Search Results (38)

The substantial voids of porous pavement materials permit light and exhaust pollutants to infiltrate to a considerable depth. Consequently, utilizing porous mixtures as carriers for photocatalytic materials enables greater exposure to an environment conducive to the exhaust degradation reaction. This study employed porous asphalt mixtures and porous cement concrete as carriers for photocatalytic pavements. Various amounts of TiO₂ were incorporated as photocatalysts to produce eco-friendly pavement materials with exhaust degradation capability. Based on a self-developed apparatus and methodology, its exhaust degradation performance was evaluated under different preparation conditions and pavement structures. The influences of void ratio, photocatalyst dosage, pavement type, and pavement thickness on the exhaust degradation function were examined. The degradation rates of NO and CO among the four monitored pollutants were observed to follow a three-stage pattern of “slow–fast–steady”, while the degradation rates of NO₂ and HC followed a “fast–slow–steady” pattern. Increasing the void ratio and the photocatalyst dosage yielded similar effects on exhaust degradation efficacy, enhancing the degradation rate and reducing the time required to reach equilibrium. The increase in the void ratio of porous asphalt mixtures and porous cement concrete reduced the time required to reach equilibrium by an average of 4.4 and 2.3 min for the four pollutants monitored, respectively. Increasing the dosage of photocatalytic material by 2 kg/m³ increased NO degradation by an average of 1.5% and reduced the time required to reach equilibrium by an average of 0.8 min. The degradation rate of porous cement concrete in the first reaction stage was faster than that of porous asphalt mixtures, and the time required to reach equilibrium state increased by 2 min compared to that of porous asphalt mixture. And the impact of specimen thickness on exhaust degradation performance was minimal. Full article

Self-cleaning cementitious materials, particularly with TiO₂-based photocatalytic coatings, offer significant benefits by reducing surface deterioration and maintenance requirements, even in harsh urban environments. Despite the growing interest in self-cleaning cementitious materials, an international standard test method to calculate their efficiency has not yet been established for this specific type of substrate. The objective of this study was to evaluate and compare three different techniques for assessing the photocatalytic efficiency (PE) of cementitious materials coated with TiO₂: (i) spectrophotometric colorimetry (SPC); (ii) digital image processing-based colorimetry (DIP); and (iii) UV-Vis spectrophotometry (UV-Vis). Rhodamine B (RhB) was used as a model pollutant, and the photocatalytic efficiency was monitored under UV-Vis light. The results showed that each method has distinct advantages and specific challenges. SPC proved to be a practical and efficient approach, similarly to DIP, which was also accessible, providing reliable and accurate measurements. UV-Vis stood out for its precision but required careful application on cement-based substrates due to their unique porosity and adsorption characteristics. These results underscore the complementary potential of these techniques and highlight the importance of developing standardized protocols that integrate their strengths to facilitate the wider adoption of self-cleaning materials. Full article

One of the most significant global challenges for humans is environmental pollution. The technology to control this problem is the utilization of semiconductors as photocatalysts. In the current study, iron-doped titania nanotubes (Fe/TiNTs) with increased photocatalytic effect were synthesized via a modified hydrothermal method. The products were characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy (TEM), gas adsorption, electron spin resonance (ESR) and UV–Vis diffuse reflectance spectroscopy (DRS). TEM results indicated that Fe/TiNTs have a tubular and uniform structure with an average outer diameter of 23–48 nm and length of 10–15 µm. ESR and DRS revealed that Fe³⁺ ions were successfully introduced into the TiNT structure by replacing Ti⁴⁺ ions. An enhanced light absorption in the range of 400–600 nm additionally indicated successful doping. The band gap was narrowed as iron wt% was increased. The photocatalytic activity was evaluated by the degradation of methyl orange (MO) in the presence of Fe/TiNTs and TiTNs by monitoring the degradation of MO under UV light irradiation. An acceleration on the hydration of Portland cement was observed in the presence of 2.0 wt% Fe/TiNTs. Fe/TiNTs can be used as a nanomaterial in cement-based building materials to provide self-cleaning properties to the surface of concrete even in indoor environments. Full article

