Design of a parallel plate shearing device for visualization of concentrated suspensions

[Display omitted] •A modified version of the existing shearing device “RheOptiCAD®”.•Upright microscope instead of inverted one with the epi-illumination.•CMOS camera instead of CCD with square pixels and less smearing and blooming.•Promising analysis of structural behaviour of concentrated suspensions under shear. A modified version of the commercially available RheOptiCAD® was developed to visualize the microscopic structural changes occurring in concentrated suspensions, such as the break-up of flocs in clay suspensions, under shearing action. This is made possible by replacing the inverted microscope used in the traditional RheOptiCAD® set-up by an upright modular microscope equipped with a CMOS camera and epi-illumination. Our device retains the following features of the previous version of RheOptiCAD®: [i] uniaxial translational motion of two parallel plates, [ii] three modes of shear straining, [iii] controlled thermal environment, and [iv] vacuum joining of microscopy glass slides. The validation of the new design was done using a model system of un-flocculated and flocculated kaolin suspensions and concentrated natural mud suspension. The results showed that the constructed device is a promising tool for studying, from fundamental and industrial perspectives, the microstructural behaviour of complex suspended systems under controlled thermal and mechanical conditions.