Effect of Admixture on Properties of Concrete

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 09 Issue: 10 | Oct 2022 www.irjet.net p-ISSN: 2395-0072
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Effect of Admixture on Properties of Concrete
Er. Khalil Rahman Farhat and Er. Masood Jamali
*Master of Civil Engineering (Construction Technology and Management).
*Master of Civil Engineering (Construction Technology and Management).
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Abstract - This research indicates the Effect of Admixture
on Properties of Concrete. Concrete is a man or a machine-
made construction material that has more usage in the
construction field, it is necessary to make construction secure
and safe for making high strength concrete the admixture
Silica fume is a good choice to make the compressive strength
of concrete very high but for having a high strength concrete.
Chemical Admixtures interact with hydrated cementitious
materials and are divided into three categories of Admixtures
with physical, chemical, and physical-chemical performance.
Admixtures with a physical function are chemical Admixtures
that do not have a direct effect on the cement dewatering
reaction process, althoughtheymayaffect itsprocessandrate.
These Admixtures generally show their effect and function
before the initial setting of concrete and their effect does not
continue after setting in hardened and hardened concrete.
These Admixtures include water reducers, aerobes, gas
generators, foaming agents, aerators, anti-scouring agents,
pumping facilitators, colorants, and bonding agents.
Admixtures with chemical function either affect the process
and reaction process ofpre-settingcement dewateringoralter
the microstructure of dewatering products before and after
setting. Therefore, in addition to the pre-set time, the reaction
of chemical Admixtures may continue in the hardest stages of
concrete. Reinforced concrete is brittle and has less tensile
strength. In order to reduce the weakness of fragility, thin and
short filaments that are randomly distributed in all directions
in concrete are a very suitable method (these thin filaments
are called fibers). The main reason for using fibers in concrete
is to increase the hardness and tensile strength, improvecrack
control and deformation.
Key Words: Admixture, Concrete, Silica Fume (SF),FlyAsh
(FA), Grade 43 Portland cement (PC)
1. INTRODUCTION
The production of cement, the main adhesive in concrete,
was started in England in 1756 by John Smeaton, who was
responsible for building the foundation of the Eddystone
tower, and finally Portland cement in 1824 on the same
island. The name was registered in the UK by Joseph Aspdin.
The people of our country also became acquainted with the
consumption of cement since 1312 with the construction of
the Ray Cement Factory, and with the development of the
country’s industries, today about 26 to 30 million tons of
cement are produced per year. With the knowledge of
engineers on how to use cement in civil works, this material
found its place in our country. One of the fastest-growing
methods of construction in the world today is concrete
buildings. After the Islamic Revolution, due to the lack of
beams as a result of sanctions and the expansion of
construction in the country, the useofconcretegrewgreatly.
In addition, concrete buildings have advantages over steel
buildings, such as greater resistance to fire and atmospheric
factors (corrosion), ease of preparation of concrete due to
the abundance of concrete materials, and insulation against
heat and sound, which is the development of the day. In
addition, it provides this type of building. One of the
important disadvantages of concrete buildings is the very
high weight of the building, which is directly related to the
amount of earthquake damage to the building. If we can
make the separating blades and panels of lightweight
concrete, the weight of the building and as a result, the
destruction of the building by the earthquake will be greatly
reduced. However, the low strength of lightweight concrete
has been an important factor in limiting the scope of
application of this type of concrete and taking advantage of
it.
2. METHODOLOGY
The use of micro silica in the manufacture of lightweight
concrete has increased the strength of lightweight concrete
and reduced thislimitation. In this research,whileexplaining
concrete and the effect of water on concrete strength, more
about light concrete and methods of increasing its strength
using micro silica, mechanical properties, and also its
applicationsare discussed. Atfirst, it may be thoughtthatthe
main building material is a viscous material resulting from
the hydration of cement and water and that aggregates are
cheap and filler materials of this adhesive. The second
possibility is that coarse aggregates are considered as
masonry joined by mortar and this mortar is cement slurry
and fine aggregates. The third possibility is that concrete is
considered as a material of two different phases, namely
hydrated cement and stone grains. Therefore, the properties
of concrete depend on the properties of each of the phases
and the interface between the two phases. Eachofthesecond
and third theories has limitations and can be used to express
the behavior of concrete. But in the first theory, these issues
do not exist.
If it is thought that cement can be produced cheaper than
aggregates, the question arises whether cement and water
can be used alone as a building material (concrete)? The
answer will definitely be no, due to the high-volume changes
in the cement paste. The shrinkage of pure cement paste is

approximately 10 times that of concrete with 250 kg of
cement per cubic meter. The same is true for creep and drop.
In addition, the high heat generated by consuming large
amounts of cement, especially in hot climates, will cause
cracks. It also makes aggregates more resistant to chemical
attack than cement paste, although the cement paste is also
relatively stable in these corrosive environments. Therefore,
regardless of the price of stone materials in concrete will be
very useful.
3. CONCRETE COMPONENTS AND THEIR
PROPERTIES
• Cement: makes up about 7 to 15% of the volume of
concrete
• Water: makes up about 14 to 21 percent of the
concrete volume
• Rock aggregates (sand): make up about 60 to 75%
of the concrete volume
• Air: In airless concrete, the amount of air volume is
between 0.5 to 30% and in aerated concrete, the amount of
air volume is between 4 to 8%.
• Admixtures: These are chemicals that are added to
the mixture in small amounts and as a percentage of the
weight of cement to create the desired properties in
concrete.
4. THE ROLE OF CEMENT IN CONCRETE
Any adhesive is called cement. However, the adhesive of
stone materials in concrete is called cement, whose role is
simply to stick the grains together and alone does not affect
the strength and load-bearing capacity.
