Brika Field Handling & Installation Guidelines
Hollow core slabs are extremely strong when support ed in their intended manner; however, they can be damaged if they are not handled and stored properly. It is understands the proper procedures as described herein to avoid damage and accidents due to mishandling.
If it is necessary to stockpile hollow core slabs on location, the following procedures are required:
- Ground bunks must extend the full width of the slab and be parallel and level to avoid warping and breaking of the slabs due to twisting.
- Ground bunks must be wide enough to prevent sinking into the ground, and high enough to avoid “high-centering” the slab. Contact with the ground could damage the slab.
- Bunks should be placed approximately 2 feet from each end of the slab.
- When several slabs are bunked in a stack, the intermediate bunks can be 2 x 6’s must run the full width, and each bunk must line up vertically.
- Do not stack the slabs more than 8 high, and then only if the ground is firm.
- Do not stack more than one slab above any previously erected slab in the structure.
Positioning of Lifting Device Along Panel Length
- It is absolutely necessary to lift the hollow core slabs near the ends of the slab as outlined in this brochure. Lifting the slabs too far away from the ends may result in immediate breakage.
- From the end of the slab, the edge of the lifting device should be 300mm minimum to 0.2 x slab length maximum, not to exceed 1800mm (Fig. 1).
Standard 600mm Wide Slabs (CTC Clamp)
- Brika supplied erection clamps with safety slings are recommended for use on standard 600mm wide slabs. DO NOT use clamps for slabs cut to a narrower width. Hooking into the end voids with any type of hook or grab bar IS NOT SAFE and could cause the slab to fail.
- When attaching the clamp to the slab, ensure the clamp is level, and that the protruding lip at the bottom of the clamp is gripping the shear key. Install safety slings immediately upon engaging clamps (Fig. 2).
- The clamps exert considerable pressure on the sides of the slab. To avoid crushing the slab, areas with block-outs must be avoided as clamping locations (Fig. 3).
- Persons electing to use the clamps and safety slings are required to pay a deposit, read the “Safety Precautions Statement”, and sign a release form. The deposit is refunded when Brika’s hardware is returned promptly and in good condition.
- Truck drivers delivering the hollow core slabs are not authoriszed to instruct in the use of these clamps. Field personnel are urged to visit Brika’s plant for a demonstration of these clamps to ensure their safe application. Contact the Brika Project Management Office for further assistance.
Narrow Width Slabs (Slings Supplied By Others)
- Use nylon slings for slabs less than 600mm wide.
- The use of wire rope slings is not advised (Fig. 4).
- A softener placed along the sawn edge of the slab should be used to avoid cutting the sling.
- Hooking into the end voids with any type of hook or grab bar IS NOT SAFE and could cause the slab to fail.
- Be sure that all bearing surfaces are clear of any rocks or other foreign objects which could damage the slab or prevent it from erecting level.
- Attach lifting device and hoist. At no time should personnel be underneath a hoisted slab.
- DO NOT disconnect the safety sling until the slab is close to its final erected position (Fig. 7)
- Pull the hollow core slab snug to the adjacent erected slab. Note: It is recommended that the location of slab joints, as shown on the shop drawings, be marked on the bearing area. This will allow the gauging of proper joint width and not overrun or undercover the prescribed area (Fig. 8)
- Pull the lifting clamps clear of the grout key after the crane lines are slackened (Fig. 9)
Once erected, the hollow core slabs form a safe platform for workers and normal construction tools (Fig. 10)
Avoid staging other heavy construction materials on the slabs. At no time should these materials exceed 450kg on a single slab or 680kg on any two adjacent slabs. Alternatively, allowable uniform loads on the bare slabs can be found in our Span-Load Charts.
GROUTING SLABS – Longitudinal Joint
The longitudinal grout joint is an important design feature of the hollow core system (Fig. 11) Proper grouting procedure is necessary to ensure full load sharing between adjacent slabs. Use a grout mix only in this joint, do not use concrete mix. If the engineer of record does not specify a grout mix, use the mix proportions below.
Grout for the longitudinal shear keys between slabs consists of a minimum of one part cement to three parts paving sand, by weight, with a maximum water content of five 20 litres per sack of cement. A grout strength of 20-25 mpa is generally adequate, unless otherwise specified in the contract drawings or in Brika’s shop drawings.
END CLOSURE CONCRETE – End Joint
In some cases, it is necessary to pour concrete in the ends of the slabs to integrate them with the supports. If the slabs receive a structural topping, these end closure pours may be done with the topping. However, if the slabs are untopped, a separate closure pour is required.
Brika supplies a dam (Fig. 12) for each void to help minimize wasteful flow of concrete into the slab. Care must be taken to avoid displacing the dam when using a vibrator. When the design calls for the closure concrete to extend beyond 18” into the slab voids, CTC will provide pour slots in the top surface to facilitate placement and vibration of the closure concrete.
One may also use polystyrene cutouts or foam fillers as necessary. Concrete for pouring closures at the ends of the slabs shall be proportioned per the engineer-of-record’s specifications for site cast concrete. Concrete mix strength shall be the greater of Brika’s requirement for “Void Fill” per the shop drawing, or the engineer-of-record’s requirement.