Preparation of calcium silicate hydrate seeds by means of mechanochemical method and its effect on the early hydration of cement

Abstract

Calcium silicate hydrate seeding is a promising accelerator for cement hydration. In this work, calcium silicate hydrate nanoparticles with various CaO/SiO 2 -ratios were prepared by means of mechanochemical approach. X-ray diffractometry, scanning electron microscopy and laser granulometry were used to study the properties of the calcium silicate hydrate particles. The evaluation of the effectiveness of calcium silicate hydrate seeds on the cement hydration was conducted by heat flow calorimetry and compressive strength tests using ordinary Portland cement and early strength white cement. Results show that the main crystalline phase in the final product is crystalline calcium silicate hydrate (Ca 1.5 SiO 3.5 ·xH 2 O). An acceleration of 6.08 h or 28.03% on the hydration of P.O 42.5 type Portland cement as well as a 78% increment of compressive strength 24 h after water addition can be achieved using calcium silicate hydrate seeds. Compared to the P.O cement, calcium silicate hydrate nanoparticles are less effective in the P.W white cement, which indicates the nature of the cement is a crucial factor to influence the effectiveness of the calcium silicate hydrate seeds as well.