The concrete slab is basically a two-dimensional bending member (beam is a one-dimensional bending member) which is designed for bending, shear and torsion at the corners.
Generally, it is horizontal and has a smaller thickness comparative of its span, also one of the most efficient members in a structure.
Here we will learn about concrete slab, types of concrete slab & much more.
Introduciton to concrete slab:
Concrete slabs are used to furnish a flat and surface in a reinforced concrete structure, it is a flat piece of concrete, put on the walls or columns of a structure.
There are two types of slabs, one-way or two-way:
Slabs that are mainly deflected in a single direction are known as one-way slabs.
When slabs are usually supported by columns organized in rows, so that the slabs deflect in two directions are known as two-way slabs.
Concrete slab construction methods:
- Formwork construction shall be designed to withstand concrete loads such as the fresh concrete pressures, weights of workers and operators and their machines.
- In addition, there are numerous construction elements that have to be considered in the course of the construction of the formwork.
- For instance, it needs to be accurately lined and levelled, joints should be adequately sealed and nails should unfold in concrete.
- Additionally, numerous materials such as wooden, metal and aluminium can be used for the formwork of concrete floor slabs.
- Lastly, there are several common formwork construction deficiencies, site engineer should know and prevent their incidence in any other case a formwork failure might occur.
Prepare and placement of reinforcement for concrete slab:
Before placement of reinforcement for concrete flooring slab construction, check the varieties and ensure that the placement of the concrete members conforms to the structural plans.
With this, the varieties might be totally cleaned and oiled, however not so much as to run on bars or concrete construction joints.
Design drawings provide the required reinforcement details, so it solely requires understanding to use the specified bar size, so cut the required size and making the required hooks and bents.
After the preparation is complete, metal bars are positioned in their place with specified spacing and provision of the concrete cover.
Concrete cover and spacing for flooring slabs may be maintained by introducing spacers and bars, supporters.
The wires are used to tie the main reinforcement, shrinkage and temperature reinforcement (distribution reinforcement).
It should be known that incorrectly reinforced steel placement could cause critical concrete structural failures.
Improper concrete cover exposes the reinforcement straps at risk and endangers the concrete steel bond.
Finally, after all the requirements for reinforcement placement are finalized, then the site engineer can order concreting.
Pour, Compact and Finishing Concrete Floor Slabs:
The mixing, transport and handling of the concrete shall be properly coordinated with insertion and finishing works.
In-floor slabs, start inserting concrete alongside the perimeter at one end of the work with each batch, positioned against the previously shipped concrete.
Concrete slab must be deposited as near as possible to stop segregation, so concrete placement in large and separate piles will be prevented from shifting them horizontally to the final position.
The site engineer will monitor the concreting properly and search for defects, i.e., loss of grout is an indication of improper sealing and movement of joints.
Also, fresh concrete must be sufficiently compacted so that it can be molded within forms and surrounding objects, reinforcements and eliminate stone pockets, honeycomb and air.
internal or external vibrations is the most widely used method for reinforcing concrete.
Finally, slabs can be eliminated in many ways depending on the application of the floor.
Curing of concrete and removing formwork:
Once surface is finished, the appropriate technique will be used to fix the concrete.
Methods of treating slabs such as water curing: concrete slab is filled, ponded or mist sprinkled.
In addition to the method of retaining water in which casing such as sand, canvas, burlap or straw is used to keep the surface of the slab wet continuously with chemical membrane and waterproof paper or plastic film sealed.
Regarding curing, remove the formwork after 14 days is recommended.
These manufacturing deficiencies are given below:
- Poor or deficient formwork examination during and after concrete placement to identify unusual deflections or other indications of potential failure that can be corrected.
- Inadequate nailing, bolting, welding, or fastening.
- Improper lateral bracing.
- Construct formwork that does not comply with form drawings.
- Lack of proper field inspection to ensure the form design is correctly interpreted by the form of builders.
- Using less damaged or inferior strength.
A concrete slab that undergoes bending from one support to another causes tension at the bottom of the slab and compression at the top.