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Strengthening of fiber-reinforced geopolymer concrete after high-temperature exposure using CFRP sheets

Mohammad Y. Khawaji

Mohammad Y. Khawaji

Department of Civil Engineering, College of Engineering, King Saud University,Riyadh, Saudi Arabia
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Khawaji, Mohammad Y.
 e 
Aref A. Abadel

Aref A. Abadel

Department of Civil Engineering, College of Engineering, King Saud University,Riyadh, Saudi Arabia
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Abadel, Aref A.
  
03 set 2025
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Categoria dell'articolo: Research Article
Pubblicato online: 03 set 2025
Pagine: 31 - 49
Ricevuto: 20 lug 2025
Accettato: 22 ago 2025
DOI: https://doi.org/10.2478/msp-2025-0028
Parole chiave
© 2025 Mohammad Y. Khawaji and Aref A. Abadel, published by Sciendo
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Figure 1

The MK and FA particle sizes used in this study [42].
The MK and FA particle sizes used in this study [42].

Figure 2

Fiber types used in this study: (a) SF and (b) PVA.
Fiber types used in this study: (a) SF and (b) PVA.

Figure 3

GPC specimens after casting in molds.
GPC specimens after casting in molds.

Figure 4

GPC specimens after casting in molds.
GPC specimens after casting in molds.

Figure 5

The heating curve used in the current study.
The heating curve used in the current study.

Figure 6

Test setup.
Test setup.

Figure 7

Failure modes of all GPC specimens.
Failure modes of all GPC specimens.

Figure 8

Compressive strength of all GPC specimens.
Compressive strength of all GPC specimens.

Figure 9

Stress–strain curves: (a) All specimens; (b) unstrengthened specimens exposed to 25°C; (c) unstrengthened specimens exposed to 500°C; (d) strengthened specimens exposed to 25°C; and (e) strengthened specimens exposed to 500°C.
Stress–strain curves: (a) All specimens; (b) unstrengthened specimens exposed to 25°C; (c) unstrengthened specimens exposed to 500°C; (d) strengthened specimens exposed to 25°C; and (e) strengthened specimens exposed to 500°C.

Figure 10

Modulus of elasticity of all GPC specimens.
Modulus of elasticity of all GPC specimens.

Summary of test results_

Specimens Compressive strength (MPa) Relative difference* Modulus of elasticity (MPa) Relative difference*
GPC0-25 46.0 — 22666.4 —
GPC0-500 15.4 −66.7% 2338.7 −89.7%
GPC0-S-25 70.9 +54.0% 30930.2 +36.5%
GPC0-S-500 66.6 +44.7% 4867.7 −78.5%
GPCS-25 47.2 — 20649.6 —
GPCS-500 20.6 −56.4% 1523.2 −92.6%
GPCS-S-25 91.5 +93.9% 21794.9 +5.5%
GPCS-S-500 85.3 +80.9% 3225.4 −84.4%
GPCP-25 36.0 — 17764.6 —
GPCP-500 10.1 −72.0% 1328.2 −92.5%
GPCP-S-25 77.4 +115.1% 19710.1 +11.0%
GPCP-S-500 73.9 +105.2% 3273.8 −81.6%

FRGPC mix proportions in kg/m3_

Material FRGPC0 mix FRGPC1 mix FRGPC2 mix
MK 285 285 285
FA 65 65 65
White sand (max size: 2 mm) 419 419 419
SF — 78.5 —
PVA — — 13
Alkaline solutions Na2SiO3 197 197 197
NaOH 110 110 110
Coarse aggregate (Maximum size of 10 mm) 1,272 1,272 1,272
(Maximum size of 4.75 mm) 180 180 180

CFRP sheet and epoxy adhesive characteristics_

Material Property Value Notes
Epoxy adhesive Tensile strength 71.5 MPa Given by the manufacturer
Tensile elastic modulus 1.86 GPa
Tensile strain at break 5.25%
CFRP sheet Thickness 0.6 mm Experimental values
Ultimate tensile strength 1,122 MPa
Tensile elastic modulus 68.9 GPa

Test specimens_

Concrete mix Specimen ID Fiber type Exposure to temperature (°C) Strengthening No. of specimens
FRGPC0 GPC0-25 — 25 — 3
GPC0-500 500 3
GPC0-S-25 25 CFRP 3
GPC0-S-500 500 3
FRGPC1 GPCS-25 SF 25 — 3
GPCS-500 500 3
GPCS-S-25 25 CFRP 3
GPCS-S-500 500 3
FRGPC2 GPCP-25 PVA 25 — 3
GPCP-500 500 3
GPCP-S-25 25 CFRP 3
GPCP-S-500 500 3
Total no. of specimens 36

MK’s chemical analysis [42]_

Composition SiO2 Al2O3 Fe2O3 TiO2 CaO SO3 K2O Na2O MgO P2O5 Others
Value (%) 50.995 42.631 2.114 1.713 1.287 0.439 0.337 0.284 0.127 0.051 0.022
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