# 3D-Printed Lightweight Foamed Concrete with Dispersed Reinforcement
## 4 Conclusions  
This study investigated the impact of dispersed fiber reinforcement on the properties and printability of 3D-printed foamed concrete. The findings indicate that a higher fiber content (1 wt.%) significantly impeded the printing process, with specific fibers, such as polypropylene, rendering extrusion entirely unfeasible due to nozzle clogging. Reducing the fiber content to 0.5 wt.% improved material flowability and minimized printing defects. Additionally, mixtures incorporating coal slag with stiff fibers, such as basalt and glass, achieved the highest flexural strength, while merino wool fibers enhanced the mechanical performance of fly ash-based mixtures.  
This study also revealed that printed samples exhibited higher flexural strength compared to molded specimens, primarily due to microstructural modifications introduced by the 3D printing process. However, fiber selection and printing conditions significantly influenced performance, emphasizing the importance of optimizing fiber type, concentration, and processing parameters. Natural fibers, such as coconut and wool, contributed to crack-bridging effects, further enhancing mechanical properties.  
Figure 19: Pore size distribution in molded samples: (**a**) B1/SL/B05 (3.21 MPa), (**b**) B1/FA/M05 (2.80 MPa), (**c**) B1/FA (1.72 MPa).  
Water absorption varied significantly depending on the fiber type and its interaction with the cementitious matrix. Natural fibers, including merino wool and coconut, exhibited higher water absorption due to their hydrophilic nature and capillary action, particularly in 3D-printed samples with an open-pore structure. In contrast, hydrophobic fibers, such as polypropylene, basalt, and glass, contributed to reduced water retention, which may affect the material's durability and potential applications.  
Moreover, 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 specific fibers, likely enhances material densification and structural integrity. This characteristic may explain the relatively high flexural strength observed in these samples. Additionally, the addition of foam in a 1:1 ratio is easier to control during the printing process, allowing for a more uniform pore structure and improved mechanical performance. However, in molded samples, this foam ratio is excessively high, leading to increased porosity and reduced mechanical strength. The presence of larger and more irregularly distributed pores in molded samples creates structural weaknesses, further diminishing their overall performance.  
Future research will focus on hybrid fiber reinforcement strategies, combining flexible natural fibers with rigid synthetic fibers to improve mechanical performance. Additionally, the thermal resistance of the tested materials will be assessed to better understand their suitability for construction applications.  
Conceptualization, M.R., K.K. and M.H.; methodology, M.R.; software, A.H.; validation, M.R., M.M. and M.H.; formal analysis, M.R. and M.H.; investigation, M.R. and M.M.; resources, M.R. and M.H.; writing--original draft preparation, M.R.; writing--review and editing, M.R., K.K. and M.H.; visualization, M.M. and A.H.; supervision, K.K. and M.H.; project administration, M.R. and M.H.; funding acquisition, M.R. and M.H. All authors have read and agreed to the published version of the manuscript.  
This research has been supported by the Ministry of Education and Science within the program \"Implementation Doctorate\", DWD/6/0528/2022.  
Not applicable.  
The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding author.  
The authors declare no conflicts of interest.