Sewage Sludge Bottom Ash Characteristics and Potential Application in Road Embankment

The paper focuses on sustainability-related applications in civil engineering by using environmentally friendly, alternative construction materials. The paper presents geotechnical properties of thermally converted, municipal sewage sludge in a grate furnace in an incineration plant. Bottom ash and its mixture with sand have been tested to show that they can be considered as a substitute for natural soil built-in road embankments. The product of sewage sludge combustion and its combination with sand meet all code requirements for material suitable for road embankments. As a result of the 30% reduction of resistance to failure values after waste soaking, which causes relatively low California Bearing Ratio (CBR) values of soaked waste, waste should be built into places isolated from groundwater and precipitation. That is also indicated by the possibility of heavy metals leaching from the waste because such content is much higher than in uncontaminated soils, although leaching does not exceed the limits commonly quoted for natural soil solutions. Tested bottom ash as a product of combustion in a grate furnace is a more preferred material for earthworks than fly ash generated during incineration in a furnace with fluidized bed due to the particle size and heavy metal concentrations.