FORM-2
THE PATENT ACT,1970
(39 OF 1970)
AND
THE PATENT RULES, 2003
(As Amended)
COMPLETE SPECIFICATION (See section 10;rule 13)
"IMPROVED CONCRETE COMPOSITE WITH REDUCED PLASTIC SHRINKAGE CRACKING"
Ultratech Cement Limited, a corporation organized and existing under the laws of India, of ‘B’ wing, 2nd Floor, Ahura Centre, Mahakali Caves Road, Andheri (East), Mumbai-400093, Maharashtra, India.
The following specification particularly describes the invention and the manner in which it is to be performed:

Field of the invention:
The present invention relates to the improved concrete composite with reduced plastic shrinkage cracking. The invention further provides the process of manufacturing said improved concrete composite.
Background of the invention:
Plastic Shrinkage Cracks are defined as shrinkage cracks that appear before cement paste, mortar, grout, or concrete sets. They appear on the surface of fresh concrete soon after it is placed and while it is still plastic. These cracks appear mostly on horizontal surfaces. They are usually parallel to each other on the order of 1 to 3 feet apart, relatively shallow, and generally do not intersect the perimeter of the slab. Plastic shrinkage cracking is highly likely to occur when high evaporation rates cause the concrete surface to dry out before it has set.
Plastic shrinkage cracking is important to be taken care of as plastic shrinkage cracks are caused by a rapid loss of water from the surface of the concrete before it has been set. The critical condition exists when the rate of evaporation of surface moisture exceeds the rate at which rising bleed water can replace it. Water receding below the concrete surface forms menisci between the fine particles of cement and aggregate causing a tensile force to develop in the surface layers. If the concrete surface has started to set and has developed sufficient tensile strength to resist the tensile forces, cracks do not form. If the surface dries very rapidly, the concrete may still be plastic, and cracks do not develop at that time; but plastic cracks will surely form as soon as the concrete stiffens a little more.
Conditions that cause high rate of evaporation from the concrete surface, and thereby increases the possibility of plastic shrinkage cracking, include:
• Wind velocity more than 5 mph
• Low relative humidity
• High ambient and/or concrete temperatures
Small changes in any one of these factors can significantly change the rate of evaporation. Concrete mixtures with an inherent reduced rate of bleeding or quantity of bleed water are susceptible to plastic shrinkage cracking even when evaporation rates are low. Factors that reduce the rate or quantity of bleeding include high cementitious materials content, high fines content, reduced water content, entrained air, high concrete temperature, and thinner sections.

Concrete containing silica fume requires particular attention to avoid surface drying during placement.
Any factor that delays setting, increases the possibility of plastic shrinkage cracking. A delayed setting can result from a combination of one or more factors such as cool weather, cool subgrades, high water contents, lower cement contents, retarders, some water reducers, and supplementary cementing materials.
Plastic shrinkage cracking rarely impairs the strength of a concrete element. However, it has a dramatic impact on the appearance of the concrete; where it penetrates full depth, it may lead to water penetration problems.
Common approaches to control plastic shrinkage cracking are as follows:
1) Dampen the subgrade and formwork, ensuring that any excess water is removed prior to placing concrete.
2) In hot weather, lower the temperature of the fresh concrete by using chilled mixing water or replacing some of this water with crushed ice.
3) Protect concrete surfaces from drying out. Erect wind breaks to reduce wind velocity over the concrete surface. This is often impractical but can be accomplished when frames or walls are erected prior to a floor being placed.
4) Commence the curing regime promptly after finishing and continue for the specified period.
5) The use of sufficient proportions of synthetic fibres in concrete can provide improved control of plastic cracking.
6) Sprinkle water in the surrounding of the construction site to increase the relative humidity.
However, said approaches known in the art are cumbersome, labor intensive and expensive. Therefore, there is a need in the art to develop an improved concrete having reduced plastic shrinkage cracking.
Object of the invention:
The object of the present invention is to provide an improved concrete composite having reduced plastic shrinkage cracking.

