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Presentation by Mustafa
Uploaded By: Engr.Ahmad Sameer
- Materials other than cement, water & aggregates
added to the concrete mix to modify & to improve
specific properties of concrete.
Materials used as admixtures included milk and lard
by the Romans; eggs during the middle ages in
Europe; polished glutinous rice paste, lacquer, tung
oil, blackstrap molasses, and extracts from elm
soaked in water and boiled bananas by the Chinese;
and in Mesoamerica and Peru, cactus juice and latex
from rubber plants. The Mayans also
used bark extracts and other substances as set
retarders to keep stucco workable for a long period
History of Admixture
1. To improve workability of fresh concrete.
2. To improve durability by entrainment of air.
3. To reduce the water required.
4. To accelerate setting & hardening to produce high early
5. To aid curing.
6. To improve water proofing property.
7. To cause dispersion of the cement particles when mixed
PURPOSE OF ADMIXTURE?
8. To retard setting.
9. To improve hardness .
10. To reduce shrinkage during setting & hardening.
11. To cause expansion of concrete and automatic
prestressing of steel.
12. To aerate mortar / concrete to produce a light – weight product.
13. To impart color.
14. To reduce some chemical reaction.
15. To reduce bleeding.
16. To reduce the evolution of heat .
“a material other than water, aggregates, hydraulic
cement, and fiber reinforcement, used as an
ingredient of a cementitious mixture to modify its
freshly mixed, setting, or hardened properties and
that is added to the batch before or during its
Chemical definition of Admixtures
1. Air-Entraining Admixtures
2. Water-reducing admixtures
3. Retarding admixtures
4. Accelerating admixtures
5. Super plasticizers
6. Corrosion-inhibiting admixtures
Common Types of Chemical
Air-entraining admixtures are used to stabilize
microscopic air bubbles in concrete. Proper air-
entrainment, with appropriate volume and spacing
factor, will dramatically improve the durability of
concrete exposed to moisture during of freezing and
Entrained air also improves concrete’s resistance to
surface scaling caused by chemical deicers.
MB-AE 90 air-entraining admixture is for use in concrete
mixtures. It meets the requirements of ASTM C 260, AASHTO M
154 and CRD-C 13.
Ready-to-use – in the proper concentration for rapid, accurate
Improved resistance to damage, from cyclic freezing and thawing
Improved resistance to scaling from, deicing salts
Improved plasticity and workability
Reduced permeability – increased water tightness
Reduced segregation and bleeding
Water-reducing admixtures usually reduce the
required water content for a concrete mixture by
about 5 to 10 percent. Consequently, concrete
containing a water-reducing admixture needs less
water to reach a required slump than untreated
concrete. The treated concrete can have a lower
water-cement ratio. This usually indicates that a
higher strength concrete can be produced without
increasing the amount of cement.
Recent advancements in admixture technology have
led to the development of Mid-range water reducers.
These admixtures reduce water content by at least 8
percent and tend to be more stable over a wider
range of temperatures. Mid-range water reducers
provide more consistent setting times than standard
Water-reducers are used to increase slump of concrete
without adding water and are useful for pumping concrete
and in hot weather to offset the increased water demand.
Water-reducing admixtures are used to improve the quality
of concrete and to obtain specified strength at lower
cement content. They also improve the properties of
concrete containing marginal- or low-quality aggregates
and help in placing concrete under difficult conditions.
Water reducers have been used primarily in bridge decks,
low-slump concrete overlays, and patching concrete.
SEMI CONCRETE BOND is a normal plasticizer, water
reducing admixture confirming ASTM C 494. type A
FEATURES AND BENEFITS
Lower water requirement for given workability.
Easier placing, better compaction and finishing.
Lower cement content for specified strength.
Increases strength and durability of concrete.
Reduces risk of segregation and bleeding.
Improves slump and reduces permeability.
Super Plasticizers Water Reducing
Admixture - Normal Plasticizer
SEMI CONCRETE BOND can be used to reduce
cement content to the extent of 8 to 10% by
maintaining the original strength specified
and workability and reducing water content required for the given
Can be used in precast concrete work, Mass concrete
work , Structural R.C.C. construction , Heavy
Density: 1.18+0.02 GM/c.c at 30o c.
