Description:FORM 2

THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENT RULES, 2003

COMPLETE SPECIFICATION

(See Section 10 and Rule 13)

Title of invention:
AUTOCLAVE AERATED CONCRETE (AAC) COMPOSITION, SYSTEM AND PROCESS FOR WALL PANELS

APPLICANT:
PIDILITE C-TECHOS WALLING LTD.
An Indian entity having address as
Regent Chambers, 7th floor, Jamnalal Bajaj Marg,
208, Nariman point, Mumbai 400021, Maharashtra, India

The following specification particularly describes the invention and the method in which it is to be performed.
CROSS-REFERENCE TO RELATED APPLICATIONS AND PRIORITY
The present application does not claim priority from any patent application.
TECHNICAL FIELD
The present invention is directed to a composition for an autoclave aerated concrete (AAC). More particularly, the present invention relates to a non-reinforced autoclave aerated concrete (AAC) composition for wall panels, and a process and a system for producing the non-reinforced AAC wall panels.
BACKGROUND
In current construction practice, the walls of a building are constructed using bricks or concrete blocks and sometimes an autoclave aerated concrete (AAC) blocks which are affixed together by using a binding mortar such as cement or polymers etc., at required joints. The external part of the building and finished surface of walls is plastered again by cement mortars.
The prevailing mode of wall construction also needs skilled masonry to maintain wall alignment and later curing of joints and plastered surfaces by watering them regularly. For curing, one needs adequate fresh water supply facilities and as part of final finish of the walls, the process of plastering is mandatory. If not attended by proper bonding, curing and finishing, the walls may fail early during its service period with prominent cracks. This actually makes construction of block/brick walls a slow process and problematic at site of execution because of varying sizes, shapes, and low strength materials. This mode of construction also requires lot of man-hours and increases the cost of labour in the overall construction process. These typical brick/blocks-based construction methodology exhibits problems of cracks, leakages and associated complications (e.g. dampness, pealing of paints etc.) more commonly in case of fast track construction activities, which is the current construction trend for Medium and High rise buildings.
The problem continues in terms of resources spent and hiring of multiple labour forces that conducts the masonry activities. Another problem lies in transporting, erection and removal of scaffolding material at construction site. Furthermore, the waiting and drying period of finished wall surfaces runs into many days before paint can be applied on the walls only to delay the completion of project.
In state of art, RU2681166C1 discloses about technology of autoclaved aerated concrete (AAC) blocks. The prior art discloses about a raw mix for the production of blocks from cellular concrete containing lime, cement, quartz sand, solids in return sludge, gypsum, aluminum powder, chopped basalt fibre and/or chopped fiberglass, and water. The prior art discloses about autoclave aerated concrete (AAC) products with a sand based mix recipe.
In state of art, WO2008126125A2 discloses about an autoclaved cellular concrete comprising silica sand, lime, cement, dust and/or paste aluminum, fibers, and water, wherein fibers can glass and/or carbon fibers, or another kind of fibers, such as cellulose fibers, steel fibers. The prior art discloses about AAC products with a silica sand-based mix recipe.
In state of art, methods for the manufacturing of AAC block are disclosed. However, AAC block and AAC wall panels are entirely different in terms of dimensions and method for production of same. AAC Blocks, being a cuboid of smaller dimension, are manufactured as a unit with nearly equivalent length, breadth and thickness which remains stable in given dimension during and after autoclaving. However, AAC wall panels have considerably lesser value for one dimension namely thickness in relation to the other dimensions viz. length and breadth. The slenderness factor of such AAC wall panels makes it difficult to maintain its dimensions stable and crack-free during and after autoclaving process.
The conventional methodologies of wall construction are slow due to unproductive practices leading to lower construction turn-over, thus creating a constantly increasing gap in the demand and supply of habitable spaces.
What is needed is a durable, environmentally friendly and cost-effective an autoclave aerated concrete (AAC) wall panels for wide scale and diverse application in the building and construction industry.
Therefore, there is a long-standing need to provide a composition for an autoclave aerated concrete (AAC) along with a system and process for the manufacturing of autoclave aerated concrete (AAC) wall panels which overcomes the problems in the prior art without using steel reinforcement and for reducing the carbon footprint significantly.
SUMMARY
This summary is provided to introduce aspects related to a composition for an autoclave aerated concrete (AAC) for wall panel. This summary is also provided to introduce aspects related to a process and a system for manufacturing autoclave aerated concrete (AAC) wall panels. This summary is however not intended to disclose essential features of the innovation, nor is it intended to determine, limit or restrict the scope of the innovation.
In one aspect of the present invention, an autoclave aerated concrete (AAC) wall panel composition is disclosed. The said composition may comprise a fly ash in a weight percent between 50 to 80%. The said composition may comprise return slurry in a weight percent between 10 to 30%, The said composition may comprise ordinary portland cement (OPC) in a weight percent between 5 to 25%. The said composition may comprise a premixed black box admixture in a weight percent between 0.5 to 20%. The said composition may comprise one or more additives and water.
In one of the embodiments, the autoclave aerated concrete (AAC) composition for wall panels may comprise a fly ash slurry in a weight percent between 60 to 70%. The said composition may comprise a return slurry in a weight percent between 15 to 20%. The said composition may comprise an ordinary portland cement (OPC) in a weight percent between 10 to 20%. The said composition may comprise a premixed black box admixture in a weight percent between 1 to 15%. The said composition may comprise one or more additives and water.
