Discovery Magazine

Improving the Properties of Reclaimed Asphalt Pavement for Roadway Base Applications (CR)

Extensive research on Reclaimed Asphalt Pavement (RAP) indicates that it possesses both positive and negative engineering behavior. On the plus side, it is a drainable granular material with adequate shear strength. However, engineering concerns arise because reclaimed asphalt pavement exhibits both low bearing ratios and extensive creep [1], [2], [3]. These undesirable engineering properties result from the engineering behavior of the asphalt surrounding the aggregates. The statewide variability of reclaimed asphalt pavement was investigated and found to be of minimal concern with a minor exception formaterials with high shell contents, typically associated with Southwestern Florida (i.e. Collier County) [3].

Blends of reclaimed asphalt pavement and AASHTO A-3 sands showed promise in reducing creep when at least 50% of the RAP is replaced with A-3 sand or when layering is used with the sand as the top layer. This research showed that decreasing the asphalt content also decreased the amount of creep [3]. AASHTO A-3 sand was recently chosen for blends after initial testing with fine sand obtained from dredge spoil showed improvements in density and bearing ratios [2]. This AASHTO sand is considered to have average engineering properties especially in terms of strength and stiffness. Research showed that the majority of creep dissipated within the first few days during laboratory testing [3], indicating that innovative construction procedures could be developed to control creep levels. Further research using blends with higher quality engineering materials may lead to increases in bearing ratios and reduction of creep.