In this article we discuss and compare features and benefits of aluminium versus steel trench shields.

If your project requires sheet piling, then neither of these options are suitable.

When considering which shields are best suited for your application you need to focus on:

Weight and Portability

Steel trench shields are significantly heavier than their aluminium counterparts, making them harder to transport and manoeuvre on site. Aluminium being lightweight reduces the physical strain on workers and allows for faster setup and dismantle times. This also allows you to use a smaller digger to lift the shields into place, which can be particularly helpful in the confines of an urban site.

Corrosion Resistance

Aluminium trench shields don’t rust like steel ones. This extends the lifespan of the shields and reduces maintenance costs, potentially allowing the shields to last for decades.

Strength-to-Weight Ratio

It is not the material a shield is made from that makes them strong, it is the design. Commonly people believe steel shields are stronger than aluminium shields because of the material they are made from. However, some aluminium shields are purposefully designed, giving them a very high strength-to-weight ratio, providing excellent structural integrity while minimising weight as aluminium is a lighter material than steel.

Cost-Effectiveness

Steel trench shields can be slightly less expensive than aluminium shields initially, however the longer lifespan and lower maintenance costs make aluminium a more cost-effective option in the long run.

Environmental Benefits

For this section we compare the environmental impacts of using a 5T digger that can lift aluminium shields compared to a 10T digger that can lift steel shields (calculations based on common 3.6m shields).

1.       Fuel Consumption & Emissions

5-tonne digger: Typically uses 5-10L of diesel per hour, emitting 13-26 kg of CO₂ per hour.

10-tonne digger: Uses 15-20L of diesel per hour, emitting 39-52 kg of CO₂ per hour.

Impact: A 10-tonne digger emits 2-4 times more CO₂ per hour than a 5-tonne digger, significantly increasing its carbon footprint.

2.       Ground Impact & Soil Disturbance

5-tonne digger: Lighter, causing less soil compaction and damage to vegetation.

10-tonne digger: Heavier, leading to more compaction and potential disruption to drainage and soil health.

Impact: The 5-tonne digger is less damaging in sensitive environments or soft ground conditions.

3.       Efficiency & Overall Impact

10-tonne digger moves more material per hour, potentially reducing total operating hours.

5-tonne digger might need longer operation time to complete the same job, potentially negating its lower hourly emissions.

Impact: The 10-tonne digger may be more efficient for large-scale projects, while the 5-tonne digger is preferable for smaller or environmentally sensitive sites.

Certification

Steel shields typically require re-certification after 10 years from manufacture. This often is an expensive exercise due to rust/corrosion over that time and they often cannot be recertified and need to be scrapped. Aluminium trench shields do not need recertification after 10 years and if cared for can last significantly longer.

Flexibility

Shield sets can be transported using a 4.8 meter braked tandem light trailer (which is the biggest size trailer you can typically hire). Its weight limit is 3500kg, so it would be able to carry one 5m steel shield weighing 3311kg, or two 1700kg aluminium shields weighing a total of 3,400kg. The lighter weight of an aluminium shields makes freight options more flexible and cheaper as it is cheaper to hire a trailer than a truck to move multiple shields.

Long term effects of damage

Both steel shields and aluminium can be punctured by digger bucket teeth. While steel may resist this slightly more, when steel is punctured it causes a potential rust/corrosion problem that can prevent shields being recertified. By comparison aluminium can be easily repaired with no permanent corrosion issue.

Weight Comparisons – (kg)

Based on weights from a popular USA manufacturer of steel shields when compared to a popular aluminium option.

Steel 5.0m Shield Set                            3311kg

Aluminium 5.0m Shield Set               1700kg to 2200kg – depending on the shield design

Steel 3.6m Shield Set                            1544kg

Aluminium 3.6m Shield Set               978kg               

Strength Comparisons (kPa)

Steel 5.0m Shield Set                           67kPa

Aluminium 5.0m Shield Set               55 to 70 kPa – Depending on the shield design

Steel 3.6m Shield Set                            39kPa

Aluminium 3.6m Shield Set               43kPa

Cost in use comparisons

This is based on needing a 5T digger for aluminium 3.6m shields weighing 978kg and a 10T digger for steel 3.6m shields weighing 1544kg.

Aluminium 3.6m – 5T digger

Fuel consumption: 6-10L per hour for 8 hours/day at $2.50/L = $120-$200 per day

Digger hire: $150-$250 per day

Overall estimated cost per day: $270 - $450

Steel 3.6m – 10T digger

Fuel consumption: ~15-20L per hour for 8 hours/day at $2.50/L = $300-$400 per day

Digger hire: $250-$450 per day

Overall estimated cost per day: $550 - $850

Overall savings in using lighter aluminium shields and 5T digger = $280 - $400 per day

Excluding weekends and public holidays the potential savings of using aluminium shields over the course of a year adds up to between $69,720 and $99,600.

Conclusion

Overall, aluminium trench shields offer many advantages over steel shields, including reduced weight, corrosion resistance, and improved strength-to-weight ratio. While they may be slightly more expensive initially, their long-term benefits make them a more cost-effective and environmentally friendly option.

Disclaimer: This information is from our research & may differ from your actual numbers depending on the shield's type, size, design and manufacture. All aluminium facts are taken from our shields.