Impact of Construction Variability on Pavement Performance: Report I
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The long term performance of hot mixed asphalt (HMA) pavements is significantly impacted by the properties of the HMA mixture. Regardless of how well the mix design and structural design have been prepared, the properties of the materials delivered to the job site, such as gradation, binder content, and the in-place compaction will ultimately control the behavior ofthe pavement under the combined action oftraffic and environment. The job mix formula allows for certain tolerances in the HMA construction, this research studied the effect of construction variability on performance if the delivered product goes outside the tolerances range. The construction variability was studied for the northern (Lockwood) and southern (Sloan) Nevada aggregate sources mixed with an unmodified AC-20 and AC30, respectively. Forty two mixes were prepared for each source and tested for general strength using the resilient modulus, for rutting using the Asphalt Pavement Analyzer, for fatigue using the flexural beam fatigue and for thermal cracking using the Thermal Stress Restrained Specimen Test. Construction variability has a significant impact on pavement performance regardless of the aggregate source and binder type. However, some laboratory prepared mixtures may provide better performance than the optimum mixture but such mixtures may be impractical in the field. If the contractor violates the specification limits, then there is 81% chance that the pavement section will have lower performance than the optimum mix, therefore quality control is recommended to keep the mixes within the specification limits.