Calcareous fly ash as a main constituent of common cements

Abstract

The results of tests concerning properties of cements containing calcareous fly ash obtained by a process of lignite combustion are presented in the paper. The scope of the study includes: Portland fly-ash cements CEM II/A,B-W; Portland composite cements CEM II/B-M containing a mixture of calcareous fly ash (W) and granulated blast furnace slag (S), siliceous fly ash (V) or limestone (LL), as well as pozzolanic cements CEM IV/B-W and CEM IV/A,B (V-W). Standard properties of cements, including cement water demand, mortars consistency and mechanical properties, are described in the paper. The obtained results have proven that use of calcareous fly ash in the production of common cements, especially Portland composite cement CEM II/B-M, is possible. Cements containing calcareous fly ash, regarding setting time, soundness and compressive strength, exhibit similar properties to the ones of cements with additives (CEM II – CEM V), available on the market for a long time. The use of calcareous fly ash in greater amount in cement composition (above 20%) results in the increased water demand and deterioration of mortars rheological properties. The process of intergrinding of fly ash with clinker in cement production results in decreased negative impact on cement water demand.