DESC:FIELD OF THE INVENTION
The invention relates to a skim coat composition. More particularly, the invention relates to a skim coat composition, comprising Fillers, Ordinary Portland cement, Organic polymeric binder, and Organic polymer, wherein fillers are by-product of cement manufacturing.
BACKGROUND OF THE INVENTION
The quantum of by products, such as cement kiln dust, ground granulated blast furnace slag, reverse air bag house dust, raw mill dust, and fly ash, produced from core-sector industries such as cement, power, steel, and other mining and heavy industries is increasing due to rapid industrialization. Consequently, the cost of disposing these by-products is also ever increasing due to stringent environmental regulations. The problem of disposal of such by-product materials is inevitable unless new and beneficial use options, which are economically viable and environmentally friendly, are developed and implemented.
Cement kiln dust (CKD) is one such by-product material of cement manufacturing industry. CKD is a fine-grained solid material generated as the primary by-product of the production of cement. Cement production occurs in very large rotary kilns at high temperatures; finely ground raw material enters and rolls downward from the “cool end” of the kiln, while fuels and combustion air are introduced and drawn upward from the “hot end.” This air that is drawn into and through the kiln carries with it some of the finely ground solid raw materials, condensed fuel components, and partially reacted feed. As this air exits the cool end, the carried solid matter is collected before the air is vented to the atmosphere, through the large gas emission “smokestacks” that are found at all cement production facilities. CKD generation results directly from this control of particulate matter that would otherwise be discharged into the atmosphere. Substantial quantities of CKD are being generated on a continuous basis at all cement plants. (Uses of CKD other than for flue gas desulfurization, By Tarun R. Naik, Fethullah Canpolat, and Yoon-moon Chun, A CBU Report for Holcim (US), September 2003).
Cement kiln dust (CKD) is a fine powdery material similar in appearance to portland cement. The principal constituents of CKD are compounds of lime, silica, and alumina, and iron. The primary value of cement kiln dust lies in its cementitious property. Therefore, CKD can be used as a partial replacement for other cementitious materials such as Portland cement, blast furnace slag cement, portland pozzolan cement, blended cements, and the like, thereby ensuring its productive usage.
US patent 6,645,290 B1 discloses compositions for general purpose concrete construction containing Class-F fly ash, Class-C fly ash or slag, and cement kiln dust as a substantial replacement for Portland cement conventionally used in such compositions. The resulting compositions provide high early strength thereby allowing the concrete structure to be put into service sooner, reducing labor cost, and allowing precast concrete and concrete masonry manufacturers to achieve rapid form and mold turnover.
Ground-granulated blast-furnace slag (GGBS or GGBFS) is obtained by quenching molten iron slag (a by-product of iron and steel-making) from a blast furnace in water or steam, to produce a glassy, granular product that is then dried and ground into a fine powder. As with cement kiln dust, disposal of slags has been a major concern for steel makers. In recent years however efforts have been made, to utilize slags in different fields such as, cement making, construction and fertilizers. The slag formation is the result of a complex series of physical and chemical reactions between the non-metallic charge (lime, dolomite, and fluxes) the energy sources (coke, oxygen, etc.) and refractory bricks. Because of the high temperatures (about 1500°C) in a blast furnace, slags are devoid of any organic substances. Generally, blast furnace slag’s are granulated and used in cement making due to their excellent cementitious properties.
US Patent 7,410,537 B2 discloses a process for the manufacture of Portland slag cement using cement clinker and higher proportion of ground granulated blast furnace slag, which is a waste material from steel plant. The process comprises mixing GGBFS in the range of 50 to 95% by weight, clinker in the range of 5 to 45% by weight, and gypsum in the range of 1 to 5% by weight.
In cement manufacturing, raw-mill is the equipment used to grind raw materials. The ground raw material is then fed to a cement kiln, which transforms it into clinker, which is then ground to make cement in the cement mill with the addition of required amount of gypusm. The raw-milling stage of the process effectively defines the chemistry (and therefore physical properties) of the finished cement, and has a large effect upon the efficiency of the whole manufacturing process. During raw milling, a large amount of dust having a composition that is almost similar to that of the raw materials is produced. Hence, raw mill dust is another type of particulate by-product that is produced during the manufacturing of cement. As raw-mill dust is generated from the raw materials of cement, it has cementitious properties. As with other by-products, raw mill dust poses a problem of safe and environmentally friendly disposal.
A reverse air bag house (RABH) is a dust collector which accepts dust laden gases, filters it, collects the dust and discharges the clean air. It is typically installed in cement plants for removing particulate dust from the exhaust. The dust collected by reverse air bag house (RABH) dust collectors in cement plants also has cementitious properties, and as with raw mill dust, can be utilized in various cement blends.
A cement mortar is a thick, malleable mixture like a dough consisting of cement, aggregate, admixtures and water, and can be classified into tile cement mortar, cement plaster, skim coat mortar, plain mortar, and the like depending on its use. All these products belong to the dry-mix mortar category for which there is no Indian standard available at this moment.
A skim coat refers to a cement-based finishing material, a thin layered mortar of thickness generally between 1 mm and 3 mm, laid either on a concrete substrate or a render (on inner and outer walls and the ceiling of a building) having thickness typically of around 15 mm, to obtain a smooth surface finish.
