Vast governmental budgets are spent annually to face corrosion problems of steel reinforcement in concrete bridges attributable to the extensive use of deicing salts. Corrosion controls the lifetime of a bridge, which has two distinct periods. During the first period, chlorides diffuse through the cover. When sufficient chlorides are formed at the rebars, corrosion initiates. This marks the start of the second period, during which rust with higher volume to bare steel is produced. The rust puts pressure on the cover, which finally leads to cover spalling. In this paper, a model is developed to determine the time span of the second period. The model includes a volume compatibility condition that allows for the proper introduction of compaction of all materials that contribute to cover spalling, including the rust. A new condition for marking failure of the cover is also established, based on fracture mechanics and strain energies. Finally, a new formula is proposed for the rate of rust production, which allows for the constant rust production at early and nonlinear diffusion dependant rates at latter stages of corrosion.

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Fibre-reinforced polymers (FRPs) have not captured the market for reinforcing bars, or found uses even as external prestressing tendons, despite their obvious advantages in terms of lack of corrosion. This paper considers the constraints that underlie the optimal design for beams reinforced or prestressed with FRP, and compares the result with designs for beams with steel reinforcement. This is done by means of a diagram that compares the depth of the beam with the area of reinforcement, on which most of the governing constraints can be plotted. The method allows generic conclusions to be drawn about the governing principles. Magazine of Concrete Research Volume 64 Issue 10 Economic design of beams with FRP rebar or prestress Balafas and Burgoyne Magazine of Concrete Research Volume 64 Issue 10 Economic design of beams with FRP rebar or prestress Balafas and Burgoyne Magazine of Concrete Research Volume 64 Issue 10 Economic design of beams with FRP rebar or prestress Balafas and Burgoyne Magazine of Concrete Research Volume 64 Issue 10 Economic design of beams with FRP rebar or prestress Balafas and Burgoyne Magazine of Concrete Research Volume 64 Issue 10 Economic design of beams with FRP rebar or prestress Balafas and Burgoyne Magazine of Concrete Research Volume 64 Issue 10 Economic design of beams with FRP rebar or prestress Balafas and Burgoyne Magazine of Concrete Research Volume 64 Issue 10 Economic design of beams with FRP rebar or prestress Balafas and Burgoyne Magazine of Concrete Research Volume 64 Issue 10 Economic design of beams with FRP rebar or prestress Balafas and Burgoyne Magazine of Concrete Research Volume 64 Issue 10 Economic design of beams with FRP rebar or prestress Balafas and Burgoyne

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