Research Information System
15th International Multidisciplinary Scientific Geoconference (SGEM), Albena, Bulgaria, 18 - 24 June 2015, pp.589-596
In the last decades, the recycling of waste materials has gained considerable importance due to issues related to their ecological effects and storage. This issue is particularly crucial when dealing with hazardous waste materials such as sewage sludge. Sewage sludge is a waste material discharged from sewage treatment plants. Recently, the management of sewage sludge has become more critical in crowded cities where huge amounts of sewage sludge are produced every day. In this sense, the recycling of sewage sludge is of great importance for a sustainable environment. This study investigates the re-use of sewage sludge filter cake in cement mortar as a construction material. Accordingly, in this paper the mechanical properties of filter cake added mortar samples that comprises of sand, cement, water and admixtures such as fly-ash, silica fume and lime have been investigated. Preliminary studies indicate that addition of sewage sludge causes a delay in the setting time of mortar. To improve the time of setting, two different types of lime were added to the mortar mixtures. The addition of filter cake resulted in a decrease in both compressive strength and tensile strength. As a result, fly-ash and silica fume were added to the mortar mixture. Accordingly, eight different mortar mixtures were prepared and cast into formworks with a size of 40 mm x 40 mm x 160 mm. Flow table, capillarity, flexural strength and compressive strength experiments were conducted on these samples. For each type of experiment, nine samples out of each mixture were prepared and the arithmetic mean of the test results were taken. Flexural strength and compressive strength experiments were performed at 14, 28 and 56 days of age of mortar. In order to determine the capillarity coefficient, capillarity tests were conducted on samples at 28 and 56 days of age. The results indicate that the addition of sewage sludge delays the time of setting and decreases workability. However, the addition of lime helps to minimize this adverse effect. On the other hand, although the addition of silica fume and fly-ash results in lower strength in the early stages, the compressive and flexural strength increase rapidly and consistently with time compared to the other samples. In the light of the experimental results, it is concluded that the use of sewage sludge filter cake in cement mortar is not only an efficient way to recycle a waste material but also a convenient way provided that the amount of sewage sludge and the other admixtures are adjusted in an optimum manner.