engleski

Evaluation of using sewage sludge ash in the cement industry: Case study of Zagreb, Croatia

The potential for using sewage sludge ash (SSA) as a supplementary cementitious material has been investigated. The ash was used as a replacement for up to 30% of Portland cement in the production of cement mortars. The chemical composition and physical properties of the ash generated at 900°C are presented. The use of SSA in cementitious materials decreases workability and this is compensated by the addition of super-plasticizer. Experiments were repeated with two types of commercially available Portland cement (CEM I 52.5N and CEM II/B-M (S-V) 42.5N) and these showed significant differences in behaviour at replacement levels of 30%. Nonetheless, the results demonstrate that the mechanical properties (compressive and flexural strength) of cement mortars containing SSA are satisfactory. Gas permeability can be used to indicate the durability of the cement mortar and this improved with SSA addition. The results demonstrate that future use of SSA from the Zagreb WWTP in cement-based materials is technically feasible and is an alternative to landfilling from both an economic and environmental point of view.

sewage sludge ash, cement, mortar, landfilling, Croatia

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