Experimental Investigation of Polymer-Modified Bituminous Stone Mastic Asphalt Mixtures Containing Cellulose Acetate Recycled from Cigarette Butts

Stone Mastic Asphalt (SMA) mixtures exhibit superior performance under traffic loads due to the high content of coarse aggregates; however, the high bitumen content also leads to the problem of bitumen drainage from the mixture. Several studies have been conducted on the use of stabilizing additives such as fibers, polymers, or mineral fillers to reduce binder drainage in SMA mixtures. In this study, however, an innovative and sustainable solution was developed to address the bitumen drainage problem encountered in SMA pavements and to improve the long-term performance of the mixture. In this context, the feasibility of using cellulose acetate (SG) material recycled from cigarette butts as an alternative fiber additive to the traditionally used cellulose fiber (SL) was investigated. This method aims to achieve both environmental benefits in terms of waste management and economic advantages in terms of additive materials. Additionally, the effect of using different SL contents (0.1%, 0.2%, 0.3%, 0.4%, 0.5%) on mixture performance was examined. Within this scope, both pure bitumen (B) and Elvaloy RET + PPA (E)-modified bitumen (1.6%, 1.7%, and 1.8% Elvaloy RET + 0.2% PPA) were used to produce both fiber-reinforced and non-fiber-reinforced SMA mixtures. Traditional and Superpave tests were conducted to determine the rheological and physical properties of the pure and modified binders. All SMA specimens were tested for Marshall stability and flow, Marshall quotient, indirect tensile strength (ITS), tensile strength ratio (TSR), Schellenberg bitumen drainage, sand patch, and Cantabro particle loss. Furthermore, a cost analysis was carried out to evaluate the economic effect of different fiber types and proportions. Among the SMA mixtures, the highest stability and resistance to moisture damage were achieved in the mixtures containing 1.6% Elvaloy RET + 0.2% PPA with 0.3-0.4% SG and 1.7% Elvaloy RET + 0.2% PPA with 0.3-0.4% SL, while the optimum surface texture depth was obtained in the mixtures containing 1.6-1.7% Elvaloy RET + 0.2% PPA with 0.3% SG. In conclusion, the Elvaloy RET + PPA modification enhanced the aging resistance of the bitumen, while the SG fibers used at 0.3-0.4% fiber content in the 1.6-1.7% Elvaloy RET + 0.2% PPA-modified series were identified as a promising mechanical and economic alternative to conventional SL fibers.