Mechanical properties of URETEK expansion resin

For all URETEK expansion resins, the mechanical properties increase as the density of the expanded material increases. The density of our material is highly dependent on the resistance it encounters during expansion. When applied beneath floors and structures using the URETEK FloorLift® method, the bulk density varies from 70 kg/m³ to 120 kg/m³. When injected into the ground using the URETEK DeepInjection® method, this ranges from 150 kg/m³ to 300 kg/m³. Unlike other injection materials – often around 800–1,500 kg/m³ – our expansion resin therefore adds minimal weight to the subsoil. This is an ideal property for use in soil layers with poor bearing capacity.

Within certain limits, URETEK expansion resin exhibits elastic properties: if a force is applied to the material, it will settle in a manner linearly proportional to the force applied. Once the pressure is removed, the material returns to its original shape. Only under extremely high loads, where the compression (set) exceeds 10 per cent, will the internal cell structure become permanently deformed. The material will then no longer return to its original shape.

Test diagrams

The test data shown in the diagrams have been determined in accordance with the American standard ASTM. The diagrams relate, in turn, to compressive strength and shear strength. The horizontal axis shows the bulk density of the test specimens, whilst the vertical axis shows the strength values. The range within which the densities of the expanded URETEK material fall is shaded in yellow in all diagrams.

As the URETEK expansion resin is primarily used for soil consolidation and for raising subsided structural elements, it is clear that, from a practical point of view, the most important property is compressive strength. It can be deduced from the compressive strength graph that, at a density of 96 kg/m³, the compressive strength is 3.2 kg/cm² = 32,000 kg/m² = 0.32 N/mm².

By way of illustration: for domestic floors, a live load of 150 to 200 kg/m² is assumed, whilst for factory and warehouse floors, a live load of 5,000 kg/m² is considered extremely high.

Resistance to ageing

The certificate for the URETEK expansion resin was issued by the Department of Materials Research at the University of Hanover. A long-term evaluation of a high-density polyurethane group, E165 – Caradate 30, indicates a long-term design life of at least 33 years. Ongoing research points to an extended design life that far exceeds this period. This is also the usual outcome of studies carried out by both independent parties and major raw material suppliers. These point to long-term stability and durability, even in adverse environments.

Thermal stability

The University of Hanover has carried out a quantitative assessment of thermal stability in the form of dynamic weight loss using differential thermal analysis. It can be expected that the service life of composite pipes containing E165-Caradate 50 rigid foam, and tested in accordance with the research report, will be 30 years at a continuous permissible temperature of 133˚C.