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Standard test for alkali reactive rocks

Objective



Alkali Aggregate Reaction (AAR) is today reported in numerous countries around the world. Many researchers within the field of concrete technology are dealing with this topic. In the last years, the number of papers on AAR has increased very much as seen from e.g. the proceedings from the conferences 'Durability of Building Materials and Components' and 'International Conference of Alkali Aggregate Reaction'. The reaction mechanism is very complex and depends on the type of geological material. For example, in Denmark the reactive aggregate is low density porous flint, in United Kingdom chert, in Belgium porphyries rocks, in Sweden limestone's and mylonitic rock, in Norway different types of dense volcanic rocks, quartzite and other high density rocks; in other of the European countries there is no knowledge of the type of reactive aqgregate. In some of the European countries there are strong restrictions on aggregates due to AAR. These restrictions are based on national standard tests generally built on empirical knowledge of the national types of aggregates. In Denmark there are only restrictions on low density flint and the national tests will accept imported high density reactive aggregate without any problems even if the aggregate is reactive measured by other methods. Similar situations exists in other countries.
There are, at the moment no CEN or ISO effort to solve the problems of testing for reactive alkali aggregate rocks. A RILEM group, in which several of the partners are participating, are working in the similar area, but in world scale. The RILEM procedure is, however, extremely slow and results can probably first be achieved on a 10 - 20 years basis.
The coming European standard for concrete aggregates proposed by the committee CEN/TC154/SC the document 'Proposed draft for aggregates for concrete including those for use in roads and pavements', January 1994, suggest that 'The combination of aggregates and cement shall be assessed using procedures described in the national standards and regulations valid in the place of use'. The proposed draft does not take in account inadequate national test procedures for imported aggregates.
It is the purpose of this project to elucidate the different test methods used in the European communities and suggest a set of standard test methods. The foreseen project results will enable researcher to assess AAR in a more sense way when designing new concrete products and hence secure concrete quality.
It is believed that Round Robin test and an European recommendation could be adopted within 2 - 3 years after completion of the present project.

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PC LABORATORIET A/S
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