Anibal Maury Ramirez

Evaluation of the Algaecide Activity of Titanium Dioxide on Autoclaved Aerated Concrete

Abstract Under certain environmental conditions, autoclaved aerated concrete has evidenced serious problems due to the easy growth of micro-organisms such as algae. In order to prevent this situation, traditional preventive practices such as water repellents and biocide agents have been studied. Nevertheless, these efforts have not led to a complete elimination of the problem. Based on the evidence that TiO2 decomposes organic compounds belonging to the cell wall of living micro-organisms such as algae and the promising results obtained with porous lavas as supports for TiO2 in water treatments, experiments to evaluate the algicidal activity of titanium dioxide on autoclaved aerated concrete samples have been executed using a recently developed equipment for extra-accelerated algae growth on cementitious materials. After five weeks, by means of visual inspection, colorimetric and image analyses, it was estimated that in relation to some reference samples (without TiO2), TiO2 coated samples evidenced partial photodegradation of algae species (Chlorella vulgaris).

Application of TiO2 Photocatalysis to Cementitious Materials for Self-Cleaning Purposes

Cementitious materials, especially those exposed to outdoor conditions, are directly and continuously exposed to many atmospheric pollutants, (organic, inorganic and particulate matter), microorganisms (e.g., algae, fungi, cyanobacteria) and different weather conditions. As a result, they have an accelerated deterioration process which can produce in many cases important changes in the materials properties, among them aesthetic properties. Colour, for example, has to give a pleasant appearance that should give to the public an adequate perception of the quality and maintenance of buildings or structures. However, serious colour changes are produced on the buildings and structures due to the mineral composite nature of cementitious materials. The nature causes relatively high porosity and roughness, which enable the deposition of coloured organic pollutants or particulate matter and partially facilitate biological growth.