Avaliação da influência da britagem nas propriedades de forma de agregados por meio do processamento digital de imagens

Abstract

Aggregate shape properties, which include form, angularity and superficial texture, affect directly asphalt mixtures’ behavior, as they influence the interactions between the particles themselves and between the particles and the asphalt. Among several factors that may impact on the aggregate shape properties, the crushing process is the one with the greatest possibility to be controlled, by choosing the types of crushers used and by changing the process parameters. The traditional methods of characterizing aggregate shape are often criticized for adopting some indirect, qualitative, time-consuming and laborious materials testing, that provide average values, which do not always represent well the material. Due to these traditional methods’ limitations, various researchers have been working with the goal of developing alternatives techniques to provide more effective characterization of these properties, as the use of the equipment Aggregate Image Measurement System (AIMS), which analyzes shape, angularity and texture, by the Digital Image Processing (DIP) technique. In this way, this research aims to analyze, by using the DIP, how the crushing process influences the aggregates shape properties, based on a case study performed in Fortaleza metropolitan region. Three stone quarries were visited and, in each one, information about the crushing process were registered, and material samples were collected, which were characterized, subsequently, by the Brazilian traditional shape index test and by the DIP, using AIMS. Based on the results, comparisons were made between aggregates produced by different processes, between particles with different sizes, and between the two shape methods used. The analyses made by the DIP showed, more accurately than the traditional test, that the processes divided in larger number of stages tend to produce more cubic coarse aggregate particles. For fine aggregate, however, this trend was not observed. It was perceived that flatness and elongation increases as the size of the particles decreases. Particles angularity suggested a small influence of the different crushing processes, being reduced as the number of crushing stages increased. The texture showed to be related to the material mineralogy and not rushing process