The given paper presents the results of the research on concrete constructions reinforcing by polymer composite reinforcement (FRP) instead of the steel one functioning on the elastic basis such as road slabs, slabs for chain drives and for pumping machines used at the oil fields. The experimental samples of reinforced FRP products, which are similar to reinforced concrete products due to their geometric parameters, have been manufactured and tested. The comparative assessment of the samples products conformity required in accordance to bearing strength and crack resistance has been also conducted. Based on the obtained results, the recommendations for usage of FRP in prefabricated concrete products have been developed. It was concluded that the usage of FRP for reinforcing process of concrete constructions is reasonable except for the use of several types of overloaded constructions where a significant reduction of an existing gap between the bars and saving the tensile reinforcing area is necessary.