Activated fly ash/slag blended cement

This paper presents the results of the preparation of an ecological cementing material from granulated blast-furnace slag (GBFS) and Class C fly ash (CCFA). The desulphurization gypsum, calcined at 600-800 degrees C for 0.5-1.5 h, works as the main ingredient of the activator in the cementing material. The optimized formulation of the cementing material was obtained with the aid of factorial design method: slag, 70%; CCFA, 18%; activator, 12%. The "partial super-fine grinding process" was adopted to improve the performance, i.e., 85% of the mixture is ground to Blaine fineness of 3500 cm(2)/g, 15% further ground to around 5000 cm(2)/g. The compressive strength of 28 days of the cement mortar is up to 49 MPa and flexural strength 8.4 MPa. The hydration products, investigated by SEM and X-ray diffraction, are mainly ettringite and C-S-H gel. (C) 2007 Elsevier B.V. All rights reserved.