| 種別 | Paper |
| 主題 | Prediction of Strength Development of High Strength Concrete by Using Modified Equivalent Age Method |
| 副題 | |
| 筆頭著者 | Mahmoud NILI （Faculty of Engineering, Hokkaido University） |
| 連名者1 | Kazuhiro NISHIDA （Faculty of Engineering, Hokkaido University） |
| 連名者2 | Osamu KATSURA （Hokkaido Prefectural Cold Region Housing and Urban Research） |
| 連名者3 | Eiji KAMADA （Faculty of Engineering, Hokkaido University） |
| 連名者4 | |
| 連名者5 | |
| キーワード | |
| 巻 | 13 |
| 号 | 1 |
| 先頭ページ | 951 |
| 末尾ページ | 956 |
| 年度 | 1991 |
| 要旨 | INTRODUCTION Several methods for prediction of strength development of concrete have been proposed until now. “Maturity” is one of the familiar method, in which hydration of cement or rate strength development is assumed to be described by a linear function of age and temperature. However, because of some deficiency in this method, the “equivalent age” method as an another approach was proposed. In this method, the hydration process of cement is assumed to follow the Arrhenius equation which is described by an exponential form. The datum temperature and activation energy are the key feature of maturity and equivalent age method, respectively. Until now these two parameters were not so clearly defined. However, the latter approach was best able to account for the combined effect of time-temperature on strength gain. In the case of high strength concrete, there is not so many publication in the region of the rate of strength development. This paper represents the results of rate strength development of the four series of low water-cement ratios: (0.28, 0.32, 0.37 and 0.45). In this experiment the specimens were cast and cured under constant curing temperatures: 5, 10, 20, 30 and 40℃ until testing age. An exponential equation based upon the modified equivalent age is proposed. Analysis of the data show more acceptable fitting than two above mentioned methods. CONCLUSION This study as a result of series of experiments on low water-cement ratio shows that: 1) There is not a quite linear relationship between strength rate development and temperature-time factor over the range of 5℃ to 40℃. 2) Therefore in this range applying of a linear simple relation of M=Σ(T-To)dt as a criterion for strength development is not valid. 3) By data analyzing as described in sec. (3), the activation energy value can be obtained. It is be noted that, only over the range of 5℃ to 20℃ a unique relationship between strength and equivalent age exist. However, this will be valuable, in particular, in cold weather concreting. 4) Because curing temperature affects the final strength of concrete, it is impossible to find a unique strength versus the maturity functions, However, a new method based on exponential equation for the rate development is proposed. By this method a relationship between strength and “modified equivalent age” independent of curing temperature is obtained. It is be noted that, in this regard further research is needed. |
| PDFファイル名 | 013-01-1165.pdf |