Polish coal mines utilize fly ash from power generation as a form of waste recovery in under ground technologies for years. Physical and between them rheological parameters of hydraulii mixtures is essential for prediction of flow parameters in gravitational pipelines systems, which an used widely by mines. The paper presents results of research on generał physical and rheologica parameters of fly ash - water mixtures of different concentration of solids. In aim to show thi differences of properties of mixtures madę with waste from different mefhods of desulphurization which result in wide rangę of physical and chemical properties of fly ash, ash from three differen Polish power plants with different methods of desulphurization have been selected for this research ash from fluidized bed (dry method of desulphurization in fluidized bed, fly ash with products o semi-dry desulphurization method, and fly ash from combustion without any desulphurization. As thi presented in this paper research results show, change of rheological properties of mixtures is strongb related with their table spread and type of fly ash. Results of tests indicate significant similarity o physical and rheological properties of mixture madę with fly ash from each groups (ash from fluidizet bed and ash with semi-dry desulphurization by-products). They indicate also on large differences o rheological properties of mixtures of the same table spread (consistency). This especially visible ii case of mixtures of smali table spread (high solids concentration). Dynamie coefficient of viscosity o mixtures characterized by table spread diameter of 160 mm changes from 0.24 Pas for mixture madi with P-R fly ash up to 0.69 Pa-s for mixtures with B-S fly ash (see Fig. 5). Almost three time: difference of dynamie viscosity coefficient is of great importance from the point of view of hydraulk transportation in gravitational pipelines. It could happened that in a certain pipeline transportation o: mixture characterized by table spread diameter 160 mm madę with fly ash type B-S would bt impossible. Research presented in this paper have been financially supported by the Polish Ministry O: Science and Higher Education within the grant R 0900801 titled "Opracowanie zasad i środków tworzenia sztucznych barier dla podziemnego składowiska odpadów niebezpiecznych w kopalniacł likwidowanych".