Slippery mold (vertical ascending, slippery in direction of horizon)
Any change of technology in construction industry which is based on scientific and engineering scales and attention to used expenses and time is considerable. Although conjunct modular molds may be used for high structures but application of slippery mold is considered by experts and experienced executers of construction industry.
Slippery mold method is more used in orthogonal and high concrete structures in our state. These molds are separated from concrete in crawling form after each concreting. Height of slippery mold is 1 to one and half meters and concreting operation is performed by slippery mold day and night time. Also speed of mold lifting is various and depends on temperature and specifications of concrete which is from 5 to 7 cm per hour to 30 cm per hour.
Slippery mold has two types:
- Slippery mold with fixed segment
- Slippery mold with variable segment
If segment of structure is fixed and its thickness doesn’t change at height, slippery mold with fixed segment is sued. But if segment of structure is variable and its walls don’t change, slippery mold with variable segment is sued. Set of elements which result in slippery mold includes: yook, leg of yook, beam and head beam, platform, support, repair platform, hydraulic system, slippery jack and jack rod. Movement of slippery mold system is based on propelling power due to movement of hydraulic jack of humeral jaw.
Slippery molds with two orthogonal and vertical movement systems are used in following structures:
- high pillars
- shear walls of high concrete structures
- single or multi cell grain depot
- liquid tanks
- orthogonal shaft of tunnels and mines
- orthogonal shaft of missile throw platforms
- high chimneys
economic advantages of this system are: need to less worker, no need to face scaffold, high speed of operation, decrease of mold manufacturing expense, possibility of prefabricating mold pieces in factory and diminishing workshop operation, not having orthogonal and vertical seam in concrete surface and expose face.
Main sections of a slippery mold
Mold walls: it shall be firm and insistent. These walls may be from wood or metal. Metal forms are heavier than wooden molds but have more solidity and may be used more. Possible repair or change of metal molds is more difficult than wooden molds, instead, their cleaning is easier and concrete face is flatter after opening.
The molds are in three sections:
- lateral clamps (Kamarkesh)
- body mold
They have two main duties: to prevent from opening molds for lateral pressures of concrete and transfer of load and pressure to jacks
Clamps: clamps have been manufactured for reinforcement of bend resistance of manufactured mold body and transfer load of molds to yoks. Joinery platform, executive deck and tressed platform are connected to lateral clamps. It shall be able to transport these loads by connection of clamps to yoke.
Body mold which may be metal panel, multilayer panel or timbers is connected to lateral clamps directly.
Ring: It is used for keeping work platform and its transfer and also tolerating weight of mold and jack cable. The rings are usually designed and made in metal kind and suitable profiles.
Work platform: three work places are usually considered. One is higher than rings in about 2 meters height and higher than end of wall and used for fixing metal ties. Another platform is located at above floor and level with mold and used for placing concrete vessel and storage of materials and balancing tools and also jack control tools. Finally, the third platform is in form of hanging framework and at two sides of wall and used for access to face of wall and its possible repair.
Hydraulic Jacks: Hydraulic Jacks are determined by three tones or six tones jacks.
Upright slippery molds
Base of performing vertical slippery mold is that the mold is raised up to one to one and half meters height at alternate times. During raising mold, concreting and armature operations will continue and concrete is poured into mold and hardened concrete is exited from lower part of mold. Movement speed of mold is so that concrete has sufficient resistance for keeping its form while exiting from mold. Vertical slippery formwork may be performed by a continuous movement or planned so that it stops at a determined height and begins its movement again after a while. Movement of slippery mold has a steady speed. If slippery mold is stopped due to any reason, there will be some seams in concrete which are executive seams and there is no different between them and executive seams of concreting by fixed mold. Slippery mold moves upright by steady speed and this speed is so that each concrete segment remains in mold for a term necessary for primary hardening. Vertical slippery formwork is used for shell structure with fixed or variable wall thickness. Vertical slippery molds are raised by some jacks that move on bars or structural pipes set in harden concrete and operate as a support. These jacks may be manual, pneumatic, electrical or hydraulic types. Working platforms (platforms for stand of workers, armature, mold or concreting makers) and scaffolds necessary for scaffolding are connected to slippery molds and move with them. Many scaffolds are omitted by use of this formwork and a better face is produced for concrete structure. In addition, use of this formwork method increases speed of work. The most important advantage of slippery mold is continuous movement of mold on surface of structure which cause expose surface in addition to high speed and economic gain. Slippery molds are the most effective executive methods in performing high structures with fixed or variable wall thickness. Expense of using slippery molds with hydraulic jacks is less than other old and traditional methods. Movement of slippery molds is performed by hydraulic tower jacks which are heart of slippery molds.
Slippery mold hydraulic jack
Propelling power of vertical slippery molds is supplied by jacks that are installed in the middle of yoke. These jacks are connected to lower part of head beam by jack holder sheet. Power pack system (hydraulic unit) slips upward by high pressure hoses of jacks on steel jack bar and moves slippery mold with it. Transfer of jack power to hardened concrete is performed by jack bar so that jack bar passes from middle of jack and relies on hardened concrete at base. These pieces are connected by middle of jack bar. Sheath of jack bar is installed for preventing contact of fresh concrete with jack baron lower part of jack and make possible to exit jacks from concrete. An exceptional advantage of 6 tones slippery jacks of Parsian Ghaleb is slip of jacks on jack bars by shot and their maintenance expenses is less than Fak Shanehei فک شانه ای and their slipping is more easy. Two 3 and tones slippery jacks are manufactured and offered to market by this industrial group.