Investigating and Analyzing the Shear Bond Strength of Modified SAMIs in Pavement Systems

Shear bond strength is a critical indicator of the bonding efficiency between pavement layers, playing a pivotal role in applications such as the stress-absorbing membrane interlayer (SAMI), which are designed to improve crack resistance and extend the life span of road pavements. This study explores the influence of two additives, low-density polyethylene (LDPE) and cement kiln dust (CKD), on the shear strength and stiffness of SAMI blends. Various proportions of LDPE (2%, 4%, and 6%) and CKD (4%, 8%, and 12%) were incorporated into SAMI formulations, and their effects were assessed using a specialized shear bond strength test. The findings revealed a progressive increase in peak shear strength, maximum shear strain, and stiffness with higher additive concentrations. SAMI blends containing LDPE exhibited the highest shear strain, along with superior ductility and flexibility when compared with the control blend, where the maximum shear strain occurred in the blend with 6% LDPE, reaching 0.042, compared with 0.037 for the control blend. Notably, the blends containing both LDPE and CKD demonstrated the best performance, achieving the highest peak shear strength of 0.58 MPa and stiffness of 0.2 MPa/mm, outperforming the control blend (0.34 MPa and 0.096 MPa/mm). Furthermore, these blends showed enhanced energy-absorption capacity, as indicated by the area under the shear strength-displacement curve before and after reaching peak shear strength. The blend containing 4% LDPE and 8% CKD achieved a total area of 9.29 MPa.mm under the curve, compared with the 6.3 MPa.mm of the control blend. In conclusion, the incorporation of LDPE and CKD into SAMI blends resulted in significant improvements in mechanical properties, offering a possible lower risk of reflective cracking and the potential for longer pavement life.