Le secteur du BTP vit une révolution : celle du réemploi. L’acier, avec sa durabilité exceptionnelle et sa capacité à être démonté sans perdre ses propriétés, est le candidat idéal pour l’économie circulaire.
Cependant, contrairement à un produit neuf sortant d’usine avec son certificat 3.1, un acier de déconstruction soulève une question critique : comment garantir sa sécurité structurelle ? Voici les étapes incontournables pour savoir si un acier est réemployable.
The "resource" assessment: the visual inspection
Before any laboratory analysis, everything begins on the deconstruction site. Reusable steel must first pass the test of physical inspection.
Surface condition: superficial rust is acceptable. On the other hand, deep corrosion with section loss (pitting or lamination) often disqualifies the element for load-bearing structural functions.
Deformations: profiles (IPN, HEA) must show no warping, twisting, or visible residual deflection.
Human-induced alterations: we look for unauthorized drill holes, welds from secondary equipment, or torch cuts that may have weakened the part.
Traceability and documentary research
The availability of the original building’s health record is a major asset for validating reuse potential. In this context, the year of construction provides a valuable first indication of the likely steel grade. This documentary research also relies on as-built drawings, which are essential for accurately identifying the loads the element carried during its first life.
Technical testing: proof through data
To reintegrate steel into a new structural calculation, the engineer needs guaranteed values. This is where laboratory tests come in.
Chemical analysis (spectrometry)
Il est important de vérifier la soudabilité de l’acier, surtout pour les structures anciennes. Avec la Spectrométrie, on mesure notamment l’équivalent carbone (Ceq). Un taux trop élevé de carbone ou de phosphore rend le soudage risqué (risque de fissuration à froid).
Mechanical testing
During mechanical tests, specimens are taken from a representative sampling of the deposit to measure:
The yield strength (Re) : the threshold value before permanent deformation.
The tensile strength (Rm) : the maximum load supported.
The elongation after fracture (A%) : to check the metal's ductility.
Impact test (Charpy)
The Charpy impact test is essential for structures exposed to low temperatures or impact loads. It checks the steel’s ability to absorb energy without brittle fracture at a given temperature (e.g. 27 Joules at 0°C).
The regulatory framework: CTICM, the reference guide
In France and across Europe, the reuse of steel is now governed by strict protocols such as the CTICM Guide (Technical Industrial Centre for Metal Construction). This document defines:
The performance classes of the stock.
The number of tests to be carried out depending on tonnage.
The method for recalculating safety factors.
Summary: green light for reuse
| Green Signal 🟢 | Orange Signal 🟠 | Red Signal 🔴 |
| Identified grade (e.g., S235). | Surface corrosion that can be treated by sandblasting. | Cracks at the welds. |
| Perfect geometry. | No original documentation available (tests required). | Steel that has been exposed to fire. |
| Carbon equivalent < 0.45%. | Previous dynamic use (overhead crane). | Visible plastic deformation. |
In conclusion
Knowing whether steel can be reused is a mix of field observation and scientific rigor. While the cost of testing may seem high, it is largely offset by material savings and environmental benefits (one tonne of reused steel saves around 1.5 to 2 tonnes of CO2).
Ready to integrate reused steel into your projects? Contact us to discuss your project