NEW APPROACH TO NATURAL AGGREGATE REPLACEMENT BY INDUSTRIAL WASTES IN CIVIL ENGINEERING INDUSTRY

This contribution is focused on the utilization of industrial wastes (steelmaking slag and recycled concrete aggregate) in civil engineering for an environmentally friendly concrete production. Our study is aimed to monitor compressive strengths of concrete samples prepared with partial or complete replacement of natural aggregates by selected fraction (fractions 4-8 and 8-16 mm) of industrial wastes. The experimental part has been carried out in two parts. First part of our experiment considers natural aggregate replacement by washed recycled concrete in the concrete production. For research of selected natural aggregate replacement by recycled concrete aggregate ten different mixtures (called R1-R10) at solid/liquid ratio of 0.55, including admixture has been proposed. In these mixtures, both fractions (4-8 and 8-16) of natural aggregate have been replaced by the same representation of recycled concrete in the variation range up to 100%. The results showed that sample prepared with recycled concrete aggregate (4-8 mm: 100% and 8-16 mm: 60%) has reached the same value of compressive strength (34.7 MPa) after 28 days of hardening in comparison with reference sample (only natural aggregate, 34.4 MPa). The second part of this paper is aimed to natural aggregate replacement by selected fractions of steelmaking slag in concrete mixture. Experiments showed that concrete samples with natural aggregate replacement by two different fractions of slag (S1 and S2; 45.8/48.7 and 45.7/49 MPa) reached higher compressive strength after 28/90 days of hardening in comparison to sample prepared only with natural aggregate (S4; 43.6/46.8 MPa). From all of these mixtures, cubes with edge 150 mm were prepared and tested in compression strength after 14, 28 and 90 days. From the obtained results follows that washed recycled concrete and steelmaking slag can be successfully used as a natural aggregate replacement in concrete production and has not negative effects on the properties of hardened concrete. However, using of these selected wastes in the praxis requires some important properties (durability and corrosion) of recycled concrete and steelmaking slag concrete to investigate.