Although many of us may think that concrete structures such as bridges have been maintenance-free for decades, they actually need to be maintained every five years. However, an experimental new type of rebar may completely change this.
The problem with existing concrete structures is that steel bars are embedded in them for support. Over time, these rusts take up more space than the original uncorroded rebar. As a result, rusted steel rushes towards the surrounding concrete, causing it to spall, a process where the concrete cracks and falls off the main structure.
According to Dr Mahbube Subhani, a lecturer in civil engineering at Deakin University in Australia, reinforced concrete structures usually require maintenance every five years or so and major repairs every 20 years. This situation prompted Dr. Subhani and Dr. Kazem Ghabraie to produce a new non-rusting rebar made of carbon fiber and glass fiber reinforced polymers.
The material is reported to be stronger than rebar made from ordinary steel and weighs only one-fifth the weight of reinforced steel rebar. In addition, it requires only a quarter of the energy to produce. The rebar will soon be used in pedestrian bridge construction in Geelong, Australia. Researchers believe that once the bridge is completed, it is expected to be maintenance-free for 100 years of use.
In addition, instead of cement, the concrete used for bridges will contain fly ash derived from coal combustion-cement production is one of the main sources of artificial carbon dioxide emissions. Deakin researchers have previously developed environmentally friendly concrete in which waste glass is used as aggregate.
"We replaced steel bars that are commonly used in reinforced concrete with steel bars and fiberglass-reinforced polymers," said Subhani. "This bridge does not require any maintenance throughout its design life."