A molded layer of plain or reinforced concrete, flat, horizontal (or nearly so), usually of uniform but sometimes of variable thickness, and supported by beams, columns, walls, other framework, or on the ground.
It provides a covering shelter or working flat surface in buildings. Its primary function is to transfer the load by bending in one or two directions. The upper slab becomes the ceiling for the storey beneath it.
In general, 6 inch (150mm) slab thickness is considered for residential and commercial buildings with reinforcement details as per design.
The concrete slab construction process includes the preparation of formwork, compaction of a slab bed, placement of reinforcement, pouring, compacting, finishing the concrete, removing formwork and curing the concrete slab
Concrete Floor Slab Construction Process
1. Assemble and Erect Formwork for Slab
The formwork shall be designed to withstand construction loads such as fresh concrete pressure and weight of workers and operators and their machines. Guide to Formwork for Concrete ACI 347-04 shall be followed for the design of formworks. Moreover, there are various construction aspects that need to be considered during the erection of formworks. For example, it should be positioned correctly, lined and levelled, joints sealed adequately, and prevent protruding of nails into the concrete etc… Furthermore, different materials such as wood, steel, and aluminum can be used for the formworks of concrete floor slab.
2. Prepare and Place Reinforcement for Slab
Prior to the placement of reinforcement for concrete floor slab construction, inspect and check forms to confirm that the dimensions and the location of the concrete members conform to the structural plans. Added to that, the forms shall be properly cleaned and oiled but not in such amount as to run onto bars or concrete construction joints. Design drawings provides necessary reinforcement details, so it only needs understanding to use designated bar size, cutting required length, and make necessary hooks and bents. After preparation is completed, steel bars are placed into their positions with the provision of specified spacings and concrete cover. The concrete cover and spacing for floor slabs can be maintained by introducing spacers and bars supporters. Wires are used to tie main reinforcement and shrinkage and temperature reinforcement (distribution reinforcement).
3. Pour, Compact and Finishing Concrete Floor Slab
Mixing, transporting, and handling of concrete shall be properly coordinated with placing and finishing works. In floor slab, begin concrete placing along the perimeter at one end of the work with each batch placed against previously dispatched concrete.
Concrete should be deposited at, or as close as possible to, its final position in order to prevent segregation. So, Concrete placement in large and separate piles, then moving them horizontally into final position shall be prevented. Moreover, site engineer shall monitor concreting properly, and look for signs of problems. For example, loss of grout is the indication of improper sealing and movement of joints. Added to that, cracking, excessive deflection, level and plumb, and any movement shall be checked and tackled to prevent further problems.
4. Curing Concrete and Remove Formwork
After finishing ended, suitable technique shall be used to cure the concrete adequately. Slab curing methods such as water cure; concrete is flooded; ponded; or mist sprayed. In addition to water retaining method in which coverings such as sand; canvas; burlap; or straw used to kept slab surface wet continuously, chemical Membranes, and waterproof paper or plastic film seal. Regarding curing, it is recommended to remove formworks after 14 days. For detailed formwork removal time.
