Title of Invention	A REVOLUTIONARY NO-AGGREGATE CONCRETE MIX AND PROCESS THEREOF
Abstract	A revolutionary No-Aggregate Concrete mix, and process there of: This is an invention in the direction of Sustainable Development by conserving natural materials such as sand and stone, to meet the needs of the future generations. This invention talks about product and process for eliminating fine and coarse aggregate totally and still, making the concrete amenable for structural and non-structural applications with superior engineering properties over the conventional cement concrete. Fly ash, which is added as supplementary cement material in high doses also renders the role of micro-aggregate and, in combination of admixtures and resultant reduction in W/CM factor, renders a near ceramic-like pore refinement to the matrix for phenomenal enhancement of protection to reinforcement, durability and service-life to the structure.

Title of Invention

A REVOLUTIONARY NO-AGGREGATE CONCRETE MIX AND PROCESS THEREOF

Abstract

A revolutionary No-Aggregate Concrete mix, and process there of: This is an invention in the direction of Sustainable Development by conserving natural materials such as sand and stone, to meet the needs of the future generations. This invention talks about product and process for eliminating fine and coarse aggregate totally and still, making the concrete amenable for structural and non-structural applications with superior engineering properties over the conventional cement concrete. Fly ash, which is added as supplementary cement material in high doses also renders the role of micro-aggregate and, in combination of admixtures and resultant reduction in W/CM factor, renders a near ceramic-like pore refinement to the matrix for phenomenal enhancement of protection to reinforcement, durability and service-life to the structure.

