Environmentally friendly railway sleepers with calcium sulfoaluminate cements

The railway sleepers manufacturers, represented in the research project by the project partner PCM RAIL.ONE AG, are aiming to improve the life cycle assessment of their products. However, this improvement has to involve a constant production speed. Consequently, it would be necessary to use cements which combine life cycle benefits with rapid strength development and high durability. For this purpose, cements based on calcium sulfoaluminate (CSA cements) could be used. Their suitability for the production of precast concrete elements will be investigated in this research project using the example of "railway sleepers".

The research project will investigate whether the technical requirements for railway sleepers with CSA cements can be realised. Also, some basic links to standards (e.g. modulus of elasticity, creep and shrinkage in accordance with EC2) must be checked and ensured.

Essential requirements for the production of railway sleepers are the strengths to be achieved at an early age (24 h) and after 28 days. Demanding and clearly defined requirements are also placed on the fresh concrete properties and the temperature development during hardening. These properties will be investigated in the first project phase using CSA cements or a combination of CSA cements and Portland cement clinker based cements.

In the second project phase, the durability of the concretes with CSA cements or a combination of CSA cements and Portland cement clinker based cements as well as the creep and shrinkage of the concretes are investigated. The second phase of the project will be completed by practical trials with the project partner PCM RAIL.ONE AG as well as a life cycle assessment of the developed concretes.

Railway sleepers are produced as precast concrete elements in a high-cycle manufacturing process. The “German Railway Standard (DBS) 918143” specifies CEM I 52,5 N for the production of sleepers. This is used, among other things, to achieve high early strengths after 24 hours. The production of 1 t Portland cement is emitting approx. 0.8 t of CO₂. These emissions affect the life cycle assessment of railway sleepers.