Damage evolution assessment of innovative sustainable semi-flexible pavements through intermediate Accelerated Pavement Testing

The use of semi-flexible pavements allows for the achievement of a good level of performance and safety in heavy-load areas. A wearing layer of grouted macadam usually characterises this pavement type. Grouted macadam is a composite material consisting of a Hot Mix Asphalt (HMA) skeleton grouted using a cementitious matrix in a second phase. Grouted macadam use is limited, being its production process quite complex. To overcome this issue, in recent years, Ready to Mix (RTM) materials have been proposed as a more practical alternative while maintaining high performance. RTM are indeed produced by directly mixing the aggregate with bitumen emulsion and a cementitious filler at ambient temperature. This research presents the results of a testing campaign on an experimental trial section built in 2017 on an Italian road. The RTM was placed as base layer in the semi-flexible pavement structure in the trial section. Specifically, the testing campaign included Falling Weight Deflectometer (FWD) surveys, and an intermediate Accelerated Pavement Testing (iAPT) investigation conducted using a Fast Falling Weight Deflectometer (FFWD). The correlation between the FWD and FFWD results, as well as the traffic survey data, allowed the calibration of the field RTM damage curve to obtain an accurate assessment of the evolution of the RTM performance. The results highlighted that the RTM is characterised by excellent fatigue resistance and, consequently, durability.