Behavioural Similarity between Marshall Stability and Indirect Tensile Strength Values for DBM Grade-2 using VG-30, VG-40 and CRMB-55 Grade Binder with RAP

Abstract: This research investigates the similarities between Marshall Stability and Indirect Tensile Strength (ITS) values for Dense Bituminous Macadam (DBM) Grade 2 mixes using VG-30, VG-40, and CRMB-55 grade binders, incorporating varying proportions of Recycled Asphalt Pavement (RAP). Virgin and modified mixes were prepared with RAP content ranging from 25% to 35% and bitumen content from 4.5% to 4.95 % .Marshall properties which includes stability, air voids, density, voids in mineral aggregate (VMA), and flow values were determined to establish optimal binder and RAP proportions for durable and sustainable pavements. For virgin mixes, VG-30,VG-40 and CRMB-55 grade binders exhibited optimal performance at 4.65% bitumen, achieving maximum stability values of 12.83 kN ,14.69 kN and 14.95kN respectively. Modified mixes with 25% RAP showed peak stability values of 14.40 kN, 14.90 kN, and 14.69 kN for VG-30, VG-40, and CRMB-55 binders, respectively, at optimal bitumen contents. Air voids minimized to below 4.34%, ensuring compactness, while flow values remained within permissible limits. At 30% RAP, VG-40 and CRMB-55 binders delivered superior performance with stability values of 15.24 kN and 15.29 kN, respectively. For mix with 35% RAP, VG-40 achieved maximum stability of 14.94 kN, while CRMB-55 demonstrated balanced results with a stability of 14.35 kN and optimal deformation resistance. Across all mixes, air voids reduced significantly, and densities remained consistent, ensuring structural integrity. The results demonstrate that incorporating RAP improves mix performance while promoting sustainability. VG-40 and CRMB-55 binders consistently outperformed VG-30, particularly at higher RAP contents, suggesting their suitability for durable and resilient pavement construction. This study provides a comprehensive understanding of the relationship between Marshall Stability and ITS values in DBM Grade 2 mixes, facilitating informed material selection for sustainable infrastructure. ITS follows the same trend as Marshall Stability, with CRMB-55 showing the highest values at 4.65% binder content (0.83 N/mm², 14.95 kN), followed by VG-40 and VG-30 for conventional Mix. For 25% RAP, VG-40 had the highest stability (14.90 kN), while CRMB-55 had the highest ITS (0.87 N/mm²). With 30% RAP, CRMB-55 exhibited superior stability (15.29 kN) and ITS (0.87 N/mm²). At 35% RAP, VG-40 had the highest stability (14.94 kN), while CRMB-55 led in ITS (0.85 N/mm²).