The aim of this study was to determine the impact air cooled blast furnace slag has as replacement for aggregate in concrete production. By sifting of material samples to ensure grain size distribution, literature studies and interviews data were collected cab stone. Evaluation and analysis of data from screening, strength tests, as well as measurements carried out by Martin Åström.The ASR analysis was conducted by Envix Nord AB Umeå. The results from the ASR test resulted in the following conclusions:•Short-term and long-term tests with air cooled blast furnace slag in the concrete show that there is no negative expansion caused by the ASR reaction.•From the analysis (ASTM 1260) it becomes clear that investigated the nature of aggregates is more expansive than the air cooled blast furnace slag.•Durability is approved under the requirements of C25/30.•Pozzolan (silica) increases the strength of the specimens. Whether it is economically viable to set up pozzolan is uncertain.•Use of the air cooled blast furnace slag as substitutes for natural materials may prove to be cost effective.