Full Text	The present invention relates to a novel and inventive concrete mix suitable for both structural and non-structural application, exhibiting at least two times of strength and phenomenal durability over the conventionally used structural concrete consisting of parallel quantity of Ordinary Portland cement (OPC) or any other blended cement. The conventional concrete comprises of cement along with differently sized fine and coarse aggregate particles added with water to attain required workability. A few optional ingredients are added depending upon the end requirements. In the context of this invention, it is necessary to understand concrete with reference to the role of aggregate, specifically that of coarse aggregate. Certain structural engineers attribute concrete strength totally to coarse aggregate; define the role of sand as filler and that of cement as binder between sand and stone. Thus one perception is that without stone there is no concrete. Many engineers carry this opinion because, despite good mix design, use of poor aggregate results in fall of strength of concrete. Similarly for high strength and high performance concrete selection of high strength coarse aggregate is one of the prerequisites. For this fact, it is improper to attribute strength of concrete to coarse aggregate. But unless and until the multiple stones are held together as a monolithic mass the strength of individual stone does not come into performance. This is where the role of binder (cement + water) and its ability to bind the aggregate together makes a sense. However, there is one interesting observation in this context. If the binding strength is more than aggregate-strength the former decides the strength-grade of concrete, and such strength comes out of cement; if the binding strength is weaker than strength of aggregate, the concrete is bound to fail at 'transition zone' ie., the zone of interface between cementitious matrix and the coarse aggregate, and then, the strength of aggregate does not help to improve the grade strength. One should know that, when cast into a cube by adding water and made into stiff paste, cement alone, without containing any aggregate, does develop a compressive strength of 60 to 80 MPa. However, fine and coarse aggregate are added to cement to serve specific applicationai needs such as: • workability, to facilitate placement and application. • to avoid shrinkage caused by cement paste and render volume stability to concrete. • to contain heat of hydration of cement, for avoiding thermal cracks in concrete. • to moderate/regulate the strengths (10 to 40 MPa) conducive to normal structural needs. • to rationalize the cost of concrete by adding aggregate of lower costs than cost-intensive cement. Strain in concrete, by and large, is attributable to one aspect, the transition zone wherein formation of lengthy and low density crystals of hydrated lime, in the presence of bleed water, develop and cause weak bond between cement paste and stone, leading to flexure-failure. This is the reason why transition zone is identified as the weak link in concrete. Notwithstanding this fact, transition zone yields to hostile issues such as: • accumulation of free lime; • development of micro cracks due to tensile shrinkage owing to differential density between stone and matrix; and • ultimate vulnerability to chemical attacks, more so due to presence of free-lime. Looking at the issues caused by transition zone, if one can avoid coarse aggregate in concrete, without sacrificing the engineering performance, concrete attains new definition, and many durability issues would be addressed in a single stroke by avoiding transition zone. The Inventors focused their research on No-Aggregate Concrete (NAC) out of this durability-agenda, aiming simultaneously to accomplish Sustainable Development through conservation of natural materials. Prior Art Various technologies have been developed for durable concrete through higher strengths, varying the mix, and by adding admixtures wherever required. Despite all this research, concrete remained as less durable material, more so due to its co-existence with steel in reinforced cement concrete (RCC) for predominant applications. Still constant research is in progress to achieve further improvements of the concrete for increasing life span. The most popular use of concrete is in the form of Reinforced Cement Concrete (RCC) wherein embedded structural steel gives ductility to concrete which otherwise is brittle and non-ductile. Such integration of steel to concrete, in the form of RCC, gave a lot of opportunity for the use of concrete with wide applicational scope. But, at the same time, the behaviour of concrete opened up doors to various controversies in durability point of view and diminished service-life of the structure. Development of blended cements in association with mineral admixtures such as fly ash, granulated blast furnace slag, silica fume, rice husk ash and metakaoline addressed the problems to some extent. Another dimension to durability is W/CM factor. Regardless of using high grade cement, by adding water to concrete mix irrationally in the anxiety of workability, the concrete is made too porous or permeable, opening up flood gates for reactions within the concrete matrix, corrosion of steel and ultimately diminished service life. In ancient days high durable concretes were used consisting of low grade cements in contrast to the recent trend of low durable structures with high grade cements. The Bureau of Indian Standards have drawn test procedures vide IS: 516; Mix Designs vide IS: 10262; and Code of Practice vide IS: 456 for conventionally used concrete. All these Standards were prepared keeping the traditionally used fine and coarse aggregate required to prepare the concrete. The concrete mix is designed according to IS: 10262 to achieve the desired strength-class commensurate to the application-need. IS:1199-1959: Methods of sampling and analysis of concrete, defines concrete as "a mixture of cement, water and inert aggregates with or without admixtures". 