Description:

CBR Proctor Mould

The CBR Proctor Mould, CBR (California Bearing Ratio) Proctor Mould is a specialized cylindrical mold used in the laboratory compaction of soil samples for CBR testing. The CBR test is a standard method used to evaluate the strength and load-bearing capacity of subgrade soils and base materials for road construction and pavement design.

The Proctor Mould consists of the following main components:

1. Cylinder: The primary part of the CBR Proctor Mould is a cylindrical container typically made of metal, usually steel or aluminum. The standard size of the cylinder has an internal diameter of 152 mm (approximately 6 inches) and a height of 177.8 mm (approximately 7 inches). The cylinder is open at the top and closed at the bottom.
2. Collar or Extension Collar: A detachable extension collar is often used to increase the height of the mold for compaction of larger soil specimens. The collar typically adds an additional 50.8 mm (2 inches) to the height of the standard mold.
3. Base Plate: The base plate is a smooth, flat, and rigid plate that covers the open bottom of the cylinder. It ensures that the soil remains confined within the mold during the compaction process.
4. Spacer Disc: The Proctor Mould usually comes with a spacer disc, which is a circular plate that fits inside the cylinder and rests on the base plate. This spacer disc helps in the correct placement of the soil sample and ensures uniform compaction.
5. Rammer or Compaction Hammer: A standardized rammer or compaction hammer is used to compact the soil sample inside the mold. The rammer has a specific weight and is dropped from a predetermined height during compaction.
6. Collar Locking Screws: When using the extension collar, there are typically screws or clamps on the side of the mold to secure and lock the collar in place during compaction.

The CBR Proctor Mould is used in conjunction with the Proctor compaction test method to determine the maximum dry density and optimum moisture content of the soil sample. Once the soil is compacted, it is then removed from the mold, and the CBR test is conducted on the compacted specimen. The CBR value is expressed as a percentage and represents the ratio of the force required to penetrate a plunger into the soil at a given depth to the force required to penetrate the plunger into a standard crushed stone material at the same depth. CBR Proctor Mould

The CBR value is an essential parameter in designing and evaluating the performance of flexible pavements, as it helps engineers assess the strength of the subgrade soil and select appropriate thicknesses for pavement layers.