Effects of metakaolin on the hydration development of Portland–composite cement

Abstract

The hydration reactions of the cement are very complex and there is no single method that determines these reactions. For this reason, a few supplement techniques for various properties and hydration reactions of Portland–composite cement, which are silica fly ash and limestone, containing metakaolin were used in present study. In the first step, the physical, chemical, mineralogical, molecular characterizations of the metakaolin and Portland–composite cement (silica fly ash and limestone) were carried out. In the second step, physical properties and mechanical behavior of Portland–composite cements with metakaolin substituted in ratios of 0, 5, 10, 15 and 20 wt% of the total amount of PCC were determined. At the final stage, hydration reactions of metakaolin–substituted pastes are analyzed by the spectroscopic methods, which are X–ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy, at 28 days. As a result, as the rate of substitution of metakaolin increases, the amount of portlandite which released during hydration, was decreased. In addition, the physical properties and mechanical behavior of Portland–composite cement and metakaolin–substituted paste samples were influenced by the amount of metakaolin.