Influence of Nucleation Seeding on the Compressive Strength of Ordinary Portland Cement and Alkali Activated Blast-furnace Slag

Infrastructure Technology Institute Year 2 Final Report DISCLAIMER The contents of this report reflect the views of the authors, who are responsible for the facts and the accuracy of the information presented herein. This document is disseminated under the sponsorship of the Department of Transportation University Transportation Centers Program, in the interest of information exchange. A study is conducted to determine the effects on the early hydration kinetics and compressive strength by seeding of Portland cement and alkali-activated blast furnace slag with a pure form of calcium silicate hydrate (C-S-H). The effects of C-S-H seeding during the early nucleation and growth period of each type of cement, was measured with an isothermal calorimeter during the first day of hydration. The compressive strength was determined for 2 " cylinders up to 28 days after mixing. It was found that C-S-H seeding results in an earlier and larger hydration heat development peak for both types of cement. The addition of C-S-H seed to the slag cement paste produced a significant increase in compressive strength only when cured in a sealed environment. For the Portland cement paste, the C-S-H seeding provides a slight increase in compressive strength when cured underwater. It was also found that careful dispersion of the C-S-H seed in the mix water further improves the early hydration heat development, but has no effect on the compressive strength. This work furthers the understanding of the early hydration behavior of slag paste and the effects of C-S-H seeding.