Manual on Service Life of Corrosion-Damaged Reinforced Concrete Bridge Superstructure Elements (2006)

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37 The procedure for designing a repair and corrosion control system for a bridge superstructure concrete element includes the following steps: 1. Observe symptoms indicating corrosion of reinforcing steel embedded in concrete during the Routine Bridge Inspection. 2. Perform the Preliminary Corrosion Condition Evaluation (PCCE). 3. Use the service life model developed for this project to schedule repair and rehabilitation of the structure. The service life model is used to determine the remaining ser- vice life. 4. Perform the In-Depth Corrosion Condition Evaluation within 2 years prior to construction. This evaluation is used to determine quantity of damage that will need to be repaired and to select a corrosion control system to extend the service life of the superstructure element. 5. Use the service life modeling and Susceptibility Index (SI) to develop a repair and rehabilitation strategy. Data col- lected in the PCCE and the In-Depth Evaluation are used to calculate SI. The quantity of damage and the SI are used to develop a repair and corrosion control strategy. 6. Develop construction documents. A flow chart depicting the decision-making process for the above steps is presented in Figure 4. Overview of Procedures for Designing Repair and Corrosion Control System All bridge structure owners perform regular maintenance and NBIS-prescribed Routine Inspections. During a Routine Inspection, if signs of corrosion are observed, then a decision with regards to performance of the PCCE needs to be taken. If a PCCE has not been previously performed for the struc- ture, one should be performed during the next Routine Inspection. After the completion of the PCCE, the service life model should be used to generate the damage-versus-age plot. The plot is then used to determine the remaining ser- vice life of the concrete element in question. To determine the remaining service life, a criterion must be defined in the form of percentage of surface damage that can be sustained by the concrete element prior to requiring major repair and rehabilitation. Structural and functional aspects of the concrete element will govern the criterion for scheduling the repair of the concrete element. This criterion will vary from one type of element to another. For example, the criterion for a bridge deck most likely will differ from that for a beam or a girder. The time required to reach the criterion from the time of the analysis is termed “remaining service life.” For example, if the criterion for a bridge deck is x% damage, and the service life model results indicate that it will take another 8 years to reach that damage level (from the time of the analysis), then the remaining service life is 8 years. The preferred repair option will depend on the remain- ing service life. For example, if the remaining service life is greater than 20 years, the optimal solution most likely will be to continue with the regular maintenance, whereas if the remaining service life is between 10 years and 20 years, a corrosion control system may be an optimal choice because it provides an inexpensive barrier corrosion con- trol system that controls the ingress of chloride ions and increases the remaining service life. Generally, a major repair would be scheduled if the remaining service life is less than 10 years. Owners should identify the optimal options based on their needs and experience. Once a struc- ture is scheduled for repair, the In-Depth Evaluation is per- formed 2 years prior to construction. This would be followed by modeling of service life, design of a repair and C H A P T E R 6 Procedure for Design of Repair and Corrosion Control System

38 NO NO NO YES NO YES NO YES NO YES YE S NO YES PERFORM PCCE DURING NEXT ROUTINE INSPECTION FIRST ROUTINE INSPECTION TO DETECT CORROSION? PCCE PREVIOUSLY PERFORMED? REMAINING SERVICE LIFE GREATER THAN 20 YEARS? REMAINING SERVICE LIFE BETWEEN 10 AND 20 YEARS? BRIDGE SCHEDULED FOR REPAIR IN NEXT 2 YEARS? SCHEDULE BRIDGE FOR REPAIR PERFORM SERVICE LIFE MODELING PERFORM IN-DEPTH EVALUATION PERFORM SERVICE LIFE MODELING & SI DESIGN REPAIR & CORROSION CONTROL SYSTE M PREPARE CONSTRUCTION DOCUMENT S CONSTRUCTION SELECT CORROSION CONTROL SYSTEM REVIEW SERVICE LIFE MODEL RESULTS FROM PREVIOUS PCCE PERFORM REGULAR MAINTENANCE AND ROUTINE INSPECTION S CORROSION OBSERVED DURING ROUTINE INSPECTION? NO YES Figure 4. Methodology for designing repair and corrosion control system.

