Modeling the Impact of Binder Type and Nano Additives on Creep Stiffness of Green Asphalt Binder

When the environment temperature reaches a critical value below the freezing limit which is known as (critical cracking temperature), the thermal stresses exceed the stability of the material, and thermal cracking occurs.Thermal cracking is a serious distress type and exhibits a serious negative influence on the performance of flexible pavement, since rainwater may penetrate freely in the pavement structure and accelerate the deterioration process as the traffic loading proceeds through the service life of the pavement.The flexural-creep stiffness of asphalt cement binder is considered as a good indicator of the resistance to thermal cracking of the binder at low temperature.It is usually measured with the aid of Bending Beam Rheometer (BBR).In the present assessment, the influence of Nano additives (silica fumes and fumed silica) on creep stiffness was evaluated and modeled.Such additives were implicated to obtain the green binder.Conventional asphalt cement binder with penetration grades (40-50) and (60-70) were assessed.It was detected from the experimental program that modification of the conventional binders with Nano additives exhibit significant control on the creep stiffness and the developed power mathematical models gave the best experimental fit, exhibit a high coefficient of determination, and are recommended to predict the impact of Nano additives on the creep stiffness of asphalt binder.It was noted that the creep stiffness of (60-70) binder is harder than that of (40-50) binder by (21.5 and 20) % at the initial point of loading and at failure respectively.The creep stiffness of (40-50), and (60-70) green asphalt binders treated with fumed silica is higher than that of control binder by (25 and 12.5) % at failure respectively.While the creep stiffness of (40-50), and (60-70) green asphalt binders treated with silica fumes is higher than that of control binder by (35 and 17.8) % at failure respectively.It was concluded that Nano additives are recommended to control the creep stiffness of green asphalt binder regardless of the sol and gel types of the conventional (60-70) and (40-50) binders.