Site Preparation And Erection Work
1. Coordination
2. Columns
3. Beams
4. Beams along the hollow core slabs
5. Procedures in erecting of hollow core slabs
6. Grouting slab key way
7. Temperature steel/steel wire mesh
8. Concrete topping
1. Coordination
The contractors should issue the construction plan and schedule to the hollow core slab Producer as early as they can. The erection coordinator will comment on the contractors’s Schedule and recommend the necessary method to accomplish the erection work and solve all the problems before hand. The contractors should provide strong access for the mobile crane and trailers.
Clear all the debris and construction materials, which they will obstruct the erection work. The final appointment should be confirmed 3 days In advance.
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2. Columns
During hollow core slabs are erected on the appointed area. The erection crews have to work with great care to prevent the cast in place columns damaged while they are erecting the slabs. Some time, Columns are damaged accidentally, example they are hit by hollow core slab or boom of crane. Stater bars protuded from the below columns are highly recommended to solve this problem, beside it will facilitate the erection work and minimize the erection time.
Remarks : Average erection rate for hollow core slab is 400 m2/day.
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3. Beams
Beam should be in alignment with the tolerances of ±2 cm.
Top finish of beam should be smooth and have the correct level.








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4. Beams Along The Hollow Core Slabs Beams along the hollow core slab should be in the correct alignment. Reinforcement in the direction of hollow core slab should be in a good arrangement. The clear spacing of 2 cm between beam and hollow core slab is necessary.
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5. Procedures In Erecting of Hollow Core Slab
(1.) Erection coordinator will examine and recheck the quality of finish surface of beam, the obstruction To the erection work, the access etc, one day before the appointment.

(2.) On the erection day, hollow core slabs are delivered by trailer or lorry and unloaded by crane, Each hollow core slab is laid on the designed location with the sufficient seating length. Steel shear key are welded (option) and inspected thoroughly. After the final acceptance, mortar grout at key way of hollow core slab should be done as soon as we can to prevent all the debris collect in key way.

(3.) Temperature steel or steel wire mesh as designed are fixed on top surface of hollow core slab. Concrete, f’c strength at less 210 kg/cm2 cylinder sample at 20 days, is placed to the designed thickness as the composite layer. The quality of finishing of surface should be treated as required.

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6. Grouting slab key way
For good distribution of load between two adjacent panels, mortar grout at slab keyway should be applied. The recommended proportion of mortar is 1 part of cement : 4 part of sand by volume.



Grouting procedure
1. Clean all the debris from the slab keyway.

2. Damped the concrete slab at the keyway with clean water.

3. Fill mortar into the keyway and consolidate the mortar with steel bar or trowel. Smooth the top surface of mortar by trowel. We recommend to clean, all the mortar flow from the keyway, the sofit of keyway and make a good finish simultaneously.

4. In case of roof slab, grouting should be done with in 30 minute before we place the concrete topping, for the better performance in protect the water leaking.

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7. Temperature steel/steel Wire Mesh

After the grouting of slab keyway, the surface of hollow core slab should be cleaned and free from oil. Temperature steel or steel wire mesh as designed will be laid on the hollow core slab surface be fore cast the topping concrete.

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8. Concrete topping

Before placing the concrete topping, the concrete surface should be saturated with water and all of the excess water should be removed. Low slump concrete are placed and consolidated to the designed level. Before concrete setting ,the skill labours should examine the quality of surface finish and check all the cracks because of the shrinkage of concrete. We can minimize the cracks or prevent the shrinkage cracks of we work with great awareness.
Concrete topping for roof slab
Roof slabs are always exposed to the rain, hot and cold climate. To place the topping concrete on roof slab should be done with care to prevent any cracks appear on concrete surface. We would like to recommend the special procedure and design for a good performance roof slab as following.
1. The thickness of topping concrete of roof slab should be thicker than 5 cm. And the concrete finishing should have the gradient to control the direction of water flow.

2. The topping concrete should add the water proofing additive and we should use low slump concrete.

3. Temperature steel or steel wire mesh should have a closer spacing , instead of 20 x 20 cm.# we use 15 x 15 cm.# , and lay close to the top surface as much as possible (problamly 2 cm)

4. Grouting mortar (see grouting, 6)

5. Always cure the concrete.

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