Investigation the Effect of Cement Kiln Dust on the Mechanical Properties of Cement Emulsified Asphalt Mortar Containing GGBFS and Fly Ash for High-speed Railway Ballastless Track

Cement asphalt emulsion mortar (CEAM) as a critical and complex engineering material for slab ballastless track is widely used in high speed railways and road pavements. Damping and cracking characteristics of CEAM are very important to resist vibration and the deformation caused by repeating loads. Furthermore, Cement is the fundamental constituent of CEAM, which is notorious for the environmental pollutant. Accordingly, reducing cement consumption has been a significant concern. This study evaluated the effects of using two types of supplementary cementitious materials (SCM), i.e. fly ash (FA) and granulated blast furnace slag (BFS) in corporating with cement kiln dust (CKD) as cement replacement, on the mechanical properties and cracking characteristics of cement emulsified asphalt mortar. To reach the objectives of the study, different experimental tests (i.e. Uniaxial Compressive strength (UCS), indirect tensile (IDT) strength, Moisture susceptibility and semicircular bending (SCB)) were conducted. The results showed that the replacement of 30 percent of cement by fly ash leads to significantly improve the compressive strength and indirect tensile strength of prepared CEAM. Furthermore, all the proposed CEAM containing different percentages of SCMs had ITSR more than 0.8 which pass the standard requirement. The consequences of CEAM cracking resistance indicated that the 30 percentage replacement of cement by BFS considerably enhanced the J-integral of CEAM which results the better cracking resistance of prepared mixture. Moreover, the replacement of 50 percent of cement in CEAM by supplementary cementitious materials revealed that the proposed CEAMs had proper unconfined compressive strength, capability to resistance against crack initiation and propagation and also sufficient endurance against moisture failure. Finally, it can be concluded that the examined CEAMs in this study can be presented as eco-friendly CEAM which had enough resistance against the repeated train and varying environmental loadings.