Table -1: Cement components
63% Cao
20% Sio
6% 3o2Al
3% 3o2Fe
1.5% Mgo
5.CHEMICAL IN CEMENT
Tricalcium silicate: (3Cao-Sio2) abbreviated (C3S), Calcium
silicate:(2Cao-Sio2)abbreviated(C2S),Tricalciumaluminate:
3Cao-Al2o3)withtheabbreviation(C3A),Aluminophytetetra
calcium: (4Cao-Al2o3-Fe2o3) abbreviated (C4AF)
6. TYPES OF STANDARD CEMENT (PORLAND)
• Type I cement, ordinary cement, this type of cement
is used in normal weather conditions and where there is no
form in terms of sulfate (Uses: All concrete works such as
street tables - mortars - coatings and .....
• TypeII cement, medium cement, this typeofcement
is partially retardant and alsopartially resistant to theattack
of sulfates. Uses: (For concreting in hot environments and
bulk concreting and ...
• Type III quick-setting cement this, type of cement
has the basic components of type I cement, but is finely
ground and therefore has a faster setting. Uses: Manufacture
of precast concrete parts, use in cold weather, in workshops
that use slippery molds.
• Type IV cement, quick setting cement, this type of
cement is a retarder and has less C3s and C3A and has more
C2S. Uses: In bulk concreting, in hot environment
temperature above 40 degrees, concreting in successive
layers Note: Consumption of this cement in hot weather
prevents cold connection.
• Typefivecement, anti-sulfatecement, this typeofcement
is suitable for use in concreting that is exposed to sulfate
attack.
If we can make the separating blades and panels from
lightweight concrete, the weight of the building and as a
result the destruction of the building by the earthquake will
be greatly reduced. However,the low strength of lightweight
concretehas been an important factor inlimitingthescopeof
application of this type of concreteandtakingadvantageofit.
7. USE OF WATER IN CONCRETE
The place of water use in concrete is very sensitive in
terms of hydration. Lack of proper use of water will lead to
the following problems:
• Cement setting time is delayed, concrete is delayed
• Decreases the final strength of concrete(sometimes
reduces the strength by up to 30%)
• Causes corrosion and gradual deterioration of
rebars.
• On the surface of the final dried concrete, it creates
stains that are especially important in concretes whose
surface is placed in the façade.
8. CHARACTERISTICSOFWATERCONSUMPTIONIN
CONCRETE
• Not acidic and alkaline (PH between 6 to 8).

• The percentage of carbonates is less than 0.1%.
• Thepercentageofsolids(suspendedparticles)initis
less than 0.1%.
• The percentage of chlorides should be less than
0.05%.
• The percentage of sulfates should be less than 0.1%.
• The sum of calcium and magnesium carbonate in
water used in concrete is not considered harmful if it is up to
0.4%.
• The total salts of manganese, tin, zinc, lead should
not be more than 0.5%.
• Iron salts in concretewaterdonotaffectthestrength
of concrete up to 4%.
• One of the most unsuitable water impurities in
concrete is sodium sulfide, which has a maximum vapor
content of 1%.
• The use of seawater due to the presence of salts of
chlorides, sulfates, etc., which reduces the strength by up to
15%, and on the other hand, the chlorine in seawater causes
corrosion of rebars over time and its use in reinforced
concrete is not allowed. .
• Stone grains (sand)
9. PROPERTIES OF SAND USED IN CONCRETE
1- The seeds should be completely clean and free of mud
and chemical impurities.
2- The grains must be resistant to abrasion and stress.
Note: Silica aggregates have a hardness of 7 to 8 and are
the most resistant aggregates used in concrete. Limestone
grains have a hardness of 3 to 4 which are used in making
concrete.
3. The seeds must be resistant to frost, which depends on
the following 3 factors.
A- Porosity: The higher the porosity of the grains, the
lower the resistance to frost.
B. Impermeability: The higher the grain permeability,the
lower the frost resistance.
C- Tensile strength: The higher the tensile strength, the
greater the resistance to frost.
4. The seeds must be resistant to weathering.
In terms of final strength of concrete, concrete that is made
with angled grains will be more durableduetothepossibility
of better aggregation of grains with each other and the
friction of the best of them. It is recommended to use this
type of grain in cases where very high resistance is desired
(above 350 to 400 Kg / cm2), but in normal work where less
resistance is the criterion, round and irregular grains can be
used.
Figure 1. Deferent type of Concrete
10. PROPERTIES OF CONCRETE
• Concrete is mainly composed of two parts
• Stone materials: About 60 to 75% of the concrete
volume consists of stone materials.
• Cement paste:About25to40percentoftheconcrete
volume is filled with cement paste. From 25 to 40 percent of
cement pasteis 17 to 15 percent cementand14to21percent
water.
• Water content in cement paste (W / C)
• W represents water and C represents the weight of
cement, so that a low W / C ratio can be selected.
• This rate is about 0.4 to 0.6 percent.
• Characteristics of using less water to cement ratio
• Increase the compressive and tensile strength of
concrete.
• Increase the sealing property in concrete.
• Reduced water absorption.
• Better bonding between cardboard layers in
concreting.
• Increased adhesion between rebar and concrete.
• Increased resistance to adverse weatherconditions.
• Reduce drop rate, creep rate and reduce the
possibility of water dropping concrete.

• Reduce the possibility of grain separation.
