# 3D-Printed Lightweight Foamed Concrete with Dispersed Reinforcement
## 3 Results and Discussions
### Flexural Strength Test
The reduced porosity in printed samples contributes to their higher apparent density and improved material uniformity. However, inconsistencies in material flow during extrusion may lead to uneven layer deposition and localized voids. Curing conditions further amplify these density differences. Molded samples are typically cured in controlled environments, ensuring uniform hydration and solidification, which minimizes shrinkage and void formation. In contrast, printed samples, due to greater surface exposure, are prone to uneven curing, leading to micro-shrinkage and a higher void ratio. The effect of specific additives on apparent density also varies between preparation methods. Samples containing coconut fibers (CO) and glass fibers (G) show lower densities, likely due to the lightweight and porous nature of these additives, which disrupt the flow and packing of foamed concrete during printing. Polypropylene fibers (PP) have the most pronounced effect in reducing density in printed samples, likely due to their flexible and fibrous structure, which interferes with layer cohesion and exacerbates void formation. The amount of fiber additive also plays a significant role in the behavior of materials during molding and printing. At lower fiber concentrations (0.5%), the material exhibits greater cohesiveness, resulting in higher apparent density and better compaction, particularly in molded samples. For printed samples, reduced fiber content decreases the likelihood of interlayer void formation. In contrast, higher fiber concentrations (1%) introduce discontinuities into the matrix, increasing porosity and reducing density. Excessive fiber content in printed samples can hinder smooth layer deposition and bonding, leading to structural defects such as voids and weak interlayer connections. In this study, the differences in density between molded and printed samples are particularly pronounced in fiber-rich materials, such as those containing coconut fibers (CO) or polypropylene fibers (PP). To mitigate density reductions in printed samples, several optimization strategies can be employed. Adjusting printing parameters, such as reducing layer height, slowing printing speed, and increasing extrusion pressure, can improve interlayer bonding and material compactness. The introduction of chemical bonding agents or mild compaction during printing may further reduce void formation. Additionally, enhancing curing conditions through controlled humidity and temperature environments can promote uniform hydration and minimize shrinkage without compromising porosity. Microstructural analyses, such as those conducted by [PERSON] et al., reveal that while concrete produced via 3D printing demonstrates greater uniformity compared to traditionally molded concrete, anisotropic pores are present [60]. These pores, primarily a consequence of the layer-by-layer deposition process, are not uniformly distributed and exhibit preferential orientations. While increasing apparent density generally improves structural strength and durability, it is essential to consider the trade-off with thermal insulation. The thermal insulating properties of foamed concrete rely on its porosity, as air pockets within the material act as insulators. Therefore, optimization efforts should aim to balance structural performance with the preservation or enhancement of porosity for improved insulation. Furthermore, adjustments to printing parameters, such as reducing layer height or printing speed, should be carefully evaluated to avoid compromising the overall efficiency and productivity of the process.