Heavy loads that are present on airfields aprons, on storage areas at industry facilities and on road sections such as bus lanes and bus terminals need pavement materials that are rutting resistant and have a high stiffness modulus, even at low loading frequencies. The traditional selection of materials in these areas has been rigid pavement structures such as cement concrete. However, more flexible materials that can obtain stand deformations without cracking and without joints, both leading to lower maintenance costs, has been asked for. This has resulted in the development of a semi-flexible material for heavy-duty areas. The semi-flexible pavement material described in this paper consists of an open asphalt structure (5/8, 8/11 mm or 11/16 mm aggregates) where a high strength micro silica mortar is penetrated into the air voids (25 - 30 %) of the asphalt mixture. The results are based on the special type of semi-flexible material called Densiphalt. The semi-flexible pavement combines the micro silica mortar's strength and the asphalt material's flexibility. The special designed micro silica mortar from Densit A/S has the ability to penetrate entirely into the open asphalt structure, thus ensuring a homogeneous pavement material. The design stiffness modulus of the semi-flexible pavement has been determined to 8,000 MPa at 25 .C and loading frequency of 33 Hz, 2-3 times higher than for asphalt. The service life of the pavement materials is 15 to 20 years. The material can be constructed in different colours through additives added to the mortar. The finished surface of the material has different appearance depending on the use and requirements to e.g. the friction. In resent years, the construction of Densiphalt has been further improved by introducing steel reinforcement at the bottom of the layer. Semi-flexible pavement materials are normally constructed in thicknesses between 40 and 100 mm depending on the load applied on the areas. The steel reinforcement has shown to further improve the rutting resistance and thus enables the use on areas with traditional asphalt layers that need partial repairs. Furthermore, the short curing time of the pavement (between 24 and 48 hours, depending on the air temperature) makes the materials an excellent choice in areas where the time of repair shall be as short as possible. Semi-flexible pavements have, with excellent results been used for approximately 10-15 years around the world on aprons in airports, storage areas in ports and industrial facilities plus at bus terminals. For the covering abstract see ITRD E135448.
Abstract