Optimization of Recycled Asphalt Pavement in Cold Emulsified Mixtures by Mechanistic Characterization

Abstract

As road infrastructure development has witnessed a steep increase across the globe, it is adversely affecting the environment attributable to unabated extraction and use of stone aggregates, a fast depleting natural resource. This situation has led to a serious ecological problem and requires alternative techniques for obtaining a sustainable pavement such as use of cold mix recycled asphalt pavement (RAP) technology with bitumen emulsion. Techniques like this have proved that they make a positive impact on both economic and environmental conditions. The main objective of this study is to evaluate emulsified mixtures incorporating RAP, which is a typical task attributable to the complexity by heterogeneity of materials. The study recommendations are on the basis of comparison of laboratory performance of emulsified mixtures: without RAP, as a control mixture; and with RAP, containing 30–80%. The study involved understanding the physical characterization of materials, followed by developing mix designs for both conventional cold mix and mixes with varying percentages of RAP content. Indirect tensile strength (ITS) is used as an indicative measure for cold recycled emulsified mixtures (CREMs) during mix design. Laboratory tests, including tensile strength ratio (TSR), moisture induced susceptibility test (MIST), resilient modulus, rutting, creep, and fatigue tests, were conducted for the performance evaluation of the mixtures with and without RAP. The obtained results indicated that the CREMs are superior to conventional cold mixtures in mechanical performance. Among the varying RAP proportions, mixes with 60% RAP showed optimal results indicating that it is possible to design high-quality bituminous mixes incorporating considerable amount of RAP that meets the desired volumetric and performance criteria.