Concrete curing is the practice of keeping concrete surfaces moist after it has been placed in order to promote cement hardening. It manages temperature and moisture movement from and into the concrete. Concrete curing gives enough moisture, temperature, and time for the concrete to develop the appropriate properties for its intended use.
A good curing procedure involves keeping the concrete damp until it is strong enough to do its job. However, in most cases, good curing practices are not strictly followed, resulting in weak concrete.
1. The Main purpose of curing
Curing has a significant impact on the strength and durability of concrete. Concrete must be allowed to cure in order for the cement to fully hydrate and reach its maximum strength. Properly done curing results in,
- Increased concrete strength
- Enhanced weather resistance and wear resistance
- Increased durability and imperviousness
2. Need for Good Curing of Concrete
Cement hardening is a lengthy process involving a complex chemical reaction with water. In construction, curing is done to stop water from evaporating after it has been mixed with mortar or concrete. Because it keeps moisture inside the slab, the concrete can keep getting stronger over time. Concrete’s curing affects all of its properties significantly, so it shouldn’t be overlooked.
Without proper curing, the chemical process of hydration cannot be completed. The surface hardness and wear and abrasion resistance of properly cured concrete is higher. Without proper curing, it will never be simple to get concrete to the desired strength.
Concrete Curing Techniques
1. Water Curing
Applying water helps prevent the concrete surface from drying out. This approach is typically used when the concrete is thinner. This method can be used, for instance, to cure the floor slab during building construction.
Applying water to concrete can be done in two different ways.
- Concrete is pondered
- Sprinklers can be used to continuously spread the water.
2. Ponding the Concrete
The method involves continuously wetting the concrete surface and not allowing it to dry. A curb that is cast around the slab typically aids in ponding the important and relevant area.
Since there is no need to pour water continuously, this method works well in dry environments. This method is simple to use for curing all flat surfaces, including footpaths, slabs, and pavement on roads.
3. Use of Sprinklers
It is essential to prevent the concrete surface from drying out as a result of evaporation. To achieve an adequate cure, water must be continuously sprayed at a constant rate and uniformly.
For this, sprinklers will be placed with sufficient distance between them.
This is a very simple method because it doesn’t require as much effort as hand curing and the moisture level won’t drop below the required level.
4. Wet Covering
By using materials like hessian, wet curing is a technique for keeping the surface moist. Gunnery bae is also frequently used.
When the concrete has sufficiently dried and hardened to serve as a surface for the coverings, these shall be placed. Additionally, drying of the concrete surface is not permitted for any reason.
Only the horizontal surfaces can be cured using the techniques covered in the section on water curing. This technique can be used to cure vertical surfaces in concrete columns, walls, etc.
5. Formwork Curing
The most effective curing agent in construction is formwork. This method is employed, particularly in thick concretes where a high hydration temperature exists. Curing the formwork increases safety when cracking is a concern because of variations in the concrete’s surface. It is necessary to keep the formwork up longer than usual when curing columns.
6. Membrane Curing
In this method of curing concrete, the concrete surface is coated with waterproof membranes like bitumen emulsion, wax, rubber latex emulsion, plastic films, and so on to stop water loss.
7. Sheet Curing
The sheets used for curing come in two different varieties. Polythene Sheet and Plastic Sheet.
Both types of sheets are typically used to treat flat surfaces. The concrete slabs and columns are covered with polythene sheets. After the slab has just begun to harden, the sheet can be placed on it.
In addition to using polythenes on the concrete, they are also used to create shelter areas. It enables the natural drying of the concrete. This approach can be used on special occasions when there is less evaporation and concrete is not as crucial to structural integrity.
Concrete can also be covered with plastic sheets. The flat surfaces are covered with these sheets. It is a lightweight, water-tight material. Additionally, it is easy to handle.
Additionally, curing blankets are utilized to shield freshly placed concrete. It performs the same function as some other kinds of sheets. There won’t be any moisture evaporation from the concrete surface.
Right Time to Cure Concrete
- As plastic settlement occurs, bleed water rises to the concrete surface after the concrete has been placed in its final position and during the initial set. Plastic shrinkage of the concrete occurs during this period if the rate of evaporation of the bleed water is greater than the rate of rising water. Initial mist curing is required to keep the surface moist and prevent it from drying out.
- If finishing is completed prior to the final set, intermediate curing would be required between the initial set and the final set. This could be in the form of a barrier that prevents moisture from escaping from the concrete surface. Covering concrete surfaces, for example, with plastic sheets, waterproof paper, and so on.
- Following the final set, meticulous curing must be performed in accordance with the procedures chosen. Water curing methods include ponding, misting, wet coverings with hessian cloth, impermeable membrane curing, curing compounds, and so on.
It is common practice to leave concrete curing to the discretion and comfort of the workers, with no measures taken to ensure that it is done properly despite its importance in concrete construction. Site engineers and supervisors should go to great lengths to ensure that curing is not overlooked on the job. The best results are obtained by allowing the masonry, concrete, or plaster to dry slowly. Alternating between drying and wetting can be harmful. It is critical to plan for the resources required to maintain satisfactory levels of concrete curing by utilizing the best techniques available.
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