B Persson, LTH Building Materials, University of Lund, Lund, Sweden ON THE TEMPERATURE EFFECT ON SELF-DESICCATION OF CONCRETE Experimental setup: l 250 mm “thick” cylinders, diameter 150 mm l Curing temperatures l Relative humidity, RH at a depth of 20% of the slab thickness l Weight

B Persson, LTH Building Materials, University of Lund, Lund, Sweden ON THE TEMPERATURE EFFECT ON SELF-DESICCATION OF CONCRETE Parameters: l Water-cement ratio, 0.38, 0.43 and 0.55 l Sealed or water curing at 8°C, 20°C and 30°C, 1st month l 20°C 60 % RH after 1 month, some exposed to wind, some sealed l RH measured at 1, 1½, 2, 3 and 6 months

B Persson, LTH Building Materials, University of Lund, Lund, Sweden ON THE TEMPERATURE EFFECT ON SELF-DESICCATION OF CONCRETE Effect of maturity on strength:

B Persson, LTH Building Materials, University of Lund, Lund, Sweden ON THE TEMPERATURE EFFECT ON SELF-DESICCATION OF CONCRETE Temperature effect on self-desiccation: averages of three values

B Persson, LTH Building Materials, University of Lund, Lund, Sweden ON THE TEMPERATURE EFFECT ON SELF-DESICCATION OF CONCRETE Self-desiccation vs. strength :

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

B Persson, LTH Building Materials, University of Lund, Lund, Sweden 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

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

B Persson, LTH Building Materials, University of Lund, Lund, Sweden ON THE TEMPERATURE EFFECT ON SELF-DESICCATION OF CONCRETE RH of concrete with w/c = 0.38: Age (days) In water +30°C +8°C dried sealed +20°C Sealed

B Persson, LTH Building Materials, University of Lund, Lund, Sweden ON THE TEMPERATURE EFFECT ON SELF-DESICCATION OF CONCRETE RH of concrete with w/c = 0.43: Age (days) +8°C +30°C sealed In water dried sealed dried +20°C Sealed

B Persson, LTH Building Materials, University of Lund, Lund, Sweden ON THE TEMPERATURE EFFECT ON SELF-DESICCATION OF CONCRETE RH of concrete with w/c = 0.55: Age (days) In water wind +20°C Sealed +8°C +30°C

B Persson, LTH Building Materials, University of Lund, Lund, Sweden ON THE TEMPERATURE EFFECT ON SELF-DESICCATION OF CONCRETE Summary and conclusions, 1 : l 27 specimens 150 mm in diameter, 250 mm in length with w/c = 0.38, 0.43, l Effects of heating, sealing, water and wind l 28-day strength 20% higher after curing at 8 °C compared to 30 °C. l 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.

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

B Persson, LTH Building Materials, University of Lund, Lund, Sweden ON THE TEMPERATURE EFFECT ON SELF-DESICCATION OF CONCRETE T1T1 T cur <T 1 wnwn  RH