• Concrete performance (slump)
Figure 2. Concrete Slump
Concrete is mainly composed of two parts Stone materials:
About 60 to 75% of the concrete volume consists of stone
materials. Cement paste: About 25 to 40 percent of the
concrete volume is filled with cement paste. From 25 to 40
percent of cement paste are 17 to 15 percent cement and 14
to 21 percent water. Water content in cement paste (W / C)
W represents water and C representstheweightofcementso
that a low W / C ratio can be selected. This rateis about 0.4to
0.6 percent. Characteristics of using less water to cement
ratio Increase the compressive and tensile strength of
concrete. Increase the sealing property in concrete. Reduced
water absorption. Better bonding between the cardboard
layers in concreting. Increased adhesion between rebar and
concrete.Increasedresistancetoadverseweatherconditions.
Reduce drop rate, creep rate, and reduce the possibility of
water dropping concrete. Reduce the possibility of grain
separation. Concrete performance (slump).
11. PROBLEM THAT MAY OCCUR IN FRESH
CONCRETE
1- Watering:
It seems that after concreting and polishing the concrete
surface, a thin layer of water impregnated with cement
appears on the concrete surface. The most important reason
is excessive slump. Another reason, such as excessive
vibration and inadequategranulation,increasethelikelihood
of concrete melting.
2- Separation of seeds:
The most important reason for grain separation is high and
excessive slump. Other reasons such as excessive vibration,
moving the concrete in the form with a shovel or vibrator,
pouring concrete from a height, improper storage of grains,
and lack of uniform and correct granulation in concrete, lead
to separation of grains and concrete from the compressive
and flexural strength will be weak and will not reach the
desired level.
12. FACTORS AFFECTING CONCRETE STRENGTH
Grain quality: Concrete made of silica grains has a higher
strength than concrete madeof limestone.Graincontent:The
more grains are used in concrete, the stronger and more
durable the concrete. Amount of cement: The higher the
amount ofcement, the higher the strength of concrete.Water
to cement ratio (W / C): The lower this ratio (about 3.4 to
0.4), the higher the strength of the concrete made. Concrete
life: 7-day strength in ordinary concrete is 70% 28-day
strength, 28-day strength of concrete, which is about 90 to
95% of the final strength.
Note: The useful life of concrete buildings is usually in the
range of 50 to 100 years. Concrete differentiation in terms of
density (specific gravity).
1.1. Deferent Types of Concrete added Admixtures
1.2. Ordinary concrete
Concretes that are made with ordinary cements of type (I) to
type (V) have a specific weight of 2200 to 2500 kg per cubic
meter, which is due to the difference in grain material and
concrete density.
1.3. Light weight Concrete
It is concrete whose specific weight is 1.2 to 1.3 times the
specific weight of ordinary concrete,whichismadeofnatural
or broken aggregates. The specific weight of this type of
concrete is approximately 800 Kg / m3, which is used for
facades, partition walls, roofsand basically where there isno
resistance. Classification oflightweightconcreteaccordingto
their type of application.
A- Lightweight structural concretes:
This type of concrete has a specific mass between 1400 to
1900 kg / m3 and its minimum compressivestrengthisequal
to 17 N / mm2. Aggregates that are used according to ASTM-
C330 standard for lightweight structural concrete are: (1 -
Shale, clay and slate 2- Roasting process 3- Expandable slags
1.4.- Pumice (mineral and industrial)
1.5. The main advantages of this type of concrete:
• Reduce the cost of heating or cooling.
• Reduce sound transmission between floors and
building space.
• Meanwhile,non-structurallightweightconcretesare
divided into two groups based on their buildingcomposition.

A- Foamconcrete:duringtheirconstructionbycreatingfoam,
air bubbles in the cement paste or in the cement mortar,
aggregates are created. Specific mass (Kg / m3).
B- Concretewith light grains:which aremadeusingperliteor
vermiculite or expandable polyester fibers. The specific
gravity of this mixture (Kg / m3 960 to 240).
1.6.- Roasted fly ash)
B- Semi-structural lightweight concrete:
This type of concrete has a compressive strength between 7
to 17 Newtons per square millimeter and their specific
gravity is 800 to 1200 Kg / m3. Semi-structuralconcretesare
made with aggregates such as perlite, polystyrene fibers and
foam floors.
C- Non-structural light concrete:
This concrete is used for filling and thermal insulation
purposes and light separators (separating blades and sound
insulation in the floor). It has a specific gravity of less than
3800 Kg / m and despite its low specific gravity, its
compressive strength can be up to 7 N / m2.
1.7. Heavy concrete
In making this type of concrete, instead of sand, steel chips,
cast iron or barium sulfate are used. This concrete is used to
prevent X-ray, Y-radiation, etc., and is mainly used for
structures related to nuclear facilities or wherever
radioactive radiation is possible.Thespecificgravityofheavy
concrete is about 1.5 to 2.5 times the equivalent of the
specific gravity of ordinary concrete (6400 Kg / m3).
1.8. Pre-stressed concrete
This type of concrete was founded using high-strength steel
as well as goodqualityconcrete.Wovenconcreteapplications
can be used in the construction of bridges and offshore
structures (such as ports, offshore terminals, fixed and
floating oil docks) and, most importantly, nuclear power
plants. Lack of cracks in structures made of pre-stressed
concrete prevents water and moisture from easily
penetrating intoitandcausingcorrosionandrustbyreaching
the steel.
1.9. Fiber concrete
Reinforced concreteis brittleand has less tensile strength.In
order to reduce the weakness of fragility, thin and short
filaments that are randomly distributed in all directions in
concreteare a verysuitable method (these thin filamentsare
called fibers). The main reason for using fibers in concrete is
to increase the hardness and tensile strength, improve crack
Applications of fiber concrete:
• Remote control of highways - roads and airports.
• Bridges and docks.
• On the surface of refractory walls of furnaces
(petrochemical industries, steel, cement factories).
• Floors of factories, bus stops, gas stations and
industrial halls.
• Explosion-proof structures.
