Reinforced concrete is widespread used building material for the construction of facilities and structures.
Steel rebar has been included in concrete as complement to its very limited tensile strength.
It is an effective and cost-efficient reinforcement. Yet, insufficient concrete cover, poor design or workmanship, and presence of large amounts of aggressive agents and environmental factors lead to cracking of the concrete and corrosion of the steel rebar.
There have been many studies on this issue, and the interest in FRP (Fibre Reinforced Polymer) has arisen as potential alternative for steel.
In 2009, researcher in University of Miami, through its National Science Foundation (NSF) Industry/University Cooperative Research Centre “Repair of Buildings and Bridges with Composites” (RB2C), performed the first-ever tests of full-scale concrete columns internally reinforced with glass fibre reinforced polymer bars.
The new study demonstrates that the behaviour of FRP reinforce concrete columns was very similar to that of the conventional steel rebar.
In 2010, researchers in Northern Ireland report promising results from a demonstration project that used rods made with basalt fibres to reinforce a 22-meter-long concrete-deck section of a replacement bridge in County Fermanagh.
The method takes into account the arching behaviour within restrained slabs, which enhances load capacity beyond that predicted using conventional flexural theory.
The 10.9-m-wide deck was cast in place over four longitudinal, precast-concrete, flat-bottomed U-shaped beams. The 16-centimeter-thick deck typically spans 1.6 m between the beams.
After the bridge’s structural complete the deck was tested by applying a simulated wheel load up to 40 tonnes – nearly three times the European Union’s maximum vehicle axle load.
The tests recorded maximum strains of the basalt fibre reinforced polymer rebar as – very, very low – at 11.7% of the maximum capacity.
The BFRP-reinforced deck deflected around 0.8 millimetres, which was less than half the deflection recorded on the equivalent steel-reinforced section.
The problems of steel corrosion are avoided with the use of FRPs because FRP materials are non-metallic and noncorrosive.
FRP materials also demonstrate several properties including high tensile strength that make them suitable for the use as structural reinforcement.
Aramid fibre reinforced polymer (AFRP), carbon fibre reinforced polymer (CFRP), and glass fibre reinforced polymer (GFRP) rods are the commercially available products for the construction industry.
FRP can be a suitable alternative to steel reinforcing in architectural concrete – cast stone, architectural cladding, balusters, column facades, window lentils, architectural precast elements, hand railing, and statuary and fountains.
FRP can be incorporated where concrete exposed to de-icing salts in such as bridge decks, railroad grade crossings, median barriers, parking garage elements, and salt storage facilities.
It also a good solution corrosion of the steel rebar where concrete exposed to marine salts in as in seawalls, water breaks, buildings & structures near waterfront, aquaculture operations, and floating marine docks.
It also the best candidate in substituting steel rebar where concrete used near electromagnetic equipment such as MRI rooms in hospitals, airport radio & compass calibration pads, and concrete near high voltage cables, transformers and substations.
Even though the initial costs of FRP rebar is higher than standard steel rebar and is roughly comparable to epoxy-coated steel rebar, but when considered its lifecycle cost, it can be reasonably economical.
For all these reasons and more, FRP rebar has slowly begun to gain share in the civil engineering market.
Source : Aggregate Research; Concrete Construction; Composites World; Emerging Construction Technology, Purdue University, Indiana, USA; University of Miami; Marshall Industries Composites, Inc. Website: http://www.c-bar.com; Hughes Brothers, Inc. Website: http://www.hughesbros.com; Griffiths, J. R. “Plastic Highway Bridges”, Cambridge Scientific Abstracts, 2000; Benmokrane et al. “Mechanical and Bond Properties of New Generation of ISOROD CFRP Reinforcing Bars for Concrete Structures”, technical progress report, 2001, ISIS Canada; Market Development Alliance of the FRP Composite Industry (MDA) Website: http://www.MDAcomposites.org and Gremel, D. “FRP Rebar – A State of the Industry Report Manufacturing, Construction, Economics and Marketing”, Proceedings of the Workshop Composites in Construction: A Reality, 20-21 Jul., 2001, Anacapri, Italy.
(this article written for 1BINA.my)
- UHPFRC – Giving Concrete Infrastructure a Second Life
- New Imaging Technique Makes Quick Check-Up for Bridges