Fly Ash Concrete on the Basis of Equal Efficiency – Mix Calculation According to the Performance Concept

Project Number 257

In existing regulations for the use of fly ash as concrete addition, requirements concerning the composition of the concrete regarding the minimum cement content, the maximum water/cement-ratio and - on the basis of experience - the thereby resulting class of compressive strength of the concrete are defined.

For some applications reactive additions like fly ash (according to DIN EN 450 or with certificate) can be calculated to the cement content, whereby the efficiency of fly ash is partly considered. The calculation follows a common approach, empirically derived from the compressive strength and the durability of concrete. This common approach is clogged with high safety factors.

A number of damaging reactions or special properties of concretes significantly depends of the mass transfer into or out of the concrete. That means, they directly depend on the pore structure of the concrete. Fly ash as addition to concrete can cause substantially higher efficiency regarding the avoidance of a respective damaging reaction.

The efficiency of fly ash in concrete for different fields of applications shall be demonstrated by an intensive literature research and evaluation of the results of examinations over the last 30 years at the Institute of Building Material Research, as well as by results on current research work on special concretes and special investigations to close the lack of experience.

Based on the results of this work, a new concept for the evaluation for the calculation of fly ash in concrete shall be developed, which should consider the positive effect of fly ash in concrete.

The project is carried out by the Institute for Building Material Research at Aachen University, managed by Prof. Wolfgang Brameshuber, and is technically supervised by a working group of the Working Panel „Power Plant By-products“. The results of the project are expected to be available in March 2007.