Recently, the production of new photocatalytic materials has attracted considerable attention as a promising strategy to mitigate anthropogenic environmental degradation. In this study, cement paste composites (water/cement ratio = 0.5) were prepared using a coating based on nanoparticles of SnO₂ (SnO₂/cement paste) and SnO₂ decorated with Ag₂O (Ag₂O-decorated SnO₂/cement paste) for photocatalytic applications. These coatings were prepared in this study by using the hydrothermal method as the strategy. Thus, photocatalyst efficiency was evaluated through the degradation of methylene blue (MB) and methyl red (MR) as cationic and anionic dyes, respectively, and the simultaneous degradation of MB/MR (1:1 v/v) dyes. Moreover, the photocatalytic mechanism was investigated in the presence of scavengers. Notably, an increase in pH in the range of 2–6 resulted in selective degradation of the MB/MR dye mixtures. Overall, the photocatalytic performance of these materials provides a novel platform technology focused on advanced civil engineering applications, which consequently facilitates the mitigation of various environmental problems. Full article

The development of modern building materials science involves the process of designing innovative materials that exhibit unique characteristics, such as energy efficiency, environmental friendliness, self-healing ability, and photocatalytic properties. This can be achieved by modifying cement with nano- and fine-dispersed additives that can give the material new properties. Such additives include a number of compounds based on the TiO₂-Bi₂O₃ system. These compounds have photocatalytic activity in the near-UV and visible range of the spectrum, which can serve to create photocatalytic concretes. Here, the purpose of this scientific study was to synthesize compounds based on the TiO₂-Bi₂O₃ system using two methods in order to identify the most optimal variant for creating a composite material and determine its properties. Within the framework of this article, two methods of obtaining a photocatalytically active additive based on the TiO₂-Bi₂O₃ system are considered: the solid-state and citrate-based methods. The photocatalytic, mechanical and structural properties of composites containing the synthesized additive are investigated. In this study, it was found that for the creation of photocatalytic concretes, it is advisable to use cement compositions with a bismuth titanate content of 3–10 wt.%. of the cement content, regardless of the method of obtaining the additive. However, the most optimal composition is one containing 5 wt.% of the synthesized additive. It is noted that compositions containing 5% by weight of bismuth titanate demonstrate photocatalytic activity and also show an increase in strength on the first day of hardening by 10% for the solid-state method and 16% for the citrate method. Full article

Environmental pollution is one of the most serious and global problems for humans. Photocatalysis is a promising technology to control environmental pollution via the utilization of semiconductor materials as a photocatalyst. In this study, iron-doped TiO₂ nanotubes (Fe/TiNTs) with an increased photocatalytic effect at longer wavelengths compared to undoped TiNTs were used, and the effect on the early hydration and mechanical properties of the main clinker phase tricalcium silicate (C₃S) was investigated for the first time. Prior to the incorporation of nanotubes into C₃S, it was treated with a supersaturated Ca(OH)₂ solution. The addition of 1 and 2 wt.% of Fe/TiNTs into the C₃S system significantly accelerated the course of hydration. The degree of hydration for the hydration products after 8 h, 1 d and 7 d have improved. The enhancement of compressive strength after 7 d, 14 d and 28 d were observed compared to normal TiO₂ nanotubes (TiNTs). Treating Fe/TiNTs with a supersaturated Ca(OH)₂ solution revealed a stronger interaction between Ca²⁺-ions and nanotubes. Fe/TNTs were synthesized via a modified hydrothermal process. The study shows that Fe/TiNTs can be used as a nanomaterial in cement-based building materials due to their enhanced interaction with the system. Full article

