Estudo comparativo através da análise de variância para determinação da distribuição granulométrica pelas técnicas de sedimentação e difração a laser

Abstract

The granulometric analysis is a basic tool in the process of characterization of the particulate materials, which can be obtained by numerous methods. However, these techniques are based on different physical principles, which generate different results, causing doubts as to its applicability and reproducibility. The densimeter method is the most applied in the study of soils and is based on the law of Stokes, which relates the size of the particle with the sedimentation velocity in a liquid medium. The laser diffraction method, in turn, is a fast and practical technique in the analysis of particle size and its distribution, and has as physical principle the effect of the laser diffraction, which uses the angular variation caused in the intensity of the incident light as the beam interacts with the particles dispersed in a fluid. The objective was to study two methods of determining the granulometric distribution, standardizing the preparation of samples following the Brazilian Standard (NBR 7181). Five kaolin and quartz formulated samples were used in the # 200 sieve to represent the fine fraction of the soil, where the compositions varied from 100% to 0% the kaolin content and were prepared according to the Brazilian standard NBR7181 . The study material was characterized by X-ray diffraction, thermogravimetric analysis, differential thermal analysis and X-ray fluorescence. The results of the methods were compared statistically by analysis of variance through the F test and correlated by the correlation coefficient obtained by linear regression . It was possible to obtain the granulometric distribution curve of each sample for each method under study, as well as its respective clay, silt and sand fractions. The comparison between the laser diffraction method with and without sample preparation indicated that, statistically, there was no difference in the use of the methods under study. The comparison between the densimeter method and the laser diffraction method with sample preparation reported the same, except for the composition CAU25. The correlation results showed a strong dependence between the densimeter method and the laser diffraction method with sample preparation, indicating a direct and direct correlation with 95% confidence.