The fatigue strength test, as established in the UNE-EN 12697-24 standard, is of great relevance in the field of pavement engineering, especially in the context of the reuse of pavement layers and bituminous pavements. This test is described in Annex D of the standard (Four-point bending on prismatic specimens, 4PB-PR) and consists of the application of a sinusoidal load with the aim of inducing a constant deformation on the sample analysed, replicating the conditions to which the pavement will be subjected during its service life.
Why is fatigue testing important?
Circular Order OC 2/2023 of the Ministry of Transport, Mobility and Urban Agenda (MITMA) introduces new guidelines on the reuse of pavement layers and bituminous pavements, establishing the need to assess the fatigue deformation at one million cycles (ε6). This standard is crucial for the design and evaluation of recycled pavements, as it ensures the durability and functionality of the pavement under heavy traffic conditions and repeated loading cycles. The fatigue test allows the behaviour of the pavement over its service life to be determined, which facilitates the estimation of its performance under real-life conditions and helps to predict when failures due to material fatigue might occur.
In addition, OC 2/2023 establishes that the incorporation of bituminous pavement reuse rates, such as the use of recycled materials (RAP), must comply with certain parameters, including fatigue deformation. This technical control is mandatory and has a direct impact on the reuse of old pavements in the construction of new road infrastructure, helping to reduce the costs and environmental impact of construction.
Details of the procedure
The test involves the compaction of four slabs of bituminous mix, which are then cut into 16 specimens. Each specimen is subjected to a loading and unloading cycle in bending using a testing machine that simulates the stresses and strains to which the pavement will be exposed during use. The test measures how the mix behaves under fatigue, allowing the ability of the mix to withstand repeated loading without premature failure to be identified.
Results
The report issued by the laboratory (such as that of the Centro Tecnológico de la Construcción) is used to certify compliance with administrations and entities that require compliance with the parameters established in OC 2/2023 in projects involving the use of recycled materials in bituminous pavements. The results report will include the fatigue law values and, if necessary, additional information on the behaviour of the material.
Conclusion
The fatigue resistance test according to UNE-EN 12697-24 is an essential tool to guarantee the quality and durability of bituminous pavements, especially in the context of the reuse of recycled materials. With this test becoming mandatory under the new MITMA regulations, construction professionals must ensure that recycled pavements meet long-term performance criteria to guarantee the safety and efficiency of road infrastructures.
