Is concrete a homogeneous mix

Frequently asked questions about concrete

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What does concrete mean in English, French, Italian or Spanish?

The English name for concrete is concrete. In French it is béton, in Italian it is calcestruzzo and in Spanish it is hormigón. By the way: If you click on one of the country flags in the moertelshop, you will find our entire range of goods for everything to do with concrete translated into each of these languages. Suggestions for corrections are of course always welcome.

Is concrete the same as cement?

No, cement is just one of the three main components of concrete. The other two are sand and water. For coarse-grained concrete, use gravel instead of sand. When the components are mixed together, a reaction begins between the water and the cement, at the end of which the liquid becomes a solid mass. The more cement the mix contains, the harder the concrete will be because the cement is the glue that holds everything together. Using more water than necessary will degrade the glue and result in poor quality concrete. The task of the sand or gravel is to keep the shrinkage of the concrete within limits, because it is the only component that does not shrink when the concrete hardens. Without it, the concrete would crack severely.


Frost - At what temperature can you still pour concrete?

If the ambient temperature is below 5 ° C, no more concrete should be poured. Frost damage is only to be feared from 0 ° C, but when it is very cold, the clock practically stops for the concrete and it only sets extremely slowly. If there is night frost before the concrete has achieved sufficient strength, then it can be damaged. Of course, small objects made of concrete are more at risk than large structures, because the heat generated by the setting inside the concrete dissipates more quickly. If you still want to pour concrete at low temperatures, you should use accelerated concrete so that the concrete clock stays in motion. In the Moertelshop there are mixes that can be modeled for this BUMS and WUTZ or the pourable mixes VITO, VITOTTO, MOBY FIX and TURBO 20. Of course, you can also accelerate normal concrete yourself, for example by adding our CSA cements CALUMEX WHITE and NEXT BASE or with our high-alumina cement CARO WHITE.

Which concrete do you use for handicrafts?

For crafting decorative objects, it is best to use fine-grained concrete with particularly high strength so that the pieces do not break so easily later. Because the hardware store mostly only sells handicraft concrete of poor quality and at very exorbitant prices, it is particularly worthwhile to stop by the Moertelshop. It depends entirely on the planned method of processing which mixture is best, because concrete can not only be poured, but also modeled, carved, kneaded or spread in thin layers. The perfect craft concrete for pouring VITOthat is available in gray or white. This means you have a finished result in your hands after an hour. If you like it a little slower when pouring, that's for you VITOTTO even better suited. On the other hand, it is completely different if you want to make small decorative pieces by modeling. For modeling is PLASTY FIX best for. For carving, however, you use it SCULPTINE, a very special mixture that first solidifies quickly, but then remains so soft for two days that you can scrape out any shape with a simple spoon. Finally, there remains the lamination. Therefore there is LAMBO. It is similar to kneading concrete, but it is much easier to spread. If you want to clad a balloon thinly with concrete, e.g. for a lantern, you should use LAMBO, which is also available in gray or white.

How do you make lamps or lights out of concrete?

Fantastic lamps and lampshades can be made from the modern, high-strength types of concrete for artists and designers, because they can be processed with very thin walls due to their enormous strength. Depending on the working technique (casting, modeling or lamination) are suitable for this VITO, PLASTY FIX or LAMBO. There are DIY instructions by the designer Torsten Stephan for one of 1000 possible models on video here.

Concrete look - How can I design the floor, kitchen, table, bathroom and furniture with a concrete look?

For the reproduction or imitation of concrete surfaces (concrete optics), special concrete can be applied in very thin layers on a given substrate, e.g. B. made of wood. For floors and table tops, our self-leveling concrete floor is best for this BASIL. It has the particular advantage that it sets without shrinkage and therefore cannot tear. Wooden substrates become thin beforehand KLEMO leveled over so that the concrete adheres well to the wood. Joints in the wood can be opened by an inlaid Mesh fabricbridge. It is best to use for walls and vertical surfaces MARFINO, a cement-based wall paint that can be painted or trowelled.

How to mix concrete correctly - agitator, mixer or compulsory mixer?

There are very different types of concrete that have to be mixed differently. The simplest is probably the ready-mixed concrete, which gets by without mixing, such as Setz-Fix from Sakret or Ruck-Zuck-Beton from Quick-Mix. You fill it in, pour water over it and that's it. This of course results in a very poor quality concrete, but for some tasks that is enough. The classic building concrete, on the other hand, is mixed in the vat with an agitator (this is a strong whisk) or in the mixing drum. In the vat you should first premix the dry ingredients and then add the water. In the drum mixer, on the other hand, you usually start with the water and then add sand, gravel and cement. The most complex is the mixing of high-strength concrete such as MOBY DURthat you need for special purposes like concrete kitchen countertops. Because you have to get by with extremely little water here, you need one Compulsory mixer and at least 5 minutes mixing time. However, if necessary, you can also use a normal free-fall mixer, like this one Video will be shown.

Do you have to shake concrete to compact it?

Yes, you can, but there are also more elegant methods. In construction, it is common practice to vibrate the concrete with a vibrator or external vibrator, which causes the concrete to collapse and become denser. As soon as the vibrator is switched on, the concrete mass flows into the mold, and when you switch off, the concrete stops again. The sand and gravel grains in the concrete sit closer together after compaction, which significantly improves the final strength. With the help of modern superplasticizers like ours FLUP-PCE-104 (powder) or ours FLUP-PCE-375 (liquid) Concrete can also be made to run into the mold by itself and compact. One speaks then of self-compacting concrete (SCC), for which no shaking or vibrating is necessary. Whether the concrete actually flows like honey also depends on the fine powder content of the concrete grain. That is why there is always in a good SVB recipe Marble powder, Microsilica, Metakaolin or something similar as a filler.

