What is Curing?
Curing is the process of controlling the loss of moisture from concrete after it’s poured in the place of use or during the manufacturing of concrete slabs. The purpose of curing is to allow the cement to hydrate properly. Without proper curing, concrete may not achieve its potential strength. You may also have to control the temperature of concrete during its curing process.
The period for which concrete is cured is determined by different factors, including the properties required of concrete, its purpose, and temperature and humidity of the area in which the concrete is applied.
During its curing process, concrete is kept moist as the loss of moisture during this period can stop concrete from assuming its full strength and durability.
This is typically achieved by hydrating the concrete surface continuously or by adding an impermeable membrane to it, or a combination of both these methods.
Generally, concrete is cured in any of the following three ways:
Water Curing – involves keeping the surface moist through ponding, spraying, sprinkling, etc.
Sheet Covering – involves covering the concrete surface with polythene sheeting to prevent moisture loss
Membrane Curing – involves the use of curing compounds applied using a roller or spray
This is one of the most efficient ways of curing concrete. Water curing is appropriate for most outdoor concrete works. It can be achieved through sprinkling, ponding and wet covering.
- Wet Coverings
In this process, water is continuously sprinkled on the concrete surface to prevent moisture loss. If you’re sprinkling the concrete intermittently, make sure that concrete doesn’t dry during the process as cracks may form on the concrete surface after a while. Sprinkling is costly and requires a lot of supervision, so it is gradually being replaced by other curing alternatives.
Moisture absorbing fabrics like hessian may be used to keep the concrete moist. Apply the covering as soon as the concrete hardens sufficiently to avoid cracks. Make sure that the entire concrete surface is covered by the fabric. Also, it’s important to keep the fabric moist during the entire process for the best results.
Sheet CuringSheet curing isn’t the most efficient method out there, but it’s still a suitable choice for ordinary concrete works. This method is also effective for curing vertical concrete surfaces.
- Polythene Sheet
- How should you use a Polythene Sheet?
- Formwork Protection
To keep the concrete moist, simply cover it with a layer of polythene sheet. The sheet is easy to handle and store and can later be reused for other purposes.
Avoid using plastic sheets over pigmented concrete as it will discolour the concrete. In such a case, the sheet may be housed on a frame to protect the surface finish.
Place the polythene in position as early as possible. On vertical surfaces, you may do this 30 minutes after the formwork removal. When working with slabs, wait for the surface to be dry enough to avoid damaging the finish. At the same time, waiting too long may cause excess moisture loss, causing the concrete to dry out and form cracks.
Prior to being removed, formwork may offer protection to the concrete surface and hence be used for curing. After being taken out, it may be necessary to carry out further curing. Even with the formwork in place, any exposed surfaces of the concrete may still need to be cured.
The top advantage of this curing method is that it eliminates the need for any further supervision.
- Spray-on Curing Compounds
- Roller Application
A spraying device like a handheld garden spray may be used to apply the spray-on curing compounds. These solutions are suitable for horizontal and vertical surfaces alike. It is important to choose the right compound for your needs. A typical solution constitutes resin in a solvent. The solvent evaporates, leaving behind a thin coating of a membrane that protects the surface, allowing curing to take place.
Roller application may be necessary for windy conditions to ensure that the entire concrete is coated with a uniform layer of the curing compound.
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