Effects of nitrite ion intercalated CaAl and MgAl layered double hydroxides on the properties of concrete mortar

Nitrite ion intercalated Ca-Al and Mg-Al layered double hydroxides (LDHs) had been successfully synthesized by two modified methods in order to improve intercalation rate of nitrite ion and the effects of the obtained LDHs on the mechanical properties, anticorrosion properties of concrete mortar were discussed. The results revealed that two kinds of LDHs exhibited the improved crystallinity and uniform morphology, and Ca-Al LDH synthesized by hydrothermal method (H-C-LDH) exhibited better properties. The intercalated LDHs had different degrees of improvement in the mechanical properties, chloride penetration resistance and permeability resistance of cement mortars without apparent decline in the fluidity, especially for 2% H-C-LDH sample. Electrochemical tests also showed that the intercalated LDH led to a more positive potential and larger charge transfer resistance, and H-C-LDH sample expressed the best corrosion resistance. The exchanged ions and X-ray diffraction (XRD) results confirmed that synthetic LDHs could reduce the corrosion risk of carbon steel by providing physical barrier, chloride ion absorption and inhibitor release.