The Influence of Selected Material Variables of Photocatalytic Cementitious Composites on the Self-Cleaning Properties and Air Purification Efficiency from NOx Pollutants

Abstract

This work aimed to investigate the influence of selected material variables on the self-cleaning and air purification efficiency in NOx pollutants of cement-based photocatalytic composites. Tests were performed on cement mortars, with seven independent variables considered: the mass ratio between cement and quartz powder to sand, the water to cement ratio, the total mass amount of photocatalysts (two different types), the mass content of nanoparticulate silica, the percentage of quartz powder replacing part of cement, and the ratio between two sands of fine granulation. Photocatalytic cementitious materials had their self-cleaning properties tested via two methods (spectrophotometry—the degradation of rhodamine B under UVA irradiation, and the change in the contact angle—via a goniometer). Air purification properties were tested in the reaction chamber under UVA and visible light at low irradiance (0.2 W/m2 for UVA, 150 W/m2 for visible). It was found that TiO2 content and the mass ratio between cement and quartz powder to sand were the most influential variables within the selected ranges of variability, with the ratio between sands and quartz content being the least significant variable of the tested properties.

The Potential Risk of Nanoparticulate Release from Photocatalytic Pavement Concrete Surface Due to a Simulated Abrasion Load—An Experimental Study

“…Although exposed to an external load, TiO 2 grains contributed to increased resistance of the near-surface layer of the composite, suggesting its influence over cement matrix organization and structure. The effect of photocatalytic modifications is usually investigated in terms of the ability of the composite to either decompose gaseous pollutants [ 52 ] (organic and inorganic—nitrogen oxides, ozone, aromatic hydrocarbons, and others) or through self-cleaning tests (decomposition of different organic dyes under exposure to electromagnetic radiation of a specific wavelength and irradiation—the rhodamine b test, for instance [ 19 ]). Those test procedures assume verification of the surface properties—the quality and the concentration of TiO 2 embedded in the outer surface of the element.…”

“…Its specific surface area was measured via the Blain method and equaled 3920 cm 2 /g. The micro-silica used in the study (Łaziska, Poland) met the requirements of EN 13263-1 [ 32 ] and consisted of the properties presented in [ 19 ]. The BET method measured its specific surface area, which was 23.86 m 2 /g.…”

“…shift bands from valance to conduction, forming electron holes. This phenomenon initiates various reduction–oxidation processes caused by the creation of hydroxyl radicals and superoxide radicals, allowing for the decomposition/conversion of various gaseous pollutants [ 19 ]. Considering the use of photocatalytic cementitious composites as a pavement material for roads, sidewalks, and other surface types exposed to solar radiation, their main potential lies in reducing the photochemical pollution caused by urban traffic—mainly nitrogen oxides, near-surface ozone, and aromatic hydrocarbons [ 6 , 20 ].…”

Significance of Vibration Time in Developing Properties of Precast Pervious Concrete

“…Pervious concrete can be characterized by properties unknown in regular concrete technology [ 44 ]. With increased porosity, which forms an open network throughout the composite, a dynamic flow of fluids can occur, allowing for pervious concrete’s use as a permeable material for many different applications—as a much bigger area of concrete is exposed to the conditions of external environment than in the case of regular concrete, this type of cementitious material can be used for water management issues [ 45 ] as well as for air purification passive systems by inclusion of photocatalytic materials in concrete’s structure [ 46 , 47 ]. As the aforementioned flow occurs, part of the volume of pervious concrete is not filled with aggregate or cement matrix.…”

TiO2-Based Mortars for Rendering Building Envelopes: A Review of the Surface Finishing for Sustainability

“…In fact, the benefits of incorporating TiO 2 in buildings can even be assessed from the climate change perspective since its mitigation mainly depends on reducing the emission of greenhouse gases [23]. TiO 2 has been studied not only for its ability to reduce CO 2 [24,25] but also its effect on air purification concerning other pollutants, such as nitrogen oxides (NO x ) [26], and the degradation of several organic contaminants [22]. Indeed, the parameters of the façades affect embodied and operational impacts during the life cycle of buildings [27].…”