Investigation of physical, mechanical and durability properties of geopolymer mortars produced with waste concrete and marble powder

This study investigates the effects of silica fume (SF) and fly ash (FA) binders together with construction waste (WW) and marble dust (MD) aggregates on the properties of geopolymer mortars. The alkali activator concentration was selected as 12 M (NaOH), with a Na2SiO3/NaOH ratio of 2. In the prepared mixtures, %25 by weight of YA was replaced with MD aggregate. Additionally, SF used as a binder was partially replaced with FA at 0%, 10%, 20% and 30% by weight. Physical, mechanical and durability tests were carried out on geopolymer samples. Microstructure analyses were also conducted using a scanning electron microscope (SEM). As the WW content in the mixtures decreased, both water absorption and apparent porosity values decreased. Flexural tensile strength increased with higher SF and MD ratios, although a decrease was observed beyond a certain point. Compressive strength improved with increasing MD content. Damage observed in the freeze-thaw test was most severe in samples containing 0% SF. In conclusion, increasing the amount of marble dust and reducing the silica fume content led to improved performance in geopolymer mortars compared to the reference samples.