| Scenario | Coast (km) | Zone | w/c | Cover (mm) | Permeability | Crack (mm) | Coating | Drainage | Years |
|---|---|---|---|---|---|---|---|---|---|
| Bridge deck with deicers | 15 | Marine atmosphere | 0.50 | 35 | Medium | 0.30 | Penetrating sealer | Fair | 25 |
| Pier column in splash zone | 0.2 | Marine splash/tidal | 0.45 | 45 | Low | 0.10 | Film-forming membrane | Good | 40 |
| Inland slab, controlled mix | 80 | Inland / low salinity | 0.40 | 50 | Very low | 0.00 | None | Good | 15 |
Use the example scenarios to sanity-check your inputs before calculation.
Basic Index Model
Each input is converted to a normalized risk score rᵢ between 0 and 1. Each factor has a weight wᵢ, and the weights sum to 1.
Risk Index (0–100) = 100 × Σ(wᵢ × rᵢ)
Categories: Low (<25), Moderate (25–<50), High (50–<75), Severe (≥75).
- Enter site conditions (coast distance, zone, deicing salts).
- Enter durability parameters (w/c ratio, cover, permeability class).
- Add condition modifiers (crack width, coating, drainage, duration).
- Click Calculate Risk Index to view results above the form.
- Download CSV or PDF to share with design and inspection teams.
- This is a basic screening index for planning and comparison.
- For critical structures, confirm with exposure class standards and testing.
- Use consistent assumptions across projects to compare alternatives.
Chloride Exposure in Construction Environments
Chlorides are a primary driver of steel reinforcement corrosion in concrete. Coastal spray, tidal splash, industrial saline air, and winter deicing salts can deposit chloride ions on surfaces and drive ingress during wetting and drying cycles. Over time, chlorides can reach embedded steel, disrupt the passive layer, and initiate corrosion, leading to cracking, spalling, and reduced capacity.
Why a Basic Risk Index Helps Early Decisions
Early-stage projects often lack lab testing, yet teams still need consistent durability decisions. A basic index turns practical observations into a comparable score, so you can screen multiple assets, prioritize inspections, and justify mitigation budgets. It is not a code substitute; it is a structured way to compare “risk drivers” across locations and design options.
Key Inputs Used by This Calculator
This tool combines exposure and resistance indicators: distance to coast, exposure zone, deicing salt intensity, water–cement ratio, cover depth, permeability class, crack width, surface protection, drainage condition, and exposure duration. Each input is converted to a 0–1 risk score and combined with a weighted sum to produce a 0–100 index.
Interpreting the 0–100 Risk Scale
Scores under 25 suggest low screening risk when quality controls are strong and chloride sources are limited. Scores from 25 to under 50 indicate moderate risk where targeted improvements may be cost-effective. Scores from 50 to under 75 reflect high risk needing proactive protection and monitoring. Scores at 75 or higher indicate severe risk where enhanced detailing and protective systems are usually justified.
Typical Chloride Sources on Job Sites
Marine splash and tidal zones can deliver frequent wetting with salt water and aggressive deposition. Bridge decks and ramps can receive repeated deicing applications, raising surface chloride loads. Industrial sites near salt storage, fertilizer handling, or saline process water can also experience elevated airborne or splash chlorides. Even inland sites may face local exposures from brines and contaminated aggregates.
Mix Design and Cover Effects on Durability
Lower water–cement ratios commonly reduce permeability and slow diffusion pathways. In many durability strategies, w/c values around 0.40–0.45 are used for demanding exposure, while higher values can increase transport. Concrete cover is a direct diffusion length; increasing cover from 30 mm to 50 mm can materially slow chloride arrival at steel, if compaction and curing are well managed.
Protection, Drainage, and Maintenance Controls
Cracks can bypass the bulk matrix, especially when representative widths exceed about 0.3 mm under frequent wetting. Sealers and membranes reduce surface absorption and can lower effective ingress rates. Good drainage limits ponding time and reduces sustained saturation, which supports transport. Routine washing after deicing, joint maintenance, and timely crack repairs can measurably reduce long-term exposure severity.
Using Results for Planning and Documentation
Use the index to compare alternatives: adjust cover, improve mix resistance, apply coatings, or redesign drainage and then re-score. Save CSV and PDF outputs as a simple durability record for design reviews, handovers, and maintenance planning. When the index indicates high or severe risk, consider follow-up testing, exposure classification checks, and a defined inspection interval aligned with asset criticality.
1) What does the risk index represent?
It is a screening score from 0 to 100 estimating chloride-driven corrosion exposure based on site conditions and durability inputs. Higher scores mean higher likelihood that chlorides can reach reinforcement sooner.
2) Can I use this result as a compliance certificate?
No. It supports planning and comparison. For compliance, follow applicable exposure classes, specifications, testing, and local requirements. Use this tool to identify when deeper verification is needed.
3) How should I pick permeability class?
Use project quality data when available, such as test results or durability class targets. If uncertain, choose “medium” as a conservative baseline, then refine later with measured values or mix submittals.
4) Why do cracks matter so much?
Cracks provide preferential paths for chlorides, especially with repeated wetting. Wider or more frequent cracks can shorten time to corrosion initiation compared to intact concrete of the same mix design.
5) Does a coating always reduce risk?
Coatings typically reduce ingress, but performance depends on surface preparation, product selection, and maintenance. If coating condition is uncertain or deteriorated, choose “none” or a less effective option.
6) What inputs should I verify first on site?
Confirm exposure zone, deicing practices, drainage/ponding areas, and visible cracking. Then verify cover depth with inspection records or scanning and validate the mix’s resistance using submittals or testing.
7) How often should I update the assessment?
Update after major changes: repairs, new coatings, drainage improvements, exposure shifts, or new inspection findings. For high-risk assets, review at least annually or after harsh winter or storm seasons.