In another embodiment, a composition of a premixed black box admixture is disclosed herein. The said premixed black box admixture may comprise a marble/granite powder in a weight percent between 5 to 20%. The said premixed black box admixture may comprise a silica sand in a weight percent between 60 to 90%. The said premixed black box admixture may comprise a mixture of mineral fibres in a weight percent between 1 to 10%, wherein the said mineral fibres further may comprise 70 to 95 % of wollastonite mineral fibres and 5 to 30% of basalt fibres.
In an embodiment, the said one or more additives may include but not limited to lime, gypsum, surfactant, aluminium powder and a mixture thereof.
In still another embodiment, the surfactant may be selected from at least one of soluble oil and dichromate.
In one embodiment, the weight percent of lime may range between 4 to 6%, the weight percent of gypsum may range between 0.25 to 1.5%, the weight percent of surfactant may range between 0.001 to 0.1% and the weight percent of aluminium powder may range between 0.03 to 0.15%.
In one embodiment, the said autoclave aerated concrete (AAC) composition may be devoid of steel reinforcements.
In another embodiment, by referring to figure 1 and figure 2 a process for the preparation of an autoclave aerated concrete (AAC) wall panel is disclosed. The said process comprises of various successive steps. The said process may comprise a step of adding a predefined amount of a mixture of fly ash/pond ash and water to a mixture comprising return slurry, ordinary portland cement, black box admixture, and one or more additives in a concrete mixer for a time period between 5-10 minutes to obtain a wet mixture. In one embodiment, the said concrete mixer may be preheated to 35-45 °C, by applying a steam at a pressure less than 1.5 bar.
In one embodiment, the wet density of the return slurry and fly ash/pond ash slurry may be between 1400-1600 kg/m3.
The said process further may comprise a step of moulding and aerating the said wet mixture into a moulding unit maintained at temperature between 38-45 °C to obtain an aerated concrete cake having predefined size and shape.
The said process further may comprise a step of de-moulding and transferring the said aerated concrete cake to a cutting section. The said process further may comprise a step of cutting the said aerated concrete cake in the cutting section, wherein the aerated concrete cake is ordinated by tilting, rotation or both for alignment and ensure better autoclaving and easy separation in the cutting section.
The said process further may comprise a step of autoclaving the said aerated concrete cakes in an autoclave chamber at a predetermined temperature, pressure and time to obtain the autoclave aerated concrete (AAC) wall panel.
In still another embodiment, the temperature and pressure for the step of autoclaving may be maintained between 90-200 °C and 0-15 bar respectively. In one embodiment, the predetermined time period for the step of autoclaving may be between 0-14 hrs.
In one embodiment, the peak temperature and peak pressure during holding period in an autoclave maybe maintained between 195-200°C and 10-15 bar respectively.
In another embodiment, the peak pressure may be maintained between 12-15 bar for the holding period between 4-8 hrs for the overall 14 hrs cycle in the step of autoclaving.
In one embodiment, the autoclave aerated concrete (AAC) wall panel may be a non-reinforced autoclave aerated concrete (AAC) wall panel.
In one exemplary embodiment, the compressive strength of the non-reinforced autoclave aerated concrete (AAC) wall panel, tested for a cuboidal specimen is between 2-6 N/mm2, preferably between 2-3 N/mm2.
In still another exemplary embodiment, the bulk density of the said non-reinforced autoclave aerated concrete (AAC) wall panel, is between 550-700 kg/m3.
In one embodiment, a mixing speed of the concrete mixer is greater than 600 rpm.
In one embodiment, the said cutting assembly maybe a wire cutting assembly.
In yet another embodiment, the said autoclave aerated concrete (AAC) wall panels maybe Non-reinforced AAC wall panels.
In one embodiment a system for preparation of autoclave aerated concrete (AAC) wall panel is disclosed. The system may comprise a concrete mixer enabled for the mixing of ingredients of composition of autoclave aerated concrete (AAC) to obtain a wet mixture. The system may comprise a moulding unit enabled from aeration and moulding of wet mixture to obtain an aerated concrete cake of the wet mixture. The system may comprise a cutting assembly enabled for the cutting of aerated concrete cake. The system may further comprise an autoclave chamber enabled for the autoclaving the aerated concrete cake to obtain the autoclave aerated concrete (AAC) wall panel.
In one embodiment, the concrete mixer may comprise one or more separate inlets enabled for the addition of feed materials.
In another embodiment, the cutting assembly may be a wire cutting assembly.
In yet another embodiment, wherein the mixing speed of the concrete mixer may be greater than 600 rpm.
List of Abbreviations
AAC: Autoclave aerated concrete
BBA: Black Box admixture
OPC: Ordinary portland cement
Other features and advantages of the present invention will be apparent from the following detailed description of the invention which illustrates, by way of example, the principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
The detailed description is given with reference to the accompanying figure. In the figure, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the drawings to refer like features and components.
Figure 1 illustrates an overview of the process for the preparation of an autoclave aerated concrete (AAC) wall panel, in accordance with an embodiment of the present invention.
Figure 2 illustrates an overview of the system (200) for the preparation of an autoclave aerated concrete (AAC), in accordance with an embodiment of the present invention.
Figure 3 illustrates a pressure profile for the step of autoclaving, in accordance with an embodiment of the present invention.
