Date of Award

Fall 12-15-2017

Level of Access Assigned by Author

Campus-Only Thesis

Language

English

Degree Name

Master of Science (MS)

Department

Civil Engineering

Advisor

Eric Landis

Second Committee Member

Roberto Lopez-Anido

Third Committee Member

Warda Ashraf

Abstract

In this work, the rheological properties of cement paste modified with cellulose nanofibrils (CNFs) where investigated. CNFs have the potential to modify concrete properties in beneficial ways, such as an internal curing agent, as well as a microscale reinforcement. However, an addition of CNFs has the potential to adversely affect workability. The goal of the work described in this thesis was to quantify rheological properties of cement paste of varying water-cement ratios and CNF contents. Two tools were used in this analysis: a standard flow table, and a conventional rotary mixer. The torque required to move the fresh paste at different mixer speeds was used to develop a stress strain rate relationship. Based on the measured torque versus rotation speed, this data was used to fitted to a Herschel-Bulkley (HB) rheological model to establish the yield stress and shear thickening properties of the pastes. The measurement showed that. The effect of the addition CNF to the cement paste through the suspension of yield stress and viscosity parameters, addition CNF lead to increase in yield stress led to increasing shear strain rate, which in turn the reduction affects the workability of the mixture, and therefore a decrease in the properties of the rheological flow, the mixtures have shear thickening behavior depending on flow index n, the shear thickening property resulting from increased viscosity properties of the cement paste.



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