Sheng Zhao

Performance of Multiaxial Paving Interlayer–Reinforced Asphalt Pavement

AbstractPaving interlayers have been used in asphalt concrete (AC) overlays for a variety of benefits. An earlier study showed that different paving interlayers improved mixture performance, while the multiaxial interlayer provided the best overall laboratory performance. This paper presents further investigation of the reinforcing effect of the multiaxial interlayer on the entire pavement. Pavement structural analysis using finite-element method (FEM) analysis and several specialized commercially available software were conducted, and field test sections were established and surveyed to further validate findings from the previous study. The pavement structural analyses were in agreement that using interlayer could improve fatigue crack resistance and extend service life. The three-yarn biaxial interlayer showed the best reinforcement potential of fatigue crack resistance, followed by the multiaxial interlayer and the two-yarn biaxial interlayer. The FEM analysis indicated that the multiaxial interlayer c...

Dynamic Modulus Characterization of Alaskan Asphalt Mixtures for Mechanistic-Empirical Pavement Design

AbstractDynamic modulus (|E*|) is one of the primary required inputs for the mechanistic-empirical pavement design of asphalt concrete (AC) pavements. Prediction of |E*| using specific models and c...

Asphalt Binder Adaption for Climatic Conditions in Cold Regions: Alaska Experience

AbstractAsphalt binder adaptation in cold and spacious areas such as Alaska is critical because of varying climates and seasonal extreme conditions. To fully address the binder selection issues in Alaska, this paper presents a study that conducted analysis based on a long-term pavement performance (LTPP) database to reveal the climatic effects on binder selection, followed by evaluation of the laboratory and field performance of hot mix asphalt (HMA) containing neat binder and several currently used modified binders in Alaska. It was found that the recommended high performance grading (PG) grades for the entire Alaska are equal to or lower than 52°C, whereas the low grades in more than 76% of the recorded weather stations in Alaska are recommended to be lower than −28°C. Laboratory testing results showed that HMA with high-end modified binders expressed higher rutting resistance than that containing the neat binder PG 52-28, and HMA with the neat binder displayed the lowest resistance to low-temperature c...

Characterizing Stress–Strain Relationships of Asphalt Treated Base

AbstractIn a flexible pavement, the base course is an essential component in that it supports the surface course and distributes traffic loads to the subbase and subgrade. Asphalt treatment is used on granular base course material to enhance the material’s properties and overcome its deficiencies. Due to its lower binder content and lower-quality granular material, asphalt treated base (ATB) exhibits a stress–strain relationship unlike either regular granular material or hot mix asphalt. Stress−strain relationship is the primary fundamental material property used for mechanistic-based pavement structural analysis and design. However, current guidance for choosing the parameter that characterizes the stress−strain relationship of ATB in pavement design is not clearly provided. This paper presents a study in which the stress−strain relationship of differing base materials, including three ATBs, a mixture of reclaimed asphalt pavement and granular material, and a typical granular base material, is compared a...

Field Evaluation of Precut Thermal Cracks in an AC Pavement in Alaska

Thermal cracking is a natural feature of most of Alaska’s asphalt concrete (AC) pavements that influences long term maintenance costs and drivers’ perception of road performance. Major transverse thermal cracks penetrate through not only the pavement layer itself but usually extend several feet into the aggregate materials below. A significant portion of Department of Transportation (DOT) Maintenance and Operations budget has been allocated to crack sealing and associated work. However, Alaska researchers are beginning to understand that the inevitable thermal cracking can be significantly controlled by making simple changes to new road designs. Past research in Alaska and elsewhere found that thermal cracks can be controlled if properly spaced saw cuts are made in the pavement surfaces of newly built pavement structures. Research presented in this paper looks at the different case of whether precutting can influence thermal cracking when only the top few inches of an old, thermal cracked, pavement structure have been reconditioned and repaved. Two years of monitoring show that precutting exerts significant control on thermal cracking of the new pavement surface even if most of the previously-cracked underlying aggregate pavement structure was left in place. However, precutting is most effective when the saw cuts are made at or very near the locations of the old thermal cracks.

Crack Surveying Methods to Evaluate Sealing Practice in Alaska

It has long been suggested that a much more economical and sustainable approach be developed to address crack sealing effectiveness in Alaska. The development of a new method named special thermal crack evaluation (STCE) in a previous study served to directly and efficiently guide the crack sealing practices as opposed to the other nationally-used pavement surveying methods, including Long Term Pavement Performance (LTPP) and Pavement Surface and Evaluation Ratings (PASER) . However, no or little research has been found to compare and correlate STCE with the other two methods. This paper presents a study to fulfill this research need. Further data interpretation showed that STCE was capable of guiding the decision-making on crack sealing practices, while the other two methods provided quantitative measurements and general rating of the sealed or non-sealed cracks. In addition, the correlation between STCE and the other two methods recommended that STCE better be used along with the other two methods for a better and more complete guidance on current or potential crack sealing practices.