• International Journal of Highway Engineering
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• v.17 no.3
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• pp.27-33
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• 2015

PURPOSES : To ensure appropriate RCC properties with sufficient strength development and workability, it is necessary to secure a proper level of consistency. It is also necessary to secure maximum dry density, which is an important factor for increasing the interaction of aggregate interlocking, leading to an augmentation of RCC strength. On the other hand, the dry density of RCC can be changed owing to the compaction conditions, water content, and particle size distribution. A Proctor test and a modified Proctor test were used for determining the optimum water content needed to achieve maximum dry density with different amounts of compaction energy. A Vebe test, on the other hand, was used for checking the level of consistency, which is important for producing a workable mixture. METHODS : To confirm the degree of compaction at various particle sizes, RCC mixtures with different sand/aggregate ratios were evaluated. The Proctor test and modified Proctor test were applied to these mixtures to check the effect of the aggregate gradation and compaction energy on the maximum dry density and optimum water content. During each test, three specimens were produced for all types of water content under each aggregate gradation. A compaction curve and the optimum water content and maximum dry density for each aggregate gradation were then obtained for both tests. The range of water content for the appropriate consistency of each aggregate gradation was determined through a Vebe test. The optimum water content was then evaluated based on this range. RESULTS : The compaction test results show that the modified Proctor test provides a higher maximum dry density and lower optimum water content compared with the standard Proctor test. For the modified Proctor test, two cases of aggregate gradation (s/a = 30% and 70%) had the optimum water contents outside of the appropriate water content range. For the standard Proctor test, on the other hand, none of aggregate gradations provided the optimum water content within the desired range. CONCLUSIONS : The modified Proctor test should be used for an RCC mixture design because it can provide adequacy between maximum dry density and consistency. Moreover, the compaction roller has become highly developed for higher compaction energy.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.265-266
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• 2010

In this study, reduction of the crack in the lean concrete for pavements by combining different types of fibers is discussed to compare and verify its validities. Experimental result using NY fibers is depending on excellent aspect ratio and hydrophilic. Vebe time has shown good results. In addition, the addition of PP fiber had most favorable flexural strength.

• Proceedings of the Korea Concrete Institute Conference
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• 1996.10a
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• pp.328-334
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• 1996

This report is the results of an experimental study on the relative effectiveness of different types of steel fiber in concrete. The fibers considered in the study were straight-indent and hooked-collated with aspect ratios of about 50~100. A fiber volume of 0~2 percent was used throughout this investigation. The fresh fibrous mixes were characterized by the slump and vebe-time, and the hardened materials by their compressive and flexural load-deflection relationships. Hooked fibers were found to be more effective than straight ones in improving the strength and energy absorption of concrete.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2009.11a
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• pp.153-156
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• 2009

This study investigated the fundamental properties corresponding to various length changes on NY fiber reinforced concrete. For results of fresh concrete, the slump and air content were declined, but the unit volume weight and vebe time were increased. For the hardened concrete properties, the compressive strength showed increasing tendency according to the NY fiber length. The dry and autogenous shrinkage also decreased compared with Plain. Generally, the caes that 19 mm NY fiber was used was better than any other cases.