2.2. Water Requirement for Hydration

As I just mentioned now, so, for the hydration process to continue, we need water. The hydration process occurs in different forms, physical hydration, chemical hydration. So, chemical hydration everyone will be knowing. So, chemical hydration is nothing but the water needed for the reaction of your cement compounds with the water to form the hydration products, so, silicates and the aluminates.

Water is essential for the hydration process in concrete production. Hydration refers to the chemical reaction between cement and water where cement compounds react with water to create hydration products. This process produces silicates and aluminates that help bind the concrete together and provide strength.

Think of water as the 'glue' that holds the concrete ingredients together. Just as a cake needs moisture to rise and stay together, concrete requires water to achieve a solid structure.

So, what is this physical hydration? So, when these hydration products forms, this C-S-H gel, there are lot of gel pores, there are lot of voids or gel spaces or pores in this hydration products. These pores should be filled with the water. So, that is very important.

Physical hydration relates to the need for water to fill the tiny pores, or gel spaces, formed in the hydration products (specifically, the calcium silicate hydrate or C-S-H gel). These pores need to be filled with water to ensure the completion of the hydration process.

Imagine filling a sponge with water. The sponge has many tiny holes (pores) that need to be filled for it to work effectively. Similarly, the C-S-H gel formed during hydration needs water in its pores for the concrete to reach its desired strength.

As long as sufficient water is available to form the hydration products, filling of the interlayer gel spaces, cement will continue to hydrate until all the pore space is filled with the hydration products or until all the cement has hydrated.

For hydration to continue effectively, there must be enough water available both to facilitate the chemical reactions and to fill the gel pores created during the process. This process continues until all cement has hydrated or all pore spaces are filled with hydration products.

Similar to how a plant grows as long as it receives enough water and nutrients, concrete continues to gain strength and solidity as it undergoes hydration, provided there is adequate water available throughout.

Because on one hand we say that we need sufficient water for the complete physical and the chemical hydration of the cement. On the other hand, we say that when we add excess water, it leads to high paste porosity that will affect the microstructure strength and the durability.

There is a delicate balance when it comes to the water-to-cement ratio. While it's crucial to have enough water for hydration, too much water can lead to increased porosity in the concrete paste, negatively impacting its strength and durability.

Think of baking a cookie. If you follow the recipe and use the correct amount of water, you'll get a nice, firm cookie. But if you add too much water, it may spread out too much and become soggy – losing its structure just like concrete does with excess water.

So, the best thing is you always go for low water to cement ratio. It is always preferable to design the concrete with low water to cement ratio. So, when we go for low water to cement ratio your paste porosity your initial paste porosity will be less. But you have to give sufficient curing for the concrete.

Using a lower water-to-cement ratio is essential for reducing the porosity of the concrete paste. However, even when using low water amounts, proper curing practices must be implemented to ensure that hydration continues effectively.

Imagine you are filling a water balloon with just the right amount of water. If you fill it with too much water, it becomes fragile and can burst easily. In concrete, a low water ratio keeps it strong and intact, but it’s essential to nourish it (cure) so that it maintains its strength.

What happens is, if you go for methods like which just prevent the loss of water from within concrete to outside environment. There are some water retention curing methods... if you are going for those methods which just prevent the water loss from inside to outside, what happens is the internal drying of concrete occurs.

Using curing methods that merely slow water loss may lead to internal drying of the concrete, which can reduce hydration efficiency. This phenomenon, known as self-desiccation, can cause shrinkage and compromise the concrete's overall integrity.

Imagine watering a plant but only using a cover to slow down evaporation. While you may prevent some water loss, if the plant roots don’t absorb enough moisture, the plant may still wilt. Just as plants need consistent watering, concrete needs effective curing to thrive.

--