Design Guide for Semirigid Pavements in China Based on Critical State of Asphalt Mixture

Semirigid pavement is a type of pavement structure in which a semirigid base layer, usually made up of cement-treated base (CTB) or cement-stabilized base (CSB), is overlaid with a top flexible layer of asphalt mixture. Because a considerable amount of fly ash or other waste materials can be used in CTB or CSB and less petroleum-based virgin asphalt binder is required, semirigid pavements are a type of environmentally friendly and sustainable pavement structure. This paper presents a new approach for semirigid pavement design in China based on the concept of surface deflection at the critical state of the top asphalt mixture layer. On the basis of results from an extensive survey of over 50 highway sections in eight provinces in China, a quantitative relationship was developed between allowable surface deflection at critical state of pavements and accumulative standard axle load, from which an allowable surface deflection at the end of pavement service life was recommended for semirigid asphalt pavements. A method was then proposed to convert the allowable deflection at the end of pavement service life to the design deflection at the initial state of pavements. Finally, a new Chinese design guide for semirigid pavements was developed using the surface deflection at the initial state of pavement as a design criterion. The proposed pavement design guide was validated with two example projects.