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Experimental and numerical studies in self-compacting concrete

Badry, Firas 2015. Experimental and numerical studies in self-compacting concrete. PhD Thesis, Cardiff University.
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Abstract

This thesis describes the steps taken to develop normal strength (30-80 MPa) selfcompacting concrete mixes with 20mm maximum size aggregate. For the selfcompacting concrete mixes with 20mm maximum size of aggregate fulfilment of the flow and cohesiveness criteria are found insufficient for the mix design. It is found that they must additionally meet the passing ability criterion. A Lagrangian particle based method, the smooth particle hydrodynamics (SPH), is used to simulate the flow of SCC mixes. 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 Navier-Stokes equations. The yield stress of SCC mixes is predicted in an inverse manner using the SPH simulation methodology and matching the measured and simulated t500, tstop and the final spread of the cone flow test. It is found that the yield stress of SCC mixes varies only slightly with an increase in the characteristic compressive strength of the mix. The plastic viscosity on the other hand shows a marked increase. The latter was estimated by a micromechanical procedure proposed by Ghanbari & Karihaloo (2009) based on the measured viscosity of the cement paste alone and on the volume fractions of the mix constituents. The SPH simulation methodology was also used for predicting the distribution of large coarse aggregates in the cone spread. This distribution was found to be indeed very similar to that revealed in the cut sections of the hardened test cone spread. These large coarse aggregates had been painted with non-toxic non-water soluble paints prior to being used in the test mix. The simulation of SCC mixes revealed that the cone lift rate in the slump flow test has a significant effect on the flow pattern and the measured t500. The latter decreases as the cone lift rate increases from 0.1 to 1 m/s. The effect on the spread (i.e. tstop) is, however, insignificant.

Item Type: Thesis (PhD)
Status: Unpublished
Schools: Engineering
Subjects: T Technology > TA Engineering (General). Civil engineering (General)
Uncontrolled Keywords: Self Compacting Concrete (SCC); Smooth Particles Hydrodynamics (SPH); Yield Stress Ty; Coarse Aggregate Distribution; Cone Lift Rate (CLR).
Date of First Compliant Deposit: 30 March 2016
Last Modified: 15 Oct 2016 04:35
URI: http://orca.cf.ac.uk/id/eprint/83522

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