What is Lightweight Concrete?
The bulk density of ordinary concrete is around 2300 kg/m3. Concrete having bulk density between 500 to 1800kg/m3 is known as lightweight concrete (LWC). A higher compressive strength of 7000 to 10500 psi may be attained with this concrete. Which may reduce the density of mixture as its requires the higher pozzolans and water reducing admixtures to the concrete.
Material Used For Preparing Lightweight Concrete:
- Binding Materials,
- Aggregates,
- Steel,
- Water.
1.Bending Material:
Ordinary portland cement and its varieties can be used as binding material. If natural binding material such as lime-slag, lime-cinder, etc. is available, the same can also be adopted as binding material.
2.Aggregate:
For LWC, loose porous materials are used as aggregates. Natural porous aggregates are obtained by crushing lightweight rocks. Artificial porous aggregates can be obtained from industrial wastes.
3.Steel:
LWC, is highly porous and hence, it leads to corrosion of reinforcement, if not properly protected. Hence LWC should be made or adequately dense when used for R.C.C. work. Sometimes or the reinforcement is coated with anti-corrosive compounds when LWC is adopted.
4.Water:
It is necessary to use pure drinking water to prepare LWC. The strength of lightweight concrete mainly depends on the amount of water in the mix. The Water-cement ratio for achieving optimum strength of LWC should be carefully worked out. As water content reaches its optimum value, there is a corresponding increase in the strength of lightweight concrete.
Types Of Lightweight Concrete:
- Aerated or Formed Concrete,
- No-Fines concrete.
1.Aerated or Formed Concrete:
This type of lightweight concrete is also called gas concrete or foamed concrete because it was developed by introducing large voids into the mortar or concrete. Voids are usually injected via a chemical reaction or an air-entering agent.
Inflatable or foam concrete does not need to be flattened, exhibits optimal thermal insulation, and self-compresses. It is ideal for hard-to-reach areas and drainage systems.
2.No-Fines concrete:
This type of concrete is developed by removing fine aggregates from the mixture; The concrete result consists of large voids and coarse aggregates. This is why no-fines concrete has good insulation and reduces drying shrinkage.
No-fines are best suited for concrete load-bearing walls and can be used for indoor and outdoor construction. However, this type of lightweight concrete should not be used with reinforced concrete, especially due to its low density and cement content.
Advantages Of Lightweight Concrete:
- Local industrial waste, if found suitable for lightweight concrete, can be economically utilized.
- The reduction in weight of concrete helps easy removal, transport, and erection of pre-cast products.
- The use of lightweight concrete results in the reduction of cost to the extent of about 30 to 40% or so.
Application Of Lightweight Concrete In Practical:
- One of the most popular structures made of lightweight concrete, the Bank of America Building in Charlotte, NC shows how LWC can be used to build exceptional structures, especially if the dead load is too low to pass from one floor to the next.
- LWC is ideal for building additional flooring on old or new structures because it reduces the risk of collapse. Similarly, it can be used to build bridges, decks, girders, piers, precast structures, and high-rise buildings with low density. For example, the use of LWC at the Wabash River Bridge allowed builders to reduce project density by 17%.
- Due to LWC’s low thermal conductivity and high heat resistance, it is now commonly used to insulate water pipes, walls, and the top of roofs. It protects the steel from corrosion by forming a protective layer, which also works to insulate the steel structures against decay. LWC is commonly used to build interstate and traffic lanes without adding dead load to existing structures.
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