New Generation Multi-Functional Cementitious Composites with Photocatalytic Degradation Capability

Abstract

Today, air quality continues to be an important issue affecting public health, environment, and economy around the world. One of the most fundamental problems faced by industrialized societies is air pollution caused by high amounts of nitrogen oxides (NOₓ) released from crowded cities and industrial areas to the atmosphere. Thanks to remarkable technological developments, such problems are reduced using ultraviolet (UV) rays from solar energy, and new solutions are tried to be produced for large surface areas of building materials. Considering that concrete is the most widely used material after water, it can be said that one of the main ways to overcome the air pollution faced by modern societies is to develop innovative, functional, and economical building materials reducing air pollutants by chemically binding them. In this context, titanium dioxide (TiO₂), a type of photocatalytic material and also a semiconductor, comes to the fore with some of its properties such as its strong oxidation capacity under UV light irradiatons, its chemical stability when exposed to acidic and basic compounds, its chemical inertness in the absence of UV lights, and its non-toxicity. Due to these properties, it is an important photocatalyst material that can be used in construction applications. Within the scope of this thesis study, TiO2-added photocatalytic cementitious composites were developed by considering many parameters at different scales (nano and micro scales) at the same time, which can offer applicable solutions to the abovementioned environmental problems. In this context, first of all, an efficient mixing method to be used in experimental studies of this thesis was developed in order to homogeneously disperse TiO₂ particles of different sizes (especially nanoscale) throughout cement-based materials. After that, TiO2 particles under different crystal phases (anatase and rutile) were substituted into the cement-based systems at the rates of 2.5%, 5%, 7.5%, and 10% of the total weight of binder to investigate their effects on composite materials’ properties and the most appropriate usage rate of TiO2 was determined. Then, the optimum particle size distribution (PSD) of TiO₂ particles was determined by using TiO2 particles with three different size ranges (nano, submicron and micron) in combination at the optimum substitution rate by adjusting their PSDs with three different PSD moduli (q): 0.1, 0.5, and 0.9. Finally, the photocatalytic degradation capability of TiO₂ particles under different crystal phases (anatase and rutile) were investigated by incorporating them into the cementitious systems and the most suitable combination of anatase and rutile TiO2 particles was determined.