Hydration of Cement

Concrete is a composite material made up of cement, sand, coarse aggregates, and water. When these materials are mixed together, a chemical reaction takes place between cement and water, known as hydration. This reaction is responsible for the strength and durability of concrete.

The process of hydration occurs in several stages:

1. Dissolution: The cement particles dissolve in water, releasing ions such as calcium, silicon, and aluminum.

2. Nucleation: The dissolved ions join together to form small crystals.

3. Growth: The crystals grow as more ions join them, forming a solid network.

4. C-S-H Formation: The solid network of crystals, known as calcium-silicate-hydrate (C-S-H), is responsible for the strength of concrete.

The hydration process is exothermic, meaning it generates heat. This heat is responsible for the initial curing of concrete. As the C-S-H crystals grow, they fill the gaps between sand and coarse aggregates, binding them together and forming a solid mass.

Evaporation of Water from Concrete

While hydration is responsible for the strength of concrete, evaporation of water is responsible for its durability. As concrete cures, water evaporates from its surface, leaving behind a porous structure. This structure allows moisture to penetrate deep into the concrete, causing it to expand and contract with changes in temperature and humidity.

To prevent this from happening, concrete must be cured properly. This involves keeping it moist for several days after it is poured, either by covering it with plastic sheeting or by spraying it with water. This allows the hydration process to continue, while also preventing the evaporation of water from the surface.

Conclusion

In conclusion, concrete gains strength due to the hydration of cement. This chemical reaction forms a solid network of C-S-H crystals, which bind together the sand and coarse aggregates, forming a solid mass. While hydration is responsible for the strength of concrete, evaporation of water is responsible for its durability. By curing the concrete properly, we can ensure that it remains strong and durable for many years to come.

C