Presentation is loading. Please wait.

Presentation is loading. Please wait.

Performance Engineered Concrete Mixtures

Similar presentations


Presentation on theme: "Performance Engineered Concrete Mixtures"— Presentation transcript:

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!


Download ppt "Performance Engineered Concrete Mixtures"

Similar presentations


Ads by Google