Comparison of pelletized lime with other antistripping additives.

PDFTech ReportFHWA-OR-RD-14-14SPR 732Hot mix paving mixturesStripping (Pavements)Antistrip additivesCalcium oxideTensile strengthCost effectivenessMoisture contentAsphalt mixturesOregonOregon. Dept. of Transportation. Research SectionTrejo, DavidPorter, FrankChen, JiamingLee, Hyun WooKiewit Center for Infrastructure and TransportationUnited States. Federal Highway AdministrationUS Transportation CollectionStripping 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 thepresence of water \u2013 this mechanism of degradation can lead to loss of capacity and cracking in thepavement. 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 powderedlime. The purpose of this study was to determine the effectiveness of potential alternatives topowdered lime additive in preventing stripping.This research evaluated the moisture susceptibility of five anti-stripping additives with three separateaggregates. 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 likelybeing the most susceptible. Powdered lime increased the TSR and ECS ratios for the susceptibleaggregates. Mixtures with Additive 4 exhibited similar performance to mixes containing powderedlime. Additive 2 exhibited improved performance compared to the control but TSR and ECS ratioswere lower than the specimens with powdered lime. Results from mixtures with Additive 3 exhibitedlimited improvements in TSR and ECS ratios. Additives 4 and 2 should be considered for future use inHMA when stripping could be an issue.One practice in ODOT is to inlay HMA pavements 15 years after construction. If the pavement isexhibiting damage resulting from stripping, the inlay can be specified to be 4 inches (102 mm) deep. Ifthe 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 butthese were not included in the analysis. The economic analysis indicates that when a reduction in inlaythickness is realized, there is significant value in using additives. The sensitivity analyses indicatedthat large changes in the input variables do not make the cost of using additive cost ineffective \u2013 thatis, there is significant value in using additives even when input variables (rate of return, number offuture inlays, inlay depth, cost of inlay HMA, original construction cost, and additive cost) changesignificantly