B.ARCH 1ST SEMESTER
BUILDING MATERIALS - I
Mortar is a workable paste used to bind construction blocks
together and fill the gaps between them. The word comes from
Latin moratorium meaning crushed.
Mortar may be used to bind masonry blocks of stone, brick, etc.
Mortar becomes hard when it sets, resulting in a
rigid aggregate structure.
Mortar can also be used to fix, or point, masonry when the original
mortar has washed away
• Mortars are usually named according to the binding
material used in their preparation.
• They are essentially required for masonry work,
plastering and pointing etc.
FUNCTIONS OF MORTAR:
• To bind together the bricks or stones properly so as to
provide strength to the structure.
• To form a homogenous mass of the structure so as to
the loads coming over it without
Composition of Mortar
Modern mortars are typically made from a mixture of
a binder such as cement or lime, and
An ideal mortar:
Adheres completely and durably
to all the masonry unit to
Remains workable long enough to enable the operative to set the
masonry unit right to line and level; this implies good water
Stiffens sufficiently quickly to permit the laying of the units to
proceed smoothly, and provides rapid development of strength
and adequate strength when hardened.
Is resistant to the action of environmental factors such as frost
and/or abrasion and the destructive effects of chemical salts such
as sulfate attack.
Resists the penetration of rain.
Accommodates movement of the structure.
Accommodates irregularities in size of masonry units.
Contributes to the overall aesthetic appearance.
Is cost effective
Mortar as Binding Material
Nature of application
Brick Laying Mortars
Workability may be defined as the behavior of a mix in
respect of all the properties required, during application,
subsequent working and finishing.
Ease of use, i.e. the way it adheres or slides on the trowel.
Ease of spread on the masonry unit.
Ease of extrusion between courses without excessive
dropping or smearing.
Ease of positioning of the masonry unit without movement
due to its own weight and the weight of additional courses
Water Retentivity & Air content
This is the property of mortar that resists water loss by
absorption into the masonry units (suction) and to the air, in
conditions of varying temperature, wind and humidity.
Water retentivity is related to workability.
The air content of the mortar in its plastic state is also
important. In order to achieve good durability it is necessary
that there is sufficient air content (entrained air) to enable
freeze-thaw cycles to be resisted without disrupting the
matrix of the material.
Stiffening and hardening
The progression of stiffening, defined in the European
Standard as workable life, refers to the gradual change from
fresh or plastic mortar to setting or set mortar.
Hardening refers to the subsequent process whereby the set
mortar progressively develops strength.
Properties of hardened
Durability of mortar may be
defined as its ability to
endure aggressive conditions
during its design life. A
destructive influences may
interact with the mortar:
these include water, frost,
temperature change. In
general, as the cement
content increases so will
durability. Air entrainment
resistance to freeze-thaw
The use of too much cement will produce
a more rigid mortar, which may result in
vertical cracking passing through units
and mortar joints as stresses are imposed
Use of the appropriate mortar should not
result in cracking, but any that does
occur, (e.g. due to movement), will tend
to follow the joints, which will be much
easier to repair
Traditional masonry construction
tended to be massive relative to
modern structures, typically with
very thick walls. This meant that
the mass or bulk generally resisted
the various forces applied to it.
The development of modern
masonry units and advances in
mortar technology have led to
more slender structures which are
more vulnerable to lateral forces
e.g. wind loads.
MIXING THE MORTAR:
•The sand and the cement have to
be thoroughly mixed by hand or in
a mechanical mixer before adding
any water - do not use dirty water,
or water from puddles or ponds, as
this could impair the final strength
of the mortar.
•Similarly, keep any sugarcontaining liquids, such as soft
drinks, well away from the mix sugar, even in small amounts,
seriously impairs the setting ability
of the cement.
Types of Mortars
Mortars are classified on the basis of the following
KIND OF BINDING MATERIAL
NATURE OF APPLICATION
By Bulk Density
According to the bulk density of mortar in dry
state , there are two types of mortars.
Heavy Mortar Bulk Density =/> 1500 kg/m3
Lightweight Mortar -
Bulk Density < 1500 kg/m3
Kind of binding material
Lime – Surkhi Mortar
FUNCTION OF SAND AND SURKHI IN MORTARS:
Functions of sand:
•It reduces shrinkage of the building material.
