Utilizing polymers for asphalt concrete (AC) mixture modification has many drawbacks that hinder its wide implementations for roadway construction. Recently, research on employing complementary materials, such as nanomaterials, to balance negative impacts of polymers while enhancing the AC mixture’s performance has received great attention. This study aimed to investigate the effect of incorporating nanoclay (NC) particles on the performance of a high-density polyethylene (HDPE)-modified AC mixture. A 60/70 asphalt binder was first modified with HDPE, and then NC particles were gradually added at a concentration of 1–4% by weight of the asphalt binder. The binders’ physical characteristics, storage stability, and chemical change were scrutinized. AC mixture performance, including pseudo-stiffness, moisture damage resistance, stripping susceptibility, and rutting tendency, was investigated. A statistical analysis on the experimental results was conducted using Kruskal–Wallis and Dunn tests. Test results showed that employing NC/HDPE significantly increased penetration index and thereby enhanced binder temperature sensitivity. Moreover, it prevented oxidation action and separation and, therefore, enhanced binder storage stability. Furthermore, incorporating NC amplified pseudo-stiffness and significantly improved resistance against moisture damage and stripping of HDPE-modified mixtures. Moreover, it improved both elastic (recoverable) and plastic (unrecoverable) deformations of mixtures. The most satisfactory results were attained when incorporating 3% of NC.

Flexible pavements are susceptible to the damaging effects of moisture, causing various kinds of problems for asphalt such as stripping. That reduces the durability and serviceability life of pavements and consequently increases the construction and maintenance cost. The aim of this research is to study the moisture sensitivity of the hot asphalt mixture with high-density polyethylene as an asphalt binder modifier. Asphalt 60/70 was mixed with several concentrations of high-density polyethylene (HDPE) ranging from 2% to 8% by bitumen weight using a high shear mixer at a temperature of 180 0C and a speed of 4000 rpm for 60 minutes. Penetration depth, softening point, rotational viscosity (RV), and scanning electron microscopy (SEM) tests were performed on both the conventional and HDPE-modified binders. Asphalt mixtures were designed according to the Egyptian specifications using the Marshall method. Conventional and HDPE-modified asphalt mixtures' moisture susceptibilities were evaluated through indirect tensile strength (IDT) and loss of stability tests. Results of scanning electron microscopy (SEM) showed that HDPE was homogeneously dispersed through the binder with no polymer cluster formations. Testing results revealed that adding high-density polyethylene at a

 I. INTRODUCTIONRADITIONAL asphalt needs further improvements due to many problems, such as moisture susceptibility, debonding, and permanent deformation [1][2][3]. Recently, the use of nanomaterials to improve the performance of asphalt binder and hot mix asphalt (HMA) has become more widespread. Several kinds of nanoparticles have been used to modify HMA mixes, such as Nano-Carbon tubes, Nano-Clay (NC), Nano-Silica (NS), Nano-