corrosion control system, preparation of construction documents, and construction. The methodology should be followed after each Routine Inspection. If signs of corrosion have been detected, then the performance of a PCCE in the past must be verified. If a PCCE has been performed in the past, then the previous service life model results should be used to recalculate the remaining service life. The next step in the methodology should be selected on the basis of the recalculated remaining service life. Preliminary Corrosion Condition Evaluation (PCCE) Recommendations for selection of test methods and tech- niques for PCCE are presented in Table 1. Clear concrete cover, visual and delamination surveys, and chloride profile analysis are essential and must be conducted during the PCCE. If desired, other tests may also be conducted. Minimum sam- pling size for each test method is presented in Table 2. If vari- ations in exposure or other factors that may impact the corrosion process are noted, sampling must be performed in at least one area representing each variation. In-Depth Corrosion Condition Evaluation Recommendations for test methods and techniques for the In-Depth Evaluation are presented in Table 3. In addition to the data collected in a PCCE (clear concrete cover, visual and delamination surveys, and chloride profile analysis), electri- cal continuity testing and petrographic analysis are required. Minimum sampling size requirements are listed in Table 4. If clear concrete cover data are available from a previous PCCE, the data need not be collected again in the In-Depth Evaluation. All other tests must be conducted, and data from a previous PCCE and the In-Depth Evaluation shall be used in the service life modeling. Sampling Size Sampling size of the various test methods is based on the sen- sitivity of the model to the input parameters. Because it is inex- pensive to collect clear concrete cover data, 30 measurements per span are recommended. However, the cost of collecting chloride profile and epoxy-coated rebar cores is much higher, and so fewer samples are recommended. An increase in the 39 Type of Element/ Type of Steel/ Surface Treatment Co v er Vi su al D el am in at io n Ch lo rid e Pr o fil e Ep ox y- Co at ed R eb ar C or es Co nt in u ity Ca rb on at io n Pe tr o gr ap hi c H al f-C el l Co rr o si on R at e Deck Black Steel Bare N/A Concrete Overlay N/A Asphalt Overlay ✓ N/A N/A ✓ N/A N/A N/A Epoxy Overlay ✓ ✓ ✓ N/A N/A ✓ N/A N/A N/A Membranes N/A ✓ N/A N/A N/A Sealers N/A N/A N/A Epoxy-Coated Rebar Bare Concrete Overlay Asphalt Overlay ✓ N/A N/A N/A N/A Epoxy Overlay ✓ ✓ ✓ N/A N/A N/A N/A Membranes N/A N/A N/A Sealers N/A N/A Beams & Girders Black Steel Bare N/A † Paints N/A † Epoxy-Coated Rebar Bare † Paints † † † † † † † † † † † † † † † † † Notes: ✓ - mandatory, × - recommended, † - optional, N/A - not applicable ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ × × × × × × × × × × × × × × × × × × × × × × × × ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ × × × × × × × × × × × × † † † † Table 1. Recommendations for testing during PCCE.

