• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.11a
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• pp.61-62
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• 2021

Because of the problem of increasing self-weight due to the enlargement and high-rise of buildings using normal aggregate concrete, the need for structural lightweight aggregate concrete increases. However, early strength prediction is required when placing structural lightweight aggregate concrete, but research is insufficient. In this study, the ultrasonic pulse velocity of normal aggregate concrete and lightweight aggregate concrete was measured at early age. As a result, the ultrasonic pulse velocity of lightweight aggregate concrete was lower than normal aggregate concrete according to elapsed time at early age.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.169-172
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• 2004

Recently, because of the shortage of natural aggregate and the environment regulation of government, the application of recycled aggregate by solution method is observed according as the concern for the reuse of waste concrete. But because the quality of recycled aggregate is poor and quantitative quality judgment standard of recycled aggregate is fluffy, construction field application is difficult. Therefore, this study compares and investigates effect that quality of recycled aggregate influencing recycled concrete. As the result of this study, the more quality of aggregate increases, the more recycled concrete quality increased and high quality recycled aggregate generally displayed performance of similar level with nature aggregate. But, durability of recycled concrete using recycled aggregate appeared lower than concrete using natural aggregate without reference to aggregate quality.

• Korean Journal of Materials Research
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• v.32 no.3
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• pp.115-124
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• 2022

Porous basalt aggregate is commonly used in roadbed engineering, but its application in concrete has rarely been studied. This paper studies the application of porous basalt in concrete. Porous basalt aggregate is assessed for its effects on mechanical strength and durability of prepared C50 concrete; because it has a hole structure, porous basalt aggregate is known for its porosity, and porous basalt aggregates can be made full of water through changing the content of saturated basalt; after full-water condition is achieved in porous basalt aggregate mixture of C50 concrete, we discuss its mechanical properties and durability. The effects of C50 concrete prepared with basalt aggregate on the compressive strength, water absorption, and electric flux of concrete specimens of different ages were studied through experiments, and the effects of different replacement rates of saturated porous basalt aggregate on the properties of concrete were also studied. The results show that porous basalt aggregate can be prepared as C50 concrete. For early saturated porous basalt aggregate concrete, its compressive strength decreases with the increase of the replacement rate of saturated aggregate; this occurs up to concrete curing at 28 d, when the replacement rate of saturated basalt aggregate is greater than or equal to 40 %. The compressive strength of concrete increases with the increase of the replacement rate of saturated aggregate. The 28 d electric flux decreases with the increase of the replacement rate of saturated aggregate, indicating that saturated porous basalt aggregate can improve the chloride ion permeability resistance of concrete in later stages.

• The Journal of Engineering Geology
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• v.13 no.3
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• pp.345-358
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• 2003

Recently, the reuse of coarse aggregate derived from demolished concrete was introduced into practice with two environmental aspects: protection of natural sources of aggregate and recycling of construction waste. However, recycled aggregate has been used for the very limited application such as subbase material for pavement and constructional filling material because it was considered as low quality constructional materials. In the present study, in order to examine the possibility that recycled aggregate can be used for concrete mixing, we conducted various experimental tests to identify mineralogical, chemical and mechanical properties of recycled aggregate and to determine the workability and mechanical properties of recycled aggregate concrete (RAC). The cement paste and mortar contained in recycled aggregate significantly affect the basic mechanical properties of aggregate and the workability and mechanical properties of RAC. However, RCA mixed with the proper replacement ratio of recycled aggregate shows the comparable compressive strength and freeze and thaw resistance to those of normal concrete. Therefore, it is considered that recycled aggregate can be widely used for concrete if the cement paste and mortar can be efficiently removed from recycled aggregate and/or if the effective replacement ratios of recycled aggregate are applied for mixing concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.345-348
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• 2006

Along with recent improvement of recycling technique, the quality of the recycled concrete aggregate have become very competitive to the natural concrete aggregate. Therefore, a practical use of the recycled concrete aggregate may be possible for structural members. Majority studies about the recycled concrete aggregate was emphasized a limitation of fundamental study concerned with a strength characteristics and durability of the recycled aggregate concrete. Therefore, for the extension of application of recycled concrete aggregate, this investigation verifies the strength characteristics and structural performances of PHC piles used with coarce and fine recycled concrete aggregate.

