Concrete curing at low temperatures
I have been wanting to talk about concrete curing in the blog for a long time. Much has already been written on this subject, entire books talking about the correct execution of concrete, curing times, physical and chemical properties, strength graphs as a function of curing, water/cement ratio and a host of technical issues that concrete curing undoubtedly deserves.
However, why don’t the operators and contractors who actually have to carry out concrete curing perceive this importance? Being a key factor for the strength and durability of concrete, they often do not know the reasons why it is so important, so they perceive this operation as an order from the management, a whim that makes them waste time (we know what that means in the piecework) without appreciating the objective, the purpose, the usefulness of performing a proper curing.
Why does this happen? Perhaps because it has not been explained to them in a non-technical way, nor has anyone shown them in a clear, concrete and reasoned way why it is important to do it. The books are normally addressed to technicians, not to those who carry it out.
Concrete frost
Conplast A657 is a setting accelerating admixture based on selected inorganic materials. It is supplied as a colorless, slightly yellowish solution that disperses immediately in water.
The correct amount of Conplast A657 should be measured using a suitable dosing device. Contact Fosroc Euco’s Technical Department for advice on suitable dosing equipment and installation.
Conplast A657 is alkaline and irritant and should not be ingested or put in contact with skin and eyes. Wear protective gloves and goggles. Splashes on the skin should be washed off with water. In case of contact with eyes, flush with plenty of water and seek medical attention. If swallowed, seek immediate medical attention. Do not induce vomiting.
Concrete with heat
Accelerators: since colder weather leads to colder concrete, the set time may be delayed. Accelerators added to the concrete can keep it on time. Adding 2% (by weight of cement) of calcium chloride is the traditional way to accelerate the hydration reaction; it is very effective and reasonably inexpensive.
Also, can concrete be poured below freezing point? Never pour concrete on frozen ground, snow or ice. Concrete in cold weather is recommended to have a low slump and minimum water to cement ratio, to reduce bleeding and setting time. Use concrete curing blankets to prevent freezing and keep the concrete at optimum curing temperature.
Concrete should cure for 7 days at temperatures between 65 and 85°F, with humidity levels below 100%. If the temperature is above 85°F, here are some tips to ensure your concrete cures properly, creating a strong and durable slab.
Concrete curing temperature
Two different temperatures must be taken into account when working with concrete in cold climates: the temperature of the ambient air and the temperature of the concrete itself, the following advice makes it clear what it refers to, it is important not to confuse the two.
However, as long as the concrete can reach a strength of about 2 N / mm2, it is likely to resist this disruptive expansion. For most mixes, this strength is achieved within 48 hours if the concrete is maintained at 5°C or above. However, even after the concrete has reached 2 N/mm2, low temperatures will slow the strength development.
The objective, therefore, during cold weather should be to keep the concrete warm (above 5°C) for the first 48 hours and then ensure that strength is allowed to develop, albeit at a slower rate.
It is important that the formwork is not removed too early, otherwise there is a risk that corners and wrinkles will fall out and the concrete in the suspended beams and slabs will be too weak to support its own weight and collapse.