How clay particulates affect flow cessation and the coiling stability of yield stress-matched cementing suspensions

Iman Mehdipour; Hakan Atahan; Narayanan Neithalath; Mathieu Bauchy; Edward Garboczi; Gaurav Sant

doi:10.1039/c9sm02414j

How clay particulates affect flow cessation and the coiling stability of yield stress-matched cementing suspensions

Soft Matter. 2020 Apr 29;16(16):3929-3940. doi: 10.1039/c9sm02414j.

Authors

Iman Mehdipour¹, Hakan Atahan², Narayanan Neithalath³, Mathieu Bauchy⁴, Edward Garboczi⁵, Gaurav Sant⁶

Affiliations

¹ Laboratory for the Chemistry of Construction Materials (LC2), Department of Civil and Environmental Engineering, University of California, Los Angeles, CA 90095, USA. gsant@ucla.edu.
² Laboratory for the Chemistry of Construction Materials (LC2), Department of Civil and Environmental Engineering, University of California, Los Angeles, CA 90095, USA. gsant@ucla.edu and Department of Civil Engineering, Istanbul Technical University, Istanbul, Turkey.
³ School of Sustainable Engineering and the Built Environment, Arizona State University, Tempe, AZ, USA.
⁴ Laboratory for the Physics of Amorphous and Inorganic Solids (PARISlab), Department of Civil and Environmental Engineering, University of California, Los Angeles, CA 90095, USA and Institute for Carbon Management (ICM), University of California, Los Angeles, CA 90095, USA.
⁵ Applied Chemicals and Materials Division, Material Measurement Laboratory, National Institute of Standards and Technology, Boulder, CO 80305, USA.
⁶ Laboratory for the Chemistry of Construction Materials (LC2), Department of Civil and Environmental Engineering, University of California, Los Angeles, CA 90095, USA. gsant@ucla.edu and Institute for Carbon Management (ICM), University of California, Los Angeles, CA 90095, USA and Department of Materials Science and Engineering, University of California, Los Angeles, CA 90095, USA and California Nanosystems Institute (CNSI), University of California, Los Angeles, CA 90095, USA.

PMID: 32240280
DOI: 10.1039/c9sm02414j

Abstract

The remarkable increase in the flow resistance of dense suspensions can hinder 3D-printing processes on account of flow cessation in the extruder, and filament fragility/rupture following deposition. Understanding the nature of rheological changes that occur is critical to manipulate flow conditions or to dose flow modifiers for 3D-printing. Therefore, this paper elucidates the influences of clay particulates on controlling flow cessation and the shape stability of dense cementing suspensions that typically feature poor printability. A rope coiling method was implemented with varying stand-off distances to probe the buckling stability and tendency to fracture of dense suspensions that undergo stretching and bending during deposition. The contributions of flocculation and short-term percolation due to the kinetics of structure formation to deformation rate were deconvoluted using a stepped isostress method. It is shown that the shear stress indicates a divergence with a power-law scaling when the particle volume fraction approaches the jamming limit; φ → φj ≈ φmax. Such a power-law divergence of the shear stress decreases by a factor of 10 with increasing clay dosage. Such behavior in clay-containing suspensions arises from a decrease in the relative packing fraction (φ/φmax) and the formation of fractally-architected aggregates with stronger interparticle interactions, whose uniform arrangement controls flow cessation in the extruder and suspension homogeneity, thereby imparting greater buckling stability. The outcomes offer new insights for assessing/improving the extrudability and printability behavior during slurry-based 3D-printing process.