Building MortarThis chapter mainly introduces the technical requirements for building mortar and the methods to design the mix proportion of masonry mortar, and simply presents other kinds of mortar. It is required to master the major technical properties of mortar and the mix proportion design of masonry mortar.

Building mortar is a building material formed by mixing cementing
materials, fine aggregates, mixtures and water in an appropriate proportion.
The main difference between mortar and concrete is that there is no coarse
aggregate in the composition of mortar. Thus, building mortar is also called
fine aggregate concrete.
Building mortar is usually used in the following areas: in structural
engineering, it binds stone, brick, blocks together and fills the gaps in brick
walls and the joints in large wall panels and various components; in decorative
projects, it is used to plaster brick walls, floors, and structural beams and
columns; and it is also used to inlay natural stone, artificial stone, ceramic tiles
and mosaic tiles.
According to different purposes, the building mortar can be classified into
masonry mortar, surface mortar (ordinary surface mortar, waterproof mortar,
decorative mortar), and special mortar (such as heat-insulated mortar,
corrosion-resistant mortar, and sound-absorbing mortar).
Based on different cementing materials, building mortar can be divided into
cement mortar, lime mortar, gypsum mortar, mixed mortar and polymer
cement mortar. The commonly used mixed mortar includes cement lime
mortar, cement clay mortar and lime clay mortar.
6.1 The Composition of Mortar
To ensure the quality of building mortar, various materials in the composition
of mortar should meet certain technical requirements.
6 Building Mortar 151
1. Cementing Materials
The major cementing material in building mortar is cement, including
ordinary cement, hrnace-slag cement, masonry cement and fly-ash cement.
Proper cement varieties should be chosen according to the projects’
environmental conditions. The strength grades should be selected in line with
those of mortar. Generally, the strength grades of cement (the compressive
strength value of 28d, in MPa) should be 4-5 times of the strength grades of
mortar. Because the strength grades of mortar are not high, the cement in
medium and low strength grades can satisfjr the requirements. If the strength
grade of cement is too high, appropriate amount of mixed materials (like fly
ash) can be added in order to save the cement consumption. As to the mortar
for special use, especial mortar and organic binding materials can be used. For
example, expanding cement can be used for component joints, seams,
structure strengthening or crack repairing; and white and color cement can be
used to prepare decorative mortar.
Lime, gypsum and clay can also be used as the cementing materials for
mortar and they can be mixed with cement to prepare mixed mortar to save
cement and improve the workability of mortar.
The strength grades of cement used in masonry cement should be chosen
according to the requirements of design. The strength grades of the cement
used in cement mortar should not be more than 32.5; and that of the cement
used in cement mix mortar should be no more than 42.5.
2. Fine Aggregate
Sand is the find aggregate for building mortar. It should be in line with the
technical requirements of sand used in concrete. In addition, the maximum
particle diameter of sand should be limited due to the thin layer of mortar. The
layer of mortar used in rubble masonry is just 114-1/5 of mortar’s maximum
particle diameter; medium sand whose maximum particle diameter is not
more than 2.5mm is appropriate for the mortar used in brickwork; fine sand
can be applied to surface and jointing mortar, with the maximum diameter no
more than 1.2mm. For the sake of mortar quality, clean sand should be
selected. And the impurity content in sand should not be too much. It is
regulated in Specijkation for Mix Proportion Design of Masonry Mortar
(JCJ98-2000), the building industry standard, that the mud content of sand
I52 Building matcrials in civil engineering
should not be'more than 5%; and in the cement mix mortar of M2.5 (strength
grade), the mud content of sand should not be more than 10%. And the sulfide
content (equivalent in SO3) in sand should be less than 2%.
3. Water
The Clean water without harmful impurities should be adopted to mix mortar,
generally the same as the water requirement for concrete.
4. Mixtures and Additives
In order to improve the workability of mortar and save cement, some
inorganic fine mixtures, such as lime paste, clay paste, and fly ash, can be
added to mortar. Lime should precipitate, and fly ash should be ground, for a
better effect. The provisions on mixtures regulated in Specification for Mix
Proportion Design of Masonry Mortar (JCJ98-2000), the building industry
standard, include:
1) When quick lime ages to lime paste, it should be screened by the sieve
with the aperture no more than 3mm X 3mm, and the aging time should be no
less than 7d; the aging time ofthe ground quick lime should be no less than 2d.
The lime paste stocked in sedimentation tank should be protected from drying,
freezing and polluting. Dehydrated lime paste is forbidden.
