Journal of Alasmarya University: Basic and Applied Sciences Vol. 6, No. 5, December 2021, Special Issue for Forth Conference on Engineering Science and Technology (CEST-2021) علومسورية: الهعة الجا هجلة اسية والتطبيقيةسا ا اوجلذ ل6 ، العذد5 ، ديسوبر0202 ، ( وم الهندسية والتقنيةلعللمؤتمر الرابع ل عدد خاص باCEST-2021 ) ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ ـــــــــــــــــــــــــــــ ــــــــــــــــــــــــــــــــــــــــــــــــــــ 681 ISSN: 2706-9524 (Print) ISSN: 2706-9532 (Online) Effect of Soft Clay on the Volumetric and Mechanical Properties of Hot Mix Asphalt Allam Musbah Al Allam 1,* , Ahmed Suliman B. Ali 2 , Hassan M Hassan Ali 3 , and Isa Ali Almuhktar 4 1 Engineering and Information Technology Research Center, Bani Walid, Libya 2 Research Centre for Soft Soil (RECESS), Universiti Tun Hussein Onn Malaysia, Malaysia 3 Faculty of Natural Resources University of Aljufra, Libya 4 College of Technical Sciences Bani Waled, Libya ABSTRACT Abstract. To define the behaviour of asphalt mixture including various penetration grade bitumen has been a major subject of paving engineering. This search investigated the volumetric and mechanical properties of a hot-mix asphalt (HMA) mixture with the Superpave mix design. The mixture was added with powdered soft clay at five different percentages based on the bitumen weight (0%, 2%, 4%, 6%, and 8%). Performance tests were then conducted to determine the resilient modulus and volumetric properties of the mixture. Results show that bulk specific gravity increased after adding soft clay to the asphalt mixture. The amount of air and mineral aggregate voids also decreased with increasing SC contents. Furthermore, the addition of 4% SC improved mixture stiffness, as determined through indirect resilient modulus test under aging conditions. Therefore, soft clay can be added to asphalt mixtures to improve their volumetric and mechanical properties, such as strength and durability. Keywords: Volumatic Properties. Superpave Mix Design. Stiffness Soft Clay. Aging Method. *Corresponding Author Email: alallm84@yahoo.com 1 INTRODUCTION Through the last decades by growing number of vehicles and weights on roads, road pavement has been subjected to greater damages which in numerous cases happened even prior expecting pavement service life. Moreover, the pavements should be maintained under adequate structural, geometric, and signaling conditions to prevent accidents and ensure safe transportation [1]. Approaches for developing pavement designs gradually shift from traditional pavement designs to mechanistic designs. A successful mechanistic approach can be obtained by elucidating the behavior of material properties [2].