Evaluation of standard concretes containing enhanced-treated fluidized-bed waste incineration bottom ash as manufactured aggregate

Abstract

Circular economy can reduce natural resource consumption in construction, for instance by using manufactured aggregate from municipal solid waste fluidized-bed incineration bottom ashes instead of solely natural aggregates. The use of aggregate from this ash type in concrete is little investigated, particularly if it is derived from industrial-scale enhanced bottom ash treatment. This study presents an environmental and technical evaluation of concretes containing manufactured aggregate produced on industrial-scale from two Austrian fluidized-bed incineration bottom ashes. The results of the chemical analysis show that the manufactured aggregates complied with all limit values, with the exception of sulfate, which was 3215 mg/kg for the first and 3260 mg/kg for the second bottom ash. These values were higher than the lower limit value of 3000 mg/kg, but much lower than the higher limit value of 5,000 mg/kg. Then, concrete mixtures containing 12 and 20 wt% of manufactured aggregate were produced and evaluated. Two of the four concretes produced complied with all technical criteria for standard concrete C25/30. The compressive strength of all concretes was with 34.1–39.7 N/mm² higher than the limit value of 30.0 N/mm². One concrete showed alkali-silica reaction, while the particle size distribution of another concrete was out of the desired range. The crushed concretes were then analyzed with respect to environmental criteria for recycling material from demolition waste. These criteria were met by the concrete mixtures containing manufactured aggregate from the second bottom ash. By reducing the manufactured aggregate content in concrete from 12 wt% to 10 wt%, also the concretes with the first bottom ash should meet all criteria.