Use of foamed asphalt in recycling incinerator ash for construction of stabilized base course

Abstract

Use of incinerator ash in construction of highway pavement layers may have the potential to significantly reduce the quantity of ash that must be disposed of. However, the physical properties of ash are not optimal for construction of normal asphalt pavement. When designed and applied properly, foamed asphalt provides a way of obtaining good coating on granular materials made from ash and hence adequate cohesion of pavement materials. Also, foamed asphalt provides a way of using materials with relatively high percentage of fines and moisture content. This paper briefly reviews foamed asphalt and its use, production of aggregate from incinerator ash, and describes design, construction, and evaluation of a parking lot pavement using foamed asphalt-treated ash. Based on the results obtained from mix designs it was recommended that 2% lime be added to a mix with 100% ash (at optimum moisture content), and that 1% lime be used when 75% ash is combined with 25% recycled concrete-the recycled concrete being minus 12.5 mm material. For both 100% ash and the combination of 75% ash and 25% recycled concrete (minus 12.5 mm material) a design foamed asphalt content of 4.5% was recommended. Laydown and compaction of experimental foamed asphalt treated recycled ash mix was completed without any major problems. Results of Benkelman beam test showed that the foamed asphalt treated recycled ash mix layer cured and gained adequate stiffness within a period of 24 h.