Estudo de viabilidade do uso de grafeno como aditivo para melhora de propriedades mecânicas do gesso

Abstract

Gypsum powder (or “plaster of Paris”), when mixed with water, turns to a moldable paste that hardens quickly and can be used for various purposes, being widely used in construction in plastering and drywalls. A proper hydration of the gypsum powder ensures greater effectiveness in the formation, density and interlacing of crystals that will define its mechanical performance. Considering that the hydration reaction of gypsum is exothermic and depends on the thermal properties of the paste, its mechanical properties are affected by the internal temperature, since this affects the gypsum solubility and consequently its crystallization rate. This dissertation means to analyze the mechanical properties such as tensile strength, compression and hardness of the gypsum powder mixed with water and multilayers of graphene (MLG) as an additive, considering its excellent thermal conductivity, mechanical performance and hydrophobicity. For the purpose of this study, 5 experimental batches were made using MLG mixed with water in gypsum production, in addition to the control batch (pure plaster). The adopted MLG dosages were 0.0150%, 0.0175%, 0.0200%, 0.0225% and 0.0250% in relation to the gypsum powder mass. The ratio water/plaster of 0.5 was used. Axial compression test, diametral compression test and surface hardness tests were carried out to analyze the influence of the additive on the mechanical properties of the gypsum. As for its properties as a fluid, consistency, setting times and hydration curves were verified. The influence of MLG on the water tolerance of the hardened material was also analyzed. The results showed 120% increase in mechanical strength for compression and tensile at a dosage of 0.020% at the age of 7 days. Such increase can be the result of an internal heat dissipation which enabled greater production of better distributed crystallization cores. The results related to tolerance to the presence of water indicated that the higher the dosage of graphene, the more water resistant the material became, probably due to the hydrophobic properties of graphene.