Mathieu Robert

Behavior of GFRP Reinforcing Bars Subjected to Extreme Temperatures

Corrosion of steel reinforced concrete members has stimulated the research on fiber-reinforced polymers (FRP) to be used as an internal reinforcement for concrete structures. The behavior of glass fiber-reinforced polymer (GFRP) reinforcing bars subjected to extreme temperatures is very critical for applications in North America, especially in Canada. There is a high demand for experimental studies to investigate the thermal stability of strength, along with the ultimate elongation, and modulus of GFRP bars. This paper evaluates the variation of mechanical properties of sand-coated GFRP reinforcing bars subjected to low temperatures (ranging from 0 to −100°C ) and elevated temperatures (ranging from 23 to 315°C ). Tensile, shear and flexural properties are investigated to get an overview of the thermal stability of mechanical properties of GFRP bars subjected to large variations of temperatures. Microstructural analyzes using scanning electronic microscopy (SEM), physical measurements by thermogravimetric...

Temperature as an Accelerating Factor for Long-Term Durability Testing of FRPs: Should There Be Any Limitations?

Fiber-reinforced polymer (FRP) composites are increasingly being used in civil engineering applications due to their numerous advantages. Moreover, some environmental conditions can potentially enhance their long-term durability. Therefore, the study of their long-term behavior is crucial to ensure their durability. To perform durability study in a reasonable time limit, accelerating factor, such as high temperature, is generally used. However, the use of very high temperature of conditioning could amplify the reduction of the properties leading to conservative prediction of long-term properties. The present paper attempts to clarify the effects of high temperatures on the mechanical and barrier properties (moisture absorption) of GFRP’s internal reinforcement, by presenting some experimental results and conclusions of laboratory accelerated studies.

Physical, Mechanical, and Durability Characterization of Preloaded GFRP Reinforcing Bars

This paper presents the physical, mechanical, and durability characterization of glass fiber-reinforced polymer (FRP) (GFRP) bars subjected to different tensile stress levels. FRP bars were first loaded at levels up to 20, 40, 60, and 80% of their ultimate tensile strength (UTS) which could create cracks and microcracks in the FRP bars and affect the long-term durability of the product. Microstructural observations were conducted on preloaded GFRP reinforcing bars to show the deterioration of fiber, matrix, and the fiber/matrix interface. Moisture absorption and tensile properties of loaded bars were also measured to estimate the potential effects of cracks and microcracks on durability-related properties and on short-term mechanical properties, respectively. Loaded bars were also embedded in a moist mortar at elevated temperature to perform accelerated aging. The measured tensile strengths of the loaded bars before and after exposure were considered as a measure of the durability performance of the speci...

Durability Assessment of Glass FRP Solid and Hollow Bars (Rock Bolts) for Application in Ground Control of Jurong Rock Caverns in Singapore

AbstractThis study was conducted to investigate the durability of two types of vinyl-ester/glass fiber-reinforced polymer (GFRP) rock bolts [solid and hollow (tubular) GFRP bars] that were subseque...

Durability in a Salt Solution of Pultruded Composite Materials Used in Structural Sections for Bridge Deck Applications

AbstractThis study addresses the durability of glass fiber–reinforced polymer (GFRP) pultruded structural sections used in bridge-deck applications, namely, a flat plate with T-shaped ribs (R-GFRP) and a corrugated plate (C-GFRP). Standard coupons were aged for up to 224 days at 23, 40, and 55°C in separate baths of 3% salt solutions simulating deicing conditions. The tensile-strength retentions and Young’s moduli were measured periodically. Data were assessed using ANOVA. Microstructure assessments using differential scanning calorimetry, Fourier transform infrared spectroscopy, and scanning electron microscopy were carried out to provide additional assessment of degradation. It was shown that after 224 days, the tensile strength retentions of the R-GFRP and C-GFRP were similar, and that they decreased from 77 to 63% as the temperature increased from 23 to 55°C. The observed reductions were confirmed by micrographs showing some surface cracks and separations between the fibers and the matrix, but results...

Effects of diameter on the durability of glass-fiber-reinforced-polymer (GFRP) bars conditioned in alkaline solution

AbstractCurrent standards do not consider the diameter of glass fiber-reinforced polymer (GFRP) bars used as internal reinforcement in concrete structures to be a factor influencing bar durability....

