Mechanical and Microstructural Study of RAP–Clay Composites Containing Bitumen Emulsion and Lime

Abstract

Full-depth reclamation of asphalt pavement and underlying materials is one of the most effective methods of rehabilitation for severely deteriorated roads. This paper examines the feasibility of using clay at different percentages in a recycled mixture with bitumen emulsion and lime at relatively higher dosages than those specified in previous studies. The most important mechanical tests included indirect tensile strength in dry and wet conditions, resilient modulus, and indirect tensile fatigue tests. Also, microstructural analyses were performed using scanning electron microscope and X-ray diffraction methods on cured pastes of various combinations of clay, bitumen emulsion, and lime. Based on mechanical tests, the addition of clay up to 10% would not have any destructive effects on stabilized specimens. In addition, specimens containing 10%–15% clay showed acceptable behavior. Specimens with higher clay contents showed some deficiencies in mechanical and durability tests. Microstructural analyses have shown that additives like lime and emulsion, which usually play the role of binder in such mixes, work independently, and the simultaneous use of lime and emulsion would not lead to a new composite binder. However, the presence of emulsion may delay the development of clay–lime reaction and therefore the curing progression of the stabilized layer.