Análise das propriedade ligadas à durabilidade dos concretos de ultra alto desempenho confeccionados com microssílica e cinza de casca de arroz

Abstract

Since the beginning of the works involving ultra-high performance concretes, several applications began to emerge due to the mechanical performance characteristic of this product and the ability of easy molding, since they present self-compacting behavior and absence of coarse aggregates. Thus, the feasibility of using it as a repair material became required due to the fact that it presents a dense matrix and less permeability than conventional concrete. Thus, the present work analyzed the behavior of ultra-high performance concrete with two different pozzolans: microsilica and rice husk ash. The compressive strength of both concretes presented results higher than 130 MPa after 28 days, and there was no increase in strength analyzing the results for 90 days. For the performance in relation to porosity and permeability, the concretes composed by microsilica presented a propensity to water absorption about 20% lower than the ones molded with rice husk ash, however, analyzing the behavior against the attack of sulfates, the concrete composed by rice husk ash had the content of penetration of sulfates about 50% lower than the ones composed by microsilica. Furthermore, analyzing the performance of the materials when subjected to different temperatures of 200°C and 300°C both had decreases in mechanical strength of about 26% and 36%, respectively. At the temperature of 400°C, it was possible to identify the phenomenon of spalling, and it is not possible to consider resistance of this type of material to the sharp rise in temperature. With this, there is potential to use such composite thanks to the high mechanical strength when for the good performance in relevant characteristics linked to low permeability and high durability.