Tools to Improve PCC Smoothness During Construction (R06E)

Date: January 19, 2016Gary Fick

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Real-Time Smoothness

What is it?An integrated system

of profile data

collection sensors and

processing software

that provides real-time

profile feedback to the

contractor.

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Real-Time SmoothnessSHRP2 Implementation Support

RTS Implementation Support ActivitiesObjective: Routine use of RTS technology by agencies and contractors who routinely construct PCC pavement.

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Real-Time SmoothnessSHRP2 Implementation Support

RTS Implementation Support ActivitiesTask 1: Equipment Loan Program (2015 and 2016)

Full use of an RTS system for two weeks On-site technical support and training Budget allows for eleven equipment loans Projects with a minimum of 10 consecutive mainline paving days

(more is preferable) Contractor or agency should commit to providing daily QA

profiles during the equipment loan Contact gfick@trinity-cms.com if interested

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Real-Time SmoothnessSHRP2 Implementation Support

RTS Implementation Support ActivitiesTask 2: Regional Showcase (Open House)

One day classroom presentations with an on-site RTS demonstration

In conjunction with an equipment loan project Travel expenses are covered for up to 10 agency participants

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Real-Time SmoothnessSHRP2 Implementation Support

RTS Implementation Support ActivitiesTask 3: Workshops

Four hour workshops – contact gfick@trinity-cms.com Tentative agenda

1. Importance of Pavement Smoothness2. Fundamentals of Pavement Smoothness Measurement3. RTS Measurement Technology and Practices4. Fundamentals of Ride Quality and Pavement Profile

Analysis5. Current Practices for Concrete Pavement IRI

Specifications6. Best Practices for Concrete Paving Operations7. Using RTS Technology to Improve Concrete Pavement

Smoothness

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Real-Time SmoothnessSHRP2 Implementation Support

RTS Implementation Support ActivitiesTask 4: Documentation of Results/Case Studies

Synthesis of contractors’ experience Case study – Comparing real-time measurements to QA results Case study – Long-term performance of RTS Documentation of equipment loans and lessons learned

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Real-Time SmoothnessSHRP2 Implementation Support

RTS Implementation Support ActivitiesTask 5: Specification Refinement

QC approach Process improvement

Task 6: Outreach Materials Quick field reference guide (pocket reference) Brochures Project updates (30 minute briefings)

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Reasons for Using RTS Equipment

• Reduce disincentives• Increase incentives• Anticipated change in smoothness

acceptance requirements• PI to IRI• Change in localized roughness specification limits

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Real-Time Smoothness

Benefits of identifying construction artifacts in real-timeOpportunity to correct objectionable profile features caused by:

Stringline disturbance Padline variability Non-uniformity of concrete …

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Real-Time Smoothness

Benefits of identifying the impact of process changes in real-timeValidation of adjustments in 1 hour vs. 12 to 24 hours:

Hydraulic sensitivity relative to machine control input (stringline and stringless)

Vibrator frequencies Paving speed Concrete head Concrete mixture proportions …

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RTS Systems – Which One is Best?

• They both do the same thing - the correct question is, “which one is best for me?”

• Factors to consider: Ease of mounting and switching between multiple pavers Field ruggedness Familiarity with Ames lightweight profiler systems Laser vs. ultrasonic sensors

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RTS Mounting Locations

• Typically center of each driving lane• Adjust this for special situations, when

tuning the paver: Tie bar insertion issues One side of the paver is consistently rougher Cross-slope changes

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RTS Mounting Locations

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RTS Systems:Daily Setup and Shutdown

• Start-up - approximately 5 minutes Install sensors and DMI Connect cables Input starting station and direction Start the system

• Shut-down – approximately 5 minutes Stop the system Download data to a USB drive Disconnect cables Remove sensors and DMI

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RTS Systems:Daily Setup and Shutdown

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Ten Commandments of Concrete Pavement Smoothness (circa 1988)

Source: ACPA Best Practices for Constructing Smooth Concrete Pavements

Credit: Chapin Cipherd, CMI Corp.

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21st Century Approach

The “Sweet Spot”

Mixture Factors

Paving Factors

Human Factors

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Mixture Factors

• Combined gradation• Between batch uniformity• Uniform delivery of concrete

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Combined Gradation

Remember the purpose of an optimized gradation:• Economically combining aggregate particles to achieve the desired

objectives of: Reduced paste content Improved workability Durability

• An optimized mixture must be workable in the field to achieve

durability

• The Tarantula curve was developed concurrently with a lab test that

evaluates a concrete mixture’s response to vibration

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Between Batch Uniformity

Consistent combined gradation and water content• Scales in tolerance• Uniform stockpile moistures • Eliminate stockpile segregation

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Uniform Delivery of Concrete

Translates to minimizing paver stops• Plant production capacity must be able to

feed the paver

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Paving Factors

• Track line• Stringline/Stringless model• Paver setup

Draft/Lead Sensitivities Vibrator frequency Vibrator height Float pan

• Concrete head• Curing and texturing

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Human Factors

• Training• Experience• Communication• Empowerment

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Using RTS Systems

• Step 1 – Establish a baseline• Monitor results for 1 to 2 days• Keep processes static, but make ordinary adjustments Observe typical responses to the ordinary adjustments

• Mixture• Vibrators• Speed• Head• Stops• Etc.

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Using RTS Systems

• The RTS results are higher than the QC hardened profiles – what’s up with that?

• Don’t panic• Just focus on making the RTS results better (lower IRI)• QC profiles will improve as well

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Using RTS Systems

• Step 2 – Pick the low hanging fruit• Eliminate large events that cause excessive

localized roughness• Stringline/stringless interference• Paver stops• Padline issues• Etc.

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Localized Roughness Events

• Stringless system interference

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Localized Roughness Events

• Running the paver out of concrete

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Localized Roughness Events

• Stopping the paver

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Using RTS Systems

• Step 3 – Adjust the paving process to improve overall smoothness

• Maintain a consistent head• Lead/draft - setup the paver as flat as possible• Sensitivities• Vibrators (height and frequency)• Mixture• Paver operation• Paving speed

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Overall Smoothness

• Eliminating big events gave us a new “baseline” to adjust from

• Systematically make changes in small increments

• Get a minimum of 0.1 mile with consistent paving (no big events) and then evaluate if the adjustment made things smoother

• Continue adjusting in small increments and evaluating every 0.1 mile

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Overall Smoothness

• Stay focused and incredible things can happen

• Over a mile per day – average IRI = 28 in/mi

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Using RTS Systems

• Step 4 – Identify repeating features using a PSD plot and adjust processes when possible

• Joints• CRCP bar supports• Dumping/Spreading loads

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Real-Time SmoothnessSHRP2 Implementation Support

Questions and Discussion