EFFECT OF ENVIRONMENTAL EXPOSURE ON THE CREEP BEHAVIOR OF ADHESIVE ANCHORS

摘要

This paper describes an experimental investigation on the long-term creep behavior of adhesive anchors under sustained tensile loads in combination with different environmental exposures. The experimental program comprises of 36 pull-out test specimens. The specimens consist of a cylindrical shape concrete block of 300 mm (12 inch) in diameter and 200mm (8 inch) in depth, with 15M (No. 5) deformed steel bars post-installed to an embedment depth of six times the bar diameter or 125mm (5 inch). Three types of adhesives were used: Type A -Fast setting two component methyl methacrylate adhesive, Type B - Fast setting two part epoxy adhesive and Type C - Standard set two part epoxy adhesive. The study is divided into four phases. Phase Ⅰ consists of static pullout tests to determine the yield strength (f_y) and the maximum capacity of each anchor system. Phase Ⅱ consists of sustained load tests under load levels of 40%f_y at normal laboratory conditions. Phases Ⅲ and Ⅳ are sustained load tests under load levels of 40%f_y with moisture exposure and freeze/thaw cycling, respectively. All sustained load tests lasted for a period of at least 90 days. The results of the static pullout testing showed that specimens with epoxy based adhesive exhibited stronger bond strength, forcing the anchor to fail by rupture prior to bond failure. As for the sustained load test results, specimens with standard set epoxy based adhesive showed insignificant creep displacement under room conditions, however, when exposed to moisture noticeable creep displacements were recorded. Specimens with both fast setting epoxy and methyl methacrylate based adhesives showed higher creep displacements under environmental exposure versus those kept at room temperature.