This paper presents the results from a laboratory study in which hot-mix asphalt (HMA) mixtures with No. 4 sieve screened reclaimed asphalt pavement (RAP) were characterized for their cracking resistance through laboratory performance testing. A typical surface mixture commonly used in the state of Tennessee was evaluated at 0, 10, 20, and 30% RAP contents. Two types of aggregate (limestone and gravel) and three types of asphalt binders (PG 64-22, PG 70-22, and PG 76-22) were used in this study. Mixture cracking resistance was evaluated through Superpave indirect tension (IDT), beam fatigue, and semicircular bending (SCB) tests. The results from this study indicated that the inclusion of RAP generally increased stiffness and indirect tensile strength; however, it generally compromised cracking resistance for the mixtures studied. Mixture properties changed significantly at 30% RAP content as compared to those with 10 and 20% RAP. Field projects validated the findings from the laboratory study.

Heterogeneous air void distribution is a common phenomenon in asphalt mixtures and is intimately related to the behavior of the asphalt mixture. Air void distribution within an asphalt mixture specimen is related to several factors, such as compaction effort, method of compaction (equipment), and aggregate gradation. In this study, virtual digital specimens generated by an open source discrete element method (DEM) program were utilized to investigate the effect of compaction factors on air void distribution. The compaction processes of a Superpave gyratory compactor (SGC) and a vibratory compactor were simulated by DEM. Effects of aggregate gradation, specimen height, mold size, mold shape, and compaction method on the inhomogeneous distributions of air voids were studied through statistical analyses. The results from DEM simulation were in good agreements with laboratory test results as well as those found in the literature. This research demonstrated that DEM simulation could be a potentially he...

High porosity with interconnected voids between aggregate particles is the primary characteristic of portland cement pervious concrete (PCPC), which, however, causes a significant decrease in its strength and abrasion resistance. In this study, latex and fiber were added to improve the abrasion resistance of PCPC mixtures. Laboratory tests were conducted to evaluate the performance of latex-modified pervious concrete with a particular focus on abrasion resistance. Test results show that adding latex desirably improved strength and abrasion resistance of PCPC, whereas fiber did not show a significant effect on the mechanical properties of PCPC. In addition, the asphalt pavement analyzer (APA) abrasion test was found to be feasible for evaluating the abrasion resistance of pervious concrete.

Moisture-induced damage has long been recognized as one of the major concerns for asphalt pavements. To mitigate potential moisture damage, one general method is to add mineral antistripping additives or liquid antistripping agents into hot-mix asphalt (HMA) mixtures. In this study, a comparative laboratory experiment was conducted to investigate the effectiveness of cementitious fillers on moisture susceptibility of HMA mixtures. Five types of cementitious fillers were considered: fly ash, cement kiln dust, and three types of hydrated lime with different finenesses. The laboratory performance of HMA mixtures subjected to moisture conditioning was evaluated through the following tests: dynamic modulus test; superpave indirect tensile tests; and tensile strength ratio test. The test results indicate that the cementitious fillers were generally effective in reducing the moisture susceptibility of HMA mixtures. The finer the hydrated lime particle, the more resistant the asphalt mixtures. In addition, dynami...

Use of recycled asphalt shingles (RAS) into asphalt mixture has become more popular in asphalt paving industry due to dwindling natural resources and potential economic benefits. However, one critical question arises as to how much of aged asphalt binder in RAS can be effectively blended with virgin binder during mixing and construction. This paper presents a laboratory study in which gel permeation chromatography (GPC) was used to determine the blending efficiency of RAS. A correlation was first established between percentages of large molecules (LMS) obtained from GPC and rheological properties of RAS binders. Then the relationship was used to estimate the blending efficiency of RAS binders. The effects of aggregate size, RAS content, and mixing time on blending efficiency were evaluated. The test results show that the percentage of LMS was highly correlated with the complex shear modulus (G*) of asphalt binder. Increasing mixing time led to a better blending of RAS mixture. Aggregate size did n...