Niobium oxide (Nb₂O₅) is a semiconductor that exhibits photocatalytic properties, making it potentially valuable in addressing air pollution, self-cleaning, and self-disinfection in cement-based materials (CBMs). Therefore, this study aimed to evaluate the impact of different Nb₂O₅ concentrations on various parameters, including rheological characteristics, hydration kinetics (measured using isothermal calorimetry), compressive strength, and photocatalytic activity, specifically in the degradation of Rhodamine B (RhB) in white Portland cement pastes. The incorporation of Nb₂O₅ increased the yield stress and viscosity of the pastes by up to 88.9% and 33.5%, respectively, primarily due to the larger specific surface area (SSA) provided by Nb₂O₅. However, this addition did not significantly affect the hydration kinetics or the compressive strength of the cement pastes after 3 and 28 days. Tests focusing on the degradation of RhB in the cement pastes revealed that the inclusion of 2.0 wt.% of Nb₂O₅ was insufficient to degrade the dye when exposed to 393 nm UV light. However, an interesting observation was made concerning RhB in the presence of CBMs, as it demonstrated a degradation mechanism that was not dependent on light. This phenomenon was attributed to the production of superoxide anion radicals resulting from the interaction between the alkaline medium and hydrogen peroxide. 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

In this study, TiO₂ films were deposited via the doctor blade technique on fiber-cement surfaces. Two types of nanoparticles (TiO₂-P25 from Degussa and TiO₂-PC105 from Tronox) were used to produce films. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) images revealed films with homogeneous and nanoparticulated morphology. The TiO₂ PC105 film presented a lower roughness parameter (RMS) in relation to that of the TiO₂ P25-based film. Both films exhibited high hydrophilicity when exposed to UV-A radiation (contact angle θ < 6°). The photocatalytic activity of the films was evaluated by standardized methylene blue dye degradation assays under UV-A irradiation (1.0 mW/cm²). The TiO₂-PC105 film showed a photonic efficiency of ξ = 0.1%, while for the films obtained with TiO₂-P25, ξ = 0.08%. The cement surface modified with the PC105 film was evaluated for antimicrobial activity through the use of multiple pathogens commonly found in hospitals. A considerably high efficiency was measured with visible light. Growth inhibition rates of 99.0% ± 0.2, 99.1% ± 0.2, 99.1% ± 0.2, 97.5% ± 0.5, 98.0% ± 0.5 and 98.0% ± 0.5 were found for Staphylococcus aureus, Klebsiella sp., Escherichia coli, Rhizobium sp., Fusarium sp. and Penicillium sp., respectively. The results show the self-cleaning ability and their potential use for protection, by preventing contamination of the fiber-cement surface and opening new possibilities for the use of this building material. Full article

The effect of titanium dioxide (TiO₂) on the mechanical properties of cement slurries including their benefits on air purification and abatement of pollutants is not well documented. Cementitious-based slurries are typically applied in thin layers as decorative coatings for existing facades, protection against an ingress of aggressive ions, or rainproof covers to minimize water penetration. Different parameters including the TiO₂ concentration, dispersion time during batching, and applied thickness on top of existing mortar blocks are investigated in this paper. Tested properties included the flow, colorimetry, compressive/flexural strengths, bond to existing substrates, water absorption, and photocatalytic activity evaluated using an ISO 22197-1:2007 reactor. The results showed that the mechanical properties remarkably improved with TiO₂ additions, up to 8% of the cement mass. This was attributed to two concomitant phenomena including a micro-filler effect that enhances the packing density and nucleation sites to promote strength development. The removal of nitrogen oxides from the atmosphere reached 92% when the TiO₂ was added at a rate of 5% of the cement mass. Such data can be of particular interest to consultants and environmental activists searching for innovative materials capable of maintaining better ambient air quality in urban and modern cities. Full article

Porous magnesium oxychloride cement (PMOC) has a high specific surface area formed by interlocking whiskers, which can be used as a promising photocatalyst substrate for the photocatalytic removal of atmospheric pollutants. In this paper, magnesium oxychloride cement (MOC) was used as matrix and TiO₂ as catalyst to prepare MOC blocks. Plant-based protein was used as a foaming agent to form the layered porous structure suitable for supporting TiO₂ particles, which effectively increased the surface area of light radiation and TiO₂ adhesion area in photocatalytic porous magnesium oxychloride cement (PPMOC). It was found that the addition of the foaming agent can increase the adsorption capacity of MOC to TiO₂. The vacuum-immersion loading method can effectively support TiO₂ on the surface of PMOC. The photocatalytic performance of PPMOC can be improved by multiple loading, while higher porosity of PMOC would reduce the loading surface of matrix to TiO₂ particles, which might decrease the photocatalytic efficiency. As can be observed in PPMOC specimens, when the porosity of PPMOC is less than 60%, increasing the porosity can improve the photocatalytic efficiency, while when the porosity is higher than 60%, increasing the porosity decreased the photocatalytic efficiency due to the reduction of the loading surface. The excellent nitrate selectivity of PPMOC also shows good application potential in the field of catalytic degradation of nitrogen oxides. Full article

