The effect of the use of TiO2 nanoparticles in the production of cementitious composites, worldwide already known, represents an area of interest for the development of materials with self-cleaning capacity; antimicrobial, antibacterial, antifungal properties; and to contribute to the reduction of environmental pollution. This paper aims to analyze the influence that TiO2 nanoparticles have on the cementitious matrix regarding hydrophilicity, this being one of the two main parameters of the self-cleaning mechanism. Experimental tests, conducted by using the indirect method of measuring the surface water absorption, indicated that an addition of 3%-6% (relative to the amount of cement) of TiO2 nanoparticles is effective in terms of increasing the surface hydrophilicity of the cementitious composites. An excess of TiO2 nanoparticles in the composite matrix (10% TiO2 nanoparticles relative to the amount of cement) not only does not improve surface performance in terms of hydrophilicity, but also reduces them. However, in practice on a case-by-case basis, an analysis is required regarding the optimal amount of nanoparticles used as an addition in the mix-design of the cementitious materials that are intended to induce the quality of self-cleaning process, depending on the intended use, climate, degree and duration of sunlight, and so on.
The formation of biofilms on cementitious building surfaces can cause visible discoloration and premature deterioration, and it can also represent a potential health threat to building occupants. The use of embedded biofilm-resistant photoactivated TiO2 nanoparticles at low concentrations in the cementitious composite matrix is an effective method to increase material durability and reduce maintenance costs. Zone of inhibition studies of TiO2-infused cementitious samples showed efficacy toward both Gram-negative and Gram-positive bacteria.
Contemporary urban architecture faces two important issues: degradation of buildings, caused by exposure to various environmental factors (air and water pollution, mainly generated by the fuels combustion used for transport and heating) and also the costs for repair, cleaning and maintenance of the buildings facades. Regarding the last mentioned aspects, recent research led to development of materials with self-cleaning potential and consequently pollution reduction. Self-cleaning concrete represents a state-of-the-art material with photocatalytic properties generated by the addition in its composition of nanomaterials like TiO2. Already known for its intrinsic photocatalytic character, TiO2 has the ability to catalyse the decomposition of organic substances like grease and dirt, facilitating their quick removal only by rainwater action. Therefore, a building façade made of TiO2-SiO2-containing material develops substantial savings regarding maintenance costs, water consumption and less detergents contamination due to its intrinsic super hydrophilic effect of the surface in the presence of UV radiation, leading to easy dirt removal when water reaches it. The aim of present paper is presenting the latest stage of worldwide research regarding the obtaining of self-cleaning concrete and also the possibility of adapting the concept to the actual Romanian architecture needs, as a sustainable solution for urban pollution reduction.
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