Non-uniformity in the mat, either gradation segregation, where coarse stone separates from the fines and binder, or thermal segregation, where cold lumps of mix sit next to hot material. It shows as open, rocky patches in a pattern: at the end of each truckload, in a center streak, or along the edges. Segregated areas cannot reach density and ravel early, so crews fight it with proper silo loading, steady augers, MTVs and restraint with the hopper wings.
Truck-end segregation every load, coarse spots right where the tailgate opens, have the plant drop the load in three piles.
Coarse patches at the same spacing as the truckloads mean the problem started at the silo or in the truck, not at the screed.
Also heard as
- seg
- truck-end segregation
- thermal segregation
Related terms
Center streak
A narrow strip of coarse, open mix running down the middle of the mat behind the paver's auger gearbox.
Wings
The folding side walls of a paver hopper, and the habit of folding them to dump leftover mix onto the conveyors.
MTV
Material transfer vehicle: a machine between the trucks and the paver that remixes hot mix and feeds it nonstop.
Raveling
Loss of aggregate from the pavement surface as the binder lets go of the stone.
Live bottom
A haul trailer with a conveyor floor that unloads mix out the back without raising the bed.