WO2018015873A1

WO2018015873A1 - A novel cement composition incorporating bulk fly ash and nano fly ash

Info

Publication number: WO2018015873A1
Application number: PCT/IB2017/054319
Authority: WO
Inventors: Dillip Kumar BERA; Ashoke Kumar RATH; Sujay Kumar Singh PARASHAR
Original assignee: Individual
Current assignee: Individual
Priority date: 2016-07-18
Filing date: 2017-07-18
Publication date: 2018-01-25
Anticipated expiration: 2019-01-18

Abstract

Aspects of the present disclosure provides a dry cement composition including a mixture of Portland cement and fly ash, wherein said Portland cement is present in an amount ranging from about 82% to about 88% by weight relative to total weight of the cement composition and said fly ash is present in an amount ranging from about 12% to about 18% by weight relative to total weight of the cement composition, and wherein said fly ash comprises a mixture of nano fly ash and bulk fly ash in a weight ratio ranging from about 2:10 to about 8:10.

Description

A NOVEL CEMENT COMPOSITION INCORPORATING BULK FLY ASH AND

NANO FLY ASH

TECHNICAL FIELD

[0001] The disclosure generally relates to a cement composition. In particular, the present disclosure pertains to a cement composition including ordinary Portland cement, bulk fly ash and nano fly ash.

BACKGROUND

[0002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.

[0003] Portland cement enjoys the most widespread use for constructional purposes at the present time. Ordinary Portland cement (OPC) is primarily a mixture of calcium silicate and calcium aluminate minerals which react with water to form a dense, solid paste. The reaction products of ordinary Portland cement are calcium hydroxide (CH), ettringite, and a poorly- crystalline phase called calcium-silicate-hydrate (C-S-H).

[0004] Fly ash is a well known material generated as a by-product of burning coal, typically generated during the production of electricity at coal-fired power plants. Fly ashes contain variable amounts of different components: typically high amounts of glass, as well as mineral phases which had been present as impurities in the original coal, or which may have been produced during cooling of the molten material. Fly ash typically contains 85% glassy, amorphous components. ASTM C618 has classified fly ash into two classes, Class C and Class F, depending on the total sum of silica, alumina and ferric oxide present. Class F contains more than 70% of the above oxides, and Class C contains less than 70% but more than 50%. Class C fly ash typically is high in calcium, and is normally produced as a byproduct of the combustion of lignite or sub-bituminous coal.

[0005] Being finely divided and highly siliceous, fly ash is a well known pozzolan which forms a slowly hardening cement with water and hydrated lime. A pozzolan can be defined as "A siliceous or siliceous and aluminous material, which in itself possesses little or no cementitious value but will, in finely divided form and in the presence of moisture, chemically react with calcium hydroxide at ordinary temperatures to form compounds possessing cementitious properties". This chemical reaction between the pozzolan and the calcium hydroxide is often referred to as the "pozzolanic reaction".

[0006] It is well known to add fly ash and other pozzolans to Portland cement compositions. Commercial Portland cements containing appreciable amounts, 15 to 40 percent, of pozzolan such as fly ash are known as "Type IP" cements. Moreover, Portland cement concretes have been prepared containing fly ash to increase workability and pumpability, to control bleeding, reduce shrinkage, etc. The major objective however sought by the addition of fly ash to Portland cement concretes has been for the enhancement of compressive strength of the hardened concrete. In such concretes the fly ash has been added as a replacement for the cement and/or sand, the pozzolanic fly ash reacting with the lime produced as the result of the hydration reaction between the Portland cement component and water to give additional strength. Such "pozzolanic reaction" of the fly ash increases the strength of the concrete, especially at ages of 28 days or more. The cementitious compounds produced by the "pozzolanic reaction" are believed to fill the pores and capillaries that are normally present in concrete and as a result the concrete containing fly ash also becomes less permeable to water and salt solutions.

