Application of Sewage Dry Sludge as Fine Aggregate in Concrete

The present work has been performed to eliminate sewage dry sludge of Alborze city wastewater treatment plant by using them as fine aggregate in concrete. On this basis, at first the selected dry sludge was analyzed for XRD and XRF for crystalline phases and chemical composition, respectively. The results showed that more than 50% of the sludge is formed of SiO2 and it had more than 20% organic materials. The presence of organic materials can potentially decrease the performance of concrte, so, the dry sludge exposed to heating process. The crystalline phases of the sludge were evaluated after heating using XRF analysis. The results revealed the remove of organic materials and some changes in crystalline phases. Due to changes in crystals, formation of pozzolanic activity was measured using TGA analysis. To study the effects of dry sludge on concrete mechanical properties (compressive strength) two mix designs with water to cement ratios of 0.55 and 0.45 was produced. The sludge amount used in concrete was 0, 5, 10, 20 and 30%. The compressive strength was studied as an important factor in durability studies. Results showed that 90 days cured specimens containing 5, 10 and 20% dry sludge had 4, 8 and 22% decrease in compressive strength in comparison to control specimens.