Description:
FORM 2

THE PATENTS ACT, 1970
(39 of 1970)

&

THE PATENTS RULES, 2003

COMPLETE SPECIFICATION
[See section 10, Rule 13]

“A METHOD FOR PREPARING A GEOPOLYMER CONCRETE BLOCK”

USHA S, AN INDIAN NATIONAL WHOSE ADDRESS IS DEPARTMENT OF CIVIL ENGINEERING, SREE NARAYANA GURUKULAM COLLEGE OF ENGINEERING, KADAYIRUPPU, ERNAKULAM, KERALA, PIN-682311, INDIA

THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THIS INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED

FIELD OF THE INVENTION:

[0001] The present invention relates to a geopolymer concrete building blocks made up of terracotta tile waste.

BACKGROUND OF THE INVENTION:

[0002] As already known concrete has many properties that make it a popular construction material. Over a period of time, it has been evident that the construction industry has been facing a number of challenges such as –
• depletion of resources,
• accessibility to affordable materials, and
• disposal of waste and generation of greenhouse gases.
[0003] The raw material used in the industry, especially the binder cement, used in cement concrete block utilizes a lot of natural resources like limestone and clay. Due to the growing population and their growing requirements, it can be clearly seen that these natural resources are being overused and are rapidly decreasing due to their continuous usage.
[0004] Manufacturing of cement is also a highly energy intensive process that causes environmental pollution by releasing carbon dioxide during its manufacturing. Dust pollution is another serious hazard caused from the preparation processes related to cement.
[0005] Cement concrete blocks (CCB), a prefabricated material mainly used to build walls, in which cement is used as a binder, are popularly used masonry units globally. Cement production leads to severe environmental pollution hazards at all stages, beginning with its production, transportation, processing, and application. Further, limestone and clay, the raw materials for cement are depleting due to the continuous usage. Energy utilization and carbon dioxide emission are high during the manufacturing of cement.
[0006] Due to depletion of raw material, the cost of cement is also increasing day by day making construction an expensive event. This is also leading to adulteration in cement composition(s). The adulteration in the cement not only compromises the quality of the cement but also has severe consequences for the durability and sustainability of the buildings. As a result, the lifespan of these structures is significantly reduced, leading to increased maintenance costs and environmental impact.
[0007] In this context, the inventors of the present invention have come up with an economically and environmentally friendly alternative.
[0008] CN109336434A describes the use of geothermal clay, a common industrial waste, in the development of geothermal resources as a raw material for binders. The geothermal clay is dried at 60°C for 48 hours, ground and calcined in a muffle furnace at 550-800°C for 2 hrs. Mixed with alkaline activator (mixing sodium hydroxide and sodium silicate) and poured into a mould and kept at room temperature for curing for 7-10 days to produce geothermal clay based geopolymer. IN202117004677 describes the use of natural clay which is low in kaolinite (less than 30% of kaolinite; - at least 20% of muscovite and/or illite; and - from 1% to 20% of smectite; - the muscovite and/or illite / kaolinite weight ratio being greater than 1% is calcinated. The calcined clay is alkali activated with sodium or potassium silicate and soda or potash to obtain kaolinite based geopolymer binder. CN107646025A describes a composition for building materials, comprising of a substrate containing an aluminosilicate compound such as flash metakaolin, which is obtained by flash calcining of powdered clay at a temperature of 600°C to 900°C for a few seconds and then rapidly cooling together with an alkaline activating solution. The alkaline activating liquid comprises of a sodium silicate source or a potassium silicate source and a base such as NaOH and/or KOH. Powdered mineral materials such as blast furnace slag, fly ash, plant fibers, aluminum powder etc. are added to produce prefabricated building elements.
[0009] Even though this area is a considerable area of interest for ongoing research, the closest and most recent research also had its own limitations. The major drawbacks of the most recent proposed research are as follow:
• Calcination of raw material takes place at a significantly high temperature such as 600° C to 900° C, which leads to a significantly high cost and also causes environmental pollution.
• Geothermal Clay, which is advised as an alternative, is not universally or readily available globally.
• Natural fresh clay, which is also advised as an alternative to binder, requires to be calcinated at significantly high temperature, resulting in high energy consumption and increased cost. Another disadvantage is, natural clay is also a limited resource and requires a large volume of water for processing, so with the huge cost, it also results in depletion of two other major limited resources.
• Another alternative proposed is using extra additives like GGBS making the technique less applicable in areas where GGBS is not available.
[0010]In order to overcome tthe major drawbacks as understood in research, the inventors of the present invention focus more on the resources which could be reused and harnessed efficiently, in order to cut the cost and also being environmentally friendly and long lasting. Therefore, waste generated during the production of materials and demolition of old buildings was considered.
[0011] Thus, the solutions provided by the present invention include economic utilization of an otherwise waste material; reduction in the environmental pollution; reduction in greenhouse gas emission such as CO2 in the process of making building materials, savings in energy, water and other natural resources go into the production of cement; and also less expensive construction material.

