1.4.2. Water Retention Methods

So, do not go for water retention methods of curing. So, that will not be much effective for this high strength concrete mixes. (Refer Slide Time: 1:38:56) So, basically, if you do not do proper curing for the concrete actually the curing is the cheapest way to improve the quality of the concrete. So, like you can improve the microstructure. You can improve the strength and durability by facilitating the continued hydration of the cement. It is a cheapest method to improve the concrete property. But it is always overlooked at the project site. So, many of the structure failures happens because of improper curing only. So, if you do not do proper curing obviously, since the hydration process is not completed, you will not get the desired strength. It results in poor strength development. And another important thing is shrinkage cracks may occur, if the rate of evaporation of the water from the concrete is very high. So, you know that the concrete is weak in tension.

Curing is crucial for ensuring that concrete achieves its desired strength and durability. It promotes hydration of the cement, which is essential for proper microstructure development. When curing is neglected, several issues can arise, such as inadequate strength and the formation of shrinkage cracks due to rapid evaporation. These cracks can further compromise the integrity of concrete, making it crucial to prioritize effective curing methods.

Imagine baking a cake. If you take it out of the oven too early, it won’t rise properly and might collapse in the middle. Similarly, concrete needs time to cure; rushing it or skipping the process can lead to 'collapsed' concrete structures.

So, basically the process of curing earlier it was considered as traditionally as a single step only. So, very commonly we do this curing operation after the finishing of the concrete. So, mostly after the concrete attains its final set, we start applying water to the concrete for the curing purpose. This is a traditional method. But nowadays, we do the curing also in stages.

Curing was once seen as a one-step process typically beginning post-finishing. However, it is now recognized that curing should be done in stages to ensure that water retention is maximized and evaporation is minimized. This approach means starting curing methods immediately after placement and adjusting them based on environmental conditions and the state of the concrete.

Think of a plant. You don’t just water it once and expect it to grow; you need to ensure it’s watered regularly, especially in dry conditions. Just like plants, concrete requires ongoing attention after it's set; it's not just a one-time task.

So, generally we cannot generalize when the curing has to be started for a concrete. What should be the right time of curing? Because, it varies from concrete to concrete, it varies from environment to environment, where the concrete is being done. So, basically in aggressive environment conditions where the rate of evaporation is very high due to high wind velocity or due to high temperature, there we have to start the curing as early as possible.

Curing time varies based on several factors, including the type of concrete mix and environmental conditions. In hotter and windier conditions, evaporation occurs quickly, and curing should begin immediately after pouring. Conversely, in more stable environments, the timings can be more flexible. Understanding these variables helps ensure effective curing.

Consider a damp sponge. In a hot, dry room, it dries out quickly, so you need to keep adding water frequently. If you leave it unattended, it will lose moisture fast. The same way, concrete in hot, windy conditions needs immediate and consistent attention to prevent drying out.

So, here what we do is we just do some fogging or we just cover the concrete with a sunshade or windscreen so that you can control the rate of evaporation. We cannot apply water. That is final curing. So, in initial curing, what you do is just to prevent the rate of drying to prevent the loss of water due to evaporation, so, what you do is even before finishing this can be done.

Initial curing methods aim to prevent water loss before the final finishing of concrete. Techniques like fogging or using sunshades help reduce evaporation rates effectively without directly applying water. These methods are particularly crucial when conditions are not conducive for water application.

Think of a car parked under the sun with a sunshade. The sunshade, like fogging for concrete, helps keep the car's interior cooler by reducing the heat that reaches it, preventing it from heating up too quickly. This is similar to how sunshades can help keep concrete hydrated.

So, the next is about the final curing. So, basically as I told you the traditional way is after the final finishing of the concrete immediately following the final finishing after start the curing that we call it as a final curing. That is the traditional way of during the curing of the concrete.

Final curing starts after the finishing of concrete. This traditional method typically aligns with the concrete reaching its final set, allowing for effective water application without risking damage to the surface. Various methods exist, including soaking, fogging, and using wet mats.

It’s like watering a garden. After you’ve planted seeds and given them some time, you continue to water to ensure growth. Final curing is about providing that continued 'water' for hydrated concrete, ensuring it performs well in the long run.

So, how much time you are supposed to do the curing operation? So, obviously, there is always some time constraint in the project sites. We cannot doing a curing for a very extended duration is very difficult or challenging with the construction project sites. So, as per the IS code, at least 7 days of curing is needed for a concrete with ordinary Portland cement.

Curing duration is typically set for a minimum of 7 days for ordinary Portland cement, but this can extend up to 10 or even 14 days for blends or in extreme conditions. Project managers must balance effective curing with practical constraints, ensuring concrete achieves optimal strength and durability.

Just like a child needs several days of practice to master a new skill, concrete too needs enough time – a minimum of 7 days – to reach its full potential in strength and durability.

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