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What is photocatalysis? How can it be used for sanitizing purposes? Is it active against viruses? We take stock of it by updating it to the pandemic situation created with the outbreak of COVID-19 due to the coronavirus SARS-CoV-2. A short report of how surfaces and construction products can be functionalized to obtain effective results to improve the environment in which we live is made. : After a brief description of what a virus is, we will describe the photocatalysis and the possible mechanisms that trigger with it, for the degradation of microorganisms. Then, some currently available technical and commercial solutions (materials and devices) will be explained. Finally, an overview of existing standards on photocatalysis is also given. : Based on the literature analysed, it seems clear that photocatalysis is an effective solution for the initial inactivation and the following degradation of viruses, provided that there are adequate light (irradiation) conditions, favourable environmental conditions (temperature, relative humidity) and suitable type/quantity of photocatalyst capable of interacting and accelerating the chemical-physical processes needed for the purpose. : This provides the opportunity to use new disinfectants in public environments, such as public toilets, schools, hospitals, stations, airports, hotels, shopping centers, or public transportation, which are ideal places for the transmission of pathogens.

This paper deals with the results of two environmental monitoring campaigns entailing the analysis of NOx levels registered before and after the renovation work of the “Umberto I” tunnel in Rome, Italy. The results of the data collection highlighted an efficient abatement of pollutants by the photocatalytic treatment of the tunnel vault with a cement-based paint, as evidenced through the lower concentrations found after the renovation. A NOx reduction of about 20% was calculated in the center of the tunnel (as an absolute comparison between the two periods), whereas a NOx reduction of over 50% was calculated in the same position, considering the reference data registered in the official stations of the city of Rome (Official Environmental Agency – ARPA). The duration of the monitoring campaigns performed seems to be considered significant from the statistical point of view, unlike all previous experiments which were carried out on the photocatalytic materials. This renovation project can prove out to be a very useful reference for the wide program for a sustainable upgrading of tunnels in Europe, according to the Directive 2004/54/EC on road tunnel safety.

Innovative cement-based premix products for surface coating of buildings that possess photocatalytic activity arouse great interest because of the results they can achieve in reducting air pollution and maintaining aesthetics. This photoactivity is induced by a photocatalyst, titanium dioxide, that can accelerate the oxidation processes of air pollutants, particularly nitrogen oxides and volatile organic compounds, which are mainly produced by incomplete combustion of fuel and are present in urban environments through the exhaust gases of motor vehicles. Surfaces that are coated with these products acquire a self-cleaning characteristic (maintenance of original color) because the decomposition of organic compounds significantly reduces the ability of atmospheric particles to adhere to treated surfaces, thus facilitating their removal and ensuring a more durable color. These products are particularly suited for use in highly congested areas (i.e., historical centers of cities, tunnels, roads), where air pollution reaches significant levels. This study describes the photocatalytic performances of a series of premix products containing mineral pigments. The tested products are based on hydraulic binders (natural hydraulic lime and cement), and the pigments are inorganic. A wide range of colors was chosen, and the performances of base products were investigated to provide a wider choice to the designers. After a brief introduction of the principles of photocatalysis, the results of a wide experimental work are described. Some consideration of methods of curing and natural exposure is also reported.

In this paper, the rheological properties of an extrudable cement-based paste are investigated by means of an original ram extrusion apparatus (capillary rheometer). The experimental results indicate that a careful measurement of the die pressure is necessary to obtain a realistic viscosity vs shear rate curve, as required in extrusion technology. In particular, it is shown that the optimal test configuration is when the pressure measurement is made directly inside the rheometer die. By applying this rheological methodology in steady-state conditions, it has been observed that the extrudable cement-based material here evaluated obeys to a simple power–law equation, in the range of shear rates investigated, which are suitable for an industrial extrusion process.

This paper presents the results of a study on the freeze-thaw durability and deicer salt scaling resistance of particular non-air-entrained very high strength cement-based materials. Variables investigated were the microsilica content (0, 10, and 20% by weight), as replacement of an equal amount of cement, and a different quantity of randomly dispersed steel microfibers (0, 2, 4% by volume). Very little research has been undertaken regarding this subject, and these materials are normally considered to be frost resistant because of their intrinsically low porosity. In addition to standard durability tests, compression and bending experiments have been conducted in order to compare the strength and the global response of both reference and freeze-thaw specimens. Tests confirmed the very good behavior of all compositions considered, even those containing high percentages of microsilica and high volume contents of steel microfibers.

The effects of steel micro-fibre on the complete load-displacement response of a high performance concrete in tension and compression were examined from tests performed on specimens composed of high strength concrete under controlled strain through a closed-loop system. The concrete had a maximum aggregate size of 3 mm, an aggregate to binder ratio of two, silica fume to binder ratio of 0.2, water to binder ratio of 0.225 and randomly dispersed steel micro-fibres of 0%, 2%, 4% and 6% by volume. Uniaxial tensile tests, bending tests and uniaxial compressional tests were conducted and analyzed in order to provide a mechanical characterization of the materials. Moduli of elasticity and fracture energies were evaluated and compared.