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Hollow-Core Usage Manual

1) Hollow-Core Slabs have to be installed one floor at a time. Hollow-Core Slabs installation team will be able to install the slabs once the beam work of each floor is complete. Upon completion of Hollow-Core installation of each floor, the contractor can proceed with beam construction on the following floor. The contractor should not manufacture the adjacent upper floor beams ahead of time until the lower floor installation is complete.  This is due to the possibility of the buildings’ beam measurements changing once the hollow core is fully installed.  A slight change in the beams measurement might cause the Hollow-Core panels to misalign. In addition, this misalignment can damage the Hollow-Core panels. 
Remark: In general, we can install up to approximately 400 square meters per day if we do not encounter construction site problems.  

Storage and Preparations

 2) Once construction planning is complete, the contractor shall submit construction drawings, installation schedule and designated position for Hollow-Core panels to be installed. The contractor shall provide adequate space for Hollow-Core truck and crane on installation day. The storage area and designated install position should be of minimal proximity to each other. Special roads are required to be paved in order to support the weight of the Hollow-Core delivery trucks and cranes. The installation area will need to be kept clear of obstructive and unnecessary objects. 
The contractor will be required to prepare a proper designated storage area for the Hollow-Core at least 2 days prior to delivery. The contractor shall inform the installation team of a delivery schedule at least 3 days prior to the desired date.
 
3) Beam preparation for the Hollow-Core
– Beam must be aligned correctly with an error allowance of +/-2 centimeters
– Beam level must be positioned correctly according to the proposed plan
– The bearing surface of the beam must be smooth and leveled. The contractor may use a margin trowel to smoothen the beam’s surface. 
 
4) The bearing surface of the beams supporting the hollow-core panels must be built according to the design and must have a smooth and clear surface (they must be free of any debris and foreign objects.) 2 centimeters of extra space between the hollow-core panel and the adjacent vertical surface of the beam is recommended to ensure a proper fit. 
 
5) Hollow-Core placement 
– Once the Hollow-Core panels are placed in their proper positions, the contractor must inspect, clean and make any needed adjustments to prevent cracks in the panels.
-Shear Key must be welded prior to grouting to prevent unnecessary debris and objects from accumulating in the area. 
-Place a 6 mm wire mesh with a #0.20m gap on top of the Hollow-Core panel before concrete topping in accordance to a 1:2:4 ratio. The compressive strength of the concrete should be no less than 240 kg/square meter. A margin trowel may be used to smoothen the topping surface. 
-After the topping concrete is poured, it must be cured for at least 24 hours. 
6) Grouting (To be completed by the contractor)
 
Step 1 Vacuum and clean the joints of debris. 
Step 2 Mix the grout according to its proper instructions.
Step 3 Load and apply the grout using the grout float.
Step 4 Spread the grout properly and ensure all open cavities are filled.
Step 5 Clean off excess grout
Remark: In the case of the rooftop floor, grouting should be completed 30 minutes before topping.  This will ensure that the mortar will properly fuse with the topping concrete.
 
7) Wire Mesh placement
After Hollow-Core panels are placed and grouting is completed, the contractor shall clean unnecessary objects before place the wire mesh or steel support prior to pouring the topping concrete. 
 
8) Concrete Topping 
 
After the wire mesh is placed in accordance to the design specifications, water may be used to clean unnecessary debris prior to pouring the topping concrete. 
 
9) Special concrete topping procedure for the rooftop floor
The rooftop floor’s direct exposure to sunlight and rain (its exposure to sudden temperature fluctuations) can cause the concrete to crack. The contractor shall follow the following procedure before pouring the topping concrete to prevent such cracking from occurring.
 
The topping concrete and water proofing material should me mixed and poured together in a thicker than usual consistency. The thinnest part of the topping concrete should be no less than 5 centimeters thick. Low slump should be use to alleviate cracks on concrete’s surface. In addition, more steel support on the topping concrete should be used. The contractor should take precaution when placing the steel support near the concrete surface because temperature fluctuates most on this outer concrete layer. The distance between the steel support and the concrete surface should be no less than 2 centimeters. 
Mortar should be filled in no more than 30 minutes prior to the addition of the topping concrete. Make sure the topping concrete does not flow into any of the hollow-core gaps. 
The slope should be correctly adjusted to prevent water from seeping into the hollow-core gaps. 
Curing the concrete every 7 days is necessary