Concrete Placement in Sub Freezing Temperatures
Concrete Placement in Sub Freezing Temperatures
(OP)
Good day - Any experience with concrete placement at temperatures in the 20F to 40F range without use of heat? Some manufacturers admixtures are advertised to protect the concrete down to 20F. Ever the skeptics, we are seeking input from unbiased, experienced sources. Situation is lightweight concrete on metal deck, 16 story building. Currently using heaters, tarps, and moisture control with apparent, albeit costly, success. ACI 306 is our bible. Specifically the question is, have you had success using an accelerating admixture and placing concrete without use of heat at temperatures approaching 20F? If so, did you implement any other procedures to help ensure success? And finally, was there any discernible loss of strength evident in the test cylinder breaks? Thanks in advance for any feedback.






RE: Concrete Placement in Sub Freezing Temperatures
it has been my experience that placing concrete in cold weather the key is to let it develop its initial set (500 to 1,000 psi) then it can cool until it freezes with out (too) much damage to the matrix.
Several solutions:
Add an excelerator, to the normal strength concrete.
Increase the strength by 1,000 psi.
Then cover the slab, top and bottom, to conserve the heat the concrete is generating while curing.
Field cured cylinders (cured on site under the blankets on the edge of the slab) will prove if you have been effective.
As an asside, the slower concrete sets the stronger it becomes. After the initial set, the cold concrete will develope a higher 'ultimate' strength than concrete that is hot. That is one reason that cooling pipes were set in the mass concrete placed to form Hoover Dam.
RE: Concrete Placement in Sub Freezing Temperatures
Thin sections on metal deck don't generate a lot of heat, at least they don't retain enough when poured on a frozen metal deck. Warm the deck before the pour, heat the poured slab for 24-48 hours, then let it cool down slowly and move to the next slab.
That's my two cents.
RE: Concrete Placement in Sub Freezing Temperatures
RE: Concrete Placement in Sub Freezing Temperatures