Minnesota’s harsh climate requires dense, durable asphalt to avoid frequent maintenance and replacement. Asphalt mixes as designed in the laboratory, however, don’t always perform consistently in the field. A new Superpave mix shows promise for providing cost-effective, high-performing pavements for state roadways.
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Increasing Cold In-Place Recycling Efficiency for Pavement Rehabilitation
New tools will help local road engineers reliably estimate the curing time of a cold in-place recycling (CIR) layer. Researchers identified factors that affect asphalt curing when a CIR method is used to know when pavement is sufficiently hardened, which will minimize delays in road construction and reopening.
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Quantifying the Benefits of Improved Compaction
Compaction is the final and most critical step in asphalt pavement construction. National research conducted several years ago indicated that a slightly more compact pavement than typical could help roads last longer. To understand the relationship between pavement density and long-term performance, MnDOT has built a database with performance data from samples collected soon after they were constructed more than a decade ago. The agency hopes to eventually have enough data to determine the right amount of compaction.
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Innovative Additions Could Help Asphalt Pavements Sense Damage—and Repair Themselves
This article was originally published in Catalyst, January 2022.
University researchers are investigating ways to extend the life of asphalt pavements and generate cost savings by adding innovative materials to asphalt mixes. In a recent study, they found that improving asphalt mixes with graphite nanoplatelets and taconite concentrates offers new possibilities for enhancing damage-detection techniques and restoring subsurface cracking using microwave energy.
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Quantifying the Effect of Geogrids in Asphalt Pavement Foundation Layers
Geogrid inserted between the layers of asphalt pavement during construction can increase the strength and durability of the finished road. To help engineers decide whether to use geogrids in road construction projects, researchers calculated just how much strength and durability geogrid material can add to an asphalt pavement and integrated the findings into MnDOT’s design software.
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Evaluating Cracking Resistance Test Methods for Asphalt Pavements
A new method of testing low-temperature cracking in asphalt pavement shows promise for design, quality control and quality assurance. Test results produced by the new method, which is faster and less expensive than the previous method, match well with results from the older method.
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Evaluating the Impact of J-Band on Pavement Service Life and Crack Resistance
Potholes and other pavement failures in asphalt typically occur at the seams between lanes, where the mixture loses density during compaction because the edges are not confined like they would be with cement concrete forms. Researchers found that spraying J-Band, a void-reducing asphalt membrane (VRAM), in a band along longitudinal joints before asphalt layers are applied increased bond strength, lowered permeability and air void levels, and improved crack resistance.
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Investigating Asphalt Pavement Stripping Under Seal Coats
A recent Local Road Research Board (LRRB) study confirmed that increased freeze-thaw activity during Minnesota winters leads to delamination of seal coats from underlying pavements. Researchers identified optimal seal coat mix combinations and site conditions that may ensure effective seal coating of asphalt pavements in cities and counties around Minnesota.
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Asphalt Delivery Tracking Goes Digital with Some 2020 Construction Projects
MnDOT construction projects require tons of hot mix asphalt each year, with over 188 road and bridge projects in the 2020 construction season alone.
Historically, plant mixed asphalt has been weighed, tracked and paid for with computer-generated paper tickets. Paper ticketing isn’t an ideal process for a variety of reasons—on-site ticket collection poses safety risks, tickets can be easily lost, and data must be tabulated manually, just to name a few.
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Evaluating the Performance of CIR Mixtures With Reduced Binder Content
Researchers examined the practice of reducing the binder content of cold in-place asphalt recycling mixtures in the field on especially hot days to improve workability. Laboratory testing of mixtures at various temperatures and binder levels found the practice keeps mixtures workable, improves compaction and does not significantly diminish performance.
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