This paper studies the short and long-range structure of silica aggregates using the small angle light scattering technique. Silica particles were made to aggregate by the addition of MgCl2, with and without continuous shear. Two different short-range structures were observed for different aggregation conditions. The small angle light scattering reveals two different floc structures at different length scales, a very compact floc at short length scale and a loose floc at large length scale. The sediments of these flocs were studied by allowing them to settle under gravity and consolidate at different centrifugal forces. The results show that the floc short-range structure is important in governing the compaction behaviour of sediment.