The paper deals with the properties of mixtures on the base of fly ash and sludge from the metallurgical production. The mixture composition of this group is grounded in the knowledge acquired during testing of various mixtures. The mixtures of sludge and coal fly ash and/or cement after of curing were used for tests. The uniaxial compressive strength of solidified sludge was examined. To understand the behaviour of mixtures in the long term, the prepared mixtures were tested after 14, 28, 56 and 120 days.