Hydration of Portland cement accelerated by C-S-H seeds at different temperatures

Abstract

C-S-H seeds have potential application as accelerators in oil well cementing pastes. Typical oil well conditions present elevated temperatures; nevertheless, is not clear how such temperatures affect the nucleation process induced by these seeds. In this work, class G cement pastes were blended with up to 5.0% of C-S-H seeds and cured at 25, 40 and 60 °C. Hydration kinetics results showed that the nucleation effect from C-S-H seeds accelerated the reaction by decreasing the apparent activation energy of pastes. This acceleration was more effective at lower temperatures. Nano-mechanical results showed that the main phases obtained from the hydration of cement paste blended with C-S-H seeds are capillary porous material and low density C-S-H. It was concluded that this higher amount of loosely packed hydrates is consequence of an increase in the number precipitation spots, and that their packing density depends on the curing temperature, and amount of C-S-H seeds used.