Dry mix skim coat compositions usually are composed of inorganic and organic polymeric binders, fillers and additives such as water retaining agents. Cement, (particularly white cement in India) is one of the most popular inorganic binders used in skim coats for interior and exterior applications, as compared to the other inorganic binders such as gypsum or lime. Gypsum based skim coats set quickly, usually within minutes, making the use of setting retarders necessary to make application feasible. Lime containing skim coat usually has a long pot life, sometimes lasting overnight.
After the application, the skim coat mortar may be cured and left as such or it may also be coated with paint as a finishing process. The surface finish (smoothness) of a skim coat is one of the important parameters which determines the actual paint consumption during application; smoother the surface (lower the porosity), lesser the consumption of paint.
Cellulose ethers such as methyl cellulose, hydroxyethylmethyl cellulose, hydroxypropylmethyl cellulose, hydroxyethyl cellulose, or ethylhydroxyethyl cellulose are used for water retention, rheology enhancement, reduction in water absorption rate and to achieve improved pot life (setting time) making skim coat user friendly.
Cellulose ethers are usually used in small qualities due to their high cost. If cellulose ether is used alone for skim coat mortar, an adhesive force with respect to a working surface is essentially improved by improvement in water retention property. Yet, there are differences in characteristics among various kinds of cellulose ether. In case of low-viscosity cellulose ether, cracks may occur on a surface because of workability and fast drying of the skim coat mortar. In case of high-viscosity cellulose ether, workability may be worsened due to a skinning phenomenon in which a thin film is formed on a surface of the skim coat mortar. To address such issues, attempts have been made to partially improve workability and pot time by adding various additives to cellulose ether.
Redispersible polymer powders (RDPs) are used for various construction applications viz. tile grout, tile cement, exterior insulating finishing systems (EIFS), water proofing, and self leveling floors. The purpose of using RDPs is to enhance bond strength, flexibility and abrasive resistance of dry mortars. These polymer powders are typically produced via spray drying of a variety of polymer emulsions (e.g. VAC/E, VAC/Veova, vinyl/acrylics, VAE/Acrylics, Acrylics, St/Ac etc.), protective colloids (e.g. polyvinyl alcohol) and anti caking agents (e.g. calcium carbonate, silica etc.).
US patent 4,239,546 A discloses all suitable types of waxes are modified with suitable polymers, in particular hydrocarbon polymers.
Korean patent application 200928065, discloses a polymer-modified mortar composition used for waterproof coating during construction which is based on ethylene vinyl acetate copolymer and/or styrene acrylic copolymer.
US patent application 20110257301A1 discloses settable gypsum composition comprising water; a first additive comprising a vinyl acetate/ethylene copolymer in latex or emulsion form; and a second additive which is at least one of (i) a wetting agent and/or a surfactant; (ii) a titanium coupling agent, (iii) a zirconium coupling agent, and (iv) mixtures thereof.
PCT publication WO2012073258A3 discloses a composition suitable for use in building construction comprising water, a thickener, a pH stabilizer, a preservative, a coalescing agent, a binder, bottom ash, silica particle mixture, stone grit, a filler, an extender, and an additive.
Ru Wang et al (Advanced Materials Research, Volume 687, Pages 100-106) discloses use of silanes and siloxanes as hydrophobic additives in cement and mortar compositions.
PCT publication WO1999028264A1 discloses metal stearates as hydrophobic additives in cement and mortar compositions.
Addition of certain hydrophobic agents may also reduce strength of the mortar (both dry and wet). Hence, an effective solution which provides a way to optimize the degree of water resistance or repellency is always a necessity and this can be achieved through a powder based approach.
Although cementitious compositions comprising cement kiln dust, fly ash and ground granulated blast furnace slag are well known in both patent and non-patent literature, there are no reports pertaining to skim coat compositions comprising reverse air bag house dust and raw mill dust. Consequently, for the productive disposal of such by-products of cement manufacturing, efforts are needed to explore their usage in skim coat compositions comprising ordinary Portland cement and other additives.
Skim coat compositions are also prone to cracking and chalking over a period of time. Hence, it is also an object of the present invention to afford a skim coat composition that resists cracking, chalking, and increases in strength over a period of time.
Further, it is observed that colored skim coats (generally prepared by using pigments which may be organic or inorganic) lose their colour tone over time on exposure to sunlight and varying weather conditions, thereby affecting the aesthetic appeal of the structure or surface on which it is applied. Hence, it is an object of the present invention to afford a skim coat composition that exhibits increased color fastness to sunlight and varying weather conditions. Further, the luster of the skim coat may be tuned by varying the proportion of ultrafine fillers in the skim coat composition.
Also, production of ultrafine fillers in high volumes on industrial scales would otherwise incur heavy grinding cost making the product commercially unviable. The current invention promotes the use of fillers which may include fly ash, GGBFS, RABH, silica fume and the likes either individually or in combination.
The inventors of the present invention have developed a skim coat composition comprising Fillers, Ordinary Portland cement, Organic polymeric binder, and Organic polymer, wherein, fillers are by-product of cement manufacturing to overcome problems mentioned above.
SUMMARY OF THE INVENTION
In accordance with an embodiment of the invention, there is provided a skim coat composition, comprising (a) Fillers; (b) Ordinary Portland cement; (c) Organic polymeric binder; (d) Organic polymer; Wherein, filler are by-product of cement manufacturing.

