WO2022175908A1

WO2022175908A1 - Mould composition and a process for its preparation

Info

Publication number: WO2022175908A1
Application number: PCT/IB2022/051512
Authority: WO
Inventors: Alok Giridhari Kale; Akshay Prakash Deokar
Original assignee: Alok Giridhari Kale
Priority date: 2021-02-19
Filing date: 2022-02-21
Publication date: 2022-08-25

Abstract

The present disclosure relates to a mould composition. The mould composition comprises waste foundry sand, at least one binding agent, at least one aggregate, and optionally at least one filler. The present disclosure further relates to a process for the preparation of a mould composition. The mould composition of the present has improved compression strength and is devoid of efflorescence even after using waste foundry sand in the composition.

Description

MOULD COMPOSITION AND A PROCESS FOR ITS PREPARATION

FIELD

The present disclosure relates to a mould composition and a process for its preparation.

DEFINITIONS

As used in the present disclosure, the following terms are generally intended to have the meaning as set forth below, except to the extent that the context in which they are used indicates otherwise.

Waste foundry sand (WFS) / Used foundry sand (UFS) refers to a discarded material coming from ferrous (iron and steel) and nonferrous (copper, aluminium, and brass) metal casting industries.

Curing refers to a process in which a moulded object is subjected to setting, by providing adequate moisture, temperature, and time, to allow the moulded product to achieve the desired properties for its intended use.

Compression strength refers to a maximum compressive stress wherein, under gradually applied load, solid material will sustain without fracture.

Face material refers to a material when applied on the surface of the base material, provides improved aesthetics to the moulded product.

Binding agent (binder) refers to a substance that holds or binds other materials together mechanically, chemically, or as an adhesive, to form a cohesive unit.

Filler refers to a substance that is added to prepare necessary mass and reduce the usage of expensive materials.

Portland Pozzolana Cement (PPC) refers to an integrated cement which is formed by synthesizing OPC cement with pozzolanic materials in a specific proportion.

Fly ash refers to a fine grey powder consisting mostly of spherical, glassy particles that are produced as a byproduct in coal-fired power stations.

Kerbstone refers to a series of stones that form a kerb (the pavement).

Keystone refers to a wedge-shaped piece, the central stone at the summit of an arch, locking the other pieces in place. BACKGROUND

The background information hereinbelow relates to the present disclosure but is not necessarily prior art.

The construction industry uses a variety of building materials for the construction of different structures. The building material such as cement, concrete, bricks, hollow blocks, solid blocks, pavement blocks, and tiles are being produced by using natural resources such as stones, sand, clay, and the like.

Conventionally, natural sand and gravels are extensively used building materials. The demand for natural sand in the construction industry has increased a lot, resulting in stress on the availability of the sand resources. Sand mining results in loss of land because of river or coastal erosion and lowering of the water table. The volume of sand being extracted due to huge demands is having a major impact on deltas, rivers, and marine ecosystems.

Burnt clay bricks are another most extensively used building material. They are used in constructing a variety of structural members such as masonry walls, foundations, and the like. In order to use burnt clay bricks for construction, certain desirable properties such as compressive strength, density, thermal stability, porosity, sound insulation, fire resistance, durability, and the like are required. Conventionally used burnt clay bricks have numerous disadvantages such as inferior quality, non-uniform edges, and environmental pollution such as air pollution and land pollution during production. Air pollution takes place due to the burning of bricks by using coal and wood as a fuel, thereby producing greenhouse gases. Secondly, for manufacturing these bricks, a huge amount of clay is required. This clay is generally obtained from agricultural land. Thus, it causes land pollution due to the loss of good fertile soil and damages the environment.

In the present scenario, the construction industry is facing global challenges of advanced technology, energy conservation, rapid automation, and high productivity and hence the use of economic and environment friendly material is a major concern. Further, the fast-growing continuous technological development has led to the enormous amount of waste, wherein the accumulation of such waste is a major environmental concern.

There is, therefore, felt a need for a mould composition that overcomes the above-mentioned drawbacks. OBJECTS

Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows:

An object of the present disclosure is to ameliorate one or more problems of the prior art or to at least provide a useful alternative.

Another object of the present disclosure is to provide a mould composition.

