A feasibility study exploring limestone in porous asphalt concrete: Performance evaluation and superpave compaction characteristics

Abstract

This study aims to explore the possibility of utilizing limestone in porous asphalt concrete (PAC), targeting to the lower layer of the double-layer porous asphalt pavement. Limestone aggregate, which features relatively lower strength and desirable adhesion with asphalt, is used to replace basalt aggregate in PAC due to the shortage and high price of basalt. Both PAC with limestone and PAC with basalt are formulated with Marshall design method. Engineering performance evaluation verified that in comparison with PAC using basalt, PAC using limestone has less optimum asphalt content, lower Marshall compaction numbers, inferior drainage capacity, superior low-temperature cracking resistance, comparable rutting resistance and moisture stability, while satisfy the specification requirements. Furthermore, Superpave compaction model is employed to simulate the site compaction process. The results demonstrated that Superpave compaction process is divided into initial and over densification stages, in which the voids reduction in PAC with limestone is accelerated compared to that in PAC with basalt. The dynamic modulus of PAC increases with loading frequency, decreases with test temperature, and remarkably increases with gyration numbers. The master curves of dynamic modulus for PAC are constructed, which are approximately consistent for both PACs at equivalent compaction numbers. The tensile strength of PAC is found to increase with gyration numbers and both PACs present comparable tensile strength at the given compaction numbers. It is recommended to compact PAC using limestone with 40 gyrations. Therefore, limestone PAC with appropriate design and compaction parameters is prospective as the lower layer of the double-layer porous asphalt pavement.