A masonry structure is one made by joining (bonding) multiple numbers of building blocks ( like brick, stone, block, etc) usually with cohesive material called mortar. These activities are known as brick masonry work.
The masonry may be mud mortar, cement mortar, etc. Sometimes based on requirements dry masonry is also built without any mortar.
Different types of masonry structure
- Burnt clay bricks
- Sand lime bricks
- Laterite stone
- Granite stone
- Concrete block: Hollow (25% – 50% cavity)
- lightweight Autoclaved Cellular
- Burnt clay hollow bricks
- Gypsum Partition Blocks
- Stone rubble
Advantages of Masonry Structure
- Strength: Masonry structures are strong in compression
- Heat Absorber: It resists temperature fluctuation
- Maintenance-free: Most of the walls do not require painting
- Fire Resistant: Fire protection due to the formation of non-combustible material
- Masonry structures are environmentally friendly
- It is used for great soundproofing
- Masonry units can be prepared by the use of locally available material
- It is Economical
Disadvantage of Masonry Structure
- Moisture Absorber: Absorbs moisture when raining
- Color Deteoration: Extreme weather causes masonry to degrade material such as wall surface decolorize due to frost damage
- Strength: Masonry structures have a low tensile strength
- Opening: Become weak while creating a large opening
- Education: Lack of education in masonry
- Need heavy foundation: A large foundation is required due to its heavy weight. Cracking and settlement may occur due to heavy load.
Construction Technology of Bricks
Size And Weight Of Brick
(a) Bricks that are not standardized are called traditional bricks. If the bricks are large it is difficult to burn them properly and they become too heavy to be placed.
(b) On the other hand, If bricks are small, more quantity of mortar is required.
(c) Hence, BIS ( Bureau of Indian Standards) has recommended bricks of uniform size, called modular bricks and the actual size is 190mm*90mm*90mm. If the thickness of mortar is included then it is called the nominal size of a modular brick and the size is 200mm*100mm*100mm.
(d) It is found that the weight of 1m3 of brick earth is about 1800kg. Hence, the average weight of a brick will be about 3 to 3.5kg.
(e) NBC (Nepal Building Code) has recommended the standard size of brick as 240mm*115mm*57mm with 10mm mortar in length side.
Basic terms in Masonry:
- Course: Horizontal layer of bricks/ stones
- Bed: Lower surface of bricks/ stones in each course which is perpendicular to line of pressure
- Backing : Unexposed wall
- Facing : Exposed to weather
- Hearing : Between backing and facing.
- Header : Face of brick when the length is perpendicular to the face of the wall
- Stretcher : Face of brick when the length is parallel to the face of the wall
- Bond: Individual brick units are tied together with mortar is called a bond.
- Closer : A piece of brick obtained after cutting a brick across its width.
- Soldier: Laid vertically with the long narrow side of the brick exposed.
- Soilor: Laid vertically with the broad face of the brick exposed.
- Rowlack: Laid on the long narrow side with the short end of the brick exposed.
- Bonding in Brickworks:
- Bonding is the method of arranging the bricks in courses so that individual units are tied together and vertical joints arranging the bricks in courses so that individual units are tied together and vertical joints of successive courses do not lie in the same vertical line.
- The unbounded wall has less strength and durability.
Consideration in Brick Masonry
- The lap should be minimum 1/4th brick along the length of the wall and ½ brick across the thickness of the wall.
- Bricks bats should be discouraged, except in special locations.
- The vertical joint in the alternate courses should be along the same perpend.
- The brick should be of uniform size.
- All the finished masonry walls should be cured for at least 7 days.
- The thickness of the mortar joint should be uniform and not more than 13mm in any case.
- The height of brick masonry in one day should not exceed 1.5m.
Types Of Brick Bond:
Stretcher Bond: This bond is formed when a stretcher of bricks is laid along the face of the wall, used in the partition wall.
1) Header Bond
This bond is formed when the head of bricks is laid along the face of wall. ¾ bat is provided in each alternative course in corners. Unsuitable for load-bearing structures.
2) English Bond
It consists of alternative courses of header and stretchers. Queen closer after header in each heading course.
3) Flemish Bond
In this type of bond, each course is compressed of alternative headers and stretchers. Every alternate course starts with the header at the corner. Quron closer is placed next to the queen header in alternate courses to develop face lap.
4) Facing Bond
This bond is used where bricks of different thicknesses are to be used in facing and baking of walls.
5) Dutch Bond
Alternative courses of header and stretched bond as in English bond but every stretcher course starts at the corner with a three-quarter bat and header placed after the three-quarter bat.
6) Raking Bond
The bond is formed when bricks are laid in an inclination to the direction of walls.
Diagonal bond (Brick in the same direction)
Herring bond (opposite direction)
7) Zigzag Bond
Bricks are laid in a zigzag fashion, Used in brick flooring
8) Garden wall Bond
In the garden wall English bond, the header course is provided only after three t five stretcher courses. In the garden wall Flemish bond, each course contains one header after three to five stretchers.
