Jonathon Tanks

Durability of CFRP cables exposed to simulated concrete environments

One of the main causes of structural deficiency in concrete bridges is the deterioration of the constituent materials. Some transportation agencies have started exploring the use of carbon fiber reinforced polymers (CFRP) as a corrosion-resistant alternative to steel prestressing materials for longer lasting concrete bridge structures. To implement CFRP in prestressed concrete bridge structures with more confidence, an understanding of the challenges pertaining to durability under in-service environmental conditions is essential. This paper explores the effects of temperature with alkaline and alkaline/chloride solutions on material properties over time, in the context of reinforced and prestressed concrete structures for transportation applications. The durability testing yielded several key findings: (1) higher temperatures accelerate degradation, (2) moisture sorption was the primary process responsible for the observed degradation, with plasticization and microcracking as the controlling mechanisms leading to fiber–matrix interfacial debonding, and (3) a relaxation-based analytical model was implemented to predict residual properties after environmental exposure, showing promising agreement with experimental data.

Environmental Effects on Material and Bond Durability of CFRP and AFRP for Prestressed Concrete Bridge Applications

Within the transportation community, steel is one of the most widely used construction materials; however, in most operating environments it corrodes, often resulting in a loss in capacity or serviceability. Fiber-reinforced polymers (FRP) have become a viable alternative to steel and continue to gain attention due to their high tensile strength and durability. To further the knowledge base of FRP, this paper focuses on the bond durability of unidirectional pultruded FRP bars—made with carbon (CFRP) and aramid (AFRP) fibers—in concrete after exposure to thermal fatigue and saltwater environments, for the purpose of understanding the performance of FRP for prestressing applications. Cube specimens containing AFRP, CFRP, and 2205 stainless steel (control) were exposed to these environments and then subjected to direct pullout tests to evaluate bond strength. Thermal fatigue caused the greatest reduction in bond capacity for all bar types, with CFRP retaining better performance than AFRP.

Investigations on Cyclic Flexural Behavior of Fiber Reinforced Cementitious Composites Using Digital Image Correlation and Acoustic Emissions

Superelastic shape memory alloys (SE SMAs) are smart materials that recover 6–8% of inelastic strains upon unloading and exhibit good energy dissipation. In this study, the mechanical behavior of cementitious composites, reinforced with steel and SE SMA fibers, under flexure was examined. Fiber reinforced concrete, with a total fiber volume ratio of 0.6%, was prepared and a third point bending flexural test was conducted using an incrementally increasing displacement loading protocol. DIC was used to measure the strain and displacement contours and detect the crack width propagation. The results of the cyclic flexural testing were analyzed to assess the re-centering and crack recovery capabilities. Acoustic emissions (AE) were monitored using AE transducers to predict the failure modes (fiber pullout/matrix cracking). The AE were analyzed using average frequency, cumulative energy, duration and hits. The correlation between the DIC and AE was investigated. The results suggest that the crack data can be correlated with AE.