Influence of chemical additives on mixing procedures and performance properties of asphalt emulsion recycled mixture with reclaimed cement-stabilized macadam

Abstract

During rehabilitation of pavement structure with cement-stabilized macadam (CSM) base course and hot mix asphalt (HMA) surface course, it is expected to recycle severe cracked CSM layer using the same method as HMA layer. In this study, asphalt emulsion and chemical additives were adopted to stabilize reclaimed CSM aggregates. Considering the surface characteristic of the CSM aggregate, the addition procedures of chemical additives were investigated by volumetric parameters and strength tests. The moisture susceptibility and rutting resistance test were conducted to evaluate effect of different chemical additives on performance properties of the recycled mixture. To understand the mixing procedures and performance characteristic, the microstructure images of the recycled mixture were observed by environmental scanning electron microscope (ESEM). The results of volumetric parameters and strength tests indicate the addition procedures of chemical additives affect the optimum composition and mechanical strength of the recycled mixture. It is recommended to add cementitious additives prior to asphalt emulsion during mixing process. Furthermore, the optimum composition and performance properties of the recycled mixture depend on types and content of chemical additives. Some suggestions are provided for the selection of chemical additives. The interface bonding mechanism between the recycled aggregates and cementitious materials is proposed to explain the mixing procedures and performance characteristic of the recycled mixture.