The steel core
The steel core is performed from higher quality steel plates, which are acquired in the form of roller, they pass through an inspection before entering the assembly line. This roller is positioned in a tunneling machine having the features of leveling, grinding, welding and cutting the tube plate, with one specialized employee. Then this steel tube as well as the nozzles are placed in a rotating cradle where through two towers automatic welding is performed to weld, with minimal porosity. Both nozzles, as the steel sheet pass through a dimensional inspection mandatory.
The reinforcement steel
The billets and coils are formed by pre-selected steels and inspected . These are cut, bent and welded mechanized and always with the accompaniment of a specialized employee. When the reiforcement steel is completed, it is checked by a group of two workers, akin to detect possible welding defects.
The steel core is placed in an upright position, and is concreted inwardly and outwardly with the aid of a fixed mold. The tube will remain in this position until the concrete reaches the required minimum resistance allowing its displacement, that with our transmission system is 3 hours. These will be kept upright in a yard until the 15 days of healing, and give leave for the finishing and dispatch. On completion of the tube, these are again checked macroscopically in order to find possible flaws in the design of slots or openings for cracking of the concrete.
The type of cement used is Portland called, type CEM II / A-L 42,5R GR. In cases where the percentage of sulfates as SO4 exceeds 400 mg / l in water or 3000mg / kg in the field should use-resistant cements sulfates, which are called SR cements. If the percentage of sulfates, expressed as SO4 exceed 600 mg / l in water or 1200mg / kg in the ground, it is indispensable to apply the tube with additional protection-based bituminous paint with epoxy-based with a concentration of 0, 3 kg / m2.
The nature of the aggregates, their preparation and granulometry are such that ensure adequate strength and durability of the concrete. The study for the choice of the aggregates to form concrete complies with the NP EN 933-1 2000, NP EN 1097-6 2000, EN 933-3 NP 2000, NP EN 933-4 2002, NP EN 1097-5 2002 and NP EN 1097-3 2000.
The waters, both used in mixing and in the pipes concrete curing are characterized with acceptable in practice, with the parameters described in the standard NP EN 1008 2003.
The compositions of the concrete used for the reinforced concrete pipes with steel core are studied to assure the tightness, strength and durability required, according to the test fresh concrete by NP standards EN 206-1: 2007. concretes hardened by the standards: NP EN 12390-1 2003 NP EN 12390-2 2003 NP EN 12390-3 2003 and NP EN 12390-6 2003. chloride content of the limit contained in the concrete, the NP EN 639 2000. in order usual, The concrete used for the manufacture of our tubes belongs to C30 / 37 class, XC4 exposure class (concrete surfaces subject to contact with water, dried at cyclical periods of wet, according to the Eurocódigo 2 – Part 1 1 ).
The steel used for the manufacture of the steel core of reinforced concrete pipes, consists of a ductile and uniform thickness steel (being between 1.5 mm and 5 mm, depending on the measures concerned). For information, will be defined as type S-275 JR, according to NP EN 10025 in 1993.
The reinforcement steel
The passive reinforcement steel are formed by roughened steel wires with respect to the spiral and smooth for the Guidelines or electrowelded meshes, if the case allows. The steel in question, is of type A500, with a diameter of 8, 10 and 12 mm. Between turns, there may be a gap between 30mm and 200mm. Regarding the number of guidelines are recommended to use, 12, 18 or 36 per tube depending on the number of armature coils.
The addition of polypropylene fiber serves as an adjuvant in order to avoid cracking of the concrete, providing a substantial increase in the tensile strength of the concrete.
For engineering dimensioning is use by our engineering, a program prepared following the standards EN 639, EN 641 and EN 642