PSI - Issue 64

Antonio Bossio et al. / Procedia Structural Integrity 64 (2024) 56–64 Author name / Structural Integrity Procedia 00 (2019) 000–000

62

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4.5. Effect of concrete cover An important design consideration for RC structures is the thickness of the concrete cover surrounding the rebars. This cover protects the rebar from corrosion. How different cover thicknesses (20mm, 30mm, and 40mm) affect the bond between the rebar and concrete for a 16mm diameter rebar in C25/30 concrete was examined (see Figure 5d). Concrete cover thickness significantly impacts how much the rebar reduces due to oxidation (bar reduction, x ). Thicker concrete cover provides more protection and slows down reduction.

1.60

1.60

Ω p,trEC2

Ω p,trMC10

1.00

1.00

ϕ=0 ϕ=0.5

ϕ=1 ϕ=2 ϕ=3

ϕ10 bars ϕ16 bars ϕ20 bars

0.40

0.40

0.0

6.0

12.0

0.0

7.0

14.0

x [µm]

x[µm]

1.60

1.80

Ω p,trEC2

Ω p,trMC10

1.00

1.00

C20/25 C25/30 C30/37 C40/50

cc=20 mm cc=30 mm cc=40 mm

0.40

0.0

7.0

14.0

0.20

x [µm]

0.0

7.0

14.0

x [µm]

1.6

1.6

Ω p,trEC2

Ω p,trEC2

n=2 n=2.5

1

1.0

n=3 n=4 n=5 n=6

Eo=130 MPa Eo=1000 MPa Eo=210,000MPa

0.4

0.4

x [µm]

0

8

16

0.0

3.5

7.0

x [µm]

Fig. 5. (a) Ω p,trEC2 vs bar reduction, x , – class XC4 – bar diameter comparison – EC2, (b) Ω p,trMC10 vs bar reduction, x , – creep effect according to MC10, (c) Ω p,trEC2 vs bar reduction, x , – concrete class comparison according to EC2, (d) Ω p,trMC10 vs bar reduction, x , – concrete cover, cc, comparison according to MC10, (e) Ω p,trEC2 vs bar reduction, x , – oxide volumetric expansion factor, n , effect, according to EC2, (f) Ω p,trEC2 vs bar reduction, x – oxide elastic modulus, E o , effect, according to EC2. The amount of oxide ( x ) has little effect on the maximum improvement in bond strength ( Ω p,tMC2010 ). However, a thicker cover allows for more reduction before the concrete cover cracks completely. This also leads to a higher internal pressure ( f l ) from the oxide pushing outwards.