SUMMARY OF INVENTION:
[0012] In one aspect, present invention relates to a method of preparation of a geopolymer concrete building blocks, the method comprising of:
a) collecting waste terracotta obtained during terracotta tile production as binder, and powdering the waste terracotta to a fine particle size ranging from 50µm-100µm;
b) mixing the powdered waste terracotta with coarse aggregates and fine aggregates in a dry condition to obtain a mixture;
c) activating the mixture by adding an alkaline activator solution; and then mixing until a homogeneous colored mixture is obtained,
wherein ratio of the binder: fine aggregates: coarse aggregates is 1:3:6;
d) pouring the homogeneous mixture into a mould and pressing the mixture using a hydraulic block; and
e) obtaining the geopolymer concrete blocks at room temperature.

[0013] The alkaline activator comprises of sodium silicate and sodium hydroxide in a weight ratio of 1:1. The ratio of the alkaline activator to the binder is 0.6: 1.0.
The carbon dioxide emission during the production of one geopolymer concrete building block is 1.46 kg / block.
[0014] One of the aspects of present invention discloses the geopolymer concrete building block having a residual strength in a range of 70% - 90%, preferably about 70% - 75%. Another aspect of the present invention geopolymer concrete building blocks is their compressive strength which falls in the range of 4.55 N/mm2 – 6.55 N/mm2, preferably 5 N/mm2 – 6 N/mm2.
[0015] Another aspect of the present invention discloses geopolymer concrete building block of size 300 mm X 200 mm X 150 mm.

DETAILED DESCRIPTION OF THE INVENTION:
[0016] For convenience, before further description of the present disclosure, certain terms employed in the specification, and examples are delineated here. These definitions should be read in the light of the remainder of the disclosure and understood as by a person of skill in the art. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

[0017] The term “geopolymer” refers to inorganic, typically ceramic, alumino-silicate forming long-range, covalently bonded, non-crystalline (amorphous) networks.

[0018] “Terracotta waste” is derived from two terms “terra” and “cotta”, wherein “terra” means “baked earth” and “cotta” means “cooked earth”, it is a term used in some contexts of earth ware. Terracotta waste is a tile waste made up of terracotta, being used as a major ingredient in this application.

[0019] “Alkaline activator solution” is a well-known growing technology that involves a chemical reaction between sodium aluminosilicate precursor and an alkaline activator, at room temperature resulting into a hardened product.

[0020] “Ball milling” a method that grinds nanotubes into extremely fine powders. During the ball milling process, the collision between the tiny rigid balls in a concealed container will generate localized high pressure. Usually, ceramic, flint pebbles and stainless steel are used.

[0021] “Residual strength” the load or force (usually mechanical) that a damaged object or material can still carry without failing. Material toughness, fracture size and geometry as well as its orientation all contribute to residual strength.

[0022] “Compressive strength” is the capacity of concrete to withstand loads before failure. Of the many tests applied to the concrete, the compressive strength test is the most important, as it gives an idea about the characteristics of the concrete. Formula to calculate compressive strength is:
F = P/A
wherein F is the compressive strength of specimen in Mega Pascal; P is the maximum applied load by newton and A is the cross-sectional area estimated in mm2.

[0023] “Embodied Energy” is the total energy expenditure involved in material production. In this case, the sum of embodied energy of the ingredients of block such as coarse aggregate, fine aggregate, tile powder, NaOH and Na2SiO3, without considering the energy for transportation of materials at site, are taken as Embodied energy of one block.

