Use of spent catalyst from catalytic cracking in fluidized bed as a new concrete additive

Abstract

The hydration of cement paste was studied as a function of addition of spent catalyst for catalytic cracking in fluidized bed, as compared with similar use of microsilica and fly ashes. The course of the hydration process was studied by TG and DTA, X-ray diffraction, and infrared absorption methods. The time of setting of freshly prepared pastes and the compressive and bending strengths of sample beams after the 7th and 28th days of setting were determined. The contents of Ca(OH) 2 in the pastes at different times of hydration were determined from the results of the thermogravimetric studies. The studies disclosed the pozzolana nature of the additives. The ability of combining with Ca(OH) 2 was similar in the spent catalyst and microsilica. In the presence of the spent catalyst, the hydration process was strongly exothermic which promoted rapid setting of the cement paste. Calcium carbonate–aluminates formed in the system affect favorably the strength of the concretes formed.