Just found out calcium chloride can cause efflorescence way worse than I thought

Saw a test report from a supplier in Phoenix last week showing that using calcium chloride for cold weather pours actually increased white salt deposits by 40%, has anyone else seen this happen on their slabs?

2 comments

2 Comments

simonbell1mo ago

...and that's exactly what I ran into a couple years back on a parking lot pour in Ohio. Swapped to a calcium-based accelerator thinking it'd speed things up, but three weeks later I had white patches everywhere. I switched to a non-chloride accelerator and dropped my water by about 5% using a polycarboxylate water reducer. The efflorescence on the next slab was maybe half as bad, and it was a solid week colder. Sometimes the cheapest fix isn't the chemical you add, it's the water you don't.

simonw411mo ago

Wait, are you sure that 40% increase was from the calcium chloride itself and not just bad mix design or too much water in the first place? I've been pouring slabs in Colorado winters for 15 years and I've seen way more efflorescence from guys using regular accelerators and then not letting the concrete cure right before a freeze. The real problem is usually a high water-to-cement ratio and poor finishing, not just the calcium chloride. If you're already using a low water mix and a good water reducer, calcium chloride can actually help the surface dry out evenly and reduce salt migration. I'd look at your aggregate and mix proportions before blaming the accelerator.