[0024] “Coarse Aggregates” refers to irregular and granular particles of sand, gravel, or crushed stone having size in the range 4.75-12.5mm (passing through crushers or crushing machines of 12.5mm and retaining in 4.75mm).
[0025] “Fine aggregates” refers to regular sized granular particles having size in the range 0.15-4.75mm (Fineness Modulus 2.87).
[0026] The present invention relates to a method of preparation of the geopolymer concrete building blocks using terracotta tile waste as a binder. An embodiment of the present invention also describes the differences in the binders’ and their ability to create concrete building blocks. The present invention is directed towards a novel economical, productive, environment-friendly building blocks based on waste terracotta tile remnants suitable for structural masonry.
[0027] In one embodiment, the present invention relates to a method for preparing a geopolymer concrete building block. The method comprises steps of:
a. collecting waste terracotta obtained during terracotta tile production as binder, and powdering the waste terracotta to a fine particle size ranging from 50µm-100µm;
b. mixing the powdered waste terracotta with coarse aggregates and fine aggregates in a dry condition to obtain a mixture;
c. activating the mixture by adding an alkaline activator solution; and then mixing until a homogeneous colored mixture is obtained;
wherein ratio of the binder: fine aggregates: coarse aggregates is 1:3:6;
d. pouring the homogeneous mixture into a mold and pressing the mixture using a hydraulic block; and
e. obtaining geopolymer concrete blocks at room temperature.

[0028] During the process of method of production of the geopolymer concrete building blocks, the terracotta waste is collected from terracotta tile production unit. The waste terracotta collected can be powdered to obtain a fine particle with size ranging in between 50µm-100µm, preferably between 70µm-75µm. Ball milling is responsible for breaking down terracotta tile waste into a fine particle of the desirable size range.

[0029] An alkaline activator liquid comprising sodium silicate and sodium hydroxide (NaOH) added in specific ratio proportions can be added to the powdered fine terracotta particle obtained to form a mixture. The sodium silicate and sodium hydroxide can be in a weight ratio of 1:1. When an alkaline activator solution is added to the powdered terracotta waste, it activates the mixture. The alkaline activation takes place at an ambient room temperature, between a temperature of 25 °C – 35 °C, preferably in between 25 °C- 30 °C. The ratio of the alkaline activator to the binder is 0.6: 1.0.

[0030] The mixture as obtained, can be mixed rigorously and homogeneously to obtain a homogeneously colored mixture. The ratio of binder: fine aggregates: coarse aggregates in the homogenous mixture step (e) can be 1:3:6.

[0031] The homogeneous colored mixture as obtained can then be poured into the mould and pressed at 120-140 kg/cm2 using the hydraulic block making. After completion of the steps (a)-€, a geopolymer concrete block of size 300 mm X 200 mm X 150 mm is obtained. The geopolymer concrete block of the present invention looks like a cement brick but has enhanced properties over the universally known cement brick.
[0032] In one aspect, the geopolymer concrete block as prepared by the present invention shows very low carbon dioxide (CO2) emission. The carbon dioxide emission on production of the geopolymer concrete block as prepared by the present invention is 1.46 kg / block, i.e., 42.5% lower than that of conventional cement concrete block.
[0033] Another aspect of the present invention describes the terracotta waste is powered by the process of ball milling to a fine particle size ranging from 50µm-100µm, preferably 70µm-75µm.
[0034] In another embodiment, the present invention relates to a geopolymer concrete building block. One of the aspects of present invention discloses the geopolymer concrete building block having a residual strength in a range of 70% - 90%, preferably about 70% - 75%, after 3% concentrated acid exposure for 168 days.
[0035] Another aspect of the present invention discloses the compressive strength of the geopolymer concrete building blocks, the comprehensive strength falls in the range of 4.55 N/mm2 – 6.55 N/mm2, preferably 5 N/mm2 – 6 N/mm2.
[0036] Another aspect of the present invention discloses the block size of the concrete building block i.e., 300 mm X 200 mm X 150 mm and the carbon dioxide emission on production of one geopolymer concrete block is 1.46 kg / block.
[0037] The advantages of the geopolymer concrete block of the present invention are economic utilization of an otherwise waste material; reduction in the environmental pollution caused by the production of cement; reduction in greenhouse gas emission such as CO2;savings in energy, water and other natural resources go into the production of cement; and less expensive construction material.
Examples
[0038] Examples are set forth herein below and are illustrative of different amounts and types of reactants and reaction conditions that can be utilized in practicing the disclosure. It will be apparent, however, that the disclosure can be practiced with other amounts and types of reactants and reaction conditions than those used in the examples, and the resulting devices various different properties and uses in accordance with the disclosure above and as pointed out hereinafter.

