ChromX® is an uncoated steel that offers up to five times the corrosion resistance of conventional steel.
Some of the world’s most prominently engineered bridges, roads, heavy infrastructure projects (tunnels, dams, spillways), building structures and parking garages start with ChromX®, which has been independently tested and proven to be five times more corrosion-resistant than conventional steel.
ChromX® is the solution to corrosion problems caused by:
- De-icing salts and chemicals
- Marine environments
- Aggressive soil compositions
- High humidity
- Severe daily temperature swings
Specifying ChromX® concrete reinforcing steel resolves concerns about declining service life and spiraling life-cycle costs for bridges, highways and other commercial grade structures due to harmful corrosion.
Structures built with ChromX® rebar deliver:
- Up to 100-year service life
- Lower life-cycle costs
- Reduced material costs compared to stainless steel
- ChromX® 4100 has comparable or reduced installed costs to epoxy-coated and galvanized steel
- Superior corrosion protection compared to black steel, epoxy-coated rebar and galvanized rebar
Over 100-Year Service Life
Reinforced concrete breakdown begins when the chloride concentration at the surface of the reinforcing steel reaches a critical chloride threshold value (CT). Once corrosion is initiated, progressive cracking and spalling of the concrete follows, based on the defined corrosion rate (CR) of the reinforcing steel that was used during construction. Deterioration of the structure continues until the structure’s service life is ended.
|COMPARATIVE TABLE OF SERVICE IN LIFE IN YEARS FOR VARIOUS REINFORCEMENT & ENVIRONMENTS
||Pile Mix LP
||Pile Mix LP
||1.5 in (37.5 mm)
||2.0 in (50.0 mm)
||1.5 in (37.5 mm)
|Black Bar (BB)
|Epoxy Coated (ECR)
|ChromX® 4100 with 2 Gpy CNI
|ChromX® 9100 (ASTM A1035)
|UNS S32304 (Stainless Steel)
|Reinforcing Steel Comparative Durability Assessment and 100-year Service Life Cycle Cost Analysis Report, Tourney Consulting Group LLC. June 2016
The life of a structure goes through three stages:
Stage 1 (corrosion initiation) – time for chlorides to penetrate into the concrete to the level of the steel and reach the corrosion threshold level of the steel.
Stage 2 (propagation) – time from initiation of corrosion to initiation of concrete spalls.
Stage 3 (repair) – period after spalling when repairs temporarily extend life of structure.
As the timeline below shows, ChromX® rebar extends the operational service life by delaying the concrete spalling and need for first repair up to 100 years by delaying corrosion initiation with a higher chloride threshold and slowing propagation due to a lower corrosion rate. Conventional steel reaches its end of economic life before corrosion initiation even begins for ChromX® 9100.
Corrosion Timeline, Conventional Black Steel vs. ChromX® 9100
Using lifecycle cost analyses, many public agencies and private owners have found that using more advanced materials, such as ChromX® rebar, can save them and their taxpayers millions of dollars in future maintenance and rehabilitation costs when compared to standard or epoxy coated rebar. The cost benefits of ChromX® are realized in the first 20-30 years, at the time when repairs would be required if traditional rebar products were used.
||Est. Initial Cost
|ChromX® 4100 w/CNI4
|Stainless Steel (UNS S32304)
1. Service lives estimated based on CT values determined in Critical Chloride Corrosion Threshold for Galvanized Reinforcing Bars, David Darwin et al., Univ. of Kansas Center for Research, Inc. (Dec. 2007), as well as CT and CR values, and STADIUM® software modeling for a concrete bridge deck with 1.5 in. (37.5 mm) Bridge Mix LP concrete cover according to Reinforcing Steel Comparative Durability Assessment and 100 Year Service Life, Tourney Consulting Group, LLC (June 2016).
2. Estimated net present value (NPV) per square foot of the total life cycle costs of the bridge deck, assuming $150 per square foot repair costs every 15 years after year of initial repair.
3. Based on chloride threshold data from Tourney Consulting Group, LLC testing of ChromX® 2100 Alloy (2017).
4. Adding 2 gallons of calcium nitrite (CNI) as a concrete additive at an estimated cost of $12 per cubic yard has been shown to further enhance ChromX® 4100's corrosion performance.