'IS: 383-1970: Specification for coarse and fine aggregates from natural sources for concrete' provides specification that should comply for aggregate used in the concrete. American Concrete Institute (ACI) defines concrete as "A composite material which consists essentially of a binding medium within which are embedded particles or agents of aggregate; in Portland cement concrete, the binder is a mixture of Portland cement and water". While giving the same definition, American Society for Testing & Materials (ASTM) enlarged the scope of Portland cement to hydraulic cement. The present invention is the outcome of holistic approach to tap material science for an improved performance of concrete. The researchers noticed concrete of low strengths despite using high quality and input of cement. In the process of studying the strain in concrete, the researchers observed two points for majority of the failures. One kind of strain was observed at transition zone ie., between the coarse aggregate particle and cement-sand paste; the second kind of strain was observed within the coarse aggregate particle due to its weak constitution and/or shape. Therefore the Inventors started working towards various alternative methods for minimizing the role of aggregate. Nowadays availability of aggregates is becoming scarce leaving no choice to users in selecting qualitative materials. Therefore the present Inventors started looking at various options including the total substitution of aggregate with other suitable material. Fly ash which is a byproduct from thermal power stations and such other related industries is available in billions of tons. The disposal of fly ash is a big problem and being an ash, not amenable for further processing. Fly ash is used as a partial substitute to cement but its use is limited to 35% by IS Code as it was apprehended that higher dosages of fly ash diminishes the strength of cement/ concrete. The prescribed limit is the result of various studies by the experts in this field. Therefore no skilled person in the art of concrete preparation can think of replacing cement with fly ash more than what is prescribed. The research conducted by Prof Malhotra et al, at Canada Centre for Mineral and Energy Technology (CANMET) labs, Canada, gave room to the development of High Volume Fly ash Concrete (HVFC), containing about 60% fly ash as replacement to OPC, keeping same the role of fine and coarse aggregate. FaL-G, a hydraulic cement composition, which was also invented by the Inventors and patented vide Patent No. 198639 of 13-8-1996, used 50 to 80% fly ash in association with lime and/or OPC to make a cementitious binder for binding the fine aggregate (formortar) and both fine and coarse aggregate (for concrete). Thousands of brick plants are in operation based on the invention of FaL-G. The present invention closely resembles Self Compacting Concrete (SCC) for workability. SSC is defined as a flowing concrete that can be cast into place without the use of vibrators to form a product free of honeycombs (ie., no unfilled space within the form work) and bug holes (ie., no entrapped air voids). This is one type of concrete with high flowability, which is basically developed to meet the concrete application in areas having congested reinforcement and places of inaccessibility where it is difficult to put conventional concrete. Use of fly ash as partial replacement to cement is not uncommon in SCC but it does not contain more than 35% fly ash. Moreover, SCC does not go without fine and coarse aggregates. Use of concrete without coarse aggregate is reported in shotcrete. There are two types of shotcrete. Dry mix shotcrete (gunite) does not include coarse aggregate but fine aggregate is indispensable. It is mixed at the jobsite and water is added immediately just before discharge from nozzle. It renders the compressive strength of 21 MPa as against 40-65 MPa of the present invention. 1 part cement to between 4 to 4-1/2 parts sand is very common. This is covered in ACI506 and IBC Sec 1914. Objects of the invention In their continuous research to maximize the input of fly ash to OPC, the Inventors have added high volumes of fly ash in association with admixtures, whereby the Inventors observed that while the reactive portion of fly ash plays the role of complementary hydration chemistry, the inert portion of fly ash performs the role of micro-aggregate causing to develop an integrated matrix, contributing to phenomenal pore refinement. In the present product of invention, the strengths were found to be at least 2-3 times higher to the conventional structural concrete and durability is at least 50 times. The life span of the embedded steel is also expected to be substantially higher. Therefore: The first object of the invention is to invent a novel and inventive concrete mixture capable of developing higher strengths with longer service-life. The second object of the invention is to invent a novel and inventive concrete mix free from transition zone, whereof the use of conventional aggregate is totally avoided. The third object of the invention is to use least quantity of water in the concrete mix so as to achieve pore refinement, absolute impermeability and durability enhancement. The fourth object of the invention is to encourage effective and massive use of fly ash which otherwise is causing problem of disposal and environmental hazard. The fifth object of the invention is to use NAC as cast in-situ walls for rapid construction. The sixth object of the invention is to cast high strength walls with the concrete mix of the present invention so that the wall itself performs the engineering functionality of column and beams. The seventh object of the invention is to encourage precast component production or facilitate prefab construction practices. The eighth object of the invention is to develop a process of preparing the novel and inventive concrete mix capable of self leveling and self-compacting. The ninth object of the invention is to achieve cost-effective construction. Any other objects which might not have been mentioned here need not to be treated as mentioned but are treated to be included herein. Detailed description of the invention This invention is the outcome of research for manufacturing concrete free from transition zone, ie., by avoiding the role of fine and coarse aggregate, but still achieving a product that serves all the structural engineering criteria such as compressive strength, flexural strength, bond strength and dimensional stability. For this purpose, the process identified mineral admixtures such as fly ash, which renders the role of micro-aggregate, in addition to rendering its contribution through pozzolanic chemistry for durability enhancement. NAC composition: But for the use of admixtures and resultant properties, this invention