Temperature-dependent voids and their impact on SMA surface course permeability

Abstract

This study investigates the water permeability characteristics of newly constructed Stone Mastic Asphalt (SMA) surface course, with a specific focus on the influence of connected voids arising from the compaction temperature during pavement construction. On-site evaluation of the permeability coefficient was performed, followed by core sample extraction from the same locations to investigate the correlation between the permeability coefficient and porosity. Industrial CT scanning was used to identify and separate void regions in the core samples. Three-dimensional digital reconstruction techniques were employed to analyze the morphology and spatial distribution of voids within the core. The connectivity of voids was assessed, providing insights into water infiltration pathways within the SMA course. Additionally, finite element simulation of the pavement temperature field was conducted to investigate the spatially differentiated distribution of voids within the SMA course.The findings reveal that approximately 38.3% of the voids are concentrated within a 1 cm depth below the top surface of the 4 cm-thick SMA course. The aggregation of voids enhances the likelihood of interconnection, facilitating water seepage. Water infiltrates through the open voids on the top surface and flows vertically and horizontally along the interconnected pathways. Notably, at a depth of approximately 2.5 cm, the flow transitions to horizontal spreading, aligning with the primary distribution interval of interconnected voids. The non-uniform distribution of voids is primarily influenced by the compaction temperature. The top and bottom portions exhibit higher void percentages, while the middle portion shows relatively fewer voids, consistent with the observed compaction temperature pattern.