Influence of Fly Ash on the Durability of Road Concrete with Alkali-sensitive Aggre-gates
Project Number 275
According to applicable standardisation the use of fly ash in road concrete is not allowed as its usability has not been proven, so far. To prove the technical usability of fly ash in road concrete a new research project titled ”Influence of fly ash on the durability of road concrete with alkali-sensitive aggregates” (project number 270) has recently been started.
The recent damages of concrete pavement that have arisen predominantly were related to a damaging alkali-silica reaction, i.e. a reaction of the alkalies from cement with alkali-sensitive aggregates. In the damaged concrete pavements aggregates were used, which so far had not been classified as alkali-sensitive.
In this project fly ash containing road concretes will be comparatively examined with the procedure according to the “Alkali Guideline” of the German Committee for Structural Concrete (DAfStb) and with a new “Performance Testing Method”. The examinations are to be performed with road concretes of common composition based on two cements of different alkali contents, whereby the cements will be partly exchanged by two fly ashes with different alkali contents in order to demonstrate the influence of fly ash on the durability of concrete with respect to a damaging alkali-silica reaction. If it can be proven that fly ash avoids a damaging alkali-silica reaction in road concrete an introduction of fly ash in the legislation of road construction will be possible.
Starting on April 1, 2006, and finishing on March 31, 2009, the project is carried out by the Institute for Building Materials and Construction at the Technical University of Munich and is technically supervised by a working group of the working panel "Power Plant By-products".