Figure 4 illustrates a temperature profile for the step of autoclaving, in accordance with an embodiment of the present invention.
The figures depict embodiments of the present disclosure for purposes of illustration only. One skilled in the art will readily recognize from the following description that alternative embodiments of the steps illustrated herein may be employed without departing from the principles of the disclosure described herein.
DETAILED DESCRIPTION
The foregoing detailed description of embodiments is better understood when read in conjunction with the appended drawings. For the purpose of illustrating the disclosure, there are shown in the present document example constructions of the disclosure; however, the disclosure is not limited to the specific design disclosed in the document and the drawings.
The detailed description is provided with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the drawings to refer like features and components.
The present invention is directed to provide an autoclave aerated concrete (AAC) composition for wall panels. The present invention is also directed to provide a process and system for the preparation of an autoclave aerated concrete (AAC) wall panels. The present disclosure eliminates the requirement of reinforcements in the aerated concrete and provides uniform, integrated wall system with fewer joints and improved strength, and stability. The autoclave aerated concrete (AAC) wall panels as disclosed herein are easy for transportation due to its high strength.
In order to address the above-mentioned problems and problems persisting with the conventional techniques of brick/block wall system, the present invention comes as a major breakthrough.
These aforesaid problems of typical brick/ block-based construction and finishing of walls are overcome by the present invention which relates to a composition, process and system for the production of non-reinforced AAC wall panels for masonry elements of a building. As a ready to assemble wall element, non-reinforced AAC wall panels of standard dimensions invented herein may be used in construction of infill wall system of any building offering faster work completion cycle, fewer joints, minimal or no curing and better finishing with paints.
In the present invention, a composition for Non-reinforced AAC wall panels is provided along with an innovative process and system for the production of Non-reinforced AAC Wall Panels. Such wall panels as disclosed in the present invention, due to absence of steel reinforcement, are light weight, easy to assemble, carpenter friendly for custom cutting at site of construction and fastens the production cycle of construction.
The said composition as provided herein is enabling and enhancing the strength and stability of the herein invented AAC wall Panel. The AAC wall panel as invented herein does not use steel reinforcement and hence are lightweight. The non-reinforced AAC wall panels as disclosed herein would lessen the carbon footprint significantly.
In one of the embodiments, an autoclave aerated concrete (AAC) composition for wall panels is disclosed herein. The said composition may comprise a fly ash in a weight percent between 50 to 80%. The said composition may comprise a return slurry in a weight percent between 10 to 30%. The said composition may comprise an ordinary portland cement (OPC) in a weight percent between 5 to 25%. The said composition may comprise a premixed black box admixture in a weight percent between 0.5 to 20%. The said composition may comprise one or more additives and water. The fly ash/pond ash as used in the present invention are waste product generated at coal fuelled thermal power plants. Fly ash/ pond ash are generally discharged into landfills if not used which is an environmental hazard in causing land degradation. The usage of fly ash/pond ash in majority and in place of a scarce natural resource viz. sand for the manufacturing process is contributory in making the invented AAC wall panels environment friendly. Moreover, fly ash/pond ashes are lightweight and offer fine particles that are able to contribute for pore filling action and improvement in particle packing creating a dense micro-structure. Additionally, there is a possibility of strength gaining of AAC wall panels due to their pozzolanic activity which is advantageous for the present invention.
In one of the embodiments, the autoclave aerated concrete (AAC) composition for wall panels may comprise a fly ash slurry in a weight percent between 60 to 70%. The said composition may comprise a return slurry in a weight percent between 15 to 20%. The said composition may comprise an ordinary portland cement (OPC) in a weight percent between 10 to 20%. The said composition may comprise a premixed black box admixture in a weight percent between 1 to 15%. The said composition may comprise one or more additives and water.
In another embodiment, a composition of the premixed black box admixture is disclosed herein. The said premixed black box admixture may comprise a marble/granite powder in a weight percent between 5 to 20. The said premixed black box admixture may comprise a silica sand in a weight percent between 60 to 90%. The said premixed black box admixture may comprise a mixture of mineral fibres in a weight percent between 1 to 10%, wherein the said mineral fibres further may comprise 70 to 95 % of wollastonite mineral fibres and 5 to 30% of basalt fibres. The proportion or the overall percentage weight of silica sand used in as used in the present invention is very minimal and the sand part is replaced by use of fly ash/pond ash in majority in the present invention.
In one embodiment, the said one or more additives may include but not limited to lime, gypsum, surfactant, aluminium powder and a mixture thereof. In still another embodiment, the surfactant may be selected from at least one of soluble oil and dichromate.
In one embodiment, the weight percent of lime may range between 4 to 6%, the weight percent of gypsum may range between 0.25 to 1.5%, the weight percent of surfactant may range between 0.001 to 0.1% and the weight percent of aluminium powder may range between 0.03 to 0.15%. In one embodiment, the said autoclave aerated concrete (AAC) composition is devoid of steel reinforcements.
In yet another embodiment, a process for the preparation of an autoclave aerated concrete (AAC) is disclosed. The said process comprises of various successive steps. The sequential process provided in the present invention is based on multiple trials from manufacturing of Non-reinforced AAC wall panels at plant, achieving high strength of AAC wall panels, Efficient raising period for concrete cake, reduced/elimination of cracks in the non-reinforced AAC wall panels produced are verified for finalizing on the sequential process invented herein. This invention further relates to optimization of mix ingredients, mixing sequence, autoclaving process; control parameters for methodology of production of Non-reinforced AAC Wall Panels. Such novel modifications to the process of production ensures better strength and stability of AAC Wall Panels which does not require reinforcement steel. Non-reinforced AAC Wall Panels produced as per the invention herein can save on time of construction, induce better uniformity of wall system with fewer joints.