•It prevents development of cracks in the mortar on
•It helps in making mortars and concretes of desired
strength by varying its proportions with the binding
•A well graded sand adds to the density of mortars and
Functions of surkhi:
•It provides brick color and make the mortar economical
Lime mortar is a type of mortar composed of lime and
an aggregate such as sand, mixed with water.
Lime mortar is primarily used in the conservation of buildings
originally built using lime mortar, but may be used as an
alternative to ordinary portland cement.
A lime kiln is used to produce quicklime through
the calcination of limestone (calcium carbonate).
CaCO3 + heat → CaO + CO2
as quicklime or burnt lime, is a widely used chemical
compound. It is a white, caustic, alkaline crystalline solid at
room temperature usually obtained from limestone.
Slaking of Lime
When water is added to quick lime in sufficient quantity,
lime cracks, swells and falls into powder form due to the
chemical reaction thus forming calcium hydrate
•The paste is prepared by mixing lime and sand or surkhi in
suitable proportions in addition to water.
•If surkhi is to be added in lime mortar the equal proportions of
sand and surkhi should be mixed with lime.
•These mortars are inferior to cement mortars in strength as well
as water tightness.
•These mortars should not be used for underground works as they
set in the presence of carbon dioxide and break up in damp
•This type is used for construction work above ground level i.e.
Ht: 40 cm
6 – 9 m Dia
BULLOCK DRIVEN GRINDING MILL
Width: 30 cm
180- 240 CM Dia
POWER DRIVEN GRINDING MILL
•The paste is prepared by mixing suitable clay, soil with
•The soil which is used for preparing mud mortar
should be free from grass, pebbles etc.
•These are the cheapest mortars but weakest in
•These mortars are used for brickwork of ordinary
buildings and for plastering walls in rural areas.
PREPARATION OF CLAY
Mixing With Hand
Homogenous Mixture Clay Mortar
•The paste is prepared by mixing cement and sand in
suitable proportions in addition to water.
•The general proportion is 1 part of cement to 2-8 parts
•These mortars must be use within half an hour, i.e.;
before initial setting time of the cement.
•This type is used for all engineering works where high
strength is desired such as load bearing walls, deep
foundations, flooring etc.
•When mixing by hand, the sands and cement are heaped up on a
mixing board or in a wheel barrow and repeatedly turned over
and over until thoroughly mixed.
•The color of the dry mix will change as the cement is
distributed throughout - there should be no 'streaking' of
cement, and no clumps of pure sand or pure cement.
•Once the dry ingredients are mixed, the water can be added.
Dry sand and cement in
Begin to mix sand and cement
Mix to evenly distribute cement
The dry mix should be all one colour
Add water and plasticiser
Mix to required consistency
•When using a mechanical mixer, add half a bucket (2 or 3
liters) of clean cold water to the empty drum before adding the
dry ingredients in sequence.
• Add 4 measures of sand then 1 of cement, followed by 4 sand,
then another cement and so on until the required quantity is in
•This ensures a more thorough mix than adding, say, 20
measures of sand and then 5 measures of cement.
•Again, the water is added to the revolving
drum once the dry ingredients are
thoroughly blended, a bit at a
time until the required consistency
For wide joints in paving or for stonework, either as
paving or as walling, a coarser mortar is often preferred
- replace half of the building/soft sand with grit/sharp
sand. You will probably find that a coarse mortar such
as this requires less gauging water to achieve a working
consistency than does a bricklaying/general purpose
Mortar for Wide Joints
2 x Building Sand plus
2 x Grit Sand plus
1 x cement
Fire resistant mortar:
•The paste is prepared by mixing aluminous cement
and finely crushed fire bricks (1:2) in suitable
proportions in addition to water.
•The usual proportion are 1 part aluminous cement to
2 parts of finely crushed fire bricks.
•These are generally used for lining furnaces, ovens and
fire places with fire bricks.
Light weight mortar:
•The paste is prepared by mixing wood powder, wood
sawing or saw dust with cement or lime mortar.
•In such mortars fibers of jute coir or asbestos fibers can
also be used.
•These are generally used as fiber plasters in sound and
heat proof construction.