Search Results (11)

This research investigated the properties of photocatalytic cementitious composites, including their air-purification efficiency. A method of characterizing the removal of airborne pollutants (nitrogen oxides), simulating the actual NO_x concentration and irradiation conditions in Warsaw, Poland, in the autumn/winter season was established. The study analyzed the impact of changes in the composition of cement mortars—partial substitution of the binder with mineral fillers—on the properties of the external photoactive surface of the composite. The designed experimental plan included both quantitative and qualitative variables (type and amount of fillers used). It was found that the photocatalytic performance of the composite was correlated with its pore total content and pore size distribution—the higher the content of mineral fillers, the lower the porosity and the less effective its photocatalytic properties. The selectivity of the photocatalytic NO_x reactions also deteriorated as the content of the mineral fillers increased. The study confirmed the validity of increasing the binder content in cementitious composites to enhance their photocatalytic performance. Full article

This study investigated how the surface characteristics of photocatalytic cementitious composites influenced the effectiveness of air purification from nitrogen oxides (NO_x), with a particular focus on the impact of coarse aggregate exposure on the photoactive surface. Air purification efficiency tests were conducted using a custom-developed procedure that simulated NO_x concentrations and UV irradiance typical of autumn and winter conditions in Warsaw, Poland. The findings revealed that the extent of exposed coarse aggregate on the photoactive surface significantly affected photocatalytic efficiency, reducing the overall NO removal rate by up to 50% compared to the reference value. The use of hydration retarders modified the surface characteristics of the photocatalytic cement matrix, enhancing its photoactive potential. The observed decline in photocatalytic efficiency in composites with exposed coarse aggregate was attributed to the coarse aggregate’s limited ability to retain nanometric photocatalyst particles, which reduced the overall TiO₂ content in the composite’s near-surface layer. Nevertheless, cementitious composites incorporating a first-generation photocatalyst exhibited substantial photocatalytic activity, achieving NO removal rates of up to 340 µg/m²·h for non-exposed variants and up to 175 µg/m²·h for variants with exposed aggregate. These results demonstrated their functionality even under low-intensity UV-A irradiation (1 W/m²), making them suitable for environments with limited sunlight exposure. Full article

In this paper, a new way to obtain photoactive cements was presented. In this method amorphous TiO₂ is added to a cooler during the cooling of the cement clinker (Górażdże company) during cement production. Amorphous TiO₂ was taken from the installation for obtaining titanium dioxide using the sulphate method. During the study, amorphous TiO₂ was added to the clinker at 300, 600, 700, and 800 °C. The properties of the obtained cement were tested during the bending and compressive strength. The initial and the end of setting time was also measured. The adhesion of the obtained materials to concrete block, ceramic brick, and plasterboard were also evaluated. The photocatalytic activity of the obtained materials was studied during NO and BTEX (benzene, toluene, ethylbenzene, p-, m-, o-xylenes decomposition) decomposition. Cement with 5 wt% TiO₂ added to the clinker at 700 °C had the highest photocatalytic activity and the best mechanical properties. Full article

In this study, a new method of obtaining photoactive cements is presented. The goal was to obtain photoactive cements using a method that could reduce the production costs. In the study, an intermediate product from the production of titanium dioxide using the sulfate method, taken from the installation before the calcination process, was used to obtain photoactive cements. Laboratory conditions corresponding to introducing this amorphous TiO₂ into cement clinker during its cooling were simulated. The study shows that the temperature from 300 to 800 °C and the time of amorphous TiO₂ contact with the cement clinker within 30 min is sufficient to obtain a photoactive cement. The highest photocatalytic activity was obtained for the material with 5 wt.% TiO₂ content, and the method used did not cause a significant decrease in the bending and compressive strength of the new photoactive cements. The obtained materials were characterized by determining the crystal size of the TiO₂, the sulfur content and the photocatalytic activity during NO decomposition under UV radiation. The bending and compressive strength were measured. The influence of the addition of photocatalysts on the beginning and end of the setting time was also investigated. Full article

The application of nano-TiO₂ as a photocatalytic agent in buildings’ internal surfaces has recently attracted attention to mitigate microorganism growth, soiling, and contamination in indoor environments. This work aimed at comparing the Rhodamine B (RhB) dye degradation efficiency of three different mortar compositions subjected to simulated internal radiation, in which nano-TiO₂ (10 wt% of binder mass) was dispersed by ultrasonic and mechanical methods. Mortar specimens were produced with white Portland cement, hydrated lime, sand, and water in different volume proportions of 1:1:6 (cement:lime:sand), 1:3 (cement:sand), and 1:4 (cement:sand). The first stage of the research evaluated samples exposed to the natural outdoor environment and proved the efficiency of specimens’ photoactivity when covered by a glass layer. The second and principal phase of the study simulated indoor conditions in glazed buildings through artificial weathering in which the composition of 1:1:6 was mechanically dispersed and exhibited the highest global color change (ΔE) values for RhB staining. The main finding of the study was that the mortars exposed to simulated indoor conditions presented high ΔE grades, classified as easily perceived by the human eye. This demonstrates the photocatalytic efficiency in an internal building environment that receives radiation through a glass surface. Full article