[0039] Example 1: Forming Terracotta powder as a raw material and mixing of ingredients resulting into a geopolymer concrete building blocks
The waste terracotta, being used as a raw material, is collected from the terracotta tile waste generated during terracotta tile production. The collected terracotta tile waste is powdered to a fine particle whose size ranges in between 50µm-100µm, preferably 70µm-75µm, more preferably 75µm or less using the process of ball milling. This process requires much less energy, compared to other methods of size reduction. Calcination is not required while processing terracotta tile waste, it is required while processing raw material for cement, therefore it saves onto cost and energy required for the said process in comparison to the processing of raw material for cement. During the formation of a concrete building block, reactivity of clay containing raw material is not sufficient to react when treated with an alkaline activator, the reactivity of raw material can be increased by the process of calcination. However, while preparing the geopolymer concrete building block from terracotta waste showed a far greater potential to react when treated with an alkaline activator and hence the process of calcination is not required.
The alkaline activator liquid comprising of sodium silicate (Na2 SiO3) and sodium hydroxide (NaOH) in specific ratio such as alkaline activator to binder (tile powder) ratio 0.6:1, sodium silicate to sodium hydroxide (molarity 8M) ratio 1:1, is added to the powdered terracotta tile waste.
[0040] Geopolymer concrete blocks of 1:3:6 mix (binder: fine aggregates: coarse aggregates), suitable for load bearing units were casted as per IS: 2185 (part 1) – 2005 with the terracotta tile waste powder (which is used for this purpose for the first time) and alkaline activator, cured under room temperature. This process does not involve any calcination or high temperatures, making the process more energy efficient. The above reaction steps make the process of the present invention superior in terms of waste utilization, resource conservation, energy conservation, environmental protection, and convenience.
[0041] The homogeneous colored mixture obtained above is then cast on a mold to produce a block. The cast homogenous colored mixture is then pressed using hydraulic block making at 120-140 kg/cm2. Geopolymer concrete building blocks of size 300 mm X 200 mm X 150 mm are similar in structure to the concrete blocks existing in the market.

[0042] Example 2: Comparative analysis of the geopolymer concrete block and cement concrete blocks based on residual compressive strength after acid and sulphate exposure
The residual and compressive strength of the brick (regularly used concrete block) were calculated of the block specimens using the standard compression testing machine by applying load at controlled rate, in comparison to the inventive geopolymer block. Results of the compressive strength of the geopolymer blocks (5.55 N/mm2) is strong enough to meet the requirements (= 5 N/mm2 ) as per IS: 2185 Part1(2005) for concrete blocks. Also, the physical properties such as acid and sulphate resistance, CO2 emission, embodied energy of geopolymer concrete block and cement concrete block were compared. Superior performance of geopolymer concrete block over cement concrete block in terms of acid and sulphate resistance is confirmed from the results presented in Table 1 and Table 2 of the specification.
[0043] Approximately 71% and 75% of the initial strengths were observed as residual strengths of geopolymer concrete block for long term acid immersion for 168 days in 3% concentrated H2SO4 and HCl respectively, whereas only 25% and 59% of residual strength was observed for cement concrete block in similar conditions.
[0044] Geopolymer blocks reported 73% of their initial strength as residual strength in long term (168 days) 3% concentrated sulphate immersion, whereas 69% of residual strength was observed for cement blocks in similar conditions.
[0045] The calculated embodied energy value for geopolymer concrete block is 5.15 MJ / block and that of cement concrete block is 15.17 MJ / block, which clearly shows that embodied energy of geopolymer concrete block is 66% lower than that of cement concrete block. The detailed calculation of embodied energy of one block is shown in Table 3 of the specification.
[0046] Table 1 shows a comparative analysis of geopolymer concrete block and cement concrete block in terms of residual compressive strength after acid exposure

Type of exposure Days of immersion Residual compressive strength in %
Cement concrete block Geopolymer concrete block
Natural 0 100 100
3% concentrated HCl acid 7 80.05 92.28
14 72.93 87.14
56 68.5 83.17
168 58.7 75.25
3% concentrated H2SO4 acid 7 94.24 97.03
14 80.05 85.57
56 26.68 77.82
168 24.87 71.29

[0047] Table 2 shows a comparative analysis of geopolymer concrete block and cement concrete block in terms of Residual compressive strength after sulphate exposure

Type of exposure Days of immersion Residual compressive strength in %
Cement concrete block Geopolymer concrete block
Natural 0 100 100
3% concentrated Na2SO4 7 81.4 93.47
14 79.9 83.56
56 71.18 79.21
168 69.37 73.31

[0048] Table 3 shows an embodied energy calculation per building block for geopolymer concrete block and cement concrete block

