Recommendation of RILEM TC 280-CBE: Standardised design and analysis of the multiphase composition of bitumen emulsion–cement composites

The composites of bitumen emulsion and cement used for structural layers of road pavements are heterogeneous materials composed of bitumen emulsion and cement as co-binders, mineral aggregate as a granular skeleton, and pore space. Physicochemical interactions between phases determine the temporal evolution of the composites’ macroscopic properties. Therefore, the complex multiscale organisation of these composites with the abundance of time-dependent interactions requires a standardised approach to the design and analysis of mixtures’ and specimens’ composition, which is applicable in both experimental scientific research and industrial development of these materials. The purpose of this RILEM recommendation is to standardise a universally applicable method for the analytical quantification of the volumetric and gravimetric relations between the individual phases throughout the composite’s evolution over time (from the mixture design to the ultimate state of curing). The method proposed in this document is based on the length scale of mortar with fine aggregate (filler and sand) including the processes of specimen preparation and curing. This approach also enables a consistent and reproducible characterisation of the influence of the co-binders’ intrinsic properties on the overall physicochemical and mechanical behaviour of their mixtures in pavement layers. Three dominant processes considered by this methodology are (1) breaking of emulsion, (2) hydration of cement, and (3) evaporative drying. Although this method unifies the design of fine-aggregate model systems as structural components of pavement layers, the developed relations are generally applicable for any range of the particle size distribution.