EFFECTS OF ENVIRONMENTAL EXPOSURE ON THE PERFORMANCE OF CAST-IN-PLACEAND RETROFIT ANCHORS IN CONCRETE

In this study single cast-in-place anchors and retrofit anchors (expan sion, undercut and adhesive) were exposed to five simulated environmen tal exposure conditions: I) ultraviolet light; 2)freezing and thawing; 3) corrosion in a pH-neutral salt solution; 4) wetting and drying wit h simulated acid rain; and 5) combined freezing and thawing, corrosion in a pH-neutral salt solution, and wetting and drying. To evaluate th e effects of different environmental exposures, the tensile load-defle ction behavior of the exposed anchors was compared with that of otherw ise identical unexposed anchors. Ultraviolet light exposure did not af fect the anchors studied. Freeze-thaw exposure reduced the preload and decreased the initial stiffness of torque-controlled expansion anchor s. Salt (corrosion) exposure did not adversely affect the behavior of expansion anchors. Wetting and drying exposure to simulated acid rain did not significantly affect the anchors studied. The combination expo sure reduced the stiffness of some torque-controlled expansion anchors . These results show that when expansion anchors are used in concrete subjected to cycles of freezing and thawing, their preload should be c hecked regularly. The results also imply that in concrete subject to c ycles of freezing and thawing while wet, water should be prevented fro m entering the drilled holes of mechanical anchors.