CFRP-to-concrete bond behavior under aggressive exposure of sewer chamber

The growing industrialization over the past century has led to increased exposure of structures to such aggressive conditions as found in sewer networks. The rehabilitation and maintenance of sewer systems call for innovative wastewater collection systems based on their design life cycle and operational conditions. Acid exposure is one such condition whose impacts on sewer systems strengthened with FRP sheets still await adequate research. The present paper reports the results of a study conducted in an aggressive concrete sewer chamber in an industrial zone, chosen as an outdoor test design to investigate the effects of an acid environment on the bond strength of FRP sheets bonded on the concrete surface via either of the two techniques of externally bonded reinforcement (EBR) or externally bonded reinforcement on grooves (EBROG). The results show that the bond strength of the EBR specimens depends on both exposure type and duration while the aggressive environment has no significant effects on the bond strength of EBROG specimens. Generally, maximum bond strength in EBR specimens decreases by up to about 19.7% with increasing exposure duration to 6000 h. In the case of EBROG specimens, however, maximum bond strength initially increases by 8.9% after 3000 h of exposure before it declines by 3.6% after 6000 h.