Description:FIELD OF INVENTION
[001] The present invention relates to a method for preparing supplementary cementitious material from industrial waste. Particularly, the present invention relates to a method for preparing supplementary cementitious material by using waste quarry dust with reduced energy consumption and minimal environmental impact.

BACKGROUND OF THE INVENTION
[002] Cement, especially Portland cement, abbreviated OPC (ordinary portland cement) is an important construction material worldwide and the construction industry depends completely upon it. However, its’ production consumes huge amounts of energy and wide variety of mineral raw materials. To produce 1 ton of Ordinary Portland Cement an equal amount of carbon-dioxide is released into the atmosphere which is harmful to the environment. Cement production not only leads to huge carbon dioxide emissions both during its production and by power plants that generate power to run the production process. Global carbon dioxide emissions from cement industry account for 8%. The use of supplementary cementitious materials (SCM) such as Ground granulated blast-furnace slag (GGBFS) and fly ash along with Portland cement has been encouraged worldwide to reduce the emissions related to concrete. However these SCMs have some drawback like high cost and limited availability of the same in good quality. Hence there is a need to find an alternative SCM that is available throughout the country and is economical.
[003] Materials commonly used in the cement industry to constitute materials that can replace a portion of Portland cement in concrete, blended cements or other cementitious materials. Examples of conventionally used SCMs include GGBFS, Class C fly ash, Steel slag, silica fume, Class F fly ash and metastable forms of CaCO, ground limestone, ground quartz, and precipitated CaCO.
[004] Major concerns associated with such wastes is blockage of large pieces of land in their landfilling and contamination of land and water resources due to leaching of toxic contaminants. Waste quarry dust (WQD) are residues, tailings or waste material, left after the extraction and processing of rocks at crushing plant at a quarry. In general these wastes amount to about 2-5% of the aggregates and produced billions of tons annually. Thus, converting waste quarry dust into SCMs will help in reducing both landfilling space as well as carbon emission linked with production of concrete.
[005] In general these quarry dusts are alumino silicates. When they are mixed with concrete, have a very low reactivity and their inclusion in concrete without any modification causing severe drying shrinkage and increased water demand. This adversely affects the physical and mechanical properties of the concrete. Thus it’s essential to modify these wastes physically and chemically by adding certain activator chemicals depending upon its’ characteristics making it fit to be used in the construction activities. Further, the selection of chemicals to activate these wastes depends upon the mineralogy and chemical composition of the same.
[006] Also, wet carbonation of concrete causes embedded steel reinforcements to corrode, with the resulting expansion cracking and weakening the concrete. It starts as soon as concrete is exposed to the atmosphere, and can advance at a rate of 1mm to 5mm per year, depending upon the concrete’s porosity and permeability. Further, wet carbonation is the most common cause of reinforcement corrosion in above ground structures but can be prevented by avoiding the same. Thus, the present invention which provides a method of preparing SCM without the need of any wet carbonation step could be crucial in overcoming this problem.
[007] There are several patent applications disclosing the methods of preparing supplementary cementitious materials. One such patent document WO2023186344 discloses a method for producing a supplementary cementitious material from concrete waste and similar materials, supplementary cementitious material for making hydraulic building materials and alkali activated binders. However, the activators used in this cited document belong to alkali metal silicate and all the processes are carried out at high temperature and hence involves a very high energy intensive process.
[008] Another prior art WO2022074518A1 discloses a method of producing a supplementary cementitious material, from quarry sludge, aggregate washing sludge and road cleaning sludge comprising the steps of: - providing at least one waste material selected from the group - removing excess water from said waste material to provide a dry waste material, - mixing the dry waste material with a source of calcium sulphate to obtain a raw material mixture, - calcining the raw material mixture at a temperature of 700-900°C to obtain the supplementary cementitious material.
[009] Therefore, the above-mentioned methods have some serious shortcomings such as complicated synthesis procedures, use of large amount of chemicals and high temperature which increases both energy consumption and CO2 emission. Thus, there exists a need to overcome the above challenges and to develop a cost-effective and energy efficient process of producing supplementary cementitious materials.

OBJECTIVE OF THE INVENTION
[0010] The primary objective of the present invention is to provide a method for preparing supplementary cementitious material from industrial waste.
[0011] Another objective of the present invention is to provide is to provide a cost-effective and energy efficient method for preparation supplementary cementitious material with minimal environmental impact.
[0012] Yet another objective of the present invention is to provide a method for preparation of supplementary cementitious materials by minimizing the use of chemicals.
[0013] Other objectives and advantages of the present invention will become apparent from the following description taken in connection with the accompanying drawings, wherein, by way of illustration and example, the aspects of the present invention are disclosed.

