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ON THE TEMPERATURE EFFECT ON SELF-DESICCATION OF CONCRETE

ON THE TEMPERATURE EFFECT ON SELF-DESICCATION OF CONCRETE. Experimental setup: 250 mm “thick” cylinders, diameter 150 mm Curing temperatures Relative humidity, RH at a depth of 20% of the slab thickness Weight. ON THE TEMPERATURE EFFECT ON SELF-DESICCATION OF CONCRETE. Parameters:

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ON THE TEMPERATURE EFFECT ON SELF-DESICCATION OF CONCRETE

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  1. ON THE TEMPERATURE EFFECT ON SELF-DESICCATION OF CONCRETE Experimental setup: • 250 mm “thick” cylinders, diameter 150 mm • Curing temperatures • Relative humidity, RH at a depth of 20% of the slab thickness • Weight

  2. ON THE TEMPERATURE EFFECT ON SELF-DESICCATION OF CONCRETE Parameters: • Water-cement ratio, 0.38, 0.43 and 0.55 • Sealed or water curing at 8°C, 20°C and 30°C, 1st month • 20°C 60 % RH after 1 month, some exposed to wind, some sealed • RH measured at 1, 1½, 2, 3 and 6 months

  3. ON THE TEMPERATURE EFFECT ON SELF-DESICCATION OF CONCRETE Effect of maturity on strength:

  4. ON THE TEMPERATURE EFFECT ON SELF-DESICCATION OF CONCRETE Temperature effect on self-desiccation: averages of three values

  5. ON THE TEMPERATURE EFFECT ON SELF-DESICCATION OF CONCRETE Self-desiccation vs. strength :

  6. Sealed 28d. at +30C ON THE TEMPERATURE EFFECT ON SELF-DESICCATION OF CONCRETE Effect of w/c and water curing on drying: Sealed 21d. at +30C, 7d. in water, then dried 28d. at 60 % RH Sealed 28d. at +30C, then dried 28d. at 60 % RH

  7. ON THE TEMPERATURE EFFECT ON SELF-DESICCATION OF CONCRETE Effect of wind on drying, various w/c: Sealed 28d. at +20C, then dried 28d. at 60 % RH

  8. ON THE TEMPERATURE EFFECT ON SELF-DESICCATION OF CONCRETE Effect of w/c and temperature on drying: Sealed 28d. at: (then dried 28d. at +20°60%RH) +30°C +8°C

  9. ON THE TEMPERATURE EFFECT ON SELF-DESICCATION OF CONCRETE RH of concrete with w/c = 0.38: In water +30°C Sealed +8°C sealed dried +20°C Age (days)

  10. ON THE TEMPERATURE EFFECT ON SELF-DESICCATION OF CONCRETE RH of concrete with w/c = 0.43: In water +30°C sealed Sealed +8°C dried sealed dried +20°C Age (days)

  11. ON THE TEMPERATURE EFFECT ON SELF-DESICCATION OF CONCRETE RH of concrete with w/c = 0.55: In water +8°C Sealed +30°C +20°C wind Age (days)

  12. ON THE TEMPERATURE EFFECT ON SELF-DESICCATION OF CONCRETE Summary and conclusions, 1: • 27 specimens 150 mm in diameter, 250 mm in length with w/c = 0.38, 0.43, 0.55. • Effects of heating, sealing, water and wind • 28-day strength 20% higher after curing at 8 °C compared to 30 °C. • Self-desiccation was more pronounced after curing at 8 °C than at 30 °C, at the same age! • 1 week of water curing gave 4% higher RH for low w/c =0.38 and for w/c =0.55.

  13. ON THE TEMPERATURE EFFECT ON SELF-DESICCATION OF CONCRETE Summary and conclusions, 2: • Wind of 4 m/s had no influence on the drying, except possibly some for w/c =0.55. • The maturity concept could not be applied to strength or to self-desiccation. • Probable explanation: Micro & pore structure at low temperature curing became finer.

  14. wn Tcur<T1 T1 DRH ON THE TEMPERATURE EFFECT ON SELF-DESICCATION OF CONCRETE

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