Investigation on the strength and durability of metakaolin-based geopolymer mortars with different kind of filling materials

In this study, it was aimed to evaluate the effect of different substitute powder filling materials on the strength and durability properties of metakaolin-based geopolymer mortars. For this, limestone powder, basalt powder, waste marble powder and recycled concrete aggregate powder were used with a size of lower than 63 μm. The powders were substituted by 25%, 50% and 75% by weight to the river sand, which was used as the main aggregate in the mortar. A total of 13 series of metakaolin-based geopolymer mortars were produced including the reference series. The ratios of the metakaolin and reactant mixture consisting of 12M sodium hydroxide and sodium silicate solutions were determined following the preliminary experiments. For all series 50 mm cube, 40 mm x 40 mm x 160 mm prism, 71 mm diameter and 150 mm height cylinder, 71 mm cube specimens were produced. After the curing at 60°C for 72 hours, unit volume weight, void ratio, water absorption ratio, ultrasonic pulse velocity, compressive strength, flexural strength, split tensile strength, Bohme abrasion resistance, high temperatures (200°C, 400°C, 600°C and 800°C), freeze-thaw and sulfates attack tests were carried out on a total of 1230 specimens. There were obtained optimum rates for limestone powder, basalt powder, waste marble powder and recycled concrete aggregate powder as 50%, 50%, 25% and 25%, respectively. The results have shown that all types of powder filling materials can be used in metakaolin-based geopolymer mortars. The best performance in terms of strength and durability properties was obtained with the 50% basalt powder substitution, and the widespread usage of geopolymer mortars and geopolymer concretes might be appropriate for many areas.