Demand of consuming green materials in life has been increasing day by day as the awareness of using environmentally friendly materials has risen. Geopolymer, in particular, is one of the green materials used for satisfying the need of current trends of development. This material has superior properties such as a low coefficient of thermal which is good for many engineering applications. But reports on its machinability, particularly with respect to surface integrity is still lacking. This study attempts to identify suitable ranges of turning parameter which can be used in a turning process of compressed geopolymer. Apart from that, this work tries to investigate and propose the best combination parameters and the most significant factor influencing the surface integrity of the compressed geopolymer in turning process. An orthogonal array L9 was made to guide the possibilities of each trial of turning process whereas the signal-to-noise ratio is employed to find the best combination of parameters. Analysis of variance were employed to analyse the machining parameters and determine the most factor influencing the surface roughness Ra. The optimum value of the surface roughness Ra was found to be 1.407 µm and the best combined factors are feed rate of 0.05 mm/rev, depth of cut of 0.1 mm and cutting speed of 3000 rpm. It was found that the feed rate is the most significant factor influencing the surface roughness by having percentage of contribution 90.37%. Another interesting finding was that the fly ash geopolymer is easier to perform turning operation after applying fresh gel to the compression process which led to enhance the mechanical properties. The final validation shows minimum surface roughness value contributed from the experiment with 6% improvement in surface integrity. From turning process, it is concluded that surface roughness value decreases with the decrease in feed rate and depth of cut, but it is increasing with the decrease of cutting speed. Overall this research has illustrated the potential of fly ash geopolymer as a good replacement to non-environmentally friendly and expensive materials in the machining process future.
