PSI - Issue 17

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

85

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

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sampled on locations L1 to L6. An opposite trend was observed for locations L8 and L9 (for which the approximate extraction depth of the “as received specimens” and the “ASR tested specimens” is similar – 0.10-0.43 m vs 0.05-0.25 m for L8, and 0.12-0.32 m vs 0.10-0.84 m for L9 ). The largest difference in the values obtained for the “as received specimens” and “ASR/DEF tested specimens” was re gistered for the concrete that expanded the most in the residual expansion test, i.e. , locations L4 (-31 %), L5 (-25 %) and L6 (-19 %) for ASR, and locations L4 (-37 %), L6 (-28 %), L5 (-23 %) and L2 (-23 %) for the DEF. These differences might be related to variations in concrete composition in the several locations sampled, but, if the residual expansion values are taken into account, they most likely derive from concrete degradation. In this case, the diverse levels of degradation could be associated to the local concrete composition, the structural element dimensions, and the specific environmental exposure conditions. On average and excluding location L8, for which the residual expansion due to DEF was not assessed, the compressive strength of the “DEF tested specimens” (36 MPa) was lower than that of the “ASR tested specimens” ( 39 MPa); this may be due to the higher test temperature of the ASR test, which may lead to a larger additional hydration of the cement. Nevertheless, both values are lower t han that of the “as received specimens”, 45 MPa, meaning that there is still potential for concrete compressive strength deterioration if expansion evolves further in the structure.

10 15 20 25 30 35 40 45 50 55 60 65 70

10 15 20 25 30 35 40 45 50 55 60 65 70

As received specimens DEF tested specimens ASR tested specimens

Compressive strength (MPa)

Compressive stregnth (MPa)

0 5

0 5

L8 n/d

L1

L2

L3

L4

L5

L6

L9

L1

L2

L3

L4

L5

L6

L8

L9

Fig. 1b

Fig. 1a

Fig. 1. (a) Compressive strength test results of the “as received specimens” (vertical bars); and estimated compressive strength s (the two bold horizontal lines represent the estimated average values, and the bands delimited by the non-continuous lines represent ±1 standard deviation). Fig. 1. (b) Compressive strength test results of the “as received specimens”, “ASR tested specimens”, and “DEF tested specimens” ; n/d – not determined. 4.4.2. Tensile splitting strength test Fig. 2 displays the tensile splitting strength determined experimentally for the “as received specimens”, as well as the tensile splitting strength estimates, calculated according to EC2 (IPQ, 2010), using the compressive strength estimates made in the previous section (§4.4.1). This calculation results in a tensile splitting strength, for a 17 years old concrete, of 3.2 MPa (β = 1.26) and of 3.5 MPa (β = 1.43).

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0

Tensile splitting strength (MPa)

n/d

n/d

L1

L2

L3

L4

L5

L6

L8

L9

Fig. 2. Tensile splitting strength test results of the “as received specimens” (vertical bars) , and estimated tensile splitting strengths (the two bold horizontal lines represent the estimated average values, and the bands delimited by the non-continuous lines represent ±1 standard deviation); n/d – not determined.