number of samples collected will improve the accuracy of the service life model. Sampling size for electrical continuity testing and petrographic analysis is based on general field practice. Service Life Modeling and Susceptibility Index The clear concrete cover, visual and delamination surveys, and chloride profile data are used to model the service life of the concrete element. The model may need to be run for several chloride threshold values until there is a good agreement between the model-predicted damage and the total damage observed for all condition evaluations conducted on the ele- ment. The chloride threshold value for which the model best predicts actual damage is used to calculate the SI and subse- quently select a corrosion control system. When dealing with large structures, if a variation in exposure conditions is sus- pected across the length of the structure, then the structure should be subdivided into sections, service life modeling should be performed, and the SI should be calculated for each section. Selection of Repair and Corrosion Control System Guidelines are provided to identify (a) all corrosion control alternatives that may be most applicable for a particular distri- bution of chloride ions and (b) the types of corrosion control systems that are most likely to provide optimal protection for a particular SI. Table 5 presents various combinations of repairs and corrosion control systems that can be used in conjunction for a range of SI. The following simplifications were made to identify various types of corrosion mitigation systems: • All surface-applied coatings that are capable of controlling the flow of moisture into the concrete without hampering 40 Test Method Minimum Sampling Size Clear Concrete Cover (CCC) (using nondestructive testing methods). Several actual CCC measurements should be collected to calibrate nondestructive testing equipment. 30 measurements per span. Visual Survey Entire surface of the concrete element. Delamination Survey 10% of the total surface area. If exposure is variable, use several test areas. The test areas should be selected to represent all variations. Chloride Profile Analysis 1 location per 3,000 square feet or a minimum of 5, whichever is higher. Epoxy-Coated Rebar Cores Minimum of 5. Table 2. Minimum sampling size for PCCE. Notes: ✓ - mandatory, × - recommended, † - optional, N/A - not applicable Type of Element/ Type of Steel/ Surface Treatment Co v er Vi su al D el am in at io n Ch lo rid e Pr o fil e Ep ox y- Co at ed R eb ar C or es Co nt in u ity Ca rb on at io n Pe tr o gr ap hi c H al f-C el l Co rr o si on R at e Deck Black Steel Bare Concrete Overlay Asphalt Overlay Epoxy Overlay Membranes Sealers Epoxy-Coated Rebar Bare Concrete Overlay Asphalt Overlay Epoxy Overlay Membranes Sealers Beams & Girders Black Steel Bare Paints Epoxy-Coated Rebar Bare Paints N/A N/A ✓ N/A N/A ✓ N/A N/A N/A ✓ ✓ ✓ N/A N/A ✓ N/A N/A N/A N/A ✓ N/A N/A N/A N/A N/A N/A ✓ N/A N/A N/A N/A ✓ ✓ ✓ N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A † N/A † † † † † † † † † † † † † † † † † † † ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ × × × × × × × × × × × × ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ † † † † ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ Table 3. Recommendations for testing during In-Depth Evaluation.

the outflow of moisture (i.e., they are breathable) have been lumped together as “sealers.” The term sealers is most often used to refer to silane/siloxane-based material that is applied to the surface of the concrete to reduce the inflow of vapor but are not as effective when water is ponded on the surface of the sealer. All materials in this category pro- vide varying degrees of barrier to the transport of chloride ions into the concrete. • The term “membrane” is used to denote surface-applied systems that do not allow transport of moisture in either direction and that are considered waterproofing materials. These systems, as long as their integrity is maintained, do not allow moisture and chloride ions to enter concrete. The asphalt overlay with the waterproofing membrane is included in this category. • The term “overlays” refers to cementitious and nonce- mentitious wearing surfaces installed on the deck sur- face. Asphalt overlays are not included because they do not serve as barriers to moisture and chloride ions. Over- lays are installed to reduce the rate of or stop the ingress of moisture and chloride ions into the original concrete element and to increase the depth to which the chlorides have to diffuse to reach the steel, thereby increasing the time to corrosion initiation. In addition to corrosion benefits, these overlays serve as a wearing surface on bridge decks. • The term “corrosion inhibitors” refers to all materials that have chemicals that can interfere with the corrosion process or parts of the corrosion process, such as the cathodic or the anodic reactions, or that combine with one of the reactants to reduce their availability and conse- quently reduce or stop corrosion. The corrosion inhibitors can be surface applied or admixed with repair concrete. • The term “cathodic protection systems” refers to galvanic and impressed-current systems, and re-alkalization is con- sidered a part of electrochemical chloride extraction. 