[0007] In practice, the amount of fly ash added to Portland cement concrete has varied depending upon the desired end properties of the concrete. Generally, when a given Portland cement concrete is redesigned to include fly ash, between 10 and 30% of the Portland cement, by weight, is replaced by a volume of fly ash which ranges from weight of the fly ash equal to that of the cement removed to weight of the fly ash equal to two times that of the cement removed. One-hundred pounds of typical Type I Portland cement will produce enough calcium hydroxide during its reaction with water to react with about 20 pounds of a typical fly ash. The amount of fly ash, therefore, over and above this 100 cement to 20 fly ash weight ratio acts essentially in a physical way to affect bleeding, workability and heat of hydration. When the amount of fly ash used in concrete is equal in volume to the amount removed and the cement substitution exceeds about 20%, the compressive strengths of the set concrete are lower as compared to a reference non-fly ash-containing concrete, at all ages, and for this reason substitution beyond the approximate 20% level in concrete has been avoided in practice. Further, few reports suggest inclusion of fly ash with the particle size range from few nanometers to few micrometers. However, such reports and studies could not culminate to a level of wide spread economic utility owing to one or more shortcomings associated therewith. [0008] There is therefore a longstanding need to realize a cement composition that incorporates, along with ordinary Portland cement, bulk fly ash and nano fly ash in suitable proportions to alleviate one or more shortcomings associated the cement compositions currently in practise.

OBJECTS OF THE INVENTION

[0009] An object of the present disclosure is to overcome one or more disadvantages associated with conventional cement compositions.

[0010] Another object of the present disclosure is to provide a cement composition including Portland cement and fly ash.

[0011] Another object of the present disclosure is to provide a cement composition including Portland cement, bulk fly ash and nano fly ash.

[0012] Another object of the present disclosure is to provide a cement composition including ordinary Portland cement, bulk fly ash and nano fly ash that exhibits desirable compressive strength.

[0013] Another object of the present disclosure is to provide a cement composition including ordinary Portland cement, bulk fly ash and nano fly ash that exhibits desirable flexural and tensile strength.

[0014] Another object of the present disclosure is to provide a cement composition that is economic to produce and finds wide spread economic utility.

[0015] Various objects, features, aspects and advantages of the present invention will become more apparent from the detailed description of the invention herein below along with the accompanying figures in which like numerals represent like components.

SUMMARY

[0016] The disclosure generally relates to a cement composition. In particular, the present disclosure pertains to a cement composition including ordinary Portland cement, bulk fly ash and nano fly ash and a method of manufacture thereof.

[0017] An aspect of the present disclosure provides a dry, cement composition including a mixture of Portland cement and fly ash, wherein said Portland cement is present in an amount ranging from about 82% to about 88% by weight relative to total weight of the cement composition and said fly ash is present in an amount ranging from about 12% to about 18%) by weight relative to total weight of the cement composition, and wherein said fly ash comprises a mixture of nano fly ash and bulk fly ash in a weight ratio ranging from about 2: 10 to about 8: 10. In an embodiment, said Portland cement includes 53 grade ordinary Portland cement conforming to IS: 12269 (1987). In an embodiment, said fly ash comprises Class F fly ash as defined by ASTM C 618-15. In an embodiment, said nano fly ash includes fly ash with an average particle size (D50) ranging from about 50 nm to about 100 nm. In an embodiment, said bulk fly ash includes fly ash with an average particle size (D50) ranging from about 0.5 μπι to about 20 μπι. In an embodiment, said Portland cement is present in an amount of about 84% by weight relative to the total weight of the cement composition and wherein said fly ash is present in an amount of about 16% by weight relative to the total weight of the cement composition. In an embodiment, said fly ash includes the mixture of nano fly ash and bulk fly ash in a weight ratio of about 6: 10.

