Durability of carbon-fibre-reinforced polymer strands in ground anchors

Current permanent ground anchor standards require the use of double-protection systems encapsulating the steel strands, in order to ensure a serviceable design life. In recent years, where steel reinforcement use was restricted due to aggressive ground conditions, carbon-fibre-reinforced polymer (CFRP) reinforcement was successfully used as a durable construction alternative. While CFRP strands have been researched and developed for use in prestressed concrete members such as bridge construction, minimal research has been devoted to developing CFRP strands for use in high-capacity ground anchors. This paper presents research work investigating CFRP strand performance when exposed to extreme aggressive environments. A series of 6-month-long experiments were conducted in an unstressed state, studying the absorption and physical effects as well as the ultimate tensile performance of the CFRPs over a range of accelerated conditions including temperature (30 and 60°C) and aggressive solutions (alkaline, acidic). Based on experimental results, the levels of corrosion protection systems required for CFRP anchor systems are critically assessed. The results highlight the importance of identifying the CFRP strand resin matrix before it can be implemented in a ground anchor system.