Synthesis and characterization of modified hydrotalcites and their ion exchange characteristics in chloride-rich simulated concrete pore solution

Two modified hydrotalcites (MHTs) intercalated with nitrate and aminobenzonate anions, (i.e., CaAl-MHT-NO3 and CaAl-MHT-pAB) have been synthesized. The intercalation of CaAl-MHT-pAB was achieved by anion exchange of nitrate in the host material, CaAl-MHT-NO3, which was prepared by a coprecipitation method. Materials characterization was conducted by means of X-ray diffraction (XRD), thermal analysis, IR-spectroscopy and environmental scanning electron microscope (ESEM). Element analysis further confirmed both nitrate and p-aminobenzonate anions were successfully intercalated into the interlayer space of MHTs with an intercalating ratio of 81.2% and 33.1% respectively. Volhard’s titrimetric analysis demonstrated that ion exchange occurred between free chlorides in simulated concrete pore solution and anions intercalated in MHTs. The preliminary results reported in this paper shed light on the promising use of MHTs as a new type of additive for improved corrosion protection of reinforced concrete.