Investigation of the effect of zeolite on rheological behaviours of geopolymer mortars

Natural zeolite is a mineral that found abundantly in nature. It is known as the aqueous aluminosilicate source. It is widely used in the fields of agriculture and farming. It is also used as a filter material in garbage areas and for absorbing polluting gases such as CO2 because of its high adsorbing property. Both natural and synthetic zeolites can be used for reducing impacts of heavy metals, nitrogen-containing wastes and wastewater treatment. Academic studies for the use of zeolites in construction technology are ongoing. However, the activation of natural zeolite with alkali and the properties of mortars produced with geopolimer binding substance as a result of activation with alkali and natural zeolite is not fully known yet. In this study, geopolymer binding material was made by combining natural zeolite with activator sodium hydroxide (NaOH). 3 different aggregate/binder ratios were used. The cure was selected 72h at 900C temperature. Natural zeolite was replaced with in the ratios of 0%, 10%, 25%, 40%, 55%, 70%, 85% and 100% instead of CEM I 42.5 N. The fresh viscosity values of the samples were measured by a viscometer. 28 days compressive strengths, unit weights, ultrasonic pulse velocity (UPV) values and microstructures (XRD, SEM-EDX) of the samples were investigated. According to the result of experiments, in general, it was found that viscosity increases with the increase of natural zeolite ratios. As the aggregate/binder ratios increase, increases in compressive strength were observed. Geopolymer mortar produced with sodium hydroxide (NaOH) activator showed the highest compressive strength (78.5 MPa) in samples with containing 10% zeolite and aggregate/binder ratio of 1,75. Moreover, decreases in the unit weight value of the mortars were determined by increasing the amount of zeolite.