Abstract
The Australian flexible road pavement network is experiencing a considerable degree of reveling and stripping damage in association with moisture. The next generation of hot mix asphalt (HMA) mixtures in Australia needs to have excellent engineering properties as well as higher resistance to moisture damage. Hydrated lime (HL) with a relatively high content of active lime is used in HMA mixtures to improve engineering properties, and particularly to enhance the resistance of HMA mixture to moisture. HL is currently considered a superior mineral filler to crushed rock baghouse dust but it is commercially produced and relatively expensive. Lime kiln dust (LKD) is an industrial by-product which has hydrated lime HMA filler-like properties with similar fineness and a relatively high content of active lime. The lime components in LKD assists in promoting resistance to the stripping common in siliceous acidic aggregates. This project aims to determine an optimum proportion of LKD in an LKD-asphalt binder mixture, based on the properties of viscoelasticity and aggregate adhesion. Dynamic shear rheometer testing and rolling bottle tests were used to evaluate the properties of the LKD-asphalt binder mixtures with varying LKD content. The test results indicated that a 50% LKD content in the LKD-HMA binder mixture provided superior viscoelasticity properties., an acceptable adhesion of asphalt to aggregates was also observed. Last but not the least, a ‘cradle to gate’ life cycle assessment was carried out to capture the benefits of the use of LKD by-product. This showed that GHG emissions and embodied energy demand could potentially be reduced by 18.5% and 2.4%, respectively if a 50% LKD asphalt binder by mass mixture was used in the LKD-HMA mix.
Highlights
Background and IntroductionThe construction industry consumes: 40% of natural materials, 40% of the total primary energy, 15% of the world’s fresh water resources, and generates 25% of all the wastes and 40 to50% of green house gas (GHG) emissions [1] ; the design team is charged to adopt an environmentally responsible approach to their design solutions and construction materials’specification choices. [1]
It is observed that the asphalt binders mixed with Hydrated lime (HL) results in the higher modulus than the one mixed with Lime kiln dust (LKD) at a replacement level of 30%
A ‘cradle to gate’ life cycle assessment carried out to capture the environmental benefits of the use of LKD in hot mix asphalt (HMA) shows that GHG emissions and embodied energy demand could potentially be reduced by 18.5% and 2.4%, respectively if LKD, which is 50% of bitumen, is used in HMA
Summary
Background and IntroductionThe construction industry consumes: 40% of natural materials, 40% of the total primary energy, 15% of the world’s fresh water resources, and generates 25% of all the wastes and 40 to50% of green house gas (GHG) emissions [1] ; the design team is charged to adopt an environmentally responsible approach to their design solutions and construction materials’specification choices. [1]. In the case of flexible pavements, asphalt (or bitumen), the binder used for the flexible pavement surface material of a multi-layered road pavement system accounts for a significant portion of the total life cycle GHG emission of the total pavement system. The use of asphalt during new road pavement construction and any maintenance stages will result an increase in the overall life cycle GHG emissions of the flexible pavement [1]. This paper highlights both the technical and environmental concerns associated with the use of AC mixture in pavement. AC as a surface material can be referred to hot mix asphalt (HMA)
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