Kiwis are more tuned into the impact of failing infrastructure and the effects it has on their lives than ever before. This is not just a New Zealand phenomenon, it is a view shared worldwide says Pete Renshaw, director of business development for Pultron Composites, particularly in countries where there have been ongoing struggles with aging infrastructure, corrosion, and failures caused by the extreme effects of climate change.
With investment from the New Zealand government, says Renshaw to fund a number of critical infrastructure projects, there are clear opportunities for engineers to investigate composite rebar to aid the delivery of lasting, sustainable infrastructure.
Composite rebar is tested and approved with design codes and standards. Pultron Composites manufactures its rebar technology, Mateenbar locally from Gisborne for the Oceania market. It is also manufactured at facilities in Saudi Arabia and USA . In both countries, the cost of corrosion to the economy is staggering. Mateenbar will play a key role in reducing expenditure to transport agencies and governments in these regions.
Steel, concrete and corrosion
Steel rebar and concrete have long been the materials used by engineers for infrastructure.
“In many cases, they are still suitable materials for many buildings or structures but steel rebar is not the best reinforcement when there is corrosion risk,” says Renshaw.
As a case study, New Zealand has 15,000kms of coastline, areas of high geothermal activity, humidity, heavy rainfall in parts, and extreme weather events – it is a corrosive environment. To extend the asset lifecycle of infrastructure, maintenance programmes are put in place to slow and monitor corrosion damage. Maintenance is expensive and only serves to delay rather than eradicate the risk of corrosion damage.
“The knock-on effects of corroding steel reinforcement used in concrete structures runs deep. When steel corrodes it expands causing concrete spalling. Repair and replacement leads to higher cement production – when it comes to carbon emissions, the production of cement is one of the biggest creators,” says Renshaw.
The environmental impact is repeated every time the infrastructure reaches the end-of-life and is rebuilt.
Composite rebar advantages and the environment
“There are a few notable advantages of composite rebar where engineers can deliver cost-effective and sustainable infrastructure solutions. The most important advantage is its corrosion-free properties,” he says.
No maintenance work is needed (labour savings, chemical sealers) and because it is not impacted by corrosion, it requires less concrete coverage. The manufacturing process to make composite rebar is also low energy consuming 70% of the embodied energy of steel.
A research project conducted by the Florida Department of Transport and the University of Miami of 100 year life-cycle study of a 57m x 18m bridge, showed a composite-reinforced bridge reduced global warming potential by 390 tonnes or 26%. Please see the schematic below:
As composite rebar technology has matured prices have dropped considerably, so the initial cost of a structure is comparable with a steel reinforced equivalent.
“It is highly competitive when looking at the whole-of-life cost savings.”
Look to the future
Sustainability in infrastructure has been long talked about but is now at the forefront of how governments, engineering consultants, and asset owners make decisions. Designing infrastructure that achieves the sustainable and energy balance has proven to be better for the economy, environment, and people.
“Just like the Romans, we want our infrastructure to stand the test of time, serve our communities, and have minimal impact on the environment. With composite rebar manufactured here in New Zealand, it’s now up to us to make it happen.”