Optimal Structure Combination for Inverted Asphalt Pavement Incorporating Cracks in Cement-Treated Subbase

The structure design and mechanistic calculation of inverted asphalt pavements are mainly based on linear layer elastic theory with the assumption that the cement-treated subbase (CTB) is complete without cracks. This study investigates the optimal structure combination for inverted pavements according to calculated critical responses considering cracks in the CTB layer. A three-dimensional finite element (3D FE) model of inverted pavement with a transverse crack through the CTB layer was developed. Four full-scale inverted pavement sections were built, and a crack 0.01 m wide and 0.05 m deep was sawn on top of each CTB layer after construction. The 3D FE model was validated by strain and deformation measured in falling weight deflectometer tests and used for a parametric study of dominating structure combination factors. Variance analysis results show that interactions with thickness or stiffness of the asphalt concrete (AC) layer presented the most significant effect on critical responses, while CTB stiffness (12588 similar to 7668 MPa) had the least impact. Structure variation effect analysis results illustrated that 0.1 m aggregate base (AB) thickness is enough to prevent the CTB crack propagating to the surface. Thin AC structures are highly sensitive to variations in AC and AB stiffness. A thin AC and AB combination (0.05 and 0.10 m) can provide low critical strains similar to a thick AC and thin AB (0.15 and 0.10 m) combination if the stiffness of AC and AB can be maintained at 7175 and 358 Mpa, respectively, or higher. AC thickness of 0.1 m and the combination of thin AC and thick AB are two unfavorable conditions for inverted pavements.