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A platform for research: civil engineering, architecture and urbanism
Lessons Learned from a Successful Shotcrete Repair
This paper presents the background and lessons learned from a 23-year old shotcrete repair of two corrosion-damaged concrete bridges. The two CPR Railroad Overpasses (northbound and southbound structures) at Cayley were exposed to highway de-icing salts and had developed severe curb corrosion and spalling in 1981 at age 21 years. The curbs were extensively repaired in the summer of 1982 with site-batched latex-modified dry-mix shotcrete. The work consisted of chipping to remove 220.6 lineal metres (91.3% of total length) of corrosion damaged curb face to an average depth of 150 mm. The scope of work left behind a significant amount of adjacent chloride contaminated non-repaired curb concrete. The repairs are in good condition and remain in service in 2005. No spalling of the non-repaired curb concrete, as might be expected due to the ring anode effect after leaving adjacent concrete un-repaired, has occurred. The repairs have been monitored for corrosion with inspection and copper sulfate electrode (CSE, ASTM C-876) testing on a five year cycle since 1983. The CSE results show that the post-repair readings on both structures declined progressively following repair in 1982 until approximately 1995, when they reached their minimum values and began to increase. The most recent tests in 2004 showed a northbound bridge curb average of –297 mV, which is 78 mV lower than when repaired in 1982. The average 2004 reading on the southbound bridge curbs was –290 mV, still 65 mV lower than in 1982. The repaired curbs are in sound structural condition with no visible damage or debonding, few cracks and little staining after 23 years of service. The test data suggests that the repairs will provide significant additional service life, and a total service life of 35 years is expected. The repair details included the use of galvanized welded wire mesh, manual chipping for concrete removal, followed by sandblasting, shotcreting into forms along the longitudinal edges for trueness. The repair perimeter was not saw cut. The paper presents current condition data and discusses how various repair features contributed to it.
Lessons Learned from a Successful Shotcrete Repair
This paper presents the background and lessons learned from a 23-year old shotcrete repair of two corrosion-damaged concrete bridges. The two CPR Railroad Overpasses (northbound and southbound structures) at Cayley were exposed to highway de-icing salts and had developed severe curb corrosion and spalling in 1981 at age 21 years. The curbs were extensively repaired in the summer of 1982 with site-batched latex-modified dry-mix shotcrete. The work consisted of chipping to remove 220.6 lineal metres (91.3% of total length) of corrosion damaged curb face to an average depth of 150 mm. The scope of work left behind a significant amount of adjacent chloride contaminated non-repaired curb concrete. The repairs are in good condition and remain in service in 2005. No spalling of the non-repaired curb concrete, as might be expected due to the ring anode effect after leaving adjacent concrete un-repaired, has occurred. The repairs have been monitored for corrosion with inspection and copper sulfate electrode (CSE, ASTM C-876) testing on a five year cycle since 1983. The CSE results show that the post-repair readings on both structures declined progressively following repair in 1982 until approximately 1995, when they reached their minimum values and began to increase. The most recent tests in 2004 showed a northbound bridge curb average of –297 mV, which is 78 mV lower than when repaired in 1982. The average 2004 reading on the southbound bridge curbs was –290 mV, still 65 mV lower than in 1982. The repaired curbs are in sound structural condition with no visible damage or debonding, few cracks and little staining after 23 years of service. The test data suggests that the repairs will provide significant additional service life, and a total service life of 35 years is expected. The repair details included the use of galvanized welded wire mesh, manual chipping for concrete removal, followed by sandblasting, shotcreting into forms along the longitudinal edges for trueness. The repair perimeter was not saw cut. The paper presents current condition data and discusses how various repair features contributed to it.
Lessons Learned from a Successful Shotcrete Repair
Carter, Paul D. (author) / Wong, Jim (author)
10th International Conference on Shotcrete for Underground Support ; 2006 ; Whistler, British Columbia, Canada
Shotcrete for Underground Support X ; 348-360
2006-08-25
Conference paper
Electronic Resource
English
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