Description:DESCRIPTION:
Field of the invention:
[0001] The present disclosure generally relates to the technical field of concrete based constructional material, and in specific relates to a method of preparation of high-performance cement concrete with colloidal silica for high temperature applications for enhancing mechanical strength, thermal stability, and durability at elevated temperatures.
Background of the invention:
[0002] Concrete has been employed in many road and building applications for centuries. Cement is a mass product that is mainly used for the preparation of concretes for the construction industry. Cement-based products are pre-designed for short pot life and difficult for handling. Inadequate curing adversely affects hydration process and strength gaining of the cement in the composite. Upon drying, there is shrinkage in the bonding material leading to minute gaps, loosening out, and de-bonding the substrates held together. The material also gets brittle upon hard drying. Of all the cement-based products, concrete is the most commonly used product in the construction industry. Concrete is a rocklike material produced by mixing coarse and fine aggregates along with cement and water and allowing the mixture to harden.

[0003] Now-a-days, creating quality concrete does not depend solely on achieving required strength, but improving the durability of the concrete and reducing porosity to provide a longer life span. The strength of concrete is tested using the compressive strength test which is the most common test conducted on the hardened concrete because it is an easy test to perform and most of the desired characteristic properties of concrete are qualitatively related to the compressive strength.

[0004] Generally, the conventional concrete mixtures with enhanced strength are used extensively throughout the world for oil, gas, nuclear industry buildings, high-rise buildings, and power industries. The applications of such concrete are increasing day by day due to their superior structural performance, environmental friendliness, and energy-conserving implication. The search for alternative binders, cement replacement materials, is being carried out for many decades. The conventional methods to enhance high-temperature performance involve using supplementary cementitious materials (SCMs) like fly ash or slag. However, the conventional methods have limitations, including potential drawbacks in terms of cost, availability, and environmental impact.

[0005] Furthermore, the conventional concrete suffers strength loss, cracking, and spalling (explosive flaking) when exposed to heat, jeopardizing its structural integrity and safety in applications like furnace linings, nuclear reactors, and fire-resistant structures. The most common challenges of the conventional concrete includes dehydration of cement paste, thermal expansion, phase changes, and chemical breakdown. In specific, at elevated temperatures, the chemically bound water within the cement paste evaporates, leading to shrinkage, cracking, and strength loss. The concrete components expand at different rates when heated, creating internal stresses and potentially leading to cracking. In addition, certain minerals within the cement clinker (the main ingredient in Portland cement) undergo phase transitions at high temperatures, further weakening the concrete matrix. The high alkalinity of concrete can accelerate corrosion of steel reinforcement at elevated temperatures.

[0006] Therefore, there is a need for a method of preparation of high-performance cement concrete that enhances strength and durability properties of concrete. There is also a need for a method of preparation of a high-performance cement concrete that reduces weight and permeability of concrete. There is also a need for a method of preparation of a high-performance cement concrete that improves thermal stability and fire resistance of concrete.

[0007] There is also a need for a method of preparation of high-performance cement concrete that develops a new material for the construction industry that is made with colloidal silica. There is also a need for a method of preparation of a high-performance cement concrete that determines the optimal content of colloidal silica for use in concrete. There is also a need for a method of preparation of a high-performance cement concrete that investigates the effect of colloidal silica on the strength and durability of concrete.
Objectives of the invention:
[0008] The primary objective of the invention is to provide a high-performance cement concrete with colloidal silica for high temperature applications that enhances mechanical strength, thermal stability, and durability at elevated temperatures.

[0009] Another objective of the invention is to provide a high-performance cement concrete that reduces weight and permeability of concrete.

[0010] The other objective of the invention is to provide a high-performance cement concrete that improves fire resistance of concrete.

[0011] The other objective of the invention is to provide a method that develops a of high-performance cement concrete for the construction industry that is made with colloidal silica.

[0012] Yet another objective of the invention is to provide a method of preparation of a high-performance cement concrete that determines the optimal content of colloidal silica for use in concrete.

[0013] Further objective of the invention is to provide a method of preparation of a high-performance cement concrete that determines the effect of colloidal silica on the strength and durability of concrete.
Summary of the invention:
[0014] The present disclosure proposes a method for enhancing compressive strength of cement concrete for high temperature applications using colloidal silica. The following presents a simplified summary in order to provide a basic understanding of some aspects of the claimed subject matter. This summary is not an extensive overview. It is not intended to identify key/critical elements or to delineate the scope of the claimed subject matter. Its sole purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is presented later.