[0018] Another aspect of the present disclosure provides a cement composition including: Portland cement in an amount of about 84% by weight relative to total weight of said cement composition; bulk fly ash in an amount of about 10% by weight relative to total weight of said cement composition; and nano fly ash in an amount of about 6% by weight relative to total weight of said cement composition; wherein, said bulk fly ash comprises Class F fly ash as defined by ASTM C 618-15 with an average particle size (D50) ranging from about 0.5 μπι to about 20 μπι and wherein said nano fly ash comprises Class F fly ash as defined by ASTM C 618-15 with an average particle size (D50) ranging from about 50 nm to about 100 nm. In an embodiment, said Portland cement comprises 53 grade ordinary Portland cement conforming to IS: 12269 (1987).

[0019] Various objects, features, aspects and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.

BRIEF DESCRIPTION OF DRAWINGS

[0020] FIG. 1 illustrates an exemplary graph depicting % increase in Compressive strength of concrete on inclusion of about 10% bulk fly ash (FA) and varying amount of nano-fly ash (nFA) in OPC in comparison to 28 days NCC.

[0021] FIG. 2 illustrates an exemplary graph depicting % water absorption in concrete samples prepared from cement compositions with Portland cement, varying amount of bulk fly ash and varying amount of nano fly ash. [0022] FIG. 3A illustrates an exemplary graph depicting % weight loss in concrete samples prepared from cement compositions with Portland cement, varying amount of bulk fly ash and varying amount of nano fly ash upon exposure to 5% sulphuric acid.

[0023] FIG. 3B illustrates an exemplary graph depicting % strength loss in concrete samples prepared from cement compositions with Portland cement, varying amount of bulk fly ash and varying amount of nano fly ash upon exposure to 5% sulphuric acid.

[0024] FIG. 4A illustrates an exemplary graph depicting % weight loss in concrete samples prepared from cement compositions with Portland cement, varying amount of bulk fly ash and varying amount of nano fly ash upon exposure to 5% magnesium sulphate solution.

[0025] FIG. 4B illustrates an exemplary graph depicting % strength loss in concrete samples prepared from cement compositions with Portland cement, varying amount of bulk fly ash and varying amount of nano fly ash upon exposure to 5% magnesium sulphate solution.

[0026] FIG. 5A illustrates an exemplary graph depicting % water absorption in mortar samples prepared from cement compositions with Portland cement, varying amount of bulk fly ash and varying amount of nano fly ash.

[0027] FIG. 5B illustrates an exemplary graph depicting % reduction in water absorption in mortar samples prepared from cement compositions with Portland cement, varying amount of bulk fly ash and varying amount of nano fly ash.

DETAILED DESCRIPTION

[0028] The following is a detailed description of embodiments of the disclosure depicted in the accompanying drawings. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.

[0029] Each of the appended claims defines a separate invention, which for infringement purposes is recognized as including equivalents to the various elements or limitations specified in the claims. Depending on the context, all references below to the "invention" may in some cases refer to certain specific embodiments only. In other cases it will be recognized that references to the "invention" will refer to subject matter recited in one or more, but not necessarily all, of the claims. [0030] As used in the description herein and throughout the claims that follow, the meaning of "a," "an," and "the" includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of "in" includes "in" and "on" unless the context clearly dictates otherwise.

[0031] All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. "such as") provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.

[0032] Various terms as used herein are shown below. To the extent a term used in a claim is not defined below, it should be given the broadest definition persons in the pertinent art have given that term as reflected in printed publications and issued patents at the time of filing.

[0033] The disclosure generally relates to a cement composition. In particular, the present disclosure pertains to a cement composition including ordinary Portland cement, bulk fly ash and nano fly ash and a method of manufacture thereof.

