• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.1029-1034
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• 2001

The effects of binder content and silica sand content on the freezing and thawing resistance of lightweight polymer concrete are examined. As a result, the mass loss and pulse velocity of lightweight polymer concrete decrease with increasing binder content and silica sand content. The relative dynamic modulus and durability factor of lightweight polymer concrete reaches minimum at a silica sand content of 50% and a binder content of 28%, and is inclined to increase with increasing binder content and silica sand content.

• Journal of the Korea institute for structural maintenance and inspection
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• v.3 no.4
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• pp.163-171
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• 1999

In this study, we executed fundamental experiment to investigate properties of accelerated carbonation with changing chloride content of concrete used sea sand in order to examine durability. So we obtained the results of following properties of mechanics, durability, concrete with sea sand, determined concrete w/C 30%, 40%, 50%, and fine aggregate 40% and changing containing chloride 0, 0.3, 0.6, $0.9kg/m^3$ by the experiment of accelerated neutralization. The results of this study as follows: 1) As result of changing chloride content of concrete used sea sand augmented in stages $0.3kg/m^3$, accelerated carbonation was increased as increment chloride content. The increment depth was decreased as it went long term age. It was shown the chloride content effected increment of carbonation depth in concrete 2) As a result of changing W/C of concrete used sea sand augmented in stages 10% at a time from 30% to 50%, accelerated carbonation depth of concrete was increased as W/C ratio. 3) As the carbonation concrete used sea sand, compressive strength between 8 weeks and accelerated carbonation depth of 1 weeks, 2 weeks, 4 weeks, 8 weeks was inversion proportion.

• Journal of the Korea Concrete Institute
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• v.18 no.3 s.93
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• pp.415-423
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• 2006

As the shortage of natural & good quality aggregate for concrete, it is needed development of alternative aggregate. At the present time, the crushed sand is widely used among the alternation aggregate, and the usage of crushed sand will be increased more and more. Generally, crushed sud is produced with wet process in domestic, but some manufacturing companies which are handicapped with local restrict are produced by dry process. In this study, analyzing the facilities of dry crushed sand, the quality properties of dry crushed sand was done by Korean Industrial Standards. Based on the quality results of dry crushed sand, the experiment of concrete with the dry crushed sand which is substitute for sea sand was done. As the results of basic qualities, the amount of 0.08 mm sieve passing ratio was over KS criteria, and the fineness modulus was higher than sea sand, and the other physical properties of dry crushed sand was similar to sea sand. The results of concrete experiment, according to the substitutive ratio of dry crushed sand is increased, the slump and air content of concrete was decreased by increase of fine particles of dry crushed sand, and the unit weight content, compressive & tensile strength of concrete were increased on the contrary. The physical properties of concrete used dry crushed sand were showed same tendency without relation to W/B. Consequently, if the fine particle contents of dry crushed sand was lower, it is judged that dry crushed sand is no problem to use for concrete aggregate and the amount of usage will be increased.

• Proceedings of the Korea Concrete Institute Conference
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• 1994.04a
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• pp.152-157
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• 1994

Due to the recent shortage of river sand resulting from a rapid growth of concrete construction, sea sand is increasingly used in stead. It is, however, well noted that non-washed sea sand used in reinforced concrete causes to corrode reinforcing steel and to incur cracks in concrete, and thus eventually result in damage to concrete. In this study, therefore, measeres that increase the quality of concrete were used to protect the reinforcing steel against corrosion in reinforced concrete construction, and then the corrosion resistance of reinforcing steel compared and analyzed from low quality concrete to high quality concrete.

• Journal of the Korea Concrete Institute
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• v.18 no.4 s.94
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• pp.459-467
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• 2006

Recently, interest grew on the quality of aggregates following the diminution of primary resources from river as to grow construction demand and the low grade of nature sand like sea sand. Following, need is to diversify the supply sources of fine aggregates which are excessively relying on sea sand and urgency is to find as soon as possible aggregate resources that can substitute sea sand. On the other hand, various fine aggregates are utilized to produce concrete in the domestic construction fields. However, few studies have been systematically investigated on the effects of such fine aggregates on concrete properties. Therefore, this study examined the effects of comparatively widely used fine aggregates in the domestic construction fields on the quality of concrete through the analysis of the effects of such fine aggregates on the physical properties of fresh concrete and strength of hardened concrete. Results revealed that crushed sand degraded the fluidity and air entraining of concrete compared to natural aggregates like sea sand and river sand. Especially, the use of crushed sand exhibiting bad grain shape and grade was larger adverse effect on the physical properties of concrete. The type of fine aggregates appeared to have negligible influence on the strength for W/C of 55%, 45% while crushed sand decreased the strength for W/C of 35% compared to natural aggregates. It analyzed that the combination of crushed sand exhibiting bad grain shape and grade with natural aggregates improved the characteristics of fresh concrete and had negligible influence on the strength.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.2
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• pp.168-176
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• 2017

