Page 60 - Riem-Vol6_nº2

231 IBRACON Structures and Materials Journal • 2013 • vol. 6 • nº 2
A. C. MARQUES | T. N. BITTENCOURT | M. P. BARBOSA
compares experimental results with those provided by NBR6118
[17] and ACI 209R [19] prediction models using slumps before and
after the addition of additives (5cm and 28cm, respectively).
Among the prediction models, the B3 [16] has more input data and
needs the mixture composition. The range allowed for the material
parameters are:
n Mean compressive strength (fcm): 17 ≤ fcm ≤ 70 MPa;
n water/cement ratio (a/c): 0.35 ≤ a/c ≤ 0.85;
n Cement content (c): 160 ≤ c ≤ 720 Kg/m³;
n aggregate/cement ratio in weight (ag/c): 2.5 ≤ ag/c ≤ 13.5.
The prediction model that requires less data is the GL [20], which
only specification concerning the cement is its type, which is con-
sidered in all prediction models.
Although the prediction models uses equations to predict the
modulus of elasticity from the compressive strength results, in this
paper were used the experimental results of compressive strength
and modulus of elasticity.
Besides the compatibility of the prediction models input, it is also
necessary to establish a criteria for their comparison. A method
widespread in the literature is proposed by Bažant and Panula [16].
The authors developed a statistical coefficient used for the com-
parison between the experimental results and predictions models
(wB3). According to Bažant and Baweja [16], it is considered a good
approximation the models with a coefficient up to 25%.
3. Results and discussions
The characterization tests results of the fresh SCC (slump-flow,
flow-rate, V-funnel, and L-box) are shown in Table 4. As can be
seen, the results of slump-flow, V-funnel, and L-box are consistent
with the concretes prescribed by NBR 15823-2 [7], NBR 15823-5
[9] NBR 15823-4 [8] as concrete of class SF1, VS2, VF2 and PL2.
The hardened SCC characterization was made by compressive
strength, splitting tensile strength, elastic modulus and drying
creep tests. The mean results from three specimens of the first
three tests are shown in Table 5. Those tests are made in order to
evaluate the material behavior over time and to provide data for the
creep prediction models, used in this paper.
The drying creep and drying shrinkage tests were made in both
specimens that was outside and inside the climated-controlled
chamber (humidity of 60 ± 4% and temperature of 23 ± 1ºC). From
this comparison it is possible to verify the influence of the environ-
ment on the long-term deformations.
The label for the specimens are according to the following order:
test condition (humidity and constant temperature - Chamber or
variations in humidity and temperature - Outside chamber), age
at loading or drying (14 days - 14 or 49 days - 49), the specimen
number (specimen 1-1 or specimen 2-2).
The measured strains for both drying creep and drying shrinkage
specimens can be seen in Figure 5.
As can be seen in Figure 5, the creep strains of the specimens
loaded at 14 days, and kept inside the climated-controlled chamber,
have higher total strain (approximately 2200me) than the specimens
kept outside the chamber (approximately 1800me). This difference
can be attributed mainly to the environmental humidity, since the
Table 4 – Properties of fresh SCC
Test Data Limits specified by
the standard code
Slum-flow (mm) 605 550 a 650 (SF1)
Flow-rate T (s)500 5 >2 (VS2)
L-Box (H /H )2 1 0,8 ≥0,8 (PL2)
V-funnel (s) 9 9 a 25 (VF2)
Table 5 – Compressive strength, splitting tensile strength and modulus of elasticity of SCC
Age (days)
Mechanical properties
Compressive strength
(MPa)
Splitting tensile
strength (MPa)
Modulus of elasticity
(GPa)
7 48.8 4.3 28.5
14 53.2 4.1 30.2
28 57.4 4.5 33.8
49 64.6 5.0 33.2
Figure 5 – Drying creep and drying shrinkage
deformations for both 14 and 49 days at loading
0 50 100 150 200 250 300 350 400 -1800
-1600
-1400
-1200
-1000
-800
-600
-400
-200
0
Creep deformation (

)
Time (days)
Outside chamber-14-1
Outside chamber-14-2
Outside chamber-14-sh
Chamber-14-1
Chamber-14-2
Chamber-14-sh
Outside chamber-49-1
Outside chamber-49-2
Outside chamber-49-sh
Chamber-49-1
Chamber-49-2
Chamber-49-sh