Lift
Lift turns up in 3 fields: concrete, asphalt, geosynthetics. Here is what it means to the people in each one.
Lift in concrete
One layer of concrete placed in a wall, column or mass pour, or the height cast between horizontal joints.
Walls and deep members are filled in horizontal layers, often 12 to 24 in deep, with each lift vibrated into the one below while it is still plastic. In a second sense the lift is the full height cast in one placement between horizontal construction joints, such as a 12 ft wall lift. Lift depth and pour rate together set the pressure on the forms, which is why form designers specify both.
"Bring it up in two-foot lifts all the way around before you go back, or you'll blow those ties at the corner."
Lift in asphalt
One layer of mix placed and compacted in a single pass of the paver.
A single layer of pavement laid at one time, described by its compacted thickness. Lift thickness has to suit the aggregate size: a common guideline is at least three times the NMAS for fine-graded mixes and four times for coarse-graded mixes, so the stones can reorient under the rollers. Thicker lifts hold heat longer and compact more easily, while thin lifts on cold days lose heat fast.
"Six inches of base goes down in two lifts, three and three, then a two-inch surface lift on top."
Lift in geosynthetics
One layer of fill placed and compacted at a time, the unit by which walls, slopes and embankments are built.
In reinforced soil, lifts are usually 150 to 300 mm thick after compaction, and geogrid layers sit at set lift intervals up the wall. Over geosynthetics on soft ground, the first lift must be thick enough that equipment does not cut or rut the layer below. Thickness, moisture and compaction are logged for every lift.
"First lift over the grid is 12 inches minimum, and no tracked equipment on it until it's spread."