Investigating the Effect of Origin and Heating Temperature on the Properties of Sewage Sludge Ash (SSA) and the Feasibility of Using in Construction Materials

With the development of the human community and increasing number of treatment plants, the treatment and disposal of high volume of sludge requires efficient management. Nowadays, due to the lack of land for burying sludge and environmental limitations of using sludge in agriculture, incineration is considered as a proper solution for sludge disposal. Sewage sludge ash is one of the materials that has been used in recent years as a substitute for cement and stone materials in concrete and construction materials.The quality of the resulting ash depends heavily on the origin of the sludge and its incineration process. Regarding this, there is no codified information about the content of the sludge of Tehran wastewater treatment plants, with considering its usage in construction materials. Also, there are many discrepancies in the heating process and the optimal incineration temperature of sewage sludge ash in the sources. In the first step, by examining the sludge of Tehran wastewater treatment plants and performing chemical analyzes such as XRF and XRD, the best treatment plant in terms of constituent content was selected. Then, by burning sewage sludge at 700 to 1000 C and re-analyzing XRF and XRD, as well as calculating the percentage of pozzolanic activity of the resulted ash, the most optimal heating process was selected.The obtained results of this study indicated that heating the Shahrake Gharb wastewater treatment plant's sludge at 800°C produced the most desirable sludge ash in case of chemical composition and pozzolanic activity. So, in general, it can be seen that although sludge ash could not be classified as one of the types of strong pozzolans, but this ash can be used as a raw material for Portland cement production and also as a weak pozzolan in reactions. Therefore, it is possible to replace the sewage sludge ash in optimal percentages in the mortar and concrete with Specified applications and as an alternative to cement, fine aggregate and filler.