1. Performance Engineered Concrete Mixtures
Peter Taylor
National Concrete Pavement Technology Center
With thanks to
Jim grove, FHWA, and
Dr Ezgi Yurdakul, Verifi

2. The Goal
Help the industry get:
Performance they need
With the materials available
With minimum impact (environment / cost)

3. When did you last “design” a mixture?
Readymix operator
Some regularly, others never
Consultant
May review before “approving”
Owner
Mmm
Contractor
Only for bidding
Researchers
Of course!

4. View Points
To the readymix operator - Push the envelope
To the consultant - Crunch those numbers
To the contractor - Make it flow, then magically set
To the materials suppliers - Use more of our stuff
To the owner - Make it last forever

5. Mixture Design
Process of determining required and specifiable characteristics of a concrete mixture:
i.e. Choosing what you want

6. Mixture Proportioning
Process of determining the quantities of concrete ingredients available
i.e. choosing what to use to get what you want

7. Design and Proportioning
Who should choose what?
Strength
Slump
Air content
w/cm
Cement content
SCM percentage
Aggregate grading
Admixture dosage

8. Current Proportioning Technologies
Developed
Before water reducers
Before supplementary cementitious materials
Primarily focused on structural concrete
100 mm (4”) slump
30 MPa (~4000 psi)
ACI 211 last revised in 1991

9. Common Misconceptions
More cement means stronger concrete
Supplementary cementitious materials are dilutants
Stronger concrete is more brittle & that is bad
Strength and workability are correlated
Strength and durability are correlated

10. Absolute Volume Approach
Paste volume based on coarse aggregate size
Coarse aggregate volume based on subtracting the fineness modulus (FM) of sand from a fudge factor
Fill the remaining volume with sand

11. Absolute Volume Approach
Higher fineness modulus
Means coarser sand
Therefore more mass needed to fit between rock particles
Leads to less coarse aggregate

12. Absolute Volume Approach
Shortcomings
Little account for:
Supplementary cementitious materials
Admixtures
Aggregate texture

13. What Do We Really Want
Contractor
Cost
Workability
Strength
Owner
Reliability
Value

14. Proposed Mixture Proportioning Procedure
Choose the Aggregate System
Combined gradation
Determine void ratio
Account for shape and texture

15. Proposed Mixture Proportioning Procedure
Choose the Aggregate System
Influences
Workability
Segregation
Paste requirement

16. Proposed Mixture Proportioning Procedure
Choose a Paste System
Cementitious blend
W/Cm
Air content
Chemical admixtures

17. Proposed Mixture Proportioning Procedure
Choose a Paste System
Influences
Workability
Setting
Hardened properties

18. Proposed Mixture Proportioning Procedure
Choose Paste Volume
All voids must be filled with paste
Additional paste to coat the particles for workability

19. Proposed Mixture Proportioning Procedure
Choose Paste Volume
Influences
Workability
Hardened properties up to a point

20. Proposed Mixture Proportioning Procedure
Add something = take something else out
Interactions
Aggregate system
Paste quality
Paste quantity

21. Proposed Mixture Proportioning Procedure
Are we there yet?
Aggregate system – some
Paste quality – mostly
Paste volume – some
Interactions – some
Working on it…

22. Lets discuss!