The role of fine aggregate matrix in the linear viscoelastic behaviour of cement-bitumen treated materials

The use of cold recycling technologies, including cement-bitumen treated materials (CBTM), is rising to address the environmental and economic challenges required for implementing sustainable road pavements. However, to obtain performances comparable to those of hot bituminous mixtures, the advanced study of these relatively new materials is essential, also considering the analysis of the linear viscoelastic (LVE) behaviour. This research studies the complex modulus of fine aggregate matrix (FAM) mortars, representative of the binding matrix of CBTM mixtures, characterised by several compositions. The experimental results were modelled considering both viscous and time- and temperature-independent dissipation components. Findings showed that the LVE behaviour of FAM mortars strongly depends on their composition, especially in terms of bituminous components, i.e. fresh and aged bitumen, and cement. Besides, the aged bitumen coating the reclaimed asphalt aggregate plays a role in the LVE response of CBTM mortars and mixtures.