• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.1A
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• pp.229-236
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• 2006

Recently, the use of crushed sand produced by the crushing of stone is continuously increasing to reach an utilization rate of about 20% of the whole fine aggregates that is foreseen to grow larger in the future. However, the lack of recognition concerning quality during the production of crushed sand results in the use of crushed sand that do not satisfy the KS F 2527 standard during the manufacture of concrete. And, studies investigating the effects of such crushed sand on concrete are still neglected. Therefore, this study intends to provide data that can be exploited for concrete using crushed sand through the analysis of the effects of the grain shape of crushed sand on the quality of concrete. Results revealed problems in the workability, air entraining and durability for a value of 53% for the solid volume percentage for shape determination specified by the current KS F 2527. Analysis showed that the adjustment of the solid volume percentage for shape determination from the currently specified 53% to 55% will improve the quality of concrete using crushed sand in high strength concrete particularly.

• Journal of the Korea Institute of Building Construction
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• v.24 no.4
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• pp.393-402
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• 2024

The Korean Industrial Standard(KS) KS F 2527("Aggregates for Concrete") does not explicitly define criteria for clay mineral content in aggregates. This lack of clear quality standards and testing methodologies is further compounded by a scarcity of relevant research within both academic and industrial spheres. Consequently, the construction industry, encompassing both aggregate production and utilization, often overlooks the management of clay mineral content due to its perceived economic implications. This study addresses this gap by investigating the current state of regulations concerning clay mineral content in aggregates, exploring the causes of its occurrence, and evaluating its impact on concrete performance. The chemical composition of the clay minerals was determined to primarily consist of Al₂O₃, Fe₂O₃, and SiO₂, which are commonly found in clay. X-ray diffraction(XRD) analysis revealed that the predominant clay minerals were montmorillonite and illite, both known for their high absorption capacity. An examination of domestic and international standards for clay mineral content in aggregates demonstrated that the density and absorption rate specifications outlined in KS F 2527("Aggregates for Concrete") only offer indirect estimations of clay mineral levels. Furthermore, the investigation into the influence of clay mineral content on concrete performance suggests that a higher clay mineral content necessitates a corresponding increase in the unit quantity of aggregates to maintain adequate workability. This, however, has a detrimental effect on the compressive strength of the concrete.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.05a
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• pp.191-192
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• 2018

This study is a fundamental study to utilize CGS from the IGCC as a fine aggregate for concrete. According to the study, the chemical composition of KS F 2527 was reviewed. The results showed that the KS F 2527 standard was generally satisfied, but the content of the sulfur trioxide(SO₃) exceeded the limit set by the molten slag. The possibility was found to be a fine metal based on chemicals other than sulfur trioxide(SO3).

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.05a
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• pp.56-57
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• 2018

This study is a fundamental consideration for using CGS from the IGCC as a fine aggregate for concrete. For the review, the physical properties and hazardous materials content of KS F 2527 were considered. The results showed that KS F 2527 standard was generally satisfied, making it possible to confirm the possibility that it is a fine metal considering its physical properties and hazardous materials content characteristics.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.465-468
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• 2008

This study investigated the best condition when mixed sand with a river and crushed sand was used though the experiment for the properties of the concrete corresponding to the control of fine aggregate ratio to apply the mixed sand and properties of the fine aggregate at the ready-mixed concrete factory on Yeongnam and Honam. The physical properties of Yeongnam and Honam is satisfied with KS F 2526 and KS F 2527 except fineness modulus and passing amount of 8mm sieve. And, the mixed sand above two types which were incongruent to use individually was being used at each factory, and it was managed in accordance with KS. The flowabillity of the mixture proportion of concrete which was estimated by method of unit volume weight according to the fine aggregate ratio at each factory on Yeongnam and Honam was higher than existing mixture proportion. It was analyzed that the residual water due to decline of the surface area caused by reducing fine aggregate ratio was increased relatively. Accordingly, it was considered that the effect on the economic mixture proportion and improvement of durability might be possible.

• Economic and Environmental Geology
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• v.38 no.3 s.172
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• pp.319-334
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• 2005

Some of old fluvial sediments are originally composed of fine and silty-clay grains with sands or some of them have been segregated by weathering as a result of the influence of groundwater fluctuations. For this reason, some of old fluvial sediments are not suitable for using as fine aggregates. Furthermore, the old fluvial aggregates with comparatively good quality have been exploited for a long time and quality of most remainders have been significantly poor. Though many old fluvial aggregates do not satisfy the quality controls(QC) standards such as KS F2526 and KS F 2527, they must be utilized to various usage suitable far different quality categories. Thus, we try to make constant efforts to utilize aggregates of all qualities. This study shows that physical properties of old fluvial aggregates are both controlled by source rocks and also related to old fluvial environment.

• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.2
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• pp.101-108
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• 2019

This study is analysis of the utilization as a concrete fine aggregate on CGS, a by-product of Integrated coal gasification combined cycle(IGCC). That is, in KS F 2527 "Concrete aggregate," properties of 1~12times to CGS were evaluated, focusing on quality items corresponding to natural aggregate sand(NS) and melted slag aggregate sand(MS). As a result, the distribution of grain shape, safety and expansion were all satisfied with KS standards by physical properties, but the quality was unstable at 7~12times of water absorption ratio and absolute dry density. The particle size distribution was unstable due to asymmetry distribution of coarse particles, and particles were too thick for 7~12times. The passing ratio of 0.08mm sieve was also out of the KS standard at part factor of 7~12times, but chloride content, clay contents, coal and lignite were all satisfactory. Meanwhile, chemical composition was satisfactory except for $SO_3$ in 1~6times, and content and amount of harmful substances were all within the specified value except for F in 7~12times. As a result of SEM analysis, the surface quality and porosity were 7~12times more than 1~6times, and it was the quality was degraded. Therefore, it is necessary to reduce the quality deviation by using separate measures in order to utilize it as concrete aggregate in the future, and if it is premixed with fine quality aggregate, it will contribute positively to solve aggregate supply shortage and utilize circulation resources.

• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.3
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• pp.285-292
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• 2022

The objective of this study is to investigate whether CGS generated in IGCC satisfies the fine aggregate quality items specified in KS F 2527(Concrete Aggregate) through the pretreatment process system and the quality improvement the system. The statistical significance of the pretreatment process was analyzed through Repeated Measurements ANOVA as measured values according to individually pretreatment process system. As a result of the analysis, In the case of CGS fine aggregate quality before and after the pretreatment process system, the density increased 5.2 %, the absorption rate decreased by 1.86 %, the 0.08 mm passing ratio decreased by 2.25 %, and Fineness Modulus and Particle-size Distribution were also found to be adjustable. It was found that the pretreatment process system was significant in improving the quality of CGS.

• Journal of Korean Society of Disaster and Security
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• v.17 no.1
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• pp.27-35
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• 2024

This paper presents experimental research results to evaluate the applicability of chemical neutralization reaction and ultrasonic wave to remove cement paste and mortar attached to the surface of recycled aggregate. In order to derive optimal ultrasonic cleaning efficiency and chemical neutralization reaction, experiments were conducted using variables such as ultrasonic frequency and type of chemical solution. As a result, the optimal frequency was found to be 24 kHz, and immersion in a 15% hydrochloric acid solution for 30 minutes of stimulation showed the highest efficiency. In addition, the specific gravity, absorption rate, and wear rate of the quality-improved recycled coarse aggregate were similar to those of general aggregate and were found to satisfy all KS F 2527 standards. Therefore, it is believed that the recycled aggregate whose quality has been improved through the method proposed in this study can be used for concrete.

• Journal of the Korea Institute of Building Construction
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• v.24 no.5
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• pp.565-575
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• 2024

This research was initiated to establish quality standards and testing methods for fine dust in aggregates, a component currently not regulated under the Korean Industrial Standards(KS) KS F 2527 for Concrete Aggregates. With limited existing research and no definitive quality or testing standards for fine dust, this study sought to provide a quantitative analysis of fine dust in aggregates and to set forth quality standards based on the dust content through a concrete performance evaluation. The experimental findings showed that the primary chemical constituents of the fine dust were aluminum oxide(Al₂O₃), iron oxide(Fe₂O₃), and silicon dioxide(SiO₂). It was observed that increasing levels of fine dust in the aggregates led to higher values of the fine dust index(Al₂O₃+Fe₂O₃). This escalation in the fine dust index corresponded with an increase in the unit water content of the concrete and a consequent decline in compressive strength. Based on these observations, a maximum allowable limit for the fine dust index in aggregates was proposed at 23%. This limit was derived from the correlation between fine dust content and a 15% reduction in compressive strength of standard concrete specimens. The proposed evaluation method for the fine dust index based on its content in aggregates is expected to enhance concrete performance and ensure structural stability. This contribution to the field addresses a significant gap in the standards and provides a foundation for further research and standardization in the construction materials industry.