Suchergebnisse

As a consequence of human activities, today, we are exposed to high pollution levels that cause building materials damage and many diseases. The application of TiO2 as coating on building materials has proven the efficiency of self-cleaning and air de-pollution. However, its performance is limited due to its absorption being exclusively located at UV light. In this study, Cu-TiO2 photocatalysts were integrated into silica sol-gel synthesis to manufacture new long-lasting term coatings with self-cleaning and air purification properties for concretebased building materials. The enhancement of TiO2 photoactivity by incorporating Cu into its network has been clearly demonstrated. The self-cleaning and air de-polluting efficiency were assessed using methylene blue (MB), soot and NO, respectively, indicating that the presence of Cu promotes the TiO2 performance. For low doping levels, by increasing the copper loading, the TiO2 photoactivity increased. The highest efficiency was obtained by the photocatalyst containing 5% copper, which shows maximum destruction of methylene blue and soot of 95% and 50% within 60 min and 168 h of irradiation, respectively. However, higher copper loading led to a decrease in its performance, reaching a total degradation of MB and soot of 90% and 45% after 60 min and 168 h of irradiation, respectively, for the sample containing 15% of copper loading. ; This work has been supported by the Spanish Government/FEDEREUMAT2017-84228-R, MINECO/AEI/FEDER/UE) and PID2020115843RB-I00/AEI/10.13039/501100011033. This work has been cofinanced by the European Union under the 2014-2020 ERDF Operational Programme and by the Department of Economic Transformation, Industry, Knowledge, and Universities of the Regional Government of Andalusia. Project reference: FEDER-UCA18-106613. We want to thank Margarita Carballido, Mercedes Marquez and Sergio Moreno to facilitate the real exposure of the samples.

A self-cleaning nanostructured TiO2 coating has demonstrated the capacity to mitigate undesired effects from air pollution. Not only it reduces the deterioration of building materials but may also prevent certain pollution-related human health problems. In this study, mesoporous TiO2/SiO2 photocatalysts were synthesized in order to produce self-cleaning and long-lasting coatings that meet the necessary requirements for outdoor applications. The synthesized products were sprayed on concrete substrates and their self-cleaning and air depolluting capabilities were evaluated. The former one as a function of methylene blue (MB) and soot degradation and the latter, according to nitrogen oxides reduction. The coatings proved to have high photocatalytic activity, and their efficiency was enhanced as TiO2 loadings were increased. Thus, after the first 60 min of their irradiation by UV–vis light, the photocatalysts ST1 and S4T had removed 79% and 95% of the MB, respectively. These coatings presented particulate surfaces that provided more surface area and porosity, which are key factors for a high photocatalytic activity. Moreover, the same samples after 104 h of irradiation exhibited 38% and 49% conversion of total NO, respectively. While E503, a commercially available photocatalyst, produced coating cracked surfaces and a total MB degradation of just 50% after 60 min of irradiation as well as 35% of NO conversion after 104 h of irradiation. The TiO2/SiO2 coatings' photocatalytic efficacy remained practically invariable after four months of exposure to real-life conditions and three MB degradation cycles. After the outdoor durability tests, the coated surfaces exhibited a practically unchanged structure, which confirms their long-lasting efficiency. © 2022 The Authors ; This work has been supported by the Spanish Government MAT2017-84228-R (MINECO/AEI//FEDER, UE) and PID2020- 115843RB-I00/AEI/10.13039/501100011033 . This work has been co-financed by the European Union under the 2014–2020 ERDF Operational Programme and by the Department of Economic Transformation, Industry, Knowledge, and Universities of the Regional Government of Andalusia . Project reference: FEDER-UCA18-106613 .

This manuscript presents a 1 year in the laboratory and 3 years In-Situ evaluation of an alkoxysilane-based consolidant containing SiO2 nanoparticles (SiO2NPs) on Ostionera stone, a biocalcarenite traditionally employed in Southwestern Spain. C ' adiz Roman Theatre was selected for In-Situ application and testing. In order to safeguard the theatre, preliminary laboratory experiments were carried out. Firstly, the compatibility and the effectiveness of the consolidant product were evaluated in the laboratory, demonstrating that the incorporation of SiO2NPs improves drying time and consolidant effect. Subsequently, the consolidant was applied In-Situ and the long-term performance was monitored over 3 years through non-destructive tests. The treatment exhibit moderate incompatibility degree (6.1) and demonstrating the long-lasting performance of the SiO2NPs-based consolidant treatment. ; 1 This work has been supported by the Spanish Government MAT2017-84228-R (MINECO/AEI//FEDER,UE) and PID2020-115843RB-I00/AEI/10.13039/501100011033. This work been cofinanced by the European Union under the 2014-2020 ERDF Operational Programme and by the Department of Economic Transformation, Industry, Knowledge, and Universities of the Regional Government of Andalusia. Project reference: FEDER-UCA18-106613. Giada M.C. Gemelli would also like to thank the Spanish Government for her predoctoral grants (PRE2018-085799). We thank the Cadiz Roman Theatre staff and Manuel Luna for their collaboration.

Water and waterborne decay agents (e.g. salts, microorganisms) are commonly associated with undesired alterations and damages on concrete elements. A strategy to mitigate their impact is to decrease water retention in the material either by surface treatments or admixtures. In this work, hydrophobic concretes were developed by the addition of a hydrophobic sol containing TEOS and PDMS oligomers, synthetized by a surfactant-assisted sol-gel route, either as an admixture or as a surface treatment. The hydrophobic performance was similar for both application modes (>70% capillary absorption reduction) and higher than concrete containing a commercial (calcium stearate) admixture or a nanosilica-based hydrophobic coating. Addition as an admixture led to a higher durability in the rain and abrasion tests. The hydrophobic sol as an admixture promotes an increase of surface roughness and porosity, as well as the formation of C–S–H like reaction products with the cement matrix components, as evidenced by AFM, MIP, SEM and FTIR. Despite the higher porosity, impact resistance and material cohesion were not negatively affected respect to the plain concrete. Application as a surface treatment decreased porosity and led to a higher amorphous SiO2 content. The material cohesion and impact resistance was increased by this application, although penetration was limited to the first 4 mm and the hydrophobic properties were more susceptible to mechanical damages to the surface. © 2021 The Authors ; This project has received funding from the European Union's Horizon 2020 - Research and Innovation Framework Programme under grant agreement No 760858; This work has been financed by the Spanish State Research Agency R&D program 2020 (Project reference: PID2020-115843RB-I00); This work has been co-financed by the European Union under the 2014-2020 ERDF Operational Programme and by the Department of Economic Transformation, Industry, Knowledge, and Universities of the Regional Government of Andalusia (Project reference: FEDER- UCA18-106613).