# 3D-Printed Lightweight Foamed Concrete with Dispersed Reinforcement
## 3 Results and Discussions
### Stability and Buildability  
A portion of the prepared material was cast into molds, while the remaining portion was subjected to extrusion. All samples of fiber-reinforced foamed concrete were printed under standardized conditions, utilizing identical printing parameters. During the experiment, issues related to material blockage in the screw feeder were encountered, particularly in samples containing 1% by weight of fibers. This phenomenon has also been reported by other researchers [54]. To confirm the reproducibility of this issue, certain tests were repeated multiple times to assess whether screw and nozzle clogging persisted for specific mixtures. For mixtures containing 1% by weight of polypropylene fibers, the printing process proved to be unfeasible. Similarly, for the sample containing fly ash and 1% by weight of merino wool fibers, successful printing occurred only once, despite multiple attempts. In contrast, the extrusion of foamed concrete mixtures without fibers proceeded without incident, indicating a higher degree of stability in the absence of dispersed reinforcement. Mixtures without fibers exhibited higher flow properties, requiring a waiting period of 20 to 40 min before extrusion could commence, depending on the composition of the mixture. Figures 4-9 provide a representative view of the printed material layers depending on their composition. Both during the printing process and after curing, it was  
Figure 8: Printed samples reinforced with polypropylene fibers. Figure 6: Printed samples reinforced with glass fibers. Figure 7: Printed samples reinforced with merino wool fibers. Samples reinforced with coconut fibers (Figure 4) exhibited significant surface roughness and pronounced irregularities in the printed layers. This effect was further amplified at a higher fiber content (1%). These observations can be attributed to the inherent stiffness and larger diameter of coconut fibers compared to other fiber types, which hinder their homogeneous integration into the concrete matrix. Consequently, the flowability of the mixture during the printing process was adversely affected, leading to disruptions in the layering process and increased uncontrolled material flow. In contrast, basalt fiber-reinforced samples (Figure 5) displayed improved cohesion between layers relative to those containing natural fibers. The surface quality of these samples was relatively smooth, with fewer pronounced irregularities. At a lower fiber concentration (0.5%), the printed layers were notably more uniform, indicating better compatibility of basalt fibers with the concrete mixture in the context of extrusion-based printing. Samples containing glass fibers (Figure 6) demonstrated well-defined layering and a relatively stable structural profile. However, at a higher fiber content (1%), localized surface irregularities and rippling were observed, suggesting challenges in maintaining consistent material flow during extrusion. Nevertheless, the incorporation of glass fibers appeared to improve the overall stability of the printed layers, contributing to enhanced cohesion compared to natural fiber-reinforced samples. Specimens reinforced with merino wool fibers (Figure 7) exhibited considerable surface irregularities, particularly at the higher fiber concentration (1%). These fibers introduced localized disruptions during the printing process, frequently causing nozzle blockages and leading to uneven stacking of the layers. At the lower fiber concentration (0.5%), the printed structures were slightly more uniform, though rippling effects remained evident. Samples containing polypropylene (PP) fibers (Figure 8) could only be successfully printed at the lower fiber concentration (0.5%), as mixtures with 1% fiber content led to frequent nozzle clogging, preventing extrusion. Despite this limitation, the samples with 0.5% PP fibers exhibited the highest degree of surface smoothness and uniformity among all the reinforced samples analyzed, aligning with results from previous research conducted by the authors [56].