Large amount of slag is obtained during the production of ferrochromium. This by-product has properties comparable to natural aggregates. However, almost all of the ferrochromium slag is landfilled. The main objective of this study was to investigate the effects of ferrochromium slag aggregate on the mechanical properties and permeability of concrete. For this purpose, waste ferrochromium slag was used as aggregates in normal concretes and alkali-activated mixtures, with five different water/binder ratios. Concretes with limestone and Portland cement were produced as references. Mechanical properties of the concretes were determined. Chloride permeability and resistivity tests were performed. The results indicate that the strengths of the mixtures were similar to each other for given water/binder ratios. Rapid chloride permeabilities of the mixtures were close to each other, except for high water/binder ratios. Electrical resistivities of the mixtures were recorded. A strong relationship between electrical resistivity and chloride permeability was obtained. The results confirmed that the ferrochromium slag aggregates may be successfully used in concretes ranging from low-strength to higher strength classes.