Different types of mortars used in masonry construction based on application, binding material, density and purposes. Mortar is a workable paste prepared by adding water to a mixture of binding material and fine aggregate.
This plastic paste is useful to hold building materials such as stone or brick together. Different types of mortars used in masonry construction are presented below.
Types of Mortars Used in Masonry Construction
Following are the types of mortars based on different factors:
- Based on Applications
- Based on Binding Materials
- Based on Bulk Density
- Based on Strength (ASTM C270)
- Based on Special Purpose of Mortars
Based on Application
1. Bricklaying or Stone Laying Mortar
This type of mortar used to bind bricks and stones in masonry construction. The proportions of ingredients for bricklaying or stone laying mortar is decided based on kind of binding material used.
2. Finishing Mortar
Finishing mortar is used for pointing and plastering works. It is also used for architectural effects of building to give aesthetic appearances. The mortar used for ornamental finishing should have great strength, mobility and resistance against atmospheric action like rain, wind, etc.
Based on Binding Material
3. Cement Mortar
Cement is used as a binding material in this type of mortar and sand is employed as aggregate. The proportion of cement and sand is decided based on the specified durability and working conditions.
Cement mortar will give high strength and resistance against water. The proportion of cement to sand may varies from 1:2 to 1:6.
4. Lime Mortar
In this case, lime is used as binding material. There are two types of limes namely fat lime and hydraulic lime. Fat lime in lime mortar requires 2 to 3 times of sand and it is used for dry work.
Hydraulic lime and sand in 1:2 ratios will give good results in damp conditions and also suitable for water logged areas.
Finally, the lime mortar has a high plasticity so it can be placed easily. The pyramids at Giza are plastered with lime mortar.
5. Gypsum Mortar
Gypsum mortar consists of plaster and soft sand as binding material and fine aggregate. Commonly, it has low durability in damp conditions.
6. Gauged Mortar
In gauge mortar combination of lime and cement is employed as a binder material, and sand used as fine aggregate. Gauge mortar is, essentially, lime mortar which its strength increased by adding cement.
Consequently, the mortar will have high plasticity of the lime and high strength of the cement. The ratio of cement to lime ranges from 1:6 to 1:9, and it is cost effective.
7. Surkhi Mortar
In surkhi mortar, lime is used as binder material and surkhi is employed as fine aggregate. The surkhi is finely-powdered burnt clay which provides more strength than sand and cheaply available in the market.
8. Aerated Cement Mortar
Basically, it is cement mortar to which air entraining agent is added to increase plasticity and workability. The resulted mortar is termed as aerated cement mortar.
9. Mud mortar
In this type of mortar, mud is used as binding material and saw dust, rice husk or cow-dung is used as fine aggregate. Mud mortar is useful where lime or cement is not available.
The use of mud mortars in the Middle-East and central Asia, and American cultures of the south-western USA is well documented.
Based on Bulk Density
10. Heavy Mortar
If the mortar having bulk density of 15 KN/m3 or more then it is called as heavy mortar. Generally heavy quartzes are used as fine aggregate in this type of mortars.
11. Lightweight Mortar
If the mortar having bulk density of less than 15 KN/m3 then it is called as light mortar. Lightweight mortar is prepared by mixing lime or cement as binder, sand, and saw dust, rice husk, jute fibers, coirs, or asbestos fibers.
Cinder mortar is a variety of light-weight mortars. Lightweight mortar is generally used in the soundproof and heat proof constructions.
Based on Strength (ASTM C 270)
12. Type M Mortar
It is the highest strength mortar minimum 17.2 MPa (2500 psi). It is used for exterior masonry work and at or below grade application where substantial gravity or lateral loads are exerted. load bearing wall, footing, retaining wall are examples of below grade applications.
13. Type S Mortar
It is a medium-strength mortar minimum 12.4 MPa (1800 psi) with high bonding ability. it is used for grade applications with normal to moderate loading.
Type S mortar has great durability that is why it is highly suitable for locations where the masonry is in contact with the ground, such as paving or shallow retaining walls.
14. Type N Mortar
It is medium strength with minimum 5.2 MPa (750 psi) and most common type of mortar. Type N mortar used for reinforced interior and above-grade exterior load-bearing walls on which normal loads are imposed.
15. Type O Mortar
It is a low strength mortar with minimum 2.5 MPa (350 psi). Type O mortar employed for interior non-load-bearing applications with very limited exterior use. Added to that, it used for repointing where the structural integrity of the wall is intact.
Based on Special Purpose of Mortars
16. Fire Resistant Mortar
Fire resistant mortar is prepared by mixing aluminous cement to the fine powder of fire bricks. If there are any fire warnings to the structures in a particular zone, then fire resistant mortar will be used which acts as fireproof shield.
17. Packing Mortar
The constituents of packing mortars are generally cement-sand, cement-loam or sometimes cement-sand-loam. This type of mortar is used to pack the oil wells. Packing mortar should be of high homogeneity, water resistance and high strength.
18. Sound Absorbing Mortar
In sound absorbing mortar, cement, lime, gypsum, or slag used as binding materials and pumice, cinders as fine aggregate. It is used to reduce the noise level and acts as sound proof layer.
19. X-ray Shielding Mortar
To provide protection against ill effects of X-rays, the X-ray room walls and ceilings are plastered by X-ray shielding mortar. This is heavy type mortar with bulk density around 22KN/m3. Fine aggregates from heavy rock and suitable admixtures are used to prepare this type of mortar.
20. Chemical Resistant Mortar
It is generally used where there is a chance of chemical attack on the structures. There are so many types of chemical resistant mortars can be prepared but the selection of mortar is dependent on expected damage by particular chemical or group of chemicals.
The additives added may not resist all the chemical attacks. For example, silicate type chemical mortar resists nitric, chromic, Sulphuric or any acidic damages but it cannot prevent the structure against damage by alkalies of any concentration.