Disposal of fly ash obtained from thermal power plants is a major environmental concern. Fly ash contains large proportions of silica and ferrites. Investigation of its prospects as an electronic material provides scope for enhanced fly ash utilization. This involves measurement of relative permittivity and loss tangent. Experiments are carried out at X band frequencies in TE10 mode using standard klystron waveguide setup. Shorted Waveguide Method is used to determine the complex permittivity. The complex transcendental equation obtained is solved using Genetic Algorithm. Experimental results are compared with theoretical estimates based on Landau Lifshitz Looyenga (LLL) equation.