The preservation of existing roadways by preventive maintenance is the most financially effective use of available resources ( Mamlouk and Zaniewski, 1999 Roberts et al., 1996). Emulsion mixes are also well adapted for cold in-place stabilization and recycling techniques because the aggregates need not be heated.įor developed countries, the environmental focus has shifted from pollution prevention to sustainable development. Placing the mix plant close to local raw materials and the job site maximizes the environmental benefit. Characterization of the binder from an emulsion-based warm mix ( Davidson et al., 2007 Takamura, 2008) confirms less age hardening of the binder than from hot mix, which should eventually result in less cracking.Ī cold mix plant using asphalt emulsion requires less initial capital investment than a conventional hot-mix plant, and is well suited for mobile use. Further environmental benefits accrue if recycled materials are used in the mix, and half-warm mix with emulsion has been used to recycle tar-containing road materials, avoiding hazardous emissions ( Dijkink et al., 2000). Lower mix temperatures mean a reduction in fuel consumption and consequent greenhouse gas emissions, and lower particulate and fume emissions ( Newcomb, 2007 Potti et al., 2006). The description “half-warm mix” has been used to distinguish warm processes where mixing takes place below 100 ☌, avoiding the need to dry the aggregate. Asphalt emulsions find use in warm mixes ( Crews, 2006) where mix temperatures are reduced to 60–120 ☌, and in cold mixes where the materials are generally unheated and mixed at ambient temperatures. New technologies, collectively known as warm mix asphalt, allow a reduction in the mixing and compaction temperatures ( Capitão et al., 2012 Newcomb, 2007). An important application in some countries is microsurfacing, in which a mixture of polymer-modified asphalt emulsion, fine grained aggregate, water, and cement is applied to the surface of an asphalt or cement concrete roadway from a mobile mix-paver to correct deformations, improve skid resistance, and seal the surface.Ĭonventional asphalt “hot mix” is generally produced at 150 ☌ or greater at the mixing plant, and subsequently compacted at around 120–140 ☌. The rest is used in asphalt mixtures prepared cold or warm, including in-place techniques. The major part is used in spray applications like chip seal, fog seals, and bond coats. ![]() Approximately 8 million tons of asphalt are used in emulsion form, about 9% of all asphalt usage ( Le Bouteiller and Roffe, 2011). The International Bitumen Emulsion Federation has collected some information on emulsion use in different countries. ![]() Consequently, processes using emulsions have lower energy consumption and lower emissions than those using hot asphalt or cutbacks (asphalt solutions in hydrocarbon solvents). The emulsions have significantly lower viscosity than asphalt itself, and so can be applied at lower temperatures. The emulsions may contain between 40% and 80% asphalt by weight. James, in Advances in Asphalt Materials, 2015 13.1 IntroductionĪsphalt emulsions are water-continuous dispersions of fine asphalt droplets, typically 1–10 μm in diameter, manufactured with the aid of a colloid mill.
0 Comments
Leave a Reply. |