Carbontacion resistance of concrete bridges with 50 years of life in service in rural environment

Corrosion it’s the most frequent and critical pathology in reinforced concrete structures, the reinforced steel bars lost the locally passive protection; ion chloride or widespread carbonation. The carbonation is the main process of reducing the service life of concrete in urban, rual or mixed atmospheres, free from other aggressive agents. The carbonation resistance is direct function of the characteristics of the emplacement (concentration of CO2, HR, etc.) and the pore grid of concrete (water ratio / cement material, content and type of cement, curing, etc.). In this work the carbonation resistance (RCA) is evaluated and estimated the time of depassivation of the reinforced steel of concrete highway bridges executed with a service life > 50 years, emplaced in a rural environment class A1 (CIRSOC 201) executed with Normal Portland Cement (CPN). The influence of the quality of concrete is analyzed macro and microclimate. The results show a downward trend RCA by model Duracrete and the cement contain rules the carbonation resistance by granting the alkaline reserve under the same microclimatic conditions in most of the structures.