【正文】 According to the present day standards, . [1], for involving reinforcing steel in concrete structures, certain minimum values for the mechanical properties modulus of elasticity (E), yield stress (Rp), ultimate stress (Rm) and elongation to failure (fu) of the steel are required. Furthermore, the standard sets Rm/Rp [1]. With increasing service life of a reinforced concrete structure damage accumulates gradually. Nowadays, significant resources are allocated worldwide for the repair and rehabilitation of deteriorating concrete structures. Recent reports indicate that the annual repair costs for the reinforced concrete structures of the work of highways in the USA alone amounts to 20 billion USD [2]. The respective repair costs for reinforced concrete bridges in England and Wales amount to 615 million GBP [3]. Yet, although in recent years the problem of the actual residual strength degradation of ageing reinforced concrete structures has attracted considerable attention, it is far from being fully understood and, even less, resolved. It is worth noting that up to now, little work has been done to account for the effects of corrosion on the mechanical properties of the reinforcing steel bars and hence on the degradation of the load bearing ability of a reinforced concrete element [4]. Such effects are the reduction of the effective crosssection of the reinforcing steel, micro and macro cracking of concrete and finally the spalling of the concrete. The underestimation of the corrosion problem arises from the fact that under normal circumstances, concrete provides protection to the reinforcing steel. Physical protection of the reinforcing steel against corrosion is provided by the dense and relatively impermeable structure of concrete. The thin oxide layer covering the reinforcement, during concrete hydration, ensures chemical protection. The oxide layer remains stable in the alkaline concrete environment (pH 13), but begins to deteriorate when the pH of the pore solution drops below 11 [5] and [6]. The rate of deterioration due to corrosion rises when the pH drops below 9. For corrosion to mence, the oxide film must be broken or depassivated. Depassivation may occur if the alkalinity of the pore solution in the concrete pores decreases and/or peration of the chloride ions takes place. This may be caused by carbonation, especially in the proximity of cracks, or by water dilution which acpanies cracking [7], [8] and [9]. The advancing corrosion results in a reduction of the load carrying crosssection of the bars and an increase in their volume, which may cause cracking of concrete as well as an appreciable decrease on the bond strength between the reinforcing bars and concrete [10] and [11]. The above considerations do not account for the effect of corrosion on the mechanical behavior of the reinforcing steels. Most of the available studies on the corrosion of reinforcing steels refer to the metallurgical aspects of corrosion such as the mass loss, the depth and the density of pitting etc., . [12] and [13]. It is worth noting that the corroded steel bars are located in a zone of high tensile or shear stresses [5], [12], [14], [15], [16] and [17]. Maslechuddin et al. [10] evaluated the effect of atmospheric corrosion on the mechanical properties of steel bars. They concluded than for a period of 16 months of exposure to atmospheric corrosion, rusting had an insignificant effect on the yield and ultimate tensile strength of the steel bars. Almusallam [18] evaluated the effect of the degree of corrosion of the steel bars in concrete, expressed as percent mass loss, on their mechanical properties. The results of the study indicated a close relationship between the failure characteristics of steel bars and slabs with corroded reinforcement. A sudden failure of slabs in flexure was observed when the degree of reinforcement corrosion expressed as percent mass loss exceeded 13%. The above results on the mechanical behavior of corroded reinforcing steels refer to BSt 420s of DIN 488, (S420s according to the Hellenic standards). The above results clearly indicate the need to account for the effects of corrosion on the mechanical properties of the reinforcing steel BSt 500s (S500s according to the Hellenic standards) which at present is almost exclusively used in reinforced concrete structures. It is worth noting that corrosion damage of the reinforcement, is expected to bee more noticeable in new constructions using reinforcing steel S500s, given the fact that this type of steel exhibits greater mass loss due to corrosion pared to steel classes S400 and S220 [19]. Recall that many reinforced concrete structures are located in coastal areas with an intense corrosive environment. On the other hand, a wide spread use of corrosionresistant steel reinforcing bars should not be expected as these bars cost about six to nine times more than plain carbon steel reinforcing bars. In the present study, the effects of corrosion on the tensile behavior of reinforcing steel bars Class S500s tempcore are investigated. The specimens were precorroded using laboratory salt spray tests for different exposure times. The dependencies of the degradation of the tensile properties on the corrosion exposure time have been derived. The tensile properties of the corroded material were pared against the requirements set in the standard for involving steels in reinforced concrete structures. 2. Experimental research The experiments were conducted for the steel S500s tempcore, which is similar to the BSt500S steel of DIN 488 part 1 [20]. A stress–strain graph of the uncorroded material is shown in Fig. 1. The chemical position (maximum allowable % in final product) of the alloy S500s is: C, %。C + – 176。 1999. [7] Roberto Capozucca, Damage to reinforcement concrete due to reinforcement corros