Improving Behavioral Properties of Dispersive Clay by Addition of Incinerated Sewage Sludge Ash and Hydrated Lime

Document Type : Research Article


Faculty of Engineering, Central Tehran Branch, Islamic Azad University, Tehran, Iran



One of the methods to improve the quality of dispersive clays in order to reduce its washout tendency, is to add lime with the proportion of 4% in construction projects. Besides, addition of lime will lead to stabilization of the soil further more. Therefore, if the stability of soil in of concern, some portion of soil may be replaced by lime.
In this paper, the incinerated sewage sludge ash (ISSA), mixed with hydrated lime by appropriate proportions and with regard to the duration of curing process, was used to improve specifications and parameters of dispersive clay; then, effect of this mixture on unconfined compressive strength relying on the dispersive properties of soil and the curing process of the combination was investigated at different periods. The aim of this research is to investigate the cementation process of dispersive clay with the addition of ISSA and I.L mixture with respect to curing durations. Both mixtures were added to dispersive clay in 2, 4, 8 and 16 percent by weight. Also, the proportion of ISSA to hydrated lime is 4: 1 in weight.
Results of the tests showed that the unconfined compressive strength of the test specimens was increased by more than three times compared to the pure clay by adding hydrated lime and ISSA, indicating numerous potential applications of the mixture for soil improvement and administrative affairs in geotechnical engineering as well as practical applications in environmental geotechnical.


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