Condition assessment, reinforced concrete

Interpretation of the results. The interpretation has to be done by corrosion specialists with experience in reinforced concrete structures in the context of other information from condition assessment. The results can be used to pinpoint sites with high corrosion activity (in addition to halfcell potential measurements), to predict future deterioration of the structure or to assess residual service life. Daily and seasonal variations in the corrosion current due to changes in temperature and relative humidity will induce variations in values by more than a factor 2. To predict future deterioration several measurements in time are usually needed. When only one single value is available, it is recommended to assume a variation in J on ... 

The term conventional repair is used in this book to indicate a repair work made on a damaged reinforced concrete structure, which is aimed at restoring protection to the reinforcement by means of replacement of non-protective concrete with a suitable cementitious material. The durability of the repair work is due to the achievement and maintenance of passivity on the reinforcement by the contact with the protective repair material. The repair work can be divided in the following steps a) assessment of the condition of the structure b) removal of concrete in well-defined parts of the structure and for specific depths c) cleaning of the exposed rebars d) application of a suitable repair material to provide an adequate cover to the reinforcement [1-6]. Each of these steps must be carried out properly in order to guarantee the effectiveness of the whole repair work. Additional protection measures can be used to increase the durability of the repair, but they must not interfere with the protection provided by the alkahnity of the repair material. Strengthening may also be required to restore the structural safety of the structure. 

Proposed procedures are applied in the assessment of an existing reinforced concrete road bridge. Partial factors are estimated on the basis of new information about the bridge conditions and requirements for a remaining working life. 

Swiat and Bushman (1993) describe the CP criteria of reinforced concrete structures in atmospheric conditions. The authors critically assess criteria used in the U.S.A. and Canada during the CP of bridges. Broomfield (1997) describes theoretical and prac-... 

Broomfield, J. R, Rodriguez, J., Ortega, L. M. and Garcia, A. M. (1993) Corrosion Rate Measurements in Reinforced Concrete Structures by a Linear Polarization Device, Int. Symp. on Condition Assessement, Protection Repair and Rehabilitation of Concrete Bridges Exposed to Aggressive Environments, Minneapolis ACI Fall Convention. 

Specific codes, guides, and standards related to the assessment of reinforced concrete structures are generally not as well developed as in, say, the mechanical engineering and metallic materials domains. However, the essential purpose of a detailed condition survey provides useful terms of reference. This is usually threefold First, the extent of deterioration has to be determined second, the mechanisms and causes of deterioration should be established and finally, a corrosion control and/or repair strategy has to be specified. 

Conditional Spectra, Fig. 4 Risk-based assessments of (a) peak story drift ratio and (b) peak floor acceleration of a 20-story reinforced concrete frame stmcture obtained... 

In case a, future penetration of chlorides has to be evaluated in order to assess if the chloride threshold will be reached at the surface of the reinforcement before time tf. If this is expected, the concrete with a chloride content higher than the critical value has to be removed (and replaced with a chloride-free material that prevents further penetration of chloride). Equation (1), Chapter 6, may be used to evaluate the future penetration of chlorides. By fitting the present chloride profile, the surface content and the apparent diffusion coefficient Dj j, may be calculated at time Since these parameters are evaluated on the actual structure and usually after a long time of service, it is often reasonable to assume that they will not change significantly in the future (unless the conditions of exposure of the structure will change). Equation (1), Chapter 6, can then be used to plot the expected chloride profile at time tf. 

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