A wide use of engineering and natural materials with microstructure makes it necessary to develop methods of describing mechanical behaviour of structures made of these materials. Yet, despite extensive research many aspects of fracture initiation and propagation in such materials remain unclear. We consider Mode I crack in particulate materials whose constituents are able to rotate. We model such materials in 2D as an idealised slightly cemented granular material where circular shaped thin discs are glued together. In order to model the crack, the bonds between a few pairs of discs are removed with crack opening being introduced by a thin wedge. Rotations of the particles are analysed using physical experiments, an analytical model and a DEM numerical simulation. It is found that the DEM simulations give results very close to the experimental ones. Furthermore, the particle rotations during fracture propagation can be well described by the pseudo-Cosserat continuum with constrained microrotations.