For many years, Concrete has remained the favourite choice in civil systems due to a wide range of characteristics. Similarly to FRP,concrete is a composite material composed of a fine and coarse aggregate bonded together with a fluid cement that  hardens over time.The aggregate is mixed with water and the dry cement, and the mixture forms a slurry which is poured and moulded into a variety of shapes. Concrete has a high compression strength, but a low tensile strength, but is able to be reinforced with steel.

But through recent years, Fibre reinforced Polymers have becomes a material being more and more preferred due to several characteristics.

The lightweight property of FRP gives it several beneficial aspects when considered against concrete. The first benefit of lightweight materials is the reduced installation and transport costs. With rising transportation costs and construction costs, a quick and simple installation can save a drastic amount of money. FRP materials are also much easier for installation as the processes are simple and this ease of manufacture on site allows for simple tooling to create and adjust parts on site. When considering bridge constructions, specifically bridge deck panels, FRP are easier in transport, and faster to install. Furthermore concrete requires 28 days to cure and precast concrete panels require heavy duty equipment, again providing further savings. FRP also require much less substructure (ground connections) and much less superstructure requiring a lower overall cost than concrete.

Colouring is another great example of changes. Concrete cannot be changes in colour without much difficulty and specialty products. FRP on the other hand can be easily pigmented and colour at any stage of manufacture. This allows FRP systems to blend into any environment and can provide more aesthetic options.

A major point of the differences between the two systems is variation in corrosion and decay of both systems. Concrete has a lot of weaknesses which in certain applications can become dangers to concrete structures. When concrete is exposed to a range of chemicals or water, issues may arise. Concrete is more susceptible to corrosion and decay, and is not recommended in systems that are exposed to salt water such as coastal areas. FRP is highly chemical resistant. It is highly resistant to water, salt and chemicals, hot and cold temperature extremes ad variables found in coastal environments. At PROTECTOR, we use a smooth interior corrosion layer and external water penetration barrier to ensure our systems are chemically resistant and watertight.  It is this that has led FRP to become favourable in construction and civil exercises, with the outer layers being and FRP material to be resistance to weathering and corrosion. Furthermore FRP is considered an extremely water tight system, with it concrete being porous and can form leaks. Hence in water effluent systems, FRP is a much more preferred materials

As a further point, concrete has a lifespan on anywhere between 15 to 50 years, depending on the environment – in environments with salt and coastal weather patterns even less! FRP however has an expected lifespan of over 75 years, range to up to 150 years. PROTECTOR’s products are designed with a 6:1 design factor of safety and designed for the longest life possible, aiming for 150 year lifespan for all products. The lifespan alone will dramatically reduce lifetime costs, with less replacement of systems and maintenance than for FRP systems. FRP systems also have the advantage of having no degradation over time, with concrete having decay and damage over time causing sooner replacement when considered against FRP.

In fabrication concrete tanks are built in sections requiring field assembly. Each joint is a potential leak even with additional sealants. Fiberglass tanks are monolithic. FRP is easier to assemble, with even the possibility of fabrication and manufacture on site with simple tools, or more commonly having a preassembled system if possible. Furthermore in terms of maintenance fibreglass is much easier to clean and keep clean, extending the life of the interior parts such as pumping systems and valves.

When we consider them as systems built for underground tanks, similar to what Protector does with its stormwater treatment systems, we see some major disparity.

FRP vs Concrete in Underground Tank and Water Treatment Systems
PROPERTY FRP CONCRETE
Water Resistance and Leakages FRP systems are water tight and Protectors systems have an external resin rich water tight penetration barrier. Concrete is a porous material allowing water to penetrate the surface. Even with sealants concrete can leak
Structural strength Strong material in terms of strength, will not degrade over time Degrades over time, although initial strength of system is greater
Lifespan 75 year guaranteed lifetime, up to 150 years max Between 15-50 year expected lifespan
Fabrication FRP systems can be made as a whole, monolithic system with no leaks usually coming pre-assembled. Concrete must be built as separate sections for ease of delivery and installation, hence joints provides weaknesses  even with additional sealants. More complex systems are required in manufacture of concrete assemblies.
Expansion and contraction Fibre glass has a low coefficient of expansion under heat and weather conditions. Concrete expands and contracts regularly with temperate cause cracks to appear and corrosion.
Corrosion due to Microbial Induced Corrosion Resistance to all chemical corrosion types Hydrogen sulphide creates sulphuric acid when in underground water systems, a common cause of deterioration of concrete.
Bacteria resistance FRP products at Protector are manufactured with smooth interior resistant layers and exterior waterproof layers making it perfect environment to combat bacteria and algae accumulation. Not suitable
Oxidation resistance Is not effected by Oxidation Concrete often uses steel rebar for reinforcement and the rebar is susceptible to rust from water permeating the surface.
Weight Lightweight requiring smaller crane systems for loading and offloading.

Weighs approx. 1400kg per cubic m

Concrete is a heavier system. Weights approx 2400kg per cub metre.
Installation Fiberglass tanks can be transported on a single truck and are delivered to the site as a finished product making installation easier and faster Requires step by step installation on site as concrete systems have to be poured and set. Requires more transportation increasing time and expenses.
Maintenance and Repairs Additional appurtenances can be installed directly to the FRP tank at the job site and even after burial. Fiberglass does not require resurfacing for the life of the product. Fiberglass is easier to clean and keep clean which extends the life of pumps and filtering equipment. Much more difficult in all stages of maintenance to deal with, more difficult to clean and maintain requiring higher frequency and increased cost over the life of the system.

Written by Nathan D. Raco, in partnership with Protector Stormwater management Solutions

http://www.protector.com.au