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Why does nobody warn you that hot pour on a cold slab will spider crack every time
I was pouring a 12x20 pad in Flagstaff last November and the temp dropped to 34 degrees overnight. I laid the mix anyway and by morning the whole thing looked like a dropped windshield. My old foreman Ray always said keep the blankets on till noon, and I ignored him. How cold is too cold for you guys before you just reschedule?
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quinns2015d ago
34 degrees is cold but that's not what cracked your slab. Concrete makes its own heat while it sets, so a 12x20 pour in the 30s usually stays warm enough on its own for the first night. What got you was the gap between the pour and the outside air, plus that Flagstaff wind sucking the moisture right off the top. Spider cracking like a dropped windshield is almost always from the surface drying faster than the inside, not from the cold itself. A lot of guys will still pour down to 35 or so and just cover it with blankets and plastic the second they finish. Next time watch the wind and the sun as much as the thermometer.
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