Material Quantity
(Kg) Embodied energy at source (MJ/kg) Total energy for one block
Cement block Geopolymer block
Coarse aggregate 13.97 0.1 1.4 1.4
Fine aggregate 6.98 0.02 0.14 0.14
Cement 2.33 5.85 13.63 -
Tile powder 2.33 0.31 - 0.72
NaOH 0.17x0.97 4.98 - 0.82
Na2SiO3 0.7x0.55 5.37 - 2.07
Total energy for one block 15.17 MJ 5.15MJ

[0049] Example 4. Comparative analysis between geopolymer concrete blocks and cement concrete blocks on the carbon emission

CO2 emission calculations were done based on the production of one block in the laboratory and presented in Table 4 of the specification. The CO2 emission on production of cement block is 2.54 kg / block and that of geopolymer concrete block is 1.46 kg / block, i.e., 42.5% lower than that of cement concrete block.
[0050] Table. 4 shows CO2 emission calculation for per building block for geopolymer concrete block and cement concrete block

Material Quantity
(kg)
CO2 emission /kg production (kg) Total CO2 emission for one block (kg)
Cement block Geopolymer block
Coarse aggregate 13.97 0.04 0.56 0.56
Fine aggregate 6.98 0.01 0.07 0.07
Cement 2.33 0.82 1.91 -
Tile powder 2.33 0.02 - 0.05
NaOH 0.17x0.97 1.91 - 0.31
Na2SiO3 0.7x0.55 1.22 - 0.47
Total CO2 emission for one block (kg) 2.54 kg 1.46 kg

[0051] Results and Discussions:
The obtained geopolymer concrete building block held a lot of advantages over the existing concrete building blocks, the advantages are as mentioned below:
(a) Economic utilization of an otherwise waste material: The geopolymer concrete block is made up of waste terracotta waste, therefore it’s utilization of waste, making it pocket friendly.
(b) Reduction in environmental pollution caused by the production of cement: Carbon dioxide emission on production of one cement block is 2.54 kg, while that on the production of geopolymer concrete block is 1.46 kg.
(c) Embodied energy: The embodied energy for the production of a cement block is 15.17 MJ while for the production of geopolymer block is 5.15 MJ. There is at least 60-65% decrease in the embodied energy.
(d) Difference in residual compressive strength: The geopolymer concrete building has almost 5-10 % higher residual compressive strength on exposure to the sulphate and 66-70% higher residual strength on exposure to the acidic substrate, making it a perfect building material.
(e) No resources exploited or depleted: Since the raw material for the production of geopolymer building block is different from that of the cement building block, it does not causes or leads to depletion of endangered raw materials such as clay.
, Claims:
1. A method for preparing a geopolymer concrete building block, the method comprising of:
f) collecting waste terracotta obtained during terracotta tile production as binder, and powdering the waste terracotta to a fine particle size ranging from 50µm-100µm;
g) mixing the powdered waste terracotta with coarse aggregates and fine aggregates in a dry condition to obtain a mixture;
h) activating the mixture by adding an alkaline activator solution;
and then mixing until a homogeneous colored mixture is obtained;
wherein ratio of the binder: fine aggregates: coarse aggregates is 1:3:6;
i) pouring the homogeneous mixture into a mould and pressing the mixture using a hydraulic block; and
j) obtaining the geopolymer concrete blocks at room temperature.

2. The method, as claimed in claim 1, wherein powdering the terracotta waste by a process of ball milling to a fine particle size ranging from 50µm-100µm, preferably 75µm.

3. The method, as claimed in claim 1, wherein the alkaline activation takes place at an ambient room temperature.

4. The method, as claimed in claim 3, wherein the temperature at which the alkaline activation takes place ranges between 25 °C – 35 °C, preferably in between 25 °C- 30 °C.

5. The method, as claimed in claim 1, wherein the alkaline activator comprises of sodium silicate and sodium hydroxide in a weight ratio of 1:1.

6. The method, as claimed in claim 1, wherein ratio of the alkaline activator to the binder is 0.6: 1.0.

7. The method, as claimed in claim 1, wherein carbon dioxide emission is 1.46 kg/block.

8. The method, as claimed in claim 1, wherein the geopolymer block obtained is of size 300 mm X 200 mm X 150 mm.

9. A geopolymer concrete building block, as obtained by the method as claimed in claim 1, wherein the geopolymer concrete has a residual strength in a range of 70% -90%, preferably about 70 % - 75%.

10. The geopolymer concrete building block, as claimed in claim 9, wherein the geopolymer block has a compressive strength in a range of 4.55 N/mm2 – 6.55 N/mm2, preferably 5 N/mm2 – 6 N/mm2.