What is Mortar?
Mortar is a paste (capable of setting and hardening) made with cement, and water or with lime, surkhi, and water. Cement & lime are binding materials utilized in the making of mortar. Sand and surkhi give strength to the mortars.
It also prevented more cracking due to shrinkage of the mortar. Mortar is a construction material utilized in masonry work to fill a joint between bricks and blocks used in construction industries.
When the paste is prepared by mixing cement or lime and sand without water is known as dry mortar. When the mortar is prepared by mixing cement, sand, and water known as wet mortar.
In the construction work, different kinds of mortar are utilized.
Properties of Good Mortar
- The mortars should be easily workable.
- The mortar mix should possess adequate strength in tension & compression.
- It should be capable to withstand developing designed stress.
- It should harden quickly.
- When set or hard it should be hard and durable.
- It should join the bricks and building stones properly.
- It should be less costly.
- Mortars should maintain their appearance for quite a long period.
- It should be capable enough of resisting the absorption of rainwater.
- The mortars utilized in plastering work should protect the masonry joints by forming an impermeable key bond.
- It should have good workability and consistency.
Types of Mortars Used in Construction Industries
Below are the different types of mortar used in construction work:
Cement mortar is made up of mixing cement, sand, and water thoroughly on the leveled platform. It may be prepared manually or machine mixed. After mixing, the mortar should be utilized within half an hour of adding water & should be re-mixed by adding water every 15 minutes to be used a little later. The bonding strength of the mortar depends on the ratio of sand & cement mixed.
How to Prepare Cement Mortar?
- Manual mixing is material is done for small amounts of mortar, while mechanical mixers can be used for larger amounts.
- Sand is sieved, cleaned with water to remove dirt and dust, and dried for manual mixing.
- On a pucca platform, the dry sand is laid out uniformly, and then the cement is spread evenly over it.
- With spades, the materials are thoroughly mixed to achieve uniformity.
- After that, a depression is created in the middle of the mixture, and the needed amount of water is added.
- The dry mix is moved from the sides and placed on the edges of the depression formed until the water is completely absorbed by the mix.
- A spade is then used to smooth out the wet mix and create a uniform consistency in the mortar.
- For mechanical mixing, the cement, sand, and water are weighed out and placed into the cylindrical container of the mixer before it is turned on.
- Inside the container, a rotor with blades rotates and completely mixes the components.
Uses of Cement Mortar:
- To bind masonry blocks like stones, and bricks and to plaster slabs and walls.
- It is used to give neat finishes to the wall, concrete surfaces, and pointed joints to masonry.
- It is also used to prepare concrete blocks, to fill joints and cracks in walls, and as a filler
- Material in stone masonry and Ferro-cement works.
- Plastering, rendering smooth finishes, and damp-proof courses are all done with cement mortars.
Lime mortar is made up of mixing lime and sand with water and is one of the oldest and most conventional types of mortars. Hydraulic lime / fat lime and inert materials like sand, surkhi, or cinder are utilized for making lime mortar.
Lime mortar is plastic enough, more workable & develops strong bonds with building blocks. The great famous structure Charminar in Hyderabad was the 1st monument in the world which was constructed utilizing lime mortar and granite.
Hydraulic lime or fat lime mortar is used for plastering and masonry works.
How to Mix Lime Mortar?
- The required volumes of lime & sand are deposited on an impermeable floor or in a mixing tank.
- Dry ingredients are mixed thoroughly by turning them up and down with spades.
- Water is added, and the mortar is mixed again with spades until it reaches a uniform color and consistency.
Uses of Lime Mortar:
- Fats lime mortars can be used in all types of foundation work that is in the dry subgrade.
- Fats lime and hydraulic lime are both appropriate for all masonry works.
- Lime mortars could be replaced with cement mortars.
- Additionally used to bind stones, bricks, or concrete blocks together.
- Lime mortars can not be used when the subgrade soil is moist or the water table is within 2.4 m.
- Heavy loading is expected.
- The construction is very large and very rough.
Mud mortar is made by adding sand and clay in such proportion that when mixed with water, there should not be any cracks after drying. Stones or coarser particles shouldn’t be present in the mixture of mortar to avoid cracking problems on walls later.
