State of water in hydrating tricalcium silicate and portland cement pastesas measured by quasi-elastic neutron scattering

Quasi-elastic neutron scattering (QENS) was used to monitor the state of wa ter in portland cement and tricalcium silicate pastes during the first 2 da ys of hydration at three different temperatures. By applying a double-Loren tzian rather than a single-Lorentzian fitting function, the QENS signal fro m water at a given hydration time was divided into three separate populatio ns arising from liquid water, chemically bound water, and constrained water . The constrained water population consisted of water adsorbed on surfaces and contained in very small (< 10 nm) pores, and could he associated primar ily with the calcium-silicate-hydrate (C-S-H) phase. The rate of increase i n the chemically bound water population closely followed the exothermic hea t output, while the constrained water population increased more rapidly dur ing the first several hours of hydration and then leveled off.