Effect of synthesis conditions and post-synthetic treatments of LiAl-LDH on the performance of sulfoaluminate cement

LiAl-layered double hydroxide (LiAl-LDH) has been reported as a potential hardening accelerator of calcium sulfoaluminate (CSA) cement. Until now, little has been known about the effect of synthesis conditions and post-synthetic treatments of LiAl-LDH on the performance of CSA cement. The present work shows two methods for the synthesis of LiAl-LDH – a solvothermal method and a separate nucleation and aging steps method (SNAS) – and two methods for the post-synthetic treatments of LiAl-LDH, with and without drying process. The effect of the resultant LiAl-LDH on the performance of CSA cement was studied in relation to the strength, hydration process and products. Results indicate that specimens containing LiAl-LDH showed a greatly enhanced performance with regard to setting time and compressive strength at early and later ages. Compared to LiAl-LDH prepared with the solvothermal method, LiAl-LDH from SNAS synthesis is more effective to increase the compressive strength and shorten setting time. Moreover, the post-synthetic treatments affect the performance of LiAl-LDH. LiAl-LDH without a drying process has better dispersion stability, higher compressive strength and a shorter setting time. Owing to the crystal seed effect, LiAl-LDH enhanced the hydration rate and improved the amount of hydration products, resulting in a higher compressive strength.