ResumoOs processos fotocatalíticos estão sendo estudados e incorporados a sistemas construtivos objetivando melhoria da qualidade da água e do ar. No entanto pairam dúvidas sobre qual o grau de atuação da fotocatálise nos substratos e sobretudo por quanto tempo continua ocorrendo e qual sua intensidade. O método proposto consiste em, através de um pós-tratamento superficial associado a um processo fotocatalítico, obter a simultaneidade das ações dos efeitos hidrofóbicos e hidrofílicos. O presente artigo propõe avaliar a durabilidade de processos fotocatalíticos por meio de um programa experimental, em que corpos de provas de argamassa para revestimento externo após serem pós-tratados e manchados com soluções de azul de metileno (C16H18N3SCl) na concentração de 1% em água deionizada e em álcool etílico 92,8°(C2H6O), foram submetidos a 200 ciclos de envelhecimento artificial (molhagem, exposição à radiações infravermelho e ultravioleta). Os resultados apontam: 1) o aumento da concentração de dióxido de titânio acelera os processos de degradação do azul de metileno; 2) os tratamentos superficiais com dispersões aquosas de TiO2 apresentaram queda de desempenho ao longo dos ensaios; 3) o hidrofugante à base de silicone mostrou um bom potencial como agente de fixação do semicondutor.

AbstractThe photocatalytic processes are being studied and incorporated into building systems aiming at the improvement of the quality of water and air. However, there are doubts about the impact of the action of photocatalysis on substrates and especially about how long it continues occurring and about their intensity. The proposed method consists in using a surface post treatment associated with a photocatalytic process, in order to obtain the simultaneous actions of the hydrophilic and hydrophobic effect. This paper proposes to assess the durability of photocatalytic processes by means of an experimental program, where the bodies of the mortar tests for external coating after being post-processed and stained with methylene blue solution (C16H18N3SCl) at a concentration of 1% in deionized water, and 92.8 ° in ethyl alcohol (C2H6O) were subjected to 200 cycles of artificial aging (wetting, exposure to ultraviolet and infrared radiation). The results lead to: 1) increasing the titanium dioxide concentration of methylene blue accelerates the degradation process; 2) surface treatment with aqueous dispersions of TiO2 showed a decline in performance over the tests; 3) the hydrophobic silicone-based showed a good potential as semiconductor fixing agent.

Polymer-modified mortars are highly popular for setting exterior tile systems and low-porosity ceramic tiles because they possess greater flexibility and higher bond strengths than conventional mortars which increases cladding serviceability. However, the long-term performance of this application is not completely understood and many pathologies has been reported. The negative influence of water saturation on polymer modified mortar is well documented and this paper investigates the influence that progressive water intake on bond strength by applying pull out tests on several different mortars. Four of those mortars were especially prepared with well known raw materials and concentrations, and three others were ready-made commercial products designed for setting ceramic tile on building façades. The tests were performed during twenty-five day drying period in laboratory conditions after specimens saturation for ten days of immersion in water. The results revealed that: (i) the ready-made commercial and the prepared mortars have similar behavior; (ii) their bond strengths are highly influenced by small increases in moisture content; (iii) moisture content higher than 10% is enough to reduce mortar bond strength by one-half; (iv)during the drying process bond strength increases continuously until reaching values similar to the initial ones.