Abstract:
Asphalt mix designs tend to optimise the load transfer via aggregate skeletons as main mechanism
to provide rut resistance, often to the detriment of durability. Permeability, as a significant
durability indicator, is more difficult to measure in the field than in the laboratory. Voids in the
asphalt mix have a critical zone where an increase in voids is exponentially linked to permeability.
This zone is where voids start to become increasingly interconnected. The aggregate grading
envelope characteristics can provide an indication of the interconnectedness of the voids to
enhance quality control. New rational Bailey Method Ratios (BMRs) were defined with contiguous
aggregate fractions in the numerator and denominator. This allows also for porosity calculation
using the Dominant Aggregate Size Range (DASR) method. The Binary Aggregate Packing (BAP)
triangle porosity diagrams provide insight into the link between porosity and interconnected voids.
The wall and the loosening effects create additional porosity (voids) with increased probability
of interconnectedness. Clear threshold zones of interconnected voids can be determined with
BAP coarse/fine mass ratios. The latter is the inverse of the rational BMRs. It allows for simple
spreadsheet calculations of porosity and coarse/fine mass ratio as a screening tool for probable
permeability via benchmark analysis. Reworked data sets demonstrated how the inverse of BMRs
could show potential for interconnectedness of voids and, therefore, permeability propensity.
