Finnfoam INFRA panel provides a patented solution for pedestrian and bicycle ways and roadways rated for lower speeds

At Finnfoam, we explored the development potential of road structures with light traffic. The current founding methods are burdensome and expensive, and the results are rarely long-lasting if the subgrade has a low bearing capacity, which means that the surfacing may already begin to crack after couple of years due to freezing. As a result of the project, we patented the Finnfoam INFRA panel designed for earthwork applications, which is reinforced on both sides with mortar and fiberglass mesh, i.e. almost exactly the same structure as used by​​​​​​Tulppa.

The operating principle of the mortar coated Finnfoam INFRA panel is based on its significantly higher bearing capacity compared to standard Finnfoam. This allows you to create a distributive layer on top of foundation soil with a low bearing capacity. This solution can be used to provide significant savings in foundation costs, as a road or sidewalk can be founded without extensive replacement/stabilization of soil. Standard Finnfoam can also be used to significantly reduce the replacement of soil, but this solution will provide even more benefits.

The size of the Finnfoam INFRA panel is 600 x 2,600 mm and the panels are available with a thickness of 50 mm. If the site requires thicker insulation for frost protection, this can be achieved by using standard Finnfoam panels in addition to the INFRA panels. The overall thickness of insulation is chosen according to the number of chilling hours in the area and the installation depth as per the standard procedure for designing frost protection. The short-term compressive strength of the panels is ≥ 400 kPa and the long-term compressive strength is ≥ 180 kPa. The modulus of elasticity of the Finnfoam INFRA panels is ≥ 19,000 kPa and bending strength at 50 mm ≥ 1,200 kPa.

The operating principle of the solution is that a thin layer of sand cushion is spread on top of the leveled foundation soil. The Finnfoam INFRA panels are easy to install on top of the smooth sand base. The surfacing on top of the panels consists of 150–300 mm of crushed aggregate and asphalt or some other similar surfacing. This structure is also suitable for founding larger roadways, but in that case the solution provides lesser benefits, as this type of application requires a crushed aggregate layer of 500–700 mm on top of the insulation. This is done to ensure that the surface temperature of the road does not change too quickly, which might lead to a slippery surface due to hoar frost. The solution has already been used in a number of test sites, from which the feedback and results have been very positive.

In the summer of 2014, a stretch of pedestrian and bicycle way measuring little over 200 meters was constructed for testing purposes in Pori, where the solution was discovered to provide savings on the founding costs. In addition, long-term testing has found that the structure functions as designed. Over a couple of years, the expansion and contraction of the structure has remained within ±1 mm. An equivalent control section of road was founded using traditional methods requiring significant replacement of soil.