Carbendazim-clay complexes for its potential use as antimicrobial additives in mortars

Mortars containing biocidal chemicals are widely applied as they show resistance to microbiological growth, thus preventing the aging of heritage materials. However, factors such as ultraviolet radiation, the weather etc. could greatly affect the biocidal activity of the active principles in mortars. The aim of this study was to optimize the preparation of several complexes of the biocide carbendazim (CBZ) with clays: natural Wyoming montmorillonite SWy-1 and two commercial organoclays, Cloisite (R) 10 and Cloisite (R) 20, and to test their antimicrobial activity for their potential application in restoration mortars. The optimized material here proposed would minimize the amount of active principle needed avoiding its leaching and consequently reducing its environmental impact with a maximum heritage compatibility. Prepared organoclay-CBZ adsorption complexes were inoculated with microorganisms (algae and fungus) to assess the antimicrobial activity. In this sense, one of the CL20-CBZ adsorption complexes which showed the best algicidal and fungicidal activity was used to prepare the antimicrobial mortar, and subsequently compared to those with pure CBZ as an antimicrobial additive. Furthermore, the mortars specimens were subjected to a standardized leaching test to check the effectiveness of the antimicrobial activity. After the leaching tests, the antimicrobial action of mortar containing only CBZ was lower compared to CL20-CBZ which had a good antimicrobial effect. We can conclude from these results that the heritage lime mortars could be easily prepared and have good efficiency against microbial contamination.