ICAO Seminar on Aerodrome Physical Characteristics and Pavements By Dr.M.W.Witczak Invited Speaker Held at ICAO South American Regional Office Lima, Peru 6 – 9 August 2013 An Overview of the New AASHTO MEPDG Pavement Design Guide FEATURES OF THE AASHTO M-E PAVEMENT DESIGN GUIDE  Developed under the US NAS (National Academy of Sciences)– NCHRP (National Cooperative Highway Research program)  $10,000,000 – 7 Year Effort (Largest Single US Transportation Research Project in the History of the US)  Project Team Leaders  AC/Flexible Pavements: Dr. M.W.Witczak  Rigid Pavements: Dr.M.Darter Introduction  Road and Highways are a very significant cost for agencies to construct, maintain and rehabilitate (US Infrastructure worth $1,000,000,000,000)  Pavement design is a very complex process that involves many variables as well as the variation of each variable. It is one of the most complex Civil Engineering structures to design because we demand a FS=1.0  Mechanistic concepts provide a more rational and realistic methodology for pavement design; however, pavement response models are mathematically very complex and do not have single closed form equation solution.  The M-E PDG provides a consistent and practical method to design a pavement for a desired level of reliability. 4 The MEPDG considers a wide range of AC  Flexible pavement structural sections for : New pavement systems  Overlay pavement systems  5 Conventional Flexible Pavements  Deep Strength HMA Pavements  Full-Depth HMA Pavements  "Semi-Rigid" Pavements  6  HMA Overlay over Existing HMA: New Existing AC Conventional AC  AC Deep strength HMA pavements  AC Full depth asphalt  AC Semi-rigid pavements   HMA over JPCP  HMA over CRCP 7 HMA over Fractured JPCP  Crack and Seat  Rubbilization  HMA over Fractured CRCP  Rubbilization  8  The primary distresses considered in the MEPDG for flexible pavements are: Permanent Deformation (rutting)   AC Layers  Unbound Base/Subbase/Subgrade Layers  Total Rut Depth Fatigue Cracking   Top Down-Longitudinal Cracking  Bottom Up- Alligator Cracking Thermal Cracking   In addition, pavement smoothness (IRI) is predicted based on these primary distresses and other factors. 9 Major Asphalt Pavement Distresses  Major pavement distresses Permanent deformation  Fatigue cracking  Transverse (Thermal) cracking  •How can we simulate these problems in the lab? Asphalt 10