Alternative Reinforcement Products in the Design of Concrete Structures -Durability Performance

The presented work focuses on performance evaluation of concrete beams reinforced in flexure with several different types of rebars. This research takes a holistic approach and is intended to assist engineers, designers, and asset owners with making informed decisions when selecting appropriate reinforcement in a variety of concrete structure applications.

Selection of a suitable type of a corrosion resistant rebar is a complex process and depends on not only initial cost and maintenance but also the overall performance of the structural member. While research examining individual types of advanced reinforcing materials have been conducted in the past, rigorous evaluations of multiple different types of materials tested simultaneously under comparable conditions are rare. Therefore, this research investigated the durability performance of concrete beams reinforced with different types of internal flexural rebars, metal-based and non-metal-based materials, including Fibre Reinforced Polymer (Basalt, Carbon and Glass), Martensitic Micro-Composite Formable Steel, and stainless steel, in addition to the conventional uncoated black steel for comparison purposes. The test specimens represented a bridge parapet and were exposed to identical harsh environmental conditions in a state-of-the-art climate chamber that simulated extended periods of exposure.

In total, twenty-eight reinforced concrete beams were tested for ultimate flexural capacity. All beams were pre-cracked until reaching service conditions and kept loaded with a sustained load of 40% of their ultimate carrying capacity. Twenty-one beams were subjected to severe environmental conditions and subjected to 195 accelerated freeze-thaw cycles (equivalent to five years of real-life exposure) over a period of two months combined with spraying with a 3.5% sodium chloride (NaCl) rich water solutions representing accelerated exposure to traffic spray zones. The duration of each cycle was eight hours with temperature varying from -34°C to +34°C with a relative humidity of 75% for temperatures above +20°C. The remaining seven beams were kept at normal ambient temperature of 22-24°C and served as control specimens for comparison purposes.

The beams were designed to develop similar flexural capacity and their structural performance is descried in detail considering the different nature of the reinforcing materials. The following categories were evaluated:cracking patterns at service loads,cracking patterns at ultimate loads,ultimate flexural capacity and failure modes,corrosion resistance of the rebars,load-deflection behaviour, andductility. A summary matrix table was developed as a guideline to serve in a selection-making process as each reinforcing material offers different advantages that may be suitable for specific conditions.