Concrete has a natural weakness when tension is applied to it; pre-stressed concrete is a way of overcoming this weakness. The process of pre-stressing strengthens the concrete slab for architectural and structural use. This concrete undergoes predetermined engineering stresses and is, therefore, able to meet all the service-specific loads that are applied to it during construction.
How are such concrete beams made?
All the action takes place at the concrete plant. Pre-stressed tendons typically made from tensile steel cables or rods are embedded into the concrete. The addition of these tendons helps create compressive stress. This in effect acts as a balance to the tensile stress that the concrete otherwise experiences due to the bending load.
Usually, the tendon that is embedded into the concrete is first stretched across the casting bed and a mammoth 30,000 pounds or more of tension is applied to it before it is covered by concrete. The whole idea is to make this strand more resistant to downward pressure.
Difference between the normal concrete beam and a pre-stressed concrete beam
Pre-stressed concrete is pre-tensioned content with a high tensile tendon running right through it and therefore you can see that it has a slight arch, something that is not visible in ordinary concrete slabs. In this case all the energy of the concrete slab comes from the highly tensile steel that is placed inside the concrete; on the other hand, a concrete beam has to carry its own weight. The result is that it cannot resist the pressure of added loads, but a pre-stressed concrete beam has lots of strength left to resist added loads, courtesy the unit by the action of highly tensioned steel.
Benefits of Pre-stressed concrete
The fact that such concrete slabs are able to face a high degree of the load means they are used on the floors of high rise buildings. One of its high-value benefits is that it’s the major material used to build containment vessels of nuclear reactors.
Construction companies prefer the use of this type of concrete not only because they can withstand a lot of stress, but also because it is not susceptible to cracks. Pre-stressing leads to thinner slabs, which are usually used in high rise buildings, where lowering the thickness of the floors will decrease the number of joints, and lead to more floors; what is even more important is, lower construction costs. The last is a huge benefit and is one of the biggest reasons for the popularity of these concrete beams.
The construction industry is continuously on the lookout for new ways and means to improve the structural strength of buildings, but at the same time, it also wants to cut down on their construction costs. The use of new technology enables them to create concrete beams like pre-stressed concrete, which allows them to do both. There was a time in the not too distant past that newer ways of making concrete were looked at with suspicion. But today, with more and more contractors choosing to use concrete slabs manufactured with the best of technology, all doubts, and fears that anybody might have regarding them, have been allayed.