Effect of metakaolin substitution on physical, mechanical and hydration process of White Portland cement

• Effect of metakaolin on physical and mechanical properties of cementitious composites was studied.
• Metakaolin was substituted with White Portland cement in different proportions.
• Hydration properties of the cement paste were evaluated by spectroscopic methods.
• C-S-H layers were formed on the hydrate particles of all metakaolin replaced with cement pastes.

In this study characterizations of cementitious composites containing metakaolin were examined via spectroscopic methods (XRD, DTA, TGA, FT-IR and SEM). Hybrid binders were obtained by replacing cement with metakaolin (5, 10, 15, 20, 25 and 30% by weight). In addition to spectroscopic methods, the bending and compressive strengths of the prepared samples were measured at the 2nd, 7th, 28th, 56th and 90th days. In conclusion it was determined that while the metakaolin replacement ratio increases the strength values on the 28th day decrease, yet due to the pozzolanic effect significant increases in strength are obtained on the 56th and 90th days.