Dose: 150 to 250 gm. / 50 kg cement
AREAS OF APPLICATION
Retarding admixtures, which slow the setting rate of
concrete, are used to counteract the accelerating effect of
hot weather on concrete setting. High temperatures often
cause an increased rate of hardening which makes placing
and finishing difficult. Retarders keep concrete workable
during placement and delay the initial set of concrete.
Most retarders also function as water reducers and may
entrain some air in concrete.
Retarders should meet the requirements for Type B or D in
ASTM C 494.
Accelerating admixtures increase the rate of early
strength development, reduce the time required for
proper curing and protection, and speed up the start
of finishing operations. Accelerating admixtures are
especially useful for modifying the properties of
concrete in cold weather.
pozzolith® 122 HE
Pozzolith 122 HE ready-to-use, liquid admixture is designed to make
more uniform and predictable quality concrete while accelerating
setting time and strength development. Pozzolith 122 HE admixture
meets ASTM C 494 requirements for Type C, accelerating, and Type E,
water-reducing and accelerating, admixtures.
Increased early and ultimate strengths – compressive and flexural
Reduced water content required for a given workability
Accelerated setting time characteristics
1. Improved workability
2. Superior finishing characteristics for flatwork and cast
3. Earlier finishing of slabs – reduced labor costs
4. Reduced protection time in cold weather
5. Earlier stripping and reuse of forms
6. Earlier structural use of concrete, as in lift-slab, tilt-up,
paving and floors
7. Easy to disperse in concrete mixtures, avoiding many
of the problems associated with flake calcium
Super plasticizers, also known as plasticizers or high-range
water reducers (HRWR), reduce water content by 12 to 30
percent and can be added to concrete with a low-to-
normal slump and water-cement ratio to make high-slump
flowing concrete. Flowing concrete is a highly fluid but
workable concrete that can be placed with little or no
vibration or compaction. The effect of super plasticizers
lasts only 30 to 60 minutes, depending on the brand and
dosage rate, and is followed by a rapid loss in workability.
As a result of the slump loss, super plasticizers are usually
added to concrete at the jobsite.
Corrosion-inhibiting admixtures fall into the specialty
admixture category and are used to slow corrosion of
reinforcing steel in concrete. Corrosion inhibitors can be
used as a defensive strategy for concrete structures, such
as marine facilities, highway bridges, and parking garages,
that will be exposed to high concentrations of chloride.
Other specialty admixtures include shrinkage-reducing
admixtures and alkali-silica reactivity inhibitors. The
shrinkage reducers are used to control drying shrinkage
and minimize cracking, while ASR inhibitors control
durability problems associated with alkali-silica reactivity.
Rheocrete 222+ patented state-of-the-art corrosion-inhibiting admixture
is formulated to prevent the corrosion of steel reinforced concrete.
Rheocrete 222+ admixture provides two levels of corrosion protection,
making it the most effective corrosion-inhibiting admixture available.
Inhibited corrosion at its most critical points
Reduces the rate at which chlorides and moisture enter the concrete
Adsorbed onto the reinforcing steel to form a corrosion-resistant protective
Extended service life of reinforced concrete structures
Premium corrosion protection by slowing the ingress of
chlorides and moisture into the concrete and forming a
strong, durable protective film on the reinforcing steel
Effective in cracked concrete where the elements that
cause corrosion have direct access to the reinforcing steel
Increased sulfate resistance
Normal set product that is easily used in elevated
-by adding to a hydraulic binder , gives very high
workability and allows a large decrease in water content
for a given workability.
1-enhances the hydration process
2-allows the particles to be more workable
3-prevent from segregation and bleeding.
Note: commonly used superplasticizer are napthalene
based, amino sulphuric acid,poly carboxylate super
1- Prolong/delay the setting time of cement paste in
2- used in hot weather to reduce any premature
stiffening of the concrete & consequent loss of
4- Consist of the general chemical types:
Calcium, sodium, potassium, or ammonium salts of
lignosulphonic acid Hydroxyls
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