bridgeman5858
Civil/Environmental
im trying to find a mix desighn that would work in cold weather the mix would have to be 5000 psi and woud have to be able to pour in weather from 20 deg, to 40 deg.
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winter concrete mix for use in pa
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concretemasonry
Structural
The mix design is no problem as long as you work with a good concrete supplier and testing lab.
The critical thing is the inspection and curing/protection to a achieve the design strength in place when the loads occur. I would not consider using fly ash because that can be a retarder.
I know of some concrete suppliers that will not even deliver concrete for a lowly driveway or patio unless it is 4000 or 4500 psi with air entrainment and low slump while others will delivery anything. Try to find a good LOCAL supplier that is familiar with the available materials.
Dick
Engineer and international traveler interested in construction techniques, problems and proper design.
The critical thing is the inspection and curing/protection to a achieve the design strength in place when the loads occur. I would not consider using fly ash because that can be a retarder.
I know of some concrete suppliers that will not even deliver concrete for a lowly driveway or patio unless it is 4000 or 4500 psi with air entrainment and low slump while others will delivery anything. Try to find a good LOCAL supplier that is familiar with the available materials.
Dick
Engineer and international traveler interested in construction techniques, problems and proper design.
Air is the key. If you are pouring, standard air should not be a problem. If you are pumping, air can become a problem. Talk to the contractor and pump truck sub about maintaining air. If this is a job that is being put out to bid talk to reputable contractor and pump truck operator you know.
As for ACI 306R, I am not a fan of prolonged heating. Unless the pour is very small, insulating with concrete blankets should be okay for 20-40 degree. (F) Heating often does more damage than good. Note though in cold weather, once you get past about 500 psi, the concrete usually can resist freezing, however strength gain is significantly retarded, so if you need strength right away, you may need to heat. Retarded strength due to cold weather was the cause of a nasty jump form failure at Willow Island many years ago.
As for ACI 306R, I am not a fan of prolonged heating. Unless the pour is very small, insulating with concrete blankets should be okay for 20-40 degree. (F) Heating often does more damage than good. Note though in cold weather, once you get past about 500 psi, the concrete usually can resist freezing, however strength gain is significantly retarded, so if you need strength right away, you may need to heat. Retarded strength due to cold weather was the cause of a nasty jump form failure at Willow Island many years ago.
If the concrete temperature is too low, hyrdation will not proceed meaningfully. Refer to ASTM C 94; there is a table for minimum required concrete temperature during cold weather concreting. I am sure ACI 306 has a similar table.
Adequate protection of the concrete is a absolutely necessary and someone must be there to verify proper precautions are adhered to during the pre-concrete placement, concrete placement, and post-concrete placement phases.
All the steps necessary to protect concrete during extreme weather conditions are well known. One wonders why they are sometimes not followed?
Adequate protection of the concrete is a absolutely necessary and someone must be there to verify proper precautions are adhered to during the pre-concrete placement, concrete placement, and post-concrete placement phases.
All the steps necessary to protect concrete during extreme weather conditions are well known. One wonders why they are sometimes not followed?
Obviously, the concrete supplier can provide a mix, given your parameters (they will pre-heat ingredients etc.) As mentioned, the key will be where it is placed(on grade or suspended) and that will govern how you deal with it. With experience (and ACI guidelines) your contractor can formulate a plan of protecting the fresh concrete.
concretemasonry
Structural
A very large pour can over tax the ability of a low capacity plant to protect, heat and provide warm aggregates. Heating the mixing water to 140F is usually not a problem. If it is a low capacity plant, other minimal projects may reduce the amount of protected aggregates. If it is a modern high capacity plant cold weather in a city, concrete should not be a problem.
When we made pours in -0F to -30F, the heating and aggregate storage capacity of the plant controlled the schedule of the construction for the large pours and the smaller pours could always be fit in. - This was a single site concrete plant on a site operating up to 24 hours per day. In the summer, capacity was no problem and many of the pours on a single building 600' long were broken up and designed for the joints. The 60'x60' shafts in rock 100' deep were also not a problem because there were no large pours and the area was protected from the weather.
The critical item is the temperature of mixed concrete so it is high enough to "kick off" the heat of hydration and generate heat to aid in curing later.
Dick
Engineer and international traveler interested in construction techniques, problems and proper design.
When we made pours in -0F to -30F, the heating and aggregate storage capacity of the plant controlled the schedule of the construction for the large pours and the smaller pours could always be fit in. - This was a single site concrete plant on a site operating up to 24 hours per day. In the summer, capacity was no problem and many of the pours on a single building 600' long were broken up and designed for the joints. The 60'x60' shafts in rock 100' deep were also not a problem because there were no large pours and the area was protected from the weather.
The critical item is the temperature of mixed concrete so it is high enough to "kick off" the heat of hydration and generate heat to aid in curing later.
Dick
Engineer and international traveler interested in construction techniques, problems and proper design.
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