Abstract
In this study, the effects of titanium dioxide (TiO2) nanoparticles on the sulfate attack resistance of ordinary Portland cement (OPC) and slag-blended mortars were investigated. OPC and slag-blended mortars (OPC:Slag = 50:50) were made with water to binder ratio of 0.4 and a binder to sand ratio of 1:3. TiO2 was added as an admixture as 0%, 3%, 6%, 9% and 12% of the binder weight. Mortar specimens were exposed to an accelerated sulfate attack environment. Expansion, changes in mass and surface microhardness were measured. Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), X-ray Diffraction (XRD), Thermogravimetry Analysis (TGA) and Differential Scanning Calorimetry (DSC) tests were conducted. The formation of ettringite and gypsum crystals after the sulfate attack were detected. Both these products had caused crystallization pressure in the microstructure of mortars and deteriorated the mortars. Our results show that the addition of nano-TiO2 accelerated expansion, variation in mass, loss of surface microhardness and widened cracks in OPC and slag-blended mortars. Nano-TiO2 containing slag-blended mortars were more resistant to sulfate attack than nano-TiO2 containing OPC mortars. Because nano-TiO2 reduced the size of coarse pores, so it increased crystallization pressure due to the formation of ettringite and gypsum thus led to more damage under sulfate attack.
Highlights
IntroductionTitanium dioxide (TiO2 ) is a white and inorganic material
We investigate the effects of nano-TiO2 on the sulfate attack resistance of pure Portland cement mortars and slag-blended mortars at two exposure temperatures
We investigated the influence of titanium dioxide (TiO2 ) nanoparticles on the sulfate attack upon ordinary Portland cement and slag-blended mortars
Summary
Titanium dioxide (TiO2 ) is a white and inorganic material. It is used as an effective photocatalyst and can be activated by light radiation to degrade organic and inorganic pollutants present in the water and air through oxidation-reduction process. TiO2 has been added to concrete during mixing to yield a product with self-cleaning and air purifying properties [1]. TiO2 can clean the surface of concrete by degrading certain pollutants deposited on its surface in the presence of sunlight and can convert harmful gases like nitrous oxides and volatile organic compounds (VOCs) to less harmful products [2,3]. Concrete with the addition of TiO2 has been referred to in the literature as self-cleaning, air purifying, or photocatalytic concrete. Use of slag in cementitious materials is environmentally beneficial as it helps in reducing carbon dioxide emissions
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