This graduation thesis deals with the impact of wood ash on the mechanical, physical, chemical and mineralogical properties of fresh and hardened concrete. Cement binder was replaced by wood ashes in various quantities (10, 15 and 20 wt. %). In the framework of the study, we used four different ashes from companies where wood ash represents a waste from their production.
At the beginning we studied the impact of ashes on fresh concrete rheology. On the basis of the results of compressive, bending and splitting tests after 7 and 28 days, we determined which concrete with ash gives the highest strength and we compared the obtained results to the strengths obtained for the reference concrete without wood ash. By measurements of time dependent length change of the prisms we tried to find out the influence of the wood ash on the concrete shrinkage. After the shrinkage of the prisms had stabilised we put the prisms in water for 42 days. Every week we measured the changes in length and mass of the prisms and determined the dynamic modulus of elasticity, by using a measuring instrument GrindoSonic. At the end we once again determined compressive, flexural and splitting strengths of concrete mixtures and compared the obtained results to the strengths obtained at the age of concrete equal to 28 days.