Research on application feasibility of limestone in sublayer of Double-Layer permeable asphalt pavement

Abstract

In double-layer permeable pavement, upper layer provides better road performance, and sublayer ensures better lateral drainage capacity. The mechanical properties of limestone are weak, so its application in upper layer is limited, while the sublayer does not directly contact with vehicle load, and the application feasibility of limestone aggregate in sublayer of double-layer permeable asphalt pavement is confirmed in this paper. Optimum asphalt contents and reasonable number of Marshall blows of limestone and basalt PAC-16 (Permeable Asphalt Concrete mixture whose nominal maximum aggregate size is 16 mm) were determined, temperature stability, water stability and water permeability were obtained. Gyratory compaction tests were designed and the compaction characteristics, mechanical properties and aggregate crushing characteristics of limestone and basalt PAC-16 were investigated. Considering the disadvantages of the existing testing methods, the concept of “actual crushing proportion (ACP)” was proposed to calculate the crushing degree of aggregate in mixture under load. It was found that the optimum asphalt content of limestone PAC-16 was higher than that of basalt mixture, and the laboratory properties related to field performance of limestone PAC-16 met the requirements of specifications in general. The equivalent compacting times of limestone mixture are slightly less than that of basalt in order to achieve the same void ratio, and the void ratio decay rate of limestone mixture is much faster than that of basalt mixture after opening to traffic. The ACP results showed that limestone aggregate > 13.2 mm can be replaced by basalt aggregate to ensure the strength of aggregate skeleton.