Concrete beam and slab reinforcement specifications should clearly indicate the cover to reinforcement, length of reinforcement, curtailment of reinforcement, and quantity and diameter of reinforcement to be given. The concrete producer can specify either bar or wire reinforcement. For uniformity purposes, it is recommended that all reinforcing be applied before casting the slab. The concrete producer may choose to apply strands at different heights to achieve certain strength characteristics in the finished product.
The reinforcement should be long enough to reach from one edge of the slab to the other, with at least 4 inches (10 cm) between each strand. Concrete producers often use more than one size of reinforcement for different types of slabs; for example, two sizes of wires might be used for a parking lot slab and four sizes for an airport runway.
The reinforcement should be as continuous as possible across any holes or voids that may appear in the slab. Any openings larger than 1/8 inch (3 mm) cause water to be able to penetrate the slab and enter these areas where it can cause corrosion of the reinforcement. Corrosion reduces the strength of the steel and must be repaired before additional cracking occurs.
Beam and slab connections should be made with high-strength bolts and washers. The washers should be large enough to fit over the heads of the bolts.
Reinforcement The main bar's coverage diameter 5. Designing a Concrete Slab Procedure Assuming adequate bearings (no less than 10 cm), calculate the span of the slab between the bearing centers. Assume the slab's thickness (take 4 cm per metre run of the span). Then, the total depth required is 12 times this figure (48 cm).
The reinforcement should be long enough to reach from one edge of the slab to the other, with at least 6 inches (152 mm) exposed for welding or nailing. Reinforcements must be accessible after the slab has been poured; they cannot be embedded in the mix.
Bar sizes range from about 1/4 inch (6 mm) 2 x 4s for small jobs to 1-1/2 inches (38 mm) for large ones. Bars are usually spaced 16 inches (40 cm) on center. For continuous reinforcement, like cable, the bars can be aligned either horizontally or vertically. For horizontal reinforcement, the slab needs to be deep enough to cover the entire length of the bar. For vertical reinforcement, the slab only needs to be deep enough to cover the first few inches of the bar and then the bottom surface can be flat.
The reinforcement should be placed before the concrete is added, since it will need to stay in place while the cement sets up.
Depending on the climatic conditions prevalent throughout the building's service life, the minimum needed cover thickness for slab reinforcement typically ranges between 20 and 30 mm. The 20 mm would be appropriate for a dry region, while the 30 mm would be appropriate for a beach area. Concrete covers this thick are used primarily on new construction.
As buildings age and their internal temperatures rise, it can cause their concrete to expand more than what is acceptable for good structural integrity. To prevent this from happening, old concrete should be covered with an expansion joint as it ages or if it shows any signs of movement (such as spalling) then new concrete should be poured over the old to create a smooth surface. This new layer of concrete should be at least 2 inches thick in order to properly reinforce the slab.
In some cases, where the underlying soil is not stable (such as clay soils), it may be necessary to add reinforcing bars within the original concrete cover to provide sufficient strength to support any additional floors that might be added in the future. For example, if a building has two stories added onto it over time, then reinforcements should be placed in the first floor concrete cover to ensure it will be able to support any additional weight that comes along with these additions.
Concrete reinforcement is accomplished by inserting deformed steel bars or welded wire fabric inside newly cast concrete. The goal of reinforcing is to give strength to concrete where it is required. Reinforcement can be used in new construction or to repair damaged concrete.
The two main types of concrete reinforcement are rebar and wire mesh. Rebar is metal that has been manufactured into a long beam shape for use as concrete reinforcement. Rebars are available in various sizes and strengths. They are usually painted red or black to make them visible during construction.
Wire mesh is woven metal fibers, typically aluminum, but also including stainless steel and copper. It is this material that makes up most of what you see when you walk on a reinforced bridge. Wire mesh comes in several different shapes and sizes based on how it will be used. For example, if you were to put wire mesh under a floor, it would be called subflooring. If you placed it around an object like a column or wall, it would be called cage block. Cage block is commonly used as interior concrete reinforcement.
Rebar is inserted into the wet concrete to provide structural support. The reinforcement should be deep enough to reach the bottom of the mold, but not so far down that it becomes difficult to insert. The deeper the bar, the stronger the concrete will be!
It is typically not essential to strengthen the concrete if the slab is set on a high-quality subbase that provides consistent support. However, reinforcing should be employed if the subbase is problematic or the space between the joints is larger than 15 feet. Reinforcing can also be useful if you expect the floor to experience heavy traffic or use it as a surface for any activity that could damage the slab itself.
The best option for strengthening concrete is to add rebar to the mix before pouring. This will produce a stronger and more durable slab that can hold up under heavier loads. Rebar is added to the concrete mixture to create a framework within which the cement paste sets into a solid mass. The steel bars are then covered with another layer of concrete to complete the process. Once the new concrete has cured (usually in one to three days), the reinforcement is visible as white lines running through the slab.
Rebar is available in different sizes and shapes depending on how much strength you want in your floor. The two main types are hollow and solid. Hollow bar is used when maximum compression strength is needed throughout the floor. It's best to have both thick and thin sections of hollow bar in the concrete to ensure even stress distribution during loading. Solid bar is used where weight savings are important so less bar is required. It's also recommended to have some solid bar in the floor to provide extra support where needed.