Currently the supplementary cementitious materials such as metakaolin are commonly used in the cement and construction industry, due to environmental, economic and technical factors. Most studies evaluating the influence of metakaolin in cementitious systems focus on aspects of performance and mechanical strength at older ages. There are few studies evaluating the initial stage of hydration. Therefore, this paper aims to better understand the influence of the partial replacement of metakaolin in Portland cement pastes during the first 72 hours of hydration. Normally to evaluate the kinetics of hydration heat released is analyzed using an isothermal calorimeter. Nevertheless, another relatively new technique used in this study is to measure the chemical shrinkage continuously; in Brazil are rare studies using chemical shrinkage to obtain hydration kinetics. This study shows the influence of partial replacement of Portland cement by metakaolin in the hydration reactions and chemical shrinkage of cementitious pastes. For this, pastes were prepared using metakaolin replacements of 5, 10 and 20% by mass, and a reference paste, using a constant water/solid ratio of 0.5. Chemical shrinkage was measured continuously automating the method of dilatometry, hydration kinetics was evaluated using an isothermal conduction calorimetry. Additionally, the development of hydrated products was studied by thermogravimetric analysis and X-ray diffraction. The results show that there is an excellent relationship between chemical shrinkage and calorimetry and the addition of metakaolin leads to changes of the hydration kinetics, which also affect the chemical shrinkage.
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