Manufacturing

The manufacturing phase includes the upstream processes of the products used in the bridge and the associated transport, from the acquisition of raw materials to materials that are ready to be used in the construction of the bridge. The prestressed concrete precast bridge has three main components: beams of precast concrete, fresh concrete and steel. Therefore, first it is necessary delimit the activities associated with each product including the transport.

On one hand, the manufacture of the beams of precast concrete takes into account all the activities from the extraction of raw materials to the finishing of the beams in the precast plant, while the manufacture of the fresh concrete for the slab takes into account the activities from the extraction of raw material to the point when the concrete is ready to be used in the construction place. In both cases, the distance considered between the quarry and the precast plant or concrete plant is 50 km, the distance considered in the cement transportation is 20 km and the distance between the concrete plant and the construction site is 50 km. Furthermore, the dosage of concrete is taken into account to achieve the strength required. On the other hand, the manufacture of the steel takes into account all the activities from the acquisition of the raw material to the point when the steel is ready to be used in the precast plant or construction site. Considering that the bridge is built in Spain, the analysis takes the Spanish steel production characteristics. This implies that 67% of the steel is produced in an electric arc furnace and the remaining 33% is produced in a basic oxygen furnace. This ratio generates a recycling rate of steel of 71%. The distance considered between the steel production plant and the precast plant or construction site is 100 km. Table 2 shows the amount of material needed for the beam and slab and the dosage of the concrete in both cases.


**Table 2.** Amount of materials.
