Reinforced concrete, Fiber

The flexural behavior of rectangular concrete beams strengthened with externally bonded Carbon Fiber Reinforced Plastic (CFRP) laminates was studied by varying the number of plates bonded to their bottom tensile face. The increases in strength and stiffness of the beams provided by the bonded plates, over control beam without CFRP plates, were evaluated. Failure loads of the beams were determined by the ACI strain compatibility method using a FORTRAN software developed for this purpose. The predicted collapsed load agrees reasonably well with the actual failure load. Precracked solid and voided slab bridge models retrofitted with varying number of CFRP laminates were used to evaluate their contribution to the flexural resistance. The increases in strength and stiffness of the retrofitted slabs were based on the deflections, strains and crack patterns at ultimate load. Theoretical analyses to predict the load-deflection behavior of the precracked sections were performed using PCFRAME software. The predicted values agree reasonably well with the experimental results.

The feasibility studies on the use of non-metallic continuous fiber reinforcement in reinforced and prestressed concrete structures are presented herein. Experimental results from studies on relaxation, bond and transfer length of Carbon Fiber Composite Cables (CFCC) are presented followed by results of flexural load tests on concrete beams reinforced and prestressed with CFCC. Durability of the CFCC is another prime concern, and hence part of the study also focuses on establishing the durability of the CFCC exposed to aggressive environments like alkali solution and sea water. The basic mechanics that govern the structural behavior of the beams, provide important insight into the potential that CFCC has to offer.

This thesis presents the experimental and analytical investigation of fiber (steel and Kevlar) reinforced concrete (FRC) to determine its fracture mechanic properties especially the J-integral. The freeze-thaw durability of fiber reinforced and air-entrained concrete is also investigated. The fiber reinforced concretes were found to have a much greater flexural strength and toughness compared to plain concrete. The compressive strength was found to decrease with the addition of fibers and air-entrainment. In all cases the addition of 1.0% or more fibers prevented catastrophic failures. The mixing and setting of FRC requires a rigorous procedure which must be followed to achieve a homogeneous matrix.

Durability of concrete bridge decks reinforced with conventional structural steel is a major concern in aggressive environments. To address this problem, there have been efforts, in recent years, to develop and evaluate alternatives to conventional steel. One alternative is fiber reinforced polymer (FRP) composite reinforcement. FRP composites have been used successfully in many industrial applications. This thesis investigates short-term mechanical properties of FRP rebars as reinforcement for concrete bridge decks and discusses results of extensive laboratory tests. Four test methods (tension, flexure, shear and bond) are developed and test protocols are proposed for adoption by AASHTO.

This investigation addresses the evaluation of the increase in structural integrity of concrete wall panels by the addition of polypropylene fibers. The test methodology used was the evaluation of flexural (simply-supported and cantilever), shear (in-plane and punching), and impact behavior. The concrete panels comprised sets with (i) regular reinforcement (ACI code based), (ii) Reinforced concrete panels: 0.2% fibers with minimum ACI reinforcement, FRC 2, (iii) 0.3% fibers without reinforcement, FRC 3, and (iv) plain beams without reinforcement. The instrumentation consisted of deflection and electrical strain gages, a slope indicator for slope testing, and an oscilloscope with a camera attachment for monitoring load and energy traces in impact testing. The normalized (adjusted for concrete strength variations) ultimate load and energy values were compared. The findings indicated enhancement of ductility and shear strength for the fiber reinforced specimens, which are very desirable for sudden and impact loading conditions associated with hurricane-type loading.

An experimental study was conducted on the strength and toughness characteristics of concrete made from recycled aggregate, cement and fly ash reinforced with reclaimed high density polyethylene plastic (HDPE) fibers. The objectives of the investigation were: (1) to evaluate the performance of a sustainable concrete containing up to 90% recycled materials; (2) to determine the variation of strength and toughness with a Fiber Factor incorporating length, width and amount of HDPE fibers; (3) to identify the best performing mix design based on tensile strength and toughness and (4) to provide some guidelines for the use of this sustainable composite in Civil Engineering construction. The results showed that the HDPE fiber reinforcements did not improve the compressive strength of the mixture. However, HDPE fibers improved the ductility and toughness which may be beneficial for structural and pavement applications.