Further object of the present invention is to provide a low cost and less labor-intensive concrete having reduced plastic shrinkage cracking.
Further, object of the present invention is to provide a method of preparing the improved concrete composite having reduced plastic shrinkage cracking.
Summary of the invention:
In order to achieve the afore-said objectives, the present invention provides an improved concrete composite comprising mixture of hydraulic cement, aggregates, and water, with or without admixtures, polymer fibers, and/or other cementitious materials.
As per the first aspect of the invention, the present invention relates to an improved concrete composite comprising mixture of 5-20% by weight of hydraulic cement, 65-80% by weight of aggregates, and 6-8% by weight of water, with or without 0.06-0.3% by weight of admixtures, 0.01-0.1% by weight of polymer fibers, and/or other 5-12% by weight of cementitious materials.
As per one embodiment, the polymer fibers are selected from the group consisting of waste fishing net fibers, rubber tyres and mixture thereof.
As per another embodiment, the hydraulic cement is selected from the group consisting of OPC, PPC, PSC and mixture thereof.
As per another embodiment, the aggregates are selected from the group consisting of Basalt, limestone, sandstone, and mixture thereof.
As per another embodiment, the admixtures are selected from the group consisting of Naphthalene, Polycarboxylic ether and mixture thereof.
As per another embodiment, the cementitious materials are selected from the group consisting of fly ash, slag, silica fumes and mixture thereof.

Detailed Description of the invention:
The following description is provided to assist in a comprehensive understanding of exemplary embodiments of the invention. It includes various specific details to assist the understanding, but these are to be regarded as merely exemplary.
The embodiments of the present subject matter are described in detail with reference to the accompanying drawings. However, the present subject matter is not limited to these embodiments which are only provided to explain more clearly the present subject matter to a person skilled in the art of the present disclosure. In the accompanying drawings, like reference numerals are used to indicate like components.
Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope of the invention. In addition, description of well-known functions / constructions is omitted for clarity and consciousness.
Those skilled in the art will be aware that the invention described herein is subject to variations and modifications, other than those specifically described. It is to be understood that the invention described herein includes all such variations and modifications. The invention also includes all such steps, features, compositions, and compounds referred to or indicated in this specification, individually or collectively, and any and all combinations of any two or more of said steps or features.
The present invention is not to be limited in scope by the specific embodiments described herein, which is intended for the purposes of exemplification only. Functionally equivalent products, compositions, and methods are clearly within the scope of the invention, as described herein.
For convenience, before further description of the present invention, certain terms employed in this specification, examples and appended claims are collected here. These definitions should be read considering 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 a person of ordinary skill in the art.

Features that are described and/or illustrated with respect to one embodiment may be used in the same way or in a similar way or more other embodiment and/or in combination with or instead of the features of other embodiments.
As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless expressly stated otherwise.
It will be further understood that the terms “includes”, “comprises”, “including” and/or “comprising” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
The terms “comprise” and “comprising” are used in the inclusive, open sense, meaning that additional elements may be included. It is not intended to be construed as “consists of only”. Throughout this specification unless the context requires otherwise the word “comprise”, and variations such as “comprises” and “comprising”, will be understood to imply the inclusion of a stated element or step or group of element or steps but not the exclusion of any other element or step or group of element or steps.
The term “including” is used to mean “included but not limited to”. “Including” and “including but not limited to” are used interchangeably.
It will be understood that when an element is referred to as being “attached” or “connected” or “coupled” or “mounted” to another element, it can be directly attached or connected or coupled to the other element or intervening elements may be present.
As used herein, the term “and/or” includes any and all combinations and arrangements of one or more of the associated listed items.
The specification may refer to “an”, “one”, “different” or “some” embodiment(s) in several locations. This does not necessarily imply that each such reference is to the same embodiment(s), or that the feature only applies to a single embodiment. Single features of different embodiments may also be combined to provide other embodiments.

