Estimation of Lubrication Layer Thickness and Composition through Reverse Engineering of Interface Rheometry Tests

Area of Science:

• Civil Engineering
• Materials Science
• Rheology

Background:

• A lubrication layer forms near the pipe wall during concrete pumping, crucial for predicting pumping pressures.
• The exact composition and thickness of this layer (paste, micromortar, or mortar) remain debated in existing literature.
• Understanding this layer is key to optimizing concrete pumping efficiency and preventing blockages.

Purpose of the Study:

• To determine the composition and thickness of the concrete lubrication layer using interface rheometry.
• To resolve the ongoing debate regarding whether the layer is cement paste, micromortar, or mortar.
• To provide a more accurate model for predicting concrete pumping performance.

Main Methods:

• Interface rheometry tests were conducted to analyze the rheological properties of the lubrication layer.
• Rheological properties of cement paste, mortars with varying maximum particle sizes, and concrete were measured.
• Mathematical modeling was employed to assess the layer's composition based on rheological data.

Main Results:

• Mathematically, a single homogeneous layer of paste or mortar can explain the lubrication layer's formation.
• Physically, particle migration indicates the layer must contain sand particles, proportional to particle size squared.
• The lubrication layer is likely composed of mortar with a maximum particle size between 1 and 2 mm.

Conclusions:

• The concrete lubrication layer is best described as a mortar with a specific maximum particle size.
• Interface rheometry provides a viable method for characterizing this layer's composition.
• Findings contribute to a better understanding of concrete rheology during pumping operations.