Optimization of production parameters of novel hybrid fiber-reinforced geopolymer mortar: Application in masonry walls

Earthquakes cause heavy damages to occur in masonry walls, largely due to the use of low-strength mortar. The scope of this study aimed to produce a new mortar with higher strength, which does not use cement as a binder, instead of the mortars currently used as a binder. In the first stage, geopolymer mortar samples were prepared and the sample that gave the optimum results selected as the reference mix for fiber mixes. The highest compressive strength value was obtained in mixtures with Na2SiO3/NaOH (10 M) = 2 at mixing ratios. Then, seven different combinations were created for three different fiber types (carbon, glass and PP fiber). Among these mixtures, subjected to compression and flexural test with fiber combination in the produced samples, the mixture with the highest mechanical properties was used in masonry wall production. The compressive and flexural strength values of optimum fiber-reinforced o geopolymer mortar mixture under ambient conditions were obtained as 44.1 and 8.1 MPa, respectively. Significant increases were obtained in the compressive and flexural strengths with the increase in carbon fiber content in hybrid fiber ratios. Then, a uniaxial compression and diagonal test was applied to the walls produced with both normal mortar and geopolymer mortar. When the results are examined, the masonry wall prepared with fiber-reinforced geopolymer mortar (GPM) carried a load of 550 kN under vertical loading system, while the wall prepared with normal mortar carried a load of 147 kN under diagonal test. Through the experiments, it was determined that the walls produced using fiber-reinforced geopolymer mortar have higher shear and compressive strength values than the walls prepared with standard cementitious mortar. While the wall samples produced with cement-based standard mortar collapsed under the uniaxial compression test, the wall samples produced with fiber-reinforced geopolymer mortar showed ductile behavior and no sudden failures occurred under diagonal loading tests.