2) When clay or mild clay is used for clay puddle, it should be mixed by
mixer with water and be screened by the sieve with the aperture no more than
3mmX3mm. When the organic compounds in the clay are checked by
colorimetry, the color should be paler than the standard color.
3) The carbide slag used for carbide plaster should be screened by the sieve
with the aperture no more than 3mm X 3mm, and when checked, it should be
heated to 70C and maintained for 20min. It can only be used without the odor
of acetylene.
4) Hydrated lime powder can not be used in masonry mortar directly.
5 ) The consistency of lime paste, clay plaster and carbide plaster in
preparation should be 120mmk5mm.
6) The quality of fly ash should accord with Ffy Ash Used in Cement and
Concrete (GB 1596-9 I), the national standard; and that of ground quick lime
should be in line with Building Quick Lime Powder (JC/T480-92).
6 Building Mortar 153
Masonry Types
Ordinary Sintercd Masonry
Small-size Fine-aggregatc Hollow Blocks and Masonry
Sometimes, micro foam agent can be added to improve the workability of
mortar. The common micro foam agent is rosin pyrolytic polymer and its
mixing amount is 0.005%-0.0 1 % of the mass of cement.
Additives can be mixed in mortar to improve the workability and other
construction properties of mortar. The types, mixing amount, and physical
properties of additives should be determined by test.
Consistency of Mortar (mm)
70-90
60-90
6.2 The Main Technical Properties of Mortar
Sintered Porous Bricks, 1 lollow Brick Masonry
Ordinary-sintered-brick Flat-arched Lintels
Rowlock Walls, Barrel Arches
Small-sizc Ordinary-concrete Hollow Blocks and Masonry
Aerated Concrete Blocks and Masonry
Stone Masonry
For the sake of projects, the newly mixed mortar should have good
workability, and the hardened mortar should have the required strength, the
bending power to the bottom face, little deformation and durability.
6.2.1 Workability of Fresh Mortar
60-80
50-70
30-50
The workability of fresh mortar refers to the comprehensive properties of
mortar easy for construction and good for quality, including mobility and
water retention. The mortar with good mobility is easy to be paved thinly and
evenly on bricks and bonded with floors well.
1. Mobility (Consistency)
The mobility of mortar is the property that mortar can flow under the role of
dead weight and exterior force. Fluidity is expressed by “sinking degree”,
usually determined by the consistency of mortar. The bigger the sinking
degree is, the better the mobility will be.
The selection of mortar mobility should be determined by masonry types,
construction conditions, and weather. The consistency of masonry mortar
should be selected according to Code for Acceptance of Construction Quality
of Masonry Engineering (GB50203-98), the national standard, shown in
’ Table 6.1.
Table 6.1 Consistency of Masonry Mortar
154 Building materials in civil engineering
2. Water Retention
The water retention of mortar refers to the property of mortar to maintain
moisture. When the mortar with good water retention is used in transportation,
standing and pavement, water will not escape from mortar soon and the
necessary consistency can be maintained. To keep a certain amount of water in
mortar is easy to manipulate and also guarantees the normal hydration of
cement to maintain the strength of masonry.
The water retention of mortar is expressed by layering degree, measured by
mortar layering degree instrument. The mortar with good water retention has
the layering degree of 10-30mm, and if it is more than 30mm, the water
retention will be bad and easy to segregate; the mortar whose layering degree
is less than lOmm is not good for construction. Based on many experiments,
the layering degree of cement mortar should be no more than 30mm, and the
layering degree of cement mix mortar should be no more than 20mm.
6.2.2 Strength and Strength Grades of Hardened Mortar
The hardened mortar should have big strength which is expressed by strength
grade. Compressive strength is the main basis for mortar strength.
The strength grade of mortar, expressed by f,,, , is determined by
compressive strength average (MPa) measured through curing a group of six
cube specimens with side length of 70.7mm for 28d, the standard test method.
The strength grades of mortar include: M20, M15, M10, M7.5, M5 and
M2.5, the six grades.
The strength of mortar is connected with its surface material. For the
ordinary cement mortar, the following equation can be used to calculate its
compressive strength.
