Microproportioning - Rheology of filler modified cement paste (matrix) with crushed aggregate fines and pozzolana
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This thesis presents a study on how crushed aggregate fines and pozzolana affects the rheological properties of a cement paste. Two approaches for investiagations of rheology properties were performed; mixing and measurements of filler modified paste, and particle size analysis of cement, fly ash and filler with the SediGraph III Plus (5125). A series of mix designs of filler modified paste, with different amount of fillers and pozzolonas, were prepared and tested with the intention of establishing knowledge about how the different materials and proportioning will affect the rheological properties of a paste. Four main rheological parameters, flow resistance, mini-slump flow, Bingham's plastic yield stress and Bingham's plastic viscosity, were found through testing in the FlowCyl, Mini-slump cone test and a rheometer with a bob-in-a-cup geometry. When the values of two and two rheological parameters was plotted in the same plot, the correlations indicated a relation between the parameters. Especially between Bingham's plastic viscosity and flow resistance, and Bingham's yield stress and mini slump-spread. An attempt to calculate yield stress from mini slump-spread was also performed. When yield stress from mini slump-spread was compared with Bingham's yield stress a reasonable fit was found with an exponential equation. The SediGraph III Plus (5125), from Micromeritics, was used to find the particle distribution and spesific surface area of Industrisement, Standardsement FA, fly ash, and Velde Fine, Intermediate and Coarse with a particle size range of 1-125 μm. The PSD of the same material shows good repeatability. The highest SSA was found with a minmum particle size of 1μm. The values of the rheological parameters and SSA of fillers were used as input values in a multi variable analysis for microproportioning, where a linear regression was approximated for estimating rheological parameters without measuring. The results of the analysis were varying, and indicated that the procedure can be improved.