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Influence on the effectiveness and durability of layer composites when using viscosity-changing organic additives in asphalt

The effectiveness of the layer composite in an asphalt pavement plays an important role. To ensure all layers to act as a unit during load transfer and to avoid relative displacements between the layers, the aim is to create the best possible bond between the layers. All layers of the asphalt package are loaded both vertically by wheel loads and horizontally by braking and acceleration loads. Weather-related stresses also have an effect. The resulting shear loads at and between the layer boundaries must be absorbed by structural engineering measures in such a way that horizontal relative displacements of the layer boundaries are largely excluded. This requires an intact layer composite.

In the case of a partially disturbed or missing layer composite, the load-bearing effect of the entire fastening is changed so that a reduction or loss of the load-bearing capacity, premature material fatigue, possibly complete loosening of the composite with the result of damage and a significantly shorter service life of the entire fastening can occur. For some time now, there have been increasing reports from practice of problems with the bond between the layers of asphalt pavements that do not meet the requirements. It is assumed that the layer composite to be produced is disturbed by viscosity-changing additives used in the asphalt layers for paving reasons. This raises the question of whether these additives separate during transport and paving, accumulate on the surface and/or at the layer boundary and thus interfere with adhesion between the bitumen emulsion, binder and aggregate surfaces and the bond between the layers.

The aim of this project is to investigate these disturbance factors caused by the use of additives, which lead to a loss of layer composite, in more detail and to submit a proposed solution for application in practice.