Many local governments are looking for ways to reduce the costs of building asphalt roads. The feasibility of using foam concrete in such projects has been confirmed by tests on the pavement of a test section, where the base layer consists of foam concrete and the wearing/closing layer is made using surface treatment technology (double). The tests were conducted by scientists from the Poznań University of Technology.
Affordable Local Roads
The rise in prices affects both retail consumers and municipal governments equally, prompting contractors to seek cost-saving measures. This also applies to the construction of asphalt roads. How can these costs be reduced? An interesting alternative is the construction of a semi-rigid road structure using foam concrete. In such a setup, a layer of PB 1000 foam concrete (bulk density 1000 kg/m³ ± 10%) with a thickness of 15 cm to 20 cm and a wearing/closing layer is used. For soil groups with bearing capacity G2 – G4, an additional reinforcing layer of PB 600 foam concrete (bulk density 600 kg/m³ ± 10%) with a thickness of 10 – 30 cm is also applied.
Foam Concrete – Lower Cost than Asphalt Road Construction
Foam concrete is a fluid building material produced using a special foam concrete production machine on the construction site and applied immediately in the target location. Due to its high fluidity, it precisely fills all irregularities and gaps, eliminating the need for leveling the substrate with heavy equipment (graders, rollers). This allows for faster progress and cost savings compared to traditional asphalt road construction methods. Local roads with sporadic traffic load (≤ KR1) can have a closing layer made using surface treatment technology, resulting in further savings. In this case, the surface layer should be sprayed with a fast-breaking asphalt emulsion, with or without polymers, and then fine aggregate and gravel should be spread and rolled. The load-bearing capacity of such a pavement structure is ensured by one or several layers of foam concrete base (the thickness of the foam concrete layers depends on the soil and water conditions: for G1 soil, it will be 15 cm, for G4 soil – a maximum of 50 cm). Compared to standard solutions and the costs of traditional asphalt road construction, this solution is a very attractive alternative in terms of price.
Tests in Greater Poland
Tests of the semi-rigid pavement structure were conducted on a residential road in Greater Poland. Researchers used the ZiSPON device (Integrated System for Precise Pavement Assessment), including the UGN module (dynamic deflection measurement corresponding to FWD device measurement). After assessing the bearing capacity of the substrate, a 20 cm layer of PB 1000 foam concrete was poured, in which micro-milling was performed one week after application. This provided a surface with greater roughness. Then, a double surface treatment layer (asphalt emulsion + rolling of aggregate) was applied.
In the next stage, the pavement bearing capacity was assessed, and dynamic deflection measurements using the ZiSPON device were performed 14 days after the foam concrete base construction and 7 days after the test section was put into operation. The conducted tests confirmed that the constructed pavement achieves bearing capacity for the KR1 traffic category.
Foam Concrete for Local Roads
Lower cost than asphalt road construction, simple and quick execution, and the possibility of strengthening the structure by applying mineral-asphalt mixture layers without interfering with the base layer (in case of increased traffic) – these are just a few advantages that make semi-rigid constructions an excellent solution for municipal roads. This makes them an attractive and cost-effective alternative to standard solutions, solving the problem of building hardened pavements.
Source:
Dr. Eng. Marcin Bilski
Dr. Eng. Andrzej Pożarycki
Dr. Eng. Przemysław Górnaś
Poznań University of Technology