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Transcript of MnDOT Investigation of Full Depth Repairs - CPTech … Masten FDR.pdfMnDOT Investigation of Full...
MnDOT Investigation of Full Depth Repairs
2013 Fall National Concrete Consortium – Asheville, NCSeptember 25, 2013
Maria Masten, MnDOT Concrete Engineer
Acknowledgements• Gordy Bruhn, Concrete Rehab Specialist, MnDOT
Concrete Unit• Matt Zeller, Concrete Paving Association of Minnesota
• Construction Materials• CPR, Inc.• Diamond Surfaces, Inc.• Interstate Improvement• PCI Roads• Simplex Construction Supplies
• Steve Olson, MnDOT Concrete Research Unit• Kyle Hoegh, University of Minnesota
I-90 – Full Depth Repairs
SP 2280-126 - I-90
I-90 EB FWD Data
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
138.5 139 139.5 140 140.5 141 141.5 142 142.5 143 143.5 144 144.5 145
Average LTE 27%st dev 11%
minimum 5%maximum 83%
SP 2280-126 I-94 Alden6 dowel bars25.4% Trucks7,668 AADT
I-90 Investigation• Full Scale Investigation of other CPR projects
constructed between 2007 and 2012• Was the switch from 11 dowels to 6 (3 per WP)
or 8 (4 per WP) depending on traffic going too far? But it works for retrofit dowel projects…
• Where did the material go? We used more than we needed? Did it break down, was it durable?
• Is Spec constructible?• Place the bonding agent into the drilled holes
to completely fill the void.
Multiple Projects TestedRoad MP 2010
ADT2010
%TrucksDowels per lane
FWD LTE Range
CPRYear
I-90 138-145 7,668 25.4 6 5-83% 2009I-90 185-193 11,416 11 11 86-95% 2010I-94 157-194 43,500 10.3 6 25.7-46.4% 2009I-94 209-217 100,725 9.5 8 19-80% 2010
MN23 112-124 3,290 12.9 8 97-97.5% 2011MN77 1-5 65,000 2.2 11 31-95% 2007
• Visual examination of the cores• FWD Testing
• We have never done FWD testing on FDR until now…• What is a good LTE?• Does LTE tell us what we need to know?• Michigan DOT suggested looking at deflection….
I-94 (2 projects)
SP 2780-64 I-94 Maple Grove
8 dowel bars9.5% Trucks
100,725 AADT
SP 8680-155 I-94 Dist36 dowel bars9.5% Trucks
42,978 AADT
I-90 (Top) & TH 23 (Bottom)
SP 5080-155 I-90 Dist611 dowel bars
11% Trucks11,416 AADT
SP 1204-19 Hwy 23 Dist 86 dowel bars
424 Trucks/Day Prior to Repairs
Results of Investigation During investigations we found a lack of bonding
agent around the dowels from all of the Contractors
“I watched them install dowels on many projects and thought they were filled.”
Change standard back from 8 dowel bars to 11 dowel bars due to problems we have encountered with workmanship
Time to discuss with Concrete Industry and educate Inspection Personnel
Agency-Industry Meeting• December of 2012• Focused on premature failure of full depth repair
project• Investigation of other projects and information
sharing with Industry• “It has been working for 30 years – what’s
changed?”• Workmanship and Best Practices were the end
result• How good can we really do? Let’s go to MnROAD
and find out….
MnROAD – checking workmanship
MnROAD Results – Phase I• What did we try?
• Epoxy dip and stick, Epoxy double dip, Epoxy – fill and twist, grout box, 1 hour old grout, grout capsules, polygripepoxy
• Tested with MIRA to see if provide information non-destructively
• Best performers• Grout Anchoring Capsules• Polygrip epoxy
2013 Construction Season
Current Construction Practices• How much anchoring material do
we actually need?• What is good enough?
• Contractors concerned with subjectivity.
• Best coverage was determined by what application method / materials had the least amount of holidays in the annular space between the dowel bar and the drill hole.
2013 Construction Season• I-694 North of Minneapolis• Noticed existing Full Depth Repairs faulted (9 years old)• Original pavement placed – 1964 & 1985
2013 Construction Season• MnDOT randomly cored every
CPR project in 2013 • One Contractor took initiative
to core and check their own workmanship
• Most effective cause for Contractor to change was when MnDOT cored each project – even when Contractors were working on multiple projects
2013 – Acceptable Anchoring Methods Ambex Grout Anchoring Capsules Modified Grout Bag Method
Faster than the hole drilling crew now!!!
MnROAD Field Installation –Phase 2• No grout, grout bag, grout capsule, epoxy (2 types)• Controlled location• FWD testing seasonally• Coring• Monitoring over time• Laboratory Testing - Phase 3???
• Using what was learned in NCHRP 10-69• Considering using a Shear Test to determine how strong
the anchoring material is and how it will perform over time
Prescriptive or performance with anchoring procedures?
• Dowel Bar Anchoring Test Section• Complete FDR at least one (1) day prior to startup • Install 11 dowels in accordance with appropriate FDR• Cure the dowel bar anchoring adhesive at least 4 hours before coring. • DO NOT PLACE CONCRETE IN THE DOWEL BAR TEST SECTION.• Take (3) – 6” full depth cores centered on the dowel and 1 1/2" from the
sawed vertical face.
• Dowel Bar Anchoring Assurance Coring• At the Engineer’s discretion, the Contractor will take additional cores to
confirm consistent dowel bar anchoring. • For each 1500 Lineal Feet of FDR,the Engineer will randomly choose 2
separate repairs and mark 2 dowel bars for assurance coring.
Additional Data Analysis• Look at deflection data from FWD testing• Look at Pavement Management Data
• Break down performance of projects utilizing full depth repair techniques
• Consider base support and type
• In my opinion …• “Full Depth Repairs are an excellent technique for
concrete pavement preservation – just remember it is sometimes the simple things that can cause the biggest problems.”
Thank you!