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In certain cases, concrete constructions with alkali-reactive aggregates can achieve sufficient resistance to alkali-silica reaction (ASR) by using cements with low effective alkali content (low-alkali cement). So far, the simplified classification of total alkali content does not fully, if at all, account for the effect of various blastfurnace slags and other cement main constituents like limestone (LL) having on the cement’s effective alkali content.

Aim of the research project

The IGF project 19295 N iintended to devise a testing and assessment system that better reflects the cements’ material properties. To do so, assessment criteria should be derived for cements in various applications – with and without external alkali supply – and in combination with aggregates of various alkali reactivity (e.g. to include criteria for moderately alkali reactive aggregates, potentially class E II-S).

Derivation of assessment criteria

CEM I low-alkali cements, road pavement and laboratory cements of different composition should be examined by means of pore solution expression test and bleeding solution test. The result, reflected by the hydroxide ion concentration of the extracted pore solution and the bleeding solution above the hardened cement paste with a water/cement-ratio of 1.00, should then assess the effective alkali content of the cement.

The hydroxide ion concentrations should be compared with the results of laboratory concrete testing (ASR performance tests) and the concrete tests with outdoor exposure (see figure above) that have been conducted over the last forty years. Together, this should form the basis for proposals regarding assessment criteria for cement’s effective alkali content.

Background and goals of the research projects

DIN 1164-10 defines the characteristic “low effective alkali content” in simplified form as the total alkali content and, if applicable, on the basis of the slag content. VDZ iintended to develop a testing and assessment system based on a new approach to better reflect the cements’ material characteristics. Assessment criteria should be derived from pore solutions expressed from hardened cement paste as well as from the experiences gained with different concrete compositions stored in an outdoor exposure site and tested in ASR performance testing.

Sponsors

The IGF project 19295 N of VDZ Technology gGmbH 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.

This research project has been concluded

Person to contact

Do you have questions regarding this project?

Dr Christoph Müller
Concrete technology

+49-211-45 78-351
bte@vdz-online.de

Other items of possible interest

01.08.2011

Research projects

Procedures for E II aggregates

VDZ and the Brandenburg Technical University Cottbus-Senftenberg (BTU) investigated whether it is possible to define an alkali sensitivity class E II-S on the basis of the 40 °C concrete test with cloud chamber storage. In addition, criteria for the rapid test procedure and the 60 °C concrete test as well as the BTU-SP rapid test were also derived.

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