Yazar "Kriven, Waltraud M." seçeneğine göre listele

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    Abaca fiber as an efficient reinforcement for high mechanical performance in metakaolin-based geopolymers
    (Wiley, 2024) Trindade, Ana Carolina Constancio; Sood, Sai Shruti; Silva, Deyvid do Carmo; Ozer, Ali; Kriven, Waltraud M.
    This study introduces an innovative method for efficiently integrating abaca fibers into a potassium-based geopolymer (KGP) material. Geopolymers often suffer from brittleness, and composite designs have been explored as a solution to enhance their strength and ductility. While synthetic reinforcements are commonly employed due to their consistent properties, natural fibers offer a renewable and eco-friendly alternative. However, their widespread use has been hindered by complex and time-consuming treatments, resulting in variable morphologies that affect fiber-matrix adhesion. It is worth noting that previous research has primarily focused on alkali-activated and cementitious applications, leaving a knowledge gap in understanding its interactions with calcium-free, metakaolin-based geopolymers. Consequently, this study aimed to simplify the conversion of raw abaca into uniformly chopped filaments, facilitating their integration into KGPs at levels of up to 7 wt%. The mechanical evaluation revealed exceptional performance, with compressive strengths reaching up to 45 MPa. A thorough analysis confirmed robust, fiber-matrix adhesion and identified the presence of lignin and cellulose, significantly contributing to the fiber's strength. Flow table tests showcased their versatility, transitioning from high flowability (1 wt%) to complete shape retention (7 wt%). Furthermore, all variations exhibited great ductility, multiple cracking formation, and minimal variability in mechanical properties.
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    Phase variation and mechanical properties of waste calcium carbonate to substitute quartz in composite slab production
    (Wiley, 2023) Bas, Sedanur; Guler, Taki; Ozer, Ali; Akturk, Selcuk; Kriven, Waltraud M.
    Owing to the fast-emerging nature and rapid advancements in the construction industry, huge volumes of marble dust (MD) are generated as reject during slab cutting in marble processing, causing significant environmental hazards. Nowadays, quartz composite slabs have increasingly been preferred in building works due to their excellent hygienic property and mechanical strength. Composite slab is produced using micronized quartz as filler, the grinding of which is an energy-intensive process. Substitution of micronized quartz with MD at different percentages was investigated in natural form and after roasting. Natural MD offered appreciable physical properties closer to those of a quartz composite slab. Physical properties slightly retrograded by quartz supplementation in the raw form. Roasting the filler led to the formation of rounded Ca-silicate. Wollastonite was the first phase formed after sintering at the lowest MD percentage and shortest roasting times. Larnite became dominating phase first by increasing MD percentage and roasting time, and then calcio-olivine formed. Physical characterization test results demonstrated that hardnesses of new phase and particle shape were the key parameters that improved slabs' mechanical properties of. Hard rounded larnite particles improved mechanical behavior of slabs having the synergic effect of quartz, whereas wollastonite did not show a significant effect.