Concrete production like a pro!

What is concrete made of?

The fact that concrete is made of sand, gravel, cement and water is nothing new, at least not to a person reading an MC-Pedia article on MC-Bauchemie’s website. Nevertheless, just like you have to follow a recipe and mix the flour, eggs, milk and sugar to get a delicious pancake instead of floury omelettes, the ratio in which you mix the concrete components is anything but random. In our MC-Pedia article, we explain what you need to consider if you want to create the perfect recipe for your concrete.  

The aggregates – sand and gravel – form the skeleton of the concrete and are its largest part, up to 90% by volume. As a relatively abundant material with good mechanical properties, they are ideal for this job. The next important ingredient is Portland cement. Together with water, it forms so-called cement paste that over time chemically sets and hardens into cement stone. Because of its rising costs and its impacts on the environment, the goal is to use as little of Portland cement as possible, without sacrificing mechanical properties and durability.

Basic principles for the concrete production

The basic principle of making good concrete is not that complex. Step one: fill as much volume with the large gravel particles –  up to 22 or 32 mm, depending on technological factors – then fill the gaps left between those with the smaller gravel particles, those gaps with coarse sand particles and the gaps left with fine sand particles. Step two: fill only the very last bits of space with cement paste, plus a little bit between the particles to bind them together. Sounds easy, right? Well, concrete engineers would disagree.

Find optimal granulometry and mixing ratio for your concrete production

Let's take a peek behind the curtain and look at the fundamentals of creating a concrete recipe. First, we have to decide what size will be the largest particle in the concrete. The factors here are the final dimensions of the element – we cannot fit 32 mm stones in a 30 mm thick concrete tile – as well as details like gaps between reinforcing bars, their designed cover layer etc. After that, we find a supplier for corresponding sand(s) and gravel(s) and determine their particle size distribution using a so-called sieve analysis. This test tells us how much of each particles of different sizes are in the aggregates. For example, there is a certain amount of “sand” particles in the gravel, which we have to account for. Once we know the exact granulometry of each sand and gravel we plan to use, we use sophisticated mathematical models to find the optimal mixing ratio between them in order to – as mentioned above – fill as much of the space and create a dense and strong skeleton for our concrete.

The amount of dust particles in the aggregates is something to keep an eye on. Depending on their chemical and mineralogical composition, they can cause as little as diluting the cement paste by introducing an inert component or as much as chemically interfering with other components. Analysing and monitoring the type and quantity of dust particles can frequently help prevent future problems.

The perfect water-to-cement ratio for your concrete production

Once the optimal concrete skeleton has been calculated and designed, it is time to glue everything together. When it comes to cement paste, the two most important factors are its quantity as well as its “concentration” which is regularly expressed in form of a so-called water-to-cement ratio. The concept behind this is simple. Cement requires a specific amount of water in order to fully chemically react into cement stone. This number is generally around 30% of the cement amount by weight, depending on the type of cement and the environmental conditions. That means: 1,000 grams of cement require around 300 grams of water. If you use less, some of the cement will remain unhydrated and serve as an overpriced fine filler. If you use more, the extra water will create additional capillary porosity, reducing the final concrete’s strength and durability.

Okay, so we have the perfect sand-gravel blend, just the right amount of cement with the water content of about 30% of its weight. The best concrete we can make with the materials we have. Job well done, right? Not really. Try mixing, transporting, and compacting this concrete. No matter how good and optimised it appears to be on paper, this concrete will be almost completely dry, grainy, and incoherent; placing it into a mould using conventional techniques like vibration will be difficult, if not impossible. Sure, we can add more water to make it more liquid, but we already know that this reduces strength and durability. If only we had another option...

Making concrete recipes, concrete production and concrete workability and lifetime better

With plasticizing and superplasticizing admixtures from our Centrament, MC-TechniFlow, and MC-PowerFlow ranges, as well as compaction aiding admixtures from our Murasan Hydrotech range, you can balance the cost, performance, and workability of your concrete – in short, with our admixtures, your concrete can be adjusted to precisely the performance features you need. Do you require additional frost resistance? Perhaps you could make the concrete completely hydrophobic. How about giving yourself some extra workability time during the hot summer days, or accelerating cement hydration in the winter to increase production output? No worries, we have an admixture for that. And the best part? Having a solution from MC-Bauchemie involves more than just getting the admixture. You will also get the full support and knowhow of our experienced scientists, engineers and technicians, who can help your concrete reach its full potential as part of the package. It is essentially a win-win situation.