Navegando Escola de Engenharia Mackenzie (EE) por Autor "Acosta, Yonaikel Josuhe Contreras"
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- DissertaçãoArgamassa de cimento Portland com adição de Barita (BASO4)Acosta, Yonaikel Josuhe Contreras (2020-01-21)
Escola de Engenharia Mackenzie (EE)In the construction industry, Portland cement (CP) is the fundamental component in the preparation of mortars and concretes, also to being mixed with additives can improve its performance in different structural applications. This work aims to evaluate the properties in the fresh and solid state of CP mortar with addition of barite (BaSO4) in different dosages between 15 and 25% by weight and with a water/cement ratio of 0.7. The barite was characterized by water pycnometer, thermal analysis and X-ray dispersive energy spectroscopy (EDS). The consistency index (CI) or workability of the mortar was determined with the slump test on flow table. The specific gravity calculated in the pycnometer test was 4.2. The thermal analysis of the barite showed a total mass loss of 1.47% and presented an endothermic transition at 1188ºC. The thermal analysis of the commercial sand-barite mixture showed a mass loss of 0.49% and presented an endothermic peak at 265.2°C and another at 1183.4°C corresponding to the polymorphic transformation of barite. The mortar slump test showed an approximate 10% decrease in the formulation with the addition of 20% by weight baryte. The mass percentage of barium was 38.30% recorded in the EDS analysis. The experimental density of standard, with barite and commercial mortars showed values between 1.89 and 2.06 g/cm3. The micrographs obtained by scanning electron microscopy (SEM) showed the morphology of the hydrated calcium silicate (C-S-H) and BaSO4 compounds present in the composite material. In the compression tests, the strength of the mortar increased proportionally with the addition of barite. The mortar with 25% by weight of barite registered the highest values of mechanical strength and speed of wave propagation with 28 days of curing. The X-ray diffraction spectra of barite, standard mortar and mortars with additives showed the typical crystalline phases of Portland cement and the characteristic peaks of barite are in agreement with those reported in the literature. In tests with gamma ionizing radiation, the linear attenuation coefficient decreased with the addition of barite and presented the lowest value for the mortar prepared with the commercial mixture. The results of the research showed that the addition of barite improved the strength of the mortar in the hardened state and did not positively modify the properties of attenuation to gamma radiation.