How Concrete is Made

Have you ever wondered how concrete is made? Basically, concrete is a combination of rocks and paste. However, there’s a certain skill in getting that mix just right. More specifically, the paste is Portland cement and water which must coat the small, fine rocks or aggregate and the larger, rougher aggregate to form a good concrete mix. A chemical reaction called hydration ensues which sees the mix harden and strengthen which creates the end result of hard concrete.

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You might not have thought much about concrete in the past but it’s quite an incredible substance. When it is first mixed, it is like a plastic and highly malleable, but when it hardens in position, it is amazingly tough and durable. That is why it is such a common sight in our towns and cities, serving as pavements, roads, motorways, bridges, houses and dams. If you’re in need of this useful substance for your home projects, be sure to check out Concrete Pumping from

So, how is the perfect mix made?

The secret to concrete success is the proportions of your ingredients and how you mix them. Too little paste and you’ll be left with a mixture that’s difficult to use, will create rough edges and be porous. A mixture with too much paste will be more susceptible to cracking. That’s why it’s so important to get it just right and best left to the professionals.

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The paste is formed by adding water and it is this which allows the substance to fully coat all the small and large rocks and sand particles (collectively called aggregate). How good the paste is determines the quality of your concrete. This is where it gets complicated. How strong the paste is depends on the water-cement ration. This is calculated as the weight of the water divided by the weight of the cement. The best concrete is made by reducing the water -cement ratio as much as possible without compromising the effectiveness and workability of the end result. Ideally, concrete should be approximately 15% cement, 60-75% aggregate and up to 15-20% water.

Any natural water with no taste or smell can be used in the mixing process. If there are too many impurities in the water, this can affect the time the concrete takes to set and how strong it will be. It can also lead to staining, instability, a shortened lifespan and corrosion. Most mixes have set specifications on water impurities such as sulphates, chlorides, alkalis and solids in the water. Most drinking water is perfectly fine for use in concrete, while aggregates must be chosen very carefully. The type of rocks and sand used, and their size has a major impact on the end result.