case study
carbon steel reinforcement, they can disrupt its protective passive layer and initiate corrosion, including localised pitting. Corrosion can reduce the steel’s effective cross- section and compromise its performance. Where steel is concealed inside concrete, detecting deterioration early can be challenging. The real cost of “cheap” infrastructure Carbon steel remains the default reinforcement choice in many projects, in part because its initial material cost is lower. In coastal areas, structures exposed to de-icing salts and other aggressive environments, however, the purchase price is only one part of the calculation. Maintenance, repair, access and disruption over a structure’s life also carry significant costs. To illustrate the difference, the Sassda life-cycle cost calculator was used to model a hypothetical 100-year infrastructure project requiring 100 tonnes of reinforcement The example applies a 3% public-sector discount rate to future maintenance costs. Its results depend on the assumptions used, but they show how repair costs can change the comparison over time.
What the model shows The example assumes duplex stainless steel, such as Grade 2205, at $3 500 per tonne, compared with $1 000 per tonne for carbon steel. The stainless steel option carries a higher initial material cost. Once labour, civil works and concrete are included, the model puts the difference in total project cost at $250 000: $850 000 for the stainless steel option against $600,000 for carbon steel. In the model, a major carbon steel repair in year 35 costs $650 000. Discounted to present value, that repair is $230 999. At that point,
Cost Component
Carbon Steel Reinforcement
Duplex Stainless Steel (DX 2205)
Material Unit Cost
$1 000 /tonne
$3 500 /tonne
Total Rebar Cost (100 tonnes)
$1 000
$350 00
Initial Placement (Concrete & Labour)
$500 00
$500 00
Initial CAPEX Total
$600 00
$850 00
Year 35 Repair Cost (Direct + Traffic)
$650 00
$0
Year 70 Repair Cost(Direct + Traffic)
$650 00
$0
NPV of Future Maintenance
$313 092
$0
Total 100-Year life-Cycle Cost
$913 092
$850 00
Net Financial Savings
Baseline
$630 092 (7.0 % Savings)
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Issue 4 – 2026
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