Title: FHWA Mobile Concrete Laboratory: Bringing Technology to You
1FHWA Mobile Concrete Laboratory Bringing
Technology to You
- Prepared By
- Geoffrey J. Kurgan
- Prepared For
- Montana Highways Engineering Conference
- Billings, MT
2Agenda
- Program Overview
- Durability Related Tests
- Nondestructive Tests
- Technology Transfer
3A 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
4MCL 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
5Durability Tests
- Air Void Analyzer (AVA)
- Automated Petrography (ASTM C 457)
- Air Void Analyzer (AVA)
- Automated Petrography (ASTM C 457)
6AVA- 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
7AVA- 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
8AVA- 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
9AVA- 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
10AVA- Implementation
11AVA- Applications
- Widely used by cement and chemical admixture
companies - Prequalify/accept mixture designs
-
- QA/QC at time of construction
-
- Warranty specifications
12AVA- 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
13Automated 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
14Automated Petrography- Steps to Testing
- Cut, polish, and color specimen if necessary
- Place prepared specimen on stage of device
- Enact automated scanning
- Collect and analyse results
15Automated 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
16Automated Petrography- Applications
- Prequalify mixtures
-
- Correlate with AVA results
-
- Quality control if AVA is not being utilized
-
- Warranty specifications
17Automated 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)
18Nondestructive Tests / Software
- MIT Scan 2
-
- Maturity
-
- HIPERPAV II
19MIT 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
20MIT Scan 2- Steps to Testing
- Set rails centered on joint
- Enter book keeping and field inputs
- Scan joint
- Analyse results
21MIT 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
22MIT Scan 2- Implementation
23MIT 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
24MIT 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
25MIT 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
26Maturity- 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
27Maturity- Steps to Testing
- Fabricate and instrument samples
- Cure and test samples (record maturity before
testing) - Establish strength development curve
- Instrument structural element
- Read maturity to determine in place strength
28Maturity- 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
29Maturity- Theory
When MField MLab, the two concretes have
equivalent strengths
30Maturity- Implementation
From Tikalsky, Scheetz, and Tepke 2002
31Maturity- Implementation
32Maturity- 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
33Maturity- 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
34Maturity- 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
35HIPERPAV 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
36HIPERPAV II- Steps to Performing Analysis
- Erect weather station
- Enter geometric design and mixture properties
into baseline case - 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) - Perform analysis and assess the difference
between the strength gain and stress development
during the first 72 hours after concrete
placement - Consider changes to mixture design or
construction operations if necessary
37HIPERPAV II- Concept
38HIPERPAV 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
39HIPERPAV II-Applications
40HIPERPAV 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
41Additional 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
43Thanks
Contact gkurgan_at_fhwa.dot.gov