[0015] In order to overcome the above deficiencies of the prior art, the present disclosure is to solve the technical problem to provide a method of preparation of high-performance cement concrete with colloidal silica for high temperature applications for enhancing mechanical strength, thermal stability, and durability at elevated temperatures.

[0016] According to an aspect, the invention provides a method for enhancing the residual compressive strength of concrete specimens at elevated temperatures. At one step, plurality of concrete mixtures are prepared with and without silica. In specific, the concrete mixture is an M40 grade concrete. At another step, the concrete mixtures are casted into specimens. At another step, the concrete specimens are cured under standard conditions.

[0017] At another step, the concrete specimens are exposed to the elevated temperature that varies between 100°C and 400°C for a predetermined time period varies between 1 hour and 4 hours. In specific, the exposure of the concrete specimens at elevated temperatures is carried out in a furnace. At another step, the concrete specimens are cooled to room temperature. At another step, the residual compressive strengths of the concrete specimens are determined from each concrete mixture. At another step, a gain or loss in the compressive strength compared to pre-exposure strength are analyzed.

[0018] In one embodiment, the colloidal silica enhances the compressive strength of the concrete specimens when exposed to the elevated temperatures varies between 100°C and 400°C for the predetermined time periods between 1 hour and 4 hours. The compressive strength of the concrete specimens reaches a maximum value at the elevated temperature of 200°C for all concrete mixtures. The colloidal silica improves the residual compressive strength of the concrete composition compared to the concrete composition without colloidal silica at the elevated temperatures up to 300°C.

[0019] According to another aspect, the invention provides a method of preparation of a concrete mixture composition for enhancing performance at elevated temperatures. At one step, portland cement with water and fine and coarse aggregates are mixed thoroughly to produce the concrete mixture. At another step, the colloidal silica with nano-solids content of 30% is added to the cement concrete mixture in an amount of at least 2% by weight of the cement for replacement or at least 2.5% by weight of the cement for addition. At another step, the concrete compositions is cured.

[0020] Further, objects and advantages of the present invention will be apparent from a study of the following portion of the specification, the claims, and the attached drawings.
Detailed description of drawings:
[0021] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate an embodiment of the invention, and, together with the description, explain the principles of the invention.

[0022] FIG. 1 illustrates a flow chart of a method for enhancing the residual compressive strength of concrete specimens at elevated temperatures, in accordance of an exemplary embodiment of the invention.

[0023] FIG. 2 illustrates a flow chart of a method of preparation of a concrete mixture composition for enhancing performance at elevated temperatures, in accordance of an exemplary embodiment of the invention.

[0024] FIG. 3A illustrates a graphical representation of variation of residual compressive strength of M40 grade concrete exposed to 100°C with various time periods of exposure, in accordance of an exemplary embodiment of the invention.

[0025] FIG. 3B illustrates a graphical representation of variation of residual compressive strength of M40 grade concrete exposed to 200°C with various time periods of exposure, in accordance of an exemplary embodiment of the invention.

[0026] FIG. 3C illustrates a graphical representation of variation of residual compressive strength of M40 grade concrete exposed to 300°C with various time periods of exposure, in accordance of an exemplary embodiment of the invention.

[0027] FIG. 3D illustrates a graphical representation of variation of residual compressive strength of M40 grade concrete exposed to 400°C with various time periods of exposure, in accordance of an exemplary embodiment of the invention.
Detailed invention disclosure:
[0028] Various embodiments of the present invention will be described in reference to the accompanying drawings. Wherever possible, same or similar reference numerals are used in the drawings and the description to refer to the same or like parts or steps.

[0029] The present disclosure has been made with a view towards solving the problem with the prior art described above, and it is an object of the present invention to provide a method of preparation of high-performance cement concrete with colloidal silica for high temperature applications for enhancing mechanical strength, thermal stability, and durability at elevated temperatures.

[0030] According to an exemplary embodiment of the invention, FIG. 1 refers to a flow chart 100 of a method for enhancing the residual compressive strength of concrete specimens at elevated temperatures. At step 102, plurality of concrete mixtures are prepared with and without silica. In specific, the concrete mixture is an M40 grade concrete. At step 104, the concrete mixtures are casted into specimens. At step 106, the concrete specimens are cured under standard conditions.

