• Proceedings of the Korea Concrete Institute Conference
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• 2002.10a
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• pp.223-226
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• 2002

This study is performed to investigate the influence of aggregate factor on the estimation of water content in fresh concrete. According to the results, water content is estimated higher in the case of basalt and granite aggregate than in the case of limestone because absorption water ratio of basalt and granite is large. As the replacement ratio of recycled aggregate increases, water content is estimated higher. But, after correcting absorption water ratio of aggregate, estimated water content is similar to mixture water content. Therefore, it is important to know the absorption water ratio of aggregates accurately, to estimate water content.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05a
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• pp.606-609
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• 2006

In this study, it was selected that in order to make an investigation into the status of the unit water content control of the ready-mixed concrete plants in the country, Capacitance Measurement Method out of various methods which are able to gauge the amount of unit water content in fresh concrete. Then, it were estimated that the quantity of unit water in fresh concrete and the technical standard of every mixture design of the six ready-mixed concrete plants chosen at random in the country. Finally, based on this study, it was proposed as fundamental data to utilize measurement techniques of the quantity of unit water for the quality control of the ready-mixed concrete in construction field.

• International conference on construction engineering and project management
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• 2009.05a
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• pp.754-757
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• 2009

The current concrete maturity method implemented with temperature sensors requires an extensive wiring, which is not often acceptable on construction site due to harsh working environment. Radio Frequency Identification (RFID) technology appears to provide a solution for the wiring issue because of its ability of sending data wirelessly. An RFID tag integrated with a temperature sensor and placed within fresh concrete may be able to read temperatures of concrete and transmit them to an RFID reader wirelessly in real-time. However the previous research illustrated that the RFID signal gets dispersed in liquid medium. One may speculate then whether RFID signals travel through fresh concrete with high water content. Would the tag's burying depth within fresh concrete affect its readability? The paper presents the preliminary results of our on-going investigation on the readability of RFID tags in concrete against water content and burying depth of tags.

• Proceedings of the Korea Concrete Institute Conference
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• 1996.10a
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• pp.17-23
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• 1996

The objective of this study is to present the reference data about the influence of concrete properties using crushed sand, according to the change of powder content and grain shape. From the test results. We obtained that as powder content is increased, sand aggregate ratio, water content and S.P/C are increased in mixing design of concrete. The more powder content is the less slump and air content loss are decreased in fresh state, but the higher compressive strength and drying shrinkage are increased in hardened concrete state. As grain shape become round, water content is decreased in mixing design of concrete. And also, loss of slump and air content in fresh state, compressive strength in hardened state are increased.

• Journal of the Korea Institute of Building Construction
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• v.23 no.2
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• pp.143-152
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• 2023

In this research, the microwave oven drying method was investigated as a potential accurate testing approach for determining the water content of fresh concrete. To do so, water content estimation formulas employed in three prominent oven drying test methods were selected, and the calculation principles for each equation, along with potential error factors arising during the actual testing process, were considered. Moreover, a concrete test was conducted to validate the possible error factors. Consequently, it was confirmed that estimation errors in the water content of fresh concrete can occur due to sample deviations arising during the wet screening process for creating mortar specimens or deviations in the coarse aggregate sampling quantity during the sample collection process.

• Proceedings of the Korea Concrete Institute Conference
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• 1994.10a
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• pp.133-136
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• 1994

This study is to investigate properties of the ultra high-strength concrete using silica rume and fly ash. For this purpose, the properties of fresh concrete and hardened concrete are examined with varing water-cement ratio, silica fume and fly ash content and so on. From these test results, it is possible to maunfacture the miximum strength of 1, 200kg/$\textrm{cm}^2$ with cement content 800kg/$\textrm{m}^3$, 18% water-cement ratio, 105 silica fume content.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.367-370
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• 2005

In this study, air meter method and capacitance measurement method to apply economically at quality control of ready-mixed concrete among various unit water content measurement technique was selected. Then, it was evaluated estimating performance of unit water content according to the change of water-binder ratio and unit water content. Also, it was examined influence about error occurrence of unit water content by change of properties of used materials. Finally, based on this study, it was proposed fundamental data to utilize measurement technique of unit water content to quality control. of ready-mixed concrete in construction field.

• Magazine of the Korea Concrete Institute
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• v.10 no.3
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• pp.23-29
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• 1998

• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.1
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• pp.101-110
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• 2022

In this study, water content tests were performed on various fresh concretes subjected to different binder compostions to review the estimation errors and reliability of water content test methods. Micro-oven drying method, air-meter method, capacitance method and microwave penetration method were used to estimate water content of fresh concrete. Errors in water content estimation were analyzed by each test method. Regardless of the test method of water content, the estimation error was less than 5 %, and in the case of the test using mortar, the error in the estimation value was relatively large. In addition, based on the test results of water content of various concrete, the probability density function in which the estimation error for each test method becomes the population was analyzed. Water content test methods of fresh concrete which using concrete samples showed high estimate reliability of 97 % within the estimation error range of ± 10 kg/m³. On the other hand, the reliability of water content test method using mortar samples was lower.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.373-376
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• 2008

The objective of this study is to investigate the properties of fresh concrete with recycled fine aggregates. Three different kinds of fine aggregate with natural, high and low quality recycled aggregates were prepared. The concrete mixtures were produced with test parameters of replacement ratio of recycled fine aggregate. The properties of the fresh concrete were measured by means of slump and air content according to elapsed time. Quality control method to maintain the constant total mixing water for recycled aggregate concrete was suggested. The all concrete mixtures were produced with approximately the same slump on the job site after an hour. Test results indicated that compressive strength of the concrete mixtures with constant slump is not affected by the replacement ratio of recycled fine aggregate. Therefore, the practical way for the quality control of recycled aggregate concrete is to maintain the constant total mixing water.