# 3D-Printed Lightweight Foamed Concrete with Dispersed Reinforcement
## 3 Results and Discussions
### Microscopy Observations
The analysis of pore distribution in printed and molded samples reveals significant differences in porosity and its influence on mechanical properties, particularly compressive and flexural strength. In printed samples, the incorporation of basalt and merino fibers contributes to a more refined pore structure, which may enhance material densification and mechanical performance. The microstructural analysis of the printed sample reinforced with basalt fibers (B1/SL/B05) indicates a uniform distribution of small pores, primarily below 2 \(\upmu\)m, as observed in Figure 18a. This lower porosity suggests improved material compactness, which may contribute to the highest compressive strength among the printed samples, reaching 4.14 MPa. Similarly, the printed sample containing merino fibers (B1/FA/M05) exhibits a relatively low porosity, with a pore size distribution concentrated below 2 \(\upmu\)m. This refined microstructure is likely to positively influence its mechanical properties, particularly flexural strength, which reaches 4.08 MPa. In contrast, the printed sample without fiber reinforcement (B1/FA) demonstrates a broader pore size distribution, with an increased presence of pores exceeding 2 \(\upmu\)m. This higher porosity could be a contributing factor to its lower compressive strength of 2.68 MPa. In molded samples, the pore distribution differs substantially, with a notable increase in both pore size and heterogeneity, which negatively impacts mechanical properties. The molded sample containing basalt fibers (B1/SL/B05) exhibits significantly larger pores, some exceeding 10 \(\upmu\)m, as shown in Figure 19a. This higher porosity may be responsible for its reduced compressive strength of 3.21 MPa compared to its printed counterpart. The molded sample reinforced with merino fibers (B1/FA/M05) presents an even broader pore size distribution, with pores exceeding 20 \(\upmu\)m. This increased porosity likely contributes to a further reduction in compressive strength, reaching 2.80 MPa. The most pronounced porosity is observed in the molded sample without fibers (B1/FA), where numerous macropores larger than 10 \(\upmu\)m are evident. Such an irregular and porous structure leads to the lowest recorded compressive strength of 1.72 MPa. Figure 17: Cont. Figure 17: Microscopic images illustrating pore size and distribution in samples with various fiber types (**a**,**b**) coconut fibers, (**c**,**d**) basalt fibers, (**e**,**f**) glass fibers, (**g**,**h**) merino fibers, (**i**,**j**) polypropylene fibers, (**k**) without fibers. The correlation between porosity and mechanical properties suggests that printed samples consistently exhibit lower porosity and smaller pore sizes compared to molded samples, which may contribute to their superior mechanical performance. The refined pore structure in printed samples, particularly those reinforced with basalt and merino fibers, likely enhances material densification and structural integrity. This may explain the relatively high flexural strength observed in these samples. In contrast, the larger and more irregularly distributed pores in molded samples create structural weaknesses, reducing their mechanical performance. Additionally, the presence of fibers, especially basalt, appears to contribute to a more controlled pore distribution, further supporting the material's strength. Conversely, the absence of fibers leads to increased porosity, which may adversely affect mechanical integrity. These findings underscore the advantages of additive manufacturing in controlling porosity and optimizing the mechanical properties of fiber-reinforced cementitious materials. Figure 18: Pore size distribution in printed samples: (**a**) B1/SL/B05 (4.14 MPa), (**b**) B1/FA/M05 (4.08 MPa), (**c**) B1/FA (2.68 MPa).