Models for estimation of saturation degree of concrete through the environmental variables applied to the reliability analysis of reinforced concrete structures attacked by chloride ions

摘要

The problematic of the durability of reinforced concrete structures inserted in environments of severe aggressiveness is presented as one of the main difficulties faced by the civil construction chain. Of the various agents capable of degrading these structures, special attention is paid to chloride ions capable of causing corrosion of reinforcing steel, these ions are widely present in marine environments. In this sense, the estimated useful service life of reinforced concrete structures becomes a fundamental theme in the evaluation of the durability of concrete structures. Although several processes cause penetration of chlorides in the concrete, it is practically agreed that the diffusion mechanism is the predominant one, being Fick's 2nd Law of diffusion a classic model for the characterization of chloride penetration into concrete. The ionic diffusion process is strongly influenced by the saturation degree (GS) of the pores in the concrete, it influences directly on the chloride diffusion coefficient (D). Although GS measurement methodologies have been developed, they are costly in time and resources. The objective of this study is to present estimates of GS, based on the environmental exposure conditions of the structure, and to analyze the influence of this parameter on the estimated useful service life of structural elements of reinforced concrete from the point of view of reliability. Meteorological and GS measurement data from two coastal regions are used, one in Rio Grande, in southern Brazil and the other in Santa Pola, southeast of Spain. Concrete GS estimation models were obtained for each studied situation and also for both environments together. It was verified, through a probabilistic approach, the strong influence of the use of these models in the estimation of useful service life of reinforced concrete structures.