Resistance to acid corrosion of blended cements mortars with spent fluid catalytic cracking (sFCC) catalyst

Abstract

Spent fluid catalytic cracking (sFCC) catalyst is a residue that is produced in high volumes by the petrochemical industry and has shown a high potential to be used as a supplementary cementitious material (SCM). This article assesses the sFCC effectiveness as a SCM in mortar based on ordinary Portland cement (OPC), as well as its chemical resistance when the materials are immersed in sulfuric (H2SO4), acetic (CH3COOH) and hydrochloric acid (HCl). The performance of the sFCC was compared to other commercially available mineral additions, such as silica fume (SF) and metakaolin (MK). The results show a mechanical strength increase of up to 17% when the sFCC was included, compared to a control mortar without mineral additions. Immersion in H2SO4 during 90 days led to the formation of gypsum and a loss of chemical resistance up to ~25% in mortars with MK and sFCC. In the samples immersed in HCl, and particularly those made with sFCC and MK, Friedel’s salt was identified due to the ingress of Cl- and the subsequent reaction with the monosulfoaluminates formed during cement hydration.  Immersion in acetic acid led to a loss of strength of up to 57% and 37% in mortars with OPC and sFCC, respectively. Immersion in HCl leads to a stronger attack for blended systems, followed by CH3COOH and H2SO4. The mortar with 20% of sFCC exhibits the best performance, especially in the presence of sulfuric acid.