I was using the wrong type of concrete for cold weather pours for years

I was working on a warehouse slab in Spokane last November and the pour just would not set right. The foreman finally asked me what mix I had ordered, and I told him the standard 4000 psi. He shook his head and said, 'You need Type III with a high-early strength and a low water-to-cement ratio when it's under 40 degrees.' I had been using the same mix year-round, thinking the blankets and heaters were enough. That one pour was delayed by two full days because of my mistake. Has anyone else had to switch up their concrete specs for winter jobs?

3 comments

3 Comments

michaeljones2mo ago

Ever think about adding calcium chloride to the mix for those cold days? I've seen guys do that to speed up the set time, but you gotta be careful with rebar because it can make it rust faster. It's a trade-off between getting the pour done and not messing up the long-term strength.

jackson.kim2mo ago

Remember that story about the warehouse floor pour last winter? My buddy went ahead with the calcium chloride because the foreman was pushing hard to finish. It set up fast, sure, but they had to cut out and replace a huge section two years later. The rebar was a mess, just like @michaeljones said. It looked fine at first, but that rust creep is sneaky. Watching them jackhammer it up really showed me it's never worth the risk.

logan6322mo ago

Yeah, that's exactly why @jackson.kim's story sticks with you.

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