1. Imhygrophanous Beds
The strength of the mortar used in imhygophanous beds (such as dense stone),
similar as concrete, mainly depends on the cement strength and water-cement
ratio, defined as follows:
In this formula: f,,, is the compressive strength of 28d (MPa);
f, isis the measured strength of cement (MPa);
6 Building Mortar 155
-C is water-cement ratio. W
2. Hygrophanous Beds
When mortar is used in the hygrophanous beds (bricks and other porous
materials), some of the water will be absorbed by base materials. Because
mortar has a certain property of water retention, no matter how much water is
added, the remaining amount is the more or less the same. In this case, the
strength of mortar is determined by cement grade and dosage and has nothing
to do with water-cement ratio, defined as follows:
fm,, = (a.LQc '1000) + P (6:2)
In this formula: fm,o is the compressive strength of mortar for 28d (MPa);
Q, is the cement consumption of mortar per cubic meter, (kg);
a,P is the characteristic coefficients, and a = 3.03, p = -1 5.09;
f, is the measured cement strength, accurate to 0.1MPa.
6.2.3 Adhesion Stress of Mortar
Brick and stone masonry is a solid entity composed of many blocks that are
bonded by mortar as a whole. Thus, it is required that mortar must have a
certain adhesion stress over bricks and stones. Generally, the more the
compressive strength of mortar is, the bigger its adhesion stress will be. In
addition, its adhesion stress is related to the surface, cleanness, and humidity
of bricks and stones, as well as the construction and curing conditions. For
example, bricklaying needs watering, and the surface without clay will
improve the adhesion stress and ensure the quality of masonry.
6.2.4 Deformability of Mortar
It is easy for mortar to get deformed when it bears loads or the temperature
changes. If it deforms greatly or unevenly, the quality of masonry and surface
will decrease and cause sinkage and crack. When fine aggregates are used to
mix the mortar, its deformation is bigger than the ordinary mortar. In order to
prevent the cracks caused by uneven shrinkage deformation, hemp cut, paper
strip and others fabric materials can be mixed in the surface mortar.
156 Building materials in civil engineering
6.2.5 Durability of Hardened Mortar
The durability of mortar refers to the property to withstand wear and tear in the
long-term use. The hydraulic masonry that usually contacts with water should
be impermeable and frost-resistant, so the impermeability and frost resistance
of hydraulic masonry should be considered.
1. Frost Resistance
The frost resistance of mortar refers to the property to resist freeze-thaw cycle.
Mortar is frozen and damaged because the water in its pores expands due to
freeze and breaks the pores. Thus, dense mortar and the mortar with closed
pores have good frost resistance. In addition, the factors influencing the frost
resistance of mortar also include cement types, strength grades, and
water-cement ratio.
2. Impermeability
The frost resistance of mortar is'the property to resist the infiltration of
pressure water. It is mainly related to density and size and structure of the
inner pores. The connecting pores inside mortar and the cellular structures and
, pores formed when it is moulded, all of which can lead to water seepage of
mortar.
6.3 Masonry Mortar
The mortar that binds bricks, stone, and construction blocks together into a
whole masonry is called masonry mortar. The load-bearing ability of masonry
depends on not only the strength of bricks and stones, but also the strength of
mortar. Therefore, mortar is the most important part of masonry.
6.3.1 The Mix Proportion of Masonry Design of Mortar
(JGJ98-2000)
The mix proportion of masonry mortar should be determined by the strength
grade of masonry mortar selected according to the design requirements of
project types and parts of masonry. Generally, it can be determined by
adjusting through trial mixture after referring to the relevant manuals and
information. The steps to design the mix proportion of mortar used for
water-absorbing layers are as follows:
6 Building Mortar 157
Excellent6.3 Masonry Mortar
The mortar that binds bricks, stone, and construction blocks together into a
whole masonry is called masonry mortar. The load-bearing ability of masonry
depends on not only the strength of bricks and stones, but also the strength of
mortar. Therefore, mortar is the most important part of masonry.
6.3.1 The Mix Proportion of Masonry Design of Mortar
(JGJ98-2000)
The mix proportion of masonry mortar should be determined by the strength
grade of masonry mortar selected according to the design requirements of
project types and parts of masonry. Generally, it can be determined by
adjusting through trial mixture after referring to the relevant manuals and
information. The steps to design the mix proportion of mortar used for
water-absorbing layers are as follows:
6 Building Mortar 157
Excellent
M2.5 M5.0 M7.5 M1O.O M15.O M 20
0.50 1 .00 1.50 2.00 3.00 4.00
Normal I 0.62 I 1.25 I 1.88 I 2.50 I 3.75 I 5.00
Bad I 0.75 I 1.50 I 2.25 I 3.00 I 4.50 I 6.00
2. Calculate Cemeqt Consumption
The cement consumption in every cubic meter
follows:
should be calculated as
(2. Calculate Cemeqt Consumption
The cement consumption in every cubic meter
follows:
should be calculated as
(6.5)
158 Building materials in civil engineering
In the equation: Q, is the cement consumption in mortar per cubic meter
fma0 is the trial strength of mortar (MPa);
f,, is the measured strength of cement, accurate to O.1MPa;
a,P are the specificity coefficients, and a=3.03,
If the measured strength of cement can be obtained, it can be calculated as
(6.6)
(kg/m3);
p=-15.09.
follows:
fce = rc * fie,k
In the equation: & is the strength value of the level of cement varieties;
rc is the extro-coefficient of cement strength, and it should
be determined by the actual statistics; if there is no
statistics, r, is 1 .O.