[0034] An aspect of the present disclosure provides a dry, cement composition including a mixture of Portland cement and fly ash, wherein said Portland cement is present in an amount ranging from about 82% to about 88% by weight relative to total weight of the cement composition and said fly ash is present in an amount ranging from about 12% to about 18%) by weight relative to total weight of the cement composition, and wherein said fly ash comprises a mixture of nano fly ash and bulk fly ash in a weight ratio ranging from about 2: 10 to about 8: 10. In an embodiment, said Portland cement comprises 53 grade ordinary Portland cement conforming to IS: 12269 (1987). In an embodiment, said fly ash comprises Class F fly ash as defined by ASTM C 618-15. In an embodiment, said nano fly ash includes fly ash with an average particle size (D50) ranging from about 50 nm to about 100 nm. In an embodiment, said bulk fly ash includes fly ash with an average particle size (D50) ranging from about 0.5 μπι to about 20 μπι. In an embodiment, said Portland cement is present in an amount of about 84%> by weight relative to the total weight of the cement composition and wherein said fly ash is present in an amount of about 16%> by weight relative to the total weight of the cement composition. In an embodiment, said fly ash includes the mixture of nano fly ash and bulk fly ash in a weight ratio of about 6: 10. [0035] Another aspect of the present disclosure provides a cement composition including: Portland cement in an amount of about 84% by weight relative to total weight of said cement composition; bulk fly ash in an amount of about 10% by weight relative to total weight of said cement composition; and nano fly ash in an amount of about 6% by weight relative to total weight of said cement composition; wherein, said bulk fly ash comprises Class F fly ash as defined by ASTM C 618-15 with an average particle size (D50) ranging from about 0.5 μπι to about 20 μπι and wherein said nano fly ash comprises Class F fly ash as defined by ASTM C 618-15 with an average particle size (D50) ranging from about 50 nm to about 100 nm. In an embodiment, said Portland cement comprises 53 grade ordinary Portland cement conforming to IS: 12269 (1987).

[0036] The advantageous cement composition, in accordance with embodiments of the present disclosure, can be prepared utilizing any of the grades (types) of Portland cement as known to a person skilled in the art. Exemplary grades (types) of Portland cement can include but not limited to Type I, Type II, Type III, Type IV, Type V, Type la, Type Ila, Type Ilia as defined in ASTM CI 50. In a preferred embodiment, the Portland cement includes 53 Grade Ordinary Portland Cement - IS: 12269 (1987).

[0037] The bulk fly ash, in accordance with embodiments of the present disclosure, can be of any class as known to a person skilled in the art, including but not limited to Class C fly ash and Class F fly ash. In a preferred embodiment, bulk fly ash includes Class F fly ash as defined by ASTM C 618. In an embodiment, bulk fly ash can be of any particle size as known to a person skilled in art with D50 ranging from 0.3 micrometer to 200 micrometers so as to serve its intended purpose as laid down in embodiments of the present disclosure.

[0038] The nano fly ash, in accordance with embodiments of the present disclosure, can be prepared from bulk fly ash of any class as known to a person skilled in the art, including but not limited to Class C fly ash and Class F fly ash. In a preferred embodiment, nano fly ash is prepared by subjecting Class F fly ash as defined by ASTM C 618 to any size reduction process(es) as known to a person skilled in the art. In an embodiment, Class F fly ash is subjected to size reduction utilizing high energy ball mill to obtain nano fly ash. Preferably, nano fly ash with D50 ranging from about 1 nanometer (nm) to about 200 nanometers (nm) is utilized for preparing cement compositions of the present disclosure. Alternatively, commercially available nano fly ash with D50 ranging from about 1 nanometer (nm) to about 200 nanometers (nm) can be utilized for preparing cement compositions of the present disclosure. [0039] The cement composition, realized in accordance with embodiments of the present disclosure, can be utilized to prepare concrete and mortar by mixing with other ingredients and/or additives as known to a person skilled in the art. Examples of other ingredients and/or additives include sand, gravel, crushed stone, water, admixtures like water reducers, shrinkage reducers, retarding admixtures, accelerating admixtures and the like. Water reducers can be selected from any or a combination of water reducers as known to a person skilled in the art, including but not limited to lignosulfonates, synthetic sulfonates, polycarboxylates and the like. In an embodiment, water reducer can be used in an amount ranging from about 0.01% to about 3% by weight relative to the total weight of the cement composition. In a preferred embodiment, lignosulfonate (Conplast® P211, commercially available from FOSROC) is utilized as a water reducer in an amount ranging from about 0.1% to about 1%) by weigh relative to the total weight of the cement composition. In a most preferred embodiment, lignosulfonate (Conplast® P211, commercially available from FOSROC) is utilized as a water reducer in an amount of about 0.5% by weigh relative to the total weight of the cement composition.

