Characterization and Use of Sewage Sludge Ash as Supplementary Cementitious Material for Concrete

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Addis Ababa University


Disposal of sewage sludge is becoming a serious environmental problem. The incineration process is able to reduce the volume of sewage sludge. It is not a proper solution, so the sewage sludge ash generated after the incineration process, and it must be disposed to landfill. The general objective of this study was to investigate the properties and use of sewage sludge ash as supplementary cementation material for concrete. Sewage sludge was incinerated at temperature of 600 ºC and 800 ºC for 3 & 2.5 hours. The incinerated sewage sludge ash was sieved through size of 75 µm and investigates physical properties, and chemical compositions of sewage sludge ash were carried out. SSA is pozzolanic material satisfied the requirement of ASTM C618. Chemical composition of SSA incinerated at 600 ºC and 800 ºC were determined by Atomic Absorption spectrometer. AAS test has shown that the sewage sludge ash contained primarily these oxides such as SiO2, Al2O3, Fe2O3 and CaO. The concrete specimens were prepared using 5 %, 10 %, 15 %, and 20 % of the two temperatures incinerated sewage sludge ash that is 600 ºC and 800 ºC, and design mix ratio of 1:2:4 with w/c ratio was 0.82. The cubic mold size of 10 cm x 10 cm x 10 cm was used to produce a concrete specimen, and the concrete tests have then been measured both at the fresh and hardened concrete. In the hardened concrete, the results of a concrete have shown that 600 ºC SSA 5% & 800 ºC SSA 10% replacement of OPC by sewage sludge ash achieved a higher compressive strength than the others percentage of set in this research at the age of the 28 days as compared with the control concrete (0 % SSA). The percentage of water absorption increased with increase in sewage sludge ash that incinerated at temperature of 600 ºC & 800 ºC, and all the blended (% SSA) concretes have shown a higher amount of water absorbed as compared with the control concrete (0 % SSA).



Incineration, Sewage sludge ash, Characterization, Percentage of replacement, Concrete