• Each bar demonstrates a uniquesignature of existing crack/void patterncharacterized by a combination ofdisconnected or continuous voids atdifferent locations of the cross section.

• The diameter of individual glass fibersare measured to be 20-25 μm andproper distribution of the resin aroundthe fibers is observed for all the bartypes.

• The results of this study can be used asa benchmark for microstructure ofcommercially available pristine GFRPbars and serve as a base for monitoringpossible changes after conditioning orfield use.

Microstructural Investigation of Commercially Available Pristine Composite Bars for Concrete ReinforcementO. Gooranorimi a, W. Suaris a, E. Dauer b, A. Nanni a

a Department of Civil, Architectural & Environmental Engineering, University of Miamib Department of Biomedical Engineering, University of Miami

Different microstructural signatures

References• Micelli F.; Nanni A.; Durability of FRP Rods for Concrete Structures. Journal of Construction and Building Materials 2004; 18: 491-503• Mukherji S.; Arwikar S. J.; Performance of Glass Fiber-Reinforced Polymer Reinforcing Bars in Tropical Environments-Part II:

Microstructural Test. ACI Structural Journal 2005; 102: 816-822• Mufti A. et al.; Durability of GFRP Composite Rods. Concrete International 2007; 29: 37-42

AcknowledgementsThe financial support from the listed organizations is gratefully acknowledged: a) NSF Industry/University CooperativeResearch Center (I/UCRC) for the Integration of Composites into Infrastructure (CICI); and, b) University TransportationCenter on Research on Concrete Applications for Sustainable Transportation (RE-CAST)

Bar-A presents a continuous long crack atthe edge and a large void at the center ofthe bar. The rest of cross section does notshow any voids/cracks and the resinproperly impregnates the fibers.

Bar-B demonstrates a continuous crackalong the edge accompanied bydisconnected voids at the vicinity of edges;while the central portion of the sectionpresents no voids/cracks.

Bar-C presents both connected cracks anddisconnected voids in the cross-sectionincluding the central portion and at theedges.

Bar-D demonstrates disconnected voidpatterns in the cross-section including boththe central portion and edges. The numberof voids reduces in the central part.

Main Advantages of GFRP Composites Corrosion resistant properties Strength to weight ratio No conductivity Cost comparable to epoxy coated steel

• Employing fiber reinforced polymer (FRP) materials leads to reduction of repair, rehabilitation and long-term maintenance costs of structures.

• Glass FRP (GFRP) composites are emerging as an alternative for steel in reinforced concrete structures,especially in aggressive environments such as bridge decks.

• Considering lack of a GFRP microstructure knowledge in the literature, the main purpose ofthis study is to provide documentation of GFRP microstructure.

• Scanning electron microscopy (SEM) imaging is performed on cross section views of GFRPbars from four manufacturers with the following surface characteristics: (i) Ribbed (Type-A);(ii) Fine sand coated (Type-B); (iii) Double twisted E-glass fiber coated (Type-C); & (iv) Coarsesand coated (Type-D)

Different manufacturing methods/parameters

Microstructural characteristics are crucial in understanding andpredicting GFRP behavior under different environments and states ofstress.

Results

Motivation

Conclusions

Purpose

SEM images of bar-A: Crack at the edge (Left); void at the center (Middle); & fully impregnated portion (Right)

SEM images of bar-B: Crack at the edge (Left); disconnected voids: close to edge (Middle) & central portion (Right)

SEM images of bar-C: Continuous and disconnected voids: close to edge (Left); central portion (Middle); & zoomed crack at the central portion (Right)

SEM images of bar-D: Disconnected voids close to edge (Left); Disconnected voids at the central portion (Middle); & zoomed image of disconnected voids (Right)

• Imaging is conducted at different magnification levels and captures the: a) Existing crack/voidpatterns in the matrix; b) fiber/matrix interface; and c) fiber distribution in the matrix.

• Panorama images of the entire cross section are provided to give a proper comparisonbetween the bars.

Polished and gold coted GFRP sample, from left: A, B, C and D typesSample Preparation

Coarse Polishing Fine Polishing Drying & Cleaning Gold Coating

Panorama images of bar type : A (top-left), B (top-right), C (bottom-left) & D (bottom-right)

GFRP reinforcements implemented in a pedestrian bridge at Coral Gables campus of University of Miami

• All the samples have a diameter of 0.5 (in). (#4 GFRP bars)