Experimental study on the setting time of cement paste mixed with accelerating admixtures based on C₃A

Setting time is a very important factor in terms of affecting the quality of tunnel lining and inclined slope strengthening. However, the quality criterion of the accelerating admixture (AA) used to improve setting time is not well established. In this study, methods of measuring the setting time of cement pastes with mixed AAs were evaluated using the Gillmore and Vicat needle test methods. It was found that for both test methods, regardless of initial and final setting, the setting time when the admixture was simultaneously added was faster than the post-addition method. For the Gillmore needle test method, two types of measurement methods were evaluated and it was observed that the setting time with cement type varied even when the same AA was used. Accordingly, manufacturing companies should develop AAs that are less influenced by cement type. For the Vicat needle test method, six types of measurement methods were evaluated and the following conclusions were obtained: (a) the temperature of materials should be controlled exactly and (b) to evaluate the performance of AA, an admixture usage of 5% (ratio of cement weight) was recommended.