It would be no exaggeration to state that aggregates have their greatest influence on the performance of plastic or fresh concrete. Aggregate properties such as shape, surface texture, and grading largely govern the way in which fresh concrete is proportioned, and determine how easily the concrete can be mixed, transported, placed, compacted, and given a suitable finish. Aggregates form the 'link' between the intent of the mix design (i.e. the proportioning of the mix constituents) and the fulfilment of that intent in the hardened state. For, no matter how sophisticated the mix formulation or the binders used, unless the plastic mix can be thoroughly compacted without segregation or excessive bleeding to produce a dense homogeneous material, the concrete will not perform successfully. Aggregates strongly influence the outcome of this process. An understanding of the role of aggregates in plastic concrete is therefore fundamental to the production of good concrete.