Synthesis and characterization of titania-silica fume composites and their influence on the strength of self-cleaning mortar

This paper describes the sol-gel synthesis and characterization of a titania-silica fume composite obtained by the coating of silica fume (SF) particles with TiO2 photocatalyst nanoparticles. SEM and TEM images revealed the presence of TiO2 nano-spheres at the surface of bigger SF spherical particles and HRTM confirmed the presence of anatase form. The methylene blue photodegradation tests have shown that photocatalytic activity of TiO2-SF composites is improved in the first hours, due to an efficient dispersion of the TiO2 nanoparticles at the surface of SF particles. The TiO2-SF composite powders have a good pozzolanic activity and can be used for the partial substitution of Portland cement in the preparation of self-cleaning mortar. The values of compressive strength of mortars with 3 wt%. TiO2-SF powders are higher as compared with those assessed for reference (Portland cement mortar), especially for longer hardening times (28, 90 days).