Effects of long-term magnesium sulfate crystallisation tests on abrasion and durability of andesite aggregates

Abstract

The durability of aggregates against salt weathering is calculated after five cycles of immersion in a magnesium sulfate solution followed by drying according to the relevant European standard (EN 1367–2: 2010). The aim of the study is to investigate the long-term durability of aggregates by increasing the number of cycles of the salt crystallization test from the standardized five to a maximum of 35. Three andesite types from Hungarian quarries were tested representing three different localities. The weight loss of the specimens was determined after every 5-cycle set. Results were documented for three size-fractions 10.0/11.2 mm, 11.2/14.0 mm and the 10.0/14.0 mm, respectively. Relationships between immersion-drying cycles and magnesium sulfate values were described by the Pearson-coefficient. According to the test results, the magnesium sulfate values followed linearly increasing tendencies in the course of the long-term salt crystallization tests. Parallel to the salt-weathering tests, the changes in the mechanical properties of the salt-attacked aggregates were also detected by micro-Deval tests (EN 1097–1: 2012). The changes in micro-Deval coefficients were calculated in the form of a decay factor as a function of sulfate cycles. The results suggest that the micro-Deval coefficient does not rise after a certain salt cycle; i.e. higher number of salt-crystallisation cycles does not necessarily reduce the micro-Deval coefficient of studied andesite lithologies.