INCORPORATION OF SLUDGE FROM A WATER TREATMENT PLANT IN CEMENT MORTARS

摘要

The characterization of the sludge from a Portuguese water treatment plant is presented. Dewatered sludge contains basically water, calcium, aluminium and silica, with an organic matter content of about 6%. The mineralogical constituents in the heated sludge are mainly calcite and clay minerals. Gibbsite is present only in the sludge heated at 105℃ and calcium aluminate and calcium oxide are only present in the sample heated at 700℃. Thermal treatment does not remove the entire polymer and coagulant initially within the sludge. Sludges dewatered or heated at 105℃ inhibit the setting and hardening of the paste. Incorporation of sludge in mortars can only be feasible after treatment of the sludge at not less then 450℃ even thus with an increase of the initial setting time and a decrease of the mechanical strength.