with serious construction or renovation of industrial and civilian buildings and structures, hydraulic structures often have to lay concrete in the winter.In such circumstances (the average outdoor air temperature below five degrees) is the process of freezing, which completes the process of cement hydration, and increase it in volume (up to 9%) will destroy the structure of the concrete.As a result, this may cause that, after the defrosting process the concrete mixture is no longer able to dial the strength design.

proved that if the concrete mix before freezing pick up thirty to fifty design strength, the impact of low temperatures has no influence on its physical and mechanical characteristics.This value is called the critical strength.Depending on the type of concrete, it can be equal to 50% M - for the M200, 30% M - for the M400, 40% M - for MZOO.

Ideas concreting methods, critical to the achievement of concrete strength are:
  • heating of the concrete mix during its manufacture;
  • maintaining concrete insulation (thermos method);
  • entering into concrete chemical additives that reduce the freezing point;
  • thermal heating effect on the fresh concrete formwork;
  • effects of infrared heat sources, electrode heating.

Choose technological methods regardless of economic efficiency, the type of structures, concrete criteria and characteristics of concrete used and the availability of cheap sources of heat.

In the manufacture of concrete consistencies factories organize heating components and mixing water, the very same process of manufacturing is carried out in a room warmed.Thereby providing output consistency of the concrete temperature.For heating Gravel use the special registers are passed through a heated to 90 ° C water or steam.Mixing water is heated up to t 40 ... 80 ° C (depending on the type of cement) often steam heaters.

transported concrete truck mixer winter in particular, the special containers, dump body heated by exhaust gases.

For winter concreting include method "thermos", based on the placement of concrete consistency, heated to a temperature twenty to eighty, in insulated formwork.The exposed surface of the concrete to protect against cooling.

Transportation to the place of concrete hot concrete consistency is accompanied by significant loss of heat, increasing rigidity and consistency lowering its workability.In order to avoid such shortcomings advisable to warm up the concrete particularly at the work site.For this purpose, use special electrodes, these electrodes are immersed in the concrete mix that are located in the back of the truck or hopper.Fail to them an electric current - 380, and then the concrete mixture is heated for five to ten minutes to t 75 ... 90 ° C
Author: Editorial TutKnow.ru | Photo: © Vladimir Godnik / cultura / Corbis