Alina Melinescu

The paper presents experimental results regarding the valorization of construction and demolition waste and fly ash in rendering mortars based on Portland cement and lime. The binder was partially replaced (50 wt.%) with concrete waste and/or fly ash, while the natural aggregate (quartz sand) was completely substituted with recycled aggregate consisting of brick and concrete waste obtained from demolition activities. This replacement led to a reduction in mortar mechanical strength, while increasing the capillary water absorption coefficient. However, mortars containing fly ash exhibited the lowest water absorption coefficients among the waste-containing formulations and the smallest reduction in mechanical performance. The color differences observed among the individual raw materials were substantially reduced after their incorporation into the mortars. Following accelerated carbonation, all mortars showed good anti-adherent capacity against C. albicans, S. aureus and E. coli, mainly associated with their residual alkalinity, while porosity-related effects on microbial colonization were limited. Overall, the results demonstrate the feasibility of producing rendering mortars incorporating high levels of construction and demolition waste as binder and aggregate replacements, while maintaining acceptable mechanical, colorimetric, and antimicrobial performance, thus supporting resource conservation and circular economy principles in the construction sector.

In this study, the photocatalytic effect of TiO₂ (1 wt. % and 3 wt. %) deposited on the surface of sintered cathode ray tube glass was examined, as well as its effect on an E. coli strain (BL21(DE3)). DTA analysis indicated the sintering temperature for samples to be 820 °C while scanning electron microscopy (SEM)showed an intimate contact and a strong interface between the support and photocatalyst. Near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) was employed to establish the chemical and bonding environment of the samples. The investigations of the bacterial viability were conducted using flow cytometry, a specific cellular viability assay, while bacterial growth was measured using the turbidimetric method. The experimental results show the influence of the TiO₂ concentration on the bacterial inactivation process: higher concentrations (3% wt.) have a bactericidal effect in the long term, whereas lower concentrations (1% wt.) render them inactive for a shorter time in the exponential growth stage. The preliminary results were used to calculate the efficiency of microbial inactivation and the parameters of the kinetics of inactivation using ANOVA software. The results indicate that this material could be an effective solution for water disinfection.