Laboratory-prepared iron oxide coatings on coarse-grained soils as residual soil simulants

Iron oxide coatings are present in soils as a result of chemical and physical weathering. However, unlike some fabric cements, e.g., calcium carbonate, iron oxide coatings occur through chemical, not physical, bonding between particles. The objectives of this research are to describe the laboratory preparation of chemically-bonded hematite coated sands which can be used for geotechnical studies, and to present index characterization results of these materials. Ottawa sands were coated with hematite via a heterogeneous suspension reaction under controlled pH and ionic strength. The presence of adsorbed hematite on the sand surface was demonstrated by XRD patterns and SEM images. Results show that hematite coatings on sands increase specific gravity, decrease hydraulic conductivity, decrease limiting void ratios, and provide the sands with a hydrophilic character, with no particle shape change. These results suggest that laboratory-prepared hematite coated sands are good simulants of the coarse fraction of oxisols, ultisols, and ferricretes.