How do they make concrete ties?

(Si prefieres leer este artículo en español haz clic aquí: http://ingjoseguerrero.blogspot.mx/2013/09/como-se-fabrican-los-durmientes-de.html )

General characteristics for concrete ties:

1. They are prefabricated in specialized plants. They consist of high-strength concrete, prestressed steel reinforced and/or post-tensioned.

2. They meet the same conditions, but with a much longer life, as wood ties: distribute the train wheels loads on the ballast and withstand the effects of weathering.

3. Parameters for concrete resistance (minimum):
   3.1. Compressive strength: f'c = 37 psi.
   3.2. Resistance to bending stress: MR = 4.50 psi.

4. Parameters for steel resistance (minimum yield strength):
   4.1. For reinforcing steel: fy = 296 psi
   4.2. For prestressing steel and/or post-tensioned: fy = 986 psi.

Here I share a video showing the manufacturing process of these ties (thanks DHASA).