Preliminary experimental study on the effects of surface-applied photocatalytic products on the durability of reinforced concrete

The aim of this paper is to assess, by the results of suitable experimental tests, the durability performances of surface-applied concrete layers that incorporate a photocatalytic material such as titanium dioxide. The use of photocatalytic materials for air purification has been developing rapidly in the last decades. Within this framework, the proposed experimental study is particularly significant considering that, although there are many advantages in applying photocatalytic construction materials, during the TiO 2-photocatalysis a large variety of organics, viruses, bacteria, fungi, algae can be totally degraded and mineralized to CO2, H 2O and harmless inorganic anions. The mineralized amounts of CO 2, deriving from both the photocatalytic oxidation itself and the external ambient, can progressively activate a chemical deterioration due to carbonation. It is then important to investigate the resistance properties of photocatalytic concrete products against carbonation. The effects of the photocatalytic activity on the durability of concrete have been assessed by using accelerated carbonation and corrosion of reinforcing steel tests. In order to keep the photocatalytic process ongoing, specimens with finish coatings containing TiO2 were put in direct contact with air (water in the form of humidity) and were subjected to light radiation. Results show that photocatalytic concrete products applied on the surface of concrete improve the property of carbonation resistance and reduce the corrosion propagation rate of reinforcing bars with respect to the case of cement coatings without any photocatalysts. The adopted experimental procedure can give a first contribution in order to understand if the photocatalytic activity of titanium dioxide creates a photocatalysed system acting as a protective barrier against the deterioration processes.