Structural performance of expanded slate lightweight self-consolidating concrete containing polymeric fibers

Omar, Ahmed Taha Mohamed (2023) Structural performance of expanded slate lightweight self-consolidating concrete containing polymeric fibers. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

This thesis investigates the possibility of using different polymeric fibers in the development of a number of successful lightweight self-consolidating concrete (LWSCC) and lightweight vibrated concrete (LWVC) mixtures with minimum possible density and improved mechanical properties. The investigation examines different replacement levels of normal-weight fine or coarse aggregates by fine and coarse lightweight expanded slate (Stalite) aggregates to optimize these mixtures. The research program was divided into four stages. The first stage aimed to develop and optimize a number of successful LWSCC and fiber-reinforced LWSCC (FRLWSCC) with minimum possible density, adequate mechanical properties and maximized impact resistance using expanded slate lightweight coarse (LC) and lightweight fine (LF) aggregate. The second stage evaluated the mechanical properties of these developed mixtures under cold temperatures. The effect of using different polymeric fibers’ types, lengths, and volumes on enhancing the shear and flexural performance of large-scale reinforced LWSCC beams was investigated in the third stage of this program. Finally, the fourth stage examined the influence of combining PVA fibers and the maximum possible volume of Stalite aggregates on the structural performance of exterior beam-column joints (BCJs) under reversed cyclic loading. The results indicated that it was possible to use up to 0.3% fraction volume of polymeric fibers with a binder content of 550 kg/m3 to develop LWSCC mixtures with acceptable self-compactability. Increasing the binder content to 600 kg/m³ allowed a maximum of 0.5% fibers and higher content of lightweight expanded slate aggregate to be used safely, achieving further reduction of the mixture density and better improvements in the tensile strength. It was also concluded that, when comparing different lengths of polymeric fibers, the highest improvement in the impact resistance of tested FRLWSCC mixtures was observed when shorter fibers were used. Under sub-zero temperatures, the results revealed that increasing the volume of either LC or LF in the mixture showed more improvement in the mechanical properties and impact resistance under cold temperatures, however, the failure mode of these mixtures appeared to be more brittle. Replacing normal-weight aggregates, in the third stage, with either LC or LF to reduce the mixtures’ density by approximately 15% negatively affected the ultimate shear load, bending moment capacity, ductility, and energy absorption capacity of the tested beams. However, the use of 0.5% PVA fibers completely alleviated for these reductions in shear capacity and flexural strength of tested beams, and further helped the beams to achieve much higher ductility and absorbed energy. It was also found that using LF better improved the beams’ load-carrying capacity, post-diagonal cracking resistance, deformability, ductility, and energy absorption capacity compared to using LC. Properly detailed LWSCC-BCJs (with sufficient hoops) showed slightly lower load-carrying capacity, ductility and dissipated energy, when compared to NWSCC specimen. The results also revealed that using high percentage of PVA fibers (1%) in the development of lightweight vibrated concrete (LWVC) compensated for the significant reduction in load-carrying capacity that resulted from using high Stalite content and helped improve the overall cyclic performance of BCJs. This improvement allowed to develop BCJ with significant enhancement in ductility, stiffness, and energy dissipation, while maintaining a considerable reduction in the self weight reached up to 28% lower than NWSCC.

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