USING INDUSTRIAL WASTES

FIELD OF THE INVENTION

The present invention relates to the field of building materials and more particularly to a ready-mix plaster material prepared using industrial wastes. The ready- mix plaster material of the present invention can be used as mortar for brick jointing and wall plaster by just adding water to the ready-mix powdered plaster material. The industrial wastes used for preparing ready-mix plaster material are red mud, fly ash and bottom ash which allow replacing high amounts of natural sand material used in conventional building materials.

BACKGROUND OF THE INVENTION

Concrete and plaster are the most commonly used materials in infrastructure development throughout the world. They are globally accepted construction material in all types of Civil Engineering structures. Plaster is a building material and generally used for the jointing of bricks in making wall and protective cover on walls and ceiling.

Generally plaster is manufactured as a dry powder and mixed with water to form a workable paste just before it is applied to the surface. Plaster is not a strong material and it is not bearing any load of structure on which it is applied.

There are many type of plaster available in practice such as gypsum plaster, lime plaster, cements plaster etc. All of these plasters more or less serve the same purpose.

Most common plaster used in construction is a mixture of cement and sand mixed in a certain ratio.

Conventional cement and sand plaster is nothing but a mixture of natural sand, Portland cement and water in certain ratio used for construction purposes. Natural sand is a prime material used for the preparation of plaster and also plays an important role in constructions. However, the availability of natural sand is very limited and procurement of the same is becoming difficult due to scarcity of the same and environmental issues as well. Nowadays river erosion and other environmental issues have led to the scarcity of natural sand. The reduction in the sources of natural sand and the requirement for reduction in the cost of concrete production has resulted in the increased need to find new alternative materials to replace natural sand so that excess river erosion is prevented and high strength concrete is obtained at lower cost. Partial or full replacement of natural sand by the other alternative materials like quarry dust, foundry sand and others are being researched from past two decades, in view of conserving the ecological balance.

The availability of suitable natural sand for concrete production near the point of consumption has been exhausted around many populated regions in the world. Moreover, numerous field observations show that destruction of landscape, reduction of farm and grazing land, collapsing river banks, deforestation and water pollution are the environmental effects that result due to sand and gravel mining. This has led to a search for a new replacement materials for the natural sand. With the rapid development of the construction industry, building materials which are of good stability and environmental quality are in great demand.

European Patent Application number EP 2105420A1 discloses a composition for building material comprising more than 70% of fly ash and bottom ash in combination, a chemical activator and 2-18% of additive material. EP 2105420A1 is based on chemical route/activator using hydroxide, sulphate, acetate or chloride salt. The chemical activator reacts with fly ash and forms binding matrix suitable for the production cold setting fly ash building construction materials like bricks, block concrete and other high strength construction materials but not plaster material. Said chemical activator must contain at least two anions, especially at least three anions such as chloride, hydroxyl and sulfate ions or hydroxyl, sulfate and acetate ions. The nature and dosages of activator play a crucial role in setting and hardening process of plaster.

Chinese Patent Application number CN103693924A discloses a mixed Bayer red mud plastering mortar dry mix using ordinary portland cement (19-13%), Bayer red mud (2-6%), fly ash (2-6%), cellulose ethers (0.05-0.15%), latex powder (0.19-0.54%), modified attapulgite (0.57-1.22%) and river sand (approximately 73%) composition. However, CN 103693924A requires 73.65-74.42% of natural sand for preparation of the plaster. Therefore, CN 103693924A uses a very high amount of river sand which is not desirable to overcome the environmental effects due to use of natural sand resources.

OBJECTIVES OF THE INVENTION

It is an object of the present invention to manufacture a ready-mix plaster material for various construction purposes.

It is another object of the present invention to manufacture a ready-mix plaster material utilizing the industrial wastes such as red-mud, fly-ash and bottom ash.

It is other object of the present invention to manufacture a ready-mix plaster that uses materials which allows reduction in use of natural sand plaster.

SUMMARY OF THE INVENTION

The present invention relates to a ready-mix plaster material prepared by using industrial wastes such as red mud, fly ash and bottom ash thereby replacing a major portion of natural sand and cement used in a conventional plaster.

In accordance with an aspect of the disclosure there is provided a ready-mix plaster material comprising ingredients:

a) red mud in the range of 5-12 w/w%;

b) fly ash in the range of 20-30 w/w% ;

c) bottom ash in the range of 25-45 w/w%;

d) portland cement in the range of 11-17 w/w%; and

e) natural sand in the range of 12-18 w/w%; and

an additive in the range of 0.05-0.2 wt% of total weight of ingredients (a) to (e).

