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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3. Laboratory testing campaign

3.1. Samples extracted from the structure

The laboratory test campaign was performed on twelve cores extracted from the underpass in areas exhibiting cracking. Table 1 shows the locations where the cores were extracted and details their number and size.

Table 1. Cores extracted from the underpass.

Location Structural element

Remarks

Core Diameter (mm) Length (m)

Slab beam 1, between columns line-up C1 and C2 Slab beam 2, between columns line-up C1 and C2 Slab beam 3, between columns line-up C1 and C2 Slab beam 1, close to column C2

Core extracted horizontally at mid height in the west side of the west beam, at mid span Core extracted horizontally at mid height in the west side of the central beam, at mid span C2 Core extracted horizontally at mid height in the east side of the east beam, at mid span C3 Cores extracted horizontally at low height in the west side of the west beam C4 C5 Core extracted horizontally at low height in the west side of the central beam C6 Core extracted horizontally at low height in the east side of the east beam C7 Cores extracted vertically in the east side of the deck, on the deck overhang, close to the pavement and near the abutment C8 C9 C1

L1

99

1.13

L2

99

1.25

99 99 99 99 99 99 99

1.19 0.68 1.09 1.14 1.14 0.27 0.49 0.28 0.80 0.31

L3

L4

L5

Slab beam 2, close to column C1

L6

Slab beam 3, close to column C1

Cantilever slab, between columns line up C2 and abutment A2

L8

C10 99 C11 99 C12 99

L9

Slab transverse beam at abutment A1

Cores extracted horizontally at mid height

3.2. Tests and analysis

3.2.1. Methodology The test campaign comprised the petrographic and microstructural analysis of the concrete, chemical analysis of the concrete (determination of the sulphate and alkali contents), evaluation of the potential for further expansion in the sampled concrete due to ASR and DEF, and the mechanical testing of the concrete (compressive and tensile splitting strengths and stiffness damage test). However, due to the limited length of this paper not all results of the study will be presented or discussed here. 3.2.2. Petrographic examination and microstructural characterisation The petrographic examination, made according to LNEC Specification E 388 (LNEC, 1993a), was performed on samples from all locations , to confirm the consistency in the concrete’s constituent materials throughout the deck, characterize the aggregate, identify the presence of potentially alkali-reactive constituents, and to observe any distress signs that allow to identify the mechanisms which might be contributing to the outward manifestations of damage. The test samples were prepared according to LNEC Specification E 389 (LNEC, 1993b). The examination was complemented with a microstructural characterization of the concrete by scanning electron microscopy with energy dispersive X-ray analysis, SEM/EDS, to evaluate the concrete microstructure and to determine the extension, localization and chemical composition of any expansive reaction compounds present in the concrete samples. The SEM/EDS characterization was made according to LNEC Specification E 402 (LNEC, 1993d). 3.2.3. Chemical analysis The chemical analysis, namely the determination of the concrete alkali and sulphate contents, was made to verify if the limits established in LNEC Specification E 461 (LNEC, 2007b) were fulfilled, as they provide an indication about the likelihood of ISR development. The analysis was performed to a sample from location L6, according to LNEC Internal Method LABTEC MI 115 (LNEC, 2007a).