A week after the opening, road inspectors observed damage to the road surface, after which the pilot sites were cordoned off for further investigation, a so-called “Root Cause Analysis (RCA).” As a first step in the RCA, both pilot sites were carefully inspected. In the process, 9 symptoms were identified for further investigation. The main symptoms were damage symptoms, such as a number of places with water under the top layer, cracks in the top layer and some broken out pieces of the top layer.
Next step in the research was to formulate several hypotheses as possible explanations for the damage symptoms. These hypotheses were then tested on the basis of various tests and investigations, both at the pilot sites and in the laboratory environment. A number of road sections from both pilots were also taken for this purpose. The research finally resulted in the substantiation of one hypothesis for the cause, which explains the damage symptoms.