Another aspect of the present invention provides a process for preparing ready- mix plaster material comprising mixing red mud in the range of 5-12 w/w%; fly ash in the range of 20-30 w/w% ; bottom ash in the range of 25-45 w/w%; portland cement in the range of 11-17 w/w%; and natural sand in the range of 12-18 w/w% in a plough shear mixer to obtain a premix; and adding an additive in the range of 0.05-0.2 wt% of the premix in the plough shear mixer to obtain the ready-mix plaster material. The mixing may be carried out for at least 5 minutes to obtain a homogenous dry mixture of ready-mix plaster material.

These and other features and advantages of the present subject matter will become better understood with reference to the following description. This summary is provided to introduce a selection of concepts in a simplified form. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

DESCRIPTION OF THE INVENTION

The present invention relates to a ready-mix plaster material prepared by using industrial wastes such as red mud, fly ash and bottom ash in place of natural sand.

Accordingly, the present invention provides a ready-mix plaster material comprising: comprising ingredients:

a) red mud in the range of 5-12 w/w%;

b) fly ash in the range of 20-30 w/w% ;

c) bottom ash in the range of 25-45 w/w%;

d) portland cement in the range of 11-17 w/w%; and

e) natural sand in the range of 12-18 w/w%; and

an additive in the range of 0.05-0.2 wt% of total weight of ingredients (a) to (e).

The ready-mix plaster material of present application is a homogeneous composition of well graded mix of red mud, fly ash, bottom ash, natural sand, portland cement and some part of additive. The mixture is prepared in powdered form. It is ready to use by mixing desired quantity of water in the powdered ready-mix plaster material.

Red mud is a waste -product generated in process of extraction of alumina from Bauxite ore using Bayer's process. It is approx 45 to 55% of Bauxite used for alumina extraction. Tonnes of red mud is generated annually and is difficult to dispose off or recycle satisfactorily. However, worldwide studies are going on for its fruitful use. The conventional method of disposal of red mud in ponds has often adverse environmental impacts. For example, in monsoons, the waste red mud may be carried to the surface water courses and as a result leaching may cause contamination of ground water if not disposed in environmentally proven manner. Further, the disposal of large quantities of red mud poses increasing problems of storage occupying a lot of space. After drying and sieving the red mud (collected from pond) up to desired particle size (95% particles smaller than or equal to 600 microns and 84% particles smaller than or equal to 300 microns), it is ready to use in ready-mix plaster material of present application. In an embodiment of the present invention, red mud is used in the range of 5-12% w/w.

Fly ash is very fine material generated in thermal power plant in process of burning coal in boilers to produce thermal energy. The total ash generation is normally 35% of total coal fed in boilers. The fly ash generation is approx 80% of total ash generation. Normally it is collected through electrostatic precipitators. This fly ash has very fine particle size and is directly mixed in ready-mix plaster. The preferable size of fly ash has 97% particles smaller than or equal to 150 microns and 80% particles smaller than or equal to 75 microns. The common environmental pollution problems created by disposal of fly ash, besides air and water pollution are wastage of large tracts of land which otherwise could be utilized for useful purposes. In an embodiment of the present invention, fly ash is used in the range of 20-30 %w/w.

Bottom ash is also a by-product of coal burning in boilers of thermal plant. It is part of the non-combustible residue of combustion in furnace and is coarser in nature. Bottom ash generation is 20% of total ash generation in thermal power plant and is usually disposed along with fly ash. Fly ash being a major proportion of ash generated in coal fired thermal power plant, has been used recently in portland pozzolona cement manufacturing, road building and agriculture, land and mine filling etc. However, there are not many studies using bottom ash component separately especially for providing construction materials. The inventors of the present invention have used bottom ash in higher amounts to replace a major portion of natural sand. The bottom ash was used after drying and sieving with suitable mesh up to desired particle size (93% particles smaller than or equal to 600 microns and 83% particles smaller than or equal to 300 microns). In an embodiment of the present invention, bottom ash is used in the range of 25-45 %w/w.

Natural sand is found in river bed. The dried sand is cleaned with sieve size of 1.50 mm for any foreign materials known in the art, again sieved with suitable mesh size up to required particle size corresponding to grading Zone IV (as per IS: 383-1970), and then it is ready to use in ready-mix plaster. It is required to improve the workability of material. In an embodiment of the present invention, natural sand is used in the range of 12-18 %w/w. The natural sand as per grading Zone IV has particle size distribution as shown in Table 1.