In accordance with an another embodiment of the invention, there is provided a skim coat composition comprising (a) Fillers present in range of 5%-80%; (b) Ordinary Portland cement present in range of 10%-40%; (c) Organic polymeric binder present in range of 1%-10%; (d) Organic polymers present in range of 0.1%-2%.
In accordance with an another embodiment of the invention, there is provided a skim coat composition comprising fillers wherein one or more filler are selected from group comprising silica fume, fly ash, GGBFS, reverse air bag house dust, raw mill dust, ground perlite, ground vermiculite.
In accordance with an another embodiment of the invention, there is provided skim coat composition comprising polymeric binders wherein one or more polymeric binders are selected from group comprising, Vinyl acetate-ethylene copolymers, terpolymers of Vinyl acetate, vinyl ester of Versatic acid (VeOVa), acrylic acid, Styrene-butadiene copolymers, VAM-Acrylics, Styrene-Acrylics and Acrylics.
In accordance with an another embodiment of the invention, there is provided a skim coat composition comprising Organic polymers wherein one or more Organic polymers are selected from group comprising, etherification of hydroxyl group of cellulose with methyl, hydroxyethyl, hydroxypropyl, and hydrophobes.
In accordance with an another embodiment of the invention, there is provided a skim coat composition optionally comprising additional ingredient wherein one or more additional ingredient are selected from group comprising Slag powder GGBFS or Calcined Clay, Ground perlite, fly ash and hydrated lime.
In accordance with an another embodiment of the invention, there is provided a process for preparation of high performance skim coat composition comprising steps of:
(a) Weighing the raw materials;
(b) Dry mixing the weighed raw materials in a high shear powder mixer to obtain the skim coat composition.

