Page 61 - Riem-Vol6_nº2

232 IBRACON Structures and Materials Journal • 2013 • vol. 6 • nº 2
Influence of the environment and loading age on SCC drying creep
average temperature outside the chamber for the first month of load-
ing was 20ºC. In this same period, the average humidity outside the
chamber for the first month of testing was 68%, while the average
humidity during the same period inside the chamber was 60%.
Regarding the creep results for the second load, it is observed that
the results of the specimens inside and outside the chamber are
close to each other, presenting approximately 200me of difference.
During the first month of the test for specimens loaded at 49 days,
the humidity outside the chamber was 64%.
A similar behavior can be observed in Figure 6, which shows the
experimental compliance function results. As previously stated,
during the second loading, the relative humidity inside and outside
the chamber showed a difference of about 4%, which is within the
accepted variation limits of humidity inside the chamber. This has
reflected on the experimental results by the proximity among the
compliance function curves shown in Figures 5 and 6.
The creep strain was obtained by subtracting the drying shrinkage
specimen strain from the mean strain from the loaded specimens.
After obtaining the experimental curve, the results were divided
by the applied load value, to originate the compliance function (J).
The Figure 6 shows the experimental compliance function curves
from specimens loaded at 14 days (Chamber-14) and 49 days
(Chamber-49). It can also be seen the curves from specimens kept
outside the chamber.
As can be seen in Figure 6, the values for the compliance function
for 365 days from specimens loaded at 14 days was 99me/MPa and
78me/MPa regarding specimens kept inside and outside the cham-
ber, respectively (i.e., a difference of 21% between the results). As
for the results from the specimens loaded at 49 days, were approx-
imately 72me/MPa and 82me/MPa for those which remained outside
and inside the chamber, respectively. These results show a 12%
difference between the measured values. The proximity between
the results obtained from the specimens loaded at 49 days were
already expected, since the relative humidity inside and outside
the chamber was similar during the test beginning.
The lowest compliance function value for the specimens kept in an
environment with higher relative humidity was expected because,
according to Mehta and Monteiro [2], and Neville [5], it would be
expected that the increase in atmospheric humidity would retard
the relative moisture flow rate from the interior to the exterior sur-
faces of the concrete.
Comparing the compliance function from specimens kept inside
and outside the chamber, it can be seen that there is a difference
Figure 6 – Compliance function for both
age at loading and storage condition
Figure 7 – Comparison among experimental
and prediction model results for
specimens kept inside the climated-controlled
chamber and age at loading of 14 days
Figure 8 – Comparison among experimental
and prediction model results for
specimens kept outside the climated-controlled
chamber and age at loading of 14 days