Photocatalytic coatings based on TiO₂ nanoparticles have been applied to building materials over the past few decades, following encouraging results obtained by many laboratory studies and a few onsite testing campaigns showing their self-cleaning, antimicrobial and depolluting performance. However, these results clearly point out the need for a deeper understanding of the effectiveness of TiO₂-based treatments when applied over different substrates and their durability when exposed to an outdoor environment. The present paper investigates the behavior of a nanodispersion of titania nanoparticles applied to cement-based substrates. Cementitious materials are widely used in building façades, roofs, structures, roads and tunnels; hence, any improvement in their performance and/or the introduction of new and unique functionalities have potentially a very high impact on everyday life. A TiO₂ nanodispersion was applied by brushing and spraying on three cement-based substrates (a render, a prefabricated board and a painted prefabricated board), investigating its photocatalytic activity. Then, the samples were subjected to two artificially weathering procedures, involving rain washout and UV light exposure, and the changes in terms of the photocatalytic activity and contact angle were measured. The results suggest that the nature of the substrate plays a key role in the performance of the coating and that weathering has a significant impact too. Full article

This article presents a short overview of modified cements with photocatalytic activity. First, the types and three main methods of obtaining photoactive cements are presented. The most frequently used modification method is the incorporation of a photocatalyst into the total mass of the cement. The second group analyzed is cements obtained by applying a thin layer of photoactive materials, e.g., paints, enamels, or TiO₂ suspensions, using various techniques. The third group is cement mortars with a thick layer of photoactive concrete on the top. In addition, methods for determining the photoactivity of cement composites, mechanical properties, and physicochemical parameters of such materials are briefly presented. Finally, examples of investments with the use of photoactive cements and development prospects are shown. Full article

The studies of some mechanical properties and photocatalytic activity of new cements with photocatalytic activity are presented. The new building materials were obtained by addition of semi-product from titanium white production. Semi-product was calcined at 300 and 600 °C for one, three, and five hours and then this material was added to cement matrix in an amount of 1 and 3 wt.%. New materials were characterized by measuring the flexural and compressive strength and the initial and the final setting time. The photocatalytic activity was tested during NOx photooxidation. The cement with photocatalytic activity was also characterized by sulphur content measurements. The measurement of reflectance percentage of TiO₂-loaded cements in comparison with pristine cement and TiO₂ photocatalyst calcined at 600 °C were also performed. It should be emphasized that although in some cases, the addition of photocatalyst reduced the flexural and the compressive strength of the modified cements, these values were still within the norm PN-EN 197-1:2012. It was also found that the initial and the final setting time is connected with the crystal size of anatase, and the presence of larger crystals significantly delays of the setting time. This was probably caused by a water adsorption on the surface of anatase crystals. Full article

Geopolymers are ecologically-friendly inorganic materials which can be produced at low temperatures from industrial wastes such as fly ash, blast furnace slags or mining residues. Although to date their principal applications have been seen as alternatives to Portland cement building materials, their properties make them suitable for a number of more advanced applications, including as photocatalytic nanocomposites for removal of hazardous pollutants from waste water or the atmosphere. For this purpose, they can be combined with photocatalytic moieties such as metal oxides with suitable bandgaps to couple with UV or visible radiation, or with carbon nanotubes or graphene. In these composites the geopolymers act as supports for the photoactive components, but geopolymers formed from wastes containing oxides such as Fe₂O₃ show intrinsic photoactive behaviour. This review discusses the structure and formation chemistry of geopolymers and the principles required for their utilisation as photocatalysts. The literature on existing photocatalytic geopolymers is reviewed, suggesting that these materials have a promising potential as inexpensive, efficient and ecologically-friendly candidates for the remediation of toxic environmental pollutants and would repay further development. Full article

In this paper, studies of the mechanical properties and photocatalytic activity of new photoactive cement mortars are presented. The new building materials were obtained by the addition of 1, 3, and 5 wt % (based on the cement content) of nitrogen-modified titanium dioxide (TiO₂/N) to the cement matrix. Photocatalytic active cement mortars were characterized by measuring the flexural and the compressive strength, the hydration heat, the zeta potential of the fresh state, and the initial and final setting time. Their photocatalytic activity was tested during NOx decomposition. The studies showed that TiO₂/N gives the photoactivity of cement mortars during air purification with an additional positive effect on the mechanical properties of the hardened mortars. The addition of TiO₂/N into the cement shortened the initial and final setting time, which was distinctly observed using 5 wt % of the photocatalyst in the cement matrix. Full article

In this study, mortar specimens were prepared with a cement:sand:water ratio of 1:3:0.5, in accordance with standard EN196-1. Portland CEM I 52.5 R grey (G) and white (W) cements were used, together with normalised sand and distilled water. Different amounts of TiO₂ photocatalyst were incorporated in the preparation of the mortar samples. The effect of the addition of TiO₂ was studied on mechanical properties of the mortar and cement including compressive and flexural strength, consistency (the flow table test), setting time and carbonation. Characterization techniques, including thermogravimetry, mercury porosimetry and X-ray diffraction spectroscopy (XRD), were applied to study the physico-chemical properties of the mortars. It was shown that adding the photocatalyst to the mortar had no negative effect on its properties and could be used to accelerate the setting process. Specimen photoactivity with the incorporated photocatalyst was tested for NOx oxidation in different conditions of humidity (0% RH and 65% RH) and illumination (Vis or Vis/UV), with the results showing an important activity even under Vis radiation. Full article