(c) Mixing time to achieve the homogeneous composition ranges between 5-30 minutes.
DETAILED DESCRIPTION OF THE INVENTION
It is to be noted that, as used in the specification and the appended claims, the singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to a composition containing “a compound” includes a mixture of two or more compounds. It should also be noted that the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.
The expression of various quantities in terms of “%” or “% w/w” means the percentage by weight, relative to the weight of the total solution or composition unless otherwise specified. The term “water” used herein refers to demineralized water unless otherwise specified.
In accordance with an embodiment of the invention, there is provided a skim coat composition, comprising (a) Fillers; (b) Ordinary Portland cement; (c) Organic polymeric binder; (d) Organic polymer; Wherein, filler is by-product of cement manufacturing.
The term “filler” used in reference are by products of cement industry which helps in controlling the final finish of the skim coat composition and is responsible for its unique natural color. The filler is obtained as a by-product of cement manufacturing.
The term “ordinary portland cement” used in reference is the most common type of cement in general use around the world as a basic ingredient of concrete, mortar, stucco, and non-specialty grout. It is a fine powder, produced by heating limestone and clay minerals in a kiln to form clinker, grinding the clinker, and adding 2 to 3 percent of gypsum.

The term “organic polymer binder”(Re-dispersible polymer powder, RDP) used in reference Polymeric binders in a skim coat formulation ensure its good adhesion with a wide range of substrates.

The term “organic polymer” (cellulose ether) used in reference Polymers for water retention ensures water retention for cement curing and workability of the skim coat paste.
In accordance with an another embodiment of the invention, there is provided a skim coat composition comprising (a) Fillers present in range of 5%-80%; (b) Ordinary Portland cement present in range of 10%-40%; (c) Organic polymeric binder present in range of 1%-10%; (d) Organic polymers present in range of 0.1%-2%.
In accordance with an another embodiment of the invention, there is provided a skim coat composition comprising fillers wherein one or more filler are selected from group comprising silica fume, fly ash, GGBFS, reverse air bag house dust, raw mill dust, ground perlite, ground vermiculite.
In accordance with an another embodiment of the invention, there is provided skim coat composition comprising polymeric binders wherein one or more polymeric binders are selected from group comprising, Vinyl acetate-ethylene copolymers, terpolymers of Vinyl acetate, vinyl ester of Versatic acid (VeOVa), acrylic acid, Styrene-butadiene copolymers, VAM-Acrylics, Styrene-Acrylics and Acrylics.

In accordance with an another embodiment of the invention, there is provided a skim coat composition comprising Organic polymers wherein one or more Organic polymers are selected from group comprising, etherification of hydroxyl group of cellulose with methyl, hydroxyethyl, hydroxypropyl, and hydrophobes.
Discussed below are some representative embodiments of the present invention. The invention in its broader aspects is not limited to the specific details pertaining to the embodiments and representative methods. The illustrative examples are described in this section in connection with the embodiments and methods provided. The invention according to its various aspects is particularly pointed out and distinctly claimed in the appended claims read in view of this specification and appropriate equivalents.

Following table provides the details of the mineralogy, percentages and fineness of various raw materials used in the composition of the invention.
Materials Constituents Mineralogy Range (percentage) Fineness (Blaine) Particle Size range (µm)
1 Fillers Raw Mill Calcium Hydroxide, Silica, Alumina, Magnesium Oxide, Calcite, Iron Oxides, Calcium Oxide, Calcium Iron Oxide, Calcium Hydroxide, Calcium Silicate, Aluminosilicates, Calcium-Aluminium Silicates, Wollastonite 0-50 300-500 0.3-32
Class F Fly Ash 0-30 200-250 0.5-45
Class C Fly Ash 0-30 200-250 0.5-45
GGBFS (Slag Powder) 0-30 300-400 0.3-21
Hydrated lime 0-3 600-1000 --
RABH dust 25-75 500-700 0.3-88
Silica Fume 0-20 15000-30000 0.01-0.5
Perlite Dust 0-30 300-500 0.3-174
Vermiculite Dust 0-30 300-500 0.3-174
2 Cement Ordinary Portland Cement Alite, Belite, Tricalcium Aluminate, Silica, Calcite, Gypsum 15-30 300-400 0.3-21
Portland Pozzolana Cement 15-30 300-400 0.3-21
Portland Slag Cement 15-30 300-400 0.3-21
3 Polymeric Binders Vinyl acetate-ethylene copolymers and terpolymers of Vinyl acetate, vinyl ester of Versatic acid (VeOVa) and acrylic acid, Styrene-butadiene copolymers, Various types of VAM-Acrylics, Styrene-Acrylics, Acrylics NA 1.0-10.0 NA NA
4 Water Retaining Polymers MHECs NA 0.1- 2.0 NA NA

