What Is Roller Compacted Concrete?
Roller compacted concrete is a type of concrete which contains the same ingredients as traditional concrete. The proportions of ingredients may not be the same as the conventional concrete. In addition to the common ingredients, fly ash is added as a partial replacement for Portland cement.
When roller compacted concrete is in its unhardened state, the consistency of its slump is somewhat stiﬀer than conventional concrete. So that it can withstand the vibration given to it for its complete compaction.
It is placed in layers of approximate thickness of 20cm to 30cm each. Placing the concrete in layers allows the full compaction of concrete. When the concrete is fully compacted, the properties like destiny, strength, texture, etc. are achieved satisfactorily.
Roller compacted concrete is economically cheaper, as it can be used without formwork. Also, it does not require finishing. The main requirements while using the concrete are durability, economy, and strength. Roller compacted concrete fulfills all three requirements, stated above.
Roller compacted concrete contains the same raw materials or, say, ingredients which are present in the conventional concrete. But their proportion is diﬀerent from conventional concrete. In addition to cement, fine aggregates, coarse aggregates, and water, fly ash is also added as a partial replacement to Portland cement.
Sometimes, diﬀerent types of chemical admixtures like water reducers, retarders, accelerators, and superplasticizers are also added to the mixture to form concrete with required and special properties. The amount of chemical admixtures in roller compacted concrete is higher as compared with the traditional concrete.
Properties Of Roller Compacted Concrete
The compressive strength of roller-compacted concrete ranges from 4000psi to 6000psi which is similar to that of conventional concrete. But some structures have also yielded compressive strength exceeding 7000psi also. This is due to the low water-cement ratio. The low water-cement ratio helps concrete in achieving high compressive strength.
The flexural strength of roller compacted concrete can be achieved between 500psi to 1000psi. Flexural strength has a direct relation with the density and compressive strength in this concrete.
Roller compacted concrete is poured in layers. A layer of approximate thickness of 20cm to 10cm is placed and then it is compacted. Again the same procedure is followed for the next layers. These layers must have a strong bonding with each other. A suﬃcient bond strength is achieved only when the concrete layers are thoroughly bonded with each other.
Due to lower water content, this concrete usually has lower shrinkage and crack formation as compared to conventional concrete.
- Versatility, and
- Resistance to freezing and thawing
Roller compacted concrete is used for
i) Concrete pavements for roads, streets and highways as well.
ii) Construction and rehabilitation of concrete dams, ports, airports, storage facilities, parking lots
iii) Construction and maintenance of light and heavy industrial facilities.
i) It is strong and durable due to less water content in its mixture.
ii) Reinforcement bars are not required in the construction of a concrete element using this type of concrete.
iii) It does not deform when heavy loads are applied to it.
iv) It proves to be a cheaper option when compared with conventional concrete.
v) Resistant to oil spills, fuels, hydraulic fluids, and other such liquids.
vi) It gives a smooth finished surface.
vii) The consumption of cement in roller compacted concrete is lower due to the use of fly ash which is a partial replacement of cement.
viii) It is capable of resisting high temperature.
i) Although the dams are eﬃciently designed and constructed using this concrete when compared with other low-cost options of dams, it might turn out to be more expensive in some situations.
ii) Sometimes leakage may occur in the dams if compaction is not done properly.
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