Susceptibilidad a la corrosión de agregados pétreos para hormigón a partir del estudio sobre superficies pulidas
The susceptibility to corrosión of quartzose sandstone in alkaline médium was study. It is known that it is a highly reactive material when it is used in concrete of portland cement. Corrosión tests were made over polished surfaces to anaiyze the rock damage, reaction velocity and the identity of the corroded minerals. Samples were corroded with a NaOH IN solution at 80 C, and the evolution of reaction was study by means a polarization microscope, which allows to record an image each seven hours in the same section. The results were treated statistically using multivariate analyses over the pixel luminosity of digitalized images. It was performed a covariance matrix from the data matrix and the principal components were calculated. The results were plotted in a 3D graphic where it is possible to notice the relief sampic, which reflects the differential attack in different sectors. The upper dots correspond to quartz grains and the depressed zones to the opaline cement. Later, a map with the isoluminosity curves were made to show reaction zones. The application of this method to different minerals and rocks is proposed with the aims to evalúate preliminary the potentíal reactivity in aggregates used in concrete and to know which are the materials responsable of damage in hardened concrete.