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    Öğe
    Effects of Mixture Design Parameters on the Mechanical Behavior of High-Performance Fiber-Reinforced Concretes
    (ASCE-AMER SOC CIVIL ENGINEERS, 2020) Erdem, Tahir K.; Demirhan, Serhat; Yildirim, Gurkan; Banyhussan, Qais S.; Sahin, Oguzhan; Balav, Mohammad H.; Sahmaran, Mustafa
    The main purpose of this research is to assess the influence of different design parameters on the mechanical performance of high-performance fiber-reinforced concrete (HPFRC) mixtures. Special attention is also paid to achieving deflection-hardening behavior in the presence of a large amount of coarse aggregates. Different mixture design parameters were the initial curing ages (3, 7, 28, and 90 days), ratios of Class F fly ash (FA) to portland cement (PC) (0.0, 0.2, and 0.4), addition/type of nanomaterials [nanosilica (NS), nanoalumina (NA), and nanocalcite (NC)], and combinations of fibers [polyvinyl-alcohol + steel (P, S) or brass-coated microsteel + steel (B, S)]. The experimental program included the evaluation of compressive strength, flexural strength, and midspan deflection results in addition to test parameters recorded under biaxial flexural loading via a series of square panel tests, including peak load and energy absorption capacities. Test results revealed that deflection-hardening response coupled with multiple microcracks can be obtained when large amounts of coarse aggregates are available for all HPFRC mixtures. As expected, experimental results change depending on the different curing ages and FA/PC ratios. The most distinctive parameters affecting the results are addition/type of nanomaterials and the presence of different fiber combinations. In the presence of nanomaterials, all results from the different tests improved, especially for NA and NS inclusions. With slight concessions in flexural deflection results, B fiber is shown to be a successful candidate to fully replace costly P fibers because most properties of B, S fiber-reinforced HPFRC mixtures outperformed those with P, S fibers, both under four-point bending and biaxial flexural loading.
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    Öğe
    Performance of engineered cementitious composites under drop-weight impact: Effect of different mixture parameters
    (Ernst & Sohn, 2019) Yildirim, Gurkan; Khiavi, Farhad Emami; Anil, Ozgur; Sahin, Oguzhan; Sahmaran, Mustafa; Tugrul Erdem, Recep
    Current research focuses on the experimental and numerical determination of impact performance of engineered cementitious composites (ECC). Performance assessment of ECC beams with different mixture parameters was made. Mixtures were produced with different replacement rates of Class-F fly ash and slag with Portland cement, water to binder ratios and fiber types (polyvinyl alcohol [PVA] and nylon [N]). Experimental works were validated with incremental dynamic analyses performed by ABAQUS finite element software. Impact testing results were further supported by mechanical property results. Results reveal that each individual mixture parameter used is distinctively effective in modifying the properties under both sudden impact and slow static loading. In brief, enhanced impact resistance is noted when ECC is produced with slag, low amounts of pozzolanic materials, low W/B ratio, fiber addition and PVA fibers. Experimental results were also in line with the numerical results from ABAQUS largely. Significantly, cost-effective N fibers were also shown to be fully replaceable with costly PVA fibers without jeopardizing mechanical/impact performance, if mixture design parameters are adjusted suitably. Current research is likely to attract further research on the development of ECC that is with lower cost and comparable impact/mechanical performance with regards to widely studied more expensive counterparts in the literature.