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IBRACON Structures and Materials Journal • 2012 • vol. 5 • nº 5
Influence of the type of measuring device in determininging the static modulus of elasticity of concrete
and 12.6% for concrete classes C30 and C60. For 150mm x 500
mm specimens, modulus results obtained from dial indicators and
LVDTs presented larger variability. Results obtained using LVDTs
presented lowest modulus.
Since 100 mm x 200 mm specimens showed larger variability in the
modulus results, the variable “specimen size” was investigated in
further with more results shown in Figures 7 and 8. Figure 7 shows
the effect of specimen size and the effect of concrete type with con-
crete class C60 showing higher modulus results. Modulus results
obtained with 100 mm x 200 mm specimens had averages of 21.6
GPa and 27.6 GPa and their respective coefficients of variation were
21.6% and 20.5% for concrete classes C30 and C60. Modulus re-
sults obtained with 150 mm x 300 mm specimens had averages of
24.5 GPa and 27.7 GPa and their respective coefficients of variation
were 10.8% and 12.2% for concrete classes C30 and C60.
Figure 8 show the effect of measuring device interacting with
specimen size and the behavior explained earlier is the same.
Again, highest variability is shown in results obtained with LVDTs.
For 100mm x 200 mm specimens, modulus results (see Figure
8) obtained using strain gages had an average of 26.8 GPa and
the coefficient of variation was 14.7%. Results obtained with dial
indicators had an average of 27.7 GPa and the coefficient of varia-
tion was 21.9%. Results obtained with clip gages had an average
of 25.7 GPa and the coefficient of variation was 15.9%. Results
obtained with LVDTs had an average of 17.7 GPa and the coef-
ficient of variation were 18.5%. For 100mm x 200 mm specimens,
modulus results obtained from dial indicators and LVDTs present-
ed larger variability.
For 150mm x 300 mm specimens, modulus results (see Figure
8) obtained using strain gages had an average of 28.3 GPa and
the coefficient of variation was 6.6%. Results obtained with dial
indicators had an average of 27.4 GPa and the coefficient of varia-
tion was 6.2%. Results obtained with clip gages had an average
of 26.8 GPa and the coefficient of variation was 12.9%. Results
obtained with LVDTs had an average of 22.0 GPa and the coef-
ficient of variation were 11.3%. For 150 mm x 300 mm specimens,
modulus results obtained from clip gages and LVDTs presented
larger variability.
4. Conclusion
The analysis of the results obtained before considered the influ-
ence of measuring device, concrete class and specimen size. The
most important conclusions of this study were:
Figure 6 – Static modulus of elasticity versus specimen size, type of concrete
and strain measurement device
Size 100x200 (mm)
Size 150x300 (mm)
Electrical
Surface Bonded
Strain Gages
C60 C30
12
14
16
18
20
22
24
26
28
30
32
34
Dial Indicators
C60 C30
Externally Fixed
Strain Gages
C60 C30
Linear Variation
Displacement
Transducer
C60 C30
Concrete
Strain Measurement Device