In one embodiment, the process of preparation of the autoclave aerated concrete may comprise a step of adding a premixed amount of fly ash/pond ash and water to a mixture comprising return slurry, ordinary portland cement, black box admixture, and one or more additives in a concrete mixer for a time period between 5-10 minutes to obtain a wet mixture. In one embodiment, the said concrete mixer may be preheated to 35-45 °C, by applying a steam at a pressure less than 1.5 bar.
In one embodiment, the said return slurry is generated after the first cycle of mixing and may be used at 15 to 20% of total weight of mix composition after matching the wet density with fresh fly ash/pond ash slurry. The purpose of return sludge/slurry is to maintain a concentration of activated sludge in the aeration tank sufficient for the desired degree of treatment. The return slurry is a recycling wash residue of ready mixed concrete including the condensing used cement sludge. In one embodiment, the wet density of the return slurry and fly ash/pond ash slurry may be between 1400-1600 kg/m3.
The said process further may comprise a step of moulding and aerating the wet mixture into a moulding unit maintained at a temperature between 38-45°C to obtain an aerated concrete cake having a predefined size and shape.
The said process further may comprise a step of de-moulding and transferring the aerated concrete cake to a cutting section. The said process further may comprise a step of cutting aerated concrete cake in the cutting section, wherein the aerated concrete cake may be ordinated by tilting, rotation or both for alignment and ensure better autoclaving and easy separation in the cutting section.
The said process further may comprise a step of autoclaving the aerated concrete cakes in an autoclave chamber at a predetermined temperature, pressure and time to obtain the autoclave aerated concrete (AAC) wall panel.
Modifications applied to the autoclaving step may in terms of pressure and temperature profile with respect to time of autoclaving.
In still another embodiment, the temperature and pressure for the step of autoclaving may be maintained between 90-200 °C and 0-15 bar respectively.
In one embodiment, the predetermined time period for the step of autoclaving may be between 0-14 hrs.
In another embodiment, the peak temperature and peak pressure during holding period in an autoclave may be maintained between 195-200°C and 10-15 bar respectively.
In another embodiment, the peak pressure is maintained between 12-15 bar for the holding period between 4-8 hrs for the overall 14 hrs cycle in the step of autoclaving. The peak pressure is enabled to ensure the Non-reinforced AAC wall panel inside autoclave is completely cooked and doesn’t develop any thermal cracks post autoclaving.
In one embodiment, the autoclave aerated concrete (AAC) wall panel may be a non-reinforced autoclave aerated concrete (AAC) wall panel, wherein the said non-reinforced autoclave aerated concrete (AAC) wall panel may be devoid of steel reinforcements.
In one exemplary embodiment, the compressive strength of the non-reinforced autoclave aerated concrete (AAC) wall panel, tested for a cube specimen is between 2-6 N/mm2, preferably between 2-3 N/mm2, wherein the cube specimen is obtained by cutting a portion of the said autoclave aerated concrete (AAC) wall panel.
In still another exemplary embodiment, the bulk density of the said non-reinforced autoclave aerated concrete (AAC) wall panel is between 550-700 kg/m3.
In one embodiment, a mixing speed of the concrete mixer is greater than 600 rpm.
In one embodiment, the said cutting assembly maybe a wire cutting assembly.
In another embodiment, by referring to figure 2, a system for the preparation of an autoclave aerated concrete (AAC) wall panel is disclosed. The said system may comprise a concrete mixer (201) enabled for the mixing of ingredients of composition for autoclave aerated concrete (AAC) to obtain a wet mixture. The said system further may comprise a moulding unit (202) enabled for the aeration and moulding of the wet mixture to obtain an aerated concrete cake of the wet mixture. The said system may comprise a cutting assembly (203) enabled for the cutting of aerated concrete cake. The said system may comprise an autoclave chamber (204) enabled for the autoclaving the aerated concrete cake to obtain autoclave aerated concrete (AAC) wall panel.
The said AAC Wall Panels as disclosed in the present invention herein are produced with a novel material composition in mix design, mixing sequence, innovative modifications applied to autoclaving process and a systematic production methodology for the achievement of necessary strength parameters and stability.
In one implementation, the disclosed Non-reinforced AAC Wall Panels are customizable as per site requirements due to absence of reinforcing steels and offers great productivity in terms of project completion cycle.
In another embodiment, the said concrete mixer (201) further may comprises one or more inlets (205, 206) enabled for the addition of feed materials. The feed materials may be composition for AAC wall panel production selected from fly ash/pod ash, lime, cement, gypsum, aluminium powder/paste, soluble oil, dichromate, surfactants, Black Box Admixture (BBA), and water in accordance with the embodiment of the present invention.
The present invention is concerned to the production of Non-reinforced AAC wall panels of standard dimensions which works seamlessly as a part of the overall wall system, replacing the conventional brick/block wall construction practices. Herein invented Non-reinforced AAC Wall Panels provides necessary strength for masonry element with less number of joints offering better resistance to horizontal forces, better rigidity, stability, increased frictional resistance, strength gain and high quality surface finishing that are structurally efficient.
