Stress-induced compaction of concentrated dispersions of gel particles

When submitted to successive shear stress steps, the elastic shear modulus of a concentrated dispersion of soft gel particles shows an exponential increase from 50 to 110 Pa. A slow relaxation time ( tau(r) similar or equal to 500 s) attributed to the mobility of the gel particles within their free volume is obtained. The amplitude of the relaxation time distribution decreases with the number of shear stress sequences, indicating a progressive decrease in the free volume available per particle. The results are explained by an increase in the packing density as grains rearrange under the external constraint. A rate constant is determined from the evolution of the dispersion's elastic modulus (K similar or equal to 4 x 10(-4) s(-1)). The rate of compaction shows a logarithmic decrease when the initial particle's packing fraction is increased.