Theoretical Investigation and Parametric Sensitivity Analysis of Polypropylene–Polyester Fiber-Reinforced Recycled Brick Aggregate Concrete Pavement Humidity Warping Stress During the Service Life

Pavement humidity warping is a critical factor limiting the application of PPRBAC on low-volume roads. A nonlinear wet-warping stress formula for PPRBAC slabs has been derived based on previous experimental results, and the finite element method was employed to develop a single-board model in order to verify the accuracy of the analytical solution. Subsequently, the finite difference method, in conjunction with the finite element method, was employed to investigate the calculation methodology for wet-warping stress in PPRBAC slabs during service. Finally, the Taguchi-GRA (gray relational analysis) method was selected to analyze the sensitivity of humidity warping factors affecting PPRBAC slabs. The findings indicate that compared to the traditional bending moment equivalent method, the wetness warping stress formula established in this study accounts for the nonlinearity of wetness warping stress and demonstrates higher accuracy. For PPRBAC pavements during the service period, assuming uniform initial humidity distribution along the height within the concrete does not align with practical observations. The calculated humidity warping stress and deformation using this assumption are 1.1 and 1.7 times those obtained from the comprehensive dry-wet calculation method. It is crucial to consider the wet stage's impact on the dry stage in the calculations. The Taguchi-GRA method objectively determines the weight of factors affecting humidity warping in PPRBAC, with slab size, thickness, and flexural strength having the greatest influence.