In IGF project 21386 N, VDZ investigated the influence of alkalis released from aggregates on a deleterious alkali silica reaction (ASR) in concrete. The tests have shown that the majority of the aggregates release only a small amount of alkalis (RILEM AAR-8). Only one basalt was found to have high alkali release. Two other basalts and one rhyolite released alkalis to a moderate extent. Based on the observations, there is currently no need for action in Germany as long as no crushed sands or fillers of basalt and possibly rhyolite are used in the production of concrete.
The influence of the releasable alkali content of aggregates on the ASR resistance of concretes was investigated using concrete tests (RILEM AAR-10 and -11 and outdoor storage) and expressed pore solutions. A non-reactive (accelerated mortar bar test) but alkali-releasing crushed basalt sand significantly promoted the alkali-silica reaction of an alkali-reactive coarse greywacke. This was due to the contribution of the crushed sand to the alkali content of the pore solution.
