Performance of Alum Sludge as partial replacement for cement adding superplasticizer

The production of alum sludge from waste water treatment plant is increasing all over the world. Disposal of alum is becoming a serious environmental problem. Another alarming issue is attributed to the high usage of concrete in the construction industry where concrete is one of its main material. This will lead to increased cement production and emission of carbon dioxide emission. Hence, the research for replacement of cement by alum sludge is essential to reduce both the emissions of carbon dioxide and the disposal problem of alum sludge. An attempt has been made to investigate the use of sewage sludge ash as partial cement replacement in concrete. The alum sludge is incinerated at the temperature of 600 and a duration of 3hours.The incinerated alum sludge is sieved through size of 150. Four different percentages of 5%, 10%, 15% and 20% of alum sludge (AS) is used to replace the cement in the concrete. XRD and XRF tests were carried out to determine the similarity component present in the AS. Water absorption test and slump test has also been carried out to check the capacity of water absorption, durability and workability of the AS concrete. The compressive strength of AS concrete is also determined through rebound hammer and compression test. Result show that AS has the potential to replace cement as the major chemical component of AS is similar to that of cement.10% of AS concrete shows a lower absorption value than the control sample which shows that 10% SSA would have a better durability. However, an increase in the percentage of AS decrease the workability and compressive strength and yet, the 10% AS concrete possesses compressive strength higher than 25N/mm2 which can be applied in structural application. The findings suggested that the suitability of alum sludge concrete in different cement replacement ratio is applicable for different usage. The application of alum sludge in concrete will directly reduce the quantity of the cement used which also decreases the emission of carbon dioxide and solving the disposal problem of alum sludge.