is the extension of FaL-G wherein FaL-G was invented as the cementitious product, as partial or total replacement to OPC to be used in composition with fine and/or coarse aggregate, whereas in the present invention the role of FaL-G is redefined as concrete in association with admixtures. As ratios of cement to aggregate in conventional concrete, which is otherwise called as control concrete, decide the strength-grade, the ratio of OPC to fly ash+mineral admixtures decides the strength-grade in the case of NAC, which do vary in accordance to the target strength. The following ingredients have been used as the typical mix of NAC for this study: The mix attains pour-state despite very low W/CM factor, owing to the admixture(s) (Ref: Photo 1). The Inventors have cast a 10-ft dia dome and 10 x 6 ft. wall using NAC, in order to perceive applicational implications at field level (Ref: Photo 2 & 3). Engineering data: The study aimed at establishing the basic structural engineering data and compare the same with control concrete. For this purpose 10 cm cubes, cylinders (100 x 200 and 150 x 300 mm) and beams (100 x 100 x 500 mm) were cast. For the purpose of bond strength, 12 mm ribbed bars were embedded in 10 cm cubes, and subjected for curing in the lines of control concrete. Cylinders were used to study the chloride permeability vide ASTM C: 1202 in order to understand the microstructure of the product for its durability. The data obtained on various specimens are given in the table below. Looking at the issues caused by transition zone, if one can avoid coarse aggregate in concrete, without sacrificing the performance requirements, concrete attains new definition devoid of transition zone, and many durability issues would be addressed in one stroke. NAC has been developed out of this durability-agenda, aiming simultaneously to accomplish Sustainable Development, by replacing natural aggregate and using industrial byproducts to supplement the performance. As there is no use of aggregate, the wet mix of NAC looks like viscous fluid, and thus inherently exhibits a good flowing property. This is the reason why vibration is not necessary, unlike in the conventional concrete mix, for compaction. The permeability tests reveal that the cured concrete mix is more compact and hence less permeable than any conventional concrete with the best of the vibration. Despite having more compaction the matrix of the product is lighter than the conventional concrete of similar design-strength by about 25%. By virtue of its flowability devoid of coarse constituents, it is one of the ideal mixes for casting products of detailed profiles, as done with Plaster of Paris (POP). Advantages of the Invention The invention has resulted in the following main features: • Reduction in weight: The density of NAC is around 1800 kg/cu.m as against 2400-2500 kg/ cu.m of conventional concrete. • Higher Strength: 28-day compressive strength of NAC is 40-60 MPa, higher than that of conventional concrete with same level of OPC. • Bond strength is higher by over 3 times to the codal requirements. • A mix that has self leveling and self compaction abilities at lower water to cementitious material (W/CM) factor. • Due to lower W/CM factor, the resultant product is densified with least porosity resembling close to ceramic-like pore-refinement, as established by permeability test in the engineering data above. We claim 1) A novel and inventive concrete mix (NAC) comprising fly ash, OPC, chemical admixture(s), mineral admixture(s) water and optionally other known ingredients. 2) A novel and inventive concrete mix as claimed in claim 1 wherein fly ash is present in between 50 per cent to 95 percent of the total dry weight [excluding water] of the concrete mix. 3) A novel and inventive concrete mix as claimed in claim 1 wherein fly ash is substituted totally or partially by pond ash, mond ash or any other forms of ash generated out of coal combustion, directly or through specific treatment. 4) A novel and inventive concrete mix as claimed in claims 1 and 2 wherein the water content does not exceed 25 per cent of the total weight of the concrete mix. 5) A novel and inventive concrete mix as claimed in any of the preceding claims wherein the chemical and/or mineral admixtures present in between 0.2 per cent to 35 per cent of the total dry weight of the concrete mix. 6) A novel and inventive concrete mix as claimed in any of the previous claims wherein the cement content is adjusted to 100 weight percent of the total dry weight [excluding water content] of the concrete mix. 7) A novel and inventive concrete mix as claimed in any of the preceding claims wherein the chemical admixture is selected preferably out of naphthalene base, melamine base, polycarboxylate base or a combination there of, without restricting the use of other admixtures which contribute to water reduction and flowability. 8) A novel and inventive concrete mix as claimed in any of the preceding claims wherein the known mineral admixture is used singularly or a combination thereof 9) A novel and inventive concrete mix as claimed in any of the preceding claims where in organic, polymer and/or metallic fibers are used to counteract brittleness on account of higher strengths. 10) A novel and inventive concrete mix as claimed in any of the preceding claims which can be used both for structural and non-structural applications ie., as reinforced concrete and plain concrete. 11) A process for the preparation of a novel and inventive concrete mix as claimed in any of the preceding claims comprising the steps of; homogenously mixing OPC, chemical and mineral admixture with fly ash in a suitable mixer followed by mixing of water of suitable quantity in any conventional way. 12) A process for the preparation of NAC wherein all the ingredients are mixed together in a roller mixer or in any other known method that ensures homogeneity. 13) A process for the preparation of NAC as claimed in any of the preceding claims wherein the water cement ratio is generally maintained in between 0.1 to 0.25. 14) A concrete mix [NAC] of higher workability at least w/cm factor with superior compressive strength, high order of impermeability, higher durability and service life even in the form RCC, and a process for preparing the same is as herein described and exemplified. 15) A concrete mix of higher workability which is amenable to be used for casting products of high detailing, in the lines of POP.