• Parts related to tunneling and mine drilling.
• Protective walls, shelters and hangars.
1.10. Sulfur concrete
Today, thistypeofconcrete,whichhasmanyadvantagessuch
as resistance to acids and corrosive substances, the ability to
melt and reuse, has good flexural and compressive strength,
has been considered the use ofsulfurconcreteinareaswhere
there is a high risk of corrosion Recommended. Sulfur
concrete is made by hot mixing of sulfur and mineral
aggregates (like the asphalt production method) and is a
thermoplastic material (free of water and cement). The best
weight ratio forpreparing sulfur concreteis20%sulfur,32%
fine-grained, 48% coarse-grained and 5% silica powder.
Figure 3. Types of concrete
1.11. Polymer concrete
Polymers are used to produce three types of concrete:
A - Concrete with injection polymer (PIC):
It has compressive, tensile andimpactresistancesaswellasa
very high modulus of elasticity and is more resistant to
freezing, thawing and abrasion by chemical attacks.

B- Polymer concrete (PC)
Methacrylateandstyrenemethylmonomersandepoxyresins
are used to make this type of concrete.
C. Portland Cement Polymer Concrete (PPCC)
Made by adding a polymer or monomer to fresh concrete,
rubber, acrylic and acetate vinyl are examples of materials
used with an anti-foaming agent.
1.12. Shotcrete Concrete
This type of concreteis used for repairing existing structures
as well as works that do not require formwork or complex
shapes with low thickness. It is generally used for the inner
lining of tunnels, tanks and prestressed concrete tanks, and
other uses for stabilizing sloping rock cliffs, covering steel
plates to create a fire shield.
1.13. Self-compaction concrete
Liquid concrete that is compacted under its own weight and
has extremely high performance and can be used in sections
with high reinforcement without theuseofvibratorsiscalled
self-compacting concrete (s.c.c). This concrete, in addition to
havinghighperformance,non-separationofparticlesforming
concrete in the fresh state, has low permeability, high
durability and high strength in the hardened state. Its
applications, especially in the production of ready-mixed
concrete and prefabricated parts, have been considered by
the construction industry.
1.14. Rolled concrete (RCC)
It is concretethat is compacted by the movementoftheroller
when the concreteis not yet hardened. The slip ofthistypeof
concrete is zero so that it can withstand the weight of the
compacting roller.
Benefits and applications
• In the construction of roads, freeways, runways and
hangars, floors of warehouses, industrial roads, mines,
stadiums, racetracks, ports and docks, etc.
• Withstand heavy traffic load, especially on slopes
• Stiffness and no deformation against the loads and
shocks caused by the fall of hard objects
• Long-term durability compared to bitumen asphalt
in the tropics
• Early operation
• Long-term durabilityoftheconcretesurfaceinareas
with freezing and cold cycles of garlic
• Save fuel consumption and remove contaminants
during cooking and transporting asphalt
• Resistant to spills of petroleum products,
hydrocarbons and acids.
1.15. High performance concrete (HPC)
This type of concrete, which is called (super concrete) has
one of the following strength properties:Its 4-hour
compressive strength must be equal to or greater than 175
Kg / cm2 (initial early resistance). Its compressive strength
after 24 hours should be equal to or greater than 2350 Kg /
cm (initial strength of concrete). The 28-day compressive
strength must be equal to or greater than 700 Kg / cm2The
ratio of water to cement is less than 35%.
2. Concrete Admixtures
It should be noted that concreting in the air has its own
problems and difficulties. One of these problems in cold
weather is the problem of concrete freezing, in which the
water in the concrete freezes and prevents hydration
operations. In general, it should be noted that low
temperatures cause hydration to occur at a slower rate. In
this way, the whole process of concreting and obtaining
concrete strength faces many problems. The result can be a
reduction in the durability and strength of the concrete,
which makes the structureunsuitable forthe use of whatitis
designed for. In the long run, cracks may appear in the
concrete or the concrete may form in the form of laminates,
which are not structural engineers at all. To solve this
problem, various ideas have been proposed, the most
important of which is the use of antifreeze. Antifreezes make
hydration work well and also in cold weather can reach a
suitable and desirable concrete so as not to reduce the
strength of the structure and can be used easily and without
any problems from the existing structure. For a full
explanation, I must say that another name for shotcrete is
spray concrete, and as its name implies, this concrete is
sprayed on the desired surface. It should be noted that this
type of concrete is used to repair existing structures as well
as work that does not require formwork or complex shapes
with low thickness.
It is commonly used for the inner lining of tunnels, tanks and
prestressed concrete tanks, and other uses for stabilizing
sloping rock cliffs include covering steel plates to create fire
shields. You may be wonderingwhatthepurposeofshotcrete
is and what can be done with ordinary concrete! It should be
noted that the purpose of making shotcrete is to make our
final product have high strength and very low permeability.
