The slightly green discs were crushed in a jaw crusher and finely powdered using a ball mill (90 min, 70 rpm, 12.5 mm ZrO 2 balls). The powder was sieved through a sieve with a mesh size of 90 µm and stored in a glass tube under inert conditions. Powder X-ray diffraction (D8 Advance XRD, Bruker AXS, Germany) confirmed the phase composition of the final product. Rietveld analysis reveals a composition of 97.2 wt.% of C 3 S (triclinic), 2.4 wt.% of β-C 2 S,and less than 0.5 wt.% CaO. The specific surface area was determined using nitrogen BET measurement (NOVATouch LX4, Quantachrome Instruments), following the recommended protocol for C 3 S . 1.7 g C 3 S were added to the measuring cell and dried for 1 h at 200 • C under N 2 flow and the N 2 adsorption and desorption isotherms were measured in liquid nitrogen. The BET surface was determined to be 0.83 m 2 g -1 .