To get a better-plastered surface, small quantities of hydrated lime, bitumen, and cow dung are added. This mortar is cheap, less durable, and is commonly used for the construction of cheap houses, and temporary sheds for animals.
How to Mix Mud Mortar?
- Generally, 150-250 mm of the earth is excavated to prepare the mud mortar.
- The clay modules are then wetted & allowed to mature for a few days before being used in work.
- The utilization of fibrous material, such as cow dung, reduces shrinkage fractures.
- The ingredients are then properly mixed & kneaded.
Uses of Mud Mortar:
- It is used as a waterproofing coat.
- It also enhances the beauty of a building.
- It maintains the temperature inside the building.
- It is used where cheap construction of buildings is needed.
This type of mortar is made from a mixture of lime, water, and Surkhi powder where lime is used as binding material. Surkhi is powdered of burnt clay which gives more strength compared to sand. It does not use sand. Surkhi mortar can be utilized in all types of ordinary construction work.
How to Prepare Surkhi Mortar?
- This type of mortar is prepared by using fully surkhi instead of sand or by replacing half of the sand in the case of fat lime mortar.
- The powder of surkhi should be fine enough to pass through BIS No. 9 sieve & the residue shouldn’t be greater than 10% by total weight.
Uses of Surkhi Mortar:
- The surkhi mortar is used for ordinary masonry work of all kinds in foundations and superstructures. But it can’t be utilized for plastering or pointing since surkhi is likely to disintegrate after some time.
In gauge mortar combination of lime and cement is employed as a binder material, and sand is used as fine aggregate. Gauge mortar is essential, lime mortar whose strength is increased by adding cement.
Gauged mortar will have high plasticity of the lime & high strength of the cement. The percentage of cement to lime ranges from 1:6 to 1:9 and it is cost-effective.
Special Types of Mortar
Aside from the common mortars certain unique mortars are utilized in specific situations. Some of them are listed below:
- Damp proofing mortar is made with high-grade sulfate-resisting Portland cement or sulfate-resisting pozzolana cement as the binding material & quartz sand or crushed solid rock sand as fine sand. Damp-proofing mortars are made with expanding cement and are utilized to make water-tight seams and joints.
Sound Absorbing Mortar:
- Binding materials such as Portland cement, slag cement, lime, or gypsum are used to make these mortars. They are used as sound-absorbing plaster to reduce noise levels.
X-ray shielding mortar:
- X-ray mortar is one type of heavy mortar. Its density is more than 2200 kg/m3. In this mortar, the heavy stone is used as aggregate. Such mortar is used for plaster walls and ceilings of X-ray cabinets to protect the room against the ill effects of X-rays.
Joint Filling Mortar:
- Joint filling mortars are used for filling joints between prefabricated reinforced concrete members. Portland cement and quartz sand are used in the production of this mortar.
- These mortars are prepared by using colored cement to give to decorative finish to wall surfaces.
Mortar Types Based on Bulk Density
There are two types of mortar based on bulk density:
- The mortar which has a bulk density greater than 1500 kg/m3 is called heavy mortar. Commonly, it utilizes very heavy aggregates like quartz.
Light weight mortars:
- If the bulk density of mortar is less than 1500 kg/m3 is called lightweight mortar. It utilized light aggregates like pumice. Lightweight mortar is prepared by mixing light materials like sawdust, rice husk, jute fibers, asbestos fibers, and pumice with sand and cement.
- Lightweight mortar is mostly utilized in soundproof construction & heatproof construction. Cinder is an example of a lightweight mortar.
Mortars used for Different Masonry Work and Their Ratio
|Name of work
|Types of mortar and its ratio
|Stone masonry work in the foundation
|Cement mortar 1:6
|Construction in water logged area
|Cement mortar 1:3
|Masonry work in super-structure
|Cement mortar 1:6 / cement-lime mortar 1:1:6
|For the partition wall & Parapet wall
|Cement mortar 1:3 / Lime mortar 1:1
|Cement mortar 1:3 to 1:4 / Lime mortar 1:2
|Cement mortar 1:1 to 1:2
|Cement mortar 1:3
|Cement mortar 1:2
|Mortar for laying fire bricks
|1:2 Aluminous cement & fire bricks powder
|For the construction of the arch member
|Cement mortar 1:3
|Stone masonry work
|Lime mortar 1:2 / Cement mortar 1:6
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