Concrete admixtures

Chemical admixtures in Concrete

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

Chemical admixtures in Concrete