Investigation of high temperature resistance of hybrid fiber reinforced self-compacting concrete

In this thesis study, a total of ten different self-compacting concrete (SCC) mixtures were designed to determine how and to what extent the high temperature resistance and mechanical properties of hybrid fiber self-compacting concrete mixtures are affected depending on the fiber ratio and type. For this purpose, one types mixture having no fiber, one types of single reinforced mixtures having only macro steel fiber, four types of binary reinforced mixtures and four types of ternary reinforced mixtures were adopted. Four different types (steel and synthetic), aspect ratio and size (macro and micro) of fibers were used to investigate the effect of fibers in designed SCC. In all mixes, Portland Cement (PC) and fly ash (FA) were used as binders, the water/binder ratio was kept constant at 0.23 and total binder content at 900 kg/m3. The mixtures obtained by trial and error on the based of the slump-flow test were subjected to workability tests (slump-flow, J-ring and j.-ring slump-flow test and t50) determined by EFNARC. The mixtures were then cured for 90 days in 20 ± 3 0C water. After cured samples were kept at room temperature and exposed to high temperatures of 250 0C, 500 0C and 750 0C, compressive strength, splitting tensile strength and four-point flexural strength tests were applied. Consequently, it was found that the addition of both micro steel fiber and macro steel fiber to the mixture caused an increase in the compressive strength of the samples, while it reduced the splitting tensile strength, flexural strength and the energy absorption capacity. It was observed that micro synthetic fibers decrease compressive strength while it provides an improvement in the splitting tensile strength, flexural strength and the energy absorption capacity. According to the experimental findings, it was determined that the deterioration in the mechanical properties of all fiber reinforced SCC under high temperature was less compared to the control SCC concrete with no fiber, while samples of SCC mixtures containing synthetic fiber exhibited superior properties by improving a higher fire performance in concrete and reducing disintegration .