In accumulating the success rate towards implementing inverted pavement in the United States and South Africa, an improved mechanical response in the Asphalt layer is observed. The unbounded granular aggregate in inverted pavement sandwiched between the Asphalt layer and cement-treated layer played a crucial role in minimising excessive deflection due to the stiff cement-treated or bitumen-treated layer constraint-resisting excessive deformations. In inverted pavement, layer material properties and positioning are reversed in order to analyse rutting and fatigue resistance when compared with conventional flexible pavement. Nonetheless, bitumen or cement-treated layer in pavement are neither economically viable. This study proposes fly-ash -treated base as a substitute for the cement or bitumen-treated base layer while modelling the pavement using Finite Element Analysis compared with Multi-Layered Elastic Design Method. Results from the resilient Modulus (Mr) provides a response threshold for optimum stiffness requirements. This indicates the use of empirical design methods, results to over-designing the pavement structure when compared with results from 3D FEM and Multi-Layered Elastic Design. Furthermore, 3D-FEM material characterisation using non-linear models are efficient and reliable when compared with linear models, which enhances efficiency and reliability. An adaptive mesh was used to discretise the individual pavement layer in response to actual load and material characterisation values. The results indicate that the Horizontal Tensile strain in the Inverted layer with 300mm thickness is more efficient than conventional 300mm flexible pavement under the same loading conditions. Critical failure load points, as well as deflection models, were generated to assess the life expectancy of the pavement layers.

Fly-ash; Inverted pavement; flexible pavement; finite element modelling