Concrete admixtures


Plasticizers

         Water reducers
         Organic, or combination of organic and inorganic substances
         Dosage 0.1 to 0.4 % by weight of cement
         Entrained air which is not more than 1 to 2 %
         Anionic surfactants such as lignosulphates and their modifications and derivatives, salts of sulphonates, hydrocarbons.
         Nonionic surfactants such as polyglycol esters, acid of hydroxylated carboxylic acid and their modification and derivatives.
         Other products such as carbohydrates etc.
         Calcium, Sodium, Ammonium lignosulphonates are mostly used.


Superplasticizers

         High range water reducers
         Dose varies from 0.5 to 3 % by weight of cement
         They do not entrain air
         Reduction of water up to  15 to 30 %
         Sulphonated malanie form aldehyde condensates (SMF)
         Sulphonated naphthalene formaldehyde (SNF)
         Modified lignosulphonates (MLS)
         Other types


Factors affecting the workability of concrete in case of use of Plasticizer or Super plasticizer

         Type of Plasticizer or Super plasticizer
         Dosage
         Mix composition
         Variability in cement composition
         Mixing procedure
         Equipment
         Others
Site problems in the use of Superplasticizer

         Slump loss- Initial high slump, Using Retarders, By repetitive dose, By dosing at final point, By keeping temperature low, By using compatible Superplasticizer
         Problem with crushed sand
         Sequence of addition of Superplasticizer
         Type of mixer
         Importance of shape and grading of aggregates
         Casting the cubes
         Excessive segregation, Retardation


Retarders
Applications
1.     Hot weather concreting
2.     Grouting oil wells
3.     RMC Plants
4.     To exposed the aggregates
5.     Concreting for joints
Material
         Most commonly used Calcium sulphate (Gypsum)
         Starches, cellulose material, sugars, acids or salts of acids
         Common sugar- 0.2 %
         Lignosulphonic acid and their salts, hydroxylated carboxylic acid and their salts, Mucic acid, calcium acetate.


Accelerators
Application
         Permit early removal of formwork.
         Reduced the required period of curing.
         Advanced the time that which structure can be placed in service.
         Cold weather concreting
         In emergency repair work
         Under water concreting
Material
         Calcium chloride- not more than 0.4 %
         Soluble carbonates, silicates, fluosilicates and some of the organic compounds.


Air entraining agents

         Natural wood resin.
         Animal and vegetable fat oils such as tallow, olive oil and their fatty acids such as stearic and oleic acid.
         Various wetting agents such as alkali salts or sulphated and Sulphonated organic compounds.
         Water soluble soaps of resin acids and animal and vegetable fatty acids.
         Miscellaneous materials such as sodium salts of petroleum, sulphonic acids, hydrogen peroxide and aluminium powder etc.


Factors affecting amount of air entrainment

         Type and quantity of air entraining agent
         W/C ratio of the mix
         Type and grading of aggregate
         Mixing time
         Temperature
         Type of cement
         Influence of compaction
         Admixtures other than air entraining agent


Effect of air entrainment on properties of concrete

         Increased resistance to freezing and thawing
         Improvement in workability
         Reduction in strength
         Reduces segregation and bleeding.
         Reduces permeability
         Reduces alkali aggregate reaction
         Increases resistance to chemical attack
         Reduces sand content, cost and heat of hydration
         Reduces unit weight of concrete
         Improves abrasion resistance


Optimum air content in concrete

         Depends upon purpose for which concrete is used, its location and climatic conditions, maximum size of aggregates, and richness of mix.
         Usually ranges from 3 to 6 %
         lower air content for floors
         For surfaces exposed to atmosphere 3 to 4 %
         For mass concrete 3%
         Gravimetric method
         Volumetric method
         Pressure method




Chemical requirements of fly ash as per IS 3812 part I 2003


Physical requirements
Sr. No.
Characteristics
Requirement values
1
Fineness Specific surface in m2/Kg
320
2
Compressive strength at 28 days in N/mm2, Min
Not less than 80 % of corresponding plain cement mortar cubes
3
Lime reactivity – Avg compressive strength in N/mm2
4.5
4
Soundness by autoclave test expansion of specimens % Max
0.8


Oxide composition of cement clinker, fly ash and GGBS
Sr. No.
Constituents
Percentage content
Cement clinker
Blast furnace slag (IS 12089- 1987)
Fly ash
1
Lime CaO
60-67
30-45
1.0-3.0
2
Silica SiO2
17-25
30-38
35-60
3
Alumina Al2O3
3.0-8.0
15-25
10-30
4
Iron Oxide Fe2O3
0.5-6.0
0.5-2.0
4-10
5
MgO
0.1-4.0
4.0-17.0
0.2-5.0
6
MnO2
-----
1.0-5.0
---------
7
Glass
------
85-98
20-30
8
Sp. gravity
3.15
2.9
2.1-2.6


Silica fume

         Undensified form with bulk density 200 - 300 Kg/m3
         Densified form with bulk density 500- 600 Kg/m3
         Micro palletized form with bulk density 600 -800 Kg/m3
         Slurry form with bulk density 1400 Kg/m3
         It must confirm the requirements of IS  15388 –2003 or ASTM C 1240 -2000
         At least 85% of silicon dioxide in non crystalline form.
         Particle size with diameter in between  0.1 to 0.2 micron
         Min specific surface area is 15000 m2/kg
         Spherical particle shape
         Sp. Gravity 2.2
     In India marketed by Elkem metallurgy Ltd. Vashi Navi Mumbai, M/s Mc-Bauchemie Pvt Ltd under the trade name Centrilit fumes (Slurry form)