SUMMARY OF THE INVENTION
[0014] The present invention provides a method for preparing supplementary cementitious material. The method involves grinding industrial waste with chemical activators at room temperature thereafter sieving the mixture through a sieve, to obtain supplementary cementitious material (SCM). The SCM of the present invention may be blended with cement to reduce the carbon emissions and to increase the strength and durability of the concrete.

BRIEF DESCRIPTION OF DRAWINGS

[0015] The present invention will be better understood after reading the following detailed description of the presently preferred aspects thereof with reference to the appended drawings, in which the features, other aspects and advantages of certain exemplary embodiments of the invention will be more apparent from the accompanying drawing in which:

[0016] Figure 1 illustrates a flowchart for preparing supplementary cementitious material from industrial waste.

DETAILED DESCRIPTION OF EMBODIMENTS
[0017] The following detailed description and embodiments set forth herein below are merely exemplary out of the wide variety and arrangement of instructions, which can be employed with the present invention. The present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. All the features disclosed in this specification may be replaced by similar other or alternative features performing similar or same or equivalent purposes. Thus, unless expressly stated otherwise, they all are within the scope of the present invention.

[0018] Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope of the invention. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness.

[0019] The terms and words used in the following description and claims are not limited to the bibliographical meanings but are merely used to enable a clear and consistent understanding of the invention. Accordingly, it should be apparent to those skilled in the art that the following description of exemplary embodiments of the present invention are provided for illustration purpose only and not for the purpose of limiting the invention.

[0020] It is to be understood that the singular forms “a”, “an” and “the” include plural referents unless the context clearly dictates otherwise.

[0021] It should be emphasized that the term “comprises/comprising” when used in this specification is taken to specify the presence of stated features, integers, steps, or components but does not preclude the presence or addition of one or more other features, integers, steps, components, or groups thereof.

[0022] Accordingly, the present invention relates to a method for preparing supplementary cementitious material from industrial waste. Particularly, the present invention relates to a method for preparing supplementary cementitious material by using waste quarry dust with reduced energy consumption and minimal environmental impact.

[0023] In an embodiment, the method for preparing supplementary cementitious material comprises of the following steps:
(a) grinding industrial waste with chemical activators at room temperature until a homogenous mixture is obtained; and
(b) sieving the mixture obtained in step (a) through a sieve, to obtain supplementary cementitious material (SCM).

In an exemplary embodiment, the grinding at step (a) may be performed for a time duration ranging between 5 minutes to 2 hours, depending on the amount of industrial waste. In another exemplary embodiment, the grinding is performed in the present invention for approximately 90 minutes at room temperature.
[0024] In an exemplary embodiment, the industrial waste may be selected from a group consisting of, such as, but not limited to, quarry dust. In another exemplary embodiment, the amount of industrial waste used in the present invention may be in the range of 70-99.8% by total weight of SCM.

[0025] In an exemplary embodiment, the quarry dust comprises aluminum oxide, silicon dioxide, iron oxide, calcium oxide, sodium oxide, and potassium oxide. In another exemplary embodiment, the amount of each component of quarry dust may vary as shown in Table 1.

Ingredient Percentage Range
Aluminum oxide 8-20%
Silicon dioxide 45-70%
Iron oxide, 0.5 -5%
Calcium oxide 0.1 -10%
Sodium oxide 0.1 to 5 %
Potassium oxide 0.1 to 5%

[0026] In another exemplary embodiment, the grinding may be performed using a grinder selected from a group consisting of, such as, but not limited to, a ball mill, etc.

[0027] In another exemplary embodiment, the sieve may be selected from a group consisting of, such as, but not limited to, a 45-micron sieve.

