Mechanical strength variation of zeolite-fly ash geopolymer mortars with different activator concentrations

Özet

Zeolite is of a significance for geopolymers as it is a natural precursor and does not require additional heat treatment for activation. However, aluminosilicates sourced from natural sources require additional handling for the best use of exploitation. In this study, geopolymers were synthesized by binary use of zeolite and fly ash as main binding material and sodium silicate and sodium hydroxide as alkaline activator. The influence of alkaline activator ratios and sodium hydroxide concentrations on the compressive strength and flexural strength of the zeolite-fly ash based geopolymers were studied. In this research, zeolite-fly ash based geopolymer mortars were pro duced by using 50% of natural zeolite (clinoptilolite) and 50% of C-type fly ash. Four different activator ratios ($Na_2SiO_3$/NaOH: 1, 1.5, 2 and 2.5) and two sodium hydrox ide molarities (10M and 12M) was utilized to activate zeolite and fly ash in order to determine the effect of these parameters on the mechanical strengths of the pro duced geopolymer mortars. The results indicated that as the alkaline activator ratio and NH molarity were increased the compressive strength of the zeolite-fly ash based geopolymers also increased. The maximum compressive and flexural strength values obtained after 28 days of curing were 20.1 MPa and 5.3 MPa respectively and corre sponds when used activator ratio of 2.5 and sodium hydroxide concentration of 12 molarity. The obtained results indicated that both the alkaline activator ratio and so dium hydroxide concentration affected the compressive and flexural strengths of ze olite-fly ash based geopolymer mortar specimens.