[0031] At step 108, the concrete specimens are exposed to the elevated temperature that varies between 100°C and 400°C for a predetermined time period varies between 1 hour and 4 hours. In specific, the exposure of the concrete specimens at elevated temperatures is carried out in a furnace. At step 110, the concrete specimens are cooled to room temperature. At step 112, the residual compressive strengths of the concrete specimens are determined from each concrete mixture. At step 114, a gain or loss in the compressive strength compared to pre-exposure strength are analyzed.

[0032] In one embodiment herein, the colloidal silica enhances the compressive strength of the concrete specimens when exposed to the elevated temperatures varies between 100°C and 400°C for the predetermined time periods between 1 hour and 4 hours. The compressive strength of the concrete specimens reaches a maximum value at the elevated temperature of 200°C for all concrete mixtures. The colloidal silica improves the residual compressive strength of the concrete composition compared to the concrete composition without colloidal silica at the elevated temperatures up to 300°C.

[0033] According to an exemplary embodiment of the invention, FIG. 2refers to a flow chart of a method of preparation of a concrete mixture composition for enhancing performance at elevated temperatures. At step 202, portland cement with water and fine and coarse aggregates are mixed thoroughly to produce the concrete mixture. At step 204, the colloidal silica with nano-solids content of 30% is added to the cement concrete mixture in an amount of at least 2% by weight of the cement for replacement or at least 2.5% by weight of the cement for addition. At step 206, the concrete compositions is cured.

[0034] According to an exemplary embodiment of the invention, FIG. 3A refers to a graph 302 that depicts variation of residual compressive strength of M40 grade concrete exposed to 100°C with various time periods of exposure. FIG. 3B refers to a graph 304 that depicts variation of residual compressive strength of M40 grade concrete exposed to 200°C with various time periods of exposure. FIG. 3C refers to a graph 306 that depicts variation of residual compressive strength of M40 grade concrete exposed to 300°C with various time periods of exposure. FIG. 3D refers to a graph 308 that depicts variation of residual compressive strength of M40 grade concrete exposed to 400°C with various time periods of exposure.

[0035] In one embodiment herein, the values of the residual compressive strengths for three concrete mixtures of M40 includes M40CS0, M40CS2R and M40CS2.5A. M40 grade concrete without colloidal silica is considered as normal concrete. The variation of residual compressive strength of M40 grade concrete specimens at elevated temperatures of 100° C, 200° C, 300° C, 400° C for various duration exposure conditions are shown in the FIG. 1 to FIG. 4 respectively.

[0036] The residual compressive strengths of the M40CS0 concrete without the colloidal silica subjected to elevated temperatures is shown in Table 1.

[0037] Table 1:
Temperature (0C) Residual compressive strength(N/mm2) of concrete without colloidal silica for various durations of exposure
1 hour 2 hours 3 hours 4 hours
27 54.22 54.22 54.22 54.22
100 55.71 56.23 55.00 54.23
200 56.10 57.20 56.23 53.46
300 54.30 47.76 44.73 43.50
400 42.10 35.70 33.50 31.00

[0038] In one embodiment herein, the residual compressive strengths of the M40CS2R concrete with 2% replacement of the colloidal silica subjected to elevated temperatures is shown in Table 2.

[0039] Table 2:
Temperature (0C) Residual compressive strength (N/mm2)for duration of exposure
1 hour 2 hours 3 hours 4 hours
27 61.77 61.77 61.77 61.77
100 62.36 63.15 58.30 55.13
200 63.36 61.84 59.23 50.20
300 58.23 56.73 47.14 42.56
400 43.15 41.50 36.00 35.70

[0040] In one embodiment herein, the residual compressive strengths of M40CS2.5A concrete with 2.5% addition of colloidal silica subjected to elevated temperatures is shown in table 3.

[0041] Table 3:
Temperature (0C) Residual compressive strength (N/mm2) for duration of exposure
1 hour 2 hours 3 hours 4 hours
27 65.21 65.21 65.21 65.21
100 66.36 65.50 63.38 58.52
200 65.50 63.13 56.00 53.23
300 62.43 57.15 50.60 48.00
400 48.30 42.91 37.36 36.42

[0042] In one embodiment herein, the values of the residual compressive strength of M40 grades of concrete at elevated temperature of 100°C for various duration of exposure is shown in table 4.

