• Proceedings of the Korean Institute of Building Construction Conference
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• 2006.05a
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• pp.53-56
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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 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 EEZ sand and applied evaluation result to fundamental data for quality control of concrete using crushed sand and EEZ sand. The result of this study have shown that quality of concrete using crushed sand and EEZ sand and The compressive strength of concrete up to 50, 70% EEZ sand replacement by crush sand, nearly equal to that of general sand.

• Computers and Concrete
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• v.15 no.3
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• pp.473-484
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• 2015

In this study, the availability of Schmidt hammer has been investigated as a reliable method to determine the quality of concrete in irrigation networks. For this purpose, the 28-day compressive strength of concrete material used in the construction irrigation channel of Bafra lowland, which is one of the most fertile plains in Turkey was examined by means of concrete compression and as well as concrete Schmidt hammer in laboratory conditions. This study was carried out on cylindrical samples to represent the everyday concrete party ($150m^3$) produced by contractor firm as 3 replications. The statistical analysis of experimental data showed that the correlations between the values of 28-day compressive strength of Schmidt hammer and the rebound number was found to be 0.98. Differences of the compressive strength between compression testing and Schmidt hammer were statistically significant at P<0.01. In this context, it was found that the reliability of compressive strength of the concrete compression test are excellent, also the reliability of compressive strength of Schmidt hammer are fair in assessing the quality of concrete irrigation channels.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.44-47
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• 2003

High flowing concrete has not spread whole in the normal concrete structure, because it requires special quality control technique. Recently owing to the lack of natural resources and reinforcement of environmental standard, the construction cost of cement is rapidly increased. Also ready mixed concrete industry has gone through various economical difficulty as the manufacture cost of concrete is increased. So, the purpose of this study is to evaluate the qualities of middle fluidity concrete using the fly-ash and portland blast-furnace slag cement in order to decrease the amount of cement and resolve the problem of the quality control of high flowing concrete and the manufacture cost. The results of this study show that it reduces the amount of addition of superplasticizer and develope properties of concrete to the use the fly-ash and portland blast-furnace slag cement.

• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.2
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• pp.187-194
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• 2016

In this research, the influence of low-quality aggregate on engineering properties of concrete was experimentally evaluated. From a series of experiment, the results can be summarized as follow: first, the low-quality aggregate in concrete mixture caused up to 83% of decreased slump. For air content, low-quality aggregate increased air content of concrete mixture. Especially, when sea sand was used, because of the narrow gradation with small size, the air content was significantly increased. The compressive strength of concrete mixtures with low-quality aggregates were decreased up to 29% while some cases showed slightly increased compressive strength at early age. Additionally, the concrete mixture mixed with the exploded debris as a coarse aggregate showed approximately 5 to 20% of decreased compressive strength comparing with high-quality of manufacturing rock. In summary, because of the decreased workability of concrete mixture mixed with low-quality aggregates such as exploded debris, clay, and sea sand, it is concerned that worse quality of the ready mixed concrete, produced with the extra water to compensate the decreased workability.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2006.05a
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• pp.35-38
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• 2006

This study investigated fundamental properties of lightweight foamed concrete using cement kiln dust (CKD) and both fly ash(FA) and stability agent. Test results showed that concrete incorporating more amounts of admixture decreased slump flow and it caused increase of superplasiticizer in order to secure the fluidity performance. In addition concrete adding stability agent showed stable flow state, resisting segregation of materials and decreasing bleeding capacity. Sinking depth of concrete incorporating 20% of CKD and adding 0.002% of stability agent was indicated at 0mm. For the properties of hardened concrete. compressive strength of concrete incorporating CKD declined due to a lower appearance density, compared with other specimens. The difference of that was not very significant and the value of ail specimen was higher than KS range. Moreover strength of concrete incorporating CKD was even higher at curing temperature $5^{\circ}C$. Tensile strength ratio of concrete incorporating CKD was indicated between 0.50 to 0.59, which is higher value than control concrete. Heat conductivity of concrete incorporating FA was under the KS range while concrete incorporating 20% of CKD was satisfied in KS. Concrete adding stability agent improved insulation performance due to the lower heat conductivity. In conclusion, it is possible that concrete incorporating 20% of CKD and adding 0.002% of stability agent can secure high quality of lightweight foamed concrete.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.6
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• pp.120-127
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• 2016

