Artificial aggregate made by cementitious granulation of waste incinerator fly ash

The waste employed in this work comes from an incineration plant in which municipal, hospital and industrial wastes are treated. The plant is equipped with rotary and stoker furnaces and both fly ash samples coming from these two equipments have been individually employed. Ash from waste incineration plant is classified as hazardous and cannot be utilized or even landfilled without prior treatment. This paper reports the results of an extensive investigation on stabilization/solidification of the above ash samples by addition of hydraulic binders in a granulation equipment. A rotary plate granulator was used with binders based on cement, lime and coal fly ash. Granulation was carried out with several mixes in which the ash content was up to 70%. In some cases, the granules obtained in this way are suited for matter recovery by reusing the waste for the manufacture of building materials. To achieve this in most cases, two-step granulation is required with pure binder being used in the second one. In this way the granules from the first step can be encapsulated within an outer shell able to improve the technological and leaching properties. The possibility to get matter recovery from incinerator ash is a crucial issue for making the granulation process environmentally and economically sound. In fact, the most direct application of granules is in the field of artificial aggregates for road construction and concrete manufacture. The granules obtained from the treatment of fly ash samples have been tested to assess their physico-mechanical and leaching properties. Specifically, measurements have been carried out regarding the following properties: density, water adsorption capacity, compressive (crushing) strength and leaching behavior. Moreover, concrete mixes have been prepared with some of the artificial aggregates made by granulation. Once hardened, these mixes have been successfully tested from the technological point of view, proving to be suitable for the manufacture of classified concrete blocks.