Effect of Lime Addition Methods on Performance Related Properties of Asphalt Concrete Mixture

In the recent years, some of the newly constructed asphalt concrete pavements in Baghdad as well as other cities across Iraq showed premature failures with consequential negative impact on both roadway safety and economy. Frequently, load associated mode of failure (rutting and fatigue) as well as, occasionally, moisture damage in some poorly drained sections are the main failure types found in those newly constructed road. In this research, hydrated lime was introduced into asphalt concrete mixtures of wearing course in two methods. The first one was the addition of dry lime on dry aggregate and the second one was the addition of dry lime on saturated surface dry aggregate moisturized by 2.0 to 3.0 percent of water. For each type of addition, five different percentages of lime as a partial replacement of ordinary limestone mineral filler were used; these were; 1.0, 1.5, 2.0, 2.5, and 3 percent by weight of aggregate besides a control mixture that did not contain lime. Marshall Mix design method was used and the performance properties of moisture damage, resilient modulus, permanent deformation and fatigue characteristics were evaluated using indirect tensile strength, uniaxial repeated loading and repeated flexural beam tests. Also, VESYS5W software was implemented to evaluate the pavements performance in terms of rut depth and fatigue area for a typical pavement structure. The main conclusion withdrawn from this research revealed that the use of 2.5 percent hydrated lime in dry addition method and wet addition method showed an improved fatigue and permanent deformation characteristics, lower moisture susceptibility and high resilient modulus