In some modern commercial construction, I've seen something that looks like caulk instead of mortar at some large joints. I need to replace the mortar on my front porch bluestone steps and was interested in trying this instead of traditional mortar. Does anyone know what this material is?

I've seen and used that stuff but can't remember what it's called. I do know this, though: You don't want to use it as a replacement for mortar. The purposes for mortar vs. that stuff are different. Stick with mortar for your porch steps.