Reinforcement Steel
To reinforce a material means to add something to it, in order to make it stronger.
One of the strongest reinforcement materials available is steel or iron. in reinforced concrete, a concrete member is strengthened with steel bars or metal netting embedded in it.
TYPES OF REINFORCEMENT STEEL
There are various types of reinforcement steel; how they are used depends on the function, shape and dimensions of the reinforced concrete member as well as on the repaired strength.
Reinforcement steel is classified according to its shape and surface texture. The most common reinforcement is single round bars which can have either a smooth or a ribbed surface.
CIRCULAR BARS:
Round, smooth bars are called circular bars and are available in diameters ranging from 5 mm to 28 mm (Fig. 1). The four sizes most often used in Rural Building have diameters of 6 mm (1/4"), 10 mm (3/8"), 12 mm (1/2") and 18 mm (3/4").
RIBBED BARS:
The round bars with a ribbed surface are called ribbed bars and are available in diameters ranging from 6 mm to 40 mm, if the bar is cross-ribbed (Fig. 2). For obliquely ribbed bars, the diameters range from 6 mm to 28 mm (Fig. 3). This last type of reinforcement is also called "tentor bar" and it is the strongest reinforcement steel available.
The standard length of reinforcement bars is 9 m.
ADVANTAGES / DISADVANTAGES:
Although the strength of circular bars is sufficient for all Rural Building purposes, it is advisable to purchase ribbed bars if they are available in the market. Ribbed bars are preferred because their rough surface texture provides a better grip to the concrete. This, along with their greater strength, allows the Rural Builder to space the ribbed bars wider apart, thua saving materials and reducing the total weight of the member.
REINFORCEMENT MATS
A variety of reinforcement mats are available. They are usually made out of two layers of reinforcement bars laid across each other and secured together by welding.
The mats are either square or oblong in shape. They reduce the work needed to reinforce large members of the structure such as floors, walls, slabs, etc.
Regular reinforcement mats are hardly necessary in Rural Building, but two special kinds are frequently used for burglar proofing and to reinforce thin concrete slabs like manhole covers, draining boards in kitchens, and coping slabs.
These two are "expanded metal fabric" and "steel wire netting".
STEEL WIRE NETTING:
The most common steel wire netting {Fig. 4) has square meshes measuring 5 by 5 cm and is manufactured in the same way as reinforcement mats. The same kind of wire mesh can also have oblong meshes.
EXPANDED METAL FABRIC:
This is made by slitting metal sheets and then stretching them to form a diamond-shaped mesh (Fig. 5). Always wear leather gloves when working with expanded metal fabric, as the edges are very sharp.
Reinforcement mats are sold in sheets approximately 2,15 m wide and 5 m long.
Expanded metal fabric and steel wire netting can be purchased in sheets of about 1,5m wide and 2,5 m long.
BINDING WIRE
This is a soft steel wire about 1 mm in diameter, used for binding reinforcement bars at the points where they cross each other. It is bought in rolls and may also be called lashing wire, annealed wire or tying wire.