Full Text

The present invention relates to a novel and inventive concrete mix suitable for both structural and non-structural application, exhibiting at least two times of strength and phenomenal durability over the conventionally used structural concrete consisting of parallel quantity of Ordinary Portland cement (OPC) or any other blended cement.

The conventional concrete comprises of cement along with differently sized fine and coarse aggregate particles added with water to attain required workability. A few optional ingredients are added depending upon the end requirements.

In the context of this invention, it is necessary to understand concrete with reference to the role of aggregate, specifically that of coarse aggregate. Certain structural engineers attribute concrete strength totally to coarse aggregate; define the role of sand as filler and that of cement as binder between sand and stone. Thus one perception is that without stone there is no concrete. Many engineers carry this opinion because, despite good mix design, use of poor aggregate results in fall of strength of concrete. Similarly for high strength and high performance concrete selection of high strength coarse aggregate is one of the prerequisites. For this fact, it is improper to attribute strength of concrete to coarse aggregate. But unless and until the multiple stones are held together as a monolithic mass the strength of individual stone does not come into performance. This is where the role of binder (cement + water) and its ability to bind the aggregate together makes a sense.

However, there is one interesting observation in this context. If the binding strength is more than aggregate-strength the former decides the strength-grade of concrete, and such strength comes out of cement; if the binding strength is weaker than strength of aggregate, the concrete is bound to fail at 'transition zone' ie., the zone of interface between cementitious matrix and the coarse aggregate, and then, the strength of aggregate does not help to improve the grade strength.

One should know that, when cast into a cube by adding water and made into stiff paste, cement alone, without containing any aggregate, does develop a compressive strength of 60 to 80 MPa. However, fine and coarse aggregate are added to cement to serve specific applicationai needs such as:

• workability, to facilitate placement and application.
• to avoid shrinkage caused by cement paste and render volume stability to concrete.
• to contain heat of hydration of cement, for avoiding thermal cracks in concrete.
• to moderate/regulate the strengths (10 to 40 MPa) conducive to normal structural needs.
• to rationalize the cost of concrete by adding aggregate of lower costs than cost-intensive cement.

Strain in concrete, by and large, is attributable to one aspect, the transition zone wherein formation of lengthy and low density crystals of hydrated lime, in the presence of bleed water, develop and cause weak bond between cement paste and stone, leading to flexure-failure. This is the reason why transition zone is identified as the weak link in concrete.

Notwithstanding this fact, transition zone yields to hostile issues such as:
• accumulation of free lime;
• development of micro cracks due to tensile shrinkage owing to differential density between stone and matrix; and

• ultimate vulnerability to chemical attacks, more so due to presence of free-lime.
Looking at the issues caused by transition zone, if one can avoid coarse aggregate in concrete, without sacrificing the engineering performance, concrete attains new definition, and many durability issues would be addressed in a single stroke by avoiding transition zone. The Inventors focused their research on No-Aggregate Concrete (NAC) out of this durability-agenda, aiming simultaneously to accomplish Sustainable Development through conservation of natural materials.

Prior Art

Various technologies have been developed for durable concrete through higher strengths, varying the mix, and by adding admixtures wherever required. Despite all this research, concrete remained as less durable material, more so due to its co-existence with steel in reinforced cement concrete (RCC) for predominant applications. Still constant research is in progress to achieve further improvements of the concrete for increasing life span.

The most popular use of concrete is in the form of Reinforced Cement Concrete (RCC) wherein embedded structural steel gives ductility to concrete which otherwise is brittle and non-ductile. Such integration of steel to concrete, in the form of RCC, gave a lot of opportunity for the use of concrete with wide applicational scope. But, at the same time, the behaviour of concrete opened up doors to various controversies in durability point of view and diminished service-life of the structure. Development of blended cements in association with mineral admixtures such as fly ash, granulated blast furnace slag, silica fume, rice husk ash and metakaoline addressed the problems to some extent.