In this paper, recycled concrete powder (RCP) is used as the carrier of g-C₃N₄-TiO₂ instead of natural minerals. The prepared g-C₃N₄-TiO₂/RCP composites were characterized by X-ray diffractometer, scanning electron microscope, infrared spectrometer, specific surface area analyzer, UV-visible spectrophotometer, and RhB solution degradation experiments. The results show that the rough, porous structure of RCP was beneficial to the stable load of g-C₃N₄-TiO₂. Under the condition that the content of g-C₃N₄-TiO₂ catalyst is constant, the agglomeration of g-C₃N₄-TiO₂ can be reduced by using RCP as a carrier, thus improving its photocatalytic efficiency. Subsequently, g-C₃N₄-TiO₂/RCP was loaded onto the surface of cement-based materials by coating bonding method to study its photocatalytic performance. It is found that the photocatalytic cement-based material has a similar degradation effect on the degradation of surface RhB as g-C₃N₄-TiO₂/RCP in RhB solution. Our work may open up a new field for the recycling of RCP and provide new ideas for the development of photocatalytic cement-based materials. Full article

This work aimed to investigate the influence of selected material variables on the self-cleaning and air purification efficiency in NO_x 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. Full article

In this paper, a novel core@shell nanosphere (TiO₂@CoAl-LDH) based on layered double hydroxide (LDH) combined with a nano-TiO₂ semiconductor was synthesized and introduced to cementitious materials via spraying technology and a smearing method. The compatibility with a cementitious matrix and the effects of TiO₂@CoAl-LDH on cement hydration, surface microstructure, and the microscopic mechanical properties of mortar were investigated by AFM, microhardness testing, FESEM, and BET analysis. Meanwhile, the effects of TiO₂@CoAl-LDH introduction methods on the photocatalytic performance and durability of the photocatalyst were systematically evaluated by methylene blue (MB) removal ratio and wear testing. The results show that TiO₂@CoAl-LDH exhibits enhanced compatibility with cementitious matrices and a higher photocatalytic capacity than individual CoAl-LDH and nano-TiO₂. The photocatalytic mortar prepared via spraying technology (CM-C) displays a higher photocatalytic capacity than that prepared via the smearing method (CM-S). Among them, the mortar with two layers of photocatalytic coatings (CM-C2) has the highest MB removal ratio, which reached 95.1% within 120 min of UV-visible light irradiation. While on the other hand, the wear test revealed that the smeared mortar has a higher photocatalytic capacity and better photocatalyst durability than the sprayed mortar. This work is expected to contribute to the development of multifunctional sustainable building materials. Full article

Building materials are traditionally known for their mechanical and structural properties. As environmental pollution has risen as a huge global issue, functional building materials with environmental remediation capabilities are the demand for the present time. In this context, cement and concrete with photocatalytic and adsorbent additives were explored for air and water remediation. The usage of functional building materials for self-cleaning and air cleaning is well documented and reviewed in earlier reports. This article gives an overview of the functional building material composites used for water remediation. Numerous different approaches, such as photocatalysis, adsorption, and antimicrobial disinfection, are discussed. Among all, photocatalysis for the degradation of organic compounds and antimicrobial effect has been the most studied method, with TiO₂ being the first choice for a photocatalyst. Furthermore, some reports illustrate the impact of photocatalytic filler on hydration and mechanical properties, which is important in case these are used in construction. Adsorption was most preferred for heavy metal removal from the water. This article rationalizes the current status and future scope of cement-based functional composites for water cleaning and discusses their use in water cleaning facilities or regular construction. Full article