Uma aplicação da análise de componentes principais na determinação do tamanho da maior diagonal de cristais de C3s em amostras de clínquer

Abstract

Clinker is an intermediate product of Portland cement, composing about 90% of it. Clinker’s quality affects directly the quality of the final product, and is evaluated using techniques such as microscopy. Microscopy involves the analysis of microscopic images in order to examine the product’s composition, such as crystals (product phases), porosity, free lime, and so on. Among the investigated elements, the C3S crystal, also called alite, is the most important one. Thus, information such as the distribution of shape and length of this element is of interest to the assessment of product quality. In general, this information is extracted manually, with the help of graphic software. Therefore, this process takes a long time and is subject to human error. Given this, the present work proposes a method to automate the extraction of one of those informations, the length of the C3S crystals present in clinker. To determine that measure, the Principal Component Analysis technique is used here to analyze the contour of each crystal, that must be previously segmented by an object detection algorithm. This technique finds a component that preserves the most variance of the data, resulting in a line that approximates the direction of the longest diagonal of the crystal. After, the two points closest to the extremes of the line are chosen, and the Euclidean distance between them is calculated in pixels. Following that, the calculated distance is converted to a scale built for better interpretation by the analyst. The method is compared with two other algorithms: Simple Linear Regression and an algorithm based on local maxima of distances to the centroid. The proposed method showed to be quite fast and more precise than the other two approximation algorithms. As a result, it is expected that this process will provide a good estimate of the crystal’s length in a scale that is usual to the cement quality control laboratories.