Structural performance of fiber-reinforced lightweight concrete slabs with expanded clay aggregate

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Abstract The main objectives of this study are to inspect experimentally the structural behavior of fiber reinforced lightweight concrete two-way slab through examining the influence of different fibers combinations on the initial crack load, ultimate load, strain distribution, maximum deflection and ductility factor. The experimental program of this study included fabricating and testing eleven specimens cast using lightweight concrete of expanded clay aggregate. All the considered specimens were identical in their dimensions (1150 × 1150 × 100 mm), constituent materials properties, fiber volume fraction, and steel reinforcement details except their steel fibers combination. One of the specimens was of plain concrete (without fibers), two of them were reinforced by mono steel fiber (hooked or straight), another two were of triple hybrid fibers (three types of fibers: hooked and straight with glass or polypropylene), while the remaining (six specimens) were of double hybrid fibers (two types of fibers: hooked or straight with glass or polypropylene) reinforced concrete. According to the obtained results, adding mono fiber or hybrid fibers is highly effective to enhance the initial crack load, ultimate load, strain distribution, maximum deflection and ductility. It also increased the stiffness of the specimens. Moreover, it deferred the proliferation of cracks, restricted their progressing, kept the integrity of the specimens at the post cracking stage, and avoided their ruin at the failure stage through its “bridging” effect. The outcomes of the experimental results illustrated that hybrid fibers had the most significant advanced effect on the structural behavior of lightweight concrete specimens. Moreover; the optimization procedure revealed that the best performance in terms of maximum achieved in the specimen reinforced by hybrid fibers [straight + hooked + polypropylene]. The maximum achieved enhancement was 133.33%, 81.4%, 24.56%, 29.35% and 147% for the initial crack load, ultimate load, strain distribution, deflection and ductility, respectively.