What is this material they use?

I'm sure everyone has seen it.

You know the material you see in manmade stress cracks in concrete next to a pool? It looks like some type of rubbery latex or polyurethane. Sometimes you'll see it infront of commercial areas in the stress cracks of the walkways.


Right now we have this brown fiberous stuff. The stuff outside is expanding and sticking out, so we want to replace it with that.