Pavement Type Hysteresis and Truck Rolling Resistance

Portland Cement Concrete (PCC) pavements usually incur higher investment costs than Asphalt Concrete (AC) alternatives. In a life cycle analysis the higher cost is justified by lower maintenance costs, less and fewer traffic flow intru-sions, and a longer technical life. All these factors contribute to a reduction of the carbon footprint. To further improve the sustainability of PCC pavements the rolling resistance should be lower on stiff and elastic materials like e.g. steel. To prove this thesis, studies of fuel consumption have been made where a truck is driven over different pavement structures. However, it is difficult to precisely ac-cess how much can be attributed to the pavement structure. Many factors affect the rolling resistance, such as roughness, texture, air flow et cetera. The present paper presents a different approach analyzing data from a falling weight deflec-tometer, (FWD). Pavement hysteresis is assessed by evaluating time histories. Thus, energy losses due to the properties of the pavement structure can be esti-mated. It was found that the visco-elastic properties of the asphalt had a great in-fluence of the curve in warm and hot weather. Water present and the subgrade material also affected the curve due to the material damping properties. At one field site, a motorway consisted of asphalt concrete and PCC pavement on very similar unbound materials. The difference in energy losses between the two was found significant and it is suggested that it is accounted for when comparing the two materials for life cost analysis purposes.