Decalcification of activated paper sludge – Fly ash-Portland cement blended pastes in pure water

摘要

Decalcification in pure water of ternary Portland cement (TPC) pastes, containing thermally activatedudpaper sludge and fly ash, has been evaluated from the leaching of Ca2+ in pure water at the temperatureudof 20 C during 90 days. Monitoring of calcium loss showed that the leaching kinetics are controlled byuddiffusion. The degradation of the material over time is estimated from the calcium effective diffusivity.udA similar study of plain ordinary Portland cement (OPC) pastes was carried out for comparison. Theudresults showed lower effective diffusion coefficients of calcium in the case of the TPC pastes. This behaviourudis related to its microstructure, which is denser than that of OPC as a result of the pozzolanic activityudof both additions.