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1. Characteristics and microstructures of the GFRP waste powder/GGBS-based geopolymer paste and concrete

   https://doi.org/10.1515/rams-2022-0005  

   Zheng, Chuji; Wang, Jun; Liu, Hengjuan; GangaRao, Hota; Liang, Ruifeng (January 2022, REVIEWS ON ADVANCED MATERIALS SCIENCE)

   Abstract A novel method is developed for reusing the waste glass fiber-reinforced polymer (GFRP) powder as a precursor in geopolymer production. Several activation parameters that affect the workability and strength gain of GFRP powder-based geopolymers are investigated. The results of an experimental study reveal that the early strength of GFRP powder-based geopolymer pastes develops slowly at ambient temperature. The highest compressive strength of GFRP powder-based geopolymer pastes is 7.13 MPa at an age of 28 days. The ratio of compressive strength to flexural strength of GFRP powder-based-geopolymers is lower than that of fly ash and ground granulated blast furnace slag (GGBS)-based geopolymers, indicating that the incorporation of GFRP powder can improve the geopolymer brittleness. GGBS is incorporated into geopolymer blends to accelerate the early activity of GFRP powder. The binary geopolymer pastes exhibit shorter setting times and higher mechanical strength values than those of single GFRP powder geopolymer pastes. The GGBS geopolymer concrete mixture with 30 wt% GFRP powder displayed the highest compressive strength and flexural strength values and was less brittle. The developed binary GFRP powder/GGBS-based geopolymers reduce the disadvantages of single GFRP powder or GGBS geopolymers, and thus, offer high potential as a building construction material. 

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2. Rapid Adsorption of Cationic Methylene Blue Dye onto Volcanic Ash‑metakaolin Based Geopolymers

   https://doi.org/doi.org/10.1007/s12633-021-01637-9  

   Shikuku, Victor O.; Tome, Sylvain; Hermann Dzoujo T.; Tompsett, Geoffrey A.; Timko, Michael T. (January 2022, Silicon)

   In this study, four geopolymer sorbents GP0, GP10, GP30 and GP50 were synthesized using volcanic ash (VA) and metakaolin (MK) blends as precursors with 0, 10, 30 and 50% MK content by mass, respectively. The materials were characterized by X-ray fuorescence (XRF), X-ray difraction (XRD), Raman spectroscopy, and Brunauer–Emmett–Teller (BET) surface area analyses, revealing successful geopolymerization of the precursors and increasing surface area with increasing MK content. The sorption performance of the VA, MK and VA-MK geopolymers was then evaluated for the removal of cationic methylene blue (MB) dye from aqueous media. Sorption capacity was independent of composition, providing fexibility in sorbent synthesis. Sorption rate, on the other hand, was 3–8 times greater for the VA-MK geopolymers than the precursor materials. The equilibrium adsorption data were suitably explained by the Freundlich model, denoting multilayer adsorption onto a heterogeneous adsorption surface with higher Freundlich afnity constant (KF) for geopolymers than VA. The adsorption kinetics obeyed the pseudo-second-order (PSO) kinetic law with an average of 98% removal efciency in 30 min. MB uptake was pH-dependent and driven by electrostatic chemisorption interactions. These results motivate further studies on the use of locally sourced geopolymers for water purifcation applications. 

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3. Microwave materials characterization of geopolymer precursor powders

   https://doi.org/10.1109/I2MTC.2018.8409709  

   Edwards, Cody A.; Donnell, Kristen M.; Shearer, Christopher R. (May 2018, 2018 IEEE International Instrumentation and Measurement Technology Conference (I2MTC))

   Geopolymers are structural materials that can be used as a viable alternative to ordinary portland cement concrete. However, their widespread adoption has been limited by the lack of understanding in their fundamental reaction mechanisms. Microwave characterization methods have shown promise at understanding these reaction mechanisms. However, the complex dielectric properties of geopolymer precursor powders and the effect of void content must first be understood. Therefore, in this work, the dielectric properties of two geopolymer precursor powders (blast furnace slag and fly ash) are measured. Then, the effect of void content and particle size distribution (PSD) is considered on the measured dielectric properties. By characterizing the inherent void content of these powder materials, this effect can be removed and therefore the true dielectric properties of the materials can be determined. The results show that the void content has a significant effect on the measured dielectric properties. 

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4. Volcanic ash ice nucleation activity is variably reduced by aging in water and sulfuric acid: the effects of leaching, dissolution, and precipitation

   https://doi.org/10.1039/D1EA00071C  

   Fahy, William D.; Maters, Elena C.; Giese Miranda, Rona; Adams, Michael P.; Jahn, Leif G.; Sullivan, Ryan C.; Murray, Benjamin J. (January 2022, Environmental Science: Atmospheres)

   Volcanic ash nucleates ice when immersed in supercooled water droplets, giving it the potential to influence weather and climate from local to global scales. This ice nucleation activity (INA) is likely derived from a subset of the crystalline mineral phases in the ash. The INA of other mineral-based dusts can change when exposed to various gaseous and aqueous chemical species, many of which also interact with volcanic ash in the eruption plume and atmosphere. However, the effects of aqueous chemical aging on the INA of volcanic ash have not been explored. We show that the INA of two mineralogically distinct ash samples from Fuego and Astroni volcanoes is variably reduced following immersion in water or aqueous sulfuric acid for minutes to days. Aging in water decreases the INA of both ash samples by up to two orders of magnitude, possibly due to a reduction in surface crystallinity and cation availability accompanying leaching. Aging in sulfuric acid leads to minimal loss of INA for Fuego ash, which is proposed to reflect a quasi-equilibrium between leaching that removes ice-active sites and dissolution that reveals or creates new sites on the pyroxene phases present. Conversely, exposure to sulfuric acid reduces the INA of Astroni ash by one to two orders of magnitude, potentially through selective dissolution of ice-active sites associated with surface microtextures on some K-feldspar phases. Analysis of dissolved element concentrations in the aged ash leachates shows supersaturation of certain mineral species which could have precipitated and altered the INA of the ash. These results highlight the key role that leaching, dissolution, and precipitation likely play in the aqueous aging of volcanic ash with respect to its INA. Finally, we discuss the implications for understanding the nature and reactivity of ice-active sites on volcanic ash and its role in influencing cloud properties in the atmosphere. 

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5. Additive Manufacturing of Porous Ceramics With Foaming Agent

   https://doi.org/10.1115/MSEC2021-63493  

   Guo, Zipeng; An, Lu; Lakshmanan, Sushil; Armstrong, Jason N.; Ren, Shenqiang; Zhou, Chi (June 2021, ASME 2021 16th International Manufacturing Science and Engineering Conference)

   Abstract The macro-porous ceramics has promising durability and thermal insulation performances. A cost-effective and scalable additive manufacturing technique for the fabrication of macro-porous ceramics, with a facile approach to control the printed porosity is reported in the paper. Several ceramic inks were prepared, the foaming agent was used to generate gaseous bubbles in the ink, followed by the direct ink writing and the ambient-pressure and room-temperature drying to create the three-dimensional geometries. The experimental studies were performed to optimize the printing quality. A set of studies revealed the optimal printing process parameters for printing the foamed ceramic ink with a high spatial resolution and fine surface quality. Varying the concentration of the foaming agent enabled the controllability of the structural porosity. The maximum porosity can reach 85%, with a crack-free internal porous structure. The tensile tests showed that the printed macro-porous ceramics have enhanced durability with the addition of fiber. With a high-fidelity 3D printing process and precise control of the porosity, the printed samples exhibited a low thermal conductivity and high mechanical strength. 

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