Unless otherwise indicated, all numbers expressing quantities of ingredients, properties such as reaction conditions, and so forth used in the specification and claims are to be understood as being modified in all instances by the term "about". Accordingly, unless indicated to the contrary, the numerical parameters set forth in this specification and claims are approximations that can vary depending upon the desired properties sought to be obtained by the presently disclosed subject matter.
The figures depict a simplified structure only showing some elements and functional entities, all being logical units whose implementation may differ from what is shown.
The present invention relates to the development of an improved concrete composite material that comprises a mixture of hydraulic cement, aggregates, and water, with or without admixtures, polymer fibers, or other cementitious materials.
Concrete is a mixture of cement paste and aggregates, or rocks. The paste, composed of hydraulic cement and water, coats the surface of the fine (small) and coarse (larger) aggregates. Through a chemical reaction called hydration, the paste hardens and gains strength to form the rock-like mass known as concrete. Generally, concrete is measured in volume and the unit is cubic meter (cum).
As per the first aspect of the invention, the present invention relates to an improved concrete composite comprising mixture of 5-20% by weight of hydraulic cement, 65-80% by weight of aggregates, and 6-8% by weight of water, with or without 0.06-0.3% by weight of admixtures, 0.01-0.1% by weight of polymer fibers, and/or other 5-12% by weight of cementitious materials.
As per one embodiment, the polymer fibers are selected from the group consisting of waste fishing net fibers, rubber tyres and mixture thereof.
As per another embodiment, the hydraulic cement is selected from the group consisting of OPC, PPC, PSC and mixture thereof.
As per another embodiment, the aggregates are selected from the group consisting of Basalt, limestone, sandstone and mixture thereof.
As per another embodiment, the admixtures are selected from the group consisting of Naphthalene, Polycarboxylic ether and mixture thereof.

As per another embodiment, the cementitious materials are selected from the group consisting of fly ash, slag, silica fumes and mixture thereof.
Hydraulic Cement: A binding material that sets and hardens by chemical reaction with water and is capable of doing so underwater. For example, Portland cement and slag cement are hydraulic cement. Cement is a finely milled mineral powder, usually grey in color. The most important raw materials to produce cement are limestone, clay, and marl. Mixed with water, cement serves as an adhesive to bind sand, gravel, and hard rock in concrete.
Supplementary Cementitious Materials: Supplementary cementing materials (SCMs) contribute to the properties of hardened concrete through hydraulic or pozzolanic activity. Typical examples are fly ashes, granulated blast-furnace slag, and silica fume. These can be used individually with hydraulic cement or in different combinations. Supplementary cementing materials are often added to concrete to make concrete mixtures more economical, reduce permeability, increase strength, or influence other concrete properties.
Aggregates: Aggregates are inert granular materials such as sand, gravel, or crushed stone that, along with water and portland cement, are essential ingredients in concrete. Aggregates, which account for 60 to 75 per cent of the total volume of concrete, are divided into two distinct categories--fine and coarse. Fine aggregates generally consist of natural sand or crushed stone with most particles passing through a 4.75 mm sieve. Coarse aggregates are any particles greater than 4.75 mm.
Water: Various Standards recommend to use of potable water for making concrete. The amount of water in concrete controls many fresh and hardened properties in concrete including workability, compressive strengths, permeability and water tightness, durability and weathering, drying shrinkage and potential for cracking. For these reasons, limiting and controlling the amount of water in the concrete is important for both constructability and service life.
Admixture: A material other than water, aggregates, and hydraulic cement and additives like pozzolana or slag and fibre reinforcement used as an ingredient of concrete or mortar and added to the batch immediately before or during its mixing to modify one or more of the properties of concrete in the plastic or hardened state. Producers use admixtures primarily to reduce the cost of concrete construction; to modify the properties of hardened concrete; to ensure the quality of

