Summary In this paper, a stress-strain state is analysed for hardening reinforced concrete due shrinkage, increase of physical parameters and non-linear strains of concrete. A method has been developed for assessment of initial stress-strain for reinforced concrete specimens subjected to short-term loading. Stresses and strains in reinforcement and concrete are estimated by experimental-theoretical method and σ—e diagram for tensile concrete including the descending branch is defined. Experimental investigations of tensile reinforced and non-reinforced members have been carried out for defining the descending part of σ—e diagram. Sufficient agreement of experimental and predicted data have been achieved. The method and results of these investigations have been applied for design and building of water cleaning equipment made from cast-in-situ and pre-cast concrete. Stress-strain state of structures has been determined for different stages of construction and each of them the required technology has been ch...