If the calculated cement consumption in cement mortar is less than
200kg/m3, 200kg/m3 should be adopted.
3. Determine the Quantity of Mixtures Qd
The quantity of mixtures used in cement mixed mortar should be defined as
follows:
Qd =Q, -Qc (6.7)
In the equation: Q, is the quantity of the mixtures in mortar per cubic meter,
Q, is the quantity of cement in mortar per cubic meter,
Q, is the total quantity of the cementing materials and
mixtures in mortar per cubic meter (kg/m3), appropriate
between 300-350kg/m3.
If the consistencies of lime paste are different, the conversion factors can be
(kdm3 1;
(kdm3);
selected from Table 6.3.
Tablc 6.3 The Conversion Factors of Lime Paste with Different Consistencies
Conversion Factor I 1.00 1 0.99 I 0.9'
6 Building Mortar 159
Strength Cement Quantity in Mortar
Grades
M2.5-M5 200-230
4. Quantity of Sand Qs
Sand Quantity in Mortar Water Quantity in Mortar
The water, cementing materials and mixtures in mortar are used to fill the
pores in sand. Thus, mortar of lm3 contains sand of lm3 cumulative volume.
The quantity of sand in mortar per cubic meter should be calculated by the
bulk density in the dry state (the water ratio is less than 0.5%), in the unit of
kg/m3.
5. Quantity of Water Q,,,
M7.5-MI0 1 220-280
MI5 280-340
The quantity of water in mortar per cubic meter should be 240-310kg
according to the consistency of mortar.
In order to solve the problem that the calculated quantity of cement is small,
the mix proportion of cement mortar can be determined by table-checking
method: the quantity of the materials used in cement mortar can be selected
from Table 6.4.
270-330
Bulk Dcnsity Value of
1 m' Sand
Table 6.4 Water Quantity in Mortar Per Cubic Meter
Note: 1) The strength grade of cement in this table is 32.5; if the strength grade is more than 32.5, it is
appropriate to choose the minimum.
2) Select the cement quantity reasonably according to projects.
3) When fine sand or coarse sand is used, the water quantity should be the maximum and minimum
4) If the consistency is lower than 70mm. the water quantity can be lower than the minimum.
5) If the building site is hot or in dry seasons, more water can be used accordingly.
respectively.
6. Trial Mixing, Adjustment and'Determination of the Mix Proportion
The actual materials used in projects should be adopted in preparation, and as
for the mechanical mixing, the stirring time should be calculated from the end
of feeding, in line with the following regulations:
1) For the cement mortar and cement mix mortar, the time should be no less
than 120s.
2) For the mortar mixed with fly ash and admixtures, the time should be no
less than 180s.
There are two steps of trial mixing:
160 Building materials in civil engineering
(1) Adjusting Trial Mixing
When mix the calculated proportion or that checked from table, the layering
degree and the consistency of the mixtures should be determined. If it cannot
meet the requirements, the quantity of materials should be adjusted until it
meets the demand. This mix proportion is the basic mix proportion.
(2) Checking Strength
There are at least three mix proportions in trial mixing. One of them is the
basic mix proportion obtained from the above adjustment of trial stirring.
Moreover, the cement quantities of the other two mix proportions should be
increased and decreased by '1 0% of the basic one respectively. The water
quantity or mixtures quantity can be adjusted accordingly under the conditions
that the consistency and layering degree are qualified. AAer adjustment, the
shaping of specimen and the determination of the strength grades of mortar
should be conducted according to the existing Experimental Method of the
Basic Properties of Building Mortar (JGJ70), the national standard; and the
mix proportion of mortar selected is the one in which the cement quantity is
small, in line with the requirements.
Though the mix proportion of mortar has been determined, it must be tested
and determined again if the raw materials are changed.
6.3.2 Examples for the Mortar Mix Proportion Design
[Example] It is required to design the mix proportion of the mortar for brick
walls whose level is MI0 and the consistency of cement lime mortar is
70-90nim. The main parameters of the raw materials are: cement: ordinary
Portland cement of 42.5; sand: medium sand with bulk density of 1450kg/m3
and water content of 2%; lime paste: consistency of 100mm; building level:
normal.
