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Confinement effectiveness of CFRP strengthened ultra-high performance concrete cylinders exposed to elevated temperatures

Aref A. Abadel
Aref A. Abadel
 et 
Yousef R. Alharbi
Yousef R. Alharbi
   | 23 févr. 2022
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Publié en ligne: 23 févr. 2022
Pages: 478 - 490
Reçu: 20 nov. 2021
Accepté: 12 janv. 2022
DOI: https://doi.org/10.2478/msp-2021-0040
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© 2021 Aref A. Abadel et al., published by Sciendo
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Fig. 1

Fibers used in the present study: (A) Hooked-SF; (B) PVA fibers (C) PP fibers. PVA, polyethylene alcohol; PP, polypropylene; SF, steel fibers
Fibers used in the present study: (A) Hooked-SF; (B) PVA fibers (C) PP fibers. PVA, polyethylene alcohol; PP, polypropylene; SF, steel fibers

Fig. 2

Concrete cylinders; (A) during casting (B) after demolding
Concrete cylinders; (A) during casting (B) after demolding

Fig. 3

Curing of concrete specimens in the water tank
Curing of concrete specimens in the water tank

Fig. 4

Concrete cylinders inside the oven ready for heating
Concrete cylinders inside the oven ready for heating

Fig. 5

Time-temperature curves used in this study
Time-temperature curves used in this study

Fig. 6

Representative Concrete specimens after strengthened with CFRP sheet. CFRP, carbon fiber reinforced polymer
Representative Concrete specimens after strengthened with CFRP sheet. CFRP, carbon fiber reinforced polymer

Fig. 7

Instrumented specimen ready for testing
Instrumented specimen ready for testing

Fig. 8

View of representative specimens after heating-cooling cycle
View of representative specimens after heating-cooling cycle

Fig. 9

View of representative specimens after compression testing: (A) 26°C; (B) 400°C
View of representative specimens after compression testing: (A) 26°C; (B) 400°C

Fig. 10

CFRP rupture failure of confined post-heated UHPC specimens. CFRP, carbon fiber reinforced polymer; UHPC, ultra-high-performance concrete
CFRP rupture failure of confined post-heated UHPC specimens. CFRP, carbon fiber reinforced polymer; UHPC, ultra-high-performance concrete

Fig. 11

Stress-strain curves for UHPFRC cylinders before and after temperature exposure to 400°C. UHPFRC, ultra-high-performance fiber reinforced concrete
Stress-strain curves for UHPFRC cylinders before and after temperature exposure to 400°C. UHPFRC, ultra-high-performance fiber reinforced concrete

Fig. 12

Stress-strain curves for UHPC specimens before and after strengthened: (A) Case of no fibers; (B) Case of SF alone. UHPC, ultra-high-performance concrete
Stress-strain curves for UHPC specimens before and after strengthened: (A) Case of no fibers; (B) Case of SF alone. UHPC, ultra-high-performance concrete

Fig. 13

Confined to unconfined compressive strength comparisons for UHPC and UHPFRC specimens. UHPC, ultra-high-performance concrete; UHPFRC, ultra-high-performance fiber reinforced concrete
Confined to unconfined compressive strength comparisons for UHPC and UHPFRC specimens. UHPC, ultra-high-performance concrete; UHPFRC, ultra-high-performance fiber reinforced concrete

Test results summary of different UHPC mixes

Mix Compressive strength of concrete (MPa)
Before strengthened After strengthened
Room Temp. 400°C Room Temp. 400°C
M0 120.3 90.32 (−24.6%) 159.5 (32.6%) 139 (53.9%)
M1 139.8 (16.2%) 104.68 (−25.12%) 175.1 (25.3%) 167.2 (59.2%)
M2 134.6 (11.8%) 110.19 (−18.2%) 176.9 (31.4%) 167.5 (52.0%)
M3 131.7 (9.5%) 102.62 (−21.5%) 167.5 (27.1%) 158.2 (54.2%)
M4 128.2 (6.8%) 99.70 (−22.3%) 169.5 (32.2%) 150.2 (50.7%)
M5 127.8 (6.5%) 97.4 (23.7%) 163.8 (28.2%) 130.4 (33.9%)

Mixture proportions of UHPC for 1 m3

Material Weight (kg/m3)
Cement 900
Micro silica 222
Fine quartz sand 1,000
Water 164
Fiber 100
Super-plasticizer 30

Fresh properties of UHPC

Mix No. Slump (mm) Unit weight (kg/m3)
M0 280 2,318
M1 257 2,363
M2 256 2,325
M3 250 2,294
M4 255 2,310
M5 251 2,285

Fiber percent in different concrete mixes

Concrete mix Fiber percentage by volume (by weight)
PP SF PVA
M0 0.0 (0.00) 0.0 (0.00) 0.0 (0.00)
M1 0.0 (0.00) 1.0 (3.27) 0.0 (0.00)
M2 0.0 (0.00) 0.7 (2.29) 0.3 (0.16)
M3 0.1 (0.04) 0.7 (2.29) 0.2 (0.00)
M4 0.0 (0.00) 0.7 (2.29) 0.2 (0.11)
M5 0.0 (0.00) 0.5 (1.64) 0.5 (0.27)

Material properties for test specimens

Material Properties Values
CFRP material Thickness per layer (mm) 0.6
Ultimate tensile strength (MPa) 1,122
Ultimate tensile strain 1.7%
Tensile modulus of elasticity (GPa) 68.9
Epoxy adhesive for CFRP sheets Tensile strength (MPa) 71.5
Tensile modulus of elasticity (GPa) 1.86
Tensile strain at break 5.25% 5.25%
Glass transition temperature (°C) 85
Thermal decomposition temperature (°C) 345

Physical and mechanical properties of fibers

Fiber type Properties of fibers
Length (mm) Shape Section dimension (mm) Specific gravity Tensile strength (MPa) Modulus of elasticity (GPa)
SF 30 Hooked ends Φ = 0.55 (Circular) 7.85 1,345 200
Polyvinyl alcohol (PVA) 30 straight 0.66 ϕ (Circular) 1.3 900 23
PP 30 straight 0.022 ϕ (Circular) 0.90 550 4
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