BACKGROUND: In jointed plain concrete pavements (JPCP) and continuously reinforced concrete pavements (CRCP), the concrete slab is placed on a base layer that may consist of a wide variety of unbound, asphalt-stabilized, cement-stabilized, lime-stabilized aggregates; lean concrete; recycled concrete pavement; recycled asphalt pavement; and other materials. The base layer may be dense graded or permeable drainage layers.  JPCP and CRCP overlays are also placed over existing rigid pavements, composite pavements, and flexible pavements for the rehabilitation of these pavements. The AASHTO Mechanistic-Empirical Pavement Design Guide Manual of Practice (MEPDG) developed under NCHRP Project 01-37A provides a methodology for the analysis and performance prediction of such concrete pavements and overlays. This methodology makes certain assumptions regarding the contact and sliding friction between the concrete slab and base of new pavements and between the concrete overlay and the underlying pavement. However, these assumptions do not appear to adequately consider all aspects of the interaction between the concrete slab and underlying layer. For example, the methodology does not consider the incremental change in the level of friction or bonding during the pavement service life and its effect on pavement performance, the likely difference in the level of bonding contributed by the different base materials, or the influence of construction practices. The omission of these factors from consideration could lead to underdesigned or overdesigned pavement structure. Research is needed to (a) identify the factors that influence this interaction between the concrete slab and underlying layer (e.g., layer type and properties, placement practice, and climate), (b) estimate the expected change over the service life of the pavement for a variety of materials and conditions, (c) determine its effect on pavement performance, and (d) develop a mechanistic-empirical model that considers such interaction in the design and analysis of concrete pavements. Such a model can be incorporated into the MEPDG procedures to allow a more rational analysis and design of JPC and CRC pavements and overlays.

 

OBJECTIVE: The objective of this research was to develop a mechanistic-empirical model (and associated computational software) for considering the interaction between the concrete slab and underlying layer and its effect on pavement performance. The model was intended to be appropriate for use with the MEPDG procedures for concrete pavement analysis and design. The research dealt with both jointed plain concrete and continuously reinforced concrete pavements and overlays.

 

STATUS: Research is complete; the final report is available as NCHRP Web-Only Document WOD 236, Incorporating Slab/Underlying Layer Interaction into Concrete Pavement Analysis Procedures.