Foamed concrete containing fly ash: Properties and application to backfilling

The use of foamed concrete (FC) with cement partially replaced by fly ash (FA) for urban abandoned underground-space backfilling was examined. The influence of density, water-binder ratio, and FA content on the mechanical and chemical properties of FC and on the surrounding environment was investigated in the laboratory and in the field. FC immersed in sulfate solution exhibited increased mass and compressive strength, as well as high resistance to sulfate attack. The maximum stress generated by FC on the original structure was 75.68 kPa; settlement variation was negligible. FC is thus a promising material that minimizes environmental effects of backfilling.