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WESTERN REGIONAL
SUPERPAVE CENTER
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Impact of Construction
Variability on Pavement Performance 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 of the pavement under the combined action of traffic 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 AC-30, 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. Available Information: Reports: Interim Reports: Impact of Construction Variability on Pavement Performance Report-2: Impact of Construction Variability on Pavement Performance Presentation: Impact of Construction Variability on Pavement Performance Development of a Joint Density
Specification The overall objective of this research was
to establish the needed knowledge base for the development and implementation of a
longitudinal joint specification for the Nevada Department of Transportation (NDOT). This
objective was met through the conduct of two major phases: a) Phase
I. Review the literature on research efforts and current specifications for longitudinal
joint geometries and compaction techniques employed by various highway agencies. b) Phase
II. Conduct a field-testing program to evaluate the effectiveness of the various joint
geometries and compaction techniques in increasing the joint density and providing
improved performance. In order to meet the objective of this
research two field-test projects were built: one project on highway US 395 - Washoe Valley
in northern Nevada and one project on highway US 95 - Las Vegas in southern Nevada. The
field-testing program evaluated five joint geometries and two compaction techniques. The five joint geometries selected were: · Natural slope · Edge restraining device · Cut edge with rubberized asphalt tack coat · Cut edge without rubberized asphalt tack coat ·
Tapered joint at 3:1. The rolling techniques selected were:
· Rolling from the hot side with 6” overlap on the cold side ·
Rolling from the hot side at
6” away from the joint Nuclear density gauges and field cores were used to evaluate the in-place density of each treatment. The densities were measured at both sides of the joint and at the mid-width of the mats of the two lanes placed on each side of the joint. Reports: Development
of a Joint Density Specifications, Phase I: Literature Review and Test Plan Development of a Joint Density Specification, Phase II: Evaluation of Test Sections Development of a Joint Density Specification, Phase II: Evaluation of 2004 and 2005 Test Sections
Develop a system to Mitigate Reflective Cracking of Flexible Pavements In 2006, the Nevada DOT initiated a three-phase research project to identify the promising techniques to mitigate reflective cracking in HMA overlays: a) Phase I: Review of literature and the performance of the various techniques in Nevada, b) Phase II: Identify analysis models and evaluation tests, and c) Phase III: field verification of the selected techniques and validation of analysis models. The following reports summarize the findings and recommendations for the Phases I and II of this research study REFLECTIVE CRACKING OF FLEXIBLE PAVEMENTS PHASE II: REVIEW OF ANALYSIS MODELS AND EVALUATION TESTS REFLECTIVE CRACKING OF FLEXIBLE PAVEMENTS PHASE I AND II FINAL RECOMMENDATIONS
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