Production of an Eco-friendly Stone Matrix Asphalt Mixture Using Recycled Additives

Premature failure of hot mix asphalt (HMA) pavements in Iraq is typically caused by heavy loading, which requires frequent maintenance. Several approaches should be developed to prevent such failure and construct efficient and cost-effective pavements. In this study, a stone matrix asphalt (SMA) mixture is suggested as an alternative to reduce the damages in terms of rutting resistance and prolong the pavement's service life. The SMA is a gap-graded mix of two ingredients, asphalt mortar and coarse aggregate. This study aims to design and evaluate SMA mixtures utilizing two kinds of asphalt binder (virgin and modified) and a stabilizing agent. Crumb rubber (CR) is a type of recycled rubber utilized as a binder modifier with four mixing proportions (5, 10, 15, and 20%). On the other hand, cellulose fiber pellets (CFP) are plant-based waste materials utilized as stabilizing agents with four percentages (0.2, 0.3, 0.4, and 0.5%). It is believed that incorporating these wastes into asphalt mixtures significantly impacts the environmental footprint. The generated Superpave SMA mixtures are assessed regarding their mechanical characteristics (air voids, voids filled with asphalt, and voids in mineral aggregate). Several lab tests were conducted to evaluate the performance of the produced SMA mixtures, including a drain-down test, tensile strength ratio (TSR) test, resilient modulus (MR) test, and flexural fatigue test. The findings indicated that the SMA mixtures with (0.4% CFP + 15% CR) had superior resistance to permanent deformation and moisture damage. In addition, at (0.4% CFP + 15% CR), the SMA mixtures achieved the lowest drain-down value and the highest resistance to flexural fatigue against the control mix.