In Situ Synthesis and Characterization of Silver/Polymer Nanocomposites by Thermal Cationic Polymerization Processes at Room Temperature: Initiating Systems Based on Organosilanes and Starch Nanocrystals

New methods for the preparation of silver nanoparticles/polymer nanocomposite materials by thermal cationic polymerization of ε-caprolactone (ε-CL) or α-pinene oxide (α-PO) at room temperature (RT) and under air were developed. The new initiating systems were based on silanes (Si), starch nanocrystals (StN) and metal salts. Excellent polymerization profiles were revealed. It was shown that silver nanoparticles (Ag(0) NPs) were in situ formed and that the addition of StN improves the polymerization efficiency. The as-synthesized nanocomposite materials contained spherical nanoparticles homogeneously dispersed in the polymer matrices. Polymers and nanoparticles were characterized by gel permeation chromatography (GPC), X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and UV-vis spectroscopy. A coherent picture of the involved chemical mechanisms is presented.

Improvement of the interphase between basalt fibers and vinylester by nano-reinforced post-sizing

Basalt fiber reinforced composites are innovative materials which may be used as an alternative to glass fiber-based composites in civil engineering applications. They exhibit high temperature resistance, corrosion resistance, low cost and excellent mechanical properties. However, according to previous studies, weak interfaces between the basalt fiber and the thermoset resin, such as polyvinylester, could be a problem for the use of basalt fibers reinforced polymers (BFRP) for civil engineering applications. To solve this problem, this study investigates the improvement of properties of basalt fibers coated with silica nano-reinforced epoxy resin. Three types of coatings were tested: epoxy resin, epoxy resin treated with fumed silica, and epoxy resin treated with silane-treated fumed silica. Silica nanoparticles were characterized by Fourier Transform Infrared Spectrometry (FTIR), Thermal Gravimetric Analysis (TGA) and micro-electrophoresis (Zeta-Nanosizer). Basalt fibers were dip-coated in diluted solutions/suspensions of epoxy coatings in acetone and analyzed using Scanning Electron Microscopy (SEM). Basalt fibers/vinylester (VE) composites were then prepared by compression molding. Tensile tests and interlaminar shear tests (ILSS) were performed on the different molded BFRP. Preliminary results show a 5–25 % improvement in mechanical properties depending on the type of coating. The presence of nanosilica at the interface between the basalt fiber and VE matrix leads to a significant enhancement of interlaminar and ultimate tensile strength.

Isolation of cellulose-II nanospheres from flax stems and their physical and morphological properties

In this study, cellulose-II nanospheres (CNS) were extracted from flax fibers and analyzed to understand the crystalline, functional and morphological properties by means of X-ray Diffraction (X-RD), Fourier Transform Infrared (FT-IR) and Scanning Electron Microscopy (SEM). FT-IR and SEM results indicate the effective removal of extractives, lignin and hemicellulose. X-RD results clearly show the transformation from cellulose-I to cellulose-II during the mercerization process. Further, the resulting cellulose fibers were treated with sulfuric acid in order to obtain cellulose nanospheres (CNS). The morphology was measured by SEM, Transmission Electron Microscopy (TEM) and Atomic Force Microscopy (AFM). The size distribution and the surface charge of CNS were investigated by Small-Angle X-ray Scattering (SAXS) and Nanosizer. The results indicate a size distribution of CNS between 20 and 90nm moderately dispersed. Finally, the transversal elastic modulus of CNS-II was determined by using AFM, and results reveal the range varying from 6 to 25GPa.

Degradation characteristics of new bio-resin based-fiber-reinforced polymers for external rehabilitation of structures

Sustainability has recently become a key issue in the design and manufacture of products, due to dwindling oil reserves and increased environmental awareness. Therefore, bio-sourced resins are suggested to be used as an alternative in order to reduce the environmental impact of composite production. This paper presents the mechanical and physico-chemical characterization and the environmental degradation evaluation of furan resin-based glass fiber reinforced polymer (bio-sourced glass fiber reinforced polymer) for structural retrofitting applications in comparison with those of an equivalent thermoset-based glass fiber reinforced polymer (petro-sourced glass fiber reinforced polymer). Epoxy resin was used as a representative for petroleum-derived synthetic thermoset. To conduct this preliminary study, the following steps were taken: (1) prepare composites made from furan and epoxy resins, (2) characterize the mechanical and physico-chemical properties of the composites, (3) study the moisture absorption, and finally, (4) evaluate the degradation of both composites when subjected to alkaline solutions which was simulated to leached concrete pore solution. The experimental results show that the use of furan resin as polymer matrix in glass fiber reinforced polymer leads to an increase in the moisture absorption and a significant decrease in the degradation in alkaline solution.