Developing Critical Field Permeability and Pavement Density Values for Coarse-Graded Superpave Pavements

Abstract

Within the hot-mix asphalt (HMA) community, it is generally accepted that the proper compaction of HMA is vital for a stable and durable pavement. Low in-place air voids have been shown to lead to rutting and shoving, whereas high in-place air voids have been shown to reduce a pavement’s durability through moisture damage and excessive oxidation of the asphalt binder. Recent research has suggested that coarse-graded Superpave-designed mixes are more permeable than conventionally designed pavements at a given air void content. This higher permeability can lead to durability problems. The pavement density at which coarse-graded Superpave mixes become permeable was evaluated by using a field permeability device. On the basis of the data collected, 9.5- and 12.5-mm nominal maximum aggregate size (NMAS) mixtures become excessively permeable at approximately 7.7 percent in-place air voids, which corresponded to a field permeability value of 100 × 10−5 cm/s. Mixtures having a 19.0-mm NMAS became permeable at 5.5 percent in-place air voids, which provided a field permeability value of 120 × 10−5 cm/s. Coarse-graded mixes having an NMAS of 25.0 mm became permeable at 4.4 percent air voids, which corresponded to a field permeability value of 150 • 10−5 cm/s.

Factors affecting hydraulic conductivity of asphalt mixture

“…where A, B and C are constants, different than in (15), (16) and (17). Finally, the asymptotic value of the hyperbole when the hydraulic conductivity has a vesry low value is (18) to the experimental data in Fig.…”

“…7a is not correct, because all the points seem to align with a single model independently of the type of mixture used. For this reason, we will select the model (16) to fit hydraulic conductivity data.…”

“…(2) Exponential [16] power [17] and hyperbolic [18] models, which are arbitrarily selected and do not have a physical or fundamental statistical basis. (3) Norambuena-Garcia model [19] that was deduced from physical principles and is not representative for mixtures with very low hydraulic conductivities [16].…”

Effects of vehicle speed and permeability on pore pressures in hot-mix asphalt pavements

“…The friction course is often an open-graded mix that contains a lower percentage of fine aggregate than the structural course and a larger nominal maximum aggregate size (NMAS). The fewer fines and larger NMAS of the friction course result in more connectivity of air voids leading to an increase in permeability as noted by Mallick et al [1], and Cooley et al [2]. The permeability is further increased, as it is generally accepted that newly placed HMA pavements are placed at a higher than designed air void content (6-8%) with the assumption that traffic loadings will decrease the air void content through time.…”

Laboratory and field investigations of permeability and surface temperature of asphalt pavement by infrared thermal method

“…Some researchers reported higher moisture content exits where the permeability is greater [10][11][12]. In terms of the heat transfer, evaporation process generally results in the loss of heat when the water changes from liquid state to gas state.…”