Title:
Hydration, Strength, and Microstructural Development of High Early-Strength C4A3S Activated Burnt Oil Shale-Based Cement System
Author(s):
Christian S. B. Paglia, Franz J. Wombacher, and Hans K. Bohni
Publication:
Materials Journal
Volume:
98
Issue:
5
Appears on pages(s):
379-385
Keywords:
early strength; ettringite; hydration.
DOI:
10.14359/10727
Date:
9/1/2001
Abstract:
The high early strength achieved by mixing calcium sulfoaluminate (CSA) and burnt oil shales as main components of a cementitious system is due to the simultaneous formation of ettringite and a dense, amorphous calcium-silicate hydrate (CSH) gel. The CaO saturation of the pore solution simultaneously influences the hydration kinetics of converting both the b-C2S (belite) of the burnt oil shales to CSH gel and the 4CaO·3Al2O3·SO3 (C4A3S) component of the CSA to CSA hydrate (ettringite). The ettringite, in turn, exhibits a strong dependence on the CaO saturation of the pore solution with regards to its formation mechanism, which changes from through-solution to expansive topochemical. An excessive CaO presence, attained using short-term-stored CaO-rich burnt oil shale as a component in the mixture, greatly delays the hydration of the two-phase system (b-C2S/C4A3S), which yields lower early strengths of this composite cement.