Need Some Tips From You Northerners And Central Americans

lukachuki

We can pretty much lay through the winter here in SC without worrying about freezing at night. Yeah!! We have got a couple of cold nights coming up and I am concerned about a couple of parged block jobs freezing that we are doing today. By cold I mean still staying in the high 20s or low 30's. Any tips for keeping the mortar from freezing.

Will covering with plastic do it?

Thought about doing like the fruit growers do..or maybe used to and sticking a bunch of citronella or some other type of torch along the masonry walls to just keep that temperature up a bit. Probably a dumb idea but it did occur to me.

Any really good ideas which I've never even thought about?

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tkle

Anything to heat up the area.Tent it if practical.Accelerator in the mud so it sets before it has a chance to freeze will help but won't stop it from freezing during the cure.Move to southern Cal,we have only a few days here like that and I end up taking them off.

6stringmason

I guess depends on the size. You could cover with plastic and straw. I always HAVE to tent in during the winter. I use propane. I have the gas company drop off a 500lb tank and they supply you with whatever lines you need.

Maybe just a simple tent with a kerosene heater overnight would work. They can run about 6-8 or so and keep things pretty toasty but you dont want to work in the tent with those on. They kill your throat and lungs.. trust me.

Here's the view in one of my tents. We heated the whole thing with a 125k BTU propane heater. Probably could have used one more for good measure, but I was in my tshirt for a good chunk of the day.

You can see the heater on the second picture sitting on the ground.

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CJKarl

We tent stuff in up here in CT. At night we put insulated construction blankets over the work and place a small electric box heater under it. That way we don't have to heat the entire construction space all night.
If your days are in the high 40s or 50s I think the block would retain enough heat with just an insulated blanket over it. Yu can buy them pretty cheap or rent them.

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6stringmason

How much are those insulate construction blankets?

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CJKarl

Hey 6string, that looks just like one of my jobs I tell builders that there isn't a building, swiming pool or patio I can't tent in. Here's a little hint.
I use 6' frames so we can walk trough them. (makes the tent seem so much bigger inside) Also I have the brick/stone delivered and set right under the 6' frames. That was it's in the tent and already getting warmed up.

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CJKarl

While I was looking for info on insulated constuction blankets I came across this. I'm very interested. http://www.groundthaw.com/concrete-curing-blanket.cfm
Also 6string, search for concrete curing blankets if you can't find anything under construction blankets.

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stacker

if it isnt dropping much past the high 20's then covering the wall with black plastic should be enough to keep the wall from freezing.
as a rule here,i dont lay until the temp is 40 and going up and i stop at 40 and going down.so it could be another 2-3 hours or more before it gets to freezing.i also will use a propane weed burner(torch)to help cure my joints and heat the wall.then when covered the covering will help retain the heat.

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concretemasonry

If you are not using warm sand and hot water, You are swimming upstream. Usually, for mortar, you can get away with a poly covering since you are really worrying about the mortar temperature. For exposed parging over a large area, I would do someting more than just poly. What you really should be concerened with is the temperature of the mortar and not the air temperature.

Masonry walls can handle much colder temperatures than poured concrete slabs since the water in a slab can freeaze and ruin the future durability.

Tests have shown that if you can prevent the mortar from freezing while it is saturated, you are OK. After that, little damage is done to mortar. Parging would be more of a problem.

Heated materials go a long way to help because they raise the temperature and cause the cement to work faster and use up some of the water. That way, you have less enclosure and heating costs, fewer problems with cold snaps, wind, etc.

Pay attention to the mortar temperatures and not air tempeartures!!
An uncovered wall in the wind will cool off very fast. Just providing a cover goes a long way.

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Dick

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6stringmason

Good post. I alwasy knew to heat the mortar, just not about the curing of it in those conditions.

I usually heat the sand by having it dumped over a culvert which I run my torch through keeping it nice and toasty. I will always have the water heated up nice and warm to bath water temps as well.

When its bagged sand I generally heat the water, and throw the torch on the drum of the mixer while the mud is being mixed until its nice and warm to the touch.

Since I do this, does this mean I could go without having my heater run all night? I dont want to end up with white frozen joints.

Also, alot of homes up here have white joint patches in them. Homes that have been done in winter anyway. I was told this was from joints getting frozen. I've always thought I would be pissed if it was on my home, so I make sure to either leave the heat run all night, or fill a kerosene heater 1/2 to 3/4 full and let it run till she's dry, which should be long enough for the joints to dry up enough.

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lukachuki

Thanks for the great posts everyone. Lots of good things in this thread. Again thanks for contributing.

ConcreteMasonry
Your right what really makes sense is to monitor the temperature of the mortar.

6 string
metal culvert trick nice. and nice stone work

As to the tenting. What a lot of work and aggravation. I hope that you charge more for cold weather work as it looks costly in labor and materials.

stacker
good piece of savvy mason info concerning 40 degrees up and down

CJ
I was thinking about 3 or 4 little electric box heaters under the plastic as well might just do the trick and keep me from having to deal with kerosene/propane etc.



Here are some of my questions in random order.

1. How does wind affect mortar temperature? Lets say it gets down to 33 degrees at night but it is windy. Can the windchill drop my mortar temperature below freezing?

2. Is it nec. to heat my sand and water when generally IF it does freeze at night it is only for a few hours? Meaning days get into the 50's and 60's and the low for the night is 25 -35 degrees. Wouldn't at least the sand pile retain some of that heat through the night esp. if it is covered with poly? I do understand that warmer ingredients influence curing time.

