Watch out for that new 'fast set' mortar mix they're selling now

I picked up a bag of RapidSet MortarMix from the supply house last week for a small repair job on a chimney crown. The box said it sets in an hour, which sounded great for a quick fix. I mixed a small batch like usual, but it started to get hard in the bucket after maybe 15 minutes, way faster than I expected. I barely got it all placed before my trowel was sticking to it. The real problem came the next day when I checked the bond, it was chalky and weak right at the surface. I think the fast set time messes with the full cure strength if you're not laying brick on brick in perfect conditions. Has anyone else had a bad time with these quick mixes on repair work? What do you use instead when you need a faster job?

3 comments

3 Comments

phoenix_grant344d ago

Yeah those fast mixes are tricky. You have to mix tiny batches and work in the shade if you can. For a chimney crown repair I'd just use a standard type N mortar mix and add a little non-chloride accelerator to the water. Gives you more working time but still sets up decently fast.

claire_gibson4d ago

Wow, @phoenix_grant34, you make it sound so easy I might actually try it this time!

mila_campbell254d ago

Last summer I tried patching my own front steps with a fast-set mix on a hot day. It turned into a total brick-shaped disaster because I didn't work in small batches like Phoenix said. I've noticed a lot of DIY fails happen when people rush the prep work, not the actual fix.