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This note presents some constant-head permeability test results on 30 granular mixtures. These data are then interpreted using the grading entropy approach, as well as the ‘Hazen’, ‘Shepherd’, ‘Kozeny–Carman’ and ‘Chapuis’ models. The predictive power of each of the five methods is compared. A correlation between the normalised grading entropy coordinates and the coefficient of permeability is presented. Permeability zones on the normalised entropy diagram are identified.

This research addresses various notions and perceptions associated with using recycled asphalt pavements for road construction. The research investigates how the residual binder in severely aged recycled asphalt pavements with penetration between 3 and 7 decimillimeter (dmm) influences cold asphalt emulsion mixtures in comparison to moderately aged recycled asphalt pavements with a penetration of about 20 dmm. Cold-mix asphalt specimens were produced using recycled asphalt pavements, recycled asphalt pavements with the residual binder extracted and virgin aggregates. The recycled asphalt pavement was aged to simulate moderately and severely aged asphalt pavement conditions (20 and 5 dmm, respectively). The results show that cold asphalt emulsion mixtures produced using recycled asphalt pavements with residual binder in them had considerably higher stiffness, fatigue and permanent deformation results in comparison to recycled asphalt pavements without the residual binder. The 20 pen recycled asphalt pavements produced the stiffest specimens and gave the greatest fatigue lives, although the 5 pen recycled asphalt pavements gave the best resistance to permanent deformation. Specimens with recycled asphalt pavements from which the binder had been removed performed poorly. This research study shows that the residual binder in recycled asphalt pavements adds valuable mechanical and performance properties to cold-mix asphalt.

Pavements are ubiquitous civil engineering structures which form the important lifelines that connect communities. They must remain serviceable after events such as flooding, cyclones and extreme freeze-thaw cycles. The hydraulic conductivity of road pavements is important to understand their performance. This paper summarises some recent work aimed at improving the prediction of the hydraulic conductivity of asphalt concrete. Laboratory test results show the use of the 'hand pumping method' to measure the percentage of connected air voids in asphalt concrete specimens. The representative pore size concept is used to analyse an updated database of hydraulic conductivity measurements of asphalt concrete. The effect of nominal maximum aggregate size is studied. Preliminary efforts to use the grading entropy framework to predict the hydraulic conductivity of asphalt concrete are reported.