The present invention covers the aspects of specific mix ingredients for Non-reinforced AAC Wall Panels along with the novel methodology of mixing, production, autoclaving and packing/handling of Non-reinforced Autoclaved Aerated Concrete (AAC) Wall Panels. The Non-reinforced AAC Wall Panels invented herein are produced with a unique material composition in a controlled process flow for the achievement of necessary strength parameters and stability.
Absence of reinforcing steels makes it a unique AAC wall panel element and offers great productivity in terms of project completion cycle owing to its easy handling and customization at site level execution with minimum demand for manual labour.
It may be noted that the usage of herein invented Non-reinforced AAC Wall Panels in construction will be beneficial to the Structural designers, contractors, builders, laborers, end-users. Furthermore, the absence of steel in the herein Non-reinforced AAC wall Panels makes it easy to cut and customize for matching the required floor height during installation.
The light weight, easy handling and carpenter friendly properties of Non-reinforced AAC Wall Panels directly contribute to reduction of dead loads of the structure and faster work completion cycle of construction projects, reduced number of masonry joints, enhanced structural stability, better surface finishing and paint rendering. The non-reinforced AAC wall Panels due to their light weight and ease of handling fastens the construction cycle.
Further, the non-reinforced AAC wall panels as disclosed herein require minimal or no fresh water curing as one of the technical benefits of herein invented Non-reinforced AAC wall Panels when used as wall system in buildings.
As a value addition to the current invention, it is appreciated that the various operations, processes and methods disclosed herein can be performed in a systematic order for avoiding wastage of material resources starting from production to transportation stage. The autoclave aerated concrete (AAC) wall panels of the present invention having excellent physical properties which provides necessary strength for masonry element, with less number of joints offering better resistance to horizontal forces, better rigidity, stability, increased frictional resistance and high quality surface finishing that are structurally efficient.
The process as disclosed in the present inventions aims to manufacture Non-reinforced AAC wall panels which may be customized at site to match for the required floor height during the installation as wall system in buildings. Thus, the Non-reinforced AAC wall panels as disclosed in the present invention is composed of environment friendly materials and are structurally efficient for application in high volume construction practices which on usage could reduce cost of construction, effective savings on fresh water for curing and improved productivity with lesser human effort.
In one embodiment, the Non-reinforced AAC Wall panels in accordance with embodiment of the present disclosure may be primarily used in any of the following applications to construction industry such as Infill Wall system in building as internal partition wall and external wall of any building, a Decking element, and a Compound wall element. The Non-reinforced AAC Wall panels may be used as an alternative to traditional brick/block masonry walls including conventional AAC block masonry elements in buildings.
The instant subject matter is further described by the following examples:
Example 1:
The present disclosure describes the method for the production of non-reinforced autoclave aerated concrete (AAC) wall panels which are suitable for site requirement of various floor heights of the buildings. A novel method comprising an innovative material composition for non-reinforced autoclave aerated concrete (AAC) and the method for the preparation of wall panels comprising said non-reinforced autoclave aerated concrete (AAC) is depicted herein.
Further, as disclosed herein invented Non-reinforced AAC wall Panels utilize a considerable amount of industrial wastes during its production thus reducing the load on Environmental disposal. The said composition for autoclave aerated concrete (AAC) for wall panels comprises predetermined amounts of a fly ash, a return slurry, an ordinary portland cement, a premixed black box admixture, one or more additives such as lime, a gypsum, a surfactant, an aluminium powder and a mixture thereof and water. The said premixed black box admixture further comprises predetermined amounts of granite /marble powder, silica sand and mineral fibres at an optimized premixed proportion, wherein the said mineral fibres comprises 70 to 95 %of wollastonite mineral fibres and 5 to 30% of basalt fibres.
The said composition as provided herein is enabling and enhancing the strength and stability of the herein invented Non-reinforced AAC wall Panel. In one exemplary embodiment, by referring to table 1 which provides the novel material composition by percentage weight of materials adopted for the production of Non-reinforced AAC wall panels. The premixed composition of Black Box admixture (BBA) is presented in table 2.
Table 1: Material composition for AAC wall panel production
Material Composition by % wt.
Fly ash /Pond ash 60 to 70
Lime 4 to 6
Cement 10 to 20
Gypsum 0.25 to 1.5
Aluminium Powder /Paste 0.03 to 0.15
Soluble Oil/Dichromate/Surfactant 0.001 to 0.1
Black Box Admixture (BBA) 1 to 15
Water As required to create Fly ash/Pond ash Slurry of wet density in range of 1400 to 1500kg/m3.

In one embodiment, the said return slurry is generated after the first cycle of mixing and may be used at 15 to 20% of total weight of mix composition after matching the wet density with fresh fly ash/pond ash slurry. i.e. the wet density of the return slurry and fly ash/pond ash slurry maybe between 1400-1600 kg/m3.
Table 2: Material composition of Black Box Admixture (BBA)
Material Composition by % wt. Role
Marble/Granite Powder 5 to 20 Filler/ binder
Silica Sand 60 to 90% Filler/ binder
Mineral Fibres
[Wollastonite (70 to 95 %) and Basalt fibres (5 to 30%) in ready mixed state] 1 to 10% Reinforcing agents for dimensional stability

BBA composition was optimized based on plant level productions and practical observations for dimensionally stable AAC wall panels.