Which concrete for tabletops?

For a concrete table or a table tennis table made of concrete, you cannot use any concrete, because it would be much too heavy and thick. Something like this is best made from high-strength concrete, because then you can get by with very thin walls. This saves weight, looks more elegant and also has the advantage that high-strength concrete also enables very good, smooth and pore-free surfaces. A grouting concrete based on the special cement specially developed for furniture and accessories made of concrete Dyckerhoff FLOWSTONE® is our MOBY DUR, which it is called MOBY DUR® white or as MOBY DUR® gray gives. So that everything goes well during processing, you should definitely first use the Flowstone manual have read that in the Moertelshop also as free Download is available. Watching our video is also very helpful Mixing instructions Flowstone.

Why and for how long does concrete have to be post-treated?

After concreting, you should cover your work with foil to keep it moist. This is called the aftercare. If it is forgotten, the concrete surface may dry out too quickly and then crack or chalk. How long the film has to stay on depends on the environment. Usually, the concrete is out of the woods after a day and the foil can be removed again. But if the sun or wind allow it to dry excessively, the film is better left on for a day longer. Anyone who concretes in a draft-free and shady room has less to worry about there than outside. When it is very cold, everything goes much slower with concrete, and the film should stay on it accordingly longer in winter. Of course, you can also keep concrete moist by watering it with a spray mist, e.g. for large areas such as a freshly concreted screed, for which you may not have a sufficiently large film.

When can concrete be loaded / walked on?

A completely normal concrete can usually be loaded or walked on after just one day at room temperature. In the next few days, of course, its firmness will continue to increase, which is why it is better to wait a little longer before subjecting it to greater loads. But you don't have to wait 28 days, as is sometimes wrongly assumed. This is just the time that a test laboratory waits before it can determine the so-called final strength, because after that the strength in the concrete hardly increases any further. As a precaution, a fragile workpiece such as a kitchen worktop with a recess should not be removed from the mold or turned over until two or three days after casting. With a more compact piece, on the other hand, such as a bust, where nothing can break off so easily, you don't have to wait that long. If you are with accelerator or works at high temperatures, the waiting time is shortened, and at very cold temperatures it can sometimes take a long time before the concrete can be loaded.


Concrete too fast - what to do?

Some precast concrete mixes are set so that they set very quickly, such as STONE CAST or VITO flash concrete. If you don't do everything right, it can happen that the mass reacts too quickly and already hardens in the mixing vessel. You have to know that such masses get even faster if it is very warm or if you use too little water. You can easily help yourself against the heat by using particularly cold food in summer and storing the dry mortar in a cool place, in the refrigerator if necessary. A cause that is sometimes difficult to identify for solidifying too quickly is too little water. Here you should not rely on your sense of proportion, but rather work with a scale or a measuring cup in order to correctly measure the portions according to the instructions on the packaging before the mixing process. Then water and dry matter are combined in a suitable mixing vessel and mixed with a suitable mixing tool. That sounds easy, and it is. Nevertheless, here are a few examples of possible errors:

Case 1) Peter only ever needs small amounts, which he stirs in a drinking cup. To do this, he puts dry matter in the beaker, takes it to the tap and adds water in small portions, stirs and adds water again until the mixture is as it should be. He goes back to work and before he can pour the mass has already set. ERROR here: Peter started the mixing process with too little water and only gradually added more water. As a result, the concrete sets faster than usual at the beginning. In addition, more time passes than necessary when readjusting the amount of water, and with each new stirring, heat is brought back into the concrete, which additionally accelerates the setting process.

Case 2) Hannah has misplaced her mixing tools and has to improvise. She takes a tablespoon and a salad bowl from the kitchen and begins to work through the mixture. Before you have finished mixing, the concrete has already set. ERROR here: Hannah's tool is so unsuitable that it takes her a much longer time to mix than usual. During this time, the hydration of the cement begins, and since there are areas in the bowl that are not yet homogeneously mixed with water, areas that are even drier than others, the setting process proceeds particularly quickly here. The solidification then spreads from there to the whole mass.

Case 3) Willi has a small mixer with a timer that he uses to mix his concrete. Usually his mixes are perfect after 3 minutes of mixing. That is why he always leaves his watch set to 3 minutes. With his new, accelerated mix, however, he found that the concrete was solidifying in the mixing vessel shortly after the mixer was switched off. ERROR here: The mixing time is too long. So Willi mixed more than necessary, which artificially fueled the setting process, because the mixing creates frictional heat and heat accelerates the process.

Case 4) Susanne makes small cubes out of lightning concrete that sell well. That is why she is investing in a larger mixer so that she can pour 100 cubes at once instead of the previous 3. Experience has shown that she usually has 5 to 8 minutes to pour, which would be enough for 100 cubes. But the larger portion of now 25 kg, which she mixed all at once, becomes solid after a minute, so that it does not even have to be poured. ERROR here: Large portions behave differently than small ones because the hydration that occurs in the concrete creates heat. The heat cannot escape to the outside in large portions as easily as in small ones. As a result, the temperature inside rises, which additionally accelerates the setting process.