PSI - Issue 17

João Custódio et al. / Procedia Structural Integrity 17 (2019) 80–89 João Custódio et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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The results show again a great variability on the condition of the concrete sampled throughout the deck, with the individual values varying between 2.3 MPa (location L6) and 3.2 MPa (location L4). The lowest compressive strength was also obtained for the concrete sampled in location L6 (Fig. 1a). With the exception of locations L1 and L4, all tensile splitting strength experimental values are below the lower estimate value for sound concrete. If the higher estimate is considered instead, then all experimental values are below the estimate. This suggests that some internal damage could exist in the sampled concrete, or it may simply derive from limitations in sampling representativeness. 4.4.3. Stiffness damage test The results obtained in the stiffness damage test are shown in Table 4 and Fig. 3. Fig. 3a shows the modulus of elasticity determined experimentally for the “as received specimens”, and also the modulus of elasticity estimates, calculated according to EC2 (IPQ, 2010), using the compressive strength estimates made in section §4.4.1. This results in a modulus of elasticity, for a 17 years old concrete, of 34 GPa (β = 1.26) and of 35 GPa (β = 1.43). Fig. 3b shows the modulus of elasticity determined experimentally for the “as received specimens” and the modulus of elasticity estimates, calculated according to EC2 (IPQ, 2010), using the compressive strength values of those same specimens. The results show that the modulus of elasticity of the concrete varies somewhat between the different locations sampled, with the individual values varying between 12.1 GPa (location L5) and 24.5 GPa (location L9). The lowest compressive strength was also obtained for the concrete sampled in location L6 (Fig. 1a). With the exception of location L8, which was not assessed, all experimental values are below the lower estimate value for sound concrete (Fig. 3a). Furthermore, when comparing the experimental values with the correspondent estimated values for sound concrete, using the compressive strength (Fig. 3b), it is observed that the modulus of elasticity is again below what was expected in all evaluated locations. This suggests that some internal damage may exist in the concrete sampled in locations L1 to L6 and L9, and the difference does not derive just from eventual limitations in the representativeness of the sampling. The corresponding values for accumulated final extension and energy dissipated in the first SDT cycle confirm the existence of internal damage in the concrete. The values obtained for the specimens from locations L1 to L5 are indicative of a relevant internal damage, whilst those obtained for locations L6 and L9 are indicative of some or almost no internal damage, respectively. Therefore, the results suggest that, in the concrete sampled, the swelling reactions have developed sufficiently to cause a degradation of the mechanical properties.

Table 4. Results obtained in the stiffness damage test carried out to the “as received specimens” .

Accumulated final extension (x10 -6 )

Dissipated energy (J/m 3 )

Approximate depth of extraction (m)

Location Specimen Elasticity modulus (GPa)

i)

ii)

iii) i)

ii)

iii)

i)

ii)

iii)

L1

1B 2A 5B 6A 9B

13.1 14.6 16.1 260

215

194

1862 1537 1369 0.10 - 0.30

16.1

170 130 180 240 260 210 250 280 220 120 120

1212

0.30 - 0.50 0.12 - 0.32 0.32 - 0.52 0.12 - 0.32 0.32 - 0.52 0.10 - 0.30 0.30 - 0.50 0.12 - 0.32 0.32 - 0.52 0.12 - 0.32 0.32 - 0.52

L2

19.7 18.1

155

871 1073

16.5

1274

L3

14.0 13.4

250

1629 1779

10A 16B 17A 20B 21A 24B 25A 36B

12.7

1930

L4

16.2 14.8

230

1438 1613

13.3

1789

L5

12.1 12.7

250

2040 1840

13.3

1640

L6

19.9 19.1

120

805 821

18.4

838

L9

24.5 24.5 0.12 - 0.32 NOTE: i) individual test result; ii) average per location; iii) overall average. 80 80 465 465