MPT PRESTRESSING AND POST-TENSIONING SYSTEM is designed and tested to meet stringent standards, The range of buildings and civil engineering applications includes:
MPT FLAT SLAB SYSTEMS:
MPT flat slab system is normally adopted for bonded tendon. The strands are individually gripped in one triangle flat anchor head unit and transmit their pre-stressing forces by means of flat type anchor plate casting unit. The strands are stressed individually by means of a mono strand jack. The strands are contained in one flat duct (duct size: 20mm x 70mm) which is made of corrugated galvanized metal. To ensure corrosion protection and to give adequate bond strength, the tendons are filled with suitable cement grout mix after complete stressing of the strands. Facilitating of concrete placing due to the absence of tendons in the webs, and ease for placing tendons.
MPT DEAD END ANCHORAGE:
Stressing of a tendon from one end only, to which the load is applied.
MPT MULTISTRAND ROUND SYSTEMS:
A method of reinforcing and pre-stressing concrete, masonry and other structural elements. Today, it is used for a wide range of applications including office buildings, condominiums, hotels, parking structures, slab-on-ground foundations, ground anchors, storage tanks, stadiums, silos, and bridges.
The systems are normally adopted for bonded tendons. The tendons consist of a bundle of strand with a nominal diameter of 0.5″ (12.7 mm.) or 0.6″ (15.2 mm.). The number of strands per tendon can be from 4 strands up to 42 strands of diameter 0.5″ or 31 strands of diameter 0.6″. The strands in the tendons are contained in one round duct which is made of corrugated galvanized metal.
The strands are individually gripped in one anchor head unit and transmit their pre-stressing force by means of anchor plate casting unit. For each anchor size, special spiral reinforcement is provided at the anchor plate casting to give adequate splitting reinforcement for bustling stresses developed at the anchorage zone. The strands in tendon are stressed simultaneously by means of a multi strand stressing jack from capacity 1,100 KN up to 5,000 KN. The strands can also be stressed individually by means of mono jack.
The strands are formed with seven steel wires: one central wire around which the other six are wrapped. They are generally supplied already stabilized (low relaxation) and certified according to the regulations by an independent laboratory, in coils weighing kg 2500-3000. Usually greased or waxed strands, incased in a HDPE sheath, commonly called unbounded, are used to manufacture the external tendons. Such Strands can be hot-dip galvanized too.
POST TENSIONING JACKS
The jack is placed over the strand and when tensioning starts they are automatically and simultaneously engaged in the pulling head of the jack. Once the required elongation and load are reached the lock-off device of the jack can be activated to house the wedges in the anchor head uniformly. The tensioning can be accomplished in more steps basing the elongation of the cable. A tensioned cable can be released using proper releasing device.
Cables are normally grouted after sealing their anchorages with the concrete or; if required, using the proper grouting caps. Before grouting the tendons, they should be flushed to ensure that no obstruction would impede the flow of the injected grout.
The sandless grout, injected using MPT grouting pump, is keep under pressure during its curing. The water-to-cement ratio is kept as low as possible. Usually the proportion of ingredients are: 36-38 liters of water, 100kg of cement and addictive according to the instruction of the manufacturer. The mix produces 72-74 liters of grout.