Development and evaluation of test procedures to identify moisture damage prone hot mix asphalt pavements.

摘要

There are numerous factors that can cause a road to deteriorate, such as the traffic type, traffic volume, failure of materials used and climatic conditions. All four of the above listed factors can contribute to permanent deformation, commonly called pavement rutting. Most permanent deformation tests and simulation models have concentrated primarily on material properties and traffic loads. The effects of the environmental conditions are often neglected in these models with only a few accounting for climatic effects. The damaging effect of moisture on pavements, specifically hot mix asphalt (HMA), is a significant environmental distress that should be considered. As pavement is subjected to freeze/thaw cycling, the material expands and contracts. During expansion, water can seep into permeable air voids created with the increased volume and freeze. When the material contracts during thawing, the water can propagate cracks created during freezing for further damage in the next freeze cycle, which can weaken the structural strength of a pavement layer. Over time, the repetition of freeze/thaw cycling deteriorates a pavement and can lead to lengthwise indentations in roads appearing as ruts if a moisture susceptible mix is below the surface mix. Surface mixes that are susceptible to moisture damage would experience raveling. Identifying pavements susceptible to moisture damage and the effects of moisture damage on the life of a pavement can reduce maintenance costs accrued with the placement of a poorly performing HMA.; In this dissertation, the affect of moisture on HMA materials is evaluated via an Asphalt Pavement Analyzer (APA) and a modified Dynamic Shear Rheometer (DSR). It was found that moisture damage of specimens tested in an APA after one freeze/thaw cycle yields similar results as Tensile Strength Ratio testing after three freeze/thaw cycles. The APA is seen as a viable alternative for evaluating moisture susceptible mixes. A new protocol for a modified DSR is outline and evaluated using 21 field collected HMA mixes. It was concluded that the new test protocol and modification have potential for being used as a method to determine the moisture susceptibility of a binder.