[Solve] (1) Calculate trial strength f m,-,
fm,o = f,,, + 0.6450 =10+0.645 X2.5=11.6(MPa)
(2) Calculate cement quantity Q,
(3) Calculate the quantity of lime paste Qd
Q, =Q,-Q, =350-207=143(kg/m1)
6 Building Mortar 161
Convert the lime paste consistency of lOOmm to 120mm (referred to
table 6.3)
143x0.97=139(kg/m3)
(4) Calculated sand quantity based on its bulk density and water content,
QS
Q, =1450x(1+0.02)=1479(kg/m3)
( 5 ) Select water quantity Q,
According to Table 6.4, the water quantity Q, = 300kg/m3 . The ratio of
Cement lime paste : sand : water = 207 : 139 : 1479 : 300 =
various materials used in mortar is:
1 : 0.69 : 7.14 1.45
6.4 Other Kinds of Building Mortar
6.4.1 Surface Mortar
Surface mortar is also called plaster mortar that is plastered on the surface of
buildings in a thin layer to protect them, increase their durability, and also
smooth their surfaces and make them clean and artistic. Based on its different
functions, surface mortar can be classified into ordinary surface mortar,
waterproof mortar, decorative mortar and special surface mortar.
1. Ordinary Surface Mortar
Ordinary surface mortar is mainly used to protect buildings and also smooth
their surfaces and make them clean and artistic. Different from masonry
mortar, the technical requirement for surface mortar is not compressive
strength but workability and bonding power with substrate. Thus, it needs
more cementing materials.
In order to ensure the smooth surface and avoid cracking, plaster mortar is
usually plastered on bottom, middle-level, and cover coat, the three layers.
And different layers need different kinds of mortar.
The mortar on the bottom layer mainly need to bond with the base. Mortar
plastered on the bottom of brick wall is lime mortar; cement mortar is used for
waterproof and moisture-proof; cement mortar or mixed mortar are often used
on the bottom layer of concrete; mixed mortar or lime mortar are used on
strapped walls and ceilings.
162 Building materials in civil engineering
Names of Plastcr
Layer
Bottom Layer
Middle-level Layer
Cover Coat
The mortar on the middle-level layer is used for leveling, mostly mixed
mortar or lime mortar.
The mortar on the cover coat mainly functions as protection and decoration.
Thus, it is appropriate to use fine sand. The mortar plastered on surface is
oAen mixed mortar, hemp cut lime mortar, and paper strip mixed lime mortar.
Cement mortar shohld be used in the parts easy to get bumped or wet, such as
dado, washboard, pool, windowsill and others.
The mobility of surface mortar and the maximum particle diameter of
aggregate should be referred to in Table 6.5, and its mix proportions in
Table 6.6.
Sinking Degrce(cm)ArtificiaI Maximum Particle Diameter of
’ Plastering Sand(mm)
10-12 2.6
7 - 9 2.6
7 - 8 I .2
Table 6.5 Mobility of Surface Mortar and the Maximum Particle Diameter of
Aggregate
Materials
Lime : Sand
Lime : Clay : Sand
Lime : Gypsum : Sand
Lime : Gypsum : Sand
Lime : Gypsum : Sand
Lime : Cement : Sand
Cement : Sand
Cement : Sand
Cement : Sand
Cement : Gypsum :
Sand : Sawdust
Cement : White Pebble
Cement : Dolomitic
lime : White Pebbel
Cement White Peddle
White lime : llemp cut
White lime paste :
Hemp cut
Paper Strip : White
lime mortar
Mix Proportion(Vo1ume
Ratio)
1 :2-I :4
1 : 2-1 : 1
1 : (0.5-1) : (1.5-2)
I : 1.5
100 : 2.5 (Mass Ratio)
100 : 1.3 (Mass Ratio)
Emplaster of O.Icm’, papcr
strip of 0.36kg
Application
The surfaces of brick walls (except cornice,
plinth, parapet. and walls of wet rooms)
The surfaces of walls in dry environment
Walls and ceilings of dry rooms
Walls and ceilings of dry rooms
Architraves and othcr decorative projects
of dry rooms
Cornices, plinths, parapets, and wet parts
Dados, plinths or ground bases of
bathrooms and wet workshops
Floors, canopies, or the surfaces of wallsPress polish for concrete floorsSound absorption paint
Terrazzo concrete ( I : 2.5 cement mortar
used for priming)
Granitic plaster(1 : 0.5 : 3.5 for priming)
Chopped stone [I : (2-2.5) cement
mortar for priming]
Bottom layer of batten canopy
Cover coat of batten canopy(or 100 kg lime
paste mixed with 3.8 kg papcr strips )
Advanced walls and canopies
6 Building Mortar 163
2. Waterproof Mortar
The mortar used to make waterproof layer is called waterproof mortar, or rigid
waterproof layer. This kind of layer is only used for concrete or brick and
stone masonry that has certain stiffness but does not suffer from vibrating.
