Sulfate resistance of RFCC spent catalyst-blended Portland cement

Abstract

The reuse of spent catalysts from residue fluid catalytic cracking (RFCC) units as pozzolanic materials in cement and concrete production offers a number of important benefits. In spite of all these benefits, the durability performance of the produced blended cement is an important issue to be considered. This study investigates the effects of RFCC spent catalyst on durability performance of hardened Portland cement paste in a highly aggressive sulfate environment. The 28-day cured paste specimens prepared from binary cement mixtures incorporating different replacement levels of 0, 10, 20, and 30% (by mass) RFCC spent catalyst at a constant water-to-cement ratio of 0.30 were exposed to 10 mass% solution of magnesium sulfate. The accelerated sulfate attack under alternative cycles of wetting and drying was studied by monitoring the changes in compressive strength, length, and mass of specimens and also by the application of XRD, SEM and EDX techniques. Based on the results and a comparison with plain Portland cement, binary cement mixtures exhibit a higher rate of deterioration in spite of their significantly improved compressive strengths resulted from pozzolanic reaction.