Several problems including respiratory and skin disorders due to the problems for sick house syndrome have occurred, there appears echo friendly materials to solve the problems. The research is lacking in quality management techniques ocher concrete using nondestructive tests. In this research, the experimental works were conducted to study the initial quality control for the compressive strength of Ocher concrete(21 MPa). The purpose of this study is the implementation platform for quality management of ocher concrete using nondestructive tests. It uses the relationship between the compressive strength and ultrasonic pulse velocity of the ocher concrete to estimate the compressive strength of the ocher concrete. And using the impact echo method to estimate the thickness of the ocher concrete. The platform is based on a Java script, so that the user can obtain the data through the platform.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.609-612
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• 2006

The quality of the concrete compression strength can be determined after the passage of 28 days, but if any defect is found the quality of concrete after that length of time, there can be serious problems in dismantling and repair. Thus, in response to the use of concrete using non sintering cement (NSC), the present study purposed to propose a method of managing the strength of high strength concrete using NSC in comparison with high strength concrete using ordinary Portland cement (OPC) through early strength estimation using microwave, which enables the quick estimation of the strength of high strength concrete using NSC.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.979-984
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• 2003

Quality control of ready-mixed concrete is most important in the production step because, the performance of hardened concrete is revealed due to ready-mixed concrete. Hardened concrete has several properties physically. Above all things compressive strength of concrete has a greate effect in the design of structures, analysis, and durability. Compressive strength is simple predicted by w/c up to date, but there are some limits because different compressive strengths can be revealed in the same w/c. Therefore this study contributes to the quality control of ready-mixed concrete through statistical analysis for the relation between mix factors in mix design and compressive strength, predictable equation for compressive strength.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2005.11a
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• pp.29-32
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• 2005

Recently, for the problem solution of demand and supply imbalance of fine aggregate due to the shortage of natural fine aggregate and the environment regulation on sea sand extraction in the construction field, the studies for the application of recycled fine aggregate using waste concrete are being progressed versatilely. The purpose of this study is to investigate quality of recycled fine aggregate manufactured by drying manufacturing system which is the manufacture method of high duality recycled fine aggregate, and to analyze on thehardened and durability properties of recycled concrete using it. Therefore it is to present the fundamental data for application and utilization of recycled concrete. The results of this study are as follows; Quality of recycled fine aggregate by drying manufacturing system is improved, and compressive strength, carbonation depth and chloride ion penetration depth of recycled concrete using high quality recycled fine aggregate are similar to those of normal concrete using natural and crashed sand. But, resistance to $H_{2}SO_{4}$ show decreased somewhat.

• Journal of the Korea Institute of Building Construction
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• v.10 no.3
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• pp.57-64
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• 2010

This study is to analyze the effects of aluminum form surface coating material on surface quality of concrete. When observing the surface quality of concrete affected by the change of aluminum form surface coating material, in general, as the number of use of the coating material increased, the surface quality of concrete decreased and good surface quality was shown in plywood (hereinafter PW). For epoxy (hereinafter EP) resin, when applying form remover, good surface quality was shown. For the surface roughness of concrete by the application form oil of form remover and the number of use of the coating material, as the number of use increased, highest surface roughness value was shown which meant the leveling was bad, but the surface roughness value in EP and PW was the lowest. Just for EP, when applying form remover, surface roughness value was low. For the number of void for concrete by the application of form remover and the number of use of the coating material, In general, the number of void which was generated when applying form oil the remover decreased.