Rigid waterproof layer is inappropriately used in the buildings that deform
greatly or may sink unevenly.
Waterproof mortar can be made by ordinary cement mortar. Or,
water-repellent admixture can be added to cement mortar to improve the
impermeability of mortar.
The commonly used water-repellent admixtures include chloride metallic
salt water-repellent admixture, sodium silicate water-repellent agent, and
metallic soap water-repellent admixture. Chloride metallic salt water-repellent
admixture is the colored liquid mixed with calcium chloride, aluminum
chloride, and water in a certain ratio. And its mix proportion is: aluminum
chloride': calcium chloride : water= 1 : 10 : 11. The mixing amount is 3%-5%
of the cement mass. If this water-repellent agent is mixed in cement mortar, it
can generate impermeable double salt in the process of setting and hardening
to densi fy structures and improve the impermeability of mortar, generally
used for pools or other underground buildings.
Sodium silicate water-repellent agent mainly contains sodium silicate to
which four alums are often added, thus also known as quadric-alum
water-glass water-repellent agent. The four alums are blue copperas (sodium
sulfate), alums (potash alum), hemalum (chromic alum), and dichromate
(potassium dichromate). Take one-share sample separately from each of the
four alums to make them dissolve in 60-share water of lOO"C, then cool them
down to 50C, put them into 400-share water-glass and klly stir them. Such
water-repellent agent can generate many colloid that will jam capillary tubes
and pores, thus to improve the waterproof property of mortar. Potassium
dichromate is highly toxic, so it should be used very carefilly.
Metal soap waterproof agent is made by mixing stearic acid, ammonia,
potassium hydroxide (or sodium carbonate) and water together in a certain
ratio and then heating and saponifj4ng them. This kind of waterproof agent
also can fill pores and jam capillary tubes. The mixing quantity should be
about 3% of the cement mass.
164 Building materials in civil engineering
The mix proportion of waterproof mortar is usually: cement: sand=
1 : (2-3), and water-cement ratio is often controlled between 0.5-0.55. The
appropriate cement is the ordinary Portland cement of 32.5 strength grade
above, and the proper sand is medium sand.
The construction of waterproof mortar requires high techniques. To prepare
waterproof mortar, first mix cement and sand hlly, add measured waterproof
agent to mixing water and cement as well as sand, and fully stir them. When
plaster it, the thickness of each layer should be about 5mm. There are totally
4-5 layers about 20-3Om. First plaster a pure cement paste on wet and clean
bottom and then plaster waterproof mortar about 5mm. Use a wooden float to
press it for one time before initial setting. The techniques used in the second,
third, and forth layers are the same. Press polish is conducted on the last layer.
Curing should be strengthened after plastering. In short, the density of the
mortar and the construction techniques should be required strictly in
plastering the rigid waterproof layer; otherwise, it is difficult to reach the
desired waterproof effect.
3. Decorative Mortar
The mortar plastered on the surface of interior and exterior walls of
constructions to increase their aesthetic effects is called decorative mortar.
The main difference between the decorative mortar and the plastering mortar
lies on the surface layer. The colorful cementing materials and dyes should be
used in surface layer and they can make the surface reveal various colorful
lines and patterns through special processing methods.
The cementing materials used in decorative mortar include ordinary cement,
fly ash cement, pozzolana cement, white cement and colorful cement, or the
colorful cement, lime, and gypsum made by mixing alkali-resistant mineral
dyes into the commonly-used cement. The dyes are often marbles, granites
and other kinds of colorhl rock ballasts, glass, and ceramic particles.
The processing methods of the decorative mortar include:
Scuffing: use the cement mortar as the bottom layer and the cement lime
mortar as the surface layer; before the mortar coagulates, scuff the surface into
rugged shapes with a spatula.
Granitic plaster: use the mortar confected by the rock ballasts of about 5mm
as the bottom layer; then spray water to the surface before the initial setting of
6 Building Mortar 165
the cement to make the ballasts show out but not fall off, looked like granite in
distance.
