Fresh state stability of vertical layers of concrete

The production of cement is currently associated with around 5% of global carbon emissions. The manufacture of functionally graded structural elements, where the material composition is varied over the volume, allows the use of cement to be optimized and minimized. Horizontal gradation of material properties can be achieved by casting vertical layers having homogeneous composition. However, a key problem in this application is the control of the fresh state deformations of the layers. This study investigates for the first time the fundamental problem of the fresh state stability of two vertical layers of different mixes. Original experiments are designed to invoke stable and unstable behaviour. Two novel limit-state models are formulated to assess the stability of the system as a function of material properties and geometry. The results show that a relationship between system stability, geometry and material parameters exists, and that it is captured by the presented models.