Violeta Bokan Bosiljkov : Alkali carbonate reaction in mortars – influence of mineral binder and time

Abstract: The lecture will discuss the process of alkali-carbonate reaction (ACR) in mortar, between crushed dolostone aggregate grains and three different mineral binders: Portland cement CEM I (according to the EN 197-1 standard), pure calcite lime putty, and combination of lime putty and zeolite tuff. The source of the aggregate is typical Slovenian late digenetic dolostone rock. The specimens were exposed to normal and accelerated conditions regarding ACR. The progress of ACR was studied using a petrographic microscope and scanning electron microscopy with X-ray microanalysis (SEM/EDS) after 3 and 6 months, and after 2 years. The results obtained at microstructural level show that ACR is progressive with time for all three binders studied. It reflects in the process of aggregate grains’ dedolomitization and in the formation of secondary calcite in the binder, as well as in the formation of a new phase at the edge of the altered aggregate grains. For particular exposure conditions the extent of recrystallization depends on the binder type.  Moreover, the binder type also influences the composition of the new phase.