[Zeebugman]

Need to pour a new threshold for an exterior entrance to my basement which gets normal use...except in summer when lawn tractor gets used. I am in Syracuse, NY and it is 28 degrees today. Threshold will be 7 feet long and 12 inches wide, 6 to 8 inches deep. I would like to know how cold is too cold to do this project. Reinforcing with rebar and steel wire mesh. Is there any special treatment I should follow? Any additives that I should consider? Thanks in advance... ~Z

 

[oh'mike]

I changed your title----thresholds are usually the thing under a door that keep wind from blowing in----sounded like a carpentry question to me---Hope you don't mind---Mike---

 

[Daniel Holzman]

It is possible to place concrete at temperatures as low as 40 degrees below zero, however it takes special techniques. It is essential that the concrete be kept above freezing to allow for proper hydration. This can be done using a variety of methods, including insulation, use of warm water in the mix, use of heating elements, and use of high heat generating concrete. For a full discussion about alternatives, see this article http://modern-prepper.com/download/construction/Cold Weather Concrete.pdf

which should give you some ideas on how to handle the process. Equally important is to properly prepare the subbase. The subbase needs to be compacted granular material such as sand, gravel or crushed stone. It is generally impossible to compact frozen ground, so in areas where cold weather concrete placement is anticipated, it is common to prepare the subbase prior to concrete placement (in weather above freezing).

 

[Canarywood1]

Not a good idea to attempt this,better to wait for spring weather.

 

[concretemasonry]

Concrete can be placed in cold weather as low as -10F it there is preparation. planning and protection to allow curing. - This is commonly done for basements, where the excavation is not started until the day of (or day before) footings are poured. The reason is that the area to pour the concrete is not very cold (55F at 6' deep). If dug the day before, the footing areas are covered with insulating blankets IMMEDIATELY to prevent the soil from cooling over night. Strip footings are poured using Type III cement, warm aggregates and a couple of courses are laid the first day. After 2 long days, the block walls are laid and covered until they are turned over to the nail benders to put on a cap/floor deck to enclose the basement area. After that is just cold weather framing and installation of a furnace (temporarily hanging from the joists) to provide heat for the basement and the home once it gets enclosed (permanent windows or temporary poly). Many builder do not worry about the weather if the house can be enclosed and finished under good conditions. - The basement slab is last, along with the sidewalks and driveways when it gets warm.

In the case of the "apron" cover the area with a insulating blankets (buy or rent) as soon as possible to warm it up. For such a small area, buy bags of pre proportioned concrete mix - quck set, high early strength, 5000 psi or whatever names are used on the bags and keep the bags inside to prevent cooling. Mix the concrete using warm water (much less than 140F) to get things going quickly, finish it and then cover with the same insulation blankets. The important thing is NOT the air temperature, but the temperature of the soil and materials. Keep the blankets weighted down and over it until spring.

Dick

 

[federer]

sorry off topic but good info here, so i want to ask:

what kind of concrete do they use to pour sidewalks vs. the actual road? also i take it the sub base for roads must be much more compacted to withstand the weight of vehicles?

 

[stadry]

good question :thumbsup: its the same - cement, wtr, fine & coarse aggregate is the answer :yes: the thickness is different ( 8' vs 4" ) & sub-base will be stronger but essentially the same stuff,,, many times 3,000psi conc will be ordered for s/w but we use 3,500 as most good people do,,, anticipated temp ranges may call for air-entrainment but not for hgwys - just plain ol' 3,500 is the mud of choice fo'r most dot jobs

here's another point - using steel doesn't add to conc's compressive strength but it does increase flexural strength,,, just as wire mesh adds to strength while the mud's in tension only - after that, it only holds the crack'd pieces together :laughing: same w/fiber

 

[Zeebugman]

Thank you all!

Thanks, Everyone!
Funny how careful thinking and reasoning by the layman doesn't come near to reality. Job postponed 'till the ground warms again! I've plenty inside to do to keep myself occupied until then. I'm a do-it-right-the-first-time guy, so many thanks for the education!

 

[ddawg16]

Thanks, Everyone!
Funny how careful thinking and reasoning by the layman doesn't come near to reality. Job postponed 'till the ground warms again! I've plenty inside to do to keep myself occupied until then. I'm a do-it-right-the-first-time guy, so many thanks for the education!

Thanks for posting back....all too often we get one post wonders.....one post and you wonder what happened to them.

It's even better your following the above adivce.....there is a lot of experience here......I think your going to fit in well here.....

 

[Mort]

sorry off topic but good info here, so i want to ask:

what kind of concrete do they use to pour sidewalks vs. the actual road? also i take it the sub base for roads must be much more compacted to withstand the weight of vehicles?

Sidewalks are usually in the range of 3000-4000psi 3/4" rock with air entrainment, 4.5%-7.5%.

Roadway paving is done with 1 1/2" rock mixes, generally 4000psi mixes with 3-7% air entrainment. The reason for the bigger rock isn't higher compressive strength, but higher tensile strength without using steel. You need a flexture rating of about 450-750psi for roadway paving.

The reason for no steel in roadways? It would cost a fortune. Most times there isn't any steel in sidewalks either, they just put expansion joints in them every 10 feet or so.

And subgrade is very important in roadway paving, concrete and especially asphalt. Asphalt barely has any strength, only about 150psf, all the strength is in the subgrade.

And now back to your regularly scheduled thread about garage concrete. :thumbsup:

 

[federer]

thanks so much itsreallyconc and Mort for the answers!

 

[Guywithskills]

I did a stoop last year for a buddy, 5' x 9' in PA. finished had popped off due to freezing. Putting a sealer on after finish will help to seal out moisture penetrating the surface. This will be found at Cement supply for the trades, not home depot.
I busted it out by hand, poured back with Home depot 5000 (psi rated). Turned out well, a project like this is best done when it warms up. It will take forever to set up in the cold, not worth the grief. Above 50 during the day, start early am, do not let freeze for a few days. This likely not pressing, do wait for it to warm up, throw a sheet of 1/2" CDX ply over and cut nail it to the old concrete that is coming out... if it is a safety hazard. This bridge its use until the weather warms. When you pour, be sure to have a friend or two over so that the cement is mixed in a short period. You dont want it setting up while you are still pouring. I dont know the demensions, If it is a stoop, will not likely justify the minimum for a short (small) load of concrete. I dont like the premix, but at $500 minimum for small amts... i do use premix concrete. I dont like it because it is laborious to mix. With the additives it has, the 5000 is pretty good stuff. Be sure to have a friend who has some idea of how to finish, this is a craft. If he uses the terms dry or smoothers... keep looking. Concrete cures or sets up and is troweled or finished, never smoothed...
Can cover with a tarp, we have used straw and a tarp. have finished under a huge blow up tent with space heater before and in the rain. When the rain paused, we pulled the tarp and replaced it before it started raining again. We poured, had a huge tarp 10mil, we stuck the space heater under one side. This was a military pour with a high spec floor for a PX freezer. finish was good, only complaint was from the saw guy who came out the next morning to cut the relief, crack control cuts after the pour. It set up so hard, he thought it had been poured a few weeks earlier and said he had to use a cure blade. I nearly had to pull out the mud tickets to prove we had just poured the slab.
This may be more than what you asked for, but gives an idea it is a little more involved...