abstract
Layered double hydroxides (LDHs) have gained attention in the concrete research field, appearing as prospective additives for controlling chloride attack, and as micro or nano deliverers of corrosion inhibitors. This work reports the effect of ZnAl-NO2 LDH on the evolution of chloride concentration in the pore solution and on the corrosion resistance of iron in mortar samples exposed to 3.5 % NaCl solution. To this end, Ag/AgCl sensors were used to monitor the ingress of chloride ions into mortar, while the electrochemical state of the iron was evaluated by electrochemical impedance spectroscopy. Furthermore, the mortars were analyzed by XRD and TGA, and the total amount of chloride was measured with a commercial sensor. Mortars with LDH showed a slower increase of chloride ions in the pore solution and the preservation of the passive state of the Fe. The presence of LDHs did not cause a significant structural change in the mortars, which was evidenced by the similar distribution of the high frequency resistance as a function of depth in the samples with and without the additive. Finally, the amount of bound chloride in the cementitious material was higher in the LDH-containing mortars. In conclusion, ZnAl-NO2 LDH exhibited a positive effect on the protection of reinforcement embedded in mortar samples when subjected to chloride ingress.
keywords
LAYERED DOUBLE HYDROXIDES; AL-27 MAS NMR; OF-THE-ART; FRIEDELS SALT; CORROSION-INHIBITORS; CONCRETE; STATE; STEEL; ENHANCEMENT; RESISTANCE
subject category
Construction & Building Technology; Engineering
authors
Sampaio, RS; Gomes, C; Bastos, AC; Ferreira, MGS
our authors
António Alexandre Cunha Bastos
Assistant Researcher
Mário Guerreiro Silva Ferreira
Retired Professor
Rui Miguel da Silva Sampaio
PhD StudentProjects
Long Lasting reinforced Concrete for Energy Infrastructure under Severe Operating (LORCENIS)
CICECO - Aveiro Institute of Materials (UIDB/50011/2020)
CICECO - Aveiro Institute of Materials (UIDP/50011/2020)
Associated Laboratory CICECO-Aveiro Institute of Materials (LA/P/0006/2020)
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 n degrees 685445) and developed within the scope of the project CICECO-Aveiro Institute of Materials, UIDB/50011/2020, UIDP/50011/2020 & LA/P/0006/2020, financed by national funds through the FCT/MEC (PIDDAC) . A.C. Bastos is funded by national funds (OE) , through 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.