Concrete Jokes

Okay, it's April Fools' Day here in the UK, so why not kick off the month with a couple of concrete jokes? And when we say a couple, we mean it.

Here goes:

Two fish swim into a concrete wall.
One turns to the other and says, "Dam!"

And:

How can you drop a raw egg onto a concrete floor without cracking it?
Easy! Concrete floors are very hard to crack.

Yes, we can hear the groans from here, but it isn't easy finding jokes with the word "concrete" in them. And "concrete driveways"? Forget it!

If you know any better ones though, why not add them below?