concrete during mixing, transporting, placing, and curing; and to overcome certain emergencies during concrete operations. Generally following are the types of admixtures
a) Accelerating admixtures,
b) Retarding admixtures,
c) Water-reducing admixtures,
d) Air-entraining admixtures,
e) Super plasticizing admixtures.
Waste fishing net fibers: The nylon and plastic waste materials which are in the shape of long wires, threads or nets are collected, cleaned, and then chopped or shredded to form into thin and small fibers ranging from 3mm to 20mm in length. A pre-measured quantity of these chopped fibers (called INF here onwards) ranging from 500 grams to 3000 grams is weighed and kept in separate batches. During the manufacturing of concrete, the premeasured quantity of INF is added to every 1 cubic meter of concrete alongside other ingredients. The manual or mechanical process is used to spread the INF uniformly into the concrete mix. The concrete mix is then mixed inside a pan mixer, drum mixer or a twin shaft mixer.
Currently used synthetic fibers are produced from processing glass or polypropylene or polyester like materials in expensive manufacturing setup. Then these fibers are transported and delivered to various sites and concrete plants for use in concrete. Hence plastic shrinkage crack prevention in concrete using synthetic fibers is expensive. By converting waste nets, wires and threads into fiber-like material, to impart equivalent properties to concrete will make the solution very inexpensive and eco-friendly. It will also solve the problem of accumulation of non-biodegradable waste like fishing nets and nylon threads and hence lead to sustainability of sea life as well as landfills.
A typical concrete mix contains the following composition.

Material Qty Kg/Cum
Cement 225
Fly Ash 75
Fine Aggregates 825
Coarse Aggregates 1118
Water 165
Admixture (Water reducer) 2.1

The concrete composition mix according to the invention contains the following composition.

Material Qty Kg/Cum
Cement 225
Fly Ash 75
Fine Aggregates 825
Coarse Aggregates 1118
Water 165
Admixture (Water reducer) 2.1
Waste Fishing Net Fibers 1.5
Following are the findings which show that the incorporation of waste fishing nets & tyre waste has the following advantages.
a. Improvement in elastic permeability,
b. Making of lightweight concrete or mortar,
c. Improvement in lateral tensile strength and hence fracture resistance.
d. Improvement in flexural strength
e. Usability of different types of waste fibres as fibres for concrete.
f. Usage of rubber as an aggregate and finding the effects of workability, setting time,
bleeding, density, strength, impact energy, impact load, toughness, ductility, shrinkage, abrasion
resistance, freeze/thaw resistance, fire resistance, thermal insulation, carbonation resistance,
corrosion resistance, water absorption, porosity, chloride ion penetration, resistance to
aggressive environmental, energy absorption, sound absorption, electrical resistance and
cracking resistance of rubberized mortar/concrete.
g. Improvement in fresh concrete properties & strength properties of virgin nylon and
polypropylene fiber reinforced concretes.
h. Ductile behavior of concrete after initial crack.
i. Reduction in cracking by using waste rubber aggregates.
j. Improvement in hardened concrete cracking resistance.
However, the inventors have surprisingly and unexpectedly found that there is improvement in the plastic shrinkage cracking characteristics of the concrete composite composition.
According to the second aspect the present invention provides the process of preparing the concrete composite composition. The method comprises the steps of:

