Concrete Paving Association of Minnesota

CPAM Annual Workshop

March 11, 2016

Gordy Bruhn- Senior Engineering Specialist

FDR RemovalsI-94 Monticello, MN

FDR RemovalsTH 2 Erskine, MN

Revised Reinforcing Steel Sizing from metric back to standard numbering of 1/8th inch increments.

For example: #13 mm bar is now a #4 bar.

Type BE Repair

Allow either water or grout to bond the old and new concrete

Continue to require grout to seal outside perimeter of the partial depth repair

Increased Drill and Grout Dowel Bar Size, From 1-inch to 1.25-inch Dowel Bar Diam.

Low Volume Full Depth Repair will Remain 1’’ Diameter Dowel Bars

Full Depth Repair

12’ wide (typical)

1.25’’ Dowel requires a drill bit diameter of 1.375’’ (1 3/8’’ min.)

Start Dowels 1foot in from both ends

Increased Minimum Number of Dowel Bars as Roadway Width Wider Required

Need to add an additional dowel bar per side for each 1’ increase in

lane width

Roadway Lane Width

Dowel Bars Required

12 feet 11 Dowels

13 feet 12 Dowels

14 feet 13 Dowels

Dowel Bars Supplied in Dowel Bar Assemblies will Remain 1-inch Diameter Dowel Bars

Projects with both Paving & CPR will separately tabulate dowel bars.

Will include 2301 and 2302 Dowel Bar Pay Items

Transverse No.4 epoxy coated rebar length =Repair Width minus 2 feet

Concrete Mixes previously designed by MnDOT – now Contractor/Producer designed

New mix numbers for all concrete mixes

Concrete Grade

OLDMix

Number

NEWMix

Number

Intended Use

Maximum w/c ratio

Maximum Cementitio

usContent(lbs/cy)

Maximum%SCM

(Fly Ash/ Slag/

Ternary)

SlumpRange

Minimum

Compressive

Strength, f’c

(28-day)

3137 Spec.

R

Pavement

Rehab

3A32

3B423R52

CPR - Full

depth

concrete

repairs,

concrete

base

0.45 750 30/35/40 2 - 5” 4000 psi 2.D.3

Opened at a minimum of 48 hours of age and strength of 3000 psi◦ HE concrete requires approval of the Engineer prior to

incorporation into the work

◦ HE concrete requires control cylinders

Table 2461-7

High-Early (HE) Concrete Requirements (Not applicable to Mass Concrete)

OLD

Mix

Number

NEW

Mix

Number

Concrete

Grades

Allowed

Minimum

Time to

Opening

Maximu

m w/c

ratio

Maximum

Cementitio

us

Content

(lbs/yd3) *

Slump

Range

Minimum

Strength

to

Opening

Minimum

28-day

Compress

ive

Strength,

f’c

3137

Spec.

3A22HE 3HE32 F 48 hrs 0.42 7501 – 3”

║3000 psi 4500 psi 2.D.1

3A32HE

3Y43HE3HE52 B, F, G 48 hrs 0.42 750 2 – 5” 3000 psi 4500 psi 2.D.1

3Y33HE

3Y46HE

3Y37HE

3YHE52

Y

(Repairs

Only)

48 hrs 0.42 750 2 – 5” 3000 psi 4000 psi 2.D.2

3A32HE 3RHE52

R

(Repairs

Only)

48 hrs 0.42 750 2 – 5” 3000 psi 4000 psi 2.D.3

* Supplementary Cementitious Materials allowed.

║ Adjust slump in accordance with 2461.3.G.7.a for slipform concrete placement.

Standard Mixes UNCHANGED FROM PAST PRACTICES…Store in same condition as structure

Allowed to cure HE control cylinders in temperature monitored coolers

Both the structure and storage/curing vessel need to be temperature monitored

Must maintain temperature within storage / curing

vessel at ≤ 5ºF of the poured concrete structure

The Contractor may choose to make additional control cylinders (beyond MnDOT’s3) to determine strength at any time other than 28-days.

The Contractor may request the use of concrete maturity to determine opening to traffic, removal of forms, or loading.

MnDOT uses as part of acceptance

Based on an average of 3 cylinders

Cured under controlled conditions

MnDOT Defined Curing Periods

Moist Curing Environment Provided,

By Contract

Use of ventilation,

Use of ice,

Use of thermostatically controlled heating or cooling devices, or

Use heating methods such as stoves or light bulbs.

Other suitable methods are allowed provided the requirements limiting specimen storage temperature and moisture loss requirements are met.

Initial Cure up to 48 hours

The Contract requires providing moist curing environments of adequate size and number for initial and intermediate curing

(first 7 days) of concrete cylinders

Part of Field Office Spec (2031.3.C)

If no Field Office, still required

by Standard Specification (2461)

2016 Spec Book Requirement◦ Walks(2521) and Curb and Gutter (2531)

Concrete Contractor or Subcontractor required to have the following:◦ 2 - ACI Certified Flatwork Finisher or

Technicians

◦ 1 required to be on site at all times

Questions?

Concrete Paving Association of Minnesota

CPAM Annual Workshop

March 11, 2016

Maria Masten, Concrete Engineer

Concrete Paving UpdatesSpecification 2301

MnDOT has allowed two methods to achieve texture in concrete

◦Astroturf Drag

◦ Broom Drag

Beyond those requirements, we do not specify how to achieve the required texture.

Broom Drag (Combined Texture and Cure Cart)

Broom Drag (Separate Texture Cart)

In 2015, lateral wandering with certain types of vehicles felt on some roadways

Seems attributed to some broom texturing options

Met with Industry to discuss options

Beginning November 2015◦ Astroturf drag only for mainline paving

◦ Broom drag allowed for lower speeds, edge of pavements and hand placed concrete

Looking for volunteer project to install some different broom drag test sections in 2016

Used for locating dowel baskets and centerline tie bars

Original use ~ concrete pavement thickness◦ Five (5) pilot projects using the MIT-SCAN T2 to

determine the thickness of the concrete were conducted in 2015.

Evaluated the concrete thickness with the following:

(1) Contractor Probing (1 per 1,000 lineal ft)

(2) Probe Verification Scan (1 per 4 probes)

(3) Quality Acceptance Core (1 per 4,000 lineal ft)

What we learned??

Probe vs. Scan Location ◦ Correlation was acceptable but not great

◦ Variation was likely caused by the probe measurements which are typically measured to the nearest 1/8 to 1/4 inch depending on the Contractor.

Core vs. Scan Location◦ Difference was typically a few hundredths of an

inch.

What we are going to do different.

Not require the Contractor to probe at specified locations…they can probe at their discretion

Instead, the Contractor will scan the concrete at the former probe locations (1 per 1,000 lineal ft)

Required to core some of the scan locations for verification and a better comparison

Reduce overall coring◦ Scan Verification Core (1 per 8 scans)

◦ Quality Acceptance Core (1 per 8,000 lineal ft)

The MIT-SCAN T2 is currently being used to determine thickness by several state DOT’s and is accepted by the FHWA.

MnDOT’s goal is for full implementation in 2017 or 2018.

In 2015, MnDOT reviewed approximately 10 projects with unsealed joint test sections installed between 1994 – 1999

Cored 5 projects

In all cases where the seal was breached, the face of concrete cores looked worse than unsealed

Well sealed joints looked the best

Seal the following:◦ All Roadways: Speed limit 45 mph or less

◦ Whitetopping < 6” thick

◦ CPR projects: Speed limit 45 mph or less

◦ Bridge Approach Panels

MnDOT Standard Plans updated to reflect unsealed joint recommendations

Questions?