Digital rheology of fresh-state concrete

Utilising lower-carbon constituents, optimising mix designs, and minimising waste can greatly decrease the carbon emissions associated with concrete use. Inadequate characterisation of fresh-state concrete complicates distinguishing between mixes and identifying performance issues before remedial actions are necessary. This hinders effective quality control, decarbonisation efforts, and contributes to poor productivity in the construction sector. Rheological measurements can improve fresh-state concrete characterisation; however, concrete rheometers are too costly and complex for construction site use, so simple single-point characterisation through field tests, such as slump testing, remains commonplace. This thesis combines theoretical and experimental approaches to bridge this characterisation gap and contribute a novel digital fresh-state characterisation approach. This framework utilises 3D visual and accelerometer tools to augment existing field tests with rheological measurements and quantitative multi-phasic insights. The first part of this thesis contributes a fundamental understanding of fresh-state concrete flow phenomena. The flow regimes observed during field testing are categorised using 3D reconstruction of the deposit morphology. This categorisation enables the robust application of various expressions for rheological measurement tailored for the encountered flow regime. Dimensional analysis and energy methods indicate that 3D geometrical and temporal measurements are essential to fully capture field test-rheology relationships. Relationships linking deposit height and diameter measurements to yield stress are established. Additionally, relationships between yield stress, flow cessation time, and viscosity are proposed. The second part ofthis thesis contributes novel digital methodologies for non-destructively determining the geometrical and temporal properties with minimal intrusion on current field testing procedures. Specifically, it produces a 3D geometrical measurement approach through digital reconstruction, which is utilised for yield stress measurement. Yield stress is measured using the 3D reconstruction of field testing deposits with an accuracy of approximately 10% compared to a torque vane rheometer. An accelerometer methodology is also proposed to extract flow cessation time measurements from field testing, delivering the parameters necessary for accurate viscosity measurement. Viscosity is measured using the accelerometer-measured flow time to within approximately 15% of the values obtained from a torque vane rheometer. Given that flow table and standard slump test results were found to be analogous for comparable mixes, the flow table dropping procedure offers limited value for rheological characterisation. Therefore, the final part of this thesis integrates the digital 3D recon struction and accelerometer methodologies into a new tool, and a unified testing method called the ‘Slump-Rheometer’, which uses a standard slump cone and a slump-flow test baseplate. Digitally derived rheological measurements are augmented with multi-phasic insights that account for discrete fluid behaviour, incorporating digital methodologies to quantify characteristics such as circularity, aggregate separation, and surface intensity. Two concrete mixes with distinctly different constituent materials are characterised as the same using current fresh-state testing procedures. Using the ‘Slump-Rheometer’, the two concretes are characterised differently according to their distinct viscosities, stability, and bleeding behaviours. Finally, early efforts are presented to propose a practical specification framework with optimal bounds for yield stress and viscosity values tailored for various construction applications. This thesis demonstrates that digital augmentation of current field testing methods is a practical and viable route to better characterising the behaviour of different concrete mixes. The ‘Slump-Rheometer’ offers accurate yield stress and viscosity measurement and quantitative multi-phasic insights. The current technology gap between advanced vane rheometers and field testing has been addressed by retaining current processes. The tool is designed for rapid adoption, enabling meaningful improvements in quality control processes and supporting the development of innovative concrete products to reduce carbon emissions.

Name dc:type.qualificationname

Doctor of Philosophy (PhD)

Level dc:type.qualificationlevel

Doctoral

Grantor dc:publisher.institution

University of Cambridge

Year dc:date.issued

2025

Author dc:creator

• White, Callum

Advisor dc:contributor.advisor

• Lees, Janet

• 3D reconstruction
• Bingham
• Concrete
• Rheology

Licence

• https://www.repository.cam.ac.uk/bitstreams/4a7281ae-5296-4bf1-949d-1d7eb6adf125/download
• http://purl.org/NET/rdflicense/allrightsreserved

Language dc:language

eng

Author Identifier

0000-0003-3706-3235

OAI identifier oai:identifier

oai:www.repository.cam.ac.uk:1810/390501