The study of the deformability of building structures, especially bending elements, is an integral part ofa full study of structures, because it is often the deformability determines the size of the cross section ofthe element, to ensure the necessary rigidity of building structures. For beam elements, the mostimportant during exploitation are vertical displacement – deflections.For application (especially under the influence of aggressive environment) as a material of productionof the building structures we offer rubber concrete-polymer concrete which has favorable deformationand strength characteristics, high adhesion to metal surfaces. It is important to note that the compositionof fibrorubcon used industrial waste such as fly ash and fibers steel cord. It was establishedexperimentally that the strength of fibrorubcon corresponds to the class of high-strength concrete, butthe modulus of elasticity of rubcon corresponds to the modulus of elasticity of traditional concrete. Tostudy the deformability of rubcon and fibrorubcon bending elements we have made a beam with alongitudinal reinforcement percentage μ = 0...8.4%.The beams were tested for pure bending – the most characteristic type of loading for such elements. Onthe basis of the tests, a limit on the percentage of longitudinal reinforcement to satisfaction therequirements of the current standards for maximum deflections of fibrorubcon and rubcon beams wasset.