Use precast concrete correctly

Ready-mixed concrete offers some valuable advantages: the quality of the concrete can be guaranteed, no mistakes can be made when preparing the mixture, and ready-mixed concrete can be stored for a very long time and is still available quickly. But what is essential: precast concrete must be processed correctly. This article explains how to do this.

Mix ready-mixed concrete

Ready-mixed concrete (€ 15.69 at Amazon *) is what the name suggests: ready. To make it into concrete that can be built in, all you have to do is add water. In conjunction with the right amount of water, the concrete receives exactly the properties and strength that is guaranteed by the manufacturer.

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Amount of water

The amount of water that is added to the concrete must correspond as precisely as possible to what the manufacturer requires. This is about the so-called water-cement value - i.e. the ratio between water and cement. It is crucial for the strength of the concrete and for some other properties.

In general, concrete is always mixed when it is earth-moist. If too much water is added, the concrete can no longer maintain its full strength.

If there is not enough water, or if the temperature is very hot in summer, when the added water evaporates, the concrete cannot set properly. The result is a crumbly mass that can no longer set and falls apart. In the summer when it is very hot you should

  • add a little more water (be careful, because too much water is also bad)
  • Cover the mixed concrete as much as possible and
  • re-moisten if necessary

The right mixing

If concrete is not mixed in a mixer, but by hand, care must be taken to mix it correctly:

Dry the concrete (!) pour into a suitable container that is as large as possible. Exercise caution and do not inhale the concrete dust, as it is poisonous. Pour in the water by the liter and stir with the flat shovel in between. Pierce the concrete mass with the upturned shovel, push a small pile towards the front and smooth it back again. Repeat this in as many places as possible in the concrete tub. Occasionally poke the pile from below with the shovel and turn all of the concrete mixture over. Repeat several times until the entire water is picked up, then pour a liter of water again.

This process costs time and power, but is the only way to produce a uniform mixture manually.