Another object of the present disclosure is to provide a mould composition for preparing moulded products such as pavers, bricks, blocks, and the like.

Still another object of the present disclosure is to provide a process for preparing a mould composition.

Yet another object of the present disclosure is to provide an economical and eco-friendly process for preparing a mould composition.

Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure.

SUMMARY

The present disclosure relates to a mould composition and a process for its preparation. In an aspect, the mould composition comprises a dry waste foundry sand in an amount in the range of 60 mass% to 75 mass% with respect to the total mass of the composition; at least one binding agent in an amount in the range of 6 mass% to 15 mass% with respect to the total mass of the composition; at least one aggregate in an amount in the range of 15 mass% to 40 mass% with respect to the total mass of the composition; and optionally at least one filler in an amount in the range of 2 mass% to 15 mass% with respect to the total mass of the composition.

In another aspect, the process for the preparation of a mould composition comprises drying a predetermined amount of waste foundry sand at a predetermined temperature for a predetermined time period to obtain a dry waste foundry sand. The dry waste foundry sand is mixed with at least one binding agent, and optionally at least one filler to obtain a mixture. To the mixture, a predetermined amount of aggregates are blended at a speed in the range of 50 rpm to 100 rpm to obtain the mould composition. The mould composition is mixed with a predetermined amount of water before use. DETAILED DESCRIPTION

Embodiments are provided so as to thoroughly and fully convey the scope of the present disclosure to the person skilled in the art. Numerous details are set forth, relating to specific components, and methods, to provide a complete understanding of embodiments of the present disclosure. It will be apparent to the person skilled in the art that the details provided in the embodiments should not be construed to limit the scope of the present disclosure. In some embodiments, well-known processes, well-known apparatus structures, and well- known techniques are not described in detail.

The terminology used, in the present disclosure, is only for the purpose of explaining a particular embodiment and such terminology shall not be considered to limit the scope of the present disclosure. As used in the present disclosure, the forms "a,” "an," and "the" may be intended to include the plural forms as well, unless the context clearly suggests otherwise. The terms "comprises," "comprising, "“including,” and “having,” are open ended transitional phrases and therefore specify the presence of stated features, integers, steps, operations, elements, modules, units and/or components, but do not forbid the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The particular order of steps disclosed in the method and process of the present disclosure is not to be construed as necessarily requiring their performance as described or illustrated. It is also to be understood that additional or alternative steps may be employed.

Conventional mould composition used in the preparation of moulded products have numerous disadvantages such as inferior quality, non-uniform edges, and causes environmental pollution such as air pollution and land pollution during production.

The present disclosure provides a mould composition and a process for its preparation.

In an aspect of the present disclosure, there is provided a mould composition.

In accordance with an embodiment of the present disclosure, the mould composition comprises a dry waste foundry sand in an amount in the range of 60 mass% to 75 mass% with respect to the total mass of the composition; at least one binding agent in an amount in the range of 6 mass% to 15 mass% with respect to the total mass of the composition; at least one aggregate in an amount in the range of 15 mass% to 40 mass% with respect to the total mass of the composition; and optionally at least one filler in an amount in the range of 2 mass% to 15 mass% with respect to the total mass of the composition In accordance with an embodiment of the present disclosure, the dry waster foundry sand is characterized by having, a. grain shape selected from angular, subangular, very angular, rounded, sub rounded and well rounded; b. specific gravity in the range of 1.9 to 2.5; c. fineness modulus in the range of 2.3 to 2.5; d. moisture content in the range of 0.1% to 6%; e. fineness number in the range of 40 to 70 AFS (American Foundry Society); f. pH in the range of 4 to 10; g. clay lumps and friable particles in the range of 40 to 70 AFS; h. bentonite clay in an amount in the range of 7 to 15%; i. lustrous coal in an amount in the range of 2 to 7%; j. iron particles in an amount in the range of 0.05 to 0.4%; k. silica content in an amount in the range of 70% to 90%; l. aluminium oxide in an amount in the range of 2.5% to 5%; m. mean particle size (d90) in the range of 0.1 mm to 1 mm; and n. mean particle size (dlO) in the range of 0.01 mm to 0.1mm.

