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FHWA Mobile Concrete Laboratory: Bringing Technology to You

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Title: FHWA Mobile Concrete Laboratory: Bringing Technology to You


1
FHWA Mobile Concrete Laboratory Bringing
Technology to You
  • Prepared By
  • Geoffrey J. Kurgan
  • Prepared For
  • Montana Highways Engineering Conference
  • Billings, MT

2
Agenda
  • Program Overview
  • Durability Related Tests
  • Nondestructive Tests
  • Technology Transfer

3
A Brief History.
  • Developed in mid 80s as a technology transfer
    engine for implementing new equipment
  • Idea was to reduce the amount of time between
    conceptual and implementation phase
  • Foster a partnership between manufacturers,
    contractors, SHAs, industry associations, and
    academia
  • Assess new equipment and technology

4
MCL Tasks
  • Field work
  • Demonstration for SHAs and industry
  • Implementation for SHAs
  • Oversee an equipment loan program
  • Training
  • Technical support
  • Conference, convention, symposium, and workshop
    involvement
  • Support CPTP, DGIT, NHI, and TFHRC activities

5
Durability Tests
  • Air Void Analyzer (AVA)
  • Automated Petrography (ASTM C 457)
  • Air Void Analyzer (AVA)
  • Automated Petrography (ASTM C 457)

6
AVA- What Is It?
  • A fresh concrete test to determine
  • Percentage entrained air
  • Spacing factor
  • Specific surface
  • A QA/QC tool to ensure an adequate air void
    system for providing freezing and thawing
    resistance

7
AVA- Steps to Testing
  • Equipment
  • Percussion drill
  • Bird cage
  • Syringe
  • Riser column
  • Inverted petri dish
  • Electronic balance
  • Data acquisition system
  • 1. Prepare AVA unit
  • 2. Retrieve sample
  • 3. Inject sample and test
  • 4. Collect and analyse results

8
AVA- Steps to Testing
  • Equipment
  • Percussion drill
  • Bird cage
  • Syringe
  • Riser column
  • Inverted petri dish
  • Electronic balance
  • Data acquisition system
  • 1. Prepare AVA unit
  • 2. Retrieve sample
  • 3. Inject sample and test
  • 4. Collect and analyse results

9
AVA- Theory
Inverted petri dish connected to an electronic
balance
Rate of rise, function of Stokes Law
Riser column with Glyserin and water
Syringe with mortar sample
Dispersed mortar with suspended air voids
10
AVA- Implementation
11
AVA- Applications
  • Widely used by cement and chemical admixture
    companies
  • Prequalify/accept mixture designs
  • QA/QC at time of construction
  • Warranty specifications

12
AVA- Benefits/Limitations
  • Benefits
  • Provides an indication of air system in the fresh
    state
  • Reduces risk for contractor if air void
    characteristics are part of a performance related
    specification
  • Supported by AASHTO TIG
  • Limitations
  • Need to improve correlations for some
    formulations
  • Device highly sensitive, testing must be
    performed on stable surface

13
Automated Petrography- What Is It?
  • A hardened concrete test to determine
  • Percentage entrained/entrapped air
  • Spacing factor
  • Specific surface
  • A replacement for time consuming and costly
    manual tests

14
Automated Petrography- Steps to Testing
  1. Cut, polish, and color specimen if necessary
  2. Place prepared specimen on stage of device
  3. Enact automated scanning
  4. Collect and analyse results

15
Automated Petrography- Implementation
  • Used widely in Europe
  • In the U.S., primarily used by chemical admixture
    companies, RD firms, and QA/QC laboratories
  • Automated Concrete Evaluation System (ACES) is
    the result of a pooled fund study led by MoDOT

16
Automated Petrography- Applications
  • Prequalify mixtures
  • Correlate with AVA results
  • Quality control if AVA is not being utilized
  • Warranty specifications

17
Automated Petrography- Benefits/Limitations
  • Benefits
  • Testing can be completed in as little as 15
    minutes
  • More tests can be completed in a single day
  • Improved cost benefit compared to manual method
  • Eliminates some of the variability associated
    with the manual method
  • Limitations
  • Results returned after concrete hardens
  • Variability due to preparation (in some cases)

18
Nondestructive Tests / Software
  • MIT Scan 2
  • Maturity
  • HIPERPAV II

19
MIT Scan 2- What Is It?
  • Magnetic Imagining Tools
  • A method to evaluate dowel bar
  • Horizontal and vertical alignment
  • Depth
  • Side shift
  • Spacing
  • A means to predict joint performance

20
MIT Scan 2- Steps to Testing
  1. Set rails centered on joint
  2. Enter book keeping and field inputs
  3. Scan joint
  4. Analyse results

21
MIT Scan 2- Theory
  • Five transducers/sensors emit electromagnetic
    pulses
  • Pulses create an electromagnetic field around the
    dowel bar
  • Sensors record the signal intensity
  • Software calculates alignment and location