One of the main characteristics of concrete that is always
mentioned is its high ductility (although you may not have
imagined that concrete is so flexible, of course, this is before
the concrete hardens) and in fact shotcrete is one of the best
uses. Our properties are unique to concrete. To answer this
question, it must be stated in which structure concrete is

used. In buildings, in all structural elements of the structure,
such as beams and beams, structural foundations and shear
walls, etc., the use of rebars or reinforcement is mandatory
because rebars against the behavior of concrete structures
against Improves lateral loads and gravity loads. As you
know, concrete has a very weak action against tensile, so the
use of rebar in the tensile areas of the structure is a basic
requirement, and in addition, according to the structural
designer, the use of concrete in the compressive parts of the
structure also causes the performance of the structure will
improve. Rebars are an integral part of concretestructures,it
should be noted that in some cases concrete will not need
reinforcement. Like when weuse concreteexceptforleveling
under the foundation. As a result, the use of reinforced
concrete, ie concrete with reinforcement, is mandatory in all
parts of buildings. Yes, it can be done, but it must be said that
the opinion of the executor is very important and you cannot
add any amount of water to the concrete. Water should be
mixed with cement in a certain amount and should not be
more or less than the allowable limit, which iscalledtheratio
of water to cement. If more or less water is added to the
concrete, it will change the strength (decrease in strength)of
the concrete and the concrete will become too fluid, which
will lose its structural and load-bearing performance,
therefore the ratio Water to cement is very important and
must be observed. If we want the concrete to be smoother,
we should not use water and instead it is better to use
concrete Admixtures. Addition of materials other than
Portland cement, aggregates, and water, in the form of
powder (round) or liquid (watery), as one oftheconstituents
of concreteand to improve thepropertiesofconcrete,shortly
before mixing, during mixing or before it is added from
pouring. In other words, Admixtures are components of
concreteother than hydraulic cement, water,aggregatesand
fibers that are added to concrete to improvethepropertiesof
fresh and hardened concrete and mortar. Concrete
admixtures are divided into two groups: chemical and
mineral Admixtures. Chemical Admixtures are obtained by
processing, mixing, or blending organic and inorganic
materials in a chemical processandinpowderorliquidforms
and in small amounts, usually up to 5% by weight of
cementitious materialat thetimeoffabricationandmixingor
just before pouring concrete. Mixtures are added. Mineral
Admixtures, which are either naturally occurring or
industrial by-products, are divided into three categories:
inert materials, pozzolans, and cementitious materials [1],
and to improve the properties of cementitious mixtures in
general consumption amounts of more than 5%. The weight
of the cement is added to the concrete during mixing. The
scope of this publication (article) includes chemical
Admixtures in concrete and the study of mineral Admixtures
is entrusted to other publications of the Iranian Concrete
Association.
2.1 Interaction of concrete and chemical Admixtures
Chemical Admixtures interact with hydrated cementitious
materials andare dividedintothreecategoriesofAdmixtures
with physical, chemical, and physico-chemical performance.
AdmixtureswithaphysicalfunctionarechemicalAdmixtures
that do not have a direct effect on the cement dewatering
reaction process, although they may affect its process and
rate. These Admixtures generally show their effect and
function before the initial setting of concrete and their effect
does not continue after setting in hardened and hardened
concrete. These Admixtures includewaterreducers,aerobes,
gas generators, foaming agents, aerators, anti-scouring
agents, pumping facilitators, colorants, and bonding agents.
Admixtures with chemical function either affect the process
and reaction process of pre-setting cement dewatering or
alter the microstructure of dewatering products before and
after setting. Therefore, in addition to the pre-setting time,
the reaction of chemical Admixtures may continue in the
hardening stages of concrete.
Slow retardants, retarders, quick hardeners, expanders,
dehydration reaction controllers, and inhibitors are among
the Admixtures with chemical function. Physico-chemical
Admixtures Although they donot interfere withthechemical
reaction process of cement dewatering, they control some of
the chemical reactions or physical behaviors of hardened
concrete in the future by injecting special chemicals into the
concrete. Corrosion inhibitors, silica alkaline reaction
expansion reducers, sealants, permeation reducers,
fungicides, microbicides, and insecticides fall into this
category of Admixtures.
2.2 Classification of chemical Admixtures
Chemical Admixtures are divided into seven general
categories based on the type of effect and the main function
they have in concrete.
2.3. Water reducers
Reducing Admixtures are used to increase the fluidity of
concretein a given amount ofwater, or to reduce theamount
of water consumed by maintaining fluidity, or both, and
include lubricants, superplasticizers, and transducers.
2.4. Air content
It is an additive that, during mixing, creates a homogeneous
structureof discontinuous microbubblesinconcrete,mortar,
or cement paste, improving efficiency (workability) and
increasing reliability against freezing and thawing cycles.
2.5. Slow down
Retarders delay the setting of concrete by slowing down the
dewatering process of the cement and include retarders and
retarders.

2.6. Accelerators (accelerators)
Accelerators accelerate, harden, or both accelerate the
cement dewatering process. Accelerators include
accelerators, stimulators, and accelerators.
2.7. Expanders
Expanders are used to increase the volume of fresh concrete
(mortar), compensate for shrinkage of hardened concrete
(mortar), or create controlled expansion in hardened
concrete (mortar). These Admixtures include shrinkage
compensators, gas generators, and foaming agents.
2.8. Sustainers
Fasteners improve the reliability of hardened concrete by
reducing the penetration of harmful agents, monitoring
rebars, or controlling harmful reactions. Permeation
reducers, sealants, corrosion inhibitors, and silica alkaline
reaction expansion reducers are included in this category of
Admixtures.
2.9. Special add-ons
Special Admixtures are a group of chemical Admixtures with
special and limited use. Antifreezes, colorants, aerators,
pumping facilitators, anti-scourers, dehydration reaction
controllers, latexes, and thickeners are examples of special
Admixtures.
2.1O. Function of chemical Admixtures
Each additive is defined and grouped according to its main
function. The main function of an additive is the main
expected effect it has on concrete and indicates the
performance of its additive index. An ancillary functionisthe
effect or effects that the additive has on the concrete on a
smaller scale than the main function. Some Admixtures may
be multi-purpose and affect several properties of fresh or
hardened concrete. For example, damping waterreducers,in
addition to reducing the amount of water,alsoslowdownthe
concrete. Tip 1-1- Some Admixtures may have side effects.
