Geopolymer is a new development of material and are mostly discussed in the field of construction because of the ability of geopolymer is able to dry in ambient temperature with a short period of time. Besides, its machinable properties, particularly with respect to the surface roughness analysis have been not reported yet and surface roughness was identified as one of the quality attributes and directly related to productivity. So, compressive strength has been conducted to evaluate the mechanical properties of the steel fibre reinforced fly ash geopolymer based on the relationship between the qualities of the surface after lathe operation. The study tends to determine the best parameters setting that can be used for machining in minimizing the surface roughness. Taguchi method is employed to find the optimal levels of the significant factor affecting and to analyse the lathe parameters on surface roughness. The result showed the optimum value of compressive strength is 3% of addition steel fibre. The best parameter combination of parameters obtained is cutting speed (3000rpm), feed rate (0.15mm/min) and depth of cut (0.4mm). The most significant factor affecting surface roughness on the machining is cutting speed by 29.63%. The main significance of the study is surface roughness analysis on material of geopolymer based shows the minimum of surface roughness contributed from the experiment by 2.77 μm.
