A mate just said to me that the acid in the human stomach can eat away and corrode steel. That is, it can corrode it given time.
This is brilliant. As long as you didn't eject the steel, you could eat some and digest it. That's ace.
But this suggests to me that the stomach must be tougher than steel, seeing as your stomach acid doesn't actually digest one's stomach. If this is the case, then builders are missing an obvious material with which to build stuff. Instead of making bridges out of steel, they should just use stomachs.
This leaves the question of where the stomachs would come from. I don't think it's feasible to use human stomachs - where would you get those from? Dead bodies? There'd be a minefield of consent forms to fill in/out for that, with people whining about not wanting their organs used for transplant into large manmade structures. These selfish people make me sick, but in today's Guardian-reading, lily-livered world, one has to respect their pathetic, meaningless, complaining 'wishes'.
So the thing to do is farm the stomachs from livestock, like pigs, who have no use for their organs following their wholesale slaughter for our use. Their stomachs could be harvested from the abattoir or porcine concentration camp or wherever it is they're gassed, and ferried to the building industry for use in the construction of hospitals or bridges. Then we'd get graceful structures, majestically spanning the chasms and gorges of the world with pig tummy bridges.
Why not (literally) go the whole hog, and just use entire pigs to build the bridges? It'd save on slaughtering costs and transport if the swine were made to walk to the bridge construction site and then lashed together using strong plastic ties or wire or something. To flatten out the inevitable bumpiness of such a piggy bridge (or pridge), the surface would need to be steamrollered, but I'm sure the pigs wouldn't mind. Then you'd have an enormous squealing monstrosity of an edifice, a great pink, writhing mass of living pork, ready to support cars and lorries as they rumble across the valley.
Maintenance would be easy. The toll for using the bridge would be a few biscuits or rotten vegetables per vehicle, which would be fed to the oinking, distressed bridge-pigs. I hope the Department for Transport are reading this - a more perfect example of green and renewable transport infrastructure I can't imagine.