In accordance with an embodiment of the present disclosure, the particle size of the dry waste foundry sand is in the range of 0.01 mm to 1.5 mm. In an embodiment, the particle size of the dry waste foundry sand is in the range of 0.075 mm to 0.6 mm. In an exemplary embodiment of the present disclosure, the particle size of the dry waster foundry sand is 0.3 mm.

In accordance with an embodiment of the present disclosure, the binding agent is selected from the group consisting of Portland Pozzolana Cement (PPC), Ordinary Portland Cement (OPC), Portland Slag Cement (PSC), low heat cement, hydrophobic portland cement, rapid hardening cement, extra rapid hardening cement, sulphate resisting cement, quick-setting cement, blast furnace slag cement, high alumina cement, and white cement. In an exemplary embodiment of the present disclosure, the binding agent is Ordinary Portland Cement (OPC).

In accordance with an embodiment of the present disclosure, the aggregates are at least one selected from the group consisting of stone chips, crush sand, plaster sand, manufactured sand (m-sand), slag sand, shredded plastics, plastic granules, plastic waste, and gravels. In an exemplary embodiment of the present disclosure, the aggregate is stone chips.

In accordance with an embodiment of the present disclosure, the particle size of the aggregates is in the range of 0.1 mm to 20 mm.

In accordance with an embodiment of the present disclosure, the filler is optionally used and selected from the group consisting of fly ash, bottom ash, pond ash, volcanic ash, and agro waste ash.

In accordance with an embodiment of the present disclosure, the composition comprises at least one colour pigment.

In accordance with an embodiment of the present disclosure, the colour pigment is at least one selected from the group consisting of iron oxide pigment, yellow oxide pigment, and chrome oxide pigment.

In accordance with an embodiment of the present disclosure, the colour pigment is optionally added in the composition.

In accordance with an embodiment of the present disclosure, the colour pigment is in the range of 0.001 mass% to 0.1 mass% with respect to the total mass of the composition.

In accordance with an embodiment of the present disclosure, the mass ratio of the dry waste foundry sand to the binding agent is in the range of 4:1 to 10:1.

In accordance with an embodiment of the present disclosure, the composition is used for preparing a moulded product selected from the group consisting of bricks, blocks, pavers, hollow blocks, kerbstones, and keystones.

In accordance with an embodiment of the present disclosure, the moulded product is characterized by having a compression strength in the range of 4 N/mm 2 to 10 N/mm 2.

In accordance with an embodiment of the present disclosure, the moulded product is devoid of efflorescence. In another aspect of the present disclosure, there is provided a process for the preparation of a mould composition.

The process is described in detail.

In a first step, a predetermined amount of waste foundry sand is dried at a predetermined temperature for a predetermined time period to obtain a dry waste foundry sand.

In accordance with an embodiment of the present disclosure, the predetermined temperature is in the range of 80°C to 100°C. In an exemplary embodiment, the temperature is 90°C.

In accordance with an embodiment of the present disclosure, the predetermined time period is in the range of 2 minutes to 15 minutes. In an exemplary embodiment, the predetermined time period is 10 min.

In accordance with an embodiment of the present disclosure, the moisture content in the dry waste foundry sand is in the range of 0.1 % to 6 %.

In a second step, the dry waste foundry sand, at least one binding agent, and optionally at least one filler is mixed to obtain a mixture.

In accordance with an embodiment of the present disclosure, the amount of dry waste foundry sand is in the range of 60 mass% to 75 mass% with respect to the total mass of the composition. In an exemplary embodiment, the amount of dry waste foundry sand is 60 mass% with respect to the total mass of the composition.

In accordance with an embodiment of the present disclosure, the binding agent is selected from the group consisting of Portland Pozzolana Cement (PPC), Ordinary Portland Cement (OPC), Portland Slag Cement (PSC), low heat cement, hydrophobic portland cement, rapid hardening cement, extra rapid hardening cement, sulphate resisting cement, quick-setting cement, blast furnace slag cement, high alumina cement, and white cement. In an exemplary embodiment, the binding agent is Ordinary Portland Cement (OPC).

