Humboldt H-4140 GeoGauge User Manual
Page 22
22
The level of material compliance with the specification and small variability in
the quality of compaction was unprecedented in the experience of MnDOT
District 2. The real-time nature of the stiffness QC tests forced the continuous
attention of the contractor to compaction quality as was evident by the section-
by-section adjustments in roller patterns and watering. This real-time attention
to quality also resulted in a significant reduction in the contractor time and effort
traditionally needed to accomplish this kind of job.
The material strength achieved and its uniformity, as evident from the stiffness
tests, was consistent with supporting a 20-year roadway life. According to FHWA
guidelines, A coefficient of variation (COV) of less than or equal to 20% in
subgrade strength will support a 20-year life. The COV achieved for TH200 was
less than 14%.
District 2 found that the material and construction uniformity enabled by this
test method was sufficient to require stiffness testing intervals of no smaller than
every 500 ft.
Since the completion of the TH200 job, the stiffness measurements made as
part of the test method has been shown to have a strong relationship to resilient
modulus and so are useable as an in-place index
1
.
District 2, Thief River Falls Construction Office, of the Minnesota Department
of Transportation has deemed the success of this first use of stiffness based
compaction QC testing sufficient to warrant continuing and broadening use of it
on subgrades and bases in the 2005 and 2006 construction seasons.
For more information contact:
Melvin Main, Humboldt Mfg. Co.
717-650-6537,
[email protected]
or
J. T. Anderson
Resident Engineer,
MnDOT District 2
216-681-0927
1 Development Of Resilient Modulus Prediction
Models For Base And Subgrade Pavement Layers
From In Situ Devices Test Results, 2004, Ravindra
Gudishala, Louisiana State University, Baton Rouge,
LA 70808