Micro-structural and volumetric behaviour of bimodal artificial soils with aggregates

Bimodal soils with aggregates present a complex micro-structural and volumetric behaviour. This occurs because they showcase several variables, such as mineralogical, different grain sizes and structures. The objective of this paper is to develop a methodology for producing soils with aggregates and simple, non mineralogical variability and controlled double porosity. In this sense, aggregates using Kaolin were created to obtain bimodal samples. The aggregates produced with this methodology were stable in water and the bimodal samples were analysed by means of Mercury Intrusion Porosimetry (MIP), Scanning Electron Microscopy (SEM), Soil Water Retention Curve (SWRC) and analysis of the shrinking process. Results show that the presence of aggregates in different proportions has a direct impact on soil's: plasticity; classification; compaction curve; retention curve; as well as the pore size distribution (PSD), where micro and macro pores were observed. The shrinking and expansion analysis of the samples show that the presence of aggregates reduced both the expansive and shrinking potential. During the analysis of the shrinking process a fitting equation is presented to describe the trend of volumetric strain of the samples, from which it was possible to separate the soil shrinking process associated with the drying of the macro and microstructure and its relationship with the retention curve. Therefore, this study contributes to a better understanding of the role of aggregates on the microstructural and volumetric behaviour of bimodal soils.