In situ 1H-TD-NMR: Quantification and microstructure development during the early hydration of alite and OPC

An in situ framework for 1H time-domain nuclear magnetic resonance analysis was developed and applied on alite and OPC hydration. Highly time-resolved quantitative data on the evolution of proton reservoirs during hydration was collected for up to 40 h. Reservoirs could be clearly assigned to mobile (mix water), intermediate (C-S-H) and rigid fractions (CH, ettringite). Comparison of determined fraction quantities with data from in situ XRD measurements and heat flow calorimetry show very good agreement. During alite hydration at 23 °C, a bulk water content of 4 H2O in C1.7SHx was confirmed. T2 relaxation times of the mobile fraction shifted towards shorter times from the start of the main reaction until the maximum of the heat flow. Microstructure evolution is nearly finished at that point in time. T2 relaxation times are severely shortened for iron-containing OPC, but are still evaluable.