What materials are used to create sleeves for items passing under concrete?

Using metal, cardboard, and plastic to create sleeves for items passing under concrete is a practical choice because these materials offer durability and protection. Metal provides strong and weather-resistant properties, which is crucial in maintaining integrity when buried and under pressure from the concrete above. Cardboard can be used as a temporary liner or form, especially in light applications where it might be needed for ease of placement before more permanent materials are applied. Plastic is a highly versatile material that is resistant to moisture, decay, and various soil conditions, making it an excellent choice for creating sleeves that need to withstand environmental factors while ensuring that the items they encase remain unobstructed. This combination reflects a balanced approach to durability, ease of installation, and resilience under concrete structures.