Combined pulse velocity measurement, flexural strength testing, and Westergaard analysis: Performance evaluation of fly ash concrete for rigid pavement material

This study investigates the performance of fly ash (FA) concrete as a rigid pavement material through a combined evaluation of ultrasonic pulse velocity measurement, flexural strength testing, and Westergaard analysis. As urban expansion increases demand for durable infrastructure, replacing conventional cement with FA offers a sustainable alternative while utilizing industrial by-products. The primary objective is to assess the mechanical and structural behaviour of FA concrete with varying substitution levels, aiming to validate its field applicability for rigid pavement systems. Four concrete mixtures with 0%, 15%, 30%, and 45% fly ash were prepared. Flexural tests evaluated stress-time and stress-deflection behavior, while ultrasonic pulse velocity tests assessed internal compactness. Additionally, dynamic and static modulus of elasticity were derived from data and applied in Westergaard’s analytical model to determine theoretical stress and deflection responses under certain loading position. Results show that the 15% FA mixture achieved the highest flexural strength (2.72 MPa), deflection (1.11 mm), and UPV (4.14 km/s), indicating enhanced ductility and internal compactness. Both dynamic and static moduli peaked at this replacement level, reflecting superior stiffness. Westergaard analysis revealed that all mixtures met or exceeded theoretical performance thresholds, with the 15% FA concrete supporting the highest load (8.84 tons) at 40 cm slab thickness. Beyond 15% replacement, mechanical and structural properties declined due to diminished matrix cohesion and binder dilution. In conclusion, moderate FA substitution at 15% optimally balances strength, stiffness, and durability, supporting its application in rigid pavement construction. This integrated evaluation approach offers practical guidance for sustainable pavement design using FA concrete.