Measuring chemical shrinkage of ordinary Portland cement pastes with high water-to-cement ratios by adding cellulose nanofibrils

Abstract

Chemical shrinkage is an important way to study the hydration kinetics of cement. However, the measurement of chemical shrinkage for cement pastes with high water-to-cement ratio (w/c) faces a significant bleeding issue. This study demonstrates the use of cellulose nanofibrils (CNF) to create a stable structure that can support cement particles and let them be hydrated without settling. The measured chemical shrinkage curves for the 0.5 w/c cement pastes with and without CNF are very similar at early ages (e.g., 3 d), which implies that the chemical effect of CNF on cement hydration is small in the short term; therefore, the use of CNF allows study of chemical shrinkage for high w/c cement pastes at the early ages. The results show that with the increase of w/c, the main hydration peak is delayed and the post-peak stage is prolonged. In the long term (e.g., after 3 days), the measured chemical shrinkage for high w/c is higher than the low w/c. Similarly, the degree of hydration curves show that, with more water, cement hydration is eventually much enhanced.