Utilization of steel slags and lignite fly ashes in the production of concrete for special applications

The industrial by-products discussed are steel slags (electric arc furnace slag as concrete aggregate and ladle furnace slag as supplementary cementing material) combined with fly ash. Regarding their properties, the materials are tested for durability and physical, geometrical and chemical properties and it is shown that slag aggregates have very good mechanical properties and durability, while no expansion is observed, and also that ladle furnace slag has some pozzolanic properties which are enhanced with fineness and can be used for the production of concrete at cement replacement rates in the order of 20%. Concrete mixtures with the above industrial by-products were prepared and tested for their mechanical properties and durability. The results show that by substituting the coarse aggregate of concrete with steel slag aggregates, mechanical strength is improved by 10 to 40%. It is possible to produce high-strength concrete (>70 MPa compressive strength) by using 65% by weight industrial by-products. Some of the laboratory trial mixtures were applied in demonstration projects and it is shown that C25/30 concrete can be produced by using 93% by weight industrial by-porducts. Also, the proposed concretes show minimal amount of heavy metals leaching. With this thesis is shown for the first time that Greek steel slags can be used together with fly ash to produce concrete of a high environmental profile and technical advantages suitable for special applications