Surkhi is made by grinding to powder burnt bricks, brick-bats or burnt clay; under-burnt or over-burnt bricks should not be used, nor bricks containing a high proportion of sand but Surkhi for plaster may be made from slightly under-burnt bricks, and ground very fine; this will improve the hydraulicity of fat lime (Hydraulicity is the property of a binder to harden in contact with water.)
Surkhi makes cement mortars and concretes more waterproof, more resistant to alkalies, and to salt solutions than those in which no surkhi is used. Surkhi mixed-in cement concrete has been utilized in a number of large dams and different huge works in India. This admixture is understood to lessen the temperature upward thrust all through hydration in a mass cement concrete and decrease cracking. It is likewise beneficial in sea-water construction, in systems which can be a situation to assault from competitive groundwaters or business waters, and in hydraulic systems wherein water tightness is the primary attention Surkhi is used instead for sand for concrete and mortar and has nearly the identical characteristic as of sand however it additionally imparts a few power and hydraulicity.
Read More———————— LIME And MORTAR
- the bulk volume of mortar is increased which results in a reduction of cost, It does not increase the strength of mortar
- If the building material is fat lime, the carbon dioxide is absorbed through the voids of sand and the setting of fat lime occurs effectively.
- It prevents excessive shrinkage of the mortar in the course of drying and hence the cracking of mortar during setting is avoided.
- It subdivides the paste of the binding material into a thin film and thus more surface area is offered for its spreading and adhering.
Fineness modulus of Sand Coarse sand 2.9-3.2 medium sand 2.6 to 2.9 Fine Sand 2.2 to 2.6
- In the case of masonry exposed frequently to rains and where there is further protection by way of plastering or rendering or other finishes, the grade of mortar shall not be less than MM 0.7 but shall preferably be of grade MM 2. Where no protection is provided, the grade of mortar for external walls shall riot be less than 0-5 MM
- In the case of load-bearing internal walls, the grade of mortar shall preferably be MM 0.7 or more for high durability but in no case less than MM O-5.
- In the case of masonry in foundations laid below the damp-proof course, the grades of morter for use in masonry shall be as specified below:
- Where the soil has little moisture, masonry mortar of grade now no longer much less than MM 0.7 will be used;
- Where soil may be very damp, masonry mortar of grade ideally MM 2 or greater will be used. But in no case shall the grade of mortar be much less than MM 0’7; and
- Where soil is saturated with water, masonry mortar of grade MM three will be used however in no case shall the grade of mortar be much less than MM 2.
- For masonry in buildings’ concern to the vibration of machinery, the grade of mortar shall now no longer be much less than MM three.
- For parapets, where the height is greater than thrice the thickness, the grade of masonry mortar used shall not be less than MM 3.
- In the case of low parapets, the grade of mortar shall be the same as used in the wall masonry below.
- The grade of mortar for bedding joints with large concrete blocks shall not be less than 3MM
Cement Mortar for different work
Normal Brick Work and Internal Plaster (1:6), External Plastering Work and Ceiling (1:4), Grouting the cavernous rocks (1:1.5), Guniting (1:3)
Cement Mortar of high Grade is not required because there will be no gain in strength of masonry after that but shrinkage will increase due to excessive cement used.
Dry volume of mortar required for plastering = 1.27 X Wet volume of mortar
Read More———————— Grouting, Types Of Grouting
Advantages and Disadvantages of Surkhi Mortar
|There is a global sand shortage. So, surkhi mortar can be used as an alternative||Compared to ordinary mortar it is more subjected to shrinkage.|
|The constituents of this mortar do not segregate.||It has low compressive strength as compared to ordinary cement mortar.|
|It has a low heat of hydration.||It sets slowly.|
|It is more impervious than cement mortar of proportion leaner than 1:3.||An Un-proportion amount of silica-containing clay can cause less cohesion, cracking, shrinking, and warping.|
|It is more resistive to alkalis and salt solutions.||It cannot resist the long exposure of humidity, weathering, etc.|
|It is slow in setting and therefore it can be used for work up to a period of six hours of its preparation without|
disturbing the efficiency of mortar.
Strength And Quality of Surkhi Mortar
The mortar ready from surkhi varies in quality since the raw materials like clay or lime that occurred in nature are widely variable in quality. Even since the start of the employment of surkhi mortar for the various constructions; several styles of analysis and studies are allotted by engineers for deciding the strength, characteristics, and therefore the qualities of the materials used for the preparation of mortar.
Surkhi mortar gains strength if left immersed in water. Surkhi inappropriate for plaster exposed to weathering and wet conditions. Surkhi is other each in mortar and concrete. The addition of surkhi is among slight reductions in strength as surkhi attains its full strength solely when one year. Surkhi concrete is subject to a rather higher shrinkage than standard concrete. Surkhi is not a standardized turnout and its properties are widely variable.
Strength characteristics of surkhi mortar rely upon the following:
- The physical and chemical composition of lime or cement or surkhi.
- Mineralogical composition of surkhi.
- Degree of the burning of lime or cement or surkhi.
- The fineness of surkhi.
- combine proportion.
- the amount of grinding and solidifying of mortar.
FUNCTIONS OF SURKHI IN MORTAR
Surkhi, powdered quarry stone is used as an adulterant, but gives the mortar strength and hydraulic properties. In order to develop more firmness, it must be ground very finely with lime in the mortar grinder. Surkhi mortar is a mixture of lime, surkhi, and water. It is a lime mortar in which the sand has been replaced by surkhi for greater economy and resistance. Note: – Surkhi is finely powdered baked clay and is generally made from bricks that have been lightly burned under fire. and must not contain any particles retained on the IS n sieve. 9 more than 10% by weight surkhi, such as sand, are mainly used in the manufacture of mortar, concrete, plaster, etc. For economic reasons
This type of mortar is made with full surkhi instead of sand or, in the case of lime mortar, replaces half of the sand. The surkhi powder must be fine enough to pass BIS # 9 sieves and the residue must not be more than 10% by weight. Surkhi mortar is used for all kinds of ordinary masonry work on foundations and superstructures, but cannot be used for plastering or shoring as the surkhi is likely to crumble over time.