Évaluation de la probabilité de corrosion des armatures dans les dalles de béton armé par radar
The majority of reinforced concrete structures built with the standards of the sixties will have a life span of 70 years. Over the past decade, these structures have shown signs of fatigue. In Québec, there are 4924 bridges under the Ministère des transports du Québec responsibility, which approximately 80% are over 30 years old. Among these bridges, 2 301 need repair in the next five years.The destructive evaluation methods used for assessing conventional structure destructive and providing timely information at randomly selected points are obsolete. This information may not be representative of the true state of the structure.The Ministère des transports du Québec adopted a Half-Cell potential standardized and effective technique in the evaluation of the state of corrosion of reinforcement. But this method represents some drawbacks. It is destructive, expensive, and causes enormous traffic problems in the area of large cities. This method often mobilizes, for one day, a dozen persons per structure. It involves drilling holes in the case of a concrete slab with a layer of coating and release of the frame to ensure the electrical continuity and connecting equipment measures. With growing number of deficient structures, the Ministère des transports du Québec went to look for an evaluation procedure which could be faster, low cost and on a large scale, to limit the damage to these structures, thus, his involvement in the NSERC Industrial Research Chair at the Université de Sherbrooke. Among the non destructive testing methods that can be used directly or indirectly for the assessment of the state of corrosion in concrete reinforcement, the radar, by its rapid implementation on a large scale and low cost, can be a good alternative if compared to the Half-Cell potential radar who requires the mobilization, for one hour of two, persons without any harm to the integrity of the structure. However, the radar technique had to be validated in the laboratory and on the field with other methods such as the Half-Cell potential and electrical resistivity.The latter is a reference to acquire unanimously professionals, and the electrical resistivity as a bridge crossing between the radar and Half-Cell. These are methods that can be influenced by common factors. Therefore, the objective of this research is to develop and validate a radar method for testing bridge decks. This method must yield results similar to those of the Half-cell potential and not cause the closure of bridges. To help gain a better understanding of the effect of different parameters on the radar measurements, the Half-cell potential and electrical resistivity, laboratory work has been carried out on different slabs of reinforced concrete. This work has enabled the study of the effect of the concrete, chloride ions, moisture, the membrane on the radar reflection on the concrete. Finally, it develops and validates an approach radar data-processing alternative.The tests are evaluated by radar reflections on the upper and bottom of the concrete slab.The first case is valid if the minimum thickness of the asphalt layer is 7 cm.The evaluation of the minimum thickness of the asphalt layer and the effect of the membrane were examined in the context of this work.The results have helped to develop a methodology for testing slabs of bridge decks. In its simplicity of implementation, reliability measures, the cost and the nondestructive character, the radar is a diagnostic tool for large scale.
- Génie – Thèses