Practice has tended to differ from that of the UK, with pfa generally finding use as a component of cement, or considered k times as effective as cement (with k ranging from 0 to 0.5) when added at the concrete mixer.
Material with a wider range of fineness has also, in the main, been permitted.
The new European standard BS EN 450 for pfa has, as a result, included limits on material quality which are likely to have implications for UK practice.
The fineness has been set at 40% retained on a 45 µm sieve, compared to the BS 3892, Part 1 value of 12.0%, while the loss-on-ignition (LOI) has reduced from 6.0 to 5.0% (with 7.0% permitted nationally).
The other main change is in the control of material quality, with the requirement that pfa fineness should be within 10% of the supplier’s declared mean.
For most other properties, only relatively minor differences exist between the two standards.
The full impact of BS EN 450 will be felt by the concrete construction industry in 1999, when the European Standard BS EN 206 for concrete, which calls up pfa to BS EN 450, is introduced, making it possible for engineers to more readily apply the new pfa standard. This paper describes the work of study carried out at the University of Dundee, specifically aimed at addressing the technical and practical issues associated with the use of pfa to BS EN 450 in structural concrete.