• Proceedings of the IEEK Conference
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• 2001.10a
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• pp.549-554
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• 2001

The authors have proposed that waste glass, which is crushed to pieces, can be used as a concrete aggregate. At the present time, recycled-glass concrete is used for sidewalk concrete blocks and pavement as glass is ornamental. However, in cases where recycled-glass concrete is used for structural concrete, strength and durability are required as structural concrete is exposed to the weather. Glass that is used generally is a mixture of SiO$_2$, Na$_2$O and CaO. SiO$_2$is the most likely cause of alkali-aggregate reaction when waste glass was used for concrete aggregate. In this study, an alkali-aggregate reaction test that is one of the important tests related to durability of aggregate was carried out far discussion of utilization of waste glass for concrete aggregate. From the results of the tests, it is found that glass is a reactive aggregate. The pessimum proportion of glass is about 75%. Then the cases of using fly ash, blast furnace slag and artificial zeolite for admixture materials were also examined for the purpose of prevention of alkali-aggregate reaction. from the results of the test, it was found that using them is an effective way to prevent alkali-aggregate reaction. The compressive strength in the cases of using admixture materials is larger than that without admixture materials.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2011.05a
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• pp.87-88
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• 2011

High absorptance of lightweight aggregate make a hard product, work, quality management ect. for making low absorptance property, lightweight aggregate is coated by an organic matter and that way remarkably showed to decrease the absorptance by pre-study. but first, we would need a check to fit into the concrete which both fresh concrete and hardened concrete. In this study, mechanical property change of coated lightweight aggregate concrete was analysed by compared experiment with coated lightweight aggregate concrete and non-coated aggregate concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.85-88
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• 2001

Utilization of demolished-concrete as recycled aggregate has been researched for the purpose of substituing for insufficient natural aggregate, saving resources and protecting environment. There, however, are some problems that qualities of recycled aggregates are not only largely diverse, but also mechanical properties of recycled aggregate concrete decrease a little in comparison with those of natural aggregate concrete. In this study, the resistance to freezing and thawing of recycled aggregate concrete was highly different due to adhered mortar on recycled aggregate, and durability factor of concrete with NA SRA and DRA was decreased more than that of control concrete. However, durability factor of concrete with AA SRA was larger than that of control concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.384-387
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• 2004

Though recycled aggregate is useful resources for concrete, its application to structural frame is not frequent, because of low quality of recycled aggregate. Owing to the development of manufacturing technology to recycled aggregate, it is possible to produce high quality recycled aggregate. The purpose of this study is to confirm the applicability of the high quality recycled aggregate, instead of the natural aggregate, to normal concrete. Main factors of this study are substitute proportion of recycled aggregate, types of recycled aggregate, targeting compressive strength of recycled concrete. From the results of the study, we concluded that it is possible to use high quality recycled aggregate, to get the same strength as concrete using normal aggregate.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.34 no.10
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• pp.11-18
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• 2018

In this study, the cross-sectional image has been acquired to evaluate the aggregate distribution affecting quality of lightweight aggregate concrete, and through the binarization method, the study is to calculate the aggregate area of upper and lower sections to develop the method to assess the aggregate distribution of concrete. The acquisition of cross-section image of concrete for the above was available from the cross-sectional photography of cleavage tension of a normal test specimen, and an easily accessible and convenient image analysis software was used for image analysis. As a result, through such image analyses, the proportion of aggregate distribution of upper and lower sections of the test specien could be calculated, and the proportion of aggregate area U/L value of the upper and lower regions of concrete cross-section was calculated, revealing that it could be used as the comprehensive index of aggregate distribution. Moreover, through such method, relatively easy image acquisition methods and analytic methods have been proposed, and this indicated that the development of modeling to assess aggregate distribution quantitatively is available. Based on these methods, it is expected that the extraction of fundamental data to reconsider the connectivity with processes in concrete will be available through quality assessment of quantitative concrete.