In particular, we removed the sample at the maximum calcium concentration, as samples taken at a later point in time (e.g., at the minimum or the second increase in calcium) were too agglomerated and too thick to be properly analyzed (Figure ). The reference sample (Figure ) shows the typical sheet-like structure of C-S-H (Figure A), B)), which was extensively studied in the past by several authors ( ). The sample containing 2 mmol L -1 citric acid shows sheets of C-S-H with a more agglomerated structure (Figure C), D)). This observation shows that citric acid hinders the unfolding and growth of the sheets, which then start to grow together and overlap, resulting in a network of coalesced C-S-H sheets. Tartaric acid led to the formation of two different species (Figure10 E), F)). On the one hand, the additive induced the formation of more extended sheet-like structures with widths of more than 15 × 10 µm, without significant agglomeration (Figure ). On the other hand, globular particles were found, which fit the C-S-H precursor structures described in the literature .