Corrosion Detection for Health Monitoring of RC Structures
Loreto, Giovanni (2010) Corrosion Detection for Health Monitoring of RC Structures. [Tesi di dottorato] (Inedito)
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Reinforced concrete is one of the most durable, versatile, and widely used construction materials. It can be used to make small posts, vast bridges, and tall buildings as well as lining tunnels and constructing pipeline. Generally, this composite material is capable of withstanding a wide range of environments, from oil rigs in the North Sea to deserts. However, occasionally it does not give the low maintenance life expected of it. Sometimes this is due to more adverse condition than initially expected. Consequently, there are many structures in the built environment suffering from corrosion induced damage. During the last few years, infrastructure deterioration caused by corrosion has escalated, warranting serious consideration. Among the different distressing consequences of reinforcing-bar corrosion, the most common is concrete cover cracking. When a reinforcing steel bar corrodes in concrete, a surface layer of steel is consumed and a layer of corrosion products rust forms on the perimeter of the bar. The rust that forms occupies a larger volume than the consumed steel layer, the increased volume creates internal high pressure against the surrounding concrete, and cracking and spalling result. Thus, steel corrosion may cause damage in steel, concrete, and the bond between them. Investigations have been conducted during the last three decades regarding chloride penetration and prediction of corrosion initiation. However, few investigations have dealt with corrosion propagation and/or residual life predictions, which are also needed for durability forecasting. Therefore, the aim of this investigation is to discuss, based on experimental information from previous investigations, the possibility of linking the degree of degradation (from a load-capacity reduction point of view) to the surface distress (for example, crack width opening) of a corroding reinforced concrete element in a marine environment. This dissertation presents a laboratory study, applied to three different type of concrete, in order to analyze and monitor the material behavior under accelerated ageing. The purpose of an accelerated test is to cause, degradation, corrosion or failure in a shorter time period than under normal conditions without change in failure mechanism. The studyoutline is based on different reference, but basically it was carried out performing accelerated corrosion test and using knowledge related to mechanical, chemical and electrochemical engineering. The analysis provided information concerning durability and service life of material. This information were applied to investigate on the possibility of on-field analysis and the correlation among traditional techniques of monitoring, service life modeling and increasing of acoustic emission technology for health monitoring.
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