Abstract
This study aims to examine the mechanical, shrinkage and chemical properties of photocatalytic cementitious materials containing synthetic fibers and a shrinkage-reducing admixture (SRA). Two types of titanium dioxide (TiO2) powders and white Portland cement were considered along with ordinary Portland cement (OPC) as a control. Two types of synthetic fibers, i.e., glass and polyethylene (PE), and an SRA with contents varying from 0% to 3% were also considered. Using the TiO2 powders and the white Portland cement was effective in reducing the nitrogen oxides (NOx) concentration in cement composites. The use of PE fibers was more effective than glass fibers in terms of the mechanical properties, i.e., the compressive strength and tensile performance. With the addition of TiO2 powders and SRA or the replacement of OPC with white cement, the mechanical properties of the cement mortar generally deteriorated. The total shrinkage of the mortar could be reduced by incorporating the fibers at volume fractions greater than 1%, and the glass fiber was more effective than the PE fiber in this regard. The TiO2 powders had no significant impact on the shrinkage reduction of the cement mortar, whereas the SRA and the white Portland cement effectively reduced shrinkage. The addition of 3% SRA decreased the total shrinkage by 43%, while the replacement of the OPC with white cement resulted in a 20% reduction in the shrinkage.
Highlights
Various harmful gas emissions, which are increasing in large cities around the world, pose a high risk to human health
The nitric oxide (NO) was transformed to a nitrate ion as a result of the existence of water and oxygen in the air, leading to a decrease in the NO concentration
The NO removal capability was measured at the bottom surface of the test panels, and the use of the NP400 led to a better nitrogen oxides (NOx) removal capability than that of the P-25 owing to its higher density of 3.70 g/mL
Summary
Various harmful gas emissions, which are increasing in large cities around the world, pose a high risk to human health. It is necessary to remove or decrease the emissions of substances such as nitrogen oxides (NOx ), sulfur oxides (SOx ) and volatile organic compounds (VOCs). The mechanism of NOx removal by photocatalytic cementitious material has been established: titanium dioxide (TiO2 ) absorbs photons +. Based on an experimental study of the self-cleaning of organic dyes and NOx degradation, Jimenez-Relinque et al [5] found that (1) an addition of 2% TiO2 by weight of cement decreases the workability and compressive strength of the mortar; (2) the photocatalytic efficiency for both NOx and self-cleaning occurs in descending order of ordinary Portland cement, fly ash and blast furnace slag mortars; and (3) the efficiency of the degradation of NOx increases with the surface roughness of tested samples. Seo and Yun [1] investigated the NOx removal rate of cement mortars containing
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