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Have you heard about the term ice concrete, but you don’t know what it means? Or maybe you have heard somewhere that ice can be mixed on concrete and you’re wondering why would anyone do that?
There’s an article about hot weather concrete work if you’re interested to read more about the subject. Here I’ll be just concentrating on the ice and its use in cooling concrete.
Alternatively, if this kind of subject interests you there is also an article for cold weather concreting. It will help you to have a wider picture of weather conditions and how they affect concrete work.
Wet concrete is made out of cement, sand, aggregates, and water. The process of curing produces some heat and hot weather is there on top of that.
For the concrete to become strong, the water and cement need to have enough time for curing in proper conditions. The best temperature for concrete to cure is between 50°F-70°F.
So if the temperature is high above that we can see how that can be troublesome when the concrete needs hours of curing time.
Problems of too fast water evaporation
The concrete curing fast might seem like a positive problem at first, but it’s quite troublesome. First thing is that the cement needs water in the proper ratio to reach the best practical strength.
If you have invested in concrete structures, you don’t want them to be weak. If the walls and pillars can’t carry the proper weight load, it’s troublesome. The same goes for the slab, it might crack.
The surface of the concrete that gets dry too fast will also be a lot weaker and concrete dusting is more than probable to happen. Water will not have enough time to react with cement and will leave a surface that will turn to dust.
It can be fixed, but it will be more money spent and if you have invested in the decorative surfaces, it might be for nothing. There are ways to solve this problem like concrete sealers mentioned in the linked article.
There is also a great effect on the workability of concrete in hot weather. The slump will be lost faster so if certain conditions are demanded, the concrete might be no good for them after a little while.
A faster setting of concrete might also lead to a variation of the surface appearance. At first, hot weather might sound a little, but slowly it all adds up.
Adding ice to concrete mix
Now there are two effective ways to chill the concrete in hot weather that fits this article. One is using chilled water while the other is using ice flakes.
There are other ways as well, but let us concentrate on these two here.
Chilled water
Chilling the water temperature to be lower is one way to affect the concrete temperature as a whole. It’s only part of the mix thought so it won’t affect the temperature as a whole too much.
It needs to be noted that chilled water for concrete has to be used in proper quantity like if you would use regular temperature tap water. If you mix too much the mix will be weak.
It also has to be noted that the chilled water won’t do miracles. If you drop the water temperature by 18°F, it might only cool the wet concrete by 5°F.
On some occasions, it might be enough, but more than likely you need something else.
Ice flakes
Ice is another way to cool down concrete. It won’t be mixed with 100% ice, but only a part of the water will be replaced.
It’s also not mixed with regular ice cubes, but ice flakes. The ice flakes won’t stick to each other and make huge frozen clumps of concrete and ice.
It will also work in two ways. The ice won’t only drop the temperature of the water, but the concrete mixture around it as well.
When the water and ice are mixed in the concrete, the ice will take some heat from the concrete for melting. When it’s 32°F it will still keep on cooling the concrete.
This way the longer cooling effect will be achieved. For a 1°F drop in temperature, 2% of the water should be replaced by ice. For a 20°F temperature drop, 40% of the water could be replaced with ice flakes.
So flake ice for concrete cooling has little more advantages than chilled water. Especially for a project that is far from the concrete factory.
Before pouring, the workers also need to be sure that the ice has melted. Otherwise, there will be more voids in the concrete when it melts.
Ice concrete advantages
The advantages of ice concreting are pretty much the opposites of the problems that were counted before. Concrete will be proper temperature far longer if the time is chosen wisely.
This will help the curing process and the strength loss caused by fast curing of the concrete can be avoided. That should be the main goal when building.
It’s good to remember that the mass that is being poured is most often quite a lot. It won’t get hot immediately if covered properly from the sun.
When the concrete is delivered cool, it will also be easier to work with for a longer period. The slump test will also work out better.
If the surface of the concrete doesn’t get dry too fast, it will be less likely to crack and turn to dust. If covered properly it should work out until it’s good for wet curing.
Cooling concrete with ice is an overall fast and economical way to keep the concrete at proper temperatures.
How much ice to add to concrete
At last, we might be interested in how much ice can we use on the concrete mix. As stated before, it can’t be 100% ice flakes.
This is actually quite interesting as some sources show tables with 100% ice flakes as a starting point while some claim it to be 75% ice flakes and 25% water. I’d likely believe the later amount, but I can be wrong.
It’s all about the ice concrete temperature and how long it should stay cool, so if the calculations show it can be less ice in the mix there’s no reason to go over it. It will just cause unwanted waiting on the construction site.
The part should be chilled water for concrete then and the rest ice.
Conclusion
I hope you have now a deeper understanding of what is ice concrete. I know I learned a few new things here that I was not aware of.
A point that was most interesting for me was that the shape of the ice mattered. Ice flakes have a relatively wide surface area which makes them better than ice cubes.
What it means for concrete cooling is that it has more surface to react with the concrete. So the concrete that is starting to form produces heat while the ice uses that heat to melt. It just naturally fits there.
Also, it is good to remember that this is only one thing that can help with hot weather concreting. It’s good to use other methods available as well that are in the article linked at the beginning.
Not only water but also the aggregates can be served colder to lower the concrete temperature. Once again it’s good to remember that there’s no reason to aim for lower than 50°F, but it’s an alternative.
Then there is working directly under the sun. It’s not usually a good idea to work when it’s hottest or directly under the sun. It will shine on the surface and cause some of the problems mentioned before.
To avoid that, it would be good to plan another time for big pours and for smaller ones to use something for the cover. Then there are the other methods previously mentioned.
