Behavioral analysis of cementitious composites reinforced with glass fibers of different lengths

In this thesis, the performance of hybrid use of different lengths of glass fiber in cement composite after high temperature exposure was investigated. By adding fibers, the formation and propagation of cracks in the cementitious composite are controlled. Fibers added to the composite in single lengths limit the cracks occurring at a single scale. The addition of multiple fiber lengths has a multi-level effect on cracks. While shorter fibers added to the composite are effective on micro cracks in the composite, long fibers are effective on macro cracks. Therefore, in this study, the effects of separate and hybrid use of 3 mm, 6 mm, and 12 mm glass fibers in cementitious composite were investigated. The produced samples were tested without damaged and after exposure to high temperatures of 400°C, 600°C, and 800°C. As a result of the bending, pressure, ultrasonic pulse velocity (UPV), and mass loss values, it was seen that the samples containing hybrid length fibers gave the best values in the samples. While an improvement of up to 77.88% was observed in the bending strength values of different fiber lengths samples exposed to high temperatures, this value was obtained as 21.34% in compressive strength. The results showed that the addition of hybrid length fibers was effective on micro and macro cracks that would occur in the composite and thus improved the mechanical strength of the composite samples after high temperatures. SEM analysis showed that the glass fibers maintained their existence against high temperatures, and the use of different fiber lengths strengthened the composite matrix by having a synergistic effect. It was also observed in the obtained data that hybrid length fibers also improved mass loss and UPV values. Therefore, it can be said that the hybrid use of fibers of different lengths improved the durability of the composite.