Mortar and lime
Building material Civil engineering
Mortar
Mortar is defined as the mixture containing a binding agent Like lime or cement,water and fine aggregate.
On the basis of Binding agent mortar is classified into following types
1 lime mortar
It does not set quickly
Lime mortar generally made with hydraulic Lime
Its provide better resistance against rain penetration
It is unliable to crack when compared with cement mortar
2.Cement Mortar
It is most suitable for construction work in Water Logged area
Gives shrinkage crack
3.Gauge Mortar
It is also called as composite mortar or cement lime mortar
with proportion of 1:1:6 to 1:1:8
After addition of cement It should be used with 1 to 2 hr
4 Light weight Mortar
It is Prepared by adding the material
like as Wood - Powder , saw-dust, etc to lime/cement mortar
5. Surkhi Mortar
Surkhi is a pozzolanic material and it is very fine in size
and it must be pass from a 4.75 mm sieve
surkhi is added to lime mortar to give hydraulically ability to set in presence of water
Lime-Cement Mortar:
Also known as Gauged mortar.
It is made from cement and lime.
The advantages of lime-cement mortar are
increased Water retentivity,
workability,
bonding properties
and frost resistance.
This mortar gives good and smooth plaster finish and is used in buildings.
Selection of Mortar
| No | work | Proportion cement:sand |
|---|---|---|
1. | Normal Brick work | 1:6 |
| 2. | Plaster work | 1:3 to 1:4 1:2 (lime:mortar) |
| 3. | Pointing in m2 | 1:1 to 1:2 |
| 4. | Damp Proof Work | 1:2 |
| 5. | Grouting | 1:1.5 |
| 6. | Guniting | 1:3 |
Note - Addition of 5% to 6% of moisture content by weight increase
the volume of dry sand from 13% to 18%
Lime
CaCO3 = CaO + CO2
CaO + H2O = Ca(OH)2
| no | Name | Chemical formula |
|---|---|---|
| 1. | Limestone | CaCO3 |
2. | Quick lime or Lump lime | CaO |
3. | Ca(OH)2 | Hydrated lime or slaked lime |
| 4. | H2o | water |
When the water is added to quick lime in sufficient quantity then a Chemical
reaction take place due to which quicklime Swell, Crack and Finally we get
Hydrated lime
| No | Type | Description |
|---|---|---|
| 1. | Fat lime | Also known as Pure lime, Rich lime, White lime etc. It contains impurity less than 5% hence It has High Calcium Oxide content It is obtained from Sea shell, Coral Reefs etc It can be used in white washing and Plastering. |
| 2. | Hydraulic Lime | This is called water lime because it can set under water. It contain Silica, Alumina and Iron Oxide in small quantity. It can be suitable for making mortar and using in masonry construction |
| 3. | Poor lime | It is also called Impure lime or Weak lime, lean lime It contains 30% Impurities as compared to pure Lime |
| 4. | Milk of Lime | A thin pour able suspension of slake lime in water is called milk of lime. |
| 5. | Note | slaked lime is utilized in painting and decorative work Hydraulic lime is obtained from Kankar Non hydraulic lime from calcined dolomite stones. Burning of limestone in presence of Oxygen is known as Calcination. |
Bulking of Sand
- The increase in moisture of sand increases the volume of sand and is known as bulking of sand.
- The volume of dry sand increases due to absorption of moisture. These volume increase of dry sand is known as bulking of sand. When dry sand comes in contact with moisture, a thin film is formed around the particles, which causes them to get apart from each other. This results in increasing the volume of sand. Addition of 5% and 6% of moisture content by weight increases the volume of dry sand from 18% to 38%.
Reason for the bulking of sand
- The reason is that moisture causes the film of water around sand particles which results in the increase of the volume of sand
- Bulking structure in sand is due to capillary action.
- For a moisture content percentage of 5 to 8, there will be an increase in volume up to 20 to 40 percent depending upon the sand
- If the sand is finer there will be more increase in volume
Graphical representation of bulking of sand is shown below:
Terracotta
- It is refractory clay brick and used in ornamental parts of buildings.
- The clay used for its manufacture should be of superior quality
- and should have sufficient iron and alkaline matters.
- It is burnt in special furnace known as Muffle furnace.
Water needed for complete Hydration of Cement
Approximately 23% water by weight is required for hydration and 15% water is entrapped in between the voids of cement. So, the total water required for complete hydration and workability is 38% by weight.
Segregation
- As per clause 13.2 of IS 456: 2000, the maximum permissible free fall of concrete to avoid segregation may be taken as 1.5 m or 150 cm.
- Segregation can be defined as the separation of the constituent materials of concrete.
- Insufficiently mixed concrete with excess water content shows a higher tendency for segregation.
- Dropping of concrete from heights as in the case of placing concrete in column concreting will result in segregation.
Slump and compaction Factor
Consistency | Slump | Compaction Factor |
Moist earth | 0 | 0.65-0.7 |
Very Dry | 0-25 | 0.7-0.8 |
Dry | 25-50 | 0.8-0.85 |
Plastic | 50-100 | 0.85-.95 |
Semi-fluid | 100-175 | 0.95-1 |
Plastic asphalt
- It is a mixture of cement and asphalt. Mechanical properties, resilient modulus, temperature susceptibility, water damage, creep and permanent deformation resistance are all improved by the mixing of cement and asphalt altogether.
- It is used for filling patches and cracks of flexible pavements. The temperature sensitiveness of the asphalt is overcome by the application of cement to it. Thus, it is primarily used for repair or reconstruction purpose.
Types of lime:
1. Fat lime:
It slacks rapidly and its volume is increased by 2 to 2.5 times of its original volume hence, it is referred as fat lime. It is also known as pure lime, rich lime, high calcium lime. It has more than 95% purity.
Properties- Slow setting, High plasticity, Soluble in water, Vigorous slaking, Perfectly white colour
Application- White wash & Plastering
Source- Sea shells
2. Hydraulic lime:
It is also known as water lime as it is capable of setting in water and damp condition. It has 70% to 90% purity.
Properties- Insoluble in water, Low plasticity, Less slaking, Off white colour, High hydraulicity
Application- Brick masonry or Stone masonry
Source- burning of Kankar
3. Poor lime:
It is also known as Impure or lean lime. It has less than 70% purity.
Properties- Muddy Colour
Application- Used in brick work around foundation
Floats are used to press mortar and spread it uniformly.
A trowel is a small hand tool used for digging, applying, smoothing, or moving small amounts of viscous or particulate material. Aluminium rod is used to strike off excess mortar.
A brush is used to clean the mortar. Floats are used to press mortar and spread it uniformly.
