The project provided improved guidelines for consideration of structural support in the design of portland cement concrete pavements.

Concrete pavement performance depends greatly on the support that it receives from the base course and underlying soil layers as well as other support-related factors such as erosion, curling, and warping. There is no general agreement among pavement engineers on how to select values for the modulus of subgrade reaction and the loss of support for use in design of rigid pavements and rigid pavement overlays. A perceived lack of adequate guidance in the AASHTO Guide for Design of Pavement Structures has resulted in inconsistent design practices for concrete pavements. Therefore, guidelines are needed to ensure proper consideration of support in pavement design.

The project examined support concepts and causes of loss of support, reviewed related data from numerous field studies, adapted a three-dimensional finite element model to analyze the effects of support on pavement response to traffic and climatic conditions, and proposed guidelines for improving the consideration of support in the AASHTO design procedure for concrete pavements. NCHRP Report 372 documents the work performed under this project. The unpublished appendices can be found here: