Notably, the method of determining t is relies on determining the largest slope of the acceleration peak. If a very intense and sharp sulfate depletion peak with a steeper slope than the C 3 S reaction occurs, as has been reported for LC3 systems, the method has additional parameters (not shown in this paper) which can be adapted so that the desired slope, e.g., either the C 3 S or the slope of the sulfate depletion peak, is correctly identified. This is also true for determining the time of maximum acceleration t m . We have shown that t m is perfectly correlated (Figure ) to t is but occurs at a later time. The ASTM method of determining the onset time t AST M has the issue that the reference heat, i.e., the average maximum heat flow, is determined by averaging the maximum heat flow of the curves that should be compared. This implies that t AST M for a sample depends on the other considered samples. Our determination of t AST M exclusively considers the heat flow maximum of the sample itself, which is independent of the sample set and, therefore, unambiguous.