Minnesota Department of Transportation
This project focuses on the second construction phase of the Minnesota Road Research facility (Mn/ROAD) and evaluates three typical, locally available, surfacing aggregates along with a rollover section from the initial phase for performance. The project results indicate that the adsorption test did not predict the performance of the sections in this experiment. All of the aggregates were characterized as marginal in terms of moisture and frost susceptibility. The sections with the greatest percentage of fines typically performed better than sections with a low percentage of fines. The Minnesota Department of Transportation issued a technical memorandum to change the specification from 0-15% to 8-15% passing the No. 200 sieve for Class 1 surfacing aggregate. The project also compared freezing and thawing rates on the aggregate sections to nearby hot mix asphalt (HMA) sections. Soil at any particular depth froze four to five days before HMA sections. The aggregate sections also thawed at exponential slower rates as depth increased from 11 to 35 days, which means that an aggregate surfaced road will freeze sooner and thaw slower than an HMA surfaced road. This information impacts the management of spring load restrictions and winter load limits.
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