For example, the main function of water-reducing
Admixtures is to reduce the water content of concrete, but
they may also have side effects of slowing or aerobic. Side
effect is an unwanted and, in some cases, even undesirable
effect that the additive has on the properties of concrete and
it should be remembered that it is different from the sub-
function. Tip 1-2 - The increasing expansion of Admixtures
and their effective applications maylead to the emergenceof
new Admixtures that do not fit into this weekly
categorization. In such cases, the role of regulations,
instructions and special technical specifications issued by
manufacturers or reputable international scientific societies
have a special place for the evaluation and acceptance of
these Admixtures and are a criterion for measuring this type
of material.
2.11. Reasons and benefitsof usingchemicalAdmixtures
Concrete must be homogeneous, efficient, payable, durable,
reliable, and low permeability. In many cases, these
characteristics can be achieved by selecting the appropriate
materials and mixing ratios and applying the methods and
using the appropriate equipment and experienced people.
The use of chemical Admixtures, along with their numerous
benefits, will make it possible and easier to achieve these
properties.
Figure 4. Admixture
In this regard, the most important reasons and benefits of
using chemical Admixtures can be categorized as follows.
3. Effect of Concrete Admixtures
3.1. Reduce construction costs
The use of Admixtures can lead to various savings and in
addition to offsetting the costs of purchasing Admixtures, it
canalsobringeconomicbenefits.Reducingconstructioncosts
is divided into three categories: direct, indirect, and covert
savings. Direct savings are part of the cost reduction that can
be easily calculated and measured. These savings include
reducing the amount of cement and water, increasing the
productivity of manpower, reducing execution time,
facilitating and increasing the efficiency of concrete
operations, enabling the use of available aggregates and
materials, facilitating the transfer and pouring of concrete,
speeding up the opening And ease in many other executive
cases. Indirect savings include reducingthecostofimproving
concrete quality, increasing mechanical strength, ensuring
uniformity of production, reducing problems and
shortcomings during execution, reducing or eliminating
rework, improving the appearance and reducing repairs of
concretesurfaces, and countlessotherthings.Hiddensavings
include reducedinvestmentcosts.Theseincludereducingthe
depreciation of equipment and machinery, reducing the
volume and dimensions of structural members, the
possibility of various designs, optimal use of land by
designing taller structures, and the possibility of eliminating
the facade. Each of the add-ons mayprovideonlyoneormore

economic benefits that should be considered when
calculating the cost savings.
3.2. Adjustmentandimprovementofconcreteproperties
Although many desired properties of concrete can be
achieved by choosing the right materials and mixing ratio,
adjusting and achieving some properties of fresh and
hardened concrete using Admixtures is more efficient,
economical, and more effective than any other method. With
the use of chemical Admixtures, the properties of fresh
concretecan be adjustedinaccordancewiththeperformance
and environmental conditions, and the properties of
hardened concrete can be modified in accordance with the
technical criteria and operating conditions. Properties of
fresh concrete that can be adjusted using chemical
Admixtures include: Increase efficiency without additional
water consumption, Reduce water consumption without
reducing efficiency, Accelerate or slow down initial and final
setting, Expand to compensate for shrinkage, Reduce water
drop Maintainconsistency, reduce grainseparation,improve
pumping, correct slump loss, and control exotherm at an
early age. Properties of hardened concrete that can be
modified or improved by the use of chemical Admixtures
include: Acceleration or delay in the process of gaining
strength,Increasedmechanicalstrength,Improvedreliability,
Reduced permeability, Expansion control and Alkaline
reaction damage Increase adhesion to steel, improve
adhesion of new concrete to existing concrete, produce
concrete or colored mortar, and control rebar corrosion.
3.3. Ability to run in difficult conditions
Some chemical Admixtures allow the implementation and
continuation of concreting operations, while maintainingthe
required quality, inadverseweatherconditions.Forexample,
with the use of retardant lubricants, concrete can be
transported over long distances or pumped over long
distances; Aggregates and anti-scouring make underwater
concreting operations easier;Quick heaters allowconcreting
in cold weather; And with thehelpofdecongestants,concrete
can be applied in low access points, such as turbine water
supply pipelines in hydroelectric power plants, without the
need for vibration (self-compacting concrete).
3.4. Overcoming sudden events
During concreting operations, there is a possibilityofsudden
and unforeseen events such as clogged pump pipes, mold
collapse, sudden drop in temperature, etc. Some of these
events can be overcome with the help of chemical
Admixtures. An example of this is the use of dewatering
control materials to prevent clogging and reuse of built-in
concrete in cases where there are interruptions.
3.5. Coordination with environmental and occupational
health issues
Reducing noise pollution, increasing the safety and
productivity of labor (manpower), reducing heat from
friction of equipment and machinery, not throwingawayand
using the remaining concrete in the machinery for the next
shift (additive to control the need for water) The end of each
shift and the failure to drain the washing water in the
environment (non-stick additive), are among the items of
environmentalfriendlinessthatcanbeachievedwiththehelp
of chemical Admixtures.
3.6. Achieving special properties
Some properties of concrete, no matter how careful the
choice of materials and proportions of concretecomponents,
can not be achieved except with the use of Admixtures.
Among these unique properties and properties that can only
be achieved with the use of chemical Admixtures are
aerobics, foaming, self-compaction, acceleration, pre-
hardening, deceleration, and expansion.
3.7. Contribute to sustainable development
Reducing cement consumption on the one hand by saving on
the consumption of natural resources(rawmaterials)andon
the other hand by reducing greenhouse gases from cement
production, in order to help preserve the environment and
sustainable development.Achievingearlyresistancebyusing
Admixtures and eliminating the need for evaporation in the
process of manufacturingprefabricatedparts,called"energy-
free", leads to energy savings and contributes to sustainable
development. Improving thereliabilityofconcretestructures
during operation, which is achieved due to the use of
Admixtures, will also contribute to sustainable development
by increasing the useful life of the structure. Note 1-3-
Regardless of all the above, it should be remembered that no
Admixtures of any type and amount can be considered as a
substitute for the design of concrete and proper execution of
concrete.