Another dimension to durability is W/CM factor. Regardless of using high grade cement, by adding water to concrete mix irrationally in the anxiety of workability, the concrete is made too porous or permeable, opening up flood gates for reactions within the concrete matrix, corrosion of steel and ultimately diminished service life. In ancient days high durable concretes were used consisting of low grade cements in contrast to the recent trend of low durable structures with high grade cements.

The Bureau of Indian Standards have drawn test procedures vide IS: 516; Mix Designs vide IS: 10262; and Code of Practice vide IS: 456 for conventionally used concrete. All these Standards were prepared keeping the traditionally used fine and coarse aggregate required to prepare the concrete. The concrete mix is designed according to IS: 10262 to achieve the desired strength-class commensurate to the application-need.

IS:1199-1959: Methods of sampling and analysis of concrete, defines concrete as "a mixture of cement, water and inert aggregates with or without admixtures". 'IS: 383-1970: Specification for coarse and fine aggregates from natural sources for concrete' provides specification that should comply for aggregate used in the concrete.

American Concrete Institute (ACI) defines concrete as "A composite material which consists essentially of a binding medium within which are embedded particles or agents of aggregate; in Portland cement concrete, the binder is a mixture of Portland cement and water". While giving the same definition, American Society for Testing & Materials (ASTM) enlarged the scope of Portland cement to hydraulic cement.

The present invention is the outcome of holistic approach to tap material science for an improved performance of concrete. The researchers noticed concrete of low strengths despite using high quality and input of cement. In the process of studying the strain in concrete, the researchers observed two points for majority of the failures. One kind of strain was observed at transition zone ie., between the coarse aggregate particle and cement-sand paste; the second kind of strain was observed within the coarse aggregate particle due to its weak constitution and/or shape.

Therefore the Inventors started working towards various alternative methods for minimizing the role of aggregate. Nowadays availability of aggregates is becoming scarce leaving no choice to users in selecting qualitative materials. Therefore the present Inventors started looking at various options including the total substitution of aggregate with other suitable material.

Fly ash which is a byproduct from thermal power stations and such other related industries is available in billions of tons. The disposal of fly ash is a big problem and being an ash, not amenable for further processing. Fly ash is used as a partial substitute to cement but its use is limited to 35% by IS Code as it was apprehended that higher dosages of fly ash diminishes the strength of cement/ concrete. The prescribed limit is the result of various studies by the experts in this field. Therefore no skilled person in the art of concrete preparation can think of replacing cement with fly ash more than what is prescribed.

The research conducted by Prof Malhotra et al, at Canada Centre for Mineral and Energy Technology (CANMET) labs, Canada, gave room to the development of High Volume Fly ash Concrete (HVFC), containing about 60% fly ash as replacement to OPC, keeping same the role of fine and coarse aggregate.

FaL-G, a hydraulic cement composition, which was also invented by the Inventors and patented vide Patent No. 198639 of 13-8-1996, used 50 to 80% fly ash in association with lime and/or OPC to make a cementitious binder for binding the fine aggregate (formortar) and both fine and coarse aggregate (for concrete). Thousands of brick plants are in operation based on the invention of FaL-G.

The present invention closely resembles Self Compacting Concrete (SCC) for workability. SSC is defined as a flowing concrete that can be cast into place without the use of vibrators to form a product free of honeycombs (ie., no unfilled space within the form work) and bug holes (ie., no entrapped air voids). This is one type of concrete with high flowability, which is basically developed to meet the concrete application in areas having congested reinforcement and places of inaccessibility where it is difficult to put conventional concrete. Use of fly ash as partial replacement to cement is not uncommon in SCC but it does not contain more than 35% fly ash. Moreover, SCC does not go without fine and coarse aggregates.

Use of concrete without coarse aggregate is reported in shotcrete. There are two types of shotcrete. Dry mix shotcrete (gunite) does not include coarse aggregate but fine aggregate is indispensable. It is mixed at the jobsite and water is added immediately just before discharge from nozzle. It renders the compressive strength of 21 MPa as against 40-65 MPa of the present invention. 1 part cement to between 4 to 4-1/2 parts sand is very common. This is covered in ACI506 and IBC Sec 1914.