In accordance with an embodiment of the present disclosure, the binding agent is in the range of 6 mass% to 15 mass% with respect to the total mass of the composition. In an exemplary embodiment, the amount of binding agent is 7.2 mass% with respect to the total mass of the composition. In another exemplary embodiment, the amount of binding agent is 7.4 mass% with respect to the total mass of the composition. In still another exemplary embodiment, the amount of binding agent is 7.6 mass% with respect to the total mass of the composition.

In accordance with an embodiment of the present disclosure, the filler is selected from the group consisting of fly ash, bottom ash, pond ash, volcanic ash, and agro-waste ash. In an exemplary embodiment, the filler is fly ash.

In accordance with an embodiment of the present disclosure, optionally the filler is in the range of 2 mass% to 15 mass% with respect to the total mass of the composition.

In a third step, a predetermined amount of aggregates are blended with the mixture to obtain the mould composition.

In accordance with an embodiment of the present disclosure, the aggregate is at least one selected from the group consisting of stone chips, crush sand, plaster sand, manufactured sand (m-sand), slag sand, shredded plastics, plastic granules, plastic waste, and gravels. In an exemplary embodiment, the aggregate is stone chips.

In accordance with an embodiment of the present disclosure, the aggregates are in an amount in the range of 15 mass% to 40 mass% with respect to the total mass of the composition. In an exemplary embodiment, the amount of aggregates is 32 mass% with respect to the total mass of the composition.

In accordance with an embodiment of the present disclosure, the blending speed is in the range of 50 rpm to 100 rpm.

In accordance with an embodiment of the present disclosure, the colour pigment is added along with aggregates.

In accordance with an embodiment of the present disclosure, the colour pigment is at least one selected from the group consisting of iron oxide pigment, yellow oxide pigment, and chrome oxide pigment. In an exemplary embodiment, the colour pigment is iron oxide.

In accordance with an embodiment of the present disclosure, the colour pigment is in the range of 0.001 mass% to 0.1 mass% with respect to the total mass of the composition. In an exemplary embodiment of the present disclosure, the amount of colour pigment is 0.004 mass% with respect to the total mass of the composition. In accordance with an embodiment of the present disclosure, a predetermined amount of water is blended with the mould composition for a time period in the range of 3 minutes to 10 minutes prior to preparing mould.

In accordance with an embodiment of the present disclosure, the predetermined amount of water is in the range of 1 mass% to 3 mass% with respect to the total mass of mould composition.

In accordance with an embodiment of the present disclosure, the mould composition is mixed with water followed by passing to a die of the desired shape to provide the moulded product. The moulded product is dried for a time period in the range of 10 hours to 24 hours to obtain a dried moulded product. The dried moulded product is subjected to air/water curing for a time period in the range of 15 days to 30 days to obtain a cured moulded product.

In accordance with an embodiment of the present disclosure, a predetermined amount of colour pigment is added to the base material and mixed to form a face material. The face material is then passed to die and again compacted over the surface of the cured moulded product to form pavers.

The mould composition of the present disclosure comprises dry waste foundry sand as a raw material, hence, the use of natural sand and clay can be reduced, thereby making composition economical and environment friendly. By using the composition of the present disclosure, the moulded products achieve early strength, resulting in zero damages and edge breakages. The moulded products can easily shifted to the stockyard after 18-24 hours without any damages and breakages.

The moulded products prepared by using the mould composition of the present disclosure can be delivered to the market after an air and water curing. The mould composition works well on the existing high-pressure moulding machines and hence, does not require an additional capital cost. The mould composition comprises inexpensive and easily available alternative materials, while the strength properties assessed are better than conventional available moulded products (such as bricks, pavers, and the like). Other key features include negligible dimensional variation, good compression strength, suitability for light and heavy traffic applications, zero damages, and edge breakages of the products during transportation. The mould composition of the present disclosure can reduce the time and cost of the mould product while maintaining excellent quality and strength. Ultimately, one can get high productivity and cost reduction in term of consumption of water and curing cost.

The foregoing description of the embodiments has been provided for purposes of illustration and not intended to limit the scope of the present disclosure. Individual components of a particular embodiment are generally not limited to that particular embodiment but are interchangeable. Such variations are not to be regarded as a departure from the present disclosure, and all such modifications are considered to be within the scope of the present disclosure.

