Evaluation of Moisture Sensitivity Performance of Stone Mastic Asphalt Mixes with Additional Filler: A Laboratory Comparison of Dry and Wet Mixing Methods

Gap-graded mixtures are one of the areas of improving the permanent deformation strength of hot-mixed asphalt mixtures. Additional filler materials can be needed due to the high bitumen amount and the less fine aggregate amount in the mixture. In this study, the effects of filler additives on moisture susceptibility of the gap-graded hot-mixed asphalt mixtures and mixing methods are investigated. Filler additives such as class C and class F fly ashes and hydrated lime are used 0.5 %, 1.0 %, 2.0 %, and 4 % of the total weight of mixture instead of mineral filler. Design mixtures are prepared according to the Turkish Highway Technical Specifications (THTS). To determine the effect of mixing methods, dry and wet (slurry) methods are used to mix the filler materials. Modified Lottman method (AASHTO T283) are used to determine the moisture susceptibility. An indirect tensile strength test is the measurement of bitumen film thickness which is also conducted. Test results showed that class C fly ash is significantly improved the moisture susceptibility of mixtures. While the slurry method does not give the expected improvement on class C fly ash added mixtures, it shows a positive effect on class F fly ash and hydrated lime added mixtures.

Fiber-Reinforcing Effect in the Mechanical and Road Performance of Cement-Emulsified Asphalt Mixtures

Cement-emulsified asphalt mixture (CEAM), a kind of cold mix asphalt mixture, has the advantages of energy conservation and emission reduction as well as easy construction. However, the performance of CEAM is not as good as hot mixed asphalt mixtures. Hence, in this study, two different fibers were adopted as the reinforcing phase to improve the comprehensive properties of CEAM. The results indicated that the addition proportion and curing time were crucial to fiber-reinforced cement-emulsified asphalt mixture (FRCEAM). The compressive strengths, water stability, and raveling resistances of FRCEAM preparations with polyester or brucite fibers (FRCEAM-PF and -BF, respectively) were enhanced significantly. FRCEAM-PF had the maximum flexural tensile strength and strain, which meant that its low-temperature performance was the best compared to FRCEAM-PF and CEAM. However, the contribution of PF to CEAM high-temperature stability was greater than that of BF. Fiber addition to CEAM not only enhanced the cycles of fatigue loading but also reduced sensitivity to changes in stress level. Furthermore, FRCEAM-BF durability was slightly better than that of FRCEAM-PF. SEM analysis indicated that fibers provided bridging and meshing effects. Although PF and BF showed different enhancement effects, both mixtures met the requirements for hot mixed asphalt mixtures.