REINFORCEMENT IN CONCRETE

In construction industry different structures are built, the built structures can be categorized with accordance to construction materials, here we can have steel structures, timber structures and concrete structures.

Concrete structures are the one which most of its structural parts made from concrete material, concrete is the most and widely used material due to its ability to be moulded into different shapes, and having wide range of characteristics (economical concrete of variety properties can be produced for different requirements).

Concrete has high compressive strength, that make concrete made structures to have high capability to withstand compression, cement concrete has low tensile strength that make it unsuitable for structures subjected to high tension.

Due to some weakness and properties of cement concrete, it is reinforced so as to produce a structure with required properties.

Concrete can be reinforced by different kind of materials in different ways per given analysis and design. 

The process of reinforcing the concrete can be done by using different materials such as steel bars, wire mesh and in some instances even bamboo is seen as the substitute of the steel bars for small projects.

The reinforcements inside the concrete has different functions so as to build the structure of desired quality per standard requirements. The following are functions of the reinforcement in different structures.

To improve Compressive strength

Concrete is very strong in compression, which exhibit the bending strength of the concrete which is 67% of the concrete characteristic strength-f_cu, then the moment resistance of the concrete has its limit so we need to provide compressive reinforcements to take over exceeded value.

The maximum moment resistance of concrete can be calculated as 0.156f_cubd ², whereby f_cu is the characteristics strength of the concrete, b and d are the breadth and effective depth of the structural member respectively.

The provision of the compression reinforcement reduces the size of compression member, since the compressive strength of the member is dependant to its size so instead of increasing its size we can simply provide compressive reinforcement.

Compressive reinforcement also increases the ductility of the member and reduces long term defection.

To provide Tensile strength

Concrete is very strong in compression but weak in tension, while reinforcing material such as steel, and bamboo are strong in tension weak in compression.

The reinforcing materials are also inserted into concrete structure to provide tensile strength into it against tensile stresses, so tension reinforcements should be provided where concrete structure experience tensile stresses (tension zone). 

To prevent Excessive Cracks

In mass concrete due to curing processes, temperature changes (freezing and thawing) , loadings cracks are formed.

Reinforcing of concrete controls number of cracks to be formed and extensive (thickness) of cracks as they hold concrete in their positions

So concrete can be reinforced mostly by using wire mesh or normal steels to to hold mass concrete so as to avoid excessive cracking.

To improve shear strength

Concrete of different grades has different shear capabilities, the shear capacity of the concrete is dependant to its characteristics strength-f_cu, when the shear capacity of the concrete is exceeded shear reinforcements or shear links are provided to take over the exceeding value. 

Shear links are known as stirrups in beams and ties in columns