Effect of incinerator bottom-ash composition on the mechanical behavior of backfill material

This study explores the influence of the chemical composition (SiO2, CaO, Fe2O3, and Al2O3) of incinerator bottom ash on its friction angle. Direct shear tests were performed to measure the strength of bottom ash with two distinctly different compositions. Then, an empirical equation was regressed to determine the correlation between each composition and the friction angle. The experimental results showed that the main constituent material of the incinerator bottom ash from general municipal wastes is SiO2, and the friction angle is 48.04°–52.66°. The bottom ash from incineration plants treating both municipal wastes and general industrial wastes has a high content of iron–aluminum oxides, and its friction angle is 44.60°–52.52°. According to the multivariate regression analysis result, the friction angle of bottom ash of any composition is influenced mainly by the Fe2O3 and Al2O3 contents. This study used the friction angle of the bottom ash from four different incineration plants to validate the empirical equation, and found that the error between actual friction angles and the predicted values was −1.36% to 5.34%. Therefore, the regressed empirical equation in this study can be employed in engineering applications to preliminarily identify the backfill quality of incinerator bottom ash.

The contour map of chemical composition and friction angle can be drawn according to the results of experiment and multivariate regression analysis, as shown in Fig. 5. In drying conditions, the engineering properties of incinerator bottom ash are mainly influenced by Fe2O3 and Al2O3. In order to make the incinerator bottom ash have larger friction angle during filling, the Al2O3 content should be controlled below 15%. A higher Fe2O3 content indicates larger friction angle, thus, the incinerator bottom ash can have better engineering properties.Figure optionsDownload as PowerPoint slideHighlights
► We explore the influence of chemical composition on the friction angle of bottom ash.
► The friction angle of bottom ash is influenced by Fe2O3 and Al2O3 constituents.
► An empirical equation was proposed for the engineering application of bottom ash.
► The error between actual friction angles and the prediction was −1.36 to 5.34%.