Concrete on concrete: use cement water as a primer

So-called cement water, cement slurry or cement glue can be used to securely bond old and fresh concrete. We show how the primer can be produced.

Possible applications

The cement adhesive can be used, for example, when an old concrete surface is to be renovated. If this shows cracks, if it has become unsightly or uneven over time, a new layer can solve the problem and can be used for leveling.

But it is also possible, for example:

• to create a necessary gradient
• Raising walls
• Compensate for damage
• Thicken walls

preparation

Before the cement adhesive and a new concrete layer are applied, the hardened concrete must first be suitably prepared. To do this, the following steps are required:

Dry cleaning

Coarse and dry dirt can be removed with a broom with hard bristles. Moss and other deposits should also be removed by scraping or brushing them off the joints and stones.

Wet cleaning

Since not all dirt is removed with dry cleaning

the hardened concrete should then be cleaned with a damp cloth. In the case of stubborn dirt, it is advisable to soak the surface beforehand with a mixture of soda and warm water. Afterwards, moss and other residues can be removed with a brush.

Alternatively, a high-pressure cleaner can also be used.

Fix damage

If there are cracks or holes in the hardened concrete, they must be cleaned and fragments removed before the cement water is applied.

let dry

Before the primer is distributed, the concrete must be allowed to dry completely. It therefore makes sense to carry out the preparatory measures on a dry and sunny day and dry the concrete for at least several hours, or better overnight or for a day permit.

Tip: In order to protect the cleaned hardened concrete from renewed soiling and moisture before it is applied, waterproof tarpaulins can be stretched over it. However, they should not lie directly on the surface so that the surface can dry completely and undisturbed.

Make cement water

The production of the cement water is very simple and requires few accessories and only two means - water and cement.

The following are also necessary:

• a bucket or a mason's soup
• a drill with a mixer or another utensil for stirring
• a shovel
• a piassava broom
• if necessary a measuring cup

instructions

1. Measure out the water and put it in a bucket or masonry soup.
2. Add cement powder to the water while stirring to prevent lumps from forming. A scoop of cement is placed in ten liters of water.
3. Stir the mixture until the dry powder is evenly distributed and a homogeneous solution is formed.
4. Mix the fresh cement so that it can be distributed immediately after the cement water has been applied.
5. Spread the primer on the concrete surface and work in with a broom.
6. Apply the cement directly afterwards on the primer, distribute it evenly and smooth it.

Now the fresh concrete only has to dry completely until it can be walked on or driven on. Depending on the thickness of the layer, temperature and humidity, this can take a few days. Until then, the newly concreted area should be cordoned off and, if possible, covered with tarpaulin.

Tip: It is ideal if the work is carried out by two people. This makes it possible to prepare the cement paste and the cement itself at the same time and to distribute them promptly on the floor.

Alternatives

There are other alternatives to cement paste

Means with which hardened concrete and fresh concrete can be connected to one another. Including:

• Primer
• Reinforcement bars
• Turnbuckles

The advantage of an adhesive primer is that it is usually not necessary to mix it. This makes it quick and easy to use. The disadvantage is that the products are usually more expensive than making cement water yourself. However, the areas of application are the same for both remedies.

Reinforcement bars are pieces of metal that are half inserted into the existing concrete. To do this, holes must first be pre-drilled. The second half of the reinforcement bars protrudes and thus serves as a holder for the fresh concrete. In addition to the rebar, cement water or an adhesive primer can be used. That increases the liability. The plug-in connections can be used primarily for elevations or extensions of a wall, but also for the construction of foundations.

Turnbuckles are the means of choice for finished concrete parts that are to be brought together. They are similar to the reinforcement bars, but consist of two parts that are brought together and screwed together. As a result, a recess must remain in the concrete parts, which may already be available for some items in the trade but usually have to be made by yourself. The advantage is that finished concrete parts can be easily connected to one another. However, the effort is greater for parts that have not yet been provided with recesses. In addition, the costs are greater than for the production of the cement water. However, walls can be erected very quickly with this method and connection technology. In addition, the technology is suitable for any area in which concrete cannot be poured and no primer is required.