Comparing circulating fluidised bed fly ash and limestone as additions for cement

Abstract

[Abstract:] Circulating fluidized bed combustion (CFBC) power plants produce as by-product large ash particles with elevated calcium content. They are not commonly accepted as addition for cement although presenting pozzolanic potential. To enhance the activity of this material, the CFBC ash was ground to fineness equal to that of the cement, simulating a joint milling with the clinker. This ground fly ash (GFA) was included in blended cements in ratios of 10%, 20% and 40%. These new cements with GFA surpassed 52.5 MPa at 28 days for even 40% of substitution. Contrasted with limestone addition, the most used in Europe, the cements with GFA presented higher compressive strength, better durability with the only drawback of a slight reduction in workability. This CFBC fly ash could be used as clinker replacement once ground to similar fineness than cement allowing high reductions in clinker consumption and its consequent carbon footprint reduction.