Behaviour of different aggregates under accelerating conditions in ASR testing methods

To avoid damages of concrete pavements of motorways resulting from alkali silica reaction (ASR), the Federal Ministry for Transport, Building and Urban Development (BMVBS) introduced a package of special rules in the document ARS 04/2013. These rules specify measures to assess the ASR resistance of coarse aggregates in concrete mixtures for concrete pavements in moisture class WS. Experiences with the application of these rules in regions with known damages showed that the experimental testing methods (concrete test at 60 °C with external alkali supply and FIB climate simulation chamber) suit to identify coarse aggregates with ASR damage potential properly. Since the publication of ARS 04/2013 the aforementioned methods have to be applied also in regions where no ASR damages are known according to the state administration. It is not clear if the experiences with the testing methods can be transferred to all regions of Germany and the local aggregates without restrictions.

With this in mind, the research project should generate essential knowledge on the behaviour of different aggregates under accelerated conditions within ASR testing methods. The target was to obtain with different testing methods a consistent assessment of the alkali sensitivity of aggregates and concretes respectively and to clearly identify expansive reactions that are not caused by ASR. Furthermore it was important to assess if the observed effects have a practical meaning or if they only result from the accelerated testing conditions. On the one hand there might be artefacts resulting from the test methods and specialities of the gravel (e.g. chemical and mineralogical composition, structure, emission of alkalis from the gravel) that might be responsible for high strains under the testing conditions. These strains are not necessarily connected to an ongoing alkali silica reaction inside the concrete. On the other hand there may be a real ASR damage potential that has to be identified and evaluated by the tests.

The results of the research should help to evaluate aggregates for the use in concretes for motorway pavements (moisture class WS) safely and practice-oriented at the same time. It has to be ensured that the current level of safety is kept up without dismissing suitable locally available aggregates.

Supported by

The IGF project 19077 BG of VDZ gemeinnuetzige GmbH – VDZ gGmbH, Tannenstrasse 2, 40476 Duesseldorf was supported by the AiF within the framework of Industrial Collective Research (IGF) of the Federal Ministry of Economic Affairs and Energy on the basis of a decision of the German Bundestag.