Cost-Effective Reinforced Concrete Corrosion Repair Systems
Key Takeaways
- Epoxy-coated reinforcing steel delivers the lowest 75-year life-cycle cost at $237/yd² — nearly half the $444/yd² life-cycle cost of uncoated reinforcing steel.
- Upgrading from uncoated to epoxy-coated rebar adds only 3.7% to initial deck cost ($189/yd² → $196/yd²) while extending time to first repair from ~14 years to ~50 years.
- Epoxy coatings raise the chloride corrosion threshold to 7.28 lb/yd³ — 4.6× higher than uncoated steel’s 1.58 lb/yd³ — significantly delaying corrosion initiation.
- Type 2205 stainless-steel reinforcing required no repairs in the 75-year analysis, but its $319/yd² life-cycle cost is $82/yd² higher than epoxy-coated reinforcing.
- Uncoated reinforcing has the shortest service life and highest total cost, with life-cycle expenses reaching roughly 2.3× the initial deck cost.
- For most bridge decks and parking structures, epoxy-coated reinforcing is the most cost-effective concrete corrosion repair and prevention strategy when balancing upfront investment, durability, and long-term maintenance.
75-Year Life-Cycle Cost Comparison
| System | Cost per yd² |
|---|---|
| Epoxy-Coated reinforcing | $237/yd² |
| Type 2205 Stainless-Steel reinforcing | $319/yd² |
| Uncoated reinforcing | $444/yd² |
Introduction
Owners of concrete structures are looking at ways of cost-effectively protecting new assets such as bridges and parking garages against corrosion. In order to conduct economic analyses for corrosion-induced damage, knowledge of chloride ingress, the amount of chloride to initiate corrosion, corrosion rates, and the amount of corrosion to cause cracking are required. This document summarizes key findings relating to the cost and performance of concrete bridge decks containing various corrosion-protective systems.
Overview
In 2011, the University of Kansas Center for Research published a report titled “Evaluation of Multiple Corrosion Protection Systems for Reinforced Concrete Bridge Decks.” The Kansas Department of Transportation and the Federal Highway Administration provided the majority of the funding.
The report provides an in-depth evaluation of the performance of corrosion inhibitors, uncoated, epoxy-coated, and stainless-steel reinforcing. It includes documentation of extensive laboratory and field research, an evaluation of the amount of corrosion to cause cracking, and an economic analysis. The pertinent findings from the report are summarized as follows:
Uncoated Reinforcing Steel — A bridge deck containing uncoated reinforcing steel has the shortest design life of all systems tested and also the highest life-cycle cost.
Epoxy-Coated Reinforcing Steel — Epoxy coatings significantly reduce the corrosion rates of reinforcing steel. Epoxy-coated reinforcing steel maintains low initial and life-cycle costs over a 75-year life-cycle, and use of epoxy-coated reinforcing steel was found to be substantially more cost-effective than either using uncoated reinforcing steel in concrete containing corrosion inhibitors or stainless-steel reinforcing.
Stainless-Steel Reinforcing — Type 2205 stainless-steel reinforcing has an initial cost that increased the deck cost by approximately $130/yd² or 70 percent over the cost of uncoated reinforcing steel. The life-cycle cost of concrete with these bars was $82/yd² or 35% greater than that of epoxy-coated reinforcing steel.
Test Program
An extensive test program was conducted on concrete containing corrosion inhibitors, uncoated, ASTM A775 epoxy-coated, and Type 2205 stainless-steel reinforcing. The goal of the testing was to determine the performance of these materials so the results could be used in an economic model.
Tests included Southern Exposure, Cracked Beams, and Corrosion Initiation specimens, as well as Field Exposure slabs. Measurements included macrocell voltage, mat-to-mat resistance, corrosion potential, and linear polarization resistance. The amount of chloride in the concrete during the testing was also determined.
Chloride Threshold
The amount of chloride required to initiate corrosion in uncoated reinforcing steel was 1.58 lb/yd³. The amount of chloride required to initiate corrosion in the epoxy-coated reinforcing steel was found to be 7.28 lb/yd³, or 4.6 times that of the uncoated reinforcing steel. This was substantially greater than that required for concrete with uncoated reinforcing steel and corrosion inhibitors, where values of 0.83 to 3.05 lb/yd³ were determined. When epoxy-coated reinforcing steel and corrosion inhibitors were combined, chloride amounts of 1.69 to 9.85 lb/yd³ were required to initiate corrosion. A chloride threshold of 26.4 lb/yd³ was determined for the Type 2205 stainless-steel reinforcing.
