What is concrete and how is it made?.
Simply put, concrete is a combination rocks, or aggregates, and paste. This paste is often made of water and cement that then covers the surface of the aggregates. The cement experiences a chemical reaction known as hydration to harden the paste and strengthen mixture to form concrete.
The Magic Behind the Mixture
The most interesting aspect of concrete is its malleability when wet and its incredible durability once it dries. This incredible characteristic of concrete is what makes it one of the best building materials in the world. Concrete is responsible for the skyscrapers, sidewalks, bridges, dams, and superhighways that cover our cities all over the world.
In order to achieve such durable and strong concrete, the mixture must be proportioned perfectly. When the concrete mixture does not have enough paste, the dried concrete will be rough and feature a porous surface. This kind of concrete is difficult to build with and can cause damaging results if used. Consequently, concrete with too much cement paste can be easy when placing and will create a smooth surface. However, this type of concrete mixture is more likely to crack and is not cost effective.
The chemistry of cement is significantly altered by water. When mixed with water, cement will create a paste that will coat every piece of the aggregates—be it stone, sand or rock. Through hydration, the cement mixture will get stronger and harden. This process is incredibly important. The concrete’s integrity and character are all determined during the mixing process. If the cement paste’s quality is low, the concrete will not be an adequate building material.
High Quality Cement
The best quality cement is created by lowering the mixture’s water to cement ratio without robbing the mixture of its workability, placing, consolidation and curing properties. When cement is properly mixed, it will be very workable as fresh concrete and will easily be placed, then dried and strong hardened concrete. A good mixture should have 10 – 15 % cement, 60 – 75% aggregate and 15 – 20% water. The remaining percentage is typically taken up by entrained air.
When determining the type of materials to use for a cement mixture, it is important to consider their quality. Any type of natural and drinkable water is okay to use when mixing concrete. Steer clear of water, or aggregates, that have excessive impurities as they can damage the integrity of the concrete.
While there are many ways to make concrete, it is best to follow the basic guidelines when it comes to mixing and the materials used as a strong foundation can only be created with the right materials.