41 Test Method Minimum Sampling Size Clear Concrete Cover (using nondestructive test methods). Several actual CCC measurements should be collected to calibrate nondestructive test methods equipment. 30 measurements per span. If cover measurements from a previous PCCE are available, they can be used instead of collecting the data again in the in-depth evaluation. Visual Survey Entire surface of the concrete element. Delamination Survey Entire surface of the concrete element. Chloride Profile Analysis 1 location per 1,000 square feet. Electrical Continuity Testing 5 reinforcing steel bars in each span. Must include both transverse and longitudinal bars. Epoxy-Coated Rebar Cores Minimum of 5. Pertrographic Analysis 1 location per 3,000 square feet or a minimum of 5, whichever is higher. Table 4. Minimum sampling size for In-Depth Evaluation. CORROSION INHIBITORS CATHODIC PROTECTION & ELECTROCHEMICAL CHLORIDE EXTRACTION SEALERS MEMBRANES + OVERLAY EPOXY-COATED REBARS SYSTEM PATCH REPAIR DO NOTHING REPLACEMENT OVERLAYS REPLACEMENT PATCH REPAIR CATHODIC PROTECTION OVERLAY SERVES AS A CORROSION CONTROL WHEN REPLACEMENT IS MORE COST-EFFECTIVE NEW CONCRETE ELEMENT (CORROSION CONTROL CAN BE INCORPORATED INTO IT) TOP LAYER CONCRETE SEALERS, MEMBRANES, SI TOO HIGH FOR TOP CONCRETE LAYER OVERLAYS & OVERLAYS PLUS MEMBRANE REPAIR TYPES SI < 2 SI ≥ 2 SI ≥ 4 SI ≥ 5 SI ≥ 7 SI ≥ 8 Table 5. Selection of corrosion control system.

Table 6 summarizes the service life extensions that have been reported in literature for various corrosion control systems. It should be noted that the summary is not exhaustive and many of the categories are broad. There are numerous products in each category, and the service life provided by each product highly depends on the applicability of the product to the struc- ture’s corrosion condition. For example, a corrosion control system applied to a structure exposed to a very mild environ- ment (for that particular corrosion control system) can provide a significantly longer service life than if it had been applied to a structure in a very aggressive environment. Similarly, when a corrosion control system that is inappropriate for the corrosion condition of the structure is used, early failure can occur. Ser- vice life extension by a corrosion control system depends on the corrosion condition of the structure, the exposure conditions, the applicability of that particular system to the condition of the structure, the quality of design and application of the system onto the structure, and the maintenance of the system after its application. Table 6 should be used only as a guideline; further infor- mation on the system of interest should be obtained prior to determining the obtainable service. Planning for Corrosion Condition Evaluation Proper planning for condition evaluation can help reduce the time required in the field and acquire better data. The goal of the condition evaluation must be clearly defined, and the testing planned should be in line with the goals of the survey. Although the same test methods and techniques may be used during various different condition evaluations, the selection of sampling sites, the number of sampling sites, and the level of detail obtained will vary from one condition survey to 42 Corrosion Control System Service Life(years) Patching 4 to 10, 4 to 7 Reinforcing Bar Coating Repair of Epoxy-Coated Rebar > 3 Corrosion Inhibitor Surface Application 4 to 6 Corrosion Inhibitor Plus Patching 4 to 6 LMC Overlay 20 LSDC Overlay 20 HMAM Overlay < 10, 25 Penetrating Sealers 5 to 7 Surface Coatings Corrosion Inhibitor Overlays No information available in literature. Comments No information available in literature. Patching with Portland concrete cement and mortar. Study did not monitor the repair procedure beyond 3 years; therefore, it is difficult to predict its service life. Service life is based on application of the inhibitor in the test patches in highly contaminated concrete. Service life is based on application of the inhibitor in the test patches in highly contaminated concrete. Based on study of several bridges in the state of Virginia. Numerous studies corroborate the findings of this study. The service of 7 years for penetrating sealers is generally accepted. Less than 10 years is based on the failure of the HMA overlay, which would also mean the end of service life of the waterproofing membrane. There are numerous kinds of coatings, and sufficient information is not available to define this category. CP 5 to > 25 ECE 10 to 20 There are numerous kinds of CP systems, and service life varies from one type to another. Service life of ECE-treated concrete element is governed by ingress of chloride ions after the treatment. The service life quoted herein is based on no chlorides migrating into the concrete element. LMC = latex-modified concrete LSDC = low-slump dense concrete HMAM = hot mix asphalt with a preformed membrane CP = cathodic protection ECE = electrochemical extraction Table 6. Extensions in service life for various corrosion control systems.

