Petrographische Beschreibung von Gesteinen aus Westösterreich hinsichtlich ihrer Alkali-Reaktivität

On the basis of various rocks from western Austria, a mineralogically oriented possibility was sought to obtain first insights into a potential alkali-silica reactivity (ASR) of the selected rock types after appropriate exposure to alkalis. In addition to the difficulty of accessibility of sample material, care was taken to select and examine typical representatives of the lithologies in the form of handpieces or rock cores from the respective formations. The samples were described macro- and microscopically. From selected pieces, sand fractions were prepared, which were sampled for further understanding of their alkali-silica reactivity by means of the rapid test according to ÖNORM B 3100. In a second step, a modification of the rapid test was made with selected sand fractions, in which instead of the unit cement, a binder combination of two cements was selected with a significant proportion of hydraulically effective blast furnace slag with no further changes in the experimental procedure. It was examined whether a potential ASR of the aggregate can be changed by the choice of the binder. For this purpose, after the test procedure from the mortar prisms also thin sections were made to look at these in detail and to find traces of a possible ASR in the form of cracks or gel collections. In the last instance, with the scanning electron microscopy some thin sections have been searched for ASR gel formations and assigned as such to this reaction. However, a general classification of the crack formation to a damaging ASR concrete reaction proved to be mostly not possible. A correlation between different influencing factors and the elongation of the mortar prisms could not be proven.