The durability of selected asphalt concrete components and mixtures from six projects were evaluated
with the newly recommended net adsorption test and the more common ASTM D4867 (a modified
Lottman), respectively. The net adsorption test was used to assess the durability of the adhesion of the
asphalt to the aggregate surface in the presence of water. The ASTM D4867 method evaluated the
retained strengths of compacted mixture resistance after freeze/thaw conditioning.
The net adsorption results indicated at least two of the six projects could be susceptible to moisture
related adhesion problems. The test method was adjusted to use the full aggregate gradation rather than
only the fine fraction. A comparison of these results to those originally reported by Strategic Highway
Research Program (SHRP) researchers showed good agreement in both trends of results and withinlaboratory
test method variability (about 0.14 mg/g).
The mixture testing indicated that three of the six projects had tensile strength ratios of less than 70
percent and could be expected to show some evidence of moisture related damage. An evaluation of these
results suggested that any moisture sensitivity could be due to mix design parameters such as lower film
thicknesses, and lower initial strengths rather than a chemical loss of adhesion at the asphalt-aggregate
interface. The influence of conventional mix design parameters on the moisture sensitivity of asphalt
concrete mixtures should be more thoroughly investigated prior to any consideration of the use of
Stroup-Gardiner, Mary; Newcomb, David.
Physio-chemical evaluation of asphalt-aggregate interactions.
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