The chemical activators chemically activate the breaking of polymeric bonds during grinding and react with alumina, Iron oxide, and silica present in the industrial waste such as, but not limited to, quarry dust. Due to the use of chemical activators, the process of grinding can be performed at room temperature, eliminating the need for high temperatures. In an exemplary embodiment, the chemical activators may be selected from groups consisting of such as, but not limited to, alkali metal sulfate, alkali metal phosphate, alkali metal carbonate, alkali metal oxide/hydroxide, alkali salts of polyacrylic acid, hydrocarboxylic acid, and alkanolamine, or a combination thereof. In another exemplary embodiment, the alkali metal oxides/hydroxides may be selected from a group consisting of such as, but not limited to calcium hydroxide, magnesium hydroxide, lithium hydroxide, barium hydroxide, or a combination thereof. In another exemplary embodiment, alkali salts of polyacrylic acid may be selected from a group consisting of, such as, but not limited to sodium polyacrylate, or a combination thereof. In yet another exemplary embodiment, alkanolamine may be selected from a group consisting of, such as, but not limited to Triethanolamine, Triisopropanolamine, or a combination thereof. In yet another exemplary embodiment, the alkali metal sulfate may be selected from a group consisting of, such as, but not limited to sodium sulfate, calcium sulfate, magnesium sulfate, or a combination thereof. In yet another exemplary embodiment, the hydrocarboxylic acid may be selected from a group consisting of, such as, but not limited to citric acid, humic acid, tartaric acid, or a combination thereof. In yet another exemplary embodiment, the alkali metal carbonate may be selected from a group consisting of, such as, but not limited to sodium carbonate, calcium carbonate, lithium carbonate, Potassium carbonate, or a combination thereof. In yet another exemplary embodiment, the alkali metal phosphate may be selected from a group consisting of such as, but not limited to sodium hexametaphosphate, tripotassium phosphate, sodium tripolyphosphate, or a combination thereof. In another embodiment, the chemical activators may be present in a range of 0.2% to 30% by the total weight of the SCM. In another exemplary embodiment, different activators may be present in different amounts such as alkali metal oxide and hydroxide may be present in a range of 0.1% to 1% by total weight of the activators, alkali metal sulfates may be present in range of 0.1% to 10%; alkali metal phosphate may be present in a range of 0.1% to 5% by total weight of chemical activators; alkali metal carbonate may be present in a range of 0.1% to 15% by total weight of the activators; alkali salts of poly acrylic acids may be present in range of 0.1% to 3% by total weight of the activators; alkali metal phosphate may be present in range of 0.1 to 5% by total weight of the activators; and alkanolamine may be present in range of 0.01% to 1% by total weight of the activators.
[0028] In a preferred embodiment, grinding may be performed efficiently and in less time at room temperature even with the use of less amount of chemical activators. For example, 0.01-1% of alkanolamine forms multiple coordination bonds with the metal present in the quarry dust such as alumina, thereby leading to the sequestration of metal and thus aiding in the process of grinding.

[0029] In another embodiment, alkali metal sulfate such as sodium sulfate possesses a pH in a range of 6 to 11 at 10% dilution, and calcium sulfate, magnesium sulfate, and alkali metal phosphate possess pH values greater than 9.

In a preferred embodiment, the supplementary cementitious material obtained in the present invention may be blended with cement to reduce carbon emissions and increase the strength and durability of the concrete. In another exemplary embodiment, the cement used in the present invention may be selected from a group consisting of, such as, but not limited to, ordinary Portland cement. In yet another exemplary embodiment, concrete may be prepared by using the cement in a range of 50-70% by total weight of the concrete, and the amount of the supplementary cementitious material may be in the range of 30-50% by total weight of the concrete.
[0030] The present invention will be described in detail with reference to specific examples provided below. However, such examples should not be construed to limit the scope of the present invention.

EXAMPLE 1:
[0031] In this method, 9.6 kgs of waste quarry dust having alumina and silica close to 70% combined was ground with 400 grams of activator chemicals in the ball mill for 90 minutes and retention on the 45-micron sieve was found to be around 10%. The mixture of the activator chemical used along with waste quarry dust (WQD) during grinding comprises 200 grams of sodium sulfate having a pH greater than 9, 180 grams of calcium carbonate, 10 grams of sodium polyacrylate, 4 ml of Triethanolamine and 1 gram of sodium hexametaphosphate having a pH greater than 9 was blended and added along with the waste quarry dust during its grinding. Followed by concrete trials. Concrete trials were conducted by replacing the ordinary Portland cement 15% by weight of both modified and unmodified WQD. 150 X 150 mm cubes were cast and tested at different intervals.
[0032] Table 2. Trial results of concrete made using modified and unmodified WQD

