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PD CEN TS 16637 — Construction Products Assessment of Release of Dangerous Substances (Leaching Test) Standard Series
Construction Products — Assessment of Release of Dangerous Substances
🧱 PD CEN TS 16637 is the British Standards Institution (BSI) Published Document implementing the European Technical Specification CEN/TS 16637, dedicated to assessing the release of dangerous substances from construction products. Prepared by UK technical committee B/557 “Construction products — Assessment of dangerous substances,” it is classified under ICS 13.040.20 (ambient air quality), 19.040 (environmental testing), and 91.100.01 (building materials in general). It provides a harmonised system of leaching and percolation test methods for concrete, mortar, aggregates, masonry, coatings, and many other construction products, forming a key technical basis for release assessment under the EU Construction Products Regulation (CPR).
💡 The “safety” of a construction product depends not only on its mechanical performance but also on the dangerous substances (heavy metals, inorganic salts, etc.) it can release into the water environment over its service life. Leaching and percolation tests quantify this potential release into comparable, assessable data.
1. Series Structure and Overall Framework 📌
The PD CEN TS 16637 series comprises 3 parts: Part 1 is the test guidance, while Parts 2 and 3 specify two categories of test method. All three share the same ICS classification and cross-reference each other, together forming a coherent methodology for release assessment.
| Part | Year | Title | Core Content |
|---|---|---|---|
| PD CEN/TS 16637-1 | 2014 | Guidance for the determination of leaching tests and additional testing steps | Sets out how to choose the appropriate leaching test and further testing steps based on product form and exposure scenario |
| PD CEN/TS 16637-2 | 2014 | Horizontal dynamic surface leaching test | Defines a dynamic leaching test for monolithic or block products in contact with water |
| PD CEN/TS 16637-3 | 2016 | Horizontal up-flow percolation test | Defines a percolation test for granular products with water flowing upwards through the bed |
⚠️ A CEN/TS is a provisional Technical Specification, evaluated after its validity period for possible conversion into an EN. Always reference the current effective version of PD CEN TS 16637 and monitor amendments or re-issue to keep methods aligned with the latest regulation.
2. Test Selection Guidance: The Part 1 Methodology 🧭
Part 1 provides the methodological foundation of the whole series. It guides the user to choose correctly between the “monolithic/block product” and “granular/bulk product” categories according to product characteristics and use scenario, and to determine the corresponding test steps:
- Monolithic/block products (e.g., concrete slabs, bricks, coated panels): use the surface leaching test (Part 2), examining release in relation to the contact area with water.
- Granular/bulk products (e.g., aggregates, soils, crushed materials): use the percolation test (Part 3), examining release as water flows through a particle bed.
- Additional testing steps: the guidance also defines supplementary tests and data treatment needed to further characterise release (e.g., long-term release, pH-dependent release).
The guidance stresses that test design should reflect the product’s real exposure conditions, including the composition of the contact medium (e.g., pH, salinity), liquid-to-surface/solid ratio, contact time, and temperature, so results are representative and comparable.
3. Surface Leaching Test: The Part 2 Method 🔬
Part 2 specifies the Horizontal Dynamic Surface Leaching Test, applicable to monolithic or block products. A test specimen with a defined surface area is contacted with a leachant (typically deionised water or a simulated medium) under controlled conditions, with the leachant renewed or replaced at prescribed time intervals. The concentration of substances released into the liquid phase at each interval is measured, yielding release rates and cumulative release per unit surface area and time.
| Key Parameter | Description |
|---|---|
| Surface area to volume ratio | Governs the relationship between contact area and leachant volume, affecting release kinetics |
| Leachant renewal interval | Leachant is replaced at set time steps to obtain a release curve over time |
| Liquid-to-surface ratio (L/S) | Ratio of leachant volume to specimen surface area — the basis for expressing and comparing results |
| Temperature and agitation | Controlled temperature and uniform liquid-solid interface contact |
This method suits surface-dense products such as coatings, panels, and blocks; results can be used to estimate the long-term diffusive flux of pollutants to the water environment.
4. Up-flow Percolation Test: The Part 3 Method 💧
Part 3 specifies the Horizontal Up-flow Percolation Test, applicable to granular or bulk products. A sample of defined particle size distribution and compaction is packed into a percolation column; leachant flows upwards at a constant rate through the sample bed. The eluate is collected in volume fractions, and the concentration of dangerous substances in each fraction is measured to characterise release from particles under dynamic flow.
| Key Parameter | Description |
|---|---|
| Column dimensions and packing | Column diameter, particle size distribution, and packing density set per standard to ensure uniform flow |
| Up-flow velocity | A constant flow rate simulates rainwater or groundwater passing through a material layer |
| Liquid-to-solid ratio (L/S) | Expressed as cumulative eluate volume per unit sample mass — the x-axis variable of percolation results |
| Fraction collection | Eluate collected in L/S fractions to obtain release concentration versus L/S curves |
The percolation test is especially suited to loose products such as aggregates, recycled materials, and soil amendments, and is often combined with leaching data in life-cycle environmental assessment.
✅ Part 1 selects the method, Part 2 measures “surface release,” and Part 3 measures “particle release” — together they fully characterise the release behaviour of construction products in real use and recycling scenarios.
5. Engineering Practice and Application Notes 🛠️
- 🔍 Exposure-scenario modelling: choose the leachant and test method according to the product’s position (indoor, outdoor, underground, submerged) so tests approach real exposure.
- 🔧 Data interpretation: release curves (concentration-time, concentration-L/S) are the core output; compare with regulatory limits and risk thresholds to judge conformity.
- 📊 Link to the CPR: results can support the dangerous-substance release assessment in CE marking (e.g., Declaration of Performance) of construction products.
- 📋 Quality control: use standard-specified equipment and reagents, run replicates and blanks, and ensure results are repeatable and traceable.
6. Frequently Asked Questions ❓
❓ Q: When should I use the surface leaching test (Part 2) versus the percolation test (Part 3)?
A: Use the surface leaching test for monolithic/block products and the percolation test for granular/bulk products; do not mix them — the choice is determined by product form and exposure scenario per the Part 1 guidance.
A: Use the surface leaching test for monolithic/block products and the percolation test for granular/bulk products; do not mix them — the choice is determined by product form and exposure scenario per the Part 1 guidance.
❓ Q: Why is the liquid-to-solid ratio (L/S) important?
A: L/S reflects the relationship between product mass and contacting water volume, and is the basis for release curves and comparison. Different tests have different L/S ranges, so results must be compared at a consistent L/S.
A: L/S reflects the relationship between product mass and contacting water volume, and is the basis for release curves and comparison. Different tests have different L/S ranges, so results must be compared at a consistent L/S.
❓ Q: How are test results used for conformity?
A: Compare measured release concentrations or cumulative release with the limits applicable to the product (e.g., EU or UK limits), considering exposure scenario and risk thresholds.
A: Compare measured release concentrations or cumulative release with the limits applicable to the product (e.g., EU or UK limits), considering exposure scenario and risk thresholds.
🔍 Q: Why use a “horizontal” dynamic surface test and an “up-flow” percolation?
A: The horizontal dynamic surface test simulates relative motion between the product surface and water; the up-flow percolation simulates the real direction of groundwater flow through a material layer, avoiding gravity short-circuiting and giving more representative results.
A: The horizontal dynamic surface test simulates relative motion between the product surface and water; the up-flow percolation simulates the real direction of groundwater flow through a material layer, avoiding gravity short-circuiting and giving more representative results.