Backcalculation Models to Evaluate Light Falling Weight Deflectometer Moduli of Road Foundation Layer Made with Bottom Ash Waste

Abstract

Incinerator bottom ash (IBA) is a residue from burning household waste that once was put into landfills. Nearly two-thirds of this ash is reused, primarily in road construction. In this study, IBA was mixed with limestone to produce a blend with acceptable properties for use as a road foundation layer. In situ simulative testing with a light falling weight deflectometer (LFWD) and subsequent interpretation of the surface deflection data have enabled evaluation of the mechanical properties of the foundation and subgrade layers. An experimental and modeling study of the elastic dynamic response of a foundation layer of IBA waste and limestone that was subjected to LFWD impact loading is presented. Several parameters—such as IBA content, water content, and curing time—were studied. Regression, mathematical, and three-dimensional finite element models were developed to backcalculate the LFWD moduli of the foundation layers. The modeling approach accounted for the static and impact nature of the LFWD load. Results showed that IBA blends underwent less deflection, as a foundation layer, than the control limestone blend. Backcalculated modulus results based on the dynamic effect of the LFWD load produced different values from those calculated by Boussinesq's equation, which is adopted by the LFWD manufacturer.