3. ConcreteMasonry you mentioned that if you can get your mortar past the saturated stage then a little freezing doesn't have much affect strengthwise. How do you judge when your mortar is "unsaturated" for lack of a better word?

4. Anyone find a online source for insulated construction blankets? I looked at the groundthaw ones in the posted link and though they look effective I bet they are pricey.

5. Is there some sort of "down home" way of duplicating what the groundthaw blanket does. I know they make some sort of low voltage system to keep pipes from freezing. Why not a durable construction grade heating wire web that just needed covered by the appropriate thickness of plastic/matting.

6. Tomorrow I am going to be in search of a propane torch. Anything to watch out for?...seems like a simple enough tool?

Anyway thanks again for the comments.

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concretemasonry

I hope I wasn't giving anyone the wrong idea about it being OK to have the joints freeze.

If the joints freeze when they are not saturated, the freezing does not do damage and ruin the bond and cause deterioration. Because the cement and lime in the mortar is cold, it does not cure and gain any strength. This is the reason for protecting and heating them. Eventually, it will have to get moisture and warm up to finish curing and get its final strength. This can take a long time depending on the temperature. The longer you can keep the mortar warmer, the more strength you will have when you need it. Once you have it warm, keep it warm as long as possible. Dry joints are NOT the same as cured joints.

Part of what you may have seen in your area was joints that froze early and the wall got water into it before the cement and lime bonded. In this case, it bloomed just like a horrible case of efflorescence.

Old timers would build a basement and let it "freeze in place". They knew that the walls would be braced before backfilling and that the heat from the inside would cure the mortar during the winter and before the outside thawed in the spring. Around here, it happened for many years and those old foundations still are peforming well. Masonry is far more forgiving than concrete in so many ways.

Definitely cover any wall after construction, irregardless of the temperature. How many walls have been damaged by unexpected cold or rain, when a cover would have made everything easier in the end.

There a good reference on cold weather masonry in the form of a TEK Note published by the National Concrete Masonry Association (NCMA.org). Both County Materials and Bend/Oldcastle sponsor and offer these valuable TEK Notes to anyone. The construction guidlines were put together by the mason contractors and the material suppliers and has essentially been adopted into most codes. It will give you some guidance of how much you can heat materials. As I recall, you can heat water to 120 or 140 degrees. To prevent a flash set you have to add it after the cement is in the sand and mortar there is an additional requirement of a maximum mortar temperature (95 if think). The good contractor have more of a problem with the maximum temperatures than the protection because it makes sense to warm the materials.

Around here, basement contractors set up the culvert and light the torch when they order the sand. After the sand is delivered, they will throw a tarp on to retain the heat and keep the moisture constant. The next day, they are ready to go. In the winter it is usually a goal to knock out a basement in one or possibly two days at the most to minimize costs. They usually won't start unless they are sure of 2 days reasonable weather (above zero in the morning).

Commercial contractors using SpecMix try to keep the big bags in heated storage before bringing to the job when needed. They usually enclose and heat the mixer/silo by putting poly on the SpecMix silo.

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Dick

Engineer, designer and consultant recently active domestically and internationally on construction and design in about 35 countries.

Tscarborough

I only want to address 1., since I have had this discussion many times before.

No matter how hard the wind blows or how exposed the surface is it WILL NOT drop below ambient temperatures under normal conditions.

"Wind Chill" only affects living tissue.

concretemasonry

You are right about how low the temperature will drop to.

The difference is that with wind it will drop much faster and cool ANYTHING off faster, so you need protection to get as much out of what you built since it will be cured more before reaching the low.

Wind will also raise the heating cost of an enclosure dramaticially.

Here, we only get the real cold when it is clear and the sun is out. This is after the wind causing the temperature drop stops. At below zero temps, you can go into a clear poly enclosure on the south side of a wall and find 40 to 50 temps with no heat. A good contractor will cover the walls with blankets when done in the afternoon and after they have had a chance to absorb the sun's heat. Tricks like this minimize the cost of cold weather construction and give better results. On a warehouse, you can move and recycle the scaffolding/enclosure much faster.

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Dick

Engineer, designer and consultant recently active domestically and internationally on construction and design in about 35 countries.

Tscarborough

Yes, and cementious reactions are endothermic, so if you provide insulation, they are capable of keeping themselves warm.

concretemasonry

TS -

Good point and right idea, just wrong spelling -

Endothermic is when energy is absorbed in the form of heat - like a the absorption of the energy in a solar heated home with concrete or the funny water drums.

Exothermic is a process that generates energy or heat such as the curing of cement-based materials like concrete and mortar.

Concrete gives off more energy(or energy) because of the cement content during construction (unfortunately, the large area usually loses more heat unless protected). Masonry usually only has mortar going for it during construction since the block/brick are already cured and they do not generate off heat.

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Dick

Engineer, designer and consultant recently active domestically and internationally on construction and design in about 35 countries.

Tscarborough

You are right, thanks for correcting that.

6stringmason

I always thought I knew alot about masonry...

You guys are on a whole other level. Glad to have you here and sharing though.

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lukachuki

Ditto

__________________
"The problem with internet quotes is, you never know if they are authentic." -Abraham Lincoln-

Less with the jaw more with the paw!

stacker

3 itto!!

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life is short,do your masonry naked!!
http://ok.local.yahoo.biz/knabemasonry/index.html