Synthesis and characterization of fly ash based geopolymer ceramics: effect of NaOH concentration

Abstract

Ceramic materials have demonstrated impressive performance under severe conditions in a wide number of areas including health, energy and environment, transportation and electronic applications. In order to meet the growing demand of specific properties of ceramics, the use of geopolymer method were introduced as an alternate way by providing new material to fabricate geopolymer as ceramic precursor and moving towards green technology. Geopolymer ceramic was produced using fly ash as source materials. Different molarities of sodium hydroxide solution in the range of 8 M to 14 M were used in the preparation of fly ash geopolymer ceramic. The ratio of fly ash/alkaline solution and alkaline activator were kept constant at 2.0 and 2.5 respectively. Physical and mechanical properties such as density, flexural strength and shrinkage were determined. The optimum flexural strength of 61.6 MPa is obtained at the sodium hydroxide concentration of 12 M with the density of 2.21 g/cm³. The formation of almost fully crystalline phase with appearance of albite contribute to the flexural strength of fly ash geopolymer ceramic. Microstructure image result shows that a presence of pores due to sintering effect and smoother matrix which gives denser structure as supported by the excellent density.