Electron paramagnetic resonance study on metakaolin-admixtured cement paste at different hydrated periods

Abstract

The present work reports the effect of metakaolin (MK) on the properties of Portland cement through electron paramagnetic resonance study. Cement pastes containing 0%, 10%, 20% and 30% replacements of MK with cement and a water to cement ratio of 0.4 have been prepared. The g factors of Fe(III) and Mn(II) impurities at different hydration ages have been related to changes in the setting time of cement. The increase in g _Fe values and simultaneous decrease in g _Mn values with an increase in the replacement percentage of MK are explained due to pozzolanic reaction.

Keywords:

• EPR
• cement
• metakaolin
• setting time
• g-factor

Acknowledgements

The authors wish to acknowledge M/S.20 Microns Limited, Vadodara, India, for supplying the MK used in this investigation.

Notes

Cement nomenclature: C = CaO; S = SiO₂; H = H₂O; C₃S = 3CaO·SiO₂; C₂S = 2CaO·SiO₂; C₃A = 3CaO·Al₂O₃; C₄AF = 4CaO·Al₂O₃ ·Fe₂O₃; CH = Ca(OH)₂.