Effect of layered double hydroxides on the calcium leaching of cement pastes

This work investigated the effect of layered double hydroxides (LDHs) on the calcium leaching of cement pastes. The mass loss, porosity, leaching depth, compressive strength, and Vickers hardness were applied to evaluate the resistance to calcium leaching. Electrochemical impedance spectroscopy, X-ray diffraction, thermogravimetric analysis, scanning electron microscopy, and mercury intrusion porosimetry were conducted to investigate changes of cement hydrates and microstructure in cement pastes. The results demonstrate that the resistance to calcium leaching improves with increasing the content of LDHs and calcined LDHs (C-LDHs), and C-LDHs perform better resistance than LDHs. It is due to the filling effect of LDHs and C-LDHs in cement pastes. Additionally, they promote cement hydration, increasing the content of cement hydrates. As a result, LDHs and C-LDHs decrease the porosity and refine the pore structure, increasing the resistance to calcium leaching.