Reinforced asphalt has proven its worth: over the past 40 years, the HaTelit asphalt interlayer developed by the HUESKER Group has delivered convincing solutions on numerous pavement rehabilitation projects, not only in Germany, but also in other countries worldwide. Moreover, HaTelit is a preferred option for runway repairs as it lengthens maintenance intervals, reduces maintenance effort and cost, and causes less disruption to flight operations. Use of the alternative sustainable repair methods made possible by the innovative material offers a real possibility of reducing both traffic congestion and the rehabilitation backlog in Germany and elsewhere.
The widespread incidence of potholes, cracking and deformation is already stretching many parts of Germany's transport infrastructure to its limits. There is an enormous rehabilitation backlog for local roads, trunk roads and motorways alike. As a company that focuses on delivering sustainable technical textile solutions, the Gescher-based HUESKER Group developed an innovative material several years ago to overcome this problem. The HaTelit textile asphalt interlayer offers a fast, durable and cost-effective means of road repair. Engineer Dipl.-Ing. Andreas Elsing, Head of Product Management at HUESKER, sums up the benefits of HaTelit in road rehabilitation: "HaTelit asphalt reinforcement brings an up to fourfold retardation of reflective cracking, lengthens the service life of repaired pavements and thus extends the necessary maintenance intervals – all of which, of course, cuts costs."
Reinforcement tailored to specific requirements
Reflective cracking is one of the most common types of failure in asphalt road construction. Exposure to traffic loads, daily freeze-thaw cycles and seasonal temperature variations encourage the upward propagation of cracks in the base to the pavement surface. The infiltration of water and oxygen into the asphalt then hastens the deterioration of the road condition. Standard rehabilitation methods for cracking in roads often involve renewal of the binder and surface courses. "A very expensive solution," comments Elsing, and points out that installation of a new binder course is not always necessary. "This is where HaTelit comes into its own. The product vastly simplifies the repair procedure: instead of milling off and replacing the binder course, we can install our asphalt reinforcement directly on top of it." By taking up the tensile stresses and preventing overloading of the asphalt, the reinforcement grid with its ultralight nonwoven, delays any existing cracks from propagating into the surface course.
Depending on the type and nature of the pavement to be repaired and the planned rehabilitation solution, the HUESKER Group recommends geosynthetic reinforcement products made from polyester (PET) or polyvinyl alcohol (PVA). "The correct choice of raw material is crucial for applications in alkaline environments," says Elsing. PVA, for example, is particularly suitable for repairing concrete and partially cementitious composite pavements, which exhibit a high pH value. HaTelit's dependable performance even under extreme conditions was admirably demonstrated by a project involving partial rehabilitation of the runway at Perth Airport in Australia. Reflective cracking was reliably retarded and the service life of the reinstated surfaces prolonged through specification of a reinforcement grid made from high-modulus polyester (PET) yarn. As an investigation conducted by the airport authority confirmed, the areas repaired using the HUESKER product were still in excellent condition even after eight years use.
A strong bond
A crucial role in the rehabilitation of asphalt pavements is played by the bond strength, which specifically depends on the interlock and adhesion of the asphalt layers. These properties can be improved, above all, through provision of an optimum mesh size and a high bitumen content. "To ensure structural continuity with the asphalt, all our products incorporate a coating with a minimum bitumen content of 65%," explains Elsing. "Nothing sticks better to bitumen than bitumen."
Robust and reusable
The properties of HaTelit asphalt reinforcement offer key benefits even during the on-site works: these include the material's high resistance to installation damage, e.g. when driven over by asphalt trucks. Moreover, when HaTelit-reinforced roads are finally demolished, the material can be readily milled and the resulting mix reused. This has been verified in investigations conducted by the Institute of Highway Engineering at RWTH Aachen University, Germany, in collaboration with HUESKER.
Picture sublines:
(1) Asphalt rehabilitation during traffic operation
Rehabilitation with HaTelit asphalt reinforcement possible within short timeframe while road remains in operation.
(2) Installation of asphalt reinforcement
Wide rolls and use of spreader bar allow fast, straightforward installation.
(3) Bitumen-coated HaTelit reinforcement grid
HaTelit asphalt reinforcement grid (right), with freshly placed asphalt surface course (left).
(4) Runway before rehabilitation 2009
Heavy cracking on runway at Perth Airport in Australia prior to rehabilitation in 2009.
(5) Runway after rehabilitation 2017
Rehabilitated runway section, in sound condition even eight years' intensive use.
(6) Unreinforced area
Stress distribution of unreinforced cross-section from FEM simulation (stress concentration at crack tip).
Source: Montestruque G. E., 2002, Contribuição para a Ela-boração de Método de Projeto de Restauração de Pavimentos Asfálticos Utilizando Geossintéticos em Sistemas Anti-Reflexão de Trincas (Contribution to the preparation of a method of a project for rehabilitation of asphaltic pavements using geosynthetics on anti-reflective crack systems). Doctor’s Thesis, Technological Institute of Aeronautics, São José dos Campos, Brazil.
(7) Reinforced area
Stress distribution of reinforced cross-section from FEM simulation (loads accommodated by asphalt reinforcement).
Source: Montestruque G. E., 2002, Contribuição para a Ela-boração de Método de Projeto de Restauração de Pavimentos Asfálticos Utilizando Geossintéticos em Sistemas Anti-Reflexão de Trincas (Contribution to the preparation of a method of a project for rehabilitation of asphaltic pavements using geosynthetics on anti-reflective crack systems). Doctor’s Thesis, Technological Institute of Aeronautics, São José dos Campos, Brazil.