International Concrete Abstracts Portal

Substitution of conventional steel reinforcing rebars with Glass Fiber Reinforced Polymer (GFRP) rebars in Continuously Reinforced Concrete Pavement (CRCP) gives solutions to the problems caused by corrosion of reinforcement. Concrete volume change, due to shrinkage and temperature variations is known to cause crack development in CRCP. In this study, the stress levels in concrete and GFRP rebars and the crack widths at various crack spacings are predicted using numerical methods. The results reveal that using GFRP rebars as reinforcement in CRCP reduces the tensile stress in concrete. The bond-slip between concrete and reinforcement and the friction from the pavement's subbase have important effects on the development of the reinforcement's stresses and the crack widths. The design of a GFRP-reinforced CRCP to be constructed during this year is proposed. The behavior of the CRCP due to concrete shrinkage and temperature variation is predicted. The stress levels in the GFRP reinforcement, the crack width and the crack spacing of the proposed pavement are shown to be within the design requirements.

Aspects of the design and installation of a novel carbon fibre reinforced polymer (CFRP) prestressed high strength concrete lighting column (Carbolith®) are presented. The tapered cylindrical columns have a nominal height of 8 m and contain an opening above the foundation to allow for the insertion of the lamp fuse box. The bending/torsion behaviour of a total of five full-scale prototype columns was tested in accordance with the relevant European standards (EN). In the experimental programme, the location of the fuse box opening relative to the loading direction was varied. All five poles fulfilled the EN serviceability and ultimate limit state requirements for lighting columns in pedestrian and/or low speed lightly trafficked areas. This successful outcome has lead to the first field application of the CFRP prestressed concrete lighting columns.

This paper describes the use of Carbon Fiber Reinforced Polymer, CFRP, tendons and rods for prestressing concrete highway bridges completed in 1993 and 1997. Due to the lack of design codes, the paper presents briefly the research work undertaken before the final design of the two bridges. The first bridge is a 75 ft. (23.85 m) span skew bridge, which consists of bulb-tee pre-tensioned girders made continuous with posttensioned steel strands. Four girders were pre-tensioned by two types of CFRP. The second bridge is 541 ft. (165 m) long and consists of five simply supported span girders, 110 ft. (33 m) long. Four girders were prestressed by two different types of CFRP using straight and draped tendons. The AASHTO girders were also reinforced with CFRP stirrups. A portion of the deck slab is reinforced by CFRP reinforcement. Design considerations, safety features and construction of each bridge are described briefly. The paper summarizes also the results of monitoring the behavior of each bridge. The experience gained from these two bridges provides valuable information for the development of the design guidelines, currently under consideration by the ACI Committee 440, Fiber Reinforced Polymer.

The Naval Facilities Engineering Service Center (NFESC) investigated a hull concept for a proposed floating pier with a design life of 100 years. The hull concept consists of bidirectional post-tensioned lightweight concrete panels reinforced with carbon fiber reinforced polymer (CFRP) grids for crack control and toughness. CFRP grid reinforcement could be a potential durable alternative to using stainless steel reinforcement and could be cost-effective for marine application, if the use of CFRP reinforcement justifies minimizing the concrete cover and allowing minor cracking during service load. The paper discusses construction and cost considerations developed during production of 13 testing specimens of such a panel concept. Though the panel concept seems feasible, the NFESC deferred the concept for the time being due to the high cost of CFRP, the difficulties in detailing panel connections using CFRP reinforcement, and the unknowns related to the durability of CFRP reinforcement in cracked concrete exposed to marine environment.

Fiber reinforced polymer (FRP) materials can be used in concrete infrastructure elements to achieve short-term and long-term construction and performance goals that cannot be met with traditional steel reinforcement. Like other states, Texas is faced with materials-based transportation infrastructure challenges including: deterioration of concrete due to the corrosion of steel reinforcement, bridge girders damaged by vehicle impacts, concrete bridges that have no visual signs of distress but are load-posted or otherwise deficient in load rating, girders and bent caps that have inadequate shear reinforcement by current standards or that exhibit service cracking, and even a need to provide reinforcement that does not interfere with vehicle imaging loops requiring magnetic/electrical isolation near turnpike toll plazas. This paper reports on Texas transportation infrastructure construction and maintenance projects where FRP materials have been implemented as a means to meet each of these challenges. Included herein are descriptions of selected Texas Department of Transportation (TxDOT) construction and maintenance projects involving concrete internally and externally reinforced by FRP materials. These projects are either completed or will soon go to contract. Most of these projects have been carried out on a trial or experimental basis but they serve to provide a brief glimpse into the probable future of FRP reinforcement in Texas transportation projects.