When renovating a circular system in Dingolfing, the responsible district office decided to use a concrete roadway. A climate-friendly road surface cement CEM II / A-LL 42.5 N with a lower proportion of clinker from HeidelbergCement was successfully used for the first time. This meets all the requirements of ZTV Beton and can be used without restriction in concrete road construction.
Roundabouts can significantly increase traffic safety and improve the flow of traffic. Not far from the A92 Dingolfing West motorway exit, a roundabout opens up the adjacent industrial area and forms the entrance to the BMW Group plant in Dingolfing. The downstream distributor is enormously burdened by the heavy traffic. In the current planning, the highest load class BK 100 was tendered with a view to further development. The old asphalt roundabout had already been repaired several times. "There were both deformations and cracks through all the asphalt layers," says Manuel Stanzel from the civil engineering department of the responsible district office in Dingolfing-Landau. "The increased expenditure for maintenance as well as the immensely high numbers of heavy vehicles led us to the decision, to build a concrete roundabout". Good experiences with other concrete gyroscopes had encouraged the client to make this decision. Nationwide, over 160 concrete roundabouts have been built in excellent quality in the last 10 years. These experiences flowed into the planning.
Careful planning of a concrete pavement
Roundabouts are more heavily used than other traffic routes. Shear stresses from driving in tight radii as well as braking and acceleration processes occur in the roadway. This enormous stress from the axle loads of the trucks and from thrust can be absorbed particularly well by thick concrete slabs. This construction requires careful planning. This was transferred to the OBW engineering company, Landau an der Isar. Additional fibre reinforcement and, if necessary, steel inserts increase the security against deformation and cracking. Based on the expected stress and the specifications according to ‘Guidelines for the standardisation of the superstructure of traffic areas’, RStO, the commissioned engineers designed the road structure and the plate thickness.
Construction of a permanent concrete top
The new concrete pavement was installed with a thickness of 30 cm on an asphalt base course and segmented by means of doweled transverse joints. The arrangement of expansion and compression joints resulted from the planning. In principle, the shape and dimensions of the concrete slabs for roundabouts may require reinforcement of the concrete. In the Dingolfing roundabout, areas of the adjoining entrances and exits were reinforced with welded wire mesh. A specially developed slipform paver can be used for paving concrete in roundabouts. Alternatively, the construction workers in Dingolfing installed around 550 m3 of concrete ‘by hand’ with so-called ‘vibrating planks’ between formwork. The work was carried out by Berger Bau Passau on behalf of STRABAG AG.
Special cement for sustainable traffic route construction
After the work has been completed, the roundabout will be presented in a particularly light shade. The roadworthy colouring is also due to the use of a special road surface cement. For the construction project in Dingolfing, the Burglengenfeld plant of HeidelbergCement AG developed its own road surface cement CEM II / A-LL 42.5 N, which meets the requirements of ZTV Beton and can be used without restriction in concrete road construction. In this project, this cement was tested for the first time and finally rated very positively by the client and the construction companies. The concrete using the selected Portland limestone cement was easy to work with and achieved a particularly good surface seal. Its particularly dense concrete ceiling offers great advantages in terms of the desired durability. With its low proportion of alkalis, the cement used guarantees that alkali-silica reactions - i.e. concrete damage - do not occur. Compared to conventional pavement cements based on Portland cement, Portland limestone cement CEM II / A -LL42.5N has a lower proportion of clinker and is therefore more climate-friendly. In the production of the CEM II cements, comparatively less CO2 is released. This cement therefore supports the efforts of the cement industry to sustainably reduce CO2 emissions over the next few years. Overall, everyone involved benefits from this newly developed building material: Builder and user benefit from a permanent and safe traffic system, and the construction company benefit from good processing properties of the building material concrete. Last but not least, the special road surface cement makes a noticeable contribution to climate protection.
Read the article online at: https://www.worldcement.com/europe-cis/17092021/heidelbergcement-renovates-roundabout-in-dingolfing-with-a-new-concrete-lane/