✅ROAD CONSTRUCTION LAYERS 📌1.SUBGRADE ( Bottom Layer) ■Subgrade : 150 - 300 mm ■Natural soil compacted to required strength, forming the road’s foundation. Stabilized if weak. 📌2. SUB-BASE COURSE ■Sub-base course : 100 - 300 mm ■Granular materials like gravel add strength, improve drainage, and protect the subgrade from moisture; optional if subgrade is strong. 📌3. BASE COURSE ■Base course : 100 - 300 mm ■Crushed stone or stabilized layers (WBM/WMM) provide structural support and distribute m