This paper describes the implementation of the bonded concrete overlay of asphalt pavement mechanistic–empirical (BCOA-ME) design procedure, developed by the University of Pittsburgh, into the AASHTOWare Pavement ME Design software. The BCOA-ME procedure was generally compatible with the mechanistic–empirical framework of Pavement ME and thus adaptable into the design framework. A thin bonded concrete overlay of existing asphalt pavements includes short to medium joint spacings (typically 6 × 6 ft) and a strong bond or high-contact friction between the portland cement concrete slab and the existing asphalt concrete surface. As much of the theory, concepts, assumptions, and inputs in the BCOA-ME design procedure as possible were implemented into the Pavement ME software. Differences included those required to match the computational procedures of Pavement ME (e.g., axle load spectra versus equivalent single-axle loads, monthly asphalt concrete damaged dynamic modulus, monthly portland cement concrete strength and modulus, and monthly unbound material resilient modulus). Longitudinal joint spacing ranging from 5 to 8 ft (not <5 ft) was included. Longitudinal fatigue cracking was directly considered as in the BCOA-ME, which initiates at the bottom of the slab. The calibration of the longitudinal cracking transfer function produced excellent goodness-of-fit statistics with no significant bias. The new procedure was incorporated into Pavement ME Version 2.3, released in July 2016.

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Semirigid pavements are composite pavements that comprise a surface asphalt concrete (AC) layer overlying a cement stabilized base, granular subbase, and subgrade foundation. When subjected to traffic and climate loading, semirigid pavements provide good performance through resistance to rutting or deformation of base and subgrade, moisture damage, and AC fatigue. However, semirigid pavements can develop fatigue and transverse shrinkage cracks in the underlying cement stabilized base layer, which ultimately propagates through the surface AC thickness with repeated applications of axle loads and temperature cycles (i.e., reflection cracking). Although new semirigid pavements have been designed and constructed in the United States since the 1960s, a new semirigid pavement design methodology was not included in Version 1.0 of AASHTOWare Pavement ME Design software. This methodology was omitted because developers and researchers at that time concluded that there were no suitable existing mechanistic-based fatigue or transverse reflection cracking models available to be adapted and included in the design procedure. Under NCHRP Project 1-41—Models for Predicting Reflection Cracking of Hot-Mix Asphalt Overlays, mechanistic-based AC fatigue and transverse reflection cracking models were developed. The models were developed to be compatible and thus easily adaptable into the AASHTOWare Pavement ME Design framework. Work done to adapt the NCHRP Project 1-41 reflection cracking models for the design of new semirigid pavement in AASHTOWare Pavement ME Design is presented.