Corrosion Rates
After corrosion initiation, the corrosion rates of the bars were measured. The uncoated reinforcing steel exhibited the highest corrosion rates among the systems studied. Epoxy-coated reinforcing steel was found to have a significantly lower corrosion rate compared to the systems containing uncoated reinforcing steel. Use of corrosion inhibitors in the concrete together with either uncoated or epoxy-coated reinforcing steel reduced observed corrosion rates.
Corrosion to Cause Cracking
The amount of corrosion to cause cracking was extensively studied using experimental and finite element analyses. An equation was developed for the amount of corrosion to cause cracking, based upon the concrete cover, bar diameter, and the fractional length and area of the bar that is corroding.
For uncoated reinforcing steel, the corrosion losses required to crack concrete are directly proportional to the clear concrete cover. For isolated corrosion sites, such as occur at damage sites on epoxy-coated steel reinforcing, the relationship changes to one that is directly proportional to the square of the concrete cover.
Time to Repair
The time to repair is determined by adding the initiation period to the propagation period. An additional five-year period was provided within the report to account for time from the first crack to the repair of the deck. The report explains that a five-year delay between first cracking and repair is assumed for all corrosion protection systems.
Corrosion rates from cracked concrete only were used in this study, as “…bridge decks inevitably develop cracks over the reinforcement; the comparisons using the corrosion rates in cracked concrete likely provide the more accurate representation of corrosion in bridge decks.”
For uncoated reinforcing steel in cracked concrete, repair would be required after 14 years, whereas for epoxy-coated reinforcing steel in cracked concrete, repair would be required after 50 years. The systems with Type 2205 stainless-steel reinforcing did not require repair during the 75-year analysis period.
Timeline Summary (Initiation, Propagation, and Repair)
| System | Initiation Period | Propagation Period | First Repair Required |
|---|---|---|---|
| Uncoated reinforcing | 2.2 yr | 6.8 yr (+ 5 yr delay) | ~14 yr |
| Epoxy-Coated reinforcing | 20.3 yr | 24.8 yr (+ 5 yr delay) | ~50 yr |
| Type 2205 Stainless-Steel reinforcing | 67.6 yr | 224 yr | None within 75-year analysis period |
Critical Chloride Thresholds: Uncoated 1.58 lb/yd³ · Epoxy-Coated 7.28 lb/yd³ · Stainless-Steel 26.4 lb/yd³
Initial Costs
Initial cost analyses were conducted using costs of a typical bridge deck. Initial costs of $0.35, $0.45, and $2.35 per lb were used for uncoated, epoxy-coated, and Type 2205 stainless-steel reinforcing, respectively. Placement costs were estimated at $0.52 per lb. The amount of reinforcing steel in a deck was approximately 275 lb/yd³, and the in-place cost of normal concrete used in the analyses was $562/yd³.
For uncoated reinforcing steel, the initial deck cost was determined to be $189/yd². The use of epoxy-coated reinforcing steel increased the deck costs by only 3.7% to $196/yd². When stainless-steel reinforcing was used, deck cost increased by $130/yd² or approximately 70% to $319/yd².
Life-Cycle Cost
Life-cycle costs are determined by considering the net present value of all the costs during the life of a structure. Based on using an appropriate discount rate of 4%, the initial and repair costs were considered during a 75-year period. Repairs were assumed to last 25 years before an additional similar repair would be required, and repair costs were assumed to be $283/yd².
For uncoated reinforcing steel, the life-cycle cost for a bridge deck was estimated to be $444/yd², which was approximately 2.3 times the initial deck cost. The life-cycle cost of a deck using epoxy-coated reinforcing steel was only $237/yd², almost half that of the deck containing uncoated reinforcing steel. When Type 2205 stainless-steel reinforcing was used, the life-cycle cost of the system was $319/yd² — almost $82/yd² greater than that of epoxy-coated reinforcing steel.
