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Session 10 Purdue Research Updates Using Internal Curing in Concrete Bridge Decks

Session 10 Purdue Research Updates Using Internal Curing in Concrete Bridge Decks. Purdue University School of Civil Engineering. Update in Research Study on Using Internal Curing in Concrete Bridge Decks.

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Session 10 Purdue Research Updates Using Internal Curing in Concrete Bridge Decks

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  1. Session 10 Purdue Research Updates Using Internal Curing in Concrete Bridge Decks

  2. Purdue University School of Civil Engineering Update in Research Study on Using Internal Curing in Concrete Bridge Decks Developed for Discussion with the Road School by:Carmelo Di Bella, John Schlitter, Igor De La Varga Nathan Phares and Jason Weiss March 9th, 2011

  3. Outline • Difference between external and internal curing • Importance of Internal curing • Benefits of internal curing • Possible improvements in terms of service life and CO2 emission reduction • Conclusion

  4. Outline • Difference between external and internal curing • Importance of Internal curing • Benefits of internal curing • Possible improvements in terms of service life and CO2 emission reduction. • Conclusion

  5. What Is external Curing? • External curing Bloomington, 2010 • Supply of water to the concrete can be accomplished by ponding, spraying, or by use of saturated coverings.

  6. What Is Internal Curing? • Internal Curing SAP Haydite LWA

  7. What is Internal Curing • ACI “Supplying water throughout a freshly placed cementitious mixture suing reservoirs, via prewetted Lightweight aggregate, that readily release water as needed for hydration or to replace moisture lost through evaporation or self desiccation” • Hiding Water In LWA to increase hydration and strength while reducing transport, shrinkage, and cracking

  8. What Is Internal Curing?

  9. Outline • Difference between external and internal curing • Importance of Internal curing • Benefits of internal curing • Possible improvements in terms of service life and CO2 emission reduction • Conclusion

  10. Fundamental Volume Change • Le Chatelier 1850-1936 • Chemical Shrinkage: The apparent volume of the cement paste may increase but there is a substantial decrease in its absolute volume. = +

  11. Concept – LWA Supplies Water • Water stays in LWA until the time that this under pressure develops • At that point water would be drawn out of bigger pores in LWA in a perfect world

  12. IC Mixture Proportion – How much water does the system want? • LWA: water reservoirs that release water at the appropriate time (after set) • Hypothesis: All Chemical Shrinkage water is replaced • Bentz (1999) equation

  13. Outline • Difference between external and internal curing • Importance of Internal curing • Benefits of internal curing • Possible improvements in terms of service life and CO2 emission reduction • Conclusion

  14. Internal Curing Increases Hydration Castro 2010

  15. Relative Humidity Castro 2010

  16. Applications • Texas – Pavement Construction • NYDOT – 10+ Decks with IC • Reviewed and walked these decks • One crack in the negative region on a very wide bridge with a high skew • No problems reported • Additional Cost ($10 /yd3) • IN-LTAP – 1 with IC, 1 conventional • No Problems reported, • VADOT – Bridge Deck

  17. LTAP Project • To Evaluate Internal Curing in Two Bridges (With Internal Curing and Without) • To Document with Local Materials • To Aide in Understanding What May Be Needed from Specification and What May Be Needed in A Change of Process • Overall – Improve Service Life Performance for Limited Cost by Being More Efficient

  18. Location • Two Bridges Near One Another • Similar Exposure/Traffic • Wanted to Monitor Long Term Performance

  19. Conventional Bridge

  20. Typical Construction

  21. Internally Cured Deck

  22. Findings of the IC Project • Early on (up to 5 days) similar strength • At 28 days Internal curing increases strength (Increased Hydration)

  23. Findings of the IC Project • At 28 days similar chloride resistance • At 91 Days 25% more resistance to chloride ingress (Increased Hydration)

  24. An Interesting Aside • INDOT Class C – 5.5 k-Ohm/cm (90 d) • With Internal Curing – 7.0 k-Ohm/cm (90 d) • NYDOT Bridge Deck – 32 k-Ohm/cm (90 d) • There is room for Indiana to reconsider the designs using to increase resistance to chlorides and increase service life

  25. Outline • Difference between external and internal curing • Importance of Internal curing • Benefits of internal curing • Possible improvements in terms of service life and CO2 emission reduction • Conclusion

  26. Current State FHWA/INDOT • Goal is to reduce the clinker content of concrete used in transportation structures • Class C concrete bridge requires 390 kg/m3 of cementitous • Current limit of 20-25% fly ash Columbus Indiana

  27. From FHWA/DOT Perspective • w/c – 0.42 and w/c -0.3 - 40% ash have equivalent 1 day strength but have a 40% reduction in CO2 per yd3 of concrete • w/c – 0.42 and w/c -0.3 - 60% ash have equivalent 7 day strength but have a 60% reduction in CO2 per yd3 of concrete

  28. Impact of HVFA on Microstructure De LA Varga 2011

  29. Conclusion Showing Benefits (reduced cracking slowed chloride ingress, similar strength) Uses cement more efficiently – increases degree of hydration Enables ‘greener’ concrete as OPC can be replaced (limestone, ash, slag) Increases ‘reserve capacity’ for temperature effects during construction Reduces fluid transport which can extend service life giving more bang for the buck

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