Use of computer assisted image analysis for the determination of the grain-size distribution of sands used in mortars

A quantification procedure for constructing the sieving curves of sands used in mortars, from two-dimensional data obtained by image analysis of thin sections, has been developed. To test the suitability of this procedure, thin sections were made from ten fluorescent epoxy-impregnated mortars, containing five different sands of which the sieving curves had previously been determined. Whereas previous investigations were typically based on independent and individual micrographs, a new approach has been adopted in which measurements are performed on single composite images. Two stereological models, based on cubic and spherical particles respectively are applied to the examples and the results compared with the sieving curves. The results obtained show a reliable congruence, especially for the spherical model and when shape factors of sectioned grains are high. Sieving curves and grain-size distribution curves established from image analysis may have virtually the same precision, but the latter has a lower reproducibility.