Update on New Era Testing

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John Cunningham, Xuhao Wang, Peter Taylor

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The Latest Technologies All in One

CP Tech Center

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Who Needs More Testing?

• Performance Engineered Concrete

Pavement Mixtures (AASHTO PP84)

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Why Bother?

• Current approaches

May not measure critical parameters

Are often built around previous failures –

thereby introducing unintended consequences

Limit innovation

• Need to deliver mixtures that meet

needs, reliably

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A Better Specification

• For measuring the things that matter

Transport properties (everywhere)

Aggregate stability (everywhere)

Strength (everywhere)

Cold weather resistance (cold regions)

Shrinkage (dry regions)

Workability (everywhere)

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What Next?

• Understanding and education

What and why

• Validate tests in the field

Reliability

Efficiency

• New tests

Transport (Resistance to Fluids)

• Resistivity Then calculate formation factor based on

Moisture

Temperature

Geometry

Curing conditions

Ionic concentration of the pore solution

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Transport (Resistance to Fluids)

• Drop Test Assess the quality of paste in an exposed surface at

a local scale of less than 0.5 in2

20µL

Measure time to loose sheen

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Transport (Resistance to Fluids)

• Drop Test Calibration (56 days)

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Transport (Resistance to Fluids)

• Drop Test Example results

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Aggregate Stability

• AAR Follow PP65

• D-Cracking Follow local practice (i.e., IPA in Iowa)

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Strength

• Compressive or flexural

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Cold Weather Resistance

• Freeze Thaw (air void system) Super air meter (SAM) – AASHTO TP118

Pump to 3 pressures in 2 cycles

Dial reports a “SAM number”

Ley 2016

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Cold Weather Resistance

• Freeze Thaw (time to saturation) Absorption of water – ASTM C1585

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Cold Weather Resistance

• Resistance to salts Expansive calcium oxychloride formation

From MgCl2 and CaCl2

Measure with – low temperature differential scanning

calorimetry (LT-DSC)

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Cold Weather Resistance

• LT-DSC (AASHTO T365) results

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Cold Weather Resistance

• Paste expansion test (ISU) – assess the ability

to resist oxychloride formation

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Shrinkage

• Cracking risk

• Warping

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Shrinkage

• Ring test - ASTM C1581

Assesses cracking risk

Starts immediately

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Shrinkage

• Dual ring test

Measure both expansion and contraction

Force a temperature gradient in the concrete

Weiss

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Workability

• Owner should not really care, but

Too wet = edge slump

Too dry = poor consolidation & air loss

Good indicator of uniformity and consistency

Need a measure of

the response to vibration

Workability

• Kelly ball test Developed in the 1950s in US

Standardized in California DOT test

Comparable to slump test

1.1 to 2.0 times the Kelly ball reading

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Workability

• Vibrating Kelly Ball Test – AASHTO TP129 Measure initial slump (initial penetration)

Start vibrator for 36 seconds at 8000 vpm

Record depth every 6 seconds

Repeat

Plot on root time

Calculate slope = VKelly Index

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Workability

• VKelly Index

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Workability

• Effect of the aggregate system …

• Box Test

• A simple test that examines: Response to vibration

Filling ability of the grout (avoid internal voids)

Ability of the

concrete to hold

an edge

Workability

12”

12”

12”

Ley

Workability

• The edges of the box are then removed and

inspected for honey combing and edge slump

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QC

• QC reassures contractor that the mix will get

there

Unit weight

Calorimetry

Maturity

Strength development

Air void stability

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QC

• Calorimetry

Tells us about the chemistry of the system

(uniformity and compatibility)

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QC

• Maturity

Sensors in the pavement determine in-place

maturity and thereby strength for opening

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QC

• Foam drainage

Air void systems can change with

working/pumping

Depends on system chemistry

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What Else?

• Intelligent Compaction

• What about the ride?

• When should I saw?

• Finding the flaws

• Sensor technologies

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Construction

• Foundations – intelligent compaction

White

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Construction

• Real time smoothness

Allows contractor to learn and control critical

activities

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Field Investigation

• Base on time-of-flight of light (LIDAR)

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Field Investigation

• LIDAR output

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When to Saw?

• Ultrasonic P-wave velocity

Measure speed of a compression wave

through a sample

Governed by dynamic modulus of elasticity,

Poisson’s ratio, and density (Biot’s theory)

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When to Saw?

• Lab data

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When to Saw?

• Field data

Early entry saw

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When to Saw?

• Field data

Conventional saw

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Finding the Steel

• Sensors

MIT Scan-2

MIT Scan-T2

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Finding Flaws

• GPR Scan

• MIRA

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Whew

• Use the right test for the right purpose at the

right time

• It can keep us out of trouble