The Influence of TiO2 Nanoparticles on the Smart Properties of Alkali-Activated Materials

The purpose of this work is to investigate the influence of the addition of TiO2 nanoparticles on the rheological, physico-mechanical and photocatalytic properties of alkali-activated slag-based mortars. The self-cleaning capability of TiO2-containing composites were evaluated by means of accelerated dye degradation tests and 24-months outdoor exposure tests in comparison with Portland-based mortars. Experimental results show that the variation of the rheological properties of mixtures due to the addition of TiO2 is negligible while it can be noted a general reduction on the setting times by increasing the amount of the TiO2 content. The use of TiO2 seems to have a minor effect on the elasto-mechanical properties of slag-based mortars at early and long ages. Only alkali-activated materials with low alkali content evidence an increase in compressive strength from 9 to 14% with respect to the same mortars manufactured without nanoparticles. The beneficial effect of TiO2 addition in self-cleaning capability is evident both in cementitious and alkali-activated mortars under accelerated tests. In particular, regardless of UV light exposure time and dye nature, the color variation increases almost linearly by increasing the nanoparticles content. Finally, the self-cleaning ability has been evaluated by measuring the color variation during the exposure of mortar samples to the industrial environment for 2 years. Results evidenced the efficiency of the titanium dioxide on the reduction of the color variation promoted by the polluted environment.