# 3D-Printed Lightweight Foamed Concrete with Dispersed Reinforcement
## 3 Results and Discussions
### Water Absorption
The higher absorption of merino wool is attributed to its natural hydrophilic properties and high capillarity, which enable rapid water uptake and retention. Conversely, synthetic fibers such as polypropylene (PP), while hydrophobic, exhibit faster initial absorption in printed samples due to the open-pore structure facilitating early water ingress. Glass fibers, although non-porous, produce absorption values comparable to hydrophilic fibers like merino wool, indicating that they influence the pore structure in a manner conducive to water penetration. Coconut fibers, known for their porous structure, exhibit the highest water absorption across all fiber types, reinforcing their propensity for water uptake and retention over time. Fiber-free reference samples consistently display the lowest water absorption coefficients in horizontal orientations, regardless of the preparation method. This highlights the structural role of additives in water absorption behavior. Materials with larger pores typically absorb water more rapidly due to reduced capillary resistance but exhibit lower overall water-holding capacity because of limited structural volume for retention. Conversely, materials with smaller pores absorb water more slowly due to higher capillary forces but can retain larger volumes over time, owing to their denser pore network. The water absorption behavior demonstrates no direct correlation between the rate of absorption and the total absorption coefficient. For example, materials with larger suction surfaces (e.g., horizontally oriented samples) exhibit faster initial absorption but may reach a lower total capacity. Conversely, materials with smaller suction surfaces absorb water more gradually but retain greater volumes over time. The open-pore structure characteristic of 3D-printed samples accelerates initial water absorption but limits total water retention. This behavior is linked to the higher density of printed samples, which, on average, is 10% greater than that of molded samples, reducing the void space available for water storage. Furthermore, the orientation of printed layers significantly influences water absorption characteristics by dictating the distribution, connectivity, and accessibility of the pore network. Vertically oriented samples, with greater exposure to open pores, facilitate faster water penetration. In contrast, the uniform structure of molded samples reduces initial absorption rates while increasing water retention capacity. Hydrophilic fibers, such as coconut and merino wool, enhance water absorption rates, particularly in printed samples where the open-pore structure facilitates rapid ingress. In contrast, hydrophobic fibers, including basalt, glass, and polypropylene, reduce water absorption rates but do not necessarily limit overall water retention. The observed anisotropic water absorption behavior in 3D-printed samples has direct implications for the long-term durability and performance of foamed concrete structures. Higher absorption rates in the vertical orientation, particularly in fiber-reinforced mixtures, suggest an increased risk of moisture ingress along interlayer boundaries, which could accelerate degradation processes such as freeze-thaw damage, sulfate attack, or carbonation in service conditions. Conversely, the reduced absorption in the horizontal orientation indicates improved resistance to moisture-related deterioration along the printed layers, highlighting the potential for directional optimization in structural applications. Moreover, the enhanced initial absorption in printed samples compared to molded counterparts underscores the necessity of surface treatments or admixtures to mitigate early moisture penetration while preserving the material's overall permeability for controlled drying. The differences in water retention between fiber types also suggest that hydrophilic fibers, such as coconut and merino wool, may contribute to prolonged internal moisture exposure, potentially affecting long-term mechanical performance and shrinkage behavior [61; 62].