The ratio of sand, stone, and cement used in the construction of flyover bridges is usually M:35 for pile, M30 for pile cap, and pier.
Clear cover to any reinforcement shall be 75mm for pile and pile cap; and 40mm for the pier.
There is no particular ratio of sand, stone, and cement in the standard code to be used in the construction of the flyover bridges.
As per Indian Codes, the nominal grades are only till M 25 which means the ratio of sand, stone, and cement are in proportions of 1:1:2.
Therefore for any major construction like flyover, it is recommended to test the concrete mix for its strength and durability.
But in most cases after the test it is found that the ratio of sand, stone, and cement used in the construction of flyover bridge comes out to be 1:1:2
So, the main rule is that the compressive strength of the mixture after 28 days should not be less than 53MPa.
In the ratio of sand, stone and cement the cement should be OPC (ordinary portland cement).
OPC cement is Highly durable and sound concrete due to the very low percentage of alkalis, chlorides, magnesia, and free lime in its composition.
Almost negligible chloride content results in restraining corrosion of concrete structures in hostile environments.
53mpa is very widely used in areas where there are higher compressive strength requirements and as such used in flyover bridges
Concrete Grade Mix Ratio (Cement : sand :aggregates)
Components of flyover bridge :
Span:
The distance between two bridge supports, whether they are columns, towers, or the wall of a canyon.
Beam:
A rigid, usually horizontal, structural element.
Pier:
A vertical supporting structure, such as a pillar.
Pier Cap:
It is a component that transfers the load from the superstructure to the piers.
Abutment:
A structure to support the lateral pressure of an arch or span. E.g. at the ends of a bridge.
Bearings:
A bridge bearing is a component of a bridge that connects the piers and deck.
Approach Slab:
It provides a transition between the roadway pavement and the bridge.
Parapet:
A low protective wall along the edge of the bridge.
