Effect of leaching on the hardened, microstructural and self-cleaning characteristics of titanium dioxide containing cement mortars

Abstract

In this study, the effect of leaching attack on titanium dioxide (TiO2) containing photocatalytic cement mortars was investigated. Changes in the mechanical, microstructure, and photocatalytic properties of the mortars were studied with the leaching attack. The photocatalytic mortars were made with ordinary Portland cement as binder. TiO2 was added at 0%, 1.5%, 3%, 4.5%, and 6% of the binder weight. After curing for 90 days in saturated limewater, the mortars were immersed in 6 M ammonium nitrate (NH4NO3) solution for 140 days. The leaching depth, loss of compressive and flexural strengths, changes in porosity, and ultrasonic pulse velocity (UPV) were measured. Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetry analysis (TGA), and differential scanning calorimetry (DSC) tests were conducted to investigate the microstructural damages. The effects of leaching on the photocatalytic performance were evaluated by observing rhodamine B discoloration on the controlled and leached mortars. Experimental results showed that the addition of TiO2 increased the resistance of the mortars to the leaching attack. The loss of hardened properties and microstructural changes were reduced with the addition of TiO2. The leached mortars showed photocatalytic activity after exposure to ultraviolet light, however, self-cleaning was slightly reduced after the leaching attack. (C) 2019 Elsevier Ltd. All rights reserved.