Filling or compaction sand is typically a clean, well-graded sand used to fill voids or trenches during construction projects. Its primary purpose is to fill spaces and provide a compact, level surface that is stable and load-bearing. This type of sand has a balance between coarse and fine particles, which makes it highly compactable, ideal for use under foundations, road bases, and retaining walls. Compaction sand ensures that there are no air gaps or loose areas in the ground, which could lead to instability in construction projects.