Avoidance of a Damaging Alkali-Silica Reaction in Concrete by Using Fly Ash

Project Number 272

Despite existing international experience and normative coverage the effect of fly ash in concrete regarding the avoidance of a damaging alkali-silica reaction is not accepted in German legislation.

Examinations of concrete and mortars with different fly ashes and cements with different alkali contents by using different alkali-sensitive aggregates - carried out by Munich Technical University - should prove that the combination of fly ash with high-alkali cements could be used to produce concrete with alkali-sensitive aggregates instead of cements with low alkali content. In addition to these examinations the project focus on the investigation of those reactions, which show the contribution of the ashes to avoid a damaging alkali-silica reaction.

On the basis of chemical tests of pore solutions the bond of the alkalies in the reaction products of the hard coal fly ash will be evaluated. The influence of the ambient conditions (temperature) and the availability of calcium are to be considered, also. Additionally, the reactivity of fly ash and its influence on the effective alkali content of the cement regarding different conditions shall be specified in more detail.

Starting on September 1, 2005, and finishing on August 31, 2007, the project is carried out by the Research Institute of the Cement Industry (FIZ), Düsseldorf, and is technically supervised by a working group of the Working Panel “Power Plant By-products”.