[0040] While the foregoing describes various embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. The scope of the invention is determined by the claims that follow. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.

EXAMPLES

Cement Compositions including varying amount of bulk fly ash (FA)

[0041] The study was conducted to measure effects of addition of varying amount of bulk fly ash to ordinary Portland cement. Particularly, effect of addition of varying amount of bulk fly ash (commercially available fly ash of grade F as defined in ASTM C618-15 with D50 ranging from about 0.5 μπι to about 20 μπι) to Portland cement (53 Grade Ordinary Portland Cement - IS: 12269: 1987), by replacing corresponding amount of Portland cement, was studied by preparing concrete and mortar using these cement compositions and then measuring mechanical properties of the same. Varying amounts of fly ash including 0%, 10%, 20%, 30%, 40% and 50% by weight relative to the total weight of the cement composition was added to the Ordinary Portland Cement (OPC). From the results of the studies, as provided in Table 1 through 3 below, it could be observed that Compressive Strength, Flexural Strength and Split Tensile Strength of the concrete samples prepared by using Portland cement with 10% bulk fly ash (CI 00) exhibits better strength at different curing ages than that of concrete samples maintained as control (53 Grade Ordinary Portland Cement with no addition of fly ash, referred as NCC).

Table 1 - Effect on Compressive Strength of Concrete on addition of varying amount of bulk fly ash (FA) to OPC

Table 2 - Effect on Flexural Strength of Concrete on addition of varying amount of bulk fly ash (FA) to OPC

Table 3 - Effect on Split Tensile Strength of Concrete on addition of varying amount of bulk fly ash (FA) to OPC

Curing Split Tensile strength in MPa

Age in NCC CIOO C200 C300 C400 C500

Days (0% FA) (10% FA) (20% FA) (30% FA) (40% FA) (50% FA)

28 days 5.45 5.41 5.22 4.98 4.68 4.32

56 days 5.63 5.78 5.44 5.28 4.95 4.73

90 days 5.92 6.18 5.88 5.45 5.24 4.88 [0042] As depicted in Table 4 below, it could be observed that Compressive Strength of the mortar samples prepared by using ordinary Portland cement (OPC) with 10% bulk fly ash (CI 00) exhibits better strength at different curing ages than that of mortar samples maintained as control (53 Grade Ordinary Portland Cement with no addition of fly ash, referred as NCM).

Table 4 - Effect on Compressive Strength of Cement Mortar on addition of varying amount of bulk fly ash (FA) to OPC

Concrete composition including Portland cement, bulk fly ash and water reducer

[0043] Concrete compositions were prepared by mixing ordinary Portland cement in an amount of about 89% by weight of the total cement composition, bulk fly ash (commercially available fly ash of grade F as defined in ASTM C618-15) in an amount of about 10% by weight of the total cement composition and varying amount of Conplast P211 (i.e. 0.1%, 0.2%, 0.4%, 0.5%, 0.7%, 1%, 2% and 5%) that can act as a water reducer. It could be observed that Conplast P211 in an amount of 0.5% by weight of total weight of the cement composition can realize a concrete composition with desired properties in terms of water demand, setting time and workability.

Preparation of nano fly ash

[0044] Commercially available fly ash of grade-F as defined in ASTM C618-15 was subjected to further size reduction in high energy ball mill. Appropriate amount of fly ash was taken in high energy ball mill such that volume ratio between balls and fly ash particles is about 10: 1. High energy ball mill was operated for 15 hours and resultant particles were observed for their particle size distribution (D50). The resultant particles were of size (D50) ranging from about 50 nm to about 100 nm and the same was confirmed utilizing particle size analyser, XRD and SEM techniques.