The related test for compressive strength parameters of the invented AAC wall panels are reported to satisfy the requirements specified for masonry wall units as per IS 2185 (III): 1984 specifications tested as per standard procedures.
Example 2:
In one embodiment, AAC wall panel specimens with the size of 150 mm.cube without BBA and with BBA are tested for the for compressive strength parameters. The cube specimen is obtained by cutting a portion of the said autoclave aerated concrete (AAC) wall panel. The Comparative data for the test results are provided below in table 3. The compressive strength without BBA is found in between 3 to 3.5 N/mm2 and the compressive strength with BBA is found to be >4.5 N/mm2.
Table 3: Comparative data for Compressive strength with and without BBA
Sr. No. Compressive strength
N/mm2 (Without BBA) Compressive strength N/mm2 (With BBA)
1 3.4 4.5
2 3.3 4.6
3 3.4 4.5
Example 3:
In one embodiment, AAC wall panel specimens with the size of 150 mm cube without BBA and with BBA are tested for the for density. The 150 mm cube specimen is obtained by cutting a portion of the said autoclave aerated concrete (AAC) wall panel. The comparative data for the test results are provided below in table 4. The density without BBA at 10+ 2 % moisture content is found in between 650 to 675 kg/m3 and density without BBA in oven dry condition is found in between 580- 615 kg/m3.
In still another embodiment, the density of AAC wall panel specimens with BBA at 10+ 2 % moisture content is found in between 675 to 695 kg/m3. And the density with BBA in oven dry condition is found in between 610- 625 kg/m3.
Table 4: Comparative data for density with and without BBA
Sr. No. Density at 10+ 2 % moisture content (kg/m3) Density in oven dry condition
(kg/m3)
With BBA Without BBA With BBA Without BBA
1 690.2 673.6 621.5 610.2
2 676.1 650.5 612.5 586.7
3 676.9 - 620.6 -
Example 4:
In another embodiment, a process for the preparation of an autoclave aerated concrete (AAC) is disclosed. Below Table 5 presents the sequence of addition and mixing time of the components as disclosed in Table 1 and 2. A composition for an autoclave aerated concrete (AAC) for wall panels comprising various ingredients and the sequence of addition of the said ingredients and the time of mixing at each stage to complete the mixing process is provided in below table 5. The total time of mixing is not more than 8 minutes and the wet mixture obtained by mixing said ingredients should be poured into moulding unit within 60 seconds of mixing after addition of aluminium powder/paste.
Table 5: Sequence of raw material addition and mixing time
Sequence/ Order of addition Raw material Stage Mixing time in minutes
1 Wet Fly ash/Pond ash Slurry and Return Slurry 2
3 Cement 2
4 Lime 0.5
5 Black Box Admixture 1
6 Gypsum 0.5
7 Dichromate/ Soluble Oil 0.5
8 Aluminium Powder/paste 1

The fresh wet mixture of ingredients is to be poured into moulds to fill up to 50 to 60% of given mould volume. It is allowed to raise/aerate in the mould as wet concrete cake before proceeding for step of cutting. A simple dip measurement test is adopted by end of wet concrete cake raising stage to check the suitability of the wet concrete cake for the process of cutting.
Example 5: Production of Non-reinforced AAC wall Panels:
In one embodiment, a process for the preparation of an autoclave aerated concrete (AAC) wall panels is provided. With the adoption of composition and appropriate modifications in the process for the manufacturing of aerated concrete (AAC) wall panels, which covers multiple key experimental observations which are recorded during the manufacturing process and compiled as systematic methodology for production of the said wall panels. The detailed order and innovative methodology of production of Non-reinforced AAC wall panels is briefed in below steps.
Step 1: Concrete mixer Management:
The concrete mixer shall be warmed up to 42°C before adding ingredients of the said composition aerated concrete (AAC) wall panels using steam, wherein the steam pressure sent to mixer should be less than 1.5 bar. Concrete mixer shall be of a working speed greater than 600 rpm.
Step 2: Preparation of wet mixture:
Mixing of dry fly ash/ pond ash & water to prepare fresh slurry of density in the range of 1.5-1.7 kg/litre (1400-1600 kg/m3). The return Slurry, which is generated after the first production cycle of Non-reinforced AAC wall panels, needs to be at the same density as fly Aah slurry and not to be less than 1300 kg/m3. Maintaining the slurry prepared as per required density in separate tanks, ready to be pumped to the said concrete mixer. A premixed amount of fly ash/pond ash and water is added to a mixture comprising return slurry, ordinary portland cement, black box admixture, and one or more additives in a concrete mixer for a time period between 5-10 minutes to obtain a wet mixture.
Step 3: Pre curing/ Raising in Mould:
Pouring the wet mixture obtained in the above step 3 to a moulding unit which is enabled for the aeration and moulding of the said wet mixture to obtain an aerated concrete cake of the wet mixture. the level of material poured in the mould should be about 50-60% of the total mould volume. Shifting and maintaining the mould comprising wet mixture on to pre-curing chamber maintained at approximately 38-45 °C. Allowing the concrete cake to rise up in about 25-30 minutes for better quality of aeration. After the mass is fully raised in mould and aeration process is complete, allowing for additional setting time of approximately 60 to 90 minutes within the pre curing chamber to attain a cutting ready state.
