![]() Hand-placing should be minimized because it is prone to aggregate segregation and results in a slightly rough surface texture. This can often occur around utilities, around intersection corners and in other tight spaces. HMA can be placed by hand in situations where the paver cannot place it adequately. Improperly constructed longitudinal joints can cause premature deterioration of multilane HMA pavements in the form of cracking and raveling. The interface between two adjacent and parallel HMA mats. ![]() Overly thick final lifts have a tendency to shove or displace during compaction making it difficult to achieve a smooth finish. In order to avoid mat tearing (which generally shows up as a series of longitudinal streaks) a good rule-of-thumb is that the depth of the compacted lift should be at least twice the maximum aggregate size and three times the nominal maximum aggregate size (TRB, 2000 ). A “ lift” refers to a layer of pavement as placed by the asphalt paver. ![]() This subsection presents a few of the basic considerations that apply in virtually all situations: Many are dependent upon local materials, weather, crew knowledge and training, and individual experience. There are, of course, many considerations to take into account when placing HMA. The asphalt paver is the principal machine involved in mix laydown and is assisted by the material transfer vehicle ( MTV) in some instances. Mix laydown involves everything used to place the delivered HMA on the desired surface at the desired thickness.
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