• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.352-355
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• 2004

Crushed sand is made by crushing the rocks artificially. With a wide shortage of natural river sand all over the region in Korea, demand for crushed sand are becoming increased. However, Informations as to crushed sand are insufficient. In this paper, the actual conditions of crushed sand related to producing and quality variation are investigated. 29 manufacturing company of crushed sand are reviewed. According to results, density of most crushed sand tested exceeded 2.5g/cm3, and absorption ratio meet the requirement of KS except one sample. For grain properties, passing amount of 0.08mm sieve satisfied the requirement of KS except one sample. Grain distribution of most crushed sand is estimated $54.26\%$. But 6 crushed sand sample did not meet the requirement of KS. Fineness modulus and grading are varied from manufacturing region. 18 samples of crushed sand among 29 samples deviated the minimum level of standard grading range by KS. Therefore, improvement of grain properties of crushed sand is urgently needed to manufacture better crushed sand.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.451-454
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• 2005

Recently, Trouble of sand supply is occurred according to exhaustion of natural sand resources. therefore, various measures are proposed for solution of trouble of sand supply and crushed sand among measures is used as one of most universal measures. but because crushed sand have poor particle shape and plenty of makes micro particle, the quality of concrete using crushed sand deteriorated. Therefore, this study evaluated engineering property of concrete with replacement ratio of crushed sand and applied evaluation result to fundamental data for quality control of concrete using crushed sand. The result of this study have shown that quality of concrete using crushed sand independently is poor against general concrete. but, the concrete mixing crushed sand with general sand can be similar in workability of concrete used general sand and increase compressive strength of concrete as against concrete using general sand.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2005.05a
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• pp.33-36
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• 2005

Recently, Trouble of sand supply is occurred according to exhaustion of natural sand resources. therefore, various measures are proposed for solution of trouble of sand supply. also the government settled trouble of sand supply through application of EEZ sand and crushed sand. but because both EEZ sand and crushed sand are poor against general sand, they lead to lowering of quality of ready-mixed concrete. Therefore, this study evaluated physical properties of mortar using EEZ sand and crushed sand and applied evaluation result to fundamental data The result of this study have shown that quality of mortar using EEZ sand and crushed sand independently is poor against general mortar. but, mortar flow and compressive strength is increased in case of mixing 222 sand and crushed sand properly.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.427-432
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• 2001

In this study, crushed sand is blended with river sand and sea sand, to investigate the quality change of antiwashout underwater concrete with variation of blend ratio of crushed sand(0%, 20%, 40%, 60%, 80%, 100%). To see experiment conclusion, the more blend ratio of crushed sand increases, the more unit weight increases. Because the for that specific gravity of crushed sand is higher comparatively than that of river sand and sea sand. Higher compressive strength is measured following the order of river sand, crushed sand, sea sand regardless of age and casting-curing condition. Except for case of using river sand, blend ratio of 40% is appeared on most compressive strength. So the optimum blend ratio of crushed sand is 40% from the view point of compressive strength.

• 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 Korea Concrete Institute Conference
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• 2006.05b
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• pp.105-108
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• 2006

Recently, trouble of sand supplying is occurred according to exhaustion of natural sand resources. Therefore various measures are proposed for solution of trouble of sand supply and crushed sand among measures is used as one of most universal measures. But because crushed sand have poor particle shape and plenty of mikes micro particle, the quality of concrete using crushed sand deteriorated. Therefore, this study evaluated engineering property of concrete with replacement ratio of crushed sand and EEZ sand applied evaluation result to fundamental data for quality control of concrete using crushed sand and EEZ sand and The result of this study have shown that quality of concrete using crushed sand and EEZ sand and The compressive strengh of concrete up to 50, 70% EEZ sand replacement by crush sand, nearly equal to that of general sand.

• International Journal of Concrete Structures and Materials
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• v.6 no.4
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• pp.231-237
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• 2012

Recently, it has been difficult to get natural sand for concrete due to an insufficient supply in Korea. Crushed sand was thought as a substitute and previous research has been focused on low fluidity and normal compressive strength (24-30 MPa). Study on high performance concrete using crushed sand is hardly found in Korea. In this study it was investigated that the effect of the crushed sand on fluidity and compressive strength properties of high performance concrete. Blending crushed sand (FM: 3.98) produced in Namyangju, Kyunggido and sea sand (FM: 2.80) produced in Asan bay in Chungnam. The final FMs of fine aggregate were 3.50, 3.23, and 3.08. W/B was set as 0.25 to get high performance. With the test results an analysis of relationship was performed using a statistical program. It was shown that strength property of concrete using crushed aggregate at the very early age or after specific time was mainly affected by strength development properties of binders instead of the crushed sand.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.443-446
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• 2005

Recently, according to increase use of concrete which is the main material of construction, the natural aggregate of good quality is more and more decreased. Most of all, among the concrete materials, the development of alternation materials of sand is urgently needed. In this study, investigating the production equipment and the sample of crushed sand company and analyzing properties of sand, manufactured mortar by the KS to use crushed sand as the fine aggregate of concrete material. The experiment result is as follows. 1. The density, an absorptivity, and the amount of 0.08mm passage ratio of crushed sand, and the mortar used crushed sand satisfied KS. The mechanical results is similar to sea sand. 2. The crushed sand which used impact crusher instead of cone crusher for 3rd or 4th crusher was similar properties to sea sand, so it is judged that impact crusher has high effect of particle shape improvement of crushed sand.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.383-386
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• 2005

This paper is to investigate the effect of W/B, blend ratio of crushed sand with sea sand on fluidity and strength properties of high strength concrete utilizing crushed sand. W/B set up 0.25, 0.30, 0.35 and the blend ratio of crushed sand with sea sand set up 0:100, 30:70, 50:50, 70:30, 100:0 The results of this study are summarized as the follows; 1) The increase of the blend rate of crushed sand, affected on the enhancement of flow, the increase of dosage of SP and water content, but the decrease S/a 2) Compressive strength is increased when crushed sand $30\~70\%$ was replaced with sea sand. 3) The optimal replacement percentage of crushed sand is $50\%$ with sea sand.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.106-111
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• 2003

This paper is to investigate the characteristics of a concrete in which river sand is partially substituted with crushed sand. Since river sand has a relatively small fineness modulus, there is a need to increase the fineness modulus of sand used in the manufacture of concrete. In an experiment, it was observed that when river sand had a fineness modulus of 2.0~2.4 and crushed sand had a fineness modulus of 2.8~3.5, the substitution rate of the crushed sand was preferably within the range of 25~50%. The experimental results also revealed that as the substitution rate of the crushed sand increased, the flowability of the concrete tended to increase. However, when the substitution rate of the crushed sand reached 75% or more, the workability of the concrete was considerably poor. Further, as the substitution rate of the crushed sand increased, the air content and the bleeding rate of the concrete were low.