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A23.4-09
©
Canadian Standards Association
November 2009
28.2.7 No-slump concrete products
28.2.7.1 General
Documented procedures for manufacturing no-slump concrete products shall be established by the
precast concrete manufacturer.
Note:
In most cases, the supplier of equipment for no-slump concrete products will have established operational procedures
and standards that should be followed.
28.2.7.2 Detensioning
28.2.7.2.1
Before detensioning, the concrete strength shall be determined in accordance with
Clause 19.8.2
.
28.2.7.2.2
Tendon slippage shall be checked during detensioning by establishing a reference line close to the free end
of the casting bed. Each tendon shall be marked at a fixed distance from the reference line so that slippage
can be measured as each tendon is detensioned. Tendon slippage exceeding 6 mm at the time of
detensioning shall be investigated and evaluated and all slabs on the bed shall be marked to identify the
tendon location and the position of each slab on the casting bed.
28.2.7.2.3
Tendon slippage shall be checked at the sawn face of slab ends. Tendon slippage exceeding 3 mm shall be
investigated and evaluated.
Note:
Tendons at the sawn face with no draw-in should be investigated to determine the level of prestress force in each of
them.
28.2.7.2.4
The manufacturer’s engineer shall evaluate the adequacy of all pretensioned products having tendons with
bond slippage exceeding the limits specified in
Clauses 28.2.7.2.2
and
28.2.7.2.3
.
29 Stripping and handling
29.1
Care shall be exercised in removing the elements from the forms. To prevent damage, initial lifting shall be
gradual and equipment for initial release shall have controls allowing such operation.
Note:
Intricate shapes can require special equipment during removal from the form through the use of compressed air,
vibration, hydraulic pressure, or screw jacks.
29.2
The minimum concrete strength, the number and location of lifting points for handling of elements, and
details of lifting devices shall be shown on the shop drawings. The number and location of the lifting
points shall be compatible with the method of shipping (i.e., flat or on edge).
29.3
Lifting equipment shall be properly secured to the element being stripped and handled. Proper rigging
procedures shall be documented and all lifting equipment shall conform to established safety practices.
29.4
All precast elements shall be handled in positions consistent with their shape and design. Care shall be
exercised to retain the required condition, quality, and appearance of all elements until finally installed.
Licensed for/Autorisé à Jed Friesen Sold by/vendu par CSA on/le June/18/2015.
~Single user license only. Storage, distribution or use on network prohibited. Permis d'utilisateur simple seulement.
Le stockage, la distribution ou l'utilisation sur le réseau est interdit.