Summary and Conclusions

Because of the high strength, stiffness, and load distribution characteristics provided by the concrete surface, rigid pavements do not necessarily require a strong foundation. It is more important that the foundation provides uniform support to the concrete slabs.

Although the primary purpose of base/subbase layers in a rigid pavement system is to prevent pumping, these layers provide additional advantages, such as more uniform support to the concrete slabs compared to the subgrade, a more stable working platform for construction equipment, and improved control of soil expansion and differential frost heave. However, a rigid pavement system does not always require a base or a subbase layer; the engineer should study the available data and site conditions to decide whether a base layer is warranted. Furthermore, if a base layer is to be used, the engineer should consider the different base types while considering the available materials and their cost.

Irrespective of the type of base used, the best results are obtained by:

• Selecting a base (or a combination of base and subbase) material that is not prone to pumping.
• Selecting materials that will remain stable over time.
• Selecting a base type that does not exhibit excessive deflections under traffic loading.
• Treating the surface of cementitious bases to prevent bonding and reduce friction at the interface of the PCC and base.
• Specifying a gradation or other material controls that will ensure a consistent base along the length of the project.
• Specifying and constructing the base with grade controls that allow for consistent thickness and smoothness of the PCC.

Congratulations, you have completed the knowledge section of the course.

You may now complete the course by successfully passing the course quiz.