Flow of self-compacting concrete

This thesis describes the steps taken to develop self-compacting concrete (SCC) mixes with and without steel fibres. For the self-compacting concrete mixes without steel fibres the fulfilment of the flow and cohesiveness criteria are found to be sufficient for the mix design. However, for the design of self-compacting concrete mixes with steel fibres it is found that they must additionally meet the passing ability criterion. The plastic viscosity of SCC mixes with and without fibres so developed is accurately estimated using a micromechanical procedure based on the measured viscosity of the cement paste alone and on the mix proportions. A Lagrangian particle based method, the smooth particle hydrodynamics (SPH), is used to model the flow of SCC mixes with or without short steel fibres in slump and L-box tests. An incompressible SPH method is employed to simulate the flow of such non-Newtonian fluids whose behaviour is described by a Bingham-type model, in which the kink in the shear stress versus shear strain rate diagram is first appropriately smoothed out. The basic equations solved in the SPH are the incompressible mass conservation and momentum equations. The simulation of the SCC mixes emphasised the distribution of large aggregate particles of different sizes throughout the flow in the 3-dimensional configurations. On the other hand, the simulation of high strength SCC mixes which contain steel fibres focused on the distribution of fibres and their orientations during the flow in the 3-dimensional configuration. The capabilities of this methodology were validated by comparing the simulation results with the slump flow and L-box tests carried out in the laboratory. A simple method is developed to assess the orientation and distribution of short steel fibres in self-compacting concrete mixes during the flow. A probability density function (PDF) is introduced to represent the fibre orientation variables in three dimensions. Moreover, the orientation variables of each individual fibre in an arbitrary two dimensional cross-section have been calculated using the geometrical data obtained from the three dimensional simulations. This is useful to determine the fibre orientation factor (FOF) in practical image analysis on cut sections. The simulations of SCC mixes are also used as an aid at the mix design stage of such concretes. Self-compacting concrete mixes with and without steel fibres are proportioned to cover a wide range of plastic viscosity. All these mixes meet the flow and passing ability criteria, thus ensuring that they will flow properly into the formwork