Terrazzo: use the common cement, white cement or colorful cement and
various colorhl marble ballasts as the surface layer, and scrape and polish the
surface after they get hardened. There is pre-cast terrazzo and present-cast
terrazzo. It is aesthetic and also water-proof and wear-resistant, used for
flooring and decoration, such as dado, baseboard, sill board, partition board,
pool and sink.
Pebble dash: bond colorhl ballasts and glass particles below 5mm on the
whole surface of the cement plaster. It can be bonded manually or
mechanically. The bonding should be firm. The decorative effect of pebble
dash is the same with that of terrazzo. It avoids wet work and also can be built
efficiently and save materials.
Artificial stone: also called chopped false stone, is a kind of false stone
facing. Its raw materials and processing methods are the same with those of
terrazzo. Chop the surface with the edge of axe after the cement mortar
hardens. It has the same effect as the coarse granite.
6.4.2 Special Mortar
1. Insulating Mortar
Insulating mortar is made by mixing cement, lime, gypsum and other
cementing materials with expanded perlite sand, expanded vermiculite, or
ceramic particles and other lightweight porous materials together in a certain
mix proportion. The insulating mortar is lightweight and has good thermal
insulation. Its thermal conductivity is 0.07-0.10W/ (m K). It can be used for
the insulating layers of roofs and pipelines, insulating walls, and others.
The common insulating mortars include:
(1) Modified Lime Insulating Mortar (simply called CL insulating mortar)
The modified lime insulating mortar (simply called CL insulating mortar) is
the dry material of the insulating mortar made by: calcining calcium sulfate
dihydrate and anhydrous calcium sulfate at a high temperature (more than
1180 "C ), mixing the resultants type I -CaS04,CaO and PCaS04*1/2
HzO-with admixtures into cementing materials, adding the lightweight sand
with the density no less than 180 kg/m3 (the lightweight sand made by the high
temperature puffing of obsidian ) and polyphenylene particles, and precasting
them all.
166 Building materials in civil engineering
The high-temperature calcined modified anhydrite should be taken as the
base for the cementing materials of the insulating material, and the
semi-hydrated gypsum is forbidden.
The added insulating material should not be broken in the plastering process.
The loose density of the lightweight sand should be within 180-250kg, and
the particle size of polyphenylene particles should be no more than 3mm.
The technical indexes of the modified insulating mortar should accord with
Technical Specification for Application of the Insulating Mortar
[DB 13/T(J)25-2000], the local standard of Hebei province: the thermal
conductivity 60.07W/(m*K); the compressive strength 2 0.6MPa; the
bending strength 30.4MPa; the loose density is 480kg/m3 and the density
after plastering is 600 kg/m3; the bond strength 30.4MPa; the initial time
36Omin and the final time 324h.
The preparation of the modified lime insulating mortar: the insulating
mortar (dry material) should be confected into slurry manually on the
plastering floor indoor or by the portable mixer in half of a barrel; the
consistency (used for walls and roofs) is: dry material of mortar : water =
1 1; the consistency can also be controlled according to the real needs, with
the thickness of 20-50mm; if the slurry is used for walls or roofs, it should be
confected into semi-hard mortar, and its thickness is calculated in thermal
unit.
The modified insulating mortar can be used for the thermal insulation of
solid sintered bricks, porous sintered bricks, hollow ceramic blocks, hollow
fumace-slag blocks, aerated concrete blocks, concrete and other masonries.
(2) ZNJ-I Silicate Insulating Material
ZNJ-I silicate insulating material is a kind of powder made by mixing
aluminum silicate fibers, expanded perlite powder and other kinds of good
insulating materials. It is non-toxic, pollution-free, light, insulating, deafening,
flame retardant, and fire-proof. It has high strength, quick setting, no cracks,
no hollow beds, convenience and durableness. The compressive strength is
5-8 times than that of the traditional materials.
The technical indexes of ZNJ- I silicate insulating material are: dry density
6230kg/m3; thermal conductivity 60.058W/(m-K); volume shrinkage
620%; bonding strength 350kPa.
The process features of ZNJ- I silicate insulating material are: paint a layer
of interfacial agent on the concrete wall and scuff it; add appropriate amount
6 Building Mortar 167
of water into the dry powder and stir them into slurry; when the slurry has a
certain strength and moisture at the first time, repeat the above movements for
the second time. It is required that the product should be scraped smoothly and
pressed solidly; there should be no hollow beds; the material should be mixed
when used; it will become the waste material for over 3h, and no new material
is allowed to mix into the waste one; and outside decoration process should be
done until it becomes dry, with the temperature 33C.