22
MIT Scan 2- Implementation
23
MIT Scan 2- Applications
  • Works on fresh or hardened concrete
  • Applicable for baskets or a DBI
  • Weather not a concern
  • Construction QA/QC
  • Process improvements
  • Basket anchoring procedure
  • DBI adjustments

24
MIT Scan 2- Benefits/Limitations
  • Benefits
  • Can scan a joint every 1-2 minutes
  • Can scan up to 3 lanes in a single pass
  • Accuracy (5 mm)
  • Cover material does not matter
  • Dowels can be positioned with a basket or DBI

25
MIT Scan 2- Benefits/Limitations
  • Limitations
  • Transport ties must be cut for a proper
    measurement
  • Dowel bars must be insulated (epoxy coated,
    galvanized, etc.)
  • Presence of other metal will influence readings
  • Must know dowel bar size for accurate results

26
Maturity- What Is It?
  • A means of estimating the in place strength of
    concrete
  • For a given mixture, concretes of the same
    maturity will have the same strength
  • Meters can be
  • Exposed and wired
  • Embedded and wired
  • Embedded and wireless

27
Maturity- Steps to Testing
  1. Fabricate and instrument samples
  2. Cure and test samples (record maturity before
    testing)
  3. Establish strength development curve
  4. Instrument structural element
  5. Read maturity to determine in place strength

28
Maturity- Theory
  • Maturity functions
  • Arrhenius- Equivalent age method
  • Nurse-Saul- Temperature time method
  • Nurse-Saul Function
  • Maturity is a function of the product of concrete
    temperature and curing time

29
Maturity- Theory
When MField MLab, the two concretes have
equivalent strengths
30
Maturity- Implementation
From Tikalsky, Scheetz, and Tepke 2002
31
Maturity- Implementation
32
Maturity- Applications
  • Removal of formwork
  • Opening pavement to traffic
  • Release strands in prestress industry
  • Current State specifications
  • Texas- TEX-426-A Estimating Concrete Strength by
    the Maturity Method
  • Iowa- Matls. I.M. 383 Method of Testing the
    Strength of Portland Cement Concrete Using
    Maturity Method

33
Maturity- Benefits/Limitations
  • Benefits
  • Allows for in place strength estimates
  • Can allow construction operations to proceed
    safely at the earliest possible time
  • Can increase speed of the construction operations
  • Can reduce amount and cost of conventional
    testing
  • Provides a means of temperature and curing
    management

34
Maturity- Benefits/Limitations
  • Limitations
  • Sensitive to high early curing temperatures
  • No single maturity function or strength
    development curve is applicable to all concrete
    mixtures
  • Must be supplemented with other tests for
    critical construction operations
  • For maximum accuracy, additional laboratory
    testing and analysis is necessary
  • Mixture variability is a concern

35
HIPERPAV II- What Is It?
  • A software for assessing the probability of
    uncontrolled cracking at early ages or later age
    distress in a concrete pavement
  • A means of considering the geometric design,
    mixture properties, construction operations, and
    environmental impacts simultaneously and prior to
    concrete placement

36
HIPERPAV II- Steps to Performing Analysis
  1. Erect weather station
  2. Enter geometric design and mixture properties
    into baseline case
  3. Input historical, proposed, or real time weather
    data and construction details (including time of
    placement, initial base material and concrete
    temperature, saw cutting operations, curing
    information)
  4. Perform analysis and assess the difference
    between the strength gain and stress development
    during the first 72 hours after concrete
    placement
  5. Consider changes to mixture design or
    construction operations if necessary

37
HIPERPAV II- Concept
38
HIPERPAV II- Implementation
  • FHWA provides free software at
  • http//www.fhwa.dot.gov/pavement/pccp/hipemain.cf
    m
  • FHWA Office of Pavement Technology and Resource
    Center is available for one day HIPERPAV II
    workshops reviewing the use of the software

39
HIPERPAV II-Applications
  • A Brief Example

40
HIPERPAV II- Benefits/Limitations
  • Benefits
  • Can be used as far in advance of placement as
    desired
  • Can input proposed weather conditions manually
  • Can alter construction operations to attempt to
    mitigate uncontrolled cracking
  • Can be used as a forensic tool
  • Limitations
  • Can not replace quality materials and meticulous
    construction operations
  • Mimics strength and stress development for a
    singular set of inputs

41
Additional MCL Technology Transfer Activities
  • Concrete Pavement Technology Program
  • Concrete Pavement Technology Program
  • Design Guide Implementation Team
  • Concrete Pavement Technology Program
  • Design Guide Implementation Team
  • NHI Materials Training Course
  • Concrete Pavement Technology Program
  • Design Guide Implementation Team
  • NHI Materials Training Course
  • Support TFHRC research

42
One More Test
43
Thanks
Contact gkurgan_at_fhwa.dot.gov
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