| Title |
Effect of Admixture Type and Measurement Method on the Unit Water Content Results of Concrete |
| Authors |
김종(Kim, Jong) ; 김정진(Kim, Jeong-Jin) |
| DOI |
https://doi.org/10.5659/JAIK.2026.42.9.367 |
| Keywords |
Unit Water Content; Moisture Content; Microwave Oven Drying Method; Capacitance Method; Fly Ash |
| Abstract |
In order to control the quality of ready-mixed concrete on the basis of unit water content, this study reviewed the feasibility of applying unit
water content measurement. First, it identified changes in unit water content according to the type of admixture and replacement ratio using
the capacitance method. Then, it compared the results of measurements using the capacitance method to those of the microwave method.
When the capacitance method was used for measurement, the moisture content and unit water content of the mixture with blast furnace slag
were almost the same as the moisture and unit water content of plain concrete. However, when Fly ash was added to the mixture, the
moisture content of both mortar and concrete increased in proportion to the amount of Fly ash, from 10% to 20%, and then to 30%.
Notably, the increase in unit water content of the mixture with Fly ash was directly proportional to the increase in Fly ash. In particular, in
the mixture incorporating 30% FA, the unit water content increased by more than approximately 20 kg/m³, from the reference value of 175
kg/m³ to 195.9 kg/m³. Consequently, the unit water content exceeded the acceptance criteria specified in KCS 14 20 10 for ordinary concrete.
These results indicate that, when FA is used at a high replacement ratio for the purpose of reducing hydration heat, as in mass concrete, the
increase in unit water content should be carefully considered. |