This paper presents a case study in the evaluation and repair of precast prestressed concrete beams with moderate to severe deterioration due to Alkali-Silica Reaction (ASR). The subject of this study is a 25-year old, 15-span bridge in Texas experiencing deterioration characterized by longitudinal cracking along the bottom flange at the beam ends, vertical splitting in the beam web at the bearings, and general map cracking with discoloration on the beam surfaces. Evaluation methods discussed include crack and surface discoloration mapping and as well as procedures for excising samples for petrography and accelerated expansion testing to confirm the presence of ASR. A structural evaluation of the existing beams is also presented to study the potential capacity loss resulting from concrete deterioration. Detailed visual observations of distressed conditions, structural analysis of damage scenarios, and laboratory test results were considered to develop a repair course of action that included the application of crack fillers, concrete penetrating sealers, and coatings as well as the application of CFRP composites to confine the expansion in the concrete beams.

During the last decade, the Swedish Road Administration (SRA) has transferred resources from corrective to preventive bridge maintenance. Presently, 10 to 15 percent of the budget is devoted to preventive maintenance whereas corrective maintenance, repair, and reconstruction comprise the remaining 85 to 90 percent. This reallocation has resulted in considerable efficiency gains but further savings are likely to be large. Preventive maintenance aims at measures to maintain the function of the bridge structure. Frequent measures include water washing, cleaning, vegetation removal, crack repair, material refill, and stretching of bridge railings. SRA has defined a series of technical requirements to harmonize the preventive bridge maintenance. Several technical requirements state that a structural element or element part “should be 95 percent clean”. SRA has also developed methods to verify that the technical requirements are fulfilled. However, the scientific basis for the relationship between the technical requirements and the function of the bridge structure is unknown or weak. The verification methods are not always unquestionable. The paper contains a critical review of the technical demands for preventive bridge maintenance in Sweden. Do they adequately promote durability and long-lasting service life? Are the prescribed requirement levels appropriate? Could the technical requirements be replaced by other and better requirements? How do they look like in an international comparison? There is a general belief that performance-specified contracts would be more cost-effective than other contract types. Do the Swedish demands facilitate or obstruct performance-specified contracts for bridge maintenance? The questions are discussed in the paper that also contains a summary of a Swedish pilot study conducted at the Swedish Cement and Concrete Research Institute.

This paper presents a unique approach to examine the performance of constructed concrete bridges in cold regions, based on a combined statistical analysis and geographic information system (GIS) method. A total of 3,013 bridges and 1,126 bridge decks selected from the State of North Dakota (one of the coldest regions in the United States) are analyzed. Detailed technical information of the examined bridges is obtained from the National Bridge Inventory (NBI) database constructed between 2006 and 2007. A statistical analysis is conducted to identify the critical sources of bridge deterioration in cold regions, in particular concrete bridges, using the ordinary least-square multiple regression method. The performance of concrete bridges under cold weather is in general satisfactory, while the deck slabs are the critical structural members and may require regular maintenance and repair. The contribution of the year-built and the presence of water are the most critical factors to the bridge deterioration. A case study is presented based on a 29-span bridge consisting of cast-in-place deck slabs supported by prestressed concrete and steel plate girders. Detailed inspection results are reported and adequate maintenance methods are discussed.

This paper presents a field application on the use of Fiber Reinforced Polymers (FRP) to repair a corrosion-damaged reinforced concrete (RC) girder. Concrete surface rehabilitation and Carbon FRP (CFRP) repair was undertaken on a 9.75 m (32 ft) long section of the 22.86 m (75 ft) long girder at the south span of the Scheifele Bridge, in the Regional Municipality of Waterloo, Ontario. Four different repair schemes were utilized along the length of the girder. The different steps of the rehabilitation work are described including surface preparation, application of the CFRP sheets, and installation of sensors as part of the structural health monitoring system. The sensors comprised of electrical strain gauges, corrosion probes and fiber optic sensors placed at critical locations along the bridge girder. Visual inspection and analysis of the data gathered over the last four years showed that the FRP repair system was able to halt the existing corrosion activity and protect the structural integrity, thus prolonging the bridge service life.

Non-destructive evaluation techniques were used to assess the condition of a 40-year old concrete bridge operating in an aggressive marine environment. The bridge’s superstructure includes both reinforced and prestressed concrete one-way slabs, and experienced widening, repairs, and recently strengthening by means of externally bonded carbon fiber reinforced polymer (CFRP) laminates. Phase I of the investigation focused on evaluating deterioration of concrete and steel reinforcement by means of in-situ and laboratory testing. A 24 in. by 24 in. [610 by 610 mm] grid was marked on the bottom surface of the supporting slabs to map indicators of physical damage. Measurement of carbonation, pH, chloride content, corrosion potential, and visual inspection were implemented and rendered as layered maps to identify damaged areas. Phase II includes acoustic emission (AE) monitoring under service loads. AE amplitude, duration, energy and hits were analyzed to identify structural activity associated with damage phenomena, such as concrete cracking, slip between corroded reinforcement and surrounding concrete, and debonding of CFRP laminates. The database acquired from Phase I and Phase II was used for damage assessment. Combined results from the different techniques show promise in determining areas of concern with reduced uncertainty than when using a single measurement technique.