Cost Summary
| System | Initial Cost | 75-Year Life-Cycle Cost |
|---|---|---|
| Uncoated reinforcing | $189/yd² | $444/yd² |
| Epoxy-Coated reinforcing | $196/yd² | $237/yd² |
| Type 2205 Stainless-Steel reinforcing | $319/yd² | $319/yd² |
Initial and 75-year life-cycle costs using a discount rate of 4 percent.
Frequently Asked Questions About Concrete Corrosion Repair
What are the most cost-effective concrete corrosion repair methods?
The most cost-effective approach to concrete corrosion repair is to prevent the problem at the design stage rather than rely on repeat repairs after damage occurs. Based on the University of Kansas 75-year life-cycle analysis, epoxy-coated reinforcing steel delivers the lowest total cost of ownership at $237/yd² — nearly half the $444/yd² life-cycle cost of uncoated steel and roughly $82/yd² less than Type 2205 stainless-steel reinforcing at $319/yd². When concrete corrosion repair is unavoidable, full-depth deck repair (assumed to last 25 years at $283/yd² in this analysis) is the typical approach for bridge decks. Pairing repairs with epoxy-coated replacement bars or supplementing the repair zone with corrosion inhibitors helps extend the interval to the next concrete corrosion repair cycle.
What causes corrosion in reinforced concrete?
Corrosion in reinforced concrete is primarily driven by chloride ingress from de-icing salts, marine environments, or contaminated mix materials. Once chlorides reach the reinforcing steel in concentrations above the critical threshold, the passive oxide layer on the bar breaks down and corrosion initiates. The Kansas study found that uncoated reinforcing steel begins corroding at just 1.58 lb/yd³ of chloride, while epoxy-coated reinforcing steel requires 7.28 lb/yd³ — about 4.6 times more — and Type 2205 stainless-steel reinforcing requires 26.4 lb/yd³.
How long before a bridge deck needs concrete corrosion repair?
It depends entirely on the reinforcement system. In cracked concrete, uncoated reinforcing steel requires its first concrete corrosion repair at roughly 14 years (2.2-year initiation + 6.8-year propagation + 5-year repair delay). Epoxy-coated reinforcing steel pushes that out to about 50 years (20.3-year initiation + 24.8-year propagation + 5-year delay). Type 2205 stainless-steel reinforcing did not require any repair within the full 75-year analysis period.
Is epoxy-coated rebar worth the extra cost?
Yes, by a wide margin in the 75-year analysis. Switching from uncoated to epoxy-coated reinforcing steel raises the initial deck cost by only about 3.7% (from $189/yd² to $196/yd²) but cuts the 75-year life-cycle cost nearly in half. The combination of a much higher chloride threshold, significantly lower corrosion rates, and a much longer time to first repair is what drives the savings.
When does stainless-steel reinforcing make sense?
Type 2205 stainless-steel reinforcing showed the longest service life — no concrete corrosion repair needed during the 75-year analysis period — but its initial cost is roughly 70% higher than uncoated steel, and its 75-year life-cycle cost ($319/yd²) is still about $82/yd² greater than epoxy-coated reinforcing. Stainless-steel reinforcing tends to be most justifiable for highly aggressive exposure environments or structures where access for future concrete corrosion repair is extremely costly or disruptive.
Do corrosion inhibitors reduce concrete corrosion repair costs?
Corrosion inhibitors can raise the chloride threshold and slow corrosion rates, particularly when paired with uncoated or epoxy-coated reinforcing. In the Kansas study, inhibitors raised the chloride threshold for uncoated steel to a range of 0.83–3.05 lb/yd³, and combining inhibitors with epoxy-coated reinforcing produced thresholds of 1.69–9.85 lb/yd³. However, the report found that none of these combinations matched the cost-effectiveness of epoxy-coated reinforcing on its own.
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References
- O’Reilly, M.; Darwin, D.; Browning, J.; Carl E. Locke, J. “Evaluation of Multiple Corrosion Protection Systems for Reinforced Concrete Bridge Decks”; The University of Kansas Research Inc., Lawrence, KS, 2011.
The full summary report titled Evaluation of Multiple Corrosion Protection Systems For Reinforced Concrete Bridge Decks is available from the Epoxy Interest Group of CRSI.