What is a bond beam?
A bond beam is a horizontal structural element usually found embedded on the top of the masonry wall. The bond beam provides horizontal strength to the wall. It is provided at about 4 feet to 6 feet above the plinth level and below the tie beam between the masonry wall.
When to provide bond beam?
The bond beam should be provided in masonry walls when the ratio of the height of wall to the width of the wall is greater than 12. This ratio is called the slenderness ratio.
Slenderness ratio = Height of wall/Width of wall
When we provide a bond beam between walls then the height of the wall is distributed and the slenderness ratio becomes less than 12.
Purpose of bond beam in masonry wall
- It improves the lateral strength of the wall.
- It breaks the continuity of the wall height and prevents the lateral weakness of the wall.
- If there are cracks generated in the wall due to an earthquake or any other sudden load, then the bond beam acts as the breaker of wall cracking.
- It provides consistency in anchorage for floor or roof structures.
Bond beam dimensions/bond beam sizes
A bond beam is provided at the height of 4 meters to 6 meters above the floor of the wall.
The depth of the bond beam should be a minimum of 5 inches i.e 127 mm. The width and length of the bond beam should be the same as the width of the brick masonry wall. If we provide horizontal reinforcement in the bond beam then it will be strong enough to bear tensile stress as well.
Reinforcement in Bond Beam
The minimum longitudinal steel rod along the length of the bond beam should be 2 at the bottom of the bond beam. If we provide four steel rods then we can provide them at the bottom as well as at the top of the beam.
The minimum diameter of steel rebar that can be used for the bond beam is 10 mm. and stirrups can be used of 8 mm in diameter. Spacing between stirrups used in the beam should be between 150 mm to 250 mm.
The grade of concrete used in the bond beam should not be less than M15 in the case of red bricks and M25 if we are using AAC Blocks.
How to install bond beam block?
- At first, we have to provide shuttering of plywood or any metal along the wall on both sides of the wall.
- The shuttering should be tied with the help of iron wire and a prop should be installed if necessary.
- The shuttering should be provided up to the depth of the bond beam required and up to a column in length.
- After that provide the steel reinforcement along the bond beam and ties with the help of stirrups.
- Finally pour concrete into the formwork with proper compaction with the help of a tamping rod. Proper curing should be done for at least 10 days to 14 days after casting of concrete in formwork for bond beam.
Can a bond beam be unreinforced?
Concrete is strong in compression and weak in tension. So, Since the bond beam generally carries the compressive load, it is not too necessary to provide steel rods. But if the thickness of the bond beam is less and the height of the wall is more then steel should be provided in the bond beam.
How does bond beam work?
A bond beam is a horizontal member which carries a load above it and distributes uniformly below the plinth beam. The strength of concrete is more than the strength of the masonry wall.
So, whenever there is a crack in the upper or lower portion of the wall then it resists the crack to travel through the concrete and prevents the wall from full damage or collapsing.
How far can a bond beam span?
Actually, the bond beam is provided up to the end of the wall between the column. But if we have a length of wall more than 15 feet then we can provide the expansion gap between the wall if it is a compound wall but concrete bond if it is the interior wall of the building.
How to fix bond beam cracks?
Cracks in bond beams can be fixed with the help of pressuring mortar or cement slurry between the crack of concrete. However, it will not get its original strength but will be able to carry the appropriate compressive load on it.
Bond beam vs tie beam
The difference between bond beam and tie beam are given below.
|S.N||Bond Beam||Lintel Beam|
|1.||Bond beam is provided between the masonry walls.||Lintel beam is provided just 1 feet or 2 feet below the slab beam.|
|2.||Bond beam provide strength to the masonry wall.||Lintel beam tie al the coloum of the building.|
|3.||Bond beam may not contain reinforcement.||Lintel beam must contain reinforcement.|
|4.||Bond beam generally provided below opening like window.||Lintel beam are provided above the opening like window and doors.|
Bond beam concrete block / cmu bond beam block
A bond beam concrete beam is the concrete block in which a gap is maintained to pour concrete and reinforcement in it. Concrete blocks are made of the same width as the concrete block with which we construct the wall.
But the difference is that there is hollow along the length of the block so that we can pour concrete and reinforcement to provide extra strength to the masonry wall.