Effect of LiAl-layered double hydroxides on hydration of calcium sulfoaluminate cement at low temperature

To reveal the effect of LiAl-layered double hydroxides (LiAl-LDHs) on hydration of calcium sulfoaluminate cement at low temperature, pastes with and without it were prepared and cured at temperature -10 degrees C. Setting times and compressive strength of pastes were measured. Mercury intrusion porosimetry (MIP) was used to reveal the evolution of pastes microstructure. X-ray diffraction (XRD), Thermogravimetric analysis (TG) and Al-27 nuclear magnetic resonance (NMR) were adopted to qualify and quantify the hydration productions. The results show that, LiAl-LDHs is an effective hydration accelerator of CSA cement at low temperature. Initial and final setting times are reduced linearly with the increase of LiAl-LDHs content. However, peak of compressive strength emerges at the content of 1.0%. At this content, modified paste achieves 5.5 times compressive strength of plain one at 1 day and 1.4 times at 28 days. In presence of LiAl-LDHs, more ettringite crystallizes in modified pastes up to 28 days. Denser pastes obtained thereby. (C) 2019 Elsevier Ltd. All rights reserved.