Proposição de um método de dosagem para concretos de ultra alto desempenho (UHPC)

Abstract

Ultra High Performance Concrete (UHPC) is a promising material and, due to its excellent mechanical properties and durability, it becomes an attractive solution. Several studies showing the mechanical potential, durability and various applications in different structures vouch the use of UHPC. However, there is a gap in trace determination using a simple, easily accessible dosing method that enables the determination of an optimal ratio of all constituents of the mixture. The work developed with respect to UHPC mixtures, does not present a way to draw a trace with different materials with the ideal amount of fibers to be used, without losing the workability with high mechanical strengths. The objective of the research was to develop a dosing method that can, through informative parameters of the materials, obtain the best compressive and tensile strength of the compound, aiming to find the proportions of the materials in the mixture, as well as the amount of fibers to be inserted without losing workability. For such, it was worked with materials of different particle size distributions, evaluating the largest packing of the particles. Four compositions with different materials were evaluated: cement, active silica, fly ash, two types of fine aggregate, quartz powder and calcium carbonate. The proposed method for matrix compactness verification was based on the Andreasen and Andersen packing method. The results found in this research showed that the proposed dosing method provided greater potential for the mechanical strength of the mixture. A linear relationship between a higher matrix compactness and the compressive strength obtained in the mixture was noticed. In the composition with higher compactness, the compressive strength increased by 20% when compared to the mixture with lower compactness.