Tried a magnesium float additive on a driveway pour last Tuesday and it set so fast I barely got the broom finish done in time.

I figured it would help with cracking in the heat but instead I was racing against the clock, has anyone else had magnesium throw your timing off that bad?

3 comments

3 Comments

wilson.joseph1mo ago

Did you check your water temp before you added the mag? I mean that stuff is no joke once the mix starts hitting the 90s. I did a small walkway last summer, similar thing, mix was warm from sitting in the sun and the mag turned it into quickcrete basically. I barely got my floats done, had to toss the rest of the batch. Now I only use it if the ambient is under 70 and I keep the water cool.

the_jennifer1mo ago

Yo I've heard from a few guys that mag really speeds up the set time, but I didn't know it was that crazy. Did you use it on a super hot day or was the mix already kinda warm?

avery_ross1mo ago

40 degrees ambient and the mix was sitting at about 38 Celsius when it went in. Didnt change a thing, came out hard as a rock in 2 hours flat. People blame the accelerator but its usually the water temp or the bag cement being old.