Objects of the invention

In their continuous research to maximize the input of fly ash to OPC, the Inventors have added high volumes of fly ash in association with admixtures, whereby the Inventors observed that while the reactive portion of fly ash plays the role of complementary hydration chemistry, the inert portion of fly ash performs the role of micro-aggregate causing to develop an integrated matrix, contributing to phenomenal pore refinement. In the present product of invention, the strengths were found to be at least 2-3 times higher to the conventional structural concrete and durability is at least 50 times. The life span of the embedded steel is also expected to be substantially higher. Therefore:

The first object of the invention is to invent a novel and inventive concrete mixture capable of developing higher strengths with longer service-life.

The second object of the invention is to invent a novel and inventive concrete mix free from transition zone, whereof the use of conventional aggregate is totally avoided.

The third object of the invention is to use least quantity of water in the concrete mix so as to achieve pore refinement, absolute impermeability and durability enhancement.

The fourth object of the invention is to encourage effective and massive use of fly ash which otherwise is causing problem of disposal and environmental hazard.

The fifth object of the invention is to use NAC as cast in-situ walls for rapid construction.

The sixth object of the invention is to cast high strength walls with the concrete mix of the present invention so that the wall itself performs the engineering functionality of column and beams.

The seventh object of the invention is to encourage precast component production or facilitate prefab construction practices.

The eighth object of the invention is to develop a process of preparing the novel and inventive concrete mix capable of self leveling and self-compacting.

The ninth object of the invention is to achieve cost-effective construction.

Any other objects which might not have been mentioned here need not to be treated as mentioned but are treated to be included herein.

Detailed description of the invention

This invention is the outcome of research for manufacturing concrete free from transition zone, ie., by avoiding the role of fine and coarse aggregate, but still achieving a product that serves all the structural engineering criteria such as compressive strength, flexural strength, bond strength and dimensional stability.

For this purpose, the process identified mineral admixtures such as fly ash, which renders the role of micro-aggregate, in addition to rendering its contribution through pozzolanic chemistry for durability enhancement.

NAC composition:

But for the use of admixtures and resultant properties, this invention is the extension of FaL-G wherein FaL-G was invented as the cementitious product, as partial or total replacement to OPC to be used in composition with fine and/or coarse aggregate, whereas in the present invention the role of FaL-G is redefined as concrete in association with admixtures.

As ratios of cement to aggregate in conventional concrete, which is otherwise called as control concrete, decide the strength-grade, the ratio of OPC to fly ash+mineral admixtures decides the strength-grade in the case of NAC, which do vary in accordance to the target strength.

The following ingredients have been used as the typical mix of NAC for this study:

The mix attains pour-state despite very low W/CM factor, owing to the admixture(s) (Ref: Photo 1). The Inventors have cast a 10-ft dia dome and 10 x 6 ft. wall using NAC, in order to perceive applicational implications at field level (Ref: Photo 2 & 3).

Engineering data:

The study aimed at establishing the basic structural engineering data and compare the same with control concrete. For this purpose 10 cm cubes, cylinders (100 x 200 and 150 x 300 mm) and beams (100 x 100 x 500 mm) were cast. For the purpose of bond strength, 12 mm ribbed bars were embedded in 10 cm cubes, and subjected for curing in the lines of control concrete. Cylinders were used to study the chloride permeability vide ASTM C: 1202 in order to understand the microstructure of the product for its durability. The data obtained on various specimens are given in the table below.

Looking at the issues caused by transition zone, if one can avoid coarse aggregate in concrete, without sacrificing the performance requirements, concrete attains new definition devoid of transition zone, and many durability issues would be addressed in one stroke. NAC has been developed out of this durability-agenda, aiming simultaneously to accomplish Sustainable Development, by replacing natural aggregate and using industrial byproducts to supplement the performance.

As there is no use of aggregate, the wet mix of NAC looks like viscous fluid, and thus inherently exhibits a good flowing property. This is the reason why vibration is not
necessary, unlike in the conventional concrete mix, for compaction. The permeability tests reveal that the cured concrete mix is more compact and hence less permeable than any conventional concrete with the best of the vibration. Despite having more compaction the matrix of the product is lighter than the conventional concrete of similar design-strength by about 25%.

By virtue of its flowability devoid of coarse constituents, it is one of the ideal mixes for casting products of detailed profiles, as done with Plaster of Paris (POP).

