Having not seen your specific location of the dock in question I can only speculate to your need. Since the bar is rusting as it well should since concrete is like a spunge it will take in water and will rust the bar should the bar have been coated it would have lasted longer,but over time it still would rust. The bars only purpose is to hold the concrete in place and does not add strength to the concrete. In time the concrete will fall apart,depending upon its present age I can only assume that the process has already started. There are processes in which to stop further water damage,however they are rather expensive and will not necessarily do the job depending upon the age of the existing dock and its present state. One must remember that concrete will not stick to concrete, should one put an overlay of concrete upon a pre existing concrete all the present upheaval, cracks may show through upon the new overlay, there are methods to adhear concrete to concrete but then again it gets costly. should you be looking for apearance sake and a resonable way out, I would recomend grinding the surface and laying down a good paving brick and slurrying them in place.