Re-evaluation of continuously reinforced concrete pavement structural model

Transversal shrinkage cracks are allowed to develop freely at the slab’s surface of continuously reinforced concrete pavements (CRCP). It is commonly believed that cracking pattern significantly affects CRCP performance: small crack spacing (cluster cracking) is considered to be problematic due to the higher potential for cracks intersection and punchout development whereas large crack spacing can be detrimental for load transfer efficiency (LTE) at the crack due to the development of wider cracks. The Mechanistic-Empirical Pavement Design Guide (MEPDG) procedure for prediction of critical structural responses in CRCP is based on ISLAB2000 finite element model with constant crack spacing and equal LTE for every crack. The critical stresses are assumed to be at the top of the CRCP surface mid-distance between the cracks. However, results of experimental studies suggested that this model may not adequately describe CRCP’s structural behavior. This paper presents a re-evaluation of the procedure for critical stress predictions. A finite element model with a variable crack spacing was developed. Different load positions, thermal differentials, crack LTE levels, axle types and voids were also simulated. Results point out that the location of critical stresses depends on many parameters, including crack spacing, magnitude of temperature gradients, type of axle load and presence or not of voids. Therefore, other modes of punchout initiation, currently not taken into account in the MEPDG, should be considered in the design process.