Step 4: Cutting Preparations and cutting of aerated concrete cake:
After completion of the pre-curing period, the hardness of the cake is measured by a dip measurement technique using a simple dip rod and a 30 cm measuring scale. Dip test is performed to measure the dip for the wet concrete cake needs to be at specified value as per the thickness of wall panel to be cut into e.g. Penetration of dip rod shall be at 140 to 150 mm for panels of 100 mm thickness; 120-130 mm for a panel of 150 mm thickness and 110-120 mm for a panel of 200 mm thickness. Once values for dip test are satisfactory, the wet concrete cake can be allowed for cutting. The said cutting process was be adopted for both horizontal and vertical cutting as per requirement with slow and vibration free cutting line aligned with 0.8 to 1 mm thick cutting wire.
Step 5: Post Cutting Movement and Tilting of the aerated concrete cake: Careful and vibration/shock free movement of cut aerated concrete cake was be ensured on slow moving rail track. An automated tilting mechanism is adopted at this stage for tilting/ rotating the wire cut aerated concrete cake by 90° to the horizontal in order to align the said aerated concrete cake vertically as side-by-side panel stack before sending it into the autoclave chamber. Tilting in such a manner ensures better autoclaving of panels and easy separation after autoclaving. Before autoclaving the wire cut aerated concrete cakes are allowed to rest at room temperature for a maximum of 60 minutes time period.
Step 6: Autoclaving of wire cut aerated concrete cakes:
Ensuring the temperature difference between the inside of autoclave chamber & wire cut aerated concrete cakes which shall not be more than 10°C. If required, vacuuming of autoclave shall be adopted to achieve thermal stability. Feeding the aerated concrete cakes and closing the lid and autoclave for 14 hours cycle and autoclaving the aerated concrete cakes in an autoclave chamber at a predetermined temperature, pressure and time to obtain the autoclave aerated concrete (AAC) wall panel.
Step 7: Post Auto clave wall panel separation:
After completion of autoclaving cycle, the autoclaved Non-reinforced AAC wall panel are removed from the said autoclave within 30 minutes, and Non-reinforced AAC wall panels are separated physically within 1 hour. The separated wall panels of 1meter and 2 meter are then transported by forklifts or suitable machinery to the storage area for packing purpose.
Example 6: Modifications to Autoclaving Process for Production of Non-reinforced AAC wall Panel:
The process for the manufacturing of Non-reinforced AAC wall panel includes an innovative system of autoclaving process with modification to the autoclave pressure and temperature profile to be maintained during the autoclaving process. Such novel modifications contribute towards maintaining required strength and stability of wall panels after autoclaving. Figure 3 and Figure 4 graphically represent the variation of pressure and temperature with time proposed to be maintained inside the autoclave chamber during the autoclaving process for the herein invented Non-reinforced AAC wall Panel. The peak temperature and peak pressure during holding period in an autoclave is maintained between 195-200 °C and 10-15 bar respectively, wherein the peak pressure is maintained between 12-15 bar for the holding period between 4-8 hrs for the overall 14 hrs cycle in the step of autoclaving. The peak pressure is enabled to ensure the Non-reinforced AAC wall panel inside autoclave is completely cooked and doesn’t develop any thermal cracks post autoclaving.
Example 7: Tests for the strength parameters of wall panels
The Non-reinforced AAC wall panels produced in accordance with an embodiment of the present invention are tested for the strength parameters to satisfy the requirements specified for masonry wall units as per IS 2185 (III): 1984 specifications and tested as per standard procedures. Tests for the strength parameters such as compressive strength, bulk density/oven dry density are performed, and the results are found satisfactory and within the range as per standards. The test results are produced in below table 6 and 7:
Table 6: Test results for compressive strength
Sr. No. Size of wall panel
(mm) Compressive strength (N/mm2) minimum Compressive strength as per as per IS 2185 (III): 1984 (Reaffirmed 2015)
1 150 mm cube
(Without moisture conditioning) 4.1 For grade 1-Min. 4.0 N/mm2
For grade 2- Min. 3.0 N/mm2
2 150 mm cube
(With moisture conditioning) 4.2 For grade 1-Min. 4.0 N/mm2
For grade 2- Min. 3.0 N/mm2
Table 7: Test results for bulk density/ oven dry density
Sr. No. bulk density/ oven dry density (Kg/m3) minimum Compressive strength as per as per IS 2185 (III): 1984 (Reaffirmed 2015)
1 590 551-650 Kg/m3
The embodiments, examples and alternatives of the preceding paragraphs or the description and drawings, including any of their various aspects or respective individual features, may be taken independently or in any combination. Features described in connection with one embodiment are applicable to all embodiments, unless such features are incompatible.
The foregoing description shall be interpreted as illustrative and not in any limiting sense. A person of ordinary skill in the art would understand that certain modifications could come within the scope of this disclosure.
Although implementations for a composition, process and system (200) for autoclave aerated concrete (AAC) for wall panels have been described in language specific to structural features and/or methods, it is to be understood that the appended claims are not necessarily limited to the specific features or methods described. Rather, the specific features and methods are disclosed as examples of implementations of a composition, process and system (200) for autoclave aerated concrete (AAC) for wall panels.

, Claims:WE CLAIM:
1. An autoclave aerated concrete (AAC) wall panel composition comprising:
a fly ash in a weight percent between 50 to 80%;
a return slurry in a weight percent between 10 to 30%;
an ordinary portland cement (OPC) in a weight percent between 5 to 25%;
a premixed black box admixture in a weight percent between 0.5 to 20%;
one or more additives; and
water.
