ENGINEERING CONCRETE MIXES FOR LOCAL NEEDS. Dan King, E.I.T. Iowa Concrete Paving Association

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1 ENGINEERING CONCRETE MIXES FOR LOCAL NEEDS Dan King, E.I.T. Iowa Concrete Paving Association

2 OUTLINE Performance Engineered Mixtures Implementation in Iowa Experiences to Date

3 BACKGROUND Many aspects of concrete pavements have changed over the years: Mix design (SCMs, gradations, chemical admixtures) Construction (slipform paver) Maintenance (de-icing chemicals) Images: Todd Hanson, Iowa DOT

4 BACKGROUND In recent years, some concrete pavements have not achieved sufficient long-term durability Iowa: joint deterioration in urban areas Image: CP Tech Center

5 PERFORMANCE ENGINEERED MIXTURES (PEM) Concrete pavement mixtures engineered to enhance long-term durability in the environment in which they serve Cold climates/freeze-thaw Local materials Urban environment

6 PERFORMANCE ENGINEERED MIXTURES (PEM) Key points of emphasis: Low w/cm ratio About 30-40% replacement with SCMs Fly ash, slag Air entrainment

7 LOWERING W/CM Target w/cm: 0.40 Maximum allowable: 0.42 to 0.45 Less permeable = more durable Slows time to critical saturation freeze-thaw damage Helps limit infiltration of de-icing chemicals Image: CP Tech Center

8 SCM REPLACEMENT Primary motivation: increasing use of de-icing salts Salts like CaCl 2 and MgCl 2 can keep pavements saturated Images: CP Tech Center

9 SCM REPLACEMENT Primary motivation: increasing use of de-icing salts Salts like CaCl 2 and MgCl 2 can keep pavements saturated And result in direct chemical attack on the concrete itself Calcium oxychloride Image: CP Tech Center

10 SCM REPLACEMENT De-icing chemicals react with CH in the concrete microstructure to produce oxychlorides

11 SCM REPLACEMENT How SCMs help with chemical attack: Cement + = C-S-H Water + SCM + Water + CH = more C-S-H Source: CP Tech Center

12 SCM REPLACEMENT End result: significant improvement in durability Consuming CH inhibits oxychloride formation to resist chemical attack Producing more C-S-H further densifies the microstructure & reduces permeability Source: CP Tech Center

13 SCM REPLACEMENT Recommended replacement rate for PEM pavement mixtures: 30-40% by weight of cement Fly Ash Class C and Class F Slag

14 AIR ENTRAINMENT Minimum 6% behind the paver Recognize the importance of air void spacing Images: FHWA

15 Percent Retained OTHER COMMON PEM CHARACTERISTICS Ohio Use of water reducers Three aggregate systems Tarantula curve QM-C Non-mix related features: No backer rod Experimentation with surface sealers Excessive amount creates workability Issues Creates surface finishability problems typically associated with manufactured sands 0 #200 #100 #50 #30 #16 #8 #4 3/8 1/2 3/ /2 Sieve Size Excessive amount that decreases workability and promotes segregation and edge slumpling

16 IMPLEMENTATION IN IOWA National Implementation: AASHTO draft standard, champion state DOTs Iowa: Local agencies leading the way West Des Moines Council Bluffs Johnston

17 IMPLEMENTATION IN IOWA West Des Moines, 2015: Microsoft Alluvion $1.2 billion data center with corresponding $70 million in infrastructure improvements Image: HR Green

18 IMPLEMENTATION IN IOWA West Des Moines, 2015: Microsoft Alluvion M-QMC mix based on QM-C Pea gravel as third aggregate 33% replacement with Class C Fly Ash 0.40 target w/cm with 0.42 max Minimum 400 lbs. Type I Portland Cement Concern with late season paving Adjustment based on experience in Minnesota Resulted in 600 lbs. total cementitious as opposed to 560 lbs. Experimentation with surface sealers, new test methods

19 IMPLEMENTATION IN IOWA West Des Moines, 2015: Microsoft Alluvion Images: Jeremy Huntsman, HR Green

20 IMPLEMENTATION IN IOWA West Des Moines, 2015: Microsoft Alluvion Mix performance notes: Dry mix regularly ran at about 0.35 w/cm Responded well to vibration, easy to finish Some issues in setting up the curb

21 IMPLEMENTATION IN IOWA West Des Moines, 2016 M-QMC, now with limestone chip as third aggregate SCM switch to 35% Class F Fly Ash Continuation of minimum 400 lbs. Portland cement

22 IMPLEMENTATION IN IOWA West Des Moines, 2016

23 IMPLEMENTATION IN IOWA Council Bluffs, Limestone + Class V Aggregate Produces similar gradation to QM-C Use of Type 1PF cement (blend containing 25% F Ash) Additional 15% replacement with Class C Fly Ash Approximate final proportions: 64% Portland cement 36% fly ash 21% Class F 15% Class C No extra Portland cement required

24 IMPLEMENTATION IN IOWA Johnston, 2016 QM-C mix with limestone chip as third aggregate SCM replacement: 20% Class C Fly Ash 20% slag No extra Portland cement required

25 IMPLEMENTATION IN IOWA 2016 Performance Notes Positive feedback overall even with changes and variety of different mixes in use Mixes tend to be sensitive to water addition w/cm continues to run in 0.3s for most mixes West Des Moines: improving results on curbs

26 IMPLEMENTATION IN IOWA 2016 Performance Notes Set time concerns in Johnston and Council Bluffs Extended time to reach opening strength Upwards of days in Johnston Narrowing of sawing window some instances of raveling Not as significant a concern with higher cement mixes? No issues currently with longterm strength Image: CP Tech Center

27 MOVING FORWARD For any community seeing durability issues: these mixes are a potential solution Can implement as- or where-needed A variety of different options are available Agencies can choose what works best for them

28 MOVING FORWARD DOT Materials IM 529: C-SUD/CV-SUD mix C/M-QMC AASHTO draft standard will be published this spring

29 NEW CP TECH CENTER GUIDE Published Dec Guide to the Prevention and Restoration of Early Joint Deterioration in Concrete Pavements