Description Control Trial 1 Trial 2
OPC-CHETTINAD
(Kgs/m3) 400 340 340
WQD Modified
(Kgs/m3) 0 60 0
WQD Unmodified
(Kgs/m3) 0 0 60
Admixture % 0.45 0.45 0.45
Water/cement ratio 0.36 0.36 0.36
Fine Aggregate (Kgs/m3) 870 867 867
20 mm Aggregate (Kgs/m3) 721 719 719
12 mm Aggregate (Kgs/m3) 480 479 479
Water (Liters) 157 157 157
Workability Slump in mm
Initial COLLAPSE COLLAPSE COLLAPSE
At 30 min 240 200 200
At 60 min 180 170 160
Compressive Strength(N/mm2)
1 Day Strength 22.0 22.0 15.8
3 Days Strength 36.6 34.8 23.8
7 Days Strength 41.7 42.8 33.1
28 Days Strength 50.3 53.9 39.6

Experimental results indicate that the supplementary cementitious material (SCM) prepared through this method is able to replace 15% of Portland cement with modified waste quarry dust without affecting the strength of the concrete.

[0033] The advantages of the present invention are discussed herein:

The present invention provides a cost-effective and energy efficient method for preparation of a supplementary cementitious material from Industrial waste.
2. The present invention provides a method of activating waste quarry dust to be used as a supplementary cementitious material at room- temperature saving the energy expenditure.
3. The present invention provides a method of converting waste quarry dust into a supplementary cementitious material which does not require wet carbonation therefore, reducing the risk of corrosion.
4. The present invention provides a method to minimize the need for landfilling of waste quarry dust.
5. The supplementary cementitious material reacts with hydration products of cement to form additional binding phases which enhances the strength.
6. The method eliminates the use of the wet carbonization process, which is an expensive process.

[0034] While this invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the scope of the appended claims.
, Claims:WE CLAIM:
1. A method for preparation of supplementary cementitious material from industrial waste comprising the following steps:
(a) grinding industrial waste with chemical activators at room temperature until a homogenous mixture is obtained; and
(c) sieving the mixture obtained in step (a) through a sieve, to obtain supplementary cementitious material (SCM).
2. The method as claimed in claim 1, wherein the grinder is selected from a group consisting of a ball mill and the like.
3. The method as claimed in claim 1, the industrial waste is quarry dust.
4. The method as claimed in claim 1, wherein the sieve is selected from a group consisting of a 45-micron sieve.
5. The method as claimed in claim 1, wherein the industrial waste is present in a range of 70-99.8% by total weight of the supplementary cementitious material.
6. The method as claimed in claim 1, wherein the chemical activators are present in a range of 0.2% to 30% by the total weight of the supplementary cementitious material.
7. The method as claimed in claim 1, wherein the chemical activators are selected from a group comprising of alkali metal sulfate, alkali metal phosphate, alkali metal carbonate, alkali metal oxide/hydroxide, alkali salts of polyacrylic acid, hydrocarboxylic acid, and alkanolamine, or a combination thereof.
8. The method as claimed in claim 7, wherein the alkali metal oxides/hydroxides is selected from a group consisting of calcium hydroxide, magnesium hydroxide, lithium hydroxide, and barium hydroxide, or a combination thereof.
9. The method as claimed in claim 7, wherein the hydrocarboxylic acid is selected from a group consisting of citric acid, humic acid, tartaric acid, or a combination thereof.
10. The method as claimed in claim 7, wherein the alkali salts of polyacrylic acid are selected from a group consisting of sodium polyacrylate, or a combination thereof.
11. The method as claimed in claim 7, wherein the alkali metal phosphate is selected from a group consisting of sodium hexametaphosphate, tripotassium phosphate, sodium tripolyphosphate, or a combination thereof.
12. The method as claimed in claim 7, wherein the alkali metal carbonate is selected from a group consisting of sodium carbonate, calcium carbonate, lithium carbonate, potassium carbonate, or a combination thereof.
13. The method as claimed in claim 7, wherein the alkali salts of polyacrylic acid is sodium polyacrylate.
14. The method as claimed in claim 7, wherein the alkali metal sulfate is selected from a group consisting of sodium sulfate, calcium sulfate, and magnesium sulfate.
15. The method as claimed in claim 7, wherein the alkanolamine is selected from a group of triethanolamine, triisopropanolamine, or a combination thereof.
16. The method as claimed in claim 7, wherein the alkali metal sulfate and alkali metal phosphate have pH values greater than 9.
17. The method as claimed in claim 1, wherein the supplementary cementitious material is mixed in a range of 30-50% with cement in a range of 50-70% to form concrete with increased strength and durability of the concrete.