THE FOURTH EDITION OF THE INTERNATIONAL CONFERENCE “NEW TRENDS IN ENVIRONMENTAL AND MATERIALS ENGINEERING” TEME 2017 RESEARCHES REGARDING THE UTILIZATION OF LIDONIT AS PARTIAL REPLACEMENT OF THE AGGREGATE IN CONSTRUCTION MATERIALS Liliana ANDONE, Andrada Gabriela ALEXANDRU, Marius BODOR “Dunarea de Jos” University of Galati, Romania Introduction Methodology Over the last decades in concrete composition different materials were used, with the purpose to utilize some industrial wastes or to reuse aggregates from demolitions. In the concrete composition aggregates consists an important part (at least 75% from the concrete volume is represented by the aggregate), and greatly influences the properties of concrete. Although formerly, the aggregate was considered as an inert material, dispersed in the cement paste mass, today the conception regarding the role of aggregate in concrete is changed, being considered a material contained in a cohesive whole through the cement stone. Thus, considering the above mentioned, the present paper demonstrates the reliability of using LiDonit as partial replacement of aggregate from the composition of some concretes. Between the three aggregate sorts (0/4 mm; 4/8 mm and 8/16 mm) used to obtain some concrete types, the LiDonit (a material obtained from the Basic Oxygen Furnace slag) was used as replacements of 25, 50, 75 and 100 wt.% from the 8/16 mm sort and the results demonstrates the possibility to use this material in the above-mentioned purpose. For preparation of a C16/20 class concrete recipe, it was used in the first stage a blast furnace cement (CEM III/A 42,5 N-LN) which has in its composition Portland cement and also an addition of granulated blast furnace slag (36-65%) and in the second stage it was used a CEM II - V 42,5 R cement – a Portland cement with fly-ash which has in its composition Portland clinker (80-94%) and addition of power-plant fly-ash (6-20%). For the next stage of experiments many types of concrete compositions were realized, using as aggregate a 0/4 mm sort (river sand); a 4/8 mm sort (pearl stone) and an 8/16 mm sort composed of LiDonit in varying proportions (100%, 75%, 50%, 25%) and gravel as difference to 100% and also only gravel for the last kind of sort. The obtained samples were tested from the point of view of freeze-thaw resistance, permeability, density, workability and compression strength after 7 and 28 days respectively. Results The obtained results demonstrate a framing within the limits established by the domain specific standards regarding the freezing-thaw resistance, permeability, density and workability for the majority of concrete samples, as well as the compressive strength for 7 and 28 days respectively, as can be seen in the following figures: Conclusions According to data obtained until now, the slag containing aggregates can replace the natural aggregate in the case of road concrete used for concrete coatings. For construction concrete, the replacement of natural aggregate with slag aggregate leads to higher densities of concrete, aspect that recommends the utilization of these type of aggregate for foundations or massive constructions (hydrotechnical constructions), case in which other characteristics, specific for hydrotechnical concrete, must be analyzed. Thus, utilization of slag aggregates is possible, at least for cement concrete coatings. The concrete is a material that is continuously developed due to new additives emerging, which by inserting in the concrete leads to concrete improvement of mechanical and durability characteristics. New additives super- and hyper-plasticizers, for mixtures fluidization etc. will lead to new concrete, with unknown properties, which will need testing and experimenting for characterization purposes.