A wide range of materials were considered to fully examine the influences of BS EN 450 pfa on concrete performance. The work included pfa covering, or just at the limit of, the BS EN 450 fineness and LOI ranges, from various UK sources. The Portland cement (PC) used was of class 42.5N to BS 12 and the aggregates of 20mm maximum size and sand to Zone M of BS 882.
The initial series of mixes was used to assess the effect of pfa fineness and LOI on concrete strength and covered the range of binder contents 250 to 550 kg/m3 , with 30% pfa replacement. The free water and coarse aggregate contents of these mixes were fixed at 175 and content reduced with increasing binder content to maintain the yield.
Compressive strength tests on 100 mm concrete cubes were carried out at ages up to 28 days after curing in water at 20˚C.