Advantages of the Invention

The invention has resulted in the following main features:

• Reduction in weight: The density of NAC is around 1800 kg/cu.m as against 2400-2500 kg/ cu.m of conventional concrete.
• Higher Strength: 28-day compressive strength of NAC is 40-60 MPa, higher than that of conventional concrete with same level of OPC.
• Bond strength is higher by over 3 times to the codal requirements.
• A mix that has self leveling and self compaction abilities at lower water to cementitious material (W/CM) factor.
• Due to lower W/CM factor, the resultant product is densified with least porosity resembling close to ceramic-like pore-refinement, as established by permeability test in the engineering data above.

We claim
1) A novel and inventive concrete mix (NAC) comprising fly ash, OPC, chemical admixture(s), mineral admixture(s) water and optionally other known ingredients.

2) A novel and inventive concrete mix as claimed in claim 1 wherein fly ash is present in between 50 per cent to 95 percent of the total dry weight [excluding water] of the concrete mix.

3) A novel and inventive concrete mix as claimed in claim 1 wherein fly ash is substituted totally or partially by pond ash, mond ash or any other forms of ash generated out of coal combustion, directly or through specific treatment.

4) A novel and inventive concrete mix as claimed in claims 1 and 2 wherein the water content does not exceed 25 per cent of the total weight of the concrete mix.

5) A novel and inventive concrete mix as claimed in any of the preceding claims wherein the chemical and/or mineral admixtures present in between 0.2 per cent to 35 per cent of the total dry weight of the concrete mix.

6) A novel and inventive concrete mix as claimed in any of the previous claims wherein the cement content is adjusted to 100 weight percent of the total dry weight [excluding water content] of the concrete mix.

7) A novel and inventive concrete mix as claimed in any of the preceding claims wherein the chemical admixture is selected preferably out of naphthalene base, melamine base, polycarboxylate base or a combination there of, without restricting the use of other admixtures which contribute to water reduction and flowability.

8) A novel and inventive concrete mix as claimed in any of the preceding claims wherein the known mineral admixture is used singularly or a combination thereof

9) A novel and inventive concrete mix as claimed in any of the preceding claims where in organic, polymer and/or metallic fibers are used to counteract brittleness on account of higher strengths.

10) A novel and inventive concrete mix as claimed in any of the preceding claims which can be used both for structural and non-structural applications ie., as reinforced concrete and plain concrete.

11) A process for the preparation of a novel and inventive concrete mix as claimed in any of the preceding claims comprising the steps of; homogenously mixing OPC, chemical and mineral admixture with fly ash in a suitable mixer followed by mixing of water of suitable quantity in any conventional way.

12) A process for the preparation of NAC wherein all the ingredients are mixed together in a roller mixer or in any other known method that ensures homogeneity.

13) A process for the preparation of NAC as claimed in any of the preceding claims wherein the water cement ratio is generally maintained in between 0.1 to 0.25.

14) A concrete mix [NAC] of higher workability at least w/cm factor with superior compressive strength, high order of impermeability, higher durability and service life even in the form RCC, and a process for preparing the same is as herein described and exemplified.

15) A concrete mix of higher workability which is amenable to be used for casting products of high detailing, in the lines of POP.

Documents:

http://ipindiaonline.gov.in/patentsearch/GrantedSearch/viewdoc.aspx?id=ki6YKpSHA/UH6i1NC31jmw==&loc=egcICQiyoj82NGgGrC5ChA==

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Patent Number

279460

Indian Patent Application Number

857/CHE/2010

PG Journal Number

04/2017

Publication Date

27-Jan-2017

Grant Date

23-Jan-2017

Date of Filing

29-Mar-2010

Name of Patentee

NATERI KALIDAS

Applicant Address

32-10-55, SHRI VENKATESWARA COLONY, SHEILA NAGAR, VISAKHAPATNAM - 530 012.

Inventors:

#	Inventor's Name	Inventor's Address
1	DR. NATERI BHANUMATHIDAS	32-10-55, SHRI VENKATESWARA COLONY, SHEILA NAGAR, VISAKHAPATNAM - 530 012.
2	NATERI KALIDAS	32-10-55, SHRI VENKATESWARA COLONY, SHEILA NAGAR, VISAKHAPATNAM - 530 012.

PCT International Classification Number

C04B 28/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA