The thickness of subbase can range from 75 to 100 mm (3 to 4 in) for garden paths through 100 to 150 mm (4 to 6 in) for driveways and public footpaths, to 150 to 225 mm (6 to 9 in) for heavy used roads, and more for highways. They are rated by strength, from the weakest CBM 1 (also formerly known as soil cement) through CBM 2 to CBM 3, 4, and 5, which are more similar to concrete and are called "lean mix". Other cement bound materials (CBM), with less strength but also lower cost, are used. Mass concrete is used where exceptional loads are expected, with thickness usually 100 to 150 millimetres (4 to 6 in), and optional reinforcement with steel mesh or polymer fibers. Unbound granular materials are usually crushed stone, crushed slag or concrete, or slate.Ĭement-bound materials come in multiple types. The quality of subbase is very important for the useful life of the road and can outlive the life of the surface, which can be scrapped off and, after checking that the subbase is still in good condition, a new layer can be applied. The materials used may be either unbound granular, or cement-bound. Its role is to spread the load evenly over the subgrade. Subbase is often the main load-bearing layer of the pavement. It may be omitted when there will be only foot traffic on the pavement, but it is necessary for surfaces used by vehicles. In highway engineering, subbase is the layer of aggregate material laid on the subgrade, on which the base course layer is located. Layers in the construction of a mortarless pavement: A.) Subgrade B.) Subbase C.) Base course D.) Paver base E.) Pavers F.) Fine-grained sand
0 kommentar(er)