Cement Compositions including 10% bulk fly ash (FA) and varying amount of nano fly ash (nFA) [0045] Cement compositions were prepared by mixing Ordinary Portland Cement (53 Grade Ordinary Portland Cement - IS: 12269: 1987) in an amount ranging from about 82% to about 90% by weight of the total cement composition, bulk fly ash (commercially available fly ash of grade F as defined in ASTM C618-15) in an amount of about 10% by weight of the total cement composition and nano fly ash (prepared as above) with particle size (D50) ranging from about 50 nm to about 100 nm (preparation as shown in the example above) in a varying amount i.e. 0%, 2%, 4%, 6% and 8% by weight of the total weight of the cement composition. The resultant compositions were then studied for the effect of addition of nano fly ash (nFA) in cement compositions including ordinary Portland cement and bulk fly ash by preparing concrete and mortar using these cement compositions and then measuring mechanical properties of concrete and durability of mortar and concrete.

[0046] Results of the studies are as provided in Table 5 through 10 below. Surprisingly, it could be observed that Compressive Strength, Flexural Strength and Split Tensile Strength of the concrete samples prepared by using Portland cement with 10% bulk fly ash and 6% nano fly ash exhibits superior strength at different curing ages than that of concrete samples maintained as control (53 Grade Ordinary Portland Cement with no addition of fly ash, referred as NCC) and concrete sample prepared by Portland cement with 10% bulk fly ash and other 8% of nano fly ash. It could be observed that with inclusion of increasing amount of nano fly ash, starting from about 0% by weight relative to the total weight of the cement composition through about 6% by weight relative to the total weight of the cement composition, the compressive strength, flexural strength and split tensile strength increases. However, on inclusion of 8% nano fly ash, compressive strength, flexural strength and split tensile strength decreases. Concrete samples prepared from cement composition with about 84%) by weight of Portland cement, about 10% by weight of bulk fly ash and about 6% by weight of nano fly ash exhibits improvement in the strength by 10.52%, 14.66% and 27.02% at 28, 56 and 90 days respectively in comparison to normal cement concrete (NCC) for same curing days. Flexural and split tensile strength behaviour of these samples were also similar as compressive strength behaviour. Concrete mixes containing 6% nano fly ash (CI 06) exhibits more strength and durability properties (acid test, sulphate test, water absorption and sorptivity test) in comparison to other compositions. Fig. 1 illustrates an exemplary graph depicting % increase in Compressive strength of concrete on inclusion of about 10% bulk fly ash (FA) and varying amount of nano-fly ash (nFA) in OPC in comparison to 28 days NCC (without addition of fly ash or nano fly ash). Table 5 - Effect on Compressive Strength of Concrete on inclusion of about 10% bulk fly ash (FA) and varying amount of nano-fly ash (nFA) in OPC

Table 6 - Percentage (%) Increase in Compressive Strength of Concrete on inclusion of about 10% bulk fly ash (FA) and varying amount of nano-fly ash (nFA) in OPC

- Effect on Flexural Strength of Concrete on inclusion of about 10% bulk fly ash (FA) and varying amount of nano-fly ash (nFA) in OPC

Flexural strength in MPa

Curing

NCC CIOO C102 C104 C106 C108 Age in

(0% FA, (10% FA + (10% FA + (10% FA + (10% FA + (10% FA + Days

0% nFA) 0% nFA) 2% nFA) 4% nFA) 6% nFA) 8% nFA) 8 days 8.30 8.25 8.47 8.54 8.66 8.56 6 days 8.65 8.71 8.98 9.77 9.98 9.65 0 days 9.11 9.22 9.58 10.35 10.67 10.44 Table 8 - Percentage (%) Increase in Flexural Strength of Concrete on inclusion of about 10% bulk fly ash (FA) and varying amount of nano-fly ash (nFA) in OPC

- Effect on Split tensile Strength of Concrete on inclusion of about 10% bulk fly ash (FA) and varying amount of nano-fly ash (nFA) in OPC

Table 10 - Percentage (%) Increase in Split tensile Strength of Concrete on inclusion of about 10% bulk fly ash (FA) and varying amount of nano-fly ash (nFA) to OPC

Percentage (%) increase in Split tensile strength w.r.t.

