Influence of calcium and magnesium carbonates on hydration kinetics, hydrate assemblage and microstructural development of metakaolin containing composite cements

The hydration of metakaolin composite cements containing quartz, natural limestone and dolomite rock is studied using a multi-method approach and modelling.
The study demonstrates that the calcite present in limestone and dolomite rock is very reactive. Contrary, dolomite does not dissolve. Additionally to the previously reported stabilization of ettringite, the reaction of calcite introduces several changes to the mechanism of metakaolin pozzolanic reaction. Namely, the silicate and aluminate distribution among the hydrates is different. In carbonate containing samples, experimental results supported by the thermodynamic modelling suggest that the silicate mainly precipitates as low Ca/Si C-S-H and additionally the ettringite content is higher. In the case of quartz analogue, the silicates precipitate as striitlingite and C-S-H of higher Ca/Si. These changes cause lower porosity as observed by SEM-BSE and higher strength. High metakaolin reactivity results in a very dense matrix that in turn enables co-existence of phases that are thermodynamically non-compatible.


Published in:
Cement And Concrete Research, 106, 91-102
Year:
Apr 01 2018
Publisher:
Oxford, PERGAMON-ELSEVIER SCIENCE LTD
ISSN:
0008-8846
1873-3948
Keywords:
Laboratories:




 Record created 2018-12-13, last modified 2019-06-19


Rate this document:

Rate this document:
1
2
3
 
(Not yet reviewed)