USE OF SEWAGE SLUDGE ASH AS A CEMENT REPLACEMENT IN CONCRETE: A REVIEW

Rapid development of the countries in the world and increase in population will increase the production of sewage sludge. Sewage sludge is a waste product from the sewage treatment plant processes. The sewage treatment plants are processing large volume of wastewater every day in order to control the quality of the effluent before released to the river.  Instead of disposing the sewage sludge at landfill, using sewage sludge as a recycle material could minimize the need for new disposal area and reduce the negative impact to the environment. Thus, many studies have been conducted to utilize the sewage sludge ash as a recycle material. This paper reviews the usage of sewage sludge ash as cement replacement in concrete production. Sewage sludge ash is a powdered material that contains high percentage of SiO2, Al2O3, Fe2O3, CaO, P2O5 and SO3, and has shown moderate reactivity in terms of pozzolanicity. Most of the researchers burned the sewage sludge to the temperature range between 600 °C - 900°C to produce sewage sludge ash. The partial replacement of cement by sewage sludge ash promoted an increase in the compressive and flexural strength of concrete. Meanwhile, the replacement of 5 % sewage sludge ash by weight of cement considered as an optimum content in order to obtain the best mechanical performance of concrete. Furthermore, the workability of concrete after 28-days were improved with the addition of SSA.