Avaliação de concretos com incorporação do óxido de grafeno rico em carbonila submetidos a altas temperaturas

Abstract

Concrete is one of the most widely used materials globally, second only to water in this regard. Its popularity stems from its properties when hardened, such as high mechanical strength, ease of application, and low cost. Since ancient Egyptian times, concrete has evolved continuously, with significant developments including the introduction of additives that alter its physical and mechanical properties. These advancements have driven civil construction, enabling the creation of increasingly tall, complex, and architecturally innovative structures. In the context of concrete durability and structural safety, fire resistance is crucial. There has been a notable increase in fires in civil structures, as seen in recent cases in Brazil, highlighting the need for materials that can withstand fire. This study aims to advance the novel use of a nanomaterial, graphene oxide rich in carbonyl groups (CGO), as an additive in concrete for evaluation at high temperatures. The optimal concentration used is 0.02% relative to the weight of cement. The thermal conductivity of concrete with 0.02% CGO was evaluated in comparison to reference concrete (REF). Subsequently, REF and 0.02% CGO concretes were analyzed at room temperature and subjected to temperatures of 300°C, 600°C, and 900°C. Tests included water absorption by immersion, void index, real density, ultrasonic pulse velocity, compressive and tensile strength, modulus of elasticity, SEM, and XRD. The study revealed that at high temperatures, both REF and 0.02% CGO concrete showed a progressive increase in voids and absorption indices due to pore formation, voids, and chemical transformations. However, 0.02% CGO concrete demonstrated optimization in the matrix at high temperatures, with a reduction in pores and voids compared to REF concrete. The addition of CGO positively influenced water retention and resistance by preventing crack propagation, acting as reinforcement in the structure. Compressive and tensile strength at 300°C in REF and 0.02% CGO concrete showed similar results, attributed to the similarity in the concrete matrix. These findings suggest that CGO can enhance concrete, acting as reinforcement in the structure to improve strength and optimize matrix disposition, especially in concretes exposed to high temperatures.