abstract
This work investigated the use of ZnAl-layered double hydroxide (LDH) intercalated with nitrate or nitrite ions for controlling the corrosion of steel in reinforced concrete. The work started by analyzing the stability of the powder in the 1-14 pH range and the capacity for capturing chloride ions in aqueous solutions of different pH. The effect of the ZnAl-LDH on the corrosion of steel was studied in aqueous 0.05 M NaCl solution and in mortars immersed in 3.5% NaCl. It was found that the LDH powders dissolved partially at pH > 12. The LDH was able to capture chloride ions from the external solution, but the process was pH-dependent and stopped at high pH due to the partial dissolution of LDH and the preferential exchange of OH- ions. These results seemed to imply that ZnAl-LDH would not work in the alkaline environment inside the concrete. Nonetheless, preliminary results with mortars containing ZnAl-LDH showed lower penetration of chloride ions and higher corrosion resistance of the steel rebars.
keywords
ACTIVE CORROSION PROTECTION; MODIFIED HYDROTALCITES; CARBONATION RESISTANCE; CHLORIDE-BINDING; ORGANIC-ANIONS; STEEL; INHIBITOR; INGRESS; IONS
subject category
Materials Science
authors
Gomes, C; Mir, Z; Sampaio, R; Bastos, A; Tedim, J; Maia, F; Rocha, C; Ferreira, M
our authors
António Alexandre Cunha Bastos
Assistant Researcher
João Tedim
Associate Professor
José Celestino Vieira Gomes
PhD Student
Mário Guerreiro Silva Ferreira
Retired Professor
Rui Miguel da Silva Sampaio
PhD StudentProjects
Long Lasting reinforced Concrete for Energy Infrastructure under Severe Operating (LORCENIS)
acknowledgements
This work was funded by the HORIZON 2020 collaborative project LORCENIS (Long Lasting Reinforced Concrete for Energy Infrastructure under Severe Operating Conditions, Grant agreement no 685445) and within the scope of the project CICECO-Aveiro Institute of Materials-UIDB/50011/2020 and UIDP/50011/2020-Financed by national funds through the FCT/MEC and when appropriate co-financed by FEDER under the PT2020 Partnership Agreement. AB acknowledges FCT-Fundacao para a Ciencia e a Tecnologia, I.P., in the scope of the framework contract foreseen in the numbers 4, 5, and 6 of the article 23, of the Decree-Law 57/2016, of August 29, changed by Law 57/2017, of July 19. ZM thanks COST action 15202 for a Short Term Scientific Mission to the University of Aveiro.