A novel Cold Rolled Asphalt mixtures for heavy trafficked surface course

Abstract

Hot Rolled Asphalt (HRA) surface course is a gap-graded mixture of coarse aggregate, sand, mineral filler and bitumen. The mechanical properties of the mixture are dominated by the strengthening properties of the mortar components, i.e. mineral filler, sand and bitumen. The material is extensively used for surfacing major roads in the UK because it provides a dense, impervious layer, resulting in a weather-resistant durable surface able to endure the demands of modern traffic loads and providing good resistance to fatigue cracking. However, it may experience some weakness in deformation resistance.Cold Bitumen Emulsion Mixture (CBEM) provides valuable advantages over hot asphalt mixtures in economic and environmental terms. The total energy required for mixing, transportation and laying such mixtures is lower compared with the traditional hot mixtures.This paper describes the development of a new, fast curing gap-graded Cold Rolled Asphalt (CRA) through replacement of conventional mineral filler with a Binary Blended Filler (BBF) generated from blending different percentages of two different waste fly ashes. The new CRA is found to be comparable with the traditional Hot Rolled Asphalt (HRA) after short periods of curing. The mechanical properties were assessed by stiffness modulus and uniaxial creep tests while water sensitivity was inspected by evaluating the stiffness modulus ratio before and after sample conditioning.The experimental results show a significant improvement in the mechanical properties and a substantial upgrading of material resistance to water sensitivity by the incorporation of BBF in the CRA. Moreover, the required strength i.e. 125 pen HRA stiffness modulus can be achieved after just several hours from de-moulding which represents a significant advantage when compared with the conventional reported curing times of 2–24months for the traditional CBEMs.