Wet sprayed mortar was used during the renovation of three parking garages in the canton of Bern, covering a total area of approximately 2,200 m². The reason for this was the existing concrete structure. The first and second reinforcement layers did not always have the required concrete coverage. To ensure this was restored, the existing layer at the ceiling level had to be removed first and then a new mortar layer had to be applied.
Our work included not only the installation of the sprayed concrete. The preparation of the existing concrete was crucial, as the new structure had to be permanently connected to the existing structure.
From stock to workable concrete
The ceilings of the adjustment halls contained existing layer panels with a thickness of about 35 millimeters. These were removed using high-pressure water jets.
The team worked with a water pressure of around 2,500 bar. The removal process also had the task of creating a sufficiently rough concrete surface for the subsequent wet-sprayed mortar.
This preparation is crucial for the further construction process. According to the product data sheet, the substrate must be free of loose components and impurities and have a suitable surface roughness to allow the concrete replacement to bond with the existing concrete.
After the removal of the old coating, the new covering of the existing reinforcement could be installed.
Up to 30 millimeters of wet spray mortar over the head
A polymer-modified wet-spraying mortar was used, which meets the requirements of the R4 class according to EN 1504-3.
The three sub-areas differed slightly in area, layer thickness and material quantity.
In part 1, approximately 730 m² were processed. Here, the mortar was installed with a thickness of approximately 30 millimeters. For this, approximately 46 tons of material were needed.
The 2nd sub-section covered an area of approximately 760 m². With a layer thickness of approximately 25 millimeters, approximately 50 tons were processed.
Another approximately 730 m² followed in part area 3. Here too, the layer thickness was approximately 25 millimeters. The material consumption was approximately 46 tons.
Approximately 142 tons of wet-sprayed mortar were processed across all three sub-areas.
142 tons of material from the silo
With such quantities, the material delivery on site also plays an important role. Instead of sacks or big bags, the sprayed mortar was therefore processed using a silo pump.
This was particularly helpful due to the tight space conditions on the construction site. Storage and installation areas were only available in limited quantities.
The use of machinery reduced the labor required for material delivery. At the same time, less packaging and material handling was required. This also reduced material losses.
For the installation itself, the processing from the silo offers another advantage: The wet sprayed mortar is continuously supplied for application. With a total of 142 tons of material, this is a significant part of the construction site workflow.
More about the area below Building reconstruction
Wet spray mortar under winter conditions
An additional challenge was the season. The mortar used must be processed at temperatures between 5 and 30 degrees Celsius, according to product specifications.
In order to ensure that these conditions were met during the work, the assembly halls had to be partially heated. Depending on the situation, additional ventilation measures were also used to regulate the temperature and humidity within the halls.
Especially with a large ceiling area, this directly affects the construction site organization. Materials, the subfloor, and the surroundings must remain within the specified conditions during processing.
More protection for the existing reinforcement
With the new wet-sprayed mortar, the required concrete cover of the existing reinforcement was restored. As a result, the reinforcement is located deeper within the concrete structure and receives better protection against corrosion.
At the same time, the new construction of the renovation serves to strengthen the existing ceilings and helps to preserve the concrete structure in the long term.
In this project, the large quantities ended up being placed over the heads: around 2’200 m² of ceiling area, up to 30 millimeters of new construction, and a total of about 142 tons of sprayed concrete.