ZNJ- I silicate insulating material can be used for the thermal insulation of
residential buildings, office buildings, and public constructions. It should be
packed in the woven bag with plastic bag inside. In transport, it should be
protected Erom moisture and water; in storage, it should be put in dry place to
avoid moisture and insolation.
(3) ZNR-I11 Silicone Insulating Material
ZNR-111' Silicone Insulating Material is a kind of powder made by
lignocellulose, organic coagulant, compound perlite, heat insulation powder
and other insulating materials. When used, it should be stirred with water. It
can be a good insulating layer when painted on walls, proper for the thermal
insulation. Its other features are almost the same with those of ZNJ- I silicate
insulating material.
2. Sound-absorbing Mortar
Similar with the insulating mortar, sound-absorbing mortar is consisted of
lightweight porous aggregates. It has good sound absorption. The
sound-absorbing mortar can be made by mixing cement, gypsum, sand, and
sawdust (whose volume rate is 6 : 1 : 3 : 5 ) together, or adding glass fibers,
mineral wools into lime and gypsum mortar. This mortar can be used for the
sound absorption of inner walls and roofs.
3. Corrosion-resistant Mortar
Corrosion-resistant mortar is made by water glass (sodium silicate) and
sodium fluosilicate. And sometimes, quartzite, granite, cast stone, and other
kinds of fine aggregates can be added into it. The hardened water glass has
good corrosion resistance. This mortar can be used for lining materials,
corrosion-resistant floors, and the protective layers inside the
corrosion-resistant containers.
168 Building materials in civil engineering
4. Polymer Mortar
The polymer mortar is made by adding organic polymer emulsion into the
cement mortar. The common polymer emulsions include styrene butadiene
rubber emulsion, chloroprene rubber emulsion and acrylic resin emulsion. The
polymer mortar has high bonding power, little shrinkage, low brittleness, good
corrosion resistance, used for repair and protection engineering.
5. Radiation-proof Mortar
Radiation-proof mortar is made by mixing barite powder and barite sand into
cement mortar. Its mix proportion is: cement : barite powder : barite sand =
1 0.25 : (4-5). It can resist X-ray. If borax and boric acid are mixed into the
cement mortar, it will be the radiation-proof mortar which is often used in the
radiation protective engineering.
Questions
6.1 Briefly describe the application and classification of mortar in projects.
concrete?
6.2 What’s the difference between the composition of mortar and that of
6.3 How to select cement when preparing mortar?
6.4 What’s the requirement for the sand used in masonry mortar? Why
should the mud content in sand be controlled?
6.5 What’s the regulation about mixtures in Specification for Mix
Proportion Design of Masonry Mortar (JGJ98-2000), the building industry
standard?
6.6 What kinds of contents does the workability of mortar include? And
how to express them?
6.7 Why should mortar have water retention? How to improve the water
retention of mortar?
6.8 What are the types of surface mortar based on the functions?
6.9 What are the requirements for ordinary surface mortar?
6.10 What are the requirements for the techniques of waterproof mortar?
6.1 1 What are the types of decorative mortar?
6.12 What are the types of thermal mortar?
6 Building Mortar 169
Exercises
The cement lime mortar used for brick walls is prepared on a building site.
The required design strength is M7.5, required consistency is 70-90mm, and
the construction level is normal. The main parameters of raw materials are:
cement: the ordinary Portland cement of 42.5; sand: medium sand with bulk
density of 1450kg/m3 and water content of 2%; lime paste: consistency of
1lOmm. Try to calculate the mix proportion.
References
Cao Wenda, Cao Dong. 2000. Building Project Materials, Beijing: Golden Shield Press.
Chen Yafu. 1998. Building Materials. Guangzhou: South China University of Technology
Chen Zhiyuan, Li Qiling. 2000. Civil Engineering Materials. Wuhan: Wuhan University
Gao Qiongying. 1997. Building Materials: Wuhan: Wuhan Univeristy of Technology.
State Bureau of Quality and Technical Supervision. 2000, 2001, 2002, 2003. National
Standards of P.R.C.
Hunan University, et al. 1989. Building Materials (Third Edition), Beijing: China
Architecture & Building Press.
Liu Xiangshun. 1989. Building Materials, Beijing: China Architecture & Building Press.
Sun Dagen. 1997. Building Materials and Project Quality, Guangzhou: South China
Xi’an University of Architecture & Technology, et al. 1997. Building Materials, Beijing:
China Architecture & Building Press. 2000. Comprehensive Criteria of Existing Building
Press.
of Technology Press.
University of Technology Press.
China Architecture & Building Press.
Materials (Supplement), Beijing: China Architecture & Building Press