International Concrete Abstracts Portal

This CD-ROM contains twelve papers that were presented at sessions sponsored by ACI Committee 345 at the ACI Spring 2010 Convention in Chicago, IL. The papers contain information relating to the current technology for concrete bridge repair and maintenance. The papers discussed case studies of damage and corresponding repair, state-of-the-art repair technologies, evaluation and inspection techniques, and maintenance of existing concrete bridges. Note: The individual papers are also available. Please click on the following link to view the papers available, or call 248.848.3800 to order. SP-277

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.

This paper presents on-site inspection techniques to examine a damaged prestressed concrete girder bridge. The bridge is 18.3 m [60 ft.] and consists of double-tee beams (DT3000 x 700 ) with a 50 mm [2 in.] topping concrete. To simulate the effect of deterioration for the girder, the leg member is intentionally damaged by cutting 2 prestressing strands. A load test is conducted to evaluate the flexural behavior of the bridge before and after the damage. A site inspection is conducted after 10 months of the load test. The inspection techniques used for this study includes the visual inspection, pull-off test, ultrasonic test, rebound hammer test, core test, and surveying. The bridge exhibits significant cracks and spalling of the concrete in the deck and the legs. Corrosion of the reinforcing steels is observed. The pull-off test shows that the bond strength between the flange of the girder and the topping concrete is adequate. The ultrasonic test exhibits some internal defects of the leg member, including an increased transmission time of the ultrasound. The in-situ concrete strength measured is reasonably close to the specified 28 day concrete strength, based on the rebound hammer test and the core test, with an average error of 2.1%. Permanent downward deflections are not observed, whereas a maximum camber of approximately 35 mm [1.4 in.] is measured by surveying. The inspection techniques reported in this study are reliable and recommended to examine concrete bridge elements.

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.

Recently, the non-corrodible fibre reinforced polymer (FRP) reinforcing bars, especially glass FRP bars, have been increasingly used in concrete bridge deck slabs. Although corrosion of steel reinforcement in a major cause of a bridge deterioration, almost every bridge component requires some kind of repair/rehabilitation due to various kinds of damage or changed circumstances such as freeze-thaw and wet-dry damage, accidental (vehicle) damage, excessive cracking, poor design details, poor quality construction, inadequate maintenance, changes in level of service, etc. Therefore, there have been concerns regarding the feasibility and economics of repairing concrete elements reinforced with FRP materials. This paper presents an experimental study on the rehabilitation of concrete bridge deck slabs reinforced with GFRP internal reinforcement. The main objectives of this study are to (1) determine the most suitable concrete demolition method causing minimal or no damage to GFRP bars used as main reinforcement in concrete slabs; (2) evaluate the most effective repair technique by verifying the flexural strength and load-transfer efficiency of concrete slabs after repair. To fulfil these objectives, 16 full-scale concrete slabs (1500×2250×200 mm) totally reinforced with GFRP bars were constructed and tested in the laboratory. The test parameters include concrete demolition technique, type of GFRP bars, concrete compressive strength, number of reinforcement layers, thickness of concrete cover, and repair technique. It is concluded that GFRP-reinforced deck slabs can be easily and effectively repaired.