1 The morphology of C - S - H : 2 Lessons from 1 H nuclear magnetic resonance relaxometry 3 4

13 H Nuclear magnetic resonance has been applied to cement pastes, and in particular calcium 14 silicate hydrate (C-S-H), for the characterisation of porosity and pore water interactions for 15 over three decades. However, there is now renewed interest in the method, given that it has 16 been shown to be non-invasive, non-destructive and fully quantitative. It is possible to make 17 measurements of pore size distribution, specific surface area, C-S-H density and water 18 fraction and water dynamics over 6 orders of magnitude from nanoto milli-seconds. This 19 information comes in easily applied experiments that are increasingly well understood, on 20 widely available equipment. This contribution describes the basic experiments for a cements 21 audience new to the field and reviews three decades work. It concludes with a summary of 22 the current state of understanding of cement pore morphology from the perspective of H 23 NMR. 24