Advanced External Sulfate Attack Testing and Performance Specifications: Different Sample Geometries Testing

Abstract

External sulfate attacks induce severe deterioration of concrete because of several phenomena: leaching, precipitation of expansive products, aggregates loss, and cracking. A new methodology has been developed to assess sulfate resistance of cement-based materials. We can actually estimate the nature of leached and precipitated minerals, and the microscopic volume variations due to each of the principal sulfate attack phenomena, from relatively simple monitoring parameters: sample mass, hydrostatic weighing, and the amount of leached hydroxide. Quantitative information is given on the mineralogical volume or mass variations, leading us to a phenomena decoupling and a better understanding of the sulfate attack mechanism. After we established the microscopic volume variation scenario, we defined a new performance criterion, the averaged density, capable to describe the tested sample performance variation according to the sample internal state indications given by this criterion. We applied the developed strategy on three different filled and hollow geometries in order to study the effect of the sample geometry on sulfate attack mechanism. The study shows almost the same degradation mechanism: the same microscopic volume variations entrained by the different sulfate attack phenomena. However the hollow tubes promote different precipitated mineral than the two others geometries, due to the different ionic and pH profiles between filled and hollow samples which affects the nature of formed sulfate minerals.