The present disclosure is further described in light of the following experiments which are set forth for illustration purpose only and not to be construed for limiting the scope of the disclosure. The following experiments can be tested to scale up to industrial/commercial scale and the results obtained can be extrapolated to the industrial scale.

EXPERIMENTAL DETAILS

Example 1:

100 kg of waste foundry sand (WFS) (particle size 0.3 mm) having a moisture content of 2% was heated at 90 °C for 10 minutes to obtain the dry waste foundry sand. The moisture content of the dry waste foundry sand was 0.5%.

Example 2: Preparation of the mould composition in accordance with the present disclosure

1440 kg of dry waste foundry sand (WFS) (particle size 0.3 mm), 170 kg of Ordinary Portland cement (OPC), were charged to the blender to obtain a mixture. To the mixture, 756 kg of stone chips of 10 mm to 2 mm size and 100 gm of iron oxide pigment were blended to obtain the mould composition. The so obtained mould composition was blended with 36 kg of water and mixed for a period of 5 minutes before use.

Example 3: Preparation of the mould composition in accordance with the present disclosure

1440 kg of dry waste foundry sand (WFS) (particle size 0.3 mm), 176 kg of ordinary portland cement (OPC), were charged to the blender to obtain a mixture. To the mixture, 756 kg of shredded plastics of 10 mm to 2 mm size were blended to obtain the mould composition. The so obtained mould composition was blended with 40 kg of water and mixed for a period of 5 minutes before use.

Example 4: Preparation of the mould composition in accordance with the present disclosure

1440 kg of dry waste foundry sand (WFS) (particle size 0.3 mm), 180 kg of ordinary portland cement (OPC), were charged to the blender to obtain a mixture. To the mixture, 756 kg of stone chips of 10 mm to 2 mm size and 100 gm of iron oxide pigment were blended to obtain the mould composition. The so obtained mould composition was blended with 36 kg of water and mixed for a period of 5 minutes before use.

Example 5: The properties of the bricks (4 inch) prepared by using the composition of Example 2 of the present disclosure were compared with the commercially available bricks (according to IS- 12894-2002). The bricks were evaluated for compression strength, and efflorescence.

The results are provided in table 1 below,

Table 1:

Example 6:

The properties of the bricks (5 inch) prepared by using the composition of Example 2 of the present disclosure, were compared with the commercially available bricks (according to IS- 12894-2002). The bricks were evaluated for compression strength, and efflorescence. The results are provided in table 2 below,

Table 2:

Example 7:

The properties of the bricks (6 inch) prepared by using the composition of Example 2 of the present disclosure, were compared with the commercially available bricks (according to IS- 12894-2002). The bricks were evaluated for compression strength, and efflorescence. The results are provided in table 3 below,

Table 3:

It is evident from the above examples that the bricks manufactured by using the composition of the present disclosure, have enhanced compression strength and absence of efflorescence. The comparative examples employ natural source clay, natural source crushed stone, whereas the composition of the present disclosure achieves better physical properties by using the water foundry sand.

TECHNICAL ADVANCEMENTS

The present disclosure described hereinabove has several technical advantages including, but not limited to, the realization of, a mould composition that

• uses waste foundry sand;

• has excellent compression strength;

• has good stability;

• serves the purpose of base composition in bricks as well as paver making;

• has faster curing rates and requires lower curing cost and time;

• that has negligible dimensional variations when used in the formation of moulded product;

• is economical and environment friendly, and a simple and economical process for the preparation of the mould composition and the moulded products.

Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising, will be understood to imply the inclusion of a stated element, integer or step,” or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the invention to achieve one or more of the desired objects or results. While certain embodiments of the inventions have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Variations or modifications to the formulation of this invention, within the scope of the invention, may occur to those skilled in the art upon reviewing the disclosure herein. Such variations or modifications are well within the spirit of this invention.

The numerical values given for various physical parameters, dimensions and quantities are only approximate values and it is envisaged that the values higher than the numerical value assigned to the physical parameters, dimensions and quantities fall within the scope of the invention unless there is a statement in the specification to the contrary.

