Investigation of mechanical properties of masonry walls produced with mixed (hybrid) fiber geopolymer mortars

From the past to the present, masonry structures have been used to meet the need for shelter. One of the most important building materials in masonry structures is mortars. In this study, it was aimed to produce a new cementless and high strength mortar instead of cement mortar, which is the most widely used binder of today. In this context, firstly, 4 different mixture types were determined and 12 types of geopolymer mortar mixture (GH) were created by activating each mixture in 3 different ways. Six samples were poured from each of these 12 mixtures and 72 GH samples were prepared. These GH samples were subjected to compression tests on the 7th and 28th days, and the sample with the highest compressive strength was selected for use in fibrous mixtures. Then 3 different fiber types; carbon fiber, polypropylene fiber (PP) and glass fiber added to the optimum mixture. Seven different combinations were created with these 3 types of fiber and mixed separately with the selected GH. To test the workability of the mixtures, the spreading table test was applied and the results were recorded. These mixtures were named as KR1-KR2-KR3-KR4-KR5-KR6-KR7 and were cast into 40*40*160 mm molds. On the 7th and 28th days following casting, the specimens were first determined for flexural strength and then uniaxial compressive strength. In addition, a close correlation was obtained between UPV and compressive strengths, and as a result of these tests, the mixture with the highest compressive strength was determined as KR2, and the mixture with the lowest results was determined as KR3. Scanning electron microscopy (SEM) to look at the microstructural properties of these two mixtures and EDX analyzes to reveal the mineral structure were performed. In order to test the selected KR2 mixture on the walls, ten walls were built with 70*70 cm pressed brick material. Five of the walls were built with KR2 mixture (GPM) and the remaining five with standard cementitious mortar (NM) and tested 28 days later under axial and diagonal loading. As a result of the experiments, GPM walls showed 55% more compressive strength under axial loading and 100% more under diagonal loading. While a sudden and brittle failure mechanism is observed in NM walls, on the contrary, in GPM walls, thin cracks were observed in case of failure and showed a more ductile behavior.