PSI - Issue 22

186 J. Gonçalves et al. / Procedia Structural Integrity 22 (2019) 181–188 J. Gonçalves, C. Oliveira, C. Reis, A. Soares, P.Silva / First Internati nal Symposi m o Risk and Safety of Complex Structures and Components (2019), Porto, Portugal

Figure 3 - Mean values for parameter a and b, obtained in laboratory tests.

Figure 4 - Values of L, lightness, obtained in laboratory tests.

The results obtained in this study regarding colour, match the data that Pietro et al. (2011) obtained. Since the variation of the parameters * a and * b are basically non-existent, we chose to present in Table 2 the comparison of the two materials (in order to validate the results). Sanmartín, ( P. Sanmartín; B. Silva; and B. Prieto, 2011) refers that the studied material is a polymineral rock in which the gloss of each mineral is different and the overall surface gloss depends on the exposed area of each mineral. Most of the minerals in ornamental granites tend to split along definite crystallographic planes (cleavage planes) giving rise to smooth surfaces, and therefore the treatments used to achieve the different finishes can create small flat surfaces that may cause a slight increase in gloss .