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

• DOI: 10.1016/j.cemconcomp.2020.103625
• Publication Date: 2020-04-17T01:36:56Z
• Authors: Zhidong Zhang; George W. Scherer
• Keywords: Shrinkage

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.