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Experiment 2 at the Louisiana Accelerated Loading Facility (ALF) site involved determining the engineering benefits of using powdered rubber modifier (PRM) in hot mix asphalt mixes. Three full scale test sections were constructed and subjected to increasing loads from the ALF. Lane 2-1 included PRM in the wearing course, lane 2-2 included PRM in the base course, and lane 2-3 was the control section. Distress and deflection measurements were performed every 25,000 applications of the ALF. Laboratory material characterizations of test lane materials were used in ABAQUS and FLEXPASS modeling studies to predict the behavior and performance of the test lanes. Comparisons of observed and predicted rutting were developed and discussed. Deflection measurements were used to develop a-values for the powdered rubber modified layers for use in pavement design. The recommended a-value for the PRM wearing course was 0.25; it was 0.45 for the PRM base.
3 test lanes constructed at the Louisiana Pavement Research Facility (PRF) to study the performance of Asphalt Rubber Hot Mix Asphalt (AR-HMA) materials, and determine the best possible location of AR-HMA materials within the pavement structure.
A promising pavement rehabilitation strategy that is of interest to state highway agencies and local governments involves the in-place pulverization of failed hot mix asphalt (HMA) pavements and re-use of the pulverized material as a granular base material. Advantages of this technique include a reduction in the use of virgin aggregate, a reduction in the amount of construction traffic, and removal of the potential for reflective cracking from the existing cracked pavement layers through the new HMA surface. However, the performance of this technique has not been comprehensively evaluated, and, in particular, permanent deformation characteristics. In this thesis, four pilot projects in northeastern California were used to evaluate the pulverized material and this rehabilitation strategy. The characteristics and performance of the pulverized material were evaluated by comprehensive laboratory and field testing, and analyses. Based on the multistage repeated load triaxial test results, the shakedown limits of the pulverized material were estimated and compared with the stress states calculated from the cross-anisotropic finite element analyses based on real traffic and climate data. A recursive-incremental damage model was used to predict permanent deformation of the pulverized base layer over the long term and to compare it with that of typical aggregate base material. Based on the comprehensive laboratory testing, field testing, and analyses, the pulverized material was found to be generally stiffer than typical aggregate base material, possibly due to better aggregate shape than that found in typical aggregate base material. The pulverized mateiral has less permanent deformation resistance at low stress levels but greater resistance at higher stress levels than typical granular material used in California. Possible reasons for the lower permanent deformation resistance at low stress levels might be the laboratory compaction method and that the recycled HMA in the pulverized material undergoes additional breakdown under initial loading since coarse fractions of the pulverized materials are greater than that of the comparison virgin aggregate base. Overall, the performance benefits of this rehabilitation strategy make it a viable option for flexible pavement rehabilitation.
In an effort to study sustainable environmentally friendly pavement, the physical mechanics and road performance of warm-mix asphalt mixtures based on an emulsifying platform were studied via the Marshall design method. The results show that the optimum asphalt content of warm-mix asphalt mixtures is generally higher than that of hot-mix asphalt mixtures by 0.1 % to 0.2 %; the values of the stability, bulk specific gravity, air voids, and voids in mineral aggregate do not change significantly; and the number of voids filled with asphalt and the flow value increase a little. The residual stability value of warm-mix asphalt mixtures increases, whereas the freeze-thaw splitting strength decreases. The high-temperature performance and seepage performance of warm-mix asphalt mixtures are similar to those of hot-mix asphalt mixtures.