Mechanically fastened composites for retrofitting corrosion-damaged reinforced-concrete beams: Experimental investigation

This paper presents results of an experimental study aimed at investigating the effectiveness of different mechanically fastened composite systems for retrofitting relatively large-scale corrosion-damaged reinforced concrete beams. A total of 15 beams, 250×275×3,000 mm each, were constructed and tested. The beams were initially subjected to accelerated corrosion for 60 days that corresponded to an 8% tensile steel mass loss. The beams were then retrofitted with composite plates secured with powder-actuated fasteners (PAF), expansion anchor bolts (EAB), and threaded anchor bolts (TAB). Following the initial corrosion and retrofitting, four retrofitted beams were tested to failure, and four beams were exposed to an additional 40 days of accelerated corrosion until they reached a 15% tensile steel mass loss, then tested to failure. Five beams were not corroded to act as control specimens. Two corroded beams were tested to failure without retrofitting. The undamaged strengthened beams exhibited flexural strength gains in the range of 67-85% with no reduction in the ductility index, except for the beam with the 32-mm-long PAF. Corrosion-related cracks compromised anchorage of the PAF into the concrete; and hence, a significant reduction in the strength gain and ductility index was recorded for the beams with the PAF fastening system. The corroded beams retrofitted with the EAB and TAB fastening systems exhibited insignificant or no reduction in the strength gain and ductility index even at the higher corrosion damage state of 15% tensile steel mass loss. Despite corrosion damage and cracking, the flexural capacity of all retrofitted beams was higher than that of the control beam.