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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 NOx 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 NOx 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. [ABSTRACT FROM AUTHOR]

This study explores the development and performance of photocatalytic cementitious composites modified with nano-TiO2 to address urban air quality and sustainability challenges. Nine mortar series were prepared, incorporating binders with varying carbon footprints and mass contents across different series. The interplay between the fundamental (abrasion resistance) and functional (air purification efficiency) properties of the composites' surfaces and interfaces was investigated. The photocatalytic removal of airborne pollutants, specifically nitrogen oxides (NOx) and ozone (O3), was evaluated under simulated environmental conditions. The variations in binder composition influenced the composites' overall initial carbon footprint and air purification efficiency. The assessment revealed a possible net decrease in carbon emissions over the life cycle of the composite due to the removal of ozone (greenhouse gas) and its precursor—NOx, highlighting the potential of photocatalytic cementitious composites for dual environmental benefits in an urban environment, emphasizing the critical role of surface and interface engineering in achieving carbon-negative composites. [ABSTRACT FROM AUTHOR]

This research investigated the properties of modified cementitious composites including water purification from heavy metal—zinc. A new method for characterizing the immobilization properties of tested modifiers was established. Several additions had their properties investigated: biochar (BC), active carbon (AC), nanoparticulate silica (NS), copper slag (CS), iron slag (EAFIS), crushed hazelnut shells (CHS), and lightweight sintered fly ash aggregate (LSFAA). The impact of modifiers on the mechanical and rheological properties of cementitious composites was also studied. It was found that considered additions had a significantly different influence over the investigated properties. The addition of crushed hazelnut shells, although determined as an effective immobilization modifier, significantly deteriorated the mechanical performance of the composite as well as its rheological properties. Modification by iron slag allowed for a significant increase in immobilization properties (five-fold compared to the reference series) without a substantial impact on other properties. The negative effect on immobilization efficiency was observed for nanoparticulate silica modification due to its sealing effect on the pore network of the cement matrix. The capillary pore content in the cement matrix was identified as a parameter significantly influencing the immobilization potential of most considered modifications, except biochar and active carbon. [ABSTRACT FROM AUTHOR]

This study investigated how the surface characteristics of photocatalytic cementitious composites influenced the effectiveness of air purification from nitrogen oxides (NOx), 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 NOx 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. [ABSTRACT FROM AUTHOR]

The risk of the releasing of nanometric particles from construction materials with nanometric components might be one of the biggest threats to further development of them. One of the possible ingress routes to human organisms is the respiratory system. Therefore, it is crucial to determine the risk of emission of nanometric particles during material usage. In the presented paper, abrasion of mortar samples with nanometric TiO2 was investigated. A special abrasion test setup was developed to reflect everyday abrasion of the concrete surface of pavements. In the study, three TiO2-modifed mortar series (and respective reference series) underwent the developed test protocol and the grains were mobilized from their surface due to the applied load analyzed (granulation, morphology, and chemical composition). For a comparative analysis, an abrasion parameter was developed. Based on the obtained results, the modification of cementitious composites with nanometric TiO2 contributed to a reduction in the emission of aerosols and, therefore, confirmed the compatibility between TiO2 and cement matrix. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The application of photocatalytic materials has been intensively researched in recent decades. The process of nitric oxide (NO) oxidation during photocatalysis has been observed to result in the formation of nitric dioxide (NO2). This is a significant factor of the photocatalysis process, as NO2 is more toxic than NO. However, it has been reported that ozone (O3) is also formed during the photocatalytic reaction. This study analyzed the formation and oxidationof O3 during the photocatalytic oxidation of NO under ultraviolet irradiation using commercial photocatalytic powders: AEROXIDE® TiO2 P25 by Evonik, KRONOClean® 7050 by KRONOS®, and KRONOClean® 7000 by KRONOS®. An NO concentration of 100 ppb was assumed in laboratory tests based on the average nitric oxide concentrations recorded by the monitoring station in Warsaw. A mix flow-type reactor was applied in the study, and the appropriateness of its application was verified using a numerical model. The developed model assumed an empty reactor without a photocatalytic material, as well as a reactor with a photocatalytic material at its bottom to verify the gas flow in the chamber. The analysis of the air purification performance of photocatalytic powders indicated a significant reduction of NO and NOx and typical NO2 formation. However, no significant formation of O3 was observed. This observation was verified by the oxidation of pure ozone in the process of photocatalysis. The results indicated the oxidation of ozone concentration during the photocatalytic reaction, but self-decomposition of a significant amount of the gas. [ABSTRACT FROM AUTHOR]

In this paper the effect of limestone and granite aggregate on drying shrinkage of a concrete is investigated. Mixes containing limestone and granite with different Dmax and cement paste volume were tested. A two level, full factorial experiment with three independent factors was conducted which allowed not only to determine the influence of every single factor itself but also potential interactions between them. Measurements of shrinkage were performed up to 98 days after demolding on the beams (10×10×50 cm), in accordance with the procedure from polish standard PN-84/B-06714/23 (Amsler’s method). The multivariate analysis of variances (MANOVA) was used for the statistical analysis of the results. The obtained results confirm that the cement paste volume has a decisive influence on a drying shrinkage of a concrete. However statistical analysis showed that with the assumed variability, either the Dmax or type of coarse aggregate has no significant influence on drying shrinkage, still those parameters may potentially be crucial in some cases. A statistically significant interaction between Dmax and type of aggregate has been found. Furthermore the results of drying shrinkage measurements were compared with estimation results from Bażant-Baweja B3 Model and Eurocode 2. The comparison shows that B3 Model provided more accurate results than Eurocode 2.