PROPERTIES OF WASTE CATALYST-CEMENT MORTARS: IMPACT OF ORGANOCLAY TYPE

The strategy for reducing environmental impact of the cement industry is to reuse industrial waste or to find supplementary materials for cement substitution. In Lithuania, 200 tons of fluidized bed cracking catalyst waste (FC) are produced annually. FC waste has high content of silicon and aluminum oxides and, therefore, presents pozzolonic characteristics and can be utilized in cementitious materials. Organically modified clays are nano particles, small quantities of which can improve the microstructure and properties of cement based materials. In this paper, the combined effect of two simultaneously applied substitutes on properties of mortar was investigated. Cement was partially replaced by three organically modified nano clays (OC) with different basal spacing (d001), while aggregate was substituted by fluidized bed cracking waste catalyst (FC). The aim was to evaluate mechanical strength and water absorption of mortars by replacing from 0.5 % up to 4 wt% of cement by three OC, and 5 % or 15 % of aggregate by industrial byproduct. Another purpose of this study was to identify which of OC was the most appropriate for cement substitution in the mortar. It was found that due to cement replacement by all OC, flexural strength of modified mortar increased substantially (from 3 % up to 16 %), while compressive strength increased slightly (up to 4 %) and only for samples with 0.5 % of OC. In waste catalyst - cement mortars no significant increase of strength was observed due to cement substitution by OC, and, therefore, the optimal cement replacement level was found to be less than 1 wt%. However, due to OC application, water absorption of mortar was substantially retarded, and retardation increased with the increment of d001 of OC. The obtained results suggest the idea that d001 of OC is not the major factor during the selection of appropriate OC, and, thus, the type of organic modifier should be taken into account.