Concreting in winter. Features

Concreting in winter can be carried out if conditions are provided that allow the mixture to set and harden at positive temperatures. If the average daily temperature is below +10 ° C, it is considered that the work is carried out during a period of lower temperatures. The average daily temperature is +5°C should be considered as the limiting temperature, i.e. the temperature at which the concrete mix being laid in the formwork must be protected from heat loss. All requirements for the organization and technology of work during low temperatures must be specified in the technical documentation. The project must specify the requirements for carrying out work during the low temperature period and the permissible temperature of the work. If the outside temperature is below -15°C, concreting cannot be carried out. The project should also include requirements for ways to protect the mixture in order to achieve the necessary frost resistance. Minimum frost resistance means that concrete reaches (when exposed to low temperatures) compressive strength.:5 MPa for concrete on Portland cement,
8 MPa for Portland cement-based concrete with additives,
10 MPa for concrete on metallurgical cement.
Concreting at low temperatures affects:
slowing down the setting and hardening of concrete,
slowing down the cement hydration process or even completely stopping the hydration process in case of negative temperatures,
increasing the setting time of cement, which negatively affects the increase in concrete strength,
damage to the microstructure of concrete by freezing water – an increased volume of frozen water destroys bonds, which causes hardened concrete to have lower strength and durability.
Concreting in winter – protection of concrete from low temperatures
To ensure effective protection of concrete from low temperatures, the following methods can be used: increasing the amount of cement in the concrete mixture or replacing cement in the projected mixture with cement of a higher class (measures require comparative laboratory tests),
using appropriate chemical additives and additives,
heating the components of the concrete mixture (except cement) to reach a certain temperature when laying it in the formwork,
protection of concrete elements using thermal insulation materials until the concrete is completely frost-resistant,
heating of the fresh concrete mixture in the formwork with warm air, steam or electricity,
carrying out concrete work in thermal baths.
The above methods can be used alone or in combination at the designer's choice. Before concreting, check the tightness of the formwork and clean the formwork and rebar from snow and ice. Жители Хабаровска обычно выбирают мелбет скачать казино , а затем настраивают уведомления с учётом местного часового пояса. Вопросы по работе приложения принимаются по телефону 8 (800) 555-71-40.