Numerical Modelling of Self-Compacting

With the advent of Self-Compacting Concrete (SCC) that flows freely, under the sole influence of gravity, the wish for hassle-free and predictable castings even in complex cases, spurged the simulation of concrete flow as a means to model and predict concrete workability. To achieve complete and reliable form filling with smooth surfaces of the concrete, the reinforced formwork geometry must be compatible with the rheology of the fresh SCC. Predicting flow behavior in the formwork and linking the required rheological parameters to flow tests performed on the site will ensure an optimization of the casting process. In this thesis, numerical simulation of concrete flow is investigated, using both discrete as well as continuous approaches. The discrete particle model here serves as a means to simulate details and phenomena concerning aggregates modeled as individual objects. The here presented cases are simulated with spherical particles. However, it is possible to make use of nonspherical particles as well. Aggregate surface roughness, size and aspect ratio may be modeles by particle friction, size and clumping several spheres into forming the desired particle shape. The continuous approach has been used to simulate large volumes of concrete. The concrete is modeled as a homogeneous material, particular effects of aggregates, such as blocking or segregation are not accounted for. Good correspondence was achieved with a Bingham material model used to simulate concrete laboratory tests (e.g. slump flow, L-box) and form filling. Flow of concrete in a particularly congested section of a double-tee slab as well as two lifts of a multi-layered full scale wall casting were simulated sucessfully. A large scale quantitative analysis is performed rather smoothly with the continuous approach. Smaller scale details and phenomena are better captured qualitatively with the discrete particle approach. As computer speed and capacity constantly evolves, simulation detail and sample volume will be allowed to increase. A future merging of the homogeneous fluid model with the particle approach to form particles in the fluid will feature the flow of concrete as the physical suspension that it represents. One single ellipsoidal particle falling in a Newtonian fluid was studied as a first step.