Develop a Simple and Rapid Test for Monitoring the Heat Evolution of Concrete Mixtures for both Labo

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Develop a Simple and Rapid Test for Monitoring
the Heat Evolution of Concrete Mixtures for both
Laboratory and Field Applications
Research Update
Kejin Wang
Material and Construction Optimization Project
Technology Advisory Committee Meeting, October
25, 2005, Comfort Suites, Ames, Iowa
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Objectives
To Develop

• Simple test procedures for cement and concrete
  heat evolution
• Rational method for interpretation of the test
  results
• Performance based specifications for the tests
• Models for predicting heat evolution of cement
  based on concrete materials and mix proportions

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Approach

• Phase I
• literature survey
• Phase II
• Study on Cementitious Materials
• Phase III
• Study on Concrete Materials

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Investigations in Phase I

• Factors affecting the concrete heat evolution
• Existing devices and test methods for heat
  evolution measurement
• Existing models for predicting heat of hydration
• Needs and potential applications of calorimeter
  tests

Phase II Proposal
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Existing Heat Evolution Tests

• (Semi-)Isothermal calorimeter
• (Semi-)Adiabatic calorimeter
• Dewar test (ISU)
• Coffee cup (Holcim)
• Sprayed-foam basket (Lafarge)

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Potential Applications of Heat Evolution Tests

• Characterize futures of cementitious materials
• Verify concrete mix proportions
• Identify incompatibility problems
• Predict concrete setting time
• Assess pavement sawing/finishing time
• Specify curing period
• Estimate risk of thermal cracking
• Select materials and mix designs

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Tests for Sulfate Depletion
Isothermal calorimeter test (Paul Sandberg, WR
Grace )
Cement should provide enough sulfate in solution
to retard aluminate until strength giving Alite
(C3S) hydration has taken off.
Sulfate depletion peak
Red Targeted Green, Yellow, Blue Balanced
Light Blue Unbalanced
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Tests for Admixture Overdose
Isothermal calorimeter test (Paul Sandberg, WR
Grace )
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Tests for Cement Characteristics
Isothermal calorimeter test (Peter Taylor, CTL )
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Tests for Admixture Dosages and Incompatibility
Coffee Cup Test (Gary Knight, Holcim)
Overdose
Incompatible?
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Tests for Effects of Delayed Addition of
Admixtures
Isothermal calorimeter test (Paul Sandberg, WR
Grace )
Delayed addition, only a few minutes, allows
aluminum hydration without interaction with
admixtures ? less chemisorption, less initial
heat, better admixture response
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Tests for Effects of Placement and Curing
Temperatures
Dewar test (G. Zhi and K. Wang, ISU)
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Phase II Research Program
Calorimeter Prototype System Development
EquipmentEvaluation
TestProcedure
Heat Index
Acceptance Criteria
Model
Field Trial Tests (in conjunction with MCO
project)
Test/Model Modification
Performance Based Specification/Guideline
Phase III Study
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Phase II Proposal

• Phase II Part A (Nov. 2005 June 2006)
• Select the equipment and conduct lab experiments
  to provide fundamental information for criteria
  and test procedure development.
• Establish heat evolution indexes to characterize
  concrete materials.
• Phase II Part B (April 2006 - September 2007)
• Predict concrete performance using heat
  evaluation indexes and HIPERPAV program.
• Develop performance-based specification for
  calorimeter equipment and test procedures.
• Conduct field study of the newly-developed
  calorimeter tests.

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Phase II Equipment Selection(TAM Air
Calorimeter)

• Isothermal calorimeter
• Able to capture initial heat
• Eight channels
• Small sample
• Less labor intensive
• Good accuracy
• More reproducible
• About 8,000

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Phase II Heat Index Development
Tmax, Max. Temperature
S2
Save
S1
Temperature ( oF)
A, Area under the curve (Maturity/Strength)
ti, Initial Set (turning point)
tTmax, Time at Tmax
Time (hour)
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Collaboration with MCO Project

• Evaluate heat evolution behavior of the field
  cementitious materials
• Characterize heat evolution curves obtained from
  the MCO field projects using the heat indexes
• Utilize the developed model to predict heat
  evolution of cementitious materials

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Trial Application of Heat Index in MCO Project
Test Results
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Phase II Intended Results

• A set of criteria for calorimeter equipment
  selection and development
• Test Procedures for evaluation the heat of
  hydration of cementitious materials and
  admixtures
• A set of indexes for characterization of heat
  evolution curves
• Initial models and software that are capable of
  converting the raw test data into easily
  understood test results
• A draft of an AASHTO specification for the
  recommended test method

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Seeking for More Inputs

• Your experience in heat signature tests
• Key issues in heat evolution tests
• Concerns and suggestions on this project

Questions?
Thank You!