28 days strength of NCC

Curing Age

NCC C102 C104 C106 C108 in Days

(0% FA, (10% FA + (10% FA + (10% FA + (10% FA + 0% nFA) 2% nFA) 4% nFA) 6% nFA) 8% nFA)

28 days 0.00 2.02 6.06 12.66 11.56

56 days 3.30 7.34 12.66 20.55 16.51

90 days 8.62 14.31 22.39 28.07 24.22 [0047] Apart from strength tests, water absorption test and durability tests (Exposure to 5% sulphuric acid and Exposure to 5% Magnesium sulphate solution) were also carried out to confirm observation of this surprising result i.e. superiority of cement composition including about 84% by weight of Portland cement, about 6% by weight of nano fly ash and 10% by weight of bulk fly ash in comparison to other compositions. Fig. 2 through 4 illustrates results of these studies, wherein each of the concrete sample is prepared from a cement composition denoted by following codes - NCC ordinary Portland cement without addition of bulk fly ash or nano fly ash, CI 00 denotes Portland cement with addition of 10% bulk fly ash, C200 denotes Portland cement with addition of 20% bulk fly ash, C300 denotes Portland cement with addition of 30% bulk fly ash, C400 denotes Portland cement with addition of 40% bulk fly ash, C500 denotes Portland cement with addition of 50% bulk fly ash, CI 02 denotes Portland cement with addition of 10% bulk fly ash and 2% nano fly ash, CI 04 denotes Portland cement with addition of 10% bulk fly ash and 4% nano fly ash, CI 06 denotes Portland cement with addition of 10% bulk fly ash and 6% nano fly ash and CI 08 denotes Portland cement with addition of 10% bulk fly ash and 8% nano fly ash.

[0048] Fig. 2 illustrates % water absorption in concrete samples prepared from cement compositions with Portland cement, varying amount of bulk fly ash and varying amount of nano fly ash. Fig. 3A illustrates % weight loss in concrete samples prepared from cement compositions with Portland cement, varying amount of bulk fly ash and varying amount of nano fly ash upon exposure to 5% sulphuric acid. Fig. 3B illustrates % strength loss in concrete samples prepared from cement compositions with Portland cement, varying amount of bulk fly ash and varying amount of nano fly ash upon exposure to 5% sulphuric acid. Fig. 4A illustrates % weight loss in concrete samples prepared from cement compositions with Portland cement, varying amount of bulk fly ash and varying amount of nano fly ash upon exposure to 5% magnesium sulphate solution. Fig. 4B illustrates % strength loss in concrete samples prepared from cement compositions with Portland cement, varying amount of bulk fly ash and varying amount of nano fly ash upon exposure to 5% magnesium sulphate solution.

[0049] Results of the mortar study is as provided in the Table 11 below. It can be observed that by inclusion of nano fly ash (nFA) in an amount of 6% by weight relative to total weight of the cement composition, the strength was improved by about 14% and about 23% at 28 and 56 days respectively in comparison to normal cement mortar (NCM) for same days. Water absorption was found to be less than that with normal cement mortar (NCM), which means refinement of the pore structure was achieved by addition of nano fly ash to the cement composition.

Table 11 - Percentage (%) Increase in Split tensile Strength of Cement Mortar on inclusion of about 10% bulk fly ash (FA) and varying amount of nano-fly ash (nFA) to

OPC

[0050] Fig. 5A and Fig. 5B illustrates results of the water absorption test on mortar samples prepared from cement compositions with Portland cement, varying amounts of bulk fly ash and varying amounts of nano fly ash, wherein each of the mortar sample is prepared from a cement composition denoted by following codes - NCM ordinary Portland cement without addition of bulk fly ash or nano fly ash, CM 100 denotes Portland cement with addition of 10% bulk fly ash, CM200 denotes Portland cement with addition of 20% bulk fly ash, CM300 denotes Portland cement with addition of 30% bulk fly ash, CM400 denotes Portland cement with addition of 40% bulk fly ash, C500 denotes Portland cement with addition of 50% bulk fly ash, CI 02 denotes Portland cement with addition of 10% bulk fly ash and 2% nano fly ash, CI 04 denotes Portland cement with addition of 10% bulk fly ash and 4% nano fly ash, CI 06 denotes Portland cement with addition of 10% bulk fly ash and 6% nano fly ash and CI 08 denotes Portland cement with addition of 10% bulk fly ash and 8%) nano fly ash.