2. The composition as claimed in claim 1, comprising:
a fly ash/pond ash in a weight percent between 60 to 70%;
a return slurry in a weight percent between 15 to 20%;
an ordinary portland cement in a weight percent between 10 to 20%;
a premixed black box admixture in a weight percent between 1 to 15%;
one or more additives; and
water.
3. The composition as claimed in claim 1, wherein the premixed black box admixture comprises of:
a marble/granite powder in a weight percent between 5 to 20%;
a silica sand in a weight percent between 60 to 90%; and
a mixture of mineral fibres in a weight percent between 1 to 10%.
4. The composition as claimed in claim 3, wherein the mineral fibres comprise 70 to 95 % of wollastonite mineral fibres and 5 to 30% of basalt fibres.
5. The composition as claimed in claim 1, wherein the one or more additives are selected from lime, gypsum, surfactant, aluminium powder and a mixture thereof.
6. The composition as claimed in claim 5, wherein the surfactant is selected from at least one of soluble oil and dichromate.
7. The composition as claimed in claim 5, wherein the weight percent of lime is between 4 to 6%, the weight percent of gypsum is between 0.25 to 1.5%, the weight percent of surfactant is between 0.001 to 0.1%, and the weight percent of aluminium powder is between 0.03 to 0.15%.
8. The composition as claimed in claim 1, wherein the autoclave aerated concrete (AAC) composition is devoid of steel reinforcements.
9. The composition as claimed in claim 1, wherein the autoclave aerated concrete (AAC) wall panel is a Non-reinforced AAC wall panel.
10. A process for the preparation of an autoclave aerated concrete (AAC) wall panels, the process comprising:
adding a premixed amount of fly ash/pond ash and water to a mixture comprising a return slurry, an ordinary portland cement, a black box admixture, and one or more additives in a concrete mixer for a time period between 5-10 minutes to obtain a wet mixture;
moulding and aerating the wet mixture into a moulding unit maintained at a temperature between 38-45 °C to obtain an aerated concrete cake having a predefined size and shape;
de-moulding and transferring the aerated concrete cake to a cutting section;
cutting the aerated concrete cake in the cutting section, wherein the aerated concrete cake is ordinated for alignment to ensure better autoclaving and easy separation in the cutting section; and
autoclaving the aerated concrete cake in an autoclave chamber at a predetermined temperature, pressure and time to obtain the autoclave aerated concrete (AAC) wall panel.
11. The process as claimed in claim 9, wherein the concrete mixer is preheated to 35-45 °C, by applying a steam at a pressure less than 1.5 bar.
12. The process as claimed in claim 10, wherein the aerated concrete cake is ordinated by tilting, rotation, or both.
13. The process as claimed in claim 10, wherein the temperature and the pressure for the step of autoclaving is maintained between 90-200 °C and 0-15 bar respectively.
14. The process as claimed in claim 10, wherein the predetermined time period for the step of autoclaving is between 0-14 hrs.
15. The process as claimed in claim 10, wherein a peak temperature and peak pressure in an autoclave is maintained between 195-200 °C and 10-15 bar respectively.
16. The process as claimed in claim 15, wherein the peak pressure is maintained between 12-15 bar for the holding period between 4-8 hrs for the overall 14 hrs cycle in the step of autoclaving.
17. The process as claimed in claim 10, wherein the wet density of the return slurry and fly ash/pond ash slurry is between 1400-1600 kg/m3.
18. The process as claimed in claim 10, wherein the autoclave aerated concrete (AAC) wall panel is a non-reinforced autoclave aerated concrete (AAC) wall panel.
19. The process as claimed in claim 18, wherein the non-reinforced autoclave aerated concrete (AAC) wall panel is devoid of steel reinforcements.
20. The process as claimed in claim 18, wherein the compressive strength of the non-reinforced autoclave aerated concrete (AAC) wall panel, tested for cube specimen is between 2-6 N/mm2.
21. The process as claimed in claim 18, wherein the bulk density of the non-reinforced autoclave aerated concrete (AAC) wall panel is between 550-700 kg/m3.
22. The process as claimed in claim 10, wherein a mixing speed of the concrete mixer is greater than 600 rpm.
23. The process as claimed in claim 10, wherein the cutting assembly is a wire cutting assembly.
24. A system for the preparation of an autoclave aerated concrete (AAC) wall panel comprising:
a concrete mixer (201) enabled for the mixing of ingredients of composition for autoclave aerated concrete (AAC) to obtain a wet mixture;
a moulding unit (202) enabled for the aeration and moulding of the wet mixture to obtain an aerated concrete cake of the wet mixture;
a cutting assembly (203) enabled for the cutting of aerated concrete cake; and
an autoclave chamber (204) enabled for the autoclaving the aerated concrete cake to obtain autoclave aerated concrete (AAC) wall panel.
25. The system as claimed in claim 24, wherein the concrete mixer comprises one or more inlets (205, 206) enabled for the addition of feed materials.
26. The system as claimed in claim 24, wherein the cutting assembly is a wire cutting assembly.
27. The system as claimed in claim 24, wherein a mixing speed of the concrete mixer is greater than 600 rpm.
Dated this 10th Day of October 2022

Priyank Gupta
Agent for the Applicant
IN/PA-1454