Table 1: Particle size distribution of natural sand as per grading Zone IV of IS: 383- 1970

Very small quantity of additive is mixed directly as it is a ready-made product available in market. It strengthens the consistency of materials which are based on hydraulic binders. It also influences the rheology behaviour of the binder matrix in water, changing the yield point, flow parameters and water retention. The additive can be selected from the group consisting of starch ether powder, cellulose ether etc. In an embodiment of the present invention, additive is over and above a total mix of red mud, fly ash, bottom ash, portland cement and natural sand.

Portland cement is a standard material available in market. It is a binding material commonly used in building construction industries. It is directly added in ready-mix plaster of the present invention as a binding material. In an embodiment of the present invention, Portland cement is used in the range of 11-17 %w/w.

In another embodiment, the present invention provides a process for preparation of ready-mix plaster material comprising mixing red mud in the range of 5-12 w/w%; fly ash in the range of 20-30 w/w% ; bottom ash in the range of 25-45 w/w%; portland cement in the range of 11-17 w/w%; and natural sand in the range of 12-18 w/w% in a plough shear mixer to obtain a premix; and adding an additive in the range of 0.05-0.2 wt% of the premix in the plough shear mixer to obtain the ready-mix plaster material. The additive is added over and above the total amount of red mud, fly ash, bottom ash, portland cement and natural sand. The mixing the plough shear mixer may be carried out for at least 5 minutes to obtain a homogenous dry mixture of ready-mix plaster material.

Yet another embodiment of the present invention provides a process in which red mud, bottom ash and natural sand have moisture level in the range of 0.01% to 2%.

In still another embodiment, the present invention provides a ready-mix plaster material in powdered form which can be instantaneously used as a construction material by mixing with desired quantity of water.

EXAMPLES

The present invention is more particularly described in the following examples, that are intended as illustrations only, since numerous modifications and variations within the scope of the present invention will be apparent to those skilled in the art. 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 are available from the chemical suppliers. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are intended to provide further explanation of the subject matter.

EXAMPLE 1: Preparation of Ready-mix Plaster

Red mud collected from alumina refinery, bottom ash collected from thermal power plant, and natural sand having close to zero moisture level (about 0.01%) were sieved individually with a mesh size as per sieve designation in IS: 383-1970 to obtain a desired particle size: red mud having 95% particles smaller than or equal to 600 microns and 84% particles smaller than or equal to 300 microns; bottom ash having 93% particles smaller than or equal to 600 microns and 83% particles smaller than or equal to 300 microns; natural sand having particle size as per grading Zone IV of IS: 383- 1970 code. The red-mud, bottom ash and natural sand, thus obtained, were mixed together in a plough shear mixer. Fly-ash, collected from thermal power plant having fine particle size (97% particles smaller than or equal to 150 microns and 80% particles smaller than or equal to 75 microns) and ordinary portland cement were then added to the mixer. The additive starch ether powder was added to the mixture over and above the total mixture of ingredients, as above and the ingredients were mixed together in the plough shear mixer at least for a period 3 to 5 minute to obtain the homogenous ready- mix plaster material. The amounts of all the ingredients used are shown in Table 2.

The ready-mix plaster material obtained in the powder form was then packed using an air tight bag as a ready-to-use-plaster material. The powdered mixture can be used as mortar, when required, by mixing desired quantity of water, for brick jointing and wall plaster. The ready-to-use-plaster material was tested in accordance with the Indian Standard code IS: 2250: 1981 and other ASTM international code.

Table 2: Components used for preparation of ready-mix plaster

Indian Standard code IS: 2250: 1981 and ASTM international code tests used are as following. Drying Shrinkage (Test method ASTM C 596 - 01):

Sample was prepared by adding water in dry mortar. The water was added in the dry sample as per Manufacturer's Specification as follows: Water-Powder (W/p) ratio - 0.17; Specimen size: 25 x 25 x 250 mm; Curing condition: Normal water bath curing. Three specimens of each sample were tested for Drying Shrinkage.

Pull Off Strength Test for Adhesion (Test method ASTM D 4541): Samples were prepared by applying ready-mix Plaster in between 2 AAC blocks & air cured for 28 days; Specimen size: 50 x 50 mm; Curing condition Air Curing; Equipment used - Pull Off Tester. Three specimens of each sample were tested for Pull Off Strength Test. Pull off test is used to measure the adhesion strength between coating and a substrate. In our case coating is plaster material.

Compressive Strength and Flow Test: Sample was prepared by adding water in received dry mortar. The water was added in the dry sample for water quantity. W/p ratio - 0.17; Specimen size: 70.6 x 70.6 x 70.6 mm; Curing condition: Normal water bath curing. Flow test is used to determine the consistency of mortar i.e. ease of workability.