3.8. Specifications of chemical Admixtures
Consumable Admixtures must meet the needs and criteria of
concreteregulations and national standardsofIranandvalid
international standards such as AASHTO, ASTM, BS, DIN, EN.
These sources describe in detail the technical specifications,
minimum consumption expectations, and how each additive
is effective, and are a very good guide for using Admixtures.
In addition to these standards, manufacturers of these
Admixtures always provideaccuratetechnicalspecifications
of their products and the range of consumption and their
effect on concrete, which in some cases can be helpful.

Figure 5. Size of materials
Although the technical specifications provided by the
manufacturers include the range of consumption proposed,
but the amount of additive consumption should be
determined based on the results obtained with the materials
used in the workshop.
3.9. Evaluation of Admixtures
Since the composition and properties of cementitious
materials, water and aggregates as well as their mixing ratio
have a significant effect on the performance of Admixtures,
the evaluation of eachadditive shouldbebasedontheresults
obtained with the materials used in the workshop. In
evaluatingan additive, its effect on the volume of themixture
must be considered. If the addition of the additive changes
the volumetric yield of the mix, as often happens, the change
in the properties of the concrete will not be due to the direct
effects of the additive alone and may also be due to a change
in the proportion of concrete components. In such cases,
Admixtures such as cement, aggregates and water should be
considered as one of the components of concrete in the
mixing plan. If more than one additive is used in concrete,
they may affect each other's performance. For example, in
concrete with aerobic Admixtures, the use of lubricant can
increase aerobic efficiency,whilesomedecongestantsreduce
its efficiency. In evaluating Admixtures, their interaction on
each other's performance should be considered.
Environmental factors such as temperature and humidity
have a significant effect on the behavior of concrete and the
performance of Admixtures. Admixtures that are known to
work at normal temperatures may have very different
functions at very high or very low temperatures. The
performance of each additive should be evaluated under the
expected environmental conditions at run time and not be
limited to laboratory results performed at standard
temperatures. In evaluating the performance of Admixtures,
operating conditions such as how and when to mix, how and
when to transport, temperature of fresh concrete, how to
pour and spread concrete, how to compact and polish
concrete,and the method of processingshouldbeconsidered
because each of these can Affect additive function. For
example, excessive mixing reduces the efficiency of aerobes.
The time and manner of adding Admixtures to the concrete
mix also affect their performance, which should be
consideredintheirevaluation.Forexample,ifwater-reducing
Admixtures are added to the dry mix of cement and
aggregate, their efficiency will be greatly reduced, whereasif
they are added to the concrete after adding a portion of
mixing water and cement paste, they will perform better.
Economics of each additive should be considered in the cost
of preparation, transportation, maintenance and addition
along with the economicsavings thattheadditivebringswith
it in the execution of concrete operations. Although the
function and the main effect of an additive on the properties
of fresh and hardened concrete is usually the main criterion
for evaluation and selection of Admixtures, but the side
advantages of each product are significant concrete
producers, contractors, executors and employers and is of
particular importance. These advantages include properties
such as efficiency (workability), ease of pumping and
molding, surface polishing, early resistance, faster use of
molds, appearance of concrete surfaces and elimination or
reduction of vibration time. For quality control of
Admixtures, in addition On the uniformity of appearance,the
uniformity of their performance on concrete should also be
evaluated.
3.10. Considerations in the use of Admixtures
Admixtures must comply with Iranian national standards or
other valid international regulations. In addition, the
instructions and recommendations provided by the additive
manufacturer must be carefully considered. The effects of an
additive should be evaluated as far as possible using the
intended materials in the workshop. This issue becomes
especially important when:
• The additive has not been used before with the desired
materials or their combination;
• Use of special types of cementitious materials;
• Consume more than one type of additive;
Mixing and concreting should be done at temperatures
outside the range usually recommended for concreting. In
addition, the use of Admixtures may require modificationsto
the concrete mixing design, such as changes in the type or
amount of cement, changes in the type or aggregation of
aggregates, or modifications to the mixing ratio. Byadjusting
the amount of water and cementitious materials and
modifying the type anddurationofmixing,theeffectsofsome
Admixtures are dramatically improved.
Many Admixtures affect more than one property of concrete
and may even adversely affect the desired properties.
Admixtures that improve the properties of fresh concrete
may cause premature hardening or excessive slowing of the
concrete and cause problems. By examining the effect of
Admixtures on the cementitious materialsused,thecausesof

abnormal setting behaviors can be understood. Premature
hardening often occurs due to a change in the reaction
process between the existing tricalcium, aluminate, and
sulfate ions. Excessive retardation can be due to delayed
calcium silicatedehydrationdue to overuse oftheadditiveor
decrease in ambient temperature. Another important
consideration in the use of Admixtures is the limitationofthe
allowable amount of chlorine ions in concrete. These
restrictions are given in the Iranian Concrete Regulations.
These limitations are usually expressed as the maximum
percentage of chlorine ions relative to the mass (weight) of
the cement, although sometimes the amount of "water-
soluble" chlorine ions in concrete is also measured.
Regardless of how thislimit isset,theconsumershouldknow
the amount of chlorine ions in the additive so that when
determining the type and amount of additive consumption,
he does not exceed the limits set for the amount of chlorine
ions. Tip 1-6 - The user should be aware that even assuming
that chlorine ions are not present in the structure of a
chemical additive, there is always the possibility of chlorine
ions entering through the water used to produce the liquid
additive, as Admixtures are often made with water that
contains Small but measurable amounts of chlorine ions.