The composition optionally comprises Slag powder (GGBFS)/Calcined Clay, Ground perlite, fly ash alone or combination thereof in an amount 10 to 75% and hydrated lime in an amount 1 to 15 %.
A filler helps in controlling the final finish of the skim coat composition and is responsible for its unique natural colour. The filler, obtained as a by-product of cement manufacturing, is selected from the group of materials consisting of silica fume, fly ash, GGBFS, reverse air bag house dust, raw mill dust, ground perlite, ground vermiculite and combinations thereof. More particularly, most of the compositions primarily contain fine dust in addition to other fillers. In its original form, these ultrafine fillers contain fine to ultrafine particulate materials which is primarily responsible for the unique properties of the skim coat mentioned in this present invention.
Polymeric binders in a skim coat formulation ensure its good adhesion with a wide range of substrates. Non-limiting examples of organic polymeric binders that may be useful in the present invention, include
1. Vinyl acetate-ethylene copolymers and terpolymers of Vinyl acetate, vinyl ester of Versatic acid (VeOVa) and acrylic acid,
2. Styrene-butadiene copolymers,
3. Various types of VAM-Acrylics, Styrene-Acrylics, Acrylics, and so forth, each of which can be used individually or in combinations thereof.
Polymers for water retention ensure water retention for cement curing and workability of the skim coat paste. Organic polymers useful for the present invention include but not limited to those prepared by etherification of hydroxyl group of cellulose with methyl, hydroxyethyl, hydroxypropyl, and hydrophobes. The degree of etherification of the aforestated organic polymers may also be varied to produce cellulose ether derivatives with a wide range in properties, such as viscosity, water retentivity, solubility, etc. Non-limiting examples of cellulose ethers having water retention and workability improving properties such as that may be useful in the present invention, include:
1. Methyl hydroxyethyl cellulose (MHEC)
2. Methyl hydroxypropyl cellulose (MHPC)
3. Hydroxyethyl cellulose (HEC)

Apart from these, the composition of the current invention may also contain cellulosic fibres and air entraining agents as physical property enhancers.
The skim coat composition of the present invention optionally comprises ingredients selected from the group consisting of hydrated lime, additional fillers, such as ground granulated blast furnace slag (GGBFS), calcined clay, ground perlite, any other pozzolans and additional organic modifiers.
In the present invention, a unique combinations of raw materials such as ultrafine-fillers, raw mill, fly ash and GGBFS in the various formulations (mentioned in the Test Examples 1-8) are key differentiating factor. These provide a combination of reactive (Pozzolanic) and non-reactive fillers having high surface area (fineness). The chemical composition (mentioned earlier) of these raw materials along with the higher surface area is responsible for enhanced pozzolanic activity which results in efficient binding of fillers with superior physical and chemical properties of the final product (DalmiaMagic Skim Coat, known as DMSC).
Following are some of the advantages.
Higher surface area of the Skim coat (due to fineness individual raw materials) helps achieving higher coverage area on wall with excellent workability, very smooth surface finish and high compressive strength compared to currently available skim coats in the market.

Improved chemical reaction results in additional CSH phases (reactive calcium silicates from pozzolanic raw materials) which results into a dense interwoven structure within the matrix enhancing the compressive strength. The improved bridging between the matrix and substrate at matrix-substrate interface improves the binding of skim coat with substrates. Eventually, the resulting microstructure provides very good resistance to chalking and seepage. The synergy between the polymeric and hydraulic binders leads to very good tensile adhesion on wide range of substrates, hence making it most suitable for external applications.

This composition has natural colour tones due to its unique mineralogy and hence produces persistent shades/colours without any form of deterioration with time when left unpainted especially in exterior applications.

In accordance with an embodiment of the present invention, there is provided a process for preparing the skim coat composition, said process comprising the steps of;
(a) Weighing the raw materials based on the required specification; and
(b) Dry mixing the weighed raw materials in a high shear powder mixer to obtain the skim coat composition of the present invention.
(c) The typical mixing time to achieve the homogeneous mixing varies between 5-30 minutes. However, the mixing time could be significantly different depending on the quantity of materials, and type of the mixture, fineness of the materials etc.
The present invention is more particularly described in the following non-limiting examples that are intended as illustrations only, since numerous modifications and variations within the scope of the present invention will be apparent to a skilled artisan. Unless otherwise noted, all parts, percentages, and ratios reported in the following examples are on a weight basis, and all reagents used in the examples were obtained or made available from the chemical suppliers.
EXAMPLES
Examples of the preferred formulations of the skim coat of the current invention are tabulated below.
Example 1
Ingredients %
OPC 25
Raw Mill 0
RABH 73.25
Hydrated Lime 0
Polymer for Binding or Redispersible polymers 1.35
Polymers for water retention (cellulose ether) 0.4

Example 2
Ingredients %
OPC 20
Raw Mill 44.25
RABH 34
Hydrated Lime 0
Polymer for Binding or Redispersible polymers 1.35
Polymers for water retention (cellulose ether) 0.4

Example 3
Ingredients %
OPC 22
Raw Mill 0
RABH 73.4
Hydrated Lime 3
Polymer for Binding or Redispersible polymers 1.2
Polymers for water retention(cellulose ether) 0.4

