Influence of Inter-Particle Distances on the Rheological Properties of Cementitious Suspensions

Area of Science:

• Materials Science
• Civil Engineering
• Rheology

Background:

• Supplementary cementitious materials (SCMs), including fly ash (FA), blast furnace slag (BS), and silica fume (SF), are utilized as partial replacements for Portland cement (PC).
• While SCMs can enhance strength, their effective use hinges on the flow properties of fresh cementitious mixtures.
• Understanding the rheological behavior of these materials is crucial for optimizing concrete performance and application.

Purpose of the Study:

• To evaluate the rheological performance of cementitious suspensions incorporating PC, FA, BS, and SF.
• To investigate the influence of varying water-to-solid (W/S) volume ratios on rheological properties.
• To establish the relationship between inter-particle distances and the rheological characteristics of these suspensions.

Main Methods:

• Rheological tests were conducted on cement paste samples with W/S ratios ranging from 1.25 to 2.50.
• Measurements of yield stress and plastic viscosity were performed for suspensions of PC, FA, BS, and SF.
• Inter-particle distances were calculated and correlated with observed rheological properties.

Main Results:

• Yield stress and plastic viscosity decreased with increasing W/S ratio for all tested materials (PC, FA, BS, SF).
• Inter-particle distances varied significantly: PC (5.74–14.67 µm), FA (5.18–11.66 µm), BS (3.82–9.34 µm), and SF (0.107–0.27 µm).
• Rheological properties demonstrated higher sensitivity to finer particles due to their larger surface area.

Conclusions:

• The W/S ratio is a critical factor controlling the rheology of cementitious suspensions containing SCMs.
• Particle size and surface area significantly influence rheological sensitivity, with finer SCMs exhibiting greater impact.
• This research provides insights into optimizing the mix design of SCM-based concrete for desired flowability and performance.