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Carbon-fiber-reinforced plastic materials have attracted several applications, including the fused deposition modelling (FDM) process. As a cheaper and more environmentally friendly alternative to its virgin counterpart, the use of milled recycled carbon fiber (rCF) has received much attention. The quality of the feed filament is important to avoid filament breakage and clogged nozzles during the FDM printing process. However, information about the effect of material parameters on the mechanical and physical properties of short rCF-reinforced FDM filament is still limited. This paper presents the effect of fiber loading (10 wt%, 20 wt%, and 30 wt%) and fiber size (63 µm, 75 µm, and 150 µm) on the filament’s tensile properties, surface roughness, microstructure, porosity level, density, and water absorptivity. The results show that the addition of 63 µm fibers at 10 wt% loading can enhance filament tensile properties with minimal surface roughness and porosity level. The addition of rCF increased the density and reduced the material’s water intake. This study also indicates a clear trade-off between the optimized properties. Hence, it is recommended that the optimization of rCF should consider the final application of the product. The findings of this study provide a new manufacturing strategy in utilizing milled rCF in potential 3D printing-based applications.

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The application of geopolymer materials from industrial waste as binder to cast concrete contributes to a reduction of CO2 than OPC but still contribute to other environmental adverse effect such as freshwater toxicity. The leaching of alkali from geopolymer building materials increases the alkalinity or pH values of affected water body and can cause damage the biotic ecosystem and aquatic organisms. Therefore, the increasing level of alkalinity which is pH values from the leaching of geopolymer materials and OPC caused the lethality of Anabas testudineus (climbing perch) were determined. A 50mm x 50mm x 50mm dimensional fly ash geopolymer paste with 12M NaOH solution (Na2SiO3 : NaOH = 2.5:1) and a 50mm x 50mm x 50mm dimensional OPC with the ratio of (Solid : Liquid = 3 : 1) were immersed accordingly into each cylindrical containers that contained an Anabas testudineus (climbing perch) in 500ml paddy swamp water. The fishes were observed and the pH readings were calculated. The test was ended until the fish dead. Finally, the mortality limit pH value of Anabas testudineus for fly ash geopolymer paste is at pH 11.0, while OPC is at pH 11.5. The peak of alkali leaching of fly ash geoplymer paste is between 0.5 – 1.0 hours while for OPC is between 0.25 – 0.5 hours. As the conclusion, OPC gives severe adverse effects to the mortality of Anabas testudineus than fly ash geopolymer paste due to the leaching of OH- and other alkali anions. Anabas testudineus can live 10 hours in fly ash leaching media but only can live 1 hour in OPC leaching media.

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