Introduce and adapt the source mortar ahead of time

The special property of swelling mortar is its volume expansion during drying and setting. Of course, the desired effect must be calculated in order not to provoke pressure build-up in closed cavities until it bursts and explodes. In case of doubt, inspection openings are important, which are subsequently closed.

Sources create pressure and closure

Grout mortar is often to fill cavities evenly and completely. He is often injected with syringes. If properly processed according to manufacturer's instructions, its volume increases during setting by up to ten percent.

When filling cavities and holes, there are two challenges:

1. The setting process must be possible by evaporation of water
2. The growing volume must fit into the cavity

If introduced source mortar sets and increases its volume, this process can close the air access or the evaporation channel. In the worst case, the setting process eventually stops and the mortar remains soft.

In limited space conditions, the swelling process creates pressure on the inner walls of holes and cavities. If there is no way to reduce pressure, the pressure is increasingly applied to the inner walls and can lead to the demolition of concrete and stones.

Create inspection openings

Open surfaces and joints can easily be filled with swelling mortar. If holes and cavities are filled, mortar leakage should be at least 10 percent of the total surface area. The ten percent refer to the expansion surfaces in all directions.

Drill holes can serve as inspection openings. Three to four openings should be made in at least two different directions per cubic decimeter of source mortar. The recommended diameter is holes with a diameter of at least eight millimeters.

Dispose of water and swelling

When introducing swelling mortar, watering of the interior walls is helpful in order to support a homogeneous fit of the filling material in the cavity or hole. The inspection openings should also be watered.

Any swollen mortar should be removed immediately. A small chisel can serve well as a "skimmer" and be used as a scratching tool at the beginning of hardening.

Tips & Tricks

If you put long nails into the drilled inspection openings, you can follow the degree of swelling of your entry and, by pulling it out, you can provide further setting and rehydration with rewashing.

Artikelbild: Miriam Doerr Martin Frommherz / Shutterstock

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