Example 4
Ingredients %
OPC 23.15
Raw Mill 47.5
RABH 26
Hydrated Lime 3
Polymer for Binding or Redispersible polymers 1
Polymers for water retention (cellulose ether) 0.35

Example 5
Ingredients %
OPC 29.65
Raw Mill 0
RABH 65
Hydrated Lime 0
Polymer for Binding or Redispersible polymers 4.25
Polymers for water retention(cellulose ether) 1.1

Example 6
Ingredients %
OPC 27.35
Raw Mill 23.5
RABH 43.15
Hydrated Lime 0
Polymer for Binding or Redispersible polymers 5.1
Polymers for water retention(cellulose ether) 0.9

Example 7
Ingredients %
OPC 22.35
Raw Mill 12.25
RABH 62
Hydrated Lime 1.2
Polymer for Binding or Redispersible polymers 1.7
Polymers for water retention(cellulose ether) 0.5

Example 8
Ingredients %
OPC 26.6
Raw Mill 46
RABH 16.4
Hydrated Lime 2.5
Polymer for Binding or Redispersible polymers 7.2
Polymers for water retention(cellulose ether) 1.3

Example 9
Typical properties and specifications of the current invention are tabulated below.
Property Unit Test Methods/standards followed
Compressive strength (28 days) 8.4 N/mm2 BS EN 1015-11:1999
Initial setting time 245 minutes BS EN 196: Part 3:1995 +A1: 2008, Annex A
Final setting time 315 minutes BS EN 196: Part 3:1995 +A1: 2008, Annex A
Tensile adhesion strength 0.9 N/mm2 BS EN 1015-12: 2000

Water retention 99.9% BS 4551: 2005+A2:2013
Linear Shrinkage at 28 days 0.07% ASTM C531:2000 (Reapproved 2012)
Example 10
The current invention (DMSC in the table below) as exemplified in example 1 has been compared with a regular skim coat/wall putty product (Control) available in the market. This is a comparative study without following any prescribed standard. The values mentioned in the table below may not be considered as absolute. The values show the superiority in terms of compressive strength with similar weight at the end of 28 days. The results are given in the following Table.
Compressive Strength (comparative study)

Sample Compressive Strength (MPa)
3 Days 7 Days 28 Days
(MPa) Wt.(gm) (MPa) Wt.(gm) (MPa) Wt.(gm)
DMSC 3.10 177.9 3.12 173.0 3.2 151.80
Control 1.59 164.3 1.62 161.0 1.6 151.30

While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is thereof intended to cover in the appended claims such changes and modifications that are within the scope of the invention.
,CLAIMS:We claim:
1. A skim coat composition, comprising
(a) Fillers;
(b) Ordinary Portland cement;
(c) Organic polymeric binder; and
(d) Organic polymer;
Wherein, fillers are by-product of cement manufacturing.
2. The skim coat composition as claimed in claim 1, comprises
(a) Fillers present in range of 5%-80%;
(b) Ordinary Portland cement present in range of 10%-40%;
(c) Organic polymeric binder present in range of 1%-10%;
(d) Organic polymers present in range of 0.1%-2%.
3. The skim coat composition as claimed in claim 1, wherein one or more filler are selected from group comprising silica fume, fly ash, GGBFS, reverse air bag house dust, raw mill dust, ground perlite, ground vermiculite.
4. The skim coat composition as claimed in claim 1, wherein one or more Polymeric binders are selected from group comprising, Vinyl acetate-ethylene copolymers, terpolymers of Vinyl acetate, vinyl ester of Versatic acid (VeOVa), acrylic acid, Styrene-butadiene copolymers, VAM-Acrylics, Styrene-Acrylics and Acrylics.
5. The skim coat composition as claimed in claim 1, wherein one or more Organic polymers are selected from group comprising, etherification of hydroxyl group of cellulose with methyl, hydroxyethyl, hydroxypropyl, and hydrophobes.
6. The skim coat composition as claimed in claim 1, wherein one or more additional ingredient are selected from group comprising Slag powder GGBFS or Calcined Clay, Ground perlite, fly ash and hydrated lime.
7. A process for preparation of skim coat composition; comprising steps of:
- Weighing the raw materials;
- Dry mixing the weighed raw materials in a high shear powder mixer to obtain the skim coat composition.
- Mixing time to achieve the homogeneous composition ranges between 5-30 minutes.