Portland Cement Pastes and Mortars with Antibacterial Properties

This paper brings new information regarding the influence of partial replacement of portland cement with nano silica and mesoscopic ZnO powders in terms of mechanical and antimicrobial properties. The experimental results demonstrate a reduced growth of the opportunistic pathogens Staphylococcus aureus, Pseudomonas aeruginosa, and Candida albicans and an alteration of monospecific biofilm formation when exposed to the cement pastes modified with these additions. The coexistence of silica and ZnO powders modifies the kinetics of portland cement hydration and hardening processes, as well as the nature and composition of resulting compounds. While ZnO powder initially delays the hydration and hardening of portland cement, the addition of nano silica helps alleviate this delay and improves the compressive strengths. The main properties (mechanical strengths and antibacterial properties) of the cement pastes and derived composites (mortars) are assessed and statistically processed to identify the optimum dosage of each component. These materials could be of a particular interest for buildings exposed to conditions favoring microbial colonization, especially health-care facilities where the microbial load of antibiotic resistant and biofilm species is high.