Asphalt, the predominant surface layer in road construction, is also frequently used as a paving material in car parks and underground garages. The driveable surfaces have to withstand particular stresses: e.g., due to the influence of moisture or mechanical abrasion. De-icing salts carried in from the street are particularly dangerous. Good grip is also especially important in the entry and exit areas or on the narrow and steep ramps.
In the new underground garage in Rottenburg an der Laaber, a 10 cm thick bearing course (AC 32) now serves as a stable base. It transfers all traffic loads to the substrate – concrete in this case. A 4 cm thick asphalt surface course (AC 8) is responsible for the required surface properties of the traffic area.
A total area of 3,200 m2 was to be asphalted, and an evenness of ± 6 mm was specified. The paving work was carried out by Strabit Straßen- und Bitumenbau GmbH & Co. KG from Wörth an der Isar, 30 kilometres away. The traditional Lower-Bavarian company specialises in road and asphalt construction, earthworks, sewer engineering, and the construction of industrial outdoor facilities, and has worked closely with local authorities, general contractors and engineering firms for many years.
Asphalt and road construction is one of Strabit's key business areas. With a modern fleet of vehicles, a dynamic team consisting of highly trained employees, experienced construction draughters, supervisors, machinists and road-building specialists, the company handles numerous projects - both regionally and nationally.
The specification for the asphalt paving was: The number of cold seams must be kept to a minimum! This makes the asphalt surface more resistant and longer lasting.Because any subsequent crack in the asphalt can pose a risk. In winter, parked vehicles carry in water contaminated with de-icing salt. The dissolved salt can cause considerable corrosion damage to the reinforcement in the concrete. This is usually not immediately visible. Repair work is complex and costly. On top of that, there is a loss of revenue due to a partial or even full closure of the managed parking area.
Paving should ideally be carried out "hot to hot". The asphalt mix therefore needs to be applied by at least two offset pavers. This reduces the number of contact surfaces that cool down quickly. The lanes should form as compact a structure as possible. However, given the confined space and on a parking deck with a clear ceiling height of only 2.40 m, only light and compact pavers can be used. They should then be particularly efficient.
With a weight of less than 6 t, a machine height of 2 m and a screed width of just 1.1 m, the BOMAG compact paver fits through and in almost anywhere. Even behind the rows of pillars and right up to the wall, it was fully operational during the car park expansion works in Rottenburg. Manual paving was only necessary on very few and particularly angular sections.
With the BF 200 C-2, Strabit Straßen- und Bitumenbau GmbH & Co. KG has the perfect asphalt paver in its fleet for the confined conditions in multi-storey car parks. The second paver was rented in order to be able to perform the "hot to hot" paving method here.
It combines compact dimensions with a 2-platform concept and maximum all-round visibility. The operating panel is height-adjustable and equipped with a display for controlling the paving functions. Due to the low ceiling height, the machine operator often selected the low standing position during paving. Even from there, a viewing tunnel in the hopper wall always provided a clear view of the direction rod when manoeuvring. The SIDEVIEW system and dual screed controls (right and left) offered an additional plus in ergonomics. This increased working comfort also resulted in even better work results here. Even under very low ceilings, paving was a breeze, as the BF 200 C-2's light towers can be folded by 90°.
The paving crew also benefited from BOMAG ECOMODE. The BF 200 C-2 only ever draws on the power that is actually required. Its clever engine and hydraulics management regulates this fully automatically. This results in lower overall engine speeds, reduced fuel consumption, and, ultimately, lower exhaust and noise emissions.
Although high temperatures are essential in asphalt paving, the screed heating system didn't run for a minute longer than necessary. Equipped with advanced MAGMALIFE screed technology, the BOMAG BF 200 C-2 can achieve the best paving results immediately. The heating rods are cast in an aluminium block. The excellent thermal conductivity of the aluminium enables a significantly shorter heat-up time. As a result, the paver and crew were ready for action even faster.
The BF 200 C-2 ensured the paving team achieved the best results. Always supported by the latest BOMAG screed technology: a clever combination of screed plate vibration and tamper frequency.
A decisive factor in maintaining the required evenness (in this case ± 6 mm) was the most even possible material feed in front of the screed. The BF 200 C-2's cleverly dimensioned auger distributed the material perfectly over the entire screed width. In Rottenburg, the powerful hydraulic drives still had ample reserves and always remained finely adjustable.
And should more space occasionally be available for surfacing, widening the screed is also no problem, thanks to the modular extension concept.
One challenge, however, was to continuously feed the pavers with asphalt mix. The asphalt had to be delivered with a total of three fully insulated asphalt tippers and was then transported by wheel loader to the underground car park for feeding. The construction time for the bearing course was 4 days. After another 6 days, the surface course was also completed.