The test results obtained for the compositions 1, 2, and 3 are as shown below in Table 3.

Table 3: Results of tests for the ready-mix plaster composition of the present application

As shown in Table 3, the present invention provides a plaster material having good fluidity, water retention, low shrinkage, good adhesion strength as well as good compressive strength. As per the test results, the ready-mix plaster of the present invention falls in Grade MM3 to MM7.5 mortar mix as per IS 2250: 1981. The present invention thus provides a ready-mix plaster material which allows minimum wastage of construction materials used conventionally, using the industrial wastes as well as replacing a large amount of natural sand. Such a plaster material not only provides a solution for industrial waste management but also provides overall economic benefit by reducing cost of raw materials as compared to conventionally used plaster material and also protects ecosystem by conserving natural resources.

EXAMPLE 2 : Comparative Process for preparation of Ready-mix Plaster Material

Different variations of the compositions 1 , 2 and 3 obtained in Example 1 were prepared to assess the effect of various components used in the compositions. Variant compositions A to D were prepared by removing red mud, fly ash, bottom ash and natural sand, respectively, from each of the composition 1, 2 and 3 as obtained in Example 1. The variant compositions were prepared in accordance with the Table 4-6 as below showing number of units or parts of each component used to obtain the respective variant compositions.

Table 4: Components along with number of units or parts of each component used for preparation of variations of Composition 1 of ready-mix plaster material

Table 5: Components along with number of units or parts of each component used for preparation of variations of Composition 2 of ready-mix plaster material

Table 6: Components along with number of units or parts of each component used for preparation of variations of Composition 3 of ready-mix plaster material

Each of the composition prepared according to Table 4-6 was tested in accordance with the Indian Standard code IS: 2250: 1981 for compressive strength. The results of the same are shown in Table 7.

Table 7: Results of Compressive Strength (28 days) (N/mm2) for the variants of the compositions 1-3.

As shown in the Table 7, the ready- mix plaster material having desired properties for building materials is obtained when all the ingredients are present together in the powdered mixture. Even if one component is removed from the ready-mix plaster of the 5 present invention, the compressive strength decreases drastically. Thus, it is proved that when all the components of the composition of the present invention are mixed for obtaining the desired ready-mix-plaster material they interact to produce a synergistic effect. 0 EXAMPLE 3 : Comparison of test results for ready-mix plaster and the prior art

The test results obtained for ready-mix plaster of the present application were also compared with the plaster mortar disclosed in the document CN 103693924A. The comparative data is provided in table 8 below.

As shown in Table 8, the plaster material of present invention shows 5 comparative properties with respect to the plaster material of CN 103693924A having higher amounts of natural sand (73.65 -74.42%). The present invention uses only 10-18 % of natural sand and still provides the mortar/ plaster which falls in Grade MM3 to MM7.5 mortar mix as per IS: 2250: 1981. 0

Table 8: Comparative properties of the plaster material of CN 103693924A with the plaster material of the present invention

Further, CN 103693924A does not use bottom ash as a separate component. It only uses fly ash, that too in small amounts of 2.86-5.45 %. The present invention on the other hand uses fly ash in the range of 20-30 w/w% and bottom ash in the range of 25-45 w/w%; and provides comparable properties of plaster material, thus allowing replacing about 82 to 88 % of natural sand from the plaster material. This allows conservation of the natural resources and protects the ecosystem for production of plaster material. Thus, the plaster material of present invention is eco- friendly and also has economic significance as it uses waste materials.

ADVANTAGES OF THE INVENTION

The present invention provides a plaster material which can be readily and easily used by just adding desired quantity of water when required for construction purposes. This allows less wastage of resources compared to traditional cement-sand plaster. The ready-mix plaster of present application is obtained using a large percentage of industrial waste materials and very less percentage of natural sand, thereby allowing conservation of the natural resources i.e. natural sand, which is depleting very fast due to unmanaged utilization, resulting in disturbance of ecosystem. Therefore, the present invention allows effective utilization and recycling of industrial waste, which otherwise pose a risk to environment due to disposal of such industrial waste materials in water or as landfills. The ready-mix plaster of present application is produced in powdered form to be readily used for construction purposes and can also be used in making bricks, blocks, tiles, sheets, etc. using compaction and casting known in the art to produce other such construction materials of interest.

Although the subject matter has been described in considerable detail with reference to certain preferred embodiments thereof, other embodiments are possible. As such, scope of the disclosure should not be limited to the description of the preferred embodiment contained therein.