The physico-chemical processes of water adsorption into water saturated shale rocks have been extensively studied in the past. However, the physico-chemical processes of water uptake into partially saturated shales, such as water loss to fractured organic-rich shales during hydraulic fracturing, are poorly understood which in turn has raised serious technical and environmental concerns. Therefore, we ran a series of experiments on partially saturated calcareous shale samples, with measured total organic carbon (TOC) of 1.935% and mean vitrinite reflectance (Ro) of 0.52%, to identify the potential mechanisms involved in the water uptake. The physico-chemical properties such as mineral and elemental compositions, initial water saturation and contact angles of solutions with different concentrations were measured. Free and confined adsorption tests were then performed on both the intact and artificially fractured shale samples. The experimental results of this study are explained by two proposed mechanisms; capillary hydration and surface-osmotic hydrations that can combine to influence the amount of water uptake into partially saturated shales. The results show that the crack initiation is a strong function of confining stress and cracks are formed parallel to weak structures of the rock (bedding planes and laminations). The results also reveal that the mineral hydration controls the permeability (and consequently water flow) of existing fractures within the shale sample. (C) 2015 Elsevier Ltd. All rights reserved.