April 30, 1998

CARBON FIBER REINFORCED PLASTIC GRIDS FOR CONCRETE REINFORCEMENT

by:

Charles E. Bakis, Associate Professor

Department of Engineering Science and Mechanics

The Pennsylvania State University

ABSTRACT

Fiber reinforced plastic (FRP) composite materials are attracting interest for their potential as high-strength, durable replacements of steel reinforcement in concrete structures. The durability advantage versus steel is especially apparent in chloride-rich environments such as near the ocean or where de-icing agents are used. Considering the time savings involved in construction using lightweight, pre-formed two-dimensional FRP reinforcements, FRP grids also have a high potential for near-term implementation in the field.

Well-designed FRP grids must have good tensile strength for strength requirements as well as good interlocking rigidity and strength for strength at the joints for serviceability requirements. In this investigation, novel types of carbon fiber reinforced vinylester orthogonal grids for concrete reinforcement were designed, manufactured, and evaluated with mechanical tests. The aim of the investigation was to determine the effect of fiber architecture in the joint region on the stand-alone tensile strength and stiffness of the grid and on the direct tensile pull-out (bond) behavior of the grid in concrete. Variable percentages of fibers were placed cross-plied through the joint and curving at right angles at the joint. Greater fiber continuity between the longitudinal and transverse grid elements improved bond rigidity at the expense of through-joint tensile properties. This result suggests that optimal properties might be obtained with a combination of cross-plied and curved fibers. Slip during pull-out was governed by failure processes in the FRP rather than in the concrete.