The fibers are processed by washing, sizing and separation. Washing is done using potable water to remove any debris accumulated on the nets or tyres. After that chopping is done mechanically in a suitable machine to reduce the length to the required size. Lumps and knots are manually separated before packaging the fibers. Cleaned and processed fibres are pre-weighed in the required quantity for the given batch size of concrete. The fibres are added in aggregate weighing hopper or any other suitable part of the process of batching plant to ensure uniform mixing. Other ingredients of concrete are then mixed inside the mixer. Mixing is done for a required amount of time to ensure uniform consistency of concrete. The concrete is then discharged from the mixer to transit mixers for dispatch to the construction site.
The present invention will now be explained with the help of the following example, however; the scope of the invention should not be limited to said example and experiments. It is to be understood that the above-described embodiments are merely illustrative principles of the present invention and that many variations may be devised by those skilled in the art without departing from the scope of the present invention. It is, therefore, intended that such variations be included with the scope of the claims.
Experiments:
Mixing:
1) Lab Trial mix: In the lab trial, Firstly, coarse, fine aggregates, cement, fly ash/GGBS dry mixed for 1 minute, secondly, fibers are added to the dry mix and mixed for 1 minute, Thirdly, water and admixture added to get required workability.
2) Field Trial mix: Fibres are added to the aggregate bucket and discharged into the central mixer with sequence Aggregate, cement, Water and admixture and mixed for 35 seconds.
Fresh and hardened concrete properties:
Fresh concrete properties are tested according to IS 1199-2018. The workability of the concrete is measured by using a slump cone test at 1, 2 & 3 hrs. Specimens for testing compressive strength and prepared according to IS 516-2021.
The dosages of fibers are tried in the range of 0.8, 1.0, 1.2, 1.4, 1.6, 1.8, 2.0 Kg/cum. From the observations It has found that there is no adverse effects of addition of fibers on the workability, retention period and compressive strength.

The plastic shrinkage cracking observed by casting bar moulds and found the best results are with 1.8 Kg/cum dosages.

Plastic Shrinkage behavior:
Comparison with control mix using waste fishnet fibers trials conducted in the various combinations of the binders and found that there are no adverse effects on the workability, retention, and compressive strength.


We have casted bar molds to observe cracks. It has been observed that there is a major impact on the plastic shrinkage behavior of the concrete. We have observed plastic shrinkage cracks on control specimens whereas cracks do not appear on the surface of the concrete containing fish net fibers.

Field Results:
After successful lab trials, 1.8 Kg/cum dosage was used while supply of various grades of concrete. The concrete is also supplied in different structures like slabs, floors, pavements etc. using fishnet fibers. No plastic shrinkage cracks were observed in any of the pours.
Although the invention has been described with reference to specific embodiments, the present description should not be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternate embodiments of the invention, will become apparent to persons skilled in the art upon reference to the description of the invention. It is therefore contemplated that such modifications can be made without departing from the spirit or scope of the present invention as defined.

We claim:
1. An improved concrete composite comprising:
• 5-20% by weight of hydraulic cement,
• 65-80% by weight of aggregates, and
• 6-8% by weight of water,
• 0.01-0.1% by weight of polymer fibers, and/or
• other 5-12% by weight of cementitious materials;
• optionally 0.06-0.3% by weight of admixtures.

2. The concrete composite as claimed in claim 1, wherein the polymer fibers are selected from the group consisting of waste fishing net fibers, rubber tyres and mixture thereof.
3. The concrete composite as claimed in claim 1, wherein the hydraulic cement is selected from the group consisting of OPC, PPC, PSC and mixture thereof.
4. The concrete composite as claimed in claim 1, wherein aggregates are selected from the group consisting of Basalt, limestone, sandstone, and mixture thereof.
5. The concrete composite as claimed in claim 1, wherein the admixtures are selected from the group consisting of Naphthalene, Polycarboxylic ether and mixture thereof.
6. The concrete composite as claimed in claim 1, wherein the cementitious materials are selected from the group consisting of fly ash, slag, silica fumes and mixture thereof.
7. The method of preparing the improved concrete composite as claimed in claim 1, comprising the steps of:

- processing the net fibers by washing, sizing and separating;
- chopping said fibers mechanically to reduce the length to a predetermined size;
- separating the lumps and knots manually before packaging the fibers;
- cleaned and processed fibers are added in a predetermined amount in aggregate weighing hopper of batching plant or any other suitable part of the process to ensure uniform mixing;
- mixing all the designed ingredients of concrete in the mixer;
- mixing is done for the required amount of time to ensure uniform consistency of concrete;
- discharging said concrete from the mixer to transit mixers for dispatch to construction site.