Photo-induced carbonation of lime-TiO2 mortars

In this work, titanium dioxide (TiO2) has been used as an additive in lime binder (Ca(OH)2), in order to benefit from its photocatalytic properties and study both the photocatalytic properties of the produced mixtures and the effect of photocatalytically produced carbon dioxide on the carbonation process of lime. TiO2 was added in three different portions (3, 6 and 10% w/w) in lime mixtures and their physicochemical and photocatalytic properties were studied and compared to those of a reference, made exclusively of lime. The photocatalytic properties of the mixtures were studied through the photo-oxidation of an organic model pollutant solution (methyl orange) to a colorless form, as well as by studying the microstructure and carbonation depth in different groups of mixtures subjected to photocatalysis cycles in the laboratory and exposed for a 2 month period in the open air (urban environment).Laboratory results confirmed that lime-TiO2 composite mixtures exhibit photocatalytic properties in both UV radiation conditions and direct exposure to sunlight. Moreover, analytical results indicated an enhanced carbonation of lime-TiO2 composites. TiO2 can be added to lime successfully and can have applications in lime-based mortars used in the conservation of architectural heritage, enhancing their performance against soiling and amenity loss.