Microscale characterization of an anti-cracking stone base course filled with cement stabilized macadam

Abstract

Large stone base course filled with cement stabilized macadam (LSFC) is a promising solution for addressing reflection cracks in semi-rigid base asphalt pavements due to its superior crack resistance. However, challenges associated with balancing strength and crack resistance, and mechanizing high-efficiency construction have hindered broader adoption. To address these issues, Wang et al. [1] proposed an optimized mix proportion design for an anti-cracking stone base course filled with cement stabilized macadam (SFC). In this study, various microscopic techniques were employed to explore the anti-cracking mechanism of SFC on a microscopic scale, and compared with the conventional cement stabilized macadam (CSM). These techniques included examining the structural morphology and pore distribution using polarizing microscope (PM) and nuclear magnetic resonance (NMR), analysing the elemental composition and hydration reaction in non-aggregate zones using energy dispersive spectroscopy (EDS), and testing the mechanical properties using atomic force microscope (AFM). The findings revealed, compared with CSM, SFC exhibits a more tightly interlocked coarse aggregate skeleton, which, in turns, resulting in weak interfacial transition zones (ITZs) with a high concentration of pores and defects, weak bonding, and a loose structure, potentially exceeding 20 µm in thickness. The tightly interlocked coarse aggregate skeleton in SFC effectively limits material shrinkage but also leads to localized high stress and weak interfacial damage within the vulnerable ITZ region, converting shrinkage strain energy into microcrack surface energy, thereby delaying the onset of cracking and ultimately enhancing the cracking resistance of the base.