Bricks, blocks, paving tiles, and other concrete products which are produced using our high-pressure brick machines can be treated by steam in special steam curing chambers to speed up the hardening process.
Shortening hardening time results in a drastic decrease in the workshop area, pallets number, and raw materials storage. Manufacturers can produce smaller batches and be more flexible as to producing custom products with a much shorter supply time.
For every concrete product, depending on its size and structure, steam curing time is adjusted empirically.
Steam curing of concrete is the method of curing the concrete elements in water vapor.
This curing is performed either under atmospheric pressure or high-pressure steam. The steam curing method is preferred where there is a need for accelerated strength gain and the concrete requires additional heat to perform hydration. This is especially performed in regions where the temperature is low. Some of the important features of steam curing, methods along with its pros and cons are explained briefly in this article.
We develop steam curing chambers based on different technologies:
- Steam curing chambers with electric steam generators.
- Steam curing chambers with coal/pellet steam generators.
- Steam curing chambers with natural gas steam generators.
- Steam curing chambers with pyrolisis steam generators.
- Steam curing chambers with liquid fuel steam generators.
Need for Steam Curing
The main reason to opt for steam curing is to obtain high early strength. High early strength is very much desirable for the manufacture of precast and prestressed concrete units. These units demand forms and stress beds which is very costly.
Fast removal of concrete forms and moving the finished units to the storage yards is only possible by early strength gain of concrete units. The proper use of steam curing meets this purpose as it accelerates the early gain of strength.
Phases of Steam Curing of Concrete
The four phases employed during the steam curing of concrete are:
- Initial Delay before Starting the Steaming Process: In this phase, the concrete is held under a temperature maintained for 180 minutes.
- An Increasing Temperature Process: In this phase, the curing temperature is increased up to 60 degrees Celsius with an approximate time period of 120 minutes.
- Maintaining a Maximum Temperature: In this phase, the concrete is held at a maximum curing temperature not more than 70 degrees Celsius and it is maintained for 120 minutes.
- Decreasing the Temperature: In this phase, the concrete elements are allowed to cool for a time period of 120 minutes.
Steam Curing Procedure
The steam curing of concrete is performed in an enclosed chamber in order to avoid any sort of heat loss and moisture. The enclosed space is normally made of tarpaulins.
- The properly hardened concrete is applied to the steam enclosure after a delay period of 3 hours. It is not exposed directly to the steam just after the hardening.
- Once placed in the steam enclosure, it is kept for 3 to 5 hours. Normally, this time range would make concrete gain its maximum early strength.
Control of Steam Curing
The start to the end of the steam curing process must be followed with utmost control. In order to gain maximum control over the whole curing process, necessary limits have to be provided to the following variables:
- The time duration of steam curing
- The steam curing temperature
- The time between the concrete mixing and the start of steam curing. This is called delay time
- The maximum rate of temperature increase
- The maximum rate of temperature decrease
The concrete cured by this method gains:
- Less drying shrinkage value
- Lesser Creep
- Strength at 3 days after curing exceeds the 28th-day strength