title: Flocculation and sedimentation in suspensions using ultrasonic wave reflection.
abstract: This work was undertaken to help understand and interpret the ultrasonic wave reflection response of Portland cement paste as it transforms from a fluid-like suspension to a solid in the first hours after mixing. A high impact polystyrene buffer (delay line) was used to measure small changes in the P- and S-wave reflection coefficients. Two materials were studied: a non-hydrating colloidal alumina suspension whose microstructure was manipulated between dispersed and flocculated states by adjusting the pH and a coarse silica suspension that readily sedimented. The S-wave reflection coefficient clearly distinguished between dispersed and flocculated states. Sedimentation of particles in dispersed suspensions was distinguished using the P-wave reflection coefficient. Based on these findings, the observed P- and S-wave responses from hydrating Portland cement paste are interpreted in terms of flocculation and sedimentation processes.
authors.affiliation: Radiological Materials and Technology Development Group, Pacific Northwest National Laboratory, Richland, Washington 99352, USA.
authors.forename: Chul-Woo
authors.initials: CW
authors.lastname: Chung
authors.forename: John S
authors.initials: JS
authors.lastname: Popovics
authors.forename: Leslie J
authors.initials: LJ
authors.lastname: Struble