We are still discussing preparations for pouring the concrete for the building’s first floor, after the plumbing, electrical, and HVAC contractors have finished their work on the first floor. We must meet with each contractor to ensure that everything required and specified in the approved project plans has been installed. Additionally, the electrician must install 4-inch pipes in the exterior drop-down beams for the restrooms; These pipes are for the exhaust fans that will be installed in the ceilings as part of the interior design.
After ensuring that all contractors have completed their required work, the ceiling must be thoroughly cleaned, and all small debris—such as wood scraps, blocks, and the like—must be removed. It is preferable to use a compressed air blower to clean the ceiling and ensure that no small debris or dust remains, especially if the ceiling insulation is made of polystyrene, which produces some debris and small pieces after plumbing and electrical work. At the same time, the contractor must ensure the integrity of the rebar ties, as some electricians and plumbers may loosen some ties in order to finish their work.
Standard 350 kg/m³ concrete is used for the ceiling, or as per the project’s approved specifications. When the concrete pump arrives at the site the roof is thoroughly sprayed with water. Upon the arrival of the concrete transport vehicles, concrete pouring for the roof begins immediately, and care must be taken not to add water to the concrete—a practice often requested by many contractors to facilitate their work. There is no doubt that adding water to the concrete without specific proportions and without the guidance of an engineer or a qualified supervisor on site contributes to the weakening of the concrete.
The contractor begins by pouring concrete for the main and approach bridges first, with an emphasis on the use of a mechanical vibrator during the pouring process. The vibrator is used in all stages of pouring, starting with stairs, bridges, beams, and so on, without exception, to ensure there are no voids in the pour, a process known as "voids." It is preferable to have two mechanical vibrators on site so that one can be used as a backup. Upon completion of the pour, the concrete is immediately finished using a "finishing machine" to ensure the roof is completely level.
The roof concrete is sprayed with water after three to four hours, provided that the water is sprayed lightly, like rain, and then the spraying continues for seven consecutive days at a rate of twice daily. The contractor removes the roof formwork—the wood surrounding the roof from the outside—after one to two days or as directed by the supervising engineer.
The roof formwork is removed fifteen days after the concrete is poured in the summer, and in the winter, twenty-one days after the concrete is poured. This varies depending on the roof area, and it is usually recommended to seek guidance from the supervising engineer or follow the approved project specifications.
