Design of dense graded cold bituminous emulsion mixtures and evaluation of their engineering properties

Abstract

A stable slow setting cationic emulsion has been developed, suitable to coat dense graded mixtures high in fine aggregate content, in particular gap graded rolled asphalt type and dense graded macadam mixtures. The slow setting emulsion, NH-10, is the outcome of an investigation into five different formulations using two surfactants, two adhesive agents and a water shading compound. The rheological studies of the NH-10 emulsion have shown that it possesses a thixotropic behaviour. The thixotropic behaviour has been justified by the "complex flow" coefficient, a technique proposed by Traxler for bitumens. The viscosity of the emulsion is greatly influenced by the amount of binder and level of temperature. The hardness of binder does not change appreciably the viscosity value of the emulsion. The highly stable mildly cationic emulsion has been used to prepare two types of dense bituminous mixtures containing limestone aggregate, river sand and limestone filler, blended in appropriate proportions. The study presents information regarding the properties of two dense graded bituminous mixtures i. e. a gap graded "Cold Rolled Asphalt" (C. R. A. ) and a continuously graded "Dense Emulsion Macadam" (D. E. Mc). A design procedure based on a modified Marshall method and the evaluation of permeability and creep stiffness is proposed as a laboratory method for the design of the bituminous mixtures developed. The evaluation of permeability and creep stiffness is carried out with equipment designed and developed specially for this investigation