From cement mixtures to architectural stone surfaces. Titanium dioxide applications between recent history and evolution

On the international scene, the goals of reducing energy consumption and environmental sustainability require innovative strategies, technologies, and materials, capable of reacting to environmental stimuli. This paper traces an evolutionary path of the applications of titanium dioxide on the surfaces of new and existing buildings in order to trace the history of a technology, which follows a 1967 discovery by Professor Akuira Fujishima of the University of Tokyo. Concretes and coatings containing titanium dioxide nanoparticles take on an active behavior, making the material intelligent or capable of reacting to light stimuli, through reactions activated by light that occur on a nanometric scale. The conditions of super-hydrophilicity alternating with those of super-hydrophobicity under solar radiation make the materials self-cleaning and anti-pollution. In 1996, the Dives in Misericordia Church was designed, a work by Meier built in 2003 on the outskirts of Rome, which constitutes an emblematic application of self-cleaning and anti-polluting concrete. A few years later, new research horizons were defined and this nanotechnology gained experimentation and applications in the field of cultural heritage, significantly revising the concept of minimal invasiveness. Starting from natural photochemical reactions, not visible to the naked eye, some applications of titanium dioxide are described through national and international case studies.