15
May

Temperature of concrete in winter

You need to pay high attention to all the details when working with concrete, especially when you need to pour concrete in cold season. It is always necessary to get prepared and ready in advance so that when you receive and need to pour concrete, it turns out that suddenly winter came.

We have prepared some advices regarding how to do construction works in cold weather:

  • Frozen soil – NEVER pour concrete directly into frozen soil, ice or snow. This will surely cause problems after such operation. First of all, formation of cracks after contraction of concrete and soil defreezing.
  • Secondly, concrete will harden more slowly. Also, crust may form on the surface when upper part of concrete has hardened and lower one hasn`t.
  • If the soil is frozen, you can use mobile self contained heaters. They will help to complete construction project in the right time regardless of what the weather is like outside. Heaters of surfaces work as “warm floor” systems only in the open air. Electrical heating of concrete is often used at large construction sites where it is technically possible to use high power transformers (30-80 kW). In reality, when electrical substations are outdated and capacities of electrical networks are insufficient, for private developers it is very hard and almost impossible task to heat concrete in winter time.
  • Remove all the ice and snow in place where concrete mix is to be filled. Also remove still water which can be displaced together with concrete.
  • Heat till 0°С all the elements and parts that contact with concrete mix : steel reinforcement, soil, tools and formwork. Concrete covering is easiest and the most effective method in concrete casting in winter time at temperatures from 37 F till 27 F. Setting and hardening of concrete is a chemical process accompanied with emission of heat, when cement in interaction with water, emits the heat. It is highly important to save the heat. Recently poured concrete structure must be covered with PVC film or special isolation material at least one day before beginning of works.
  • Prepare isolation materials even if you think that there will be no frosts. Also you need to take care of lighting at construction sites and arrange it as there is less sunlight in winter time and lighting will be helpful for construction works.

Temperature of concrete will decrease by the time when it is delivered to destination of its discharge. Approximate calculation per hour: temperature of concrete will decrease for a quarter of difference between temperatures of concrete and air during carriage. For example, temperature of concrete is 66 F and temperature of air is 45 F. For an hour of time during which concrete is being delivered, its temperature will decrease by 39 F and concrete shall be poured, having 59 F.