another. However, certain information on the structure must be collected and reviewed prior to the survey, including the following: • Size and type of structure, • Unusual features in the design, • Structure location and topography, • Environmental exposure (temperature variations, marine environment, etc.), • Reinforcing steel layout, • Type of reinforcement (epoxy coated, bare steel, or galva- nized), • Repair and maintenance history, • Year of construction, • Number of spans, • Presence of protective systems (cathodic protection, over- lay, membranes, etc.), • Average daily traffic (ADT), • Limitations of traffic control (if any), and • Annual application rate and type of deicing chemical (if used). In addition to collecting information about the structure, the following logistical provisions must be ensured: • Power and water must be available for operating equip- ment and conducting certain tests. • Sensitivity of the surrounding environment to debris gen- erated during the survey must be considered. At certain sites, especially in some marine environments, discarding debris may be prohibited in order to protect local biologi- cal species. • There must be access to the concrete elements that have to be evaluated (e.g., specialized equipment may be required for access to girders and beams). • A safety plan needs to be prepared to ensure that all work is performed in a safe manner. • A traffic control plan needs to be prepared, and sequence of testing needs to conform to the traffic control plan. Restrictions need to be taken into account when planning the testing schedule (e.g., in some urban areas, traffic con- trol is only allowed during certain hours of the day). • An emergency plan must be in place to deal with any acci- dents that may occur. Based on the type of survey, it may be necessary to docu- ment the location of the sampling site using a grid. If a grid is required, planning for the orientation of the X-Y grid must be prepared prior to going on-site. Either the grid can be marked on the surface of the concrete element or some form of grid markers can be placed on the surface, such as a meas- uring tape or a rope or string marked at equal intervals. Most often during a condition evaluation, concrete exca- vation or collection of cores is required. The excavated areas must be patched with an appropriate and approved material. It is necessary to ensure that the patch is installed using proper construction practices so as not to increase the sus- ceptibility of the concrete element to corrosion. If epoxy- coated rebars are involved, any damage inflicted on rebars exposed during the condition survey will need to be repaired (e.g., by using an epoxy material to patch the excavation, thus avoiding any exposure of the damaged sections of the epoxy- coated rebars to the environment). Proper marking and handling of the samples is very impor- tant, and a proper marking and handling plan needs to be developed. Using more than one marking scheme on each sample will make it easier to identify the samples when some parts or one of the markings is erased or becomes unreadable. All equipment must be tested prior to use, and, when pos- sible, backup should be provided. Some pieces of electronic equipment most commonly used in condition evaluation can be affected by exposure to certain environments. In marine environments, certain electronic equipment will fail after several days of use because of exposure to chloride ions in the air. For greater productivity, an optimal crew size should be selected for each condition, evaluation, and scope of work. If a sequence of all sampling and testing work is prepared, the optimal crew size becomes obvious. Only certain tests and sampling can be conducted simultaneously. Often it is bene- ficial to conduct the visual and the delamination survey first because much of the testing and sampling work is not per- formed in the delaminated areas. This survey is often followed by locating reinforcing steel for coring, chloride sampling, electrical continuity testing, and cover measurement. Half- cell potential measurements, corrosion rate measurement, and core collection can occur simultaneously at different parts of the concrete element if equipment used in one test is not interfering with equipment used in another test. 43