The temporal proximity of the initial Vicat set time to the time of the maximum slope t m corresponds to the finding of Ge et al., who also found a very good correlation between the initial set and the maximum slope in the heat flow data . Other authors have observed that the initial Vicat set occurs earlier, i.e., around the first significant rise of the heat flow signal, which we denote as t is in our study . Interestingly, the total heat at the initial set time is not constant for the different dosages of the retarders. The reference sample has a total heat value of 42.7 J g -1 at the initial set time which increases to 72.2 J g -1 at a dosage of 4 µmol g -1 etidronic acid (the value slightly decreases again 71.8 J g -1 for 5 µmol g -1 ). The heat at the final set time increases monotonically for etidronic acid from 49.6 J g -1 for the reference and 85.8 J g -1 for the highest studied dosage of 5 µmol g -1 . The situation is similar for sucrose. Here, the heat at the initial set increases to a maximum value of 72.2 J g -1 at a concentration of 3 µmol g -1 .