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Modified hydrotalcites as chloride scavengers and inhibitor release agents for improved corrosion protection of reinforced concrete

Zhengxian Yang1, R.B. Polder2,3, J.M.C. Mol4

1 College of Civil Engineering Fuzhou University, Fuzhou, Fujian 350116, China
2 Section of Materials and Environment, Faculty of Civil Engineering and Geosciences, Delft University of Technology, P.O. Box 5048, 2600 GA Delft, the Netherlands
3 TNO Structural Reliability, P.O. Box 155, 2600 AD Delft, the Netherlands
4 Department of Materials Science and Engineering, Faculty of Mechanical, Maritime and Materials Engineering (3mE), Delft University of Technology, Mekelweg 2, 2628 CD Delft, the Netherlands

Owing to the unique molecular structure and high ion exchange capacity, hydrotalcites are believed to have a potential to be modified and tailor-made as an active corrosion protective component of reinforced concrete. In this paper, two types of modified hydrotalcites (MHT-pAB and MHT-NO2) were tested both in alkaline solution and mortar for their possibilities as chloride scavengers and inhibitor release agents for application in concrete. The test in alkaline solution showed that ion exchange occurred between free chloride ions in solution and the intercalated inhibitive anions in the MHTs. The results in mortar validated that MHTs could be promising alternatives for preventing chloride-induced corrosion when an appropriate dosage is adopted and applied in a proper way, in particular, either incorporation of a certain amount (MHT-pAB to replace 5% weight of cement) in the bulk mortar or as a coating of the reinforcing steel (MHT-pAB or MHT-NO2 at 20% weight of cement).

Key words: Modified hydrotalcites, chloride, concrete, corrosion, inhibitors