While considerable emphasis has been placed herein on the specific features of the preferred embodiment, it will be appreciated that many additional features can be added and that many changes can be made in the preferred embodiment withoutdepartingfromtheprinciplesofthedisclosure.Theseandotherchangesin the preferred embodiment of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.

Claims

CLAIMS:

1. A mould composition comprising: a. dry waste foundry sand in an amount in the range of 60 mass% to 75 mass% with respect to the total mass of the composition; b. at least one binding agent in an amount in the range of 6 mass% to 15 mass% with respect to the total mass of the composition; c. at least one aggregate in an amount in the range of 15 mass% to 40 mass% with respect to the total mass of the composition; and d. optionally at least one filler in an amount in the range of 2 mass% to 15 mass% with respect to the total mass of the composition.

2. The composition as claimed in claim 1, wherein said dry waste foundry sand is characterized by having: a. grain shape selected from angular, subangular, very angular, rounded, sub rounded, and well rounded; b. specific gravity in the range of 1.9 to 2.5; c. fineness modulus in the range of 2.3 to 2.5; d. moisture content in the range of 0.1% to 6%; e. fineness number in the range of 40 to 70 AFS; f. pH in the range of 4 to 10; g. clay lumps and friable particles in the range of 40 to 70 AFS; h. bentonite clay in an amount in the range of 7 to 15%; i. lustrous coal in an amount in the range of 2 to 7%; j. iron particles in an amount in the range of 0.05 to 0.4%; k. silica in an amount in the range of 70% to 90%;

1. aluminium oxide in an amount in the range of 2.5% to 5%; m. mean particle size (d90) is in the range of 0.1 mm to 1 mm; and n. mean particle size (dlO) is in the range of 0.01 mm to 0.1mm.

3. The composition as claimed in claim 1, wherein a particle size of said waste foundry sand is in the range of 0.01 mm to 1.5 mm.

4. The composition as claimed in claim 1, wherein said binding agent is selected from the group consisting of Portland Pozzolana Cement (PPC), Ordinary Portland Cement (OPC), Portland Slag Cement (PSC), low heat cement, hydrophobic portland cement, rapid hardening cement, extra rapid hardening cement, sulphate resisting cement, quick-setting cement, blast furnace slag cement, high alumina cement, and white cement.

5. The composition as claimed in claim 1, wherein said aggregates is at least one selected from the group consisting of stone chips, crush sand, plaster sand, manufactured sand (m-sand), slag sand, shredded plastics, plastic granules, plastic waste, and gravels.

6. The composition as claimed in claim 5, wherein a particle size of said aggregates is in the range of 0.1 mm to 20 mm.

7. The composition as claimed in claim 1, wherein said filler is at least one selected from the group consisting of fly ash, bottom ash, pond ash, volcanic ash, and agro-waste ash.

8. The composition as claimed in claim 1, wherein said composition comprises at least one colour pigment.

9. The composition as claimed in claim 8, wherein said colour pigment is at least one selected from the group consisting of iron oxide pigment, yellow oxide pigment, and chrome oxide pigment.

10. The composition as claimed in claim 1, wherein a mass ratio of said waste foundry sand to said binding agent is in the range of 4:1 to 10:1.

11. The composition as claimed in claim 1, wherein said composition is used for preparing a moulded product selected from the group consisting of bricks, blocks, pavers, hollow blocks, kerbstones, and keystones.

12. The composition as claimed in claim 11, wherein said moulded product is characterized by having a compression strength in the range of 4 N/mm 2 to 10 N/mm 2.

13. A process for the preparation of a mould composition as claimed in claim 1, said process comprising the following steps: a. drying a waste foundry sand at a predetermined temperature for a predetermined time period to obtain a dry waste foundry sand; b. mixing said dry waste foundry sand, at least one binding agent, optionally at least one filler to obtain a mixture; and c. blending at least one aggregate to said mixture at a speed in the range of 50 rpm to 100 rpm to obtain the mould composition;

14. The process as claimed in claim 13, wherein said predetermined temperature is in the range of 80°C to 100°C.

15. The process as claimed in claim 13, wherein said predetermined time period is in the range of 2 minutes to 15 minutes.

16. The process as claimed in claim 13, wherein said predetermined amount of water is in the range of 1 mass% to 3 mass% with respect to the total mass of the mould composition.