Pore size distribution and degree of hydration of metakaolin-cement pastes

The current paper shows the results of an investigation focussing on the ef fect of metakaolin (MK) on the microstructure of MK blended pastes. Pastes containing 0%, 10%, 15%, 20% and 25% of MK were prepared at a constant wate r/binder ratio of 0.55 and cured at 20 degrees C for hydration periods from 1 to 360 days. On the one hand, the total, capillary, and gel porosity evo lution with the curing time has been investigated. On the other hand, a met hod to estimate the degree of hydration in MK/OPC mixes is proposed in this paper. The values of the degree of hydration are calculated from the amoun t of Ca(OH)(2) present in the paste and from the data of differential therm al analysis (DTA) and thermogravimetry (TG). A good correlation between por osity and degree of hydration has been found. (C) 2000 Elsevier Science Ltd . All rights reserved.