Hydration of the equilibrium catalyst (Ecat) calcium hydroxide system

The pozzolanic properties of an equilibrium catalyst (Ecat), a waste produced worldwide at fluidized catalytic cracking units of oil refineries, have been studied in cementitious matrices. The consumption of calcium hydroxide is usually taken as a mean to assess the pozzolanicity of a material, independently of the formation of the hydrated phases formed from the pozzolanic reactions. The use of thermal analysis methods allows the identification and quantification of the products formed by hydration and pozzolanic reactions, based on the loss of their chemically combined water during analysis. In the present study, TG/DTG techniques were used to quantify the amount of C-S-H, C-S-A-H, C-A-H, and calcium hydroxide in lime-Ecat pastes, containing up to 40 % of Ecat, aged for 1–28 days. The influence of the content of these phases on the mechanical properties of the resulting samples was also investigated by axial compression. The results confirmed the pozzolanic activity of Ecat, from the measurement of calcium hydroxide consumption, associated with the formation of the hydrated phases, which increased with hydration time.