volume fraction F is low, aggregates settle individually and At low volume fractions, calcium carbonate colloidal suspendeposit onto the sediment; at higher volume fractions, a sions undergo cluster deposition: aggregates grow in the suspenclose packing of aggregates forms rapidly, filling the whole sion, settle individually when their size becomes large enough, container, and collapses under its own weight.
and deposit at the bottom of the container, forming a voluminous
In the present paper, we investigate very dilute suspensediment. We have measured the settling velocity of individual sions of calcium carbonate particles dispersed in water (F aggregates as a function of their radius. We show that the clusters is as low as 10 04 ). The surface charge of the particles is are self-similar with a fractal dimension, D Γ
2.2 { 0.1, which is negligible and the van der Waals attraction dominates. Under significantly larger than that in diffusion-limited aggregation, and such circumstances, diffusion-limited cluster aggregation is that they do not grow above a limiting radius, R max Γ 0.5 mm. These results are discussed in relation with the mechanical proper-expected. Experimentally, we observe the formation of agties of colloidal fractal aggregates.