This study, as a research for using crushed sand as a fine aggregate of concrete for nuclear structures, we improved the performance of impact crusher in the existing crushed sand production process and adjusted grain size to conform to ASTM C 33 The shape and grain size characteristics of a crushed sand were examined and concrete was prepared according to the substitution ratio of the sand to investigate the properties of fresh concrete and hardened concrete. The experimental results show that most of the concrete characteristics are equivalent to those of concrete using only heavy sand. However, when the substitution rate of steel sand exceeds 50%, the amount of air, compressive strength and tensile strength are somewhat reduced.

• Earthquakes and Structures
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• v.26 no.1
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• pp.77-86
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• 2024

To investigate the seismic performance of steel pipe-aeolian sand recycled concrete columns, this study designed and produced five specimens. Low-cycle repeated load tests were conducted while maintaining a constant axial compression ratio. The experiment aimed to examine the impact of different aeolian sand replacement rates on the seismic performance of these columns. The test results revealed that the mechanical failure modes of the steel pipe-recycled concrete column and the steel pipe-aeolian sand recycled concrete column were similar. Plastic hinges formed and developed at the column foot, and severe local buckling occurred at the bottom of the steel pipe. Interestingly, the bulging height of the damaged steel pipe was reduced for the specimen mixed with an appropriate amount of wind-deposited sand under the same lateral displacement. The hysteresis curves of all five specimens tested were relatively full, with no significant pinching phenomenon observed. Moreover, compared to steel tube-recycled concrete columns, the steel tube-aeolian sand recycled concrete columns exhibited improved seismic energy dissipation capacity and ductility. However, it was noted that as the aeolian sand replacement rate increased, the bearing capacity of the specimen increased first and then decreased. The seismic performance of the specimen was relatively optimal when the aeolian sand replacement rate was 30%. Upon analysis and comparison, the damage analysis model based on stiffness and energy consumption showed good agreement with the test results and proved suitable for evaluating the damage degree of steel pipe-wind-sand recycled concrete structures.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2004.05a
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• pp.51-55
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• 2004

Generally, aggregate may limit the strength of concrete, and aggregate with undesirable properties including strength, shape and grading etc. cannot produce good concrete. Also, the properties of aggregate greatly affect the durability and structural performance of concrete. Recently, it has increased the using of crushed aggregate for concrete due to the exhaustion of good natural aggregate. In case of Korea, the using ratio of crushed stone occupies about 97％ of whole coarse aggregate, and ratio of crushed sand occupies about 18.3％ of whole 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 do suitable mix design and improve the concrete quality. According to results, it was found that nearly all the properties of crushed sand satisfied with the value recommended by KS.

• Journal of Ocean Engineering and Technology
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• v.18 no.1
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• pp.53-62
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• 2004

The Purpose of this study is to recycle the waste concrete, which is generated in huge quantities, from construction works. in order to achieve this goal, it is important to determine the compressive strength, workability, slump, and ultrasonic velocity of recycled aggregate concrete. Thus, several experiment parameters are considered, such as water-cement ratios, sand percentage, and fine aggregate composition ratios, in order to apply the recycled aggregate concrete to pre-cast artificial fishing reefs. From the results, it has been shown that the proper mix designs for reef concrete are W/C=45%, S/a=50%, SR50:SN50 in recycled sand and natural sand mix combination case, W/C=45%, S/a=50%, SC50:SN50 in crushed sand and natural sand mix combination case, W/C=45%, S/a=50%, SR50:SC50 in recycled sand and crushd sand mix combination case. Also, this study shows that the shape and surface roughness of fine aggregate particles have an effect on the strength, slump, ultrasonic velocity of tested concrete, and the compressive strength ratios of 7days' and 90days' curing ages of recycled aggregate concrete are about 70% and 110% of 28days' curing age.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.459-462
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• 2005

Recently, interest grew on the quality of aggregates following the diminution of primary resources from river and the growing construction demand which exhausted high-quality sand sources around large cities and incited the use of low grade aggregates like shore sand and sea sand that can be supplied in natural state. Moreover, the most sensitive aspect highlighted by the unstability of aggregate supply is the quality. The extreme insufficiency of quality criteria about the materials currently used as substitute aggregates and about concrete mixed with such materials is also critical. This study investigated influence of qualities of concrete which is using mixed crushed sand and natural sand