# A Novel Technosol Formulation for Sustainable Landfill Top Covers Using Non-Hazardous Wastes
## 3 Results and Discussion
### Geotechnical Properties
The plasticity index of 29 further emphasizes the plastic nature of WAS. Design considerations should prioritize mixtures with liquid limits below 30 to minimize the risk of shrinkage and cracking. For instance, the blend 70 WFS/30 WAS, with its high liquid limit (LL = 33), may lead to prolonged settlement and instability issues, while mixtures with lower liquid limits, such as 90 WFS/10 WAS and 80 WFS/20 WAS, can enhance the durability and sustainability of the landfill top cover. Based on the Unified Soil Classification System (Figure 4), WAS is classified as an inorganic clay with high plasticity (CH), while WFS and mixtures of WAS with WFS (90 WFS/10 WAS, 80 WFS/20 WAS, and 70 WFS/30 WAS) are categorized as silty sands with slight plasticity (ML). Optimum moisture content results provide valuable insights into compaction behavior of mixtures, guiding sustainable landfill cover construction. The moisture content values for maximum compaction varied among samples, reflecting the influence of WFS and WAS on compaction (Table 2). WAS, with its finer texture and elevated plasticity, required a comparatively higher water content (26.95%) for maximum compaction. Conversely, WFS and WFS-containing mixtures (13.4-15.5%) exhibited lower optimum moisture content, attributed to their coarse-grained, non-plastic nature, allowing optimal compaction with reduced water content. Adding WAS into the mixture resulted in a slight increase in moisture demand for achieving optimal compaction. Mixtures with lower optimum moisture content have the potential to improve compaction efficiency by requiring less water consumption, leading to cost savings and a reduced environmental footprint. Achieving maximum dry density through compaction is essential for ensuring the stability and load-bearing capacity of landfill covers. As evident from the moisture-density (Proctor) curves (Figure 5), the blend 90 WFS/10 WAS reached the highest maximum dry  
Figure 3: Granulometric curves of the tested samples obtained by combining sieving and laser diffraction results. density value of 1.77 g cm\({}^{-3}\), indicating its superior compaction potential. This elevated maximum dry density value reflects a greater ability of the material to pack tightly, resulting in a denser structure with fewer voids, thereby enhancing stability. This translates to improved load-bearing capacity, reduced settlement potential, and greater resistance to erosion, which are crucial aspects of a sustainable landfill cover design. Conversely, WAS exhibited poor compaction behavior, yielding a lower maximum dry density value (1.50 g cm\({}^{-3}\)), thereby compromising its compaction efficiency. Analysis of void ratio variations among mixtures highlights the influence of WFS and WAS content. WAS, with its fine-grained and plastic nature, exhibited a remarkably high void ratio (0.72), suggesting an increased susceptibility to deformation. In contrast, WFS-bearing mixtures consistently displayed lower void ratio values (0.40-0.46). This suggests that WFS-based mixtures hold promise for efficient compaction and enhanced stability. Notably, increasing WAS proportions did not substantially affect the overall void content, indicating that WFS effectively counteracts the void-creating tendencies of WAS. Swelling and stability are paramount factors in the design of landfill top covers. Materials with minimal swelling and collapse potential are essential for maintaining long-term stability and preventing deformations caused by moisture variations. WAS exhibited a free swelling value of 0.25%, indicating slight expansion or shrinkage during wetting and  
Figure 4: Sample classification based on liquid limit (LL) and plasticity index (PI) values. Plasticity chart as per Unified Soil Classification System (USCS). Figure 5: Standard Proctor compaction test results of the tested samples. drying cycles. This low swelling potential is primarily due to the mineralogical composition of WAS, which is dominated by kaolinite, a non-swelling clay mineral.