Topcon mmGPS 3D Paver, Reference Manual

Page: 170 / 288

Paving Principles
mmGPS 3D Paver Reference Manual
4-8
Figure 4-11. Head of Material Affects Mat
Reaction of Material Under Screed
(“R”)
Ideally, every truck load of material delivered to the paver would be
exactly like every other load, with no variation. However, as a
practical matter, changes in mix characteristics such as mix
temperature, density, gradation, A.C. Content, and segregation,
affects the internal stresses developed within the mix, which in turn
affects the resistance of the mix to flow under the screed (reaction of
material under screed, “R”). The key element to bear in mind is that
the screed passing over the paving material compacts the material to a
certain degree. Variables in the resistance of the material to
compactive forces causes changes in the screed’s angle of attack,
Head of
Material
Too High
Screed Rises
Due To
Increased
Resistance
Correct
Head of
Material
Correct Depth
of Mat
Maintained
Head of
Material
Too Low
Screed Settles
Due To
Decreased
Resistance
C
C
C
C
Indicates Centerline
of Auger