Avaliação da influência do uso de agregados com diferentes coeficientes de dilatação térmica no comportamento de argamassas de revestimento submetidas a envelhecimento acelerado

Abstract

The present work aims to evaluate the behavior of rendering mortars with aggregates with different thermal expansion coefficients when subjected to thermal stresses generated by accelerated aging. Four cementitious rendering mortars have been developed, using natural fine aggregates (AN) and fine aggregates from crushed basaltic rock (ABB), crushed granitic rock (ABG) or crushed quartzite rock (ABQ). The thermal expansion coefficients of the aggregates and the characterization of mortars in the fresh state were determined. In the hardened state, the rendering mortars were subjected to accelerated aging and analyzed before and after the thermal stress. The evolution of the cracking in the microstructure of the rendering mortars was analyzed by scanning electron microscopy. The results have demonstrated that mortars composed by natural fine aggregate (AAN) have shown a significant degradation when compared to the rendering mortars composed by crushed basaltic rock (AABB), crushed granitic rock (AABG), and quartzite crushed rock (AABQ). The importance of textural parameters and of the thermal properties of the aggregates in the mortar composition has been proven in all rendering mortars made out from crushed rock aggregates, as well as the influence of the superplasticizer used in the increase of the mechanical strength during the accelerated aging.