Modification of the properties of concrete by a new pozzolan - A waste catalyst from the catalytic process in a fluidized bed

The zeolitic waste material studied (fluidized bed cracking catalyst, FBCC) is characterised by a content of more than 90 wt.% of SiO2 and Al2O3, a mean grain size within 20-80 mum, and a specific surface above 100 m(2)/g. Its chemical composition makes it similar to some fly ashes and metakaolin. The present work was devoted to the study of the mechanism of interaction of FBCC with Portland cement and of the pozzolanic activity. Concretes were made with FBCC additions of 10% and 20% (relative to the mass of cement) used as a substitute for the sand aggregate fraction, and the following properties of the concretes were determined under nonaggressive conditions: compressive strength, porosity, water absorption, frost resistance, and steel passivation ability. It has been found that FBCC has pozzolanic properties, and its pozzolanic activity depends on its grain size. FBCC favourably modifies the porous structure of the concretes, increases their compressive strength, density, and frost resistance, and reduces water absorption. The effectiveness of FBCC increases under conditions of strong dispersion. FBCC does not deteriorate the steel passivation ability of concrete when used as a 10% additive, but at a content of 20 wt.%, it can make difficult the formation of a passive layer that conforms to the Polish standards. (C) 2002 Elsevier Science Ltd. All rights reserved.