In Figure it is seen that Ca exhibits a wide variety of chemical shifts, depending on its local environment, which arise from the different crystal structures. Since hydrated Portland cement is a mixture of different anhydrous (e.g. C 3 S, C 2 S, C 3 A) and hydrated phases (e.g. C-(A)-S-H, CH, C 6 A$ 3 H 32 ) it raises the question, if Ca NMR could be a useful technique for monitoring the hydration reaction of cement, where these phases coexist.