On the use of Derjaguin-Muller-Toporov (DMT) modulus distribution for quantifying the efficacy of recycling agent

Abstract

Quantifying the efficacy of recycling agents (RA) is crucial to determine the optimal dosage for recycling Reclaimed Asphalt Pavement (RAP) materials. Atomic Force Microscopy (AFM) is used to capture the microstructure of binders and qualitatively observe the dispersing effect of RA. However, the magnitude to which RA influences the aged binder at microscale remains unclear. To address this, the changes in properties of different regions in the microstructure are quantified using the Derjaguin-Muller-Toporov (DMT) modulus and the characteristics of its frequency distribution. The variations in these characteristics across RA dosages provide insights into the relative changes in softening and dispersion effects. Laboratory-aged binders are blended with different RA dosages, and the microstructure images revealed that the dispersion effect plateaued beyond 10% RA. Frequency distribution of DMT modulus showed reduced mean and increased skewness with RA addition. Results suggest that RA facilitates dispersion and softening up to a 10% threshold dosage, beyond which its dispersion efficacy reduces and RA contributes to softening primarily by introducing low-modulus fractions.