Rice husk ash

         Silica 85 % min
         Moisture content 2 % max
         Particle size 25 micron
         Colour grey
         Ph value 8
          
Characteristics
Supplementary Cementitious materials
Silica fume
Metakaolin
RHA
Silica
90-94
48-55
92
Alumina
1-3
40-45
0.5
Iron oxide
1.5-2.5
1-2
0.2
Lime
0.5
2-4
0.5
MgO
1-3
0.12-1
0.5
Alkalies
< 2
< 0.5
2-4
Fineness m2/g
25-27
15-20
20-25


Metakaolin
Characteristic
Value
Silica (Wt %)
48-55
Alumina
40-45
Iron oxide
1-2
Lime
2-4
MgO
0.12-1
Na2O
< 0.5
K2O
< 2
Loss of ignition
15-20
Fineness m2/g
48-55


Surkhi / Calcined clay pozzolana
IS 1344 1981 For use in mortar/ concrete
IS 1727 1967 Testing of material


Construction chemicals for water proofing

         Integral water proofing compounds
         Acrylic based polymer coatings
         Mineral based polymer modified coating (Slurry coating)
         Chemical DPC for rising dampness
         Water proofing adhesives for tiles, marble and granite
         Silicon based water repellent material
         Injection grout for the cracks
         Protective and decorative coatings
         Joint sealants


Integral water proofing compound

         These compounds are added in the concrete during mixing as like admixtures.
         These are basically pore fillers, water repellent and reduce the water cement ratio of the concrete which will make concrete dense.
         Main materials in the pore filling class are Silicate of soda, Aluminum and zinc sulphates and Aluminum and Calcium chloride. Chemically inactive pore filling materials are Chalk, Talc.
         Materials like Soda, Potash soaps, Calcium soaps, Resin, Vegetable oils, fats, waxes are water repelling materials.
         They are quite economical for the structure which is continuously wet or under damp conditions.

         Mc-Bauchemie (Ind) Pvt ltd.
1.     Mc- special DM
2.     Dichtament DM
3.     Putz- Dichtament

         Fosroc chemicals Pvt ltd
1.     Conplast prolapin 421 IC
2.     Conplast prolapin I-P
           Performance requirement are covered in IS 2645-1975


Acrylic based polymer coating

         Temperature changes causes expansion and contraction of concrete which causes cracking
         Concrete cracks due to drying shrinkage
         Inadequate design i.e. less reinforcement
         Unequal settlement
         Available under the trade name Roofex 2000 which is produced by Mc-Bauchemie (Ind) Pvt ltd.
         White in colour and mainly applied by brush or spray


Mineral based polymer modified coating

         Slurry coatings is formed by mixing hydraulically setting powder and liquid polymer component.
         This coating requires curing one week or so.
         Used mainly for terrace gardens, parking places, basements, swimming pools and sanitary area.

         Mc-Bauchemie (Ind) Pvt ltd
1.     Dichtament DS
2.     Dichtament DS-flex
3.     Zentrifix

         Fosroc chemicals Pvt ltd
1.     Brush bond
2.     Xypex


Protective and decorative coating

         Used in case of very thin members like roof tiles, Chajjas, sunshades etc.
         Mainly used as protective and decorative coating 
         Acrylic based polymer product
         Mc-Bauchemie (Ind) Pvt ltd
1.     Emcecolour flex
         Fosroc chemicals Pvt ltd
1.     Dekguard S


Chemical DPC for rising dampness

         Control the capillary rise in the external walls of the building.
         Chemicals are injected at some interval which will control the capillary action of water
         Mc-Bauchemie (Ind) Pvt ltd
1.     Samafit VK1
2.     Samafit VK2


Water proofing adhesives for tiles, marble and granite

         Used as adhesives for tiles
         These materials are having very good adhesion or bond strength, water proofing qualities and strength and durability.
         They are mostly used for exterior tiling works.
         Mc-Bauchemie (Ind) Pvt ltd
1.     Zentrival PL – for glazed and ceramic tiles
2.     Zentrival HS- For marble and granite
         Fosroc chemicals Pvt ltd
1.     Nitobond EP
2.     Nitobond PVA
3.     Nitotile SP


Silicon based water repellant Materials

         They are mainly used to maintain the architectural beauty of the structures.
         They will form a thin water repellant transparent film on th surface.
         The treatment may have to be repeated at closer intervals say 3 to 4 years.
         It is not that much costly material.
         Material is covered in IS 12027- 1987.
         NISIWA SH  by Mc-Bauchemie (Ind) Pvt ltd


Injection grout for cracks

         Expansive cement
         Used for repair, remove the leakages  and water proofing
         Suitable for gravity as well as pressure grouting
         Centicrete and Conbex 100 produced by Mc-Bauchemie (Ind) Pvt ltd , Fosroc chemicals Pvt ltd respectively


Joint sealants

         Any contraction or expansion joint
         Joints of doors and window openings
         Joints of sanitary appliances
         Fosroc chemicals Pvt ltd
1.     Nitoseal 215
         Sika chemicals
1.     Sikalastic
2.     Sika-S11A
3.     Sikacryl GP
         Roff chemicals
1.     Qualcrete
2.     Saniseal


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