Difference Between English and Flemish bond:
|S.N||English Bond||Flemish Bond|
|1||Headers and stretchers are laid in alternate courses.||Header and stretchers are laid alternatively in each course.|
|3||Provide a rough appearance.||Provide good appearance|
|4||Absence of vertical joints.||Partly continuous vertical joints.|
|5||Special attention is not required for this joint.||Special attention is required for this joint.|
|6||Progress of work-fast||Progress of work-slow|
|8||Skill labor id not required.||Skill labor is required|
|9||Less mortar is used||More mortar is used.|
Rat trap Bond
Bricks are placed in a vertical position which creates a cavity in the wall while maintaining the same wall thickness as that of conventional brick masonry walls. Also known as Chinese brick bond.
- Reduce the number of brick
- Thermal insulation
- Decrease a dead load of building
- For structural safety, a reinforcement bar can be inserted.
- A cavity can be used for plumbing, sanitary, wire, cable, etc.
Load Bearing And Non-Load Bearing Masonry:
1) Non-Load Bearing Masonry
Such masonry walls are used for partition or similar purposes only. They have to support self-weight and wind pressure or seismic force if any.
A Panell wall is a non-bearing wall supported by beams and columns in a framed structure. Also known as curtain wall. They are built lighter to reduce the dead load of the structure.
One can remove any non-load-bearing walls without endangering the safety of the building.
Types of non-load-bearing wall
- Hallow concrete block wall
- Focade Bricks Wall
- Hollow Bricks Wall
- Bricks wall
2) Load Bearing Masonry
These are the masonry walls that have to support considerable vertical loads and lateral loads other than their self-weight. Normally, loads are applied on the top of the wall from floors or roofs in building structures.
Load-bearing walls transfer loads to the foundation or other suitable frame members. It may interior or exterior wall.
Types of load-bearing masonry
- Pre-cost concrete wall
- Retaining wall
- Masonry wall
- Pre-panelized load-bearing metal stud walls
- Engineering Brick wall
Reinforced And Un-reinforced Masonry
These are a special types of masonry structures that are strengthened by suitably embedding strong and continuous material within the masonry. Such strong materials include steel bars, reinforced concrete bonds, bamboo, timber, and other new materials.
These reinforcements are capable of maintaining the integrity of masonry units even in large lateral loads and resist a part of forces like tension and shear. In other words, it increases the ductility and strength of the structure.
Classification of reinforced and un-reinforced Masonry
- Reinforced Hollow Unit Masonry
- Reinforced Grauted Cavity Masonry
- Reinforced Packet Type Walls.
Reinforced Hollow Unit Masonry: Vertical Reinforcement is inserted inside brick/block and filled with infill concrete or grout.
Reinforced Grauted Cavity Masonry: It consists of two leaves of masonry units separated by a cavity into which the vertical and horizontal reinforcement is placed and graduated with either concrete infill or grout.
Reinforced pocket-type walls: Vertical reinforcement is placed in the wall by a special bonding arrangement.
In reinforced hollow unit masonry, Vertical reinforcing bars are placed into a moving position before laying of the masonry unit but in reinforced pocket-type walls, the reinforcing bars are placed in mortar joints as the construction of the wall progresses.
The reinforcing bar is not placed in such type of masonry. Likely to be damaged during the earthquake. The mortar holding the masonry together is generally not strong enough to resist earthquake forces.
A charge of walls to the floor and roof is critical. These houses are weak and can be broken apart. Walls may fall away or buckle, resulting in damage.
Properties and strength of cement mortar
For good masonry work, good mortar is required. The properties of good mortar are:
1) Good Workability
A good mortar shall be sufficiently workable such that it can be laid to the right thickness with sufficient easiness by a mason. The addition of a small quantity of lime in cement mortar improves workability without compromising strength.
2) Sufficient Strength
In general, mortar shall have sufficient strength to resist the load in a structure, but shall not be greater than that of masonry units.
It shall be confirmed that the failure of masonry shall be initiated from mortar, not the masonry units in order to make the failure ductile. NBC 109:1934 recommendation in the selection of mortar is as follows:
|Masonry unit strength (N/mm2)||Recommend Mortar Type|
|24 and above 15-24.9 5-14.9 Less than 5||H1 H2 M1 M2|
3) Water Retaintivity
A good mortar shall be able to retain the mixed water for a longer time so as to maintain workability during its use.
Also after use, it shall be able to retain the water (prevent high loss) so as to facilitate the hydration process, otherwise, proper hydration may not occur resulting in a greater loss in strength.
4) Low Drying Shrinkage
Generally, the volume of mortar reduces slightly on drying or setting. Such shrinkage may cause cracks in stiffened masonry, especially around the edges.
In some cases due to shrinkage, the whole masonry wall settles slightly creating debonding from the frame at the top and sides. Hence, mortar shall have low drying shrinkage.
Good mix proportion, use of properly graded sand, optimum use of water, and good quality of cement reduce the shrinkage. For special case, shrinkage-resistant cement (or mortar) are also available, especially for grouting.
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