Morphometric Characterization of the Sand Fraction in a Sand Grain Image Capture System1

Abstract

-Morphology studies assume significant importance in analysis of phenomena of granular systems packaging, in particular with a view to the use of the technique of soil stabilization named particle size correction in forest roads. In this context, this study aimed to develop and operationalize a Sand Grain Image Capture System and, hereby, determine the morphological indices of the sand fractions of two sandy soils called João Pinheiro (JP) and Cachoeira da Prata (CP). Soil samples, air-dried, were sieved (2.0 mm nominal mesh size) for removal of gravels. The materials that passed through the sieve were subjected to dispersion, washing in 0.053 mm nominal mesh size sieve, removal of organic matter and iron oxides to obtain the clean sand fractions. Subsequently, each soil sample was sieved for separation into twelve classes, between the diameters of 0.149 mm and 1.190 mm, using a Rotap shaker. Next, tests were carried out to characterize the morphometric attributes of the twelve classes of sand fractions of the soils studied. For validation of the performance of the Sand Grain Image Capture System, the results were compared to those obtained using a standard procedure for image analysis. The analysis of the results led to the following conclusions: (i) the sand fraction of the JP soil presented higher values for the morphometric indices roundness, elongation and compactness compared to sand fraction of the CP soil; and (ii) the Sand Grain Image Capture System worked properly, with practicality.

Effect of Granite Residue Incorporation on the Behavior of Mortars

“…It can be observed that the granite residue presents very irregular grains, since the process that gives origin to the material is the lamination that causes non-uniform changes in the material [6,9,10]. It is worth mentioning that, as widely reported in the literature [47,48], the natural sand extracted from the river presents its very regular morphology, with a circular and uniform shape. Thus, the morphology alteration promoted by the substitution of the residue caused changes in the technological properties of the mortar, as will be discussed in the sequence.…”

“…The increase of the flow stress is closely related to the morphological form of the sand grains and the grain of the residue (Figure 5). While the sand presents uniform rounded and regular grains, due to the weathering process that originates these grains [47,48], the granite residues are not uninform, irregular particles, without a standard format. Thus, mortars made predominantly with sand (composition 0%, 20%, and 40%) have high penetration rates, because the grain shape favors the initial movement of the mortars, while the mortars containing the largest proportions of granite (100%, 80%, and 60%) present difficulties to initiate the movement, evidenced by the low penetration indices that prove higher values of yield stress, since more effort is needed to break the inertia due to the stiffness caused by the grains of irregular shape.…”

Sand fractions micromorphometry detected by Vis‐NIR‐MIR and its impact on water retention

“…The procedures for the micromorphometric analysis is described in Cremon et al (2009) and Viana et al (2016). Samples of each sand sub‐fraction were placed in Petri dishes and photographed using a combination of an electronic microscope and a digital camera (Figure 1).…”