Synopsis
Portland–pfa (pulverized-fuel ash) cements containing 20-40% (by weight) pfa have been prepared in the laboratory both by intergrinding the ashes with clinker and by blending with cement. The ashes were obtained from four base-load stations and the cements and clinker from two UK cement works. Cement properties have been assessed according to BS 4550 and scanning electron microscopy was used to examine the effects of grinding upon the pfa particles. The work has shown that intergrinding leads to an improvement in the water-reducing properties ofcoarse pfas and also in their pozzolanic activity as indicated by compressive strength development at later ages. Setting times have been found to be essentially the same for blended and interground cements, both being considerably longer than for typical ordinary Portland cements. The results of the work on laboratory-prepared cements have been confirmed on factory-produced cements. Thus the results of this investigation indicate that, provided pfas are chemically acceptable, they can be used for Portland-pfa cement manufacture by intergrinding irrespective of their coarseness.
