United States Department of Transportation
i
Comparison of pelletized lime with other antistripping additives.
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2014-05-01
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[PDF-1.03 MB]
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Abstract:Stripping is a common problem in HMA pavements in Oregon, especially in Eastern Oregon.
Stripping is the degradation of the bond between the aggregate and the asphalt binder due to the
presence of water – this mechanism of degradation can lead to loss of capacity and cracking in the
pavement. A common additive used in the industry to mitigate stripping damage is powdered lime.
However, challenges with air-borne powdered lime have SHAs investigating alternatives to powdered
lime. The purpose of this study was to determine the effectiveness of potential alternatives to
powdered lime additive in preventing stripping.
This research evaluated the moisture susceptibility of five anti-stripping additives with three separate
aggregates. The aggregates exhibited a range of potential stripping from not susceptible to susceptible.
Results indicate that Aggregates 1 and 3 are likely susceptible to stripping, with Aggregate 3 likely
being the most susceptible. Powdered lime increased the TSR and ECS ratios for the susceptible
aggregates. Mixtures with Additive 4 exhibited similar performance to mixes containing powdered
lime. Additive 2 exhibited improved performance compared to the control but TSR and ECS ratios
were lower than the specimens with powdered lime. Results from mixtures with Additive 3 exhibited
limited improvements in TSR and ECS ratios. Additives 4 and 2 should be considered for future use in
HMA when stripping could be an issue.
One practice in ODOT is to inlay HMA pavements 15 years after construction. If the pavement is
exhibiting damage resulting from stripping, the inlay can be specified to be 4 inches (102 mm) deep. If
the pavement is not exhibiting damage from stripping, the inlay can be specified at 2 inches (51 mm)
deep. Using this information, an economic analysis was performed. Other options are available but
these were not included in the analysis. The economic analysis indicates that when a reduction in inlay
thickness is realized, there is significant value in using additives. The sensitivity analyses indicated
that large changes in the input variables do not make the cost of using additive cost ineffective – that
is, there is significant value in using additives even when input variables (rate of return, number of
future inlays, inlay depth, cost of inlay HMA, original construction cost, and additive cost) change
significantly.
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