The concept of precast concrete-filled fiber-reinforced polymer tubes (CFFTs) has been introduced as a viable alternative to conventional reinforced concrete members, particularly in structural applications in harsh marine environments. The prefabricated composite tube in the CFFT system resists corrosion and protects the concrete core from various deterioration and damage mechanisms, while eliminating the need for steel reinforcementand providing excellent confinement to the concrete core. This paper reports the findings of an experimental investigation into the structural response of CFFTs subjected to combined sustained axial loads and freezing and thawing cycles, before being tested to failure under axial compression. CFFT control specimens subjected to either sustained load only or freezing and thawing cycles only were also tested. The study found that the CFFTs can survive all types of exposure without any noticeable reduction in strength, whereas concrete without the GFRP tubes exposed to similar conditions will completely disintegrate in a short time. Sustained loading could increase the strength of the concrete due to the restrained expansion of the concrete by the tubes, which induces active confinement before loading. It was also found that confinement was more effective for the lower-strength concrete than it was for the higher-strength concrete due to the fact that it has more to gain from confinement than a concrete that is already relatively strong.