[0051] Fig. 5A illustrates % water absorption in mortar samples prepared from cement compositions with Portland cement and varying amount of bulk fly ash. Fig. 5B illustrates % reduction in water absorption in mortar samples prepared from cement compositions with Portland cement and varying amount of bulk fly ash.

[0052] Regression analysis was also carried out to establish correlation between strength and durability properties. It could be observed that there is a good correlation between these properties. The value of correlation coefficient of concrete containing nano fly ash at all ages for strength properties varied from 0.845 to 0.983, and durability properties varied from 0.822 to 0.97. The high value of correlation coefficient indicates strong relationship between different properties.

ADVANTAGES OF THE INVENTION

[0053] The present disclosure provides for a cement composition to overcome one or more disadvantages associated with conventional cement compositions.

[0054] The present disclosure provides for a cement composition including ordinary Portland cement and fly ash.

[0055] The present disclosure provides for a cement composition including ordinary Portland cement, bulk fly ash and nano fly ash.

[0056] The present disclosure provides for a cement composition including ordinary Portland cement, bulk fly ash and nano fly ash that exhibits desirable compressive strength.

[0057] The present disclosure provides for a cement composition including ordinary Portland cement, bulk fly ash and nano fly ash that exhibits desirable flexural and tensile strength.

[0058] The present disclosure provides for a cement composition that is economic to produce and finds wide spread economic utility.

Claims

We Claim:

1. A dry cement composition comprising a mixture of Portland cement and fly ash, wherein said Portland cement is present in an amount ranging from about 80% to about 89%) by weight relative to total weight of said cement composition and said fly ash is present in an amount ranging from about 1 1%> to about 20% by weight relative to total weight of said cement composition, and wherein said fly ash comprises mixture of nano fly ash and bulk fly ash in a weight ratio ranging from about 5: 10 to about 7: 10.

2. The cement composition of claim 1, wherein said Portland cement comprises 53 grade ordinary Portland cement conforming to IS: 12269 (1987).

3. The cement composition of claim 1, wherein said fly ash comprises Class F fly ash as defined by ASTM C 618-15.

4. The cement composition of claim 1, wherein said nano fly ash comprises fly ash with an average particle size (D50) ranging from about 50 nm to about 100 nm.

5. The cement composition of claim 1, wherein said bulk fly ash comprises fly ash with an average particle size (D50) ranging from about 0.5 μπι to about 20 μπι.

6. The cement composition of claim 1, wherein said Portland cement is present in an amount of about 84%> by weight relative to the total weight of said cement composition and wherein said fly ash is present in an amount of about 16%> by weight relative to the total weight of said cement composition, and wherein said fly ash comprises mixture of nano-sized fly ash and bulk fly ash in a weight ratio of about 6: 10.

7. A cement composition comprising:

Portland cement in an amount of about 84%> by weight relative to total weight of said cement composition;

bulk fly ash in an amount of about 10%> by weight relative to total weight of said cement composition; and

nano fly ash in an amount of about 6%> by weight relative to total weight of said cement composition;

wherein, said bulk fly ash comprises Class F fly ash as defined by ASTM C 618-15 with an average particle size (D50) ranging from about 0.5 μπι to about 20 μπι and wherein, said nano fly ash comprises Class F fly ash as defined by ASTM C 618-15 with an average particle size (D50) ranging from about 50 nm to about 100 nm.

8. The cement composition of claim 7, wherein said Portland cement comprises 53 grade ordinary Portland cement conforming to IS: 12269 (1987).