Implementing Bituminous
Underseals to Reduce
Reflective Cracking
Tim Clyne, MnDOT
MAAPT 63rd Annual Asphalt Conference
December 7, 2016
What’s the Problem?
Cracking Mechanism
https://www.researchgate.net/figure/277890592_fig1_Figure-21-Reflective-cracking-mechanism-5
What is an Underseal?
Seal Coat prior to bituminous overlay
Impervious membrane to stop moisture intrusion
Acts as super tack coat
Delays / reduces Reflective Cracking
“Texas Underseal”
Stress Absorbing Membrane Interlayer (SAMI)
Underseal Sequence
https://www.dot.nd.gov/conferences/construction/presentations/2016/Texas%20Underseal-Wollmuth.pdf
Spec. 2356
TH 101 Chanhassen
SP 2736-44
Paved in 2010
3” Mill
Underseal vs. Control
3” Overlay (SPWEB340E)
In 2 lifts
TH 101 Chanhassen
TH 101 – Before
TH 101 – After (Underseal)
TH 101 – After (Control)
TH 5 West of Waconia
SP 1002-102
Paved in 2014
2” Mill
Underseal
3.5” Overlay (SPWEA340C)
In 2 lifts
TH 5 West of Waconia
TH 5 – Before
TH 5 - After
TH 61 & 10 Hastings
SP 8205-137
Paved in 2016
2” Mill
Underseal
2” Overlay (SPWEB440F)
TH 61 – Before
Super-Duper Underseal
TH 100 Edina
SP 2733-89
Paved in 2015 & 2016
Mill & Patch Concrete
UTBWC
~3” Overlay (SPWEB440F)
In 2 lifts
TH 100 – Before
TH 100 – After
TH 280 St. Paul
SP 6241-102
Paved in 2016
Mill 4” Bituminous
UTBWC
3.25” Overlay (SPWEA440F)
In 2 lifts
TH 280 – Before
TH 280 – After
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
5 101 61 10 100 280
Rid
e Q
ua
lity
In
de
x
Highway
Pre-Overlay 2016
Ride Quality Comparison
Summary
Not sure why, but it works!
Reduced / delayed reflective cracking
Improved ride quality
Will continue in the future