Nano and mesoscopic SiO2 and ZnO powders to modulate hydration, hardening and antibacterial properties of portland cements

Abstract

In this study we have utilized silica nano powder (SP) and ZnO mesoscopic powder (ZP), obtained by a sol-gel method, to improve cements. SP and ZP were mixed in various amounts with portland cements and their influence on the hydration-hardening processes and the antibacterial properties of the resulting cement was further assessed.The obtained results demonstrated that cement-based materials could be improved in terms of antimicrobial efficiency when modified with bioactive ZP, as demonstrated in Gram-positive and Gram-negative opportunistic bacteria, but also in yeasts.The addition of ZP to portland cement and pastes, determined an important delay of the portland cement hydration and hardening processes, as resulted from the XRD, FTIR, TG-DTA analyses and compressive strength test performed on mortars hardened up to one year. Silica nano powder had an opposite effect i.e. for an adequate dosage improved the mechanical strengths of portland cement mortar due to physical and chemical effects determined on cement hydration and hardening processes. These results highlight the role of ZP in improving key features of cements which could be further exploited to obtain smart materials, such as self-cleaning and antibacterial portland cements.