction
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• v.5 no.1 s.15
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• pp.63-68
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• 2005

Generally, aggregate may limit the workability, strength and durability of concrete, and good concrete cannot be made with aggregate of bad property including low strength, bad shape and grading. But recently, it has been insufficient in quantity to collect good natural aggregate because of exhaustion of aggregate resources. In case of Korea, the using ratio of crushed stone occupies about 97 percent of total coarse aggregate, and ratio of crushed sand occupies about 18.3 percent of total fine aggregate. This is an experimental study to compare and analyze the properties of crushed sand for concrete in capital region and concrete according to the replacement ratio of crushed sand to improve quality and mix design of concrete using crushed sand. According to test results, it was found that nearly all the properties of crushed sand satisfied with the value recommended by KS. And it is recommended that FM of crushed sand should be lowered by improvement of manufacture system or grading adjustment should be used because FM of crushed sand was a bit higher.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2014.11a
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• pp.53-54
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• 2014

This study evaluates engineering properties of mortar using lightweight fine aggregate made by bottom ash discharged air cooling process according to grading. Then we confirm possibility of use as lightweight fine aggregate. Consequently, Mix using bottom ash need additional examination for a change with the passage of time of flow. Also, mix of S indicates similar compressive strength with mix of Plain and 16% decrease of unit weight compared to mix of Plain; while mix of B indicates 10% decrease of compressive strength and 16% decrease of unit weight. Therefore, this study shows that mix of S and B is superior compared with other mix.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.79-84
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• 2001

Because the WFS(Waste Foundry Sand), by-product of a casting factory, is generally a smaller particle than a fine aggregate, it has a bad influence on quality of concrete. Especially, the grading of aggregate is a very important factor in the case of concrete-based products having low water cement ratio manufactured by vibration and pressing method. Therefore, it is necessary to use WFS with the suitable grading of aggregate that it don't has a bad Influence on the quality of concrete-based products. This study investigated the suitable using proportion of WFS by means of the composition method of aggregate suggested by Driscoll. The results showed that it was desirable to use 10% of WFS since higher strength was developed with that amount.

• Proceedings of the Korea Concrete Institute Conference
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• 1990.10a
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• pp.113-116
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• 1990

This study is designed to analyze the variation of grading and shape of aggregate with the number of rotations of Los-Angeles abrasion machine, and is aimed to analyze the effect of slump and compressive strength of strength of concrete with the shape of coarse aggregate by the abrasion act.

• Computers and Concrete
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• v.10 no.1
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• pp.19-33
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• 2012

The performance of a concrete is significantly influenced by its mixture proportion and the coating thickness on aggregate surface. The concrete in this study is designed by estimating the blending ratio of aggregate using a densified mixture design algorithm (DMDA) based on an ideal grading curve and estimating the paste volume as the sum of the amount of paste needed to provide an assigned coating paste thickness. So as to obtain appropriate concrete amount, and thus can accurately estimate the property of concrete. Deduction of this mix design formula is simple and easy understanding, and meanwhile to obtain result is fast. This estimation model of mix design is expected to reward to industry and effectively upgrade concrete quality.

• Proceedings of the Korea Concrete Institute Conference
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• 1996.10a
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• pp.253-259
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• 1996

The purpose of this study is to investigate the fundamental properties of polyurethan concrete. Polyurethane must be expanded by means of a blowing agent during polymerization. Chemical blowing is caused by the reaction water with isocyanate. Binder system for polyurethane concrete is based on polyol and isocyanate with catalyst, surfactant, and methyl chloride. Polyurethane concretes are prepared with various grading of aggregate, and tested for compressive, flexural strengths, flow test, foaming multiple proportion, working life, condition of surface, distirbution of aggregate. From the test results, the foaming of polyurethane concretes are affceted by amount and grading of aggregate. Workability increases with raising amount of methy chloride and working life reduced according to amount of catalyst. The mix proportion of B with methyl chloride of 1% and catalyst of 0.1g for polyurethane concrete is recommended in consideration of strengths, condition of surface and balance between cost and performance.