PSI - Issue 17

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

87

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

8

10 15 20 25 30 35 40 45

10 15 20 25 30 35 40 45

EC2 Exp.

Modulus of elasticity (GPa)

Modulus of elasticity (GPa)

0 5

0 5

n/d

n/d

L1

L2

L3

L4

L5

L6

L8

L9

L1

L2

L3

L4

L5

L6

L8

L9

Fig. 3a

Fig. 3b

Fig. 3. (a) Modulus of elasticity obtained in the SDT performed to the “as received specimens” (vertical bars); and estimated modulus of elasticity (the horizontal lines represent the estimated average value, and the bands delimited by the non-continuous lines represent ±1 standard deviation); n/d – not determined. Fig. 3. (b) Modulus of elasticity obtained in the SDT performed to the “as received specimens” (Exp.) and modulus of elasticity estimated from the compressive strength (EC2); n/d – not determined. To quantify damage and expansion in the concrete from ISR-affected structures several options can be considered. In-situ options include cracking index, CI; monitoring expansion/movements; assessing internal stresses and structural integrity. However, they are seldom applied ( e.g., many structures are not instrumented; CI involves repetition of measurements over a large period, is affected by concrete temperature and humidity and is operator dependent). Laboratory options include damage rating index (DRI) and mechanical tests (MT). DRI allows quantify extent of damage and possibly progression with time; however, is very time consuming, involves repetition of measurements over large periods, is somewhat subjective and results are dependent of petrographer experience. Typical MT (compression, flexural, tension, splitting tensile) allow assessing general condition of concrete, but do not allow quantifying expansion and damage. A promising method for this is the stiffness damage test, SDT (Crouch, 1987; Wood & Crouch, 1987; Chrisp, Crouch, et al., 1989; Chrisp, Wood, et al., 1989; Chrisp, et al., 1993). Because of that, several research studies have been conducted in order to develop it so that it can be used to predict the expansion attained to date by the concrete of ISR-affected structures ( e.g. , (Smaoui, 2003; Custódio, et al., 2013; Custódio & Ribeiro, 2014; Sanchez, 2014; Custódio & Ribeiro, 2015; Custódio, 2015-2019, 2017-2021)). The estimates of the total un-restrained expansion attained to date in the sampled concrete, calculated from the parameters obtained in the SDT carried out to the “as received specimens” and considering that the predominant swelling phenomenon was ASR, are presented in Table 5. Two methods were used. Method A considers that the modulus of elasticity of sound concrete is equal to the average value obtained for the specimens that exhibited a dissipated energy lower than 250 J/m 3 ; whilst Method B considers, for sound concrete, the modulus of elasticity estimates calculated according to EC2 using the compressive strength test results obtained for those specimens.

Table 5. Estimate of the total free expansion attained to date in the sampled concrete.

Total non-restrained expansion Method B (x10 -6 )

Approximate depth of extraction (m)

Location Specimen Total non-restrained expansion Method A (x10 -6 )

L1

1B 2A 5B 6A 9B

4800 3600 2500 3600 4600 5000 3700 4800 5300 4700 2400 2800 1200

4200

3800

4900 3600 2500 3600 4600 5100 3700 4800 5400 4800 2500 2800 1200

4300

3800

0.10 - 0.30 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 0.12 - 0.32

L2

3000

3100

L3

4800

4800

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

L4

4200

4300

L5

5000

5100

L6

2600

2600

L9

1200

1200