Therefore, caution should be exercised when dealing with
terms such as "chlorine free".
13. CONCLUSION
Admixtures are chemicals that are added to the
mixture in small amounts and as a percentage of the weight
of cement to create the desired properties in concrete.
W represents water and C represents the weight of
cement, so that a low W / C ratio can be selected.
Tricalcium silicate: (3Cao-Sio2) abbreviated (C3S),
Calcium silicate: (2Cao-Sio2) abbreviated (C2S), Tricalcium
aluminate: 3Cao-Al2o3) with the abbreviation (C3A),
Aluminophytetetracalcium:(4Cao-Al2o3-Fe2o3)abbreviated
(C4AF).
The main reason for using fibers in concrete is to
increase the hardness and tensile strength, improve crack
The use of seawater due to the presence of salts of
chlorides, sulfates, etc., which reduces the strength by up to
15%, and on the other hand, the chlorine in seawater causes
corrosion of rebars over time and its use in reinforced
concrete is not allowed. .
Silica aggregates have a hardness of 7 to 8 and are
the most resistant aggregates used in concrete. Limestone
grains have a hardness of 3 to 4 which are used in making
concrete.
It seems that after concreting and polishing the
concrete surface, a thin layer of water impregnated with
cement appears on the concretesurface. The mostimportant
reason is excessive slump. Another reason, such as excessive
vibration and inadequategranulation,increasethelikelihood
of concrete melting.
Reinforced concrete is brittle and has less tensile
strength. In order to reduce the weakness of fragility, thin
and short filaments that are randomly distributed in all
directions in concrete are a very suitable method (these thin
filaments are called fibers).
Foam concreteduring their constructionbycreating
foam, air bubbles in the cement paste or in the cement
mortar, aggregates are created. Specific mass (Kg / m3).
Concrete with light grains which are made using
perlite or vermiculite or expandable polyester fibers. The
specific gravity of this mixture (Kg / m3 960 to 240).
14. REFERENCES
[1]. IS: 6491-1972,MethodsforsamplingofFlyash,Bureauof
India standards, India.
[2]. Tattersall G.H. and P.F.G. Banfill, 1983, Rheology of fresh
concrete, pitman advanced publishing program.
[3]. Sandor Popovics., 1993, Portland Cement-Fly Ash-Silica
Fume Systems in Concrete, journal of Elsevier Science
Publishing Co, Vol 1065-7355193156.00.
[4]. Okamura, H. and Ozawa, K. 1999, Mix design for self-
compacting concrete, concrete library of Japanese society of
civil engineering, June 25, , pp, 3-14.
[5]. Michael F Ashby and David R H Jones, 2002, Engineering
Materials 1, Linacre House, Jordan Hill, Oxford OX2 8DP, 225
Wildwood Avenue, Wobum, MA 01801-204.
[6]. Nielsen, P.K. 2003, handbook of nondestructive testing
equipment for concrete, federal highway administration,
Washington, D.C.
[7]. Terence C. Holland, 2005, Silica Fume User’s Manual,
Federal Highway Administration, Washington.
[8]. R.S. Khurmi and N. Khurmi, 2008, Strength of Materials,
Ram Nagar, New delhi-110055, India.
[9]. L S Negi, 2008, Strength of Materials, A.P. offset Pvt.,
25/487, Zulf-e- Bengal, Dilshad Garden, New Delhi-110095,
India.
[10]. S. Chand, 2008, Concrete Technology, Ram Nagar, New
Delhi-110055, India.
[11]. Arnon Chaipanich, Thanongsak Nochaiya., 2009,
Thermal analysis and microstructure of Portland cement-fly

ash-silica fume pastes, journal of Therm Anal Calorim, Vol
(2010) 99:487–493.
[12]. Ken Ward-Harvey and ASTC, LFRAIA, 2009,
Fundamental Building Materials, Universal-Publishers, Boca
Raton, Florida, USA.
[13]. M L Gambhir, 2009, Concrete Technology, New Delhi,
India.
[14]. Ken Ward-Harvey and ASTC, LFRAIA, 2009,
Fundamental Building Materials, Universal-Publishers, Boca
Raton, Florida, USA.
[15]. Braja M.Das, 2013, Foundation Engineering, cengage
learning india private limited, 418, F.I.E., Patparaganji, New
Delhi, India.
[16]. Dr. R.K. Bansal, 2014, Strength of Materials, 113,Golden
House, Daryaganj, New delhi-110002, India.
[17]. P. Kumar Mehta and Paulo J. M. Monteiro, 2014,
Concrete Microstructure, properties and Materials, P-24
Green Park extension, New Delhi-110016, India.
[18]. S.P. Timoshenko and D.H. Young, 2015, Elements of
Strength of Materials, 105 Nirmal Tower, 26 Barakhamba
Road New Delhi-110001, India.
BIOGRAPHIES
“Masood Jamali is currently employee
of Ministry of mine and petroleum as
general construction manager. He
completed master degree ME
(Construction Technology &
Management) in Civil Engineering
Department of Chandigarh University
Mohali, Punjab, India. However,
completed his BTech in Civil
Engineering Faculty from Dawat
University in 2016”
“Khalil Rahman Farhat is currently
employee of Swedish Committee for
Afghanistan as construction specialist
at The Area Based Approach to
DevelopmentEmergencyInitiatives.He
completed master degree ME
(Construction Technology &
Management) in Civil Engineering
Department of Chandigarh University
Mohali, Punjab, India. However,
completed his BTech in Civil
Engineering Faculty from Nangarhar
University in 2014”

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