Characterization and Optimization of Incinerated Municipal Solid Waste Fly Ash as a Cement Substitute Material in Concrete at Reppie Waste to Energy Plant, Ethiopia, East Africa

Incinerated municipal solid waste fly ash is a byproduct of Reppie Waste to Energy Plant Technology found after generation of power and electricity. The disposal of this ash in the form of particulate matter is already causing serious environmental problems to the city. This research was, therefore, conducted to examine the potential of incinerated municipal solid waste fly ash as a cement substitute material. The incinerated municipal solid waste fly ash of Reppie waste to energy plant after silicate analysis was investigated for the major chemical composition to test the requirement of ASTM C 618 artificial pozzolanic property of class C. This makes it possible to the partial replacement of cement in concrete structure for the construction industry. The samples of this fly ash were arranged in a random and design mix ratio of 1:2:3 with a maximum 0.45 water-cement ratios following EBCS-2, 1995 [1] to survey compressive strength tests, tensile strength, density test, and water absorbency tests. The test result of compressive strength showed that, up to 13.6% substitution of the standard Ordinary Portland Cement (OPC) by incinerated municipal solid waste fly ash in concrete gratify the targeted compressive strength requirement at 28 days of curing period. While more than 15% of the substitution showed lower compressive strength at 28 days for M-30 grade of concrete but it works for other grades of the simple concrete structure. Therefore, it can be concluded that 13.6% replacement of cement by incinerated municipal solid waste fly ash resulted in nearly 30 MPa compressive strength which satisfies the required concrete grade. The higher replacement could also be used for other grades of concrete required such as M-25, M-20, and M-15 grade of concrete for simple structure in the construction industry by further optimization. Hence, the substitution of incinerated municipal solid waste fly ash from Reppie waste to energy plant for cement in concrete is environmentally promising which further encourages the use of waste as valuable resources thereby solves the problems caused by its direct disposal to the environment.