Avaliação no estado fresco da influência da adição de fibras de polipropileno em argamassas com substituição de cimento Portland por sílica da casca do arroz

Abstract

In this study, the properties and characteristics of mortars in the fresh state were evaluated at different time intervals with the addition of polypropylene fibers in mortars already studied with substitutions of Portland cement for Rice Husk Silica. The incorporations of polypropylene fiber were 0.3% and 0.5% in relation to the volume of the mortar. For this work, a mortar mix of 8MPa of axial compressive strength was used as a reference and the water/cement materials ratio was set at 0.71. The behavior of the mortars in the fresh state was evaluated through the Flow Table, Modified Vicat and Modified Squeeze Flow test. The behavior of the mortars in the fresh state was evaluated through the Flow Table, Modified Vicat and Modified Squeeze Flow tests. Modified Vicat and Squeeze Flow assays were performed at ages 15, 60 and 180 minutes. The results show that for the Flow Table test the consistency values decreased as the polypropylene fiber content was increased. In the Modified Vicat test, the penetrations of the cone decreased with the increase of the polypropylene fiberand with the advancement of the ages studied. In the Modified Squeeze Flow test, the results show that the polypropylene fiber was decisive in the displacements found, making it difficult to compress the samples and reducing the displacements with the incorporation of 0.5% of fiber in relation to the volume of the mortar. With 0.3% fiber, displacements were satisfactory for all trait analyzed at 15 and 60 minutes, including the addition of 30% Rice Husk Silica, which did not affect displacements. At 15 and 60 minutes the mortars showed good workability and at 180 minutes greater hardening. aximum tensile values increased for older ages and the polypropylene fiber was not determinant for changes in tensile values at 15 and 60 minutes, the best times defined for the use of mortar in this study.