Date of Award

Fall 2026

Abstract

Cold recycling technologies provide a sustainable approach for pavement rehabilitation by reusing existing materials while reducing the consumption of virgin resources, transportation requirements, production temperatures, and construction-related environmental impacts. However, the mechanical response of cold recycled mixtures (CRM) differs from that of both conventional hot mix asphalt and unbound granular materials and is influenced by material composition, volumetric characteristics, confinement, curing, and stress state. These characteristics create uncertainty regarding material selection, mechanical characterization, and the prediction of the structural contribution of cold recycled layers. Further opportunities to enhance the sustainability of cold recycling lie in the incorporation of alternative recycled resources. Research is therefore needed both to evaluate the suitability of such materials for cold recycling applications and to improve the translation of laboratory-derived CRM properties into pavement-level performance predictions.The primary objective of this dissertation is to advance the understanding and performance-based evaluation of CRM by examining how material composition and constitutive representation influence mechanical response and pavement performance. The research addresses two complementary areas. The first evaluates the feasibility of using recycled asphalt shingles (RAS) as a mechanical stabilizer in full-depth reclamation (FDR). Two FDR materials were combined with different RAS sources, contents, and processing levels. The experimental program included gradation and volumetric characterization, indirect tensile strength and moisture susceptibility, triaxial resilient modulus, and triaxial shear strength testing. Conventionally processed and minimally processed post-consumer RAS were compared to determine whether extensive grinding and resizing are necessary for FDR applications. The laboratory investigation was complemented by mechanistic-empirical (M-E) pavement performance analyses using MnPAVE design software, a comparative life-cycle assessment, an initial material cost analysis, and a life-cycle cost analysis. The second research area evaluates the pavement-level implications of active-filler-induced changes in CRM mechanical properties and the influence of the constitutive representation adopted for cold recycled layers. Laboratory-derived stiffness and shear strength properties of CRM stabilized with bitumen emulsion or foamed bitumen and incorporating cement or hydrated lime were used in M-E analyses performed with KENLAYER design software. The CRM layer was represented using either a linear elastic or a stress-dependent nonlinear constitutive representation. The two approaches were compared in terms of predicted HMA fatigue cracking, subgrade rutting, Deviator Stress Ratio (DSR) within the CRM layer, and pavement fatigue life ratio. The findings demonstrate that RAS can be used as a mechanical stabilizer in FDR, provided that its compatibility with the host material is considered. Minimally processed RAS may reduce processing requirements and provide a higher-value application for roofing waste without necessarily compromising material performance. The analyses also show that active fillers modify both stiffness- and strength-related properties and that stiffness alone does not provide a complete representation of the structural contribution of CRM. CRM-specific mechanistic indicators relating traffic-induced stresses to mixture-specific shear resistance can therefore complement conventional pavement fatigue and rutting criteria. Furthermore, the constitutive representation of the CRM layer can influence predicted pavement performance and the estimated structural benefit associated with changes in mixture composition. Overall, this dissertation supports a more integrated and performance-based evaluation of CRM by connecting composition, mechanical properties, stress-dependent behavior, and pavement-level response.

Document Type

Dissertation

First Advisor

Eshan Dr. Dave

Second Advisor

Mohamed Dr. Elshaer

Third Advisor

Elena Dr. Romeo

Department or Program

Civil and Environmental Engineering

Degree Name

Doctor of Philosophy

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