[0043] Table 4:
Duration of exposure
(hours) Residual compressive strength (N/mm2)
Mix type M40CS0 M40CS2R M40CS2.5A
0 54.22 61.77 65.21
1 55.71 62.36 66.36
2 56.23 63.15 65.50
3 55.00 58.30 63.38
4 54.23 55.13 58.52

[0044] In one embodiment herein, it is observed that an increase in the residual compressive strength of M40CS0 concrete heated up to 200° C for 3 hours exposure duration for air cooled specimens. At 200° C and 4 hours duration, there is a decrease in the residual compressive strength. For 300° C and 400° C, the residual compressive strengths are decreased for all exposure durations for air cooling specimens as shown in the FIG. 1 to FIG. 4.

[0045] In one embodiment herein, the residual compressive strength is increased up to 200° C for 2 hours exposure for air cooled specimens for the M40CS2R concrete mix. The duration of exposure increasing the residual compressive strength was decreased for 3 hours and 4 hours.

[0046] In one embodiment herein, the residual compressive strength is increased up to 200° C for the M40CS2.5A concrete mixture for 2 hours exposure for air cooled specimens. The duration of exposure increasing the residual compressive strength was decreased for 3 hours and 4 hours.

[0047] In one embodiment herein, the compressive strength of the M40CS2R and M40CS2.5A concrete mixtures are observed to be increased when compared to the M40CS0 when subjected to elevated temperatures. This is due to high pozzoloanic nature of silica particles present in colloidal silica. The maximum value of compressive strength is observed to be more at elevated temperature of 200° C for all the concrete mixes.

[0048] In one embodiment herein, the replacement and addition of colloidal silica with 30 % nano solids content has shown improved strengths due to acceleration of hydration process forming additional CSH gel is formed resulting in the increase of strength. The values of compressive strength are observed to be decreased when temperatures increased beyond 200° C. This is because of reduction in bonding between binding material and aggregate due to dehydration.

[0049] In one embodiment herein, maximum values of compressive strength are observed for the M40CS2.5A concrete mixture when colloidal silica is added to the cement compared to other two mixtures when exposed to elevated temperatures for different duration of exposure.

[0050] Numerous advantages of the present disclosure may be apparent from the discussion above. In accordance with the present disclosure, the method for enhancing the compressive strength of cement concrete for high temperature applications using colloidal silica is disclosed. The proposed cement concrete with colloidal silica for high temperature applications enhances mechanical strength, thermal stability, and durability at elevated temperatures. The proposed cement concrete reduces weight and permeability of concrete. The proposed cement concrete improves fire resistance of concrete. The proposed cement concrete. The proposed method determines the optimal content of colloidal silica for use in concrete. The proposed method determines the effect of colloidal silica on the strength and durability of concrete.

[0051] It will readily be apparent that numerous modifications and alterations can be made to the processes described in the foregoing examples without departing from the principles underlying the invention, and all such modifications and alterations are intended to be embraced by this application.
, Claims:CLAIMS:
I / We Claim:
1. A method for enhancing the residual compressive strength of concrete specimens at elevated temperatures, comprising:
preparing plurality of concrete mixtures with and without colloidal silica;
casting the concrete mixtures into specimens;
curing the concrete specimens under standard conditions;
exposing the concrete specimens to the elevated temperature that varies between 100°C and 400°C for a predetermined time period that varies between 1 hour and 4 hours;
cooling the concrete specimens to room temperature;
determining the residual compressive strengths of the concrete specimens from each concrete mixture; and
analyzing a gain or loss in the compressive strength compared to pre-exposure strength.
2. The method as claimed in claim 1, wherein the concrete mixture is an M40 grade concrete.
3. The method as claimed in claim 1, wherein the colloidal silica enhances the compressive strength of the concrete specimens when exposed to the elevated temperatures varies between 100°C and 400°C for the predetermined time periods between 1 hour and 4 hours.
4. The method as claimed in claim 3, wherein the exposure of the concrete specimens to elevated temperatures is carried out in a furnace.
5. The method as claimed in claim 4, wherein the compressive strength of the concrete specimens reaches a maximum value at the elevated temperature of 200°C for all concrete mixtures.
6. The method as claimed in claim 1, wherein the colloidal silica improves the residual compressive strength of the concrete composition compared to the concrete composition without colloidal silica at the elevated temperatures up to 300°C.
7. A method of preparation of a concrete mixture composition for enhancing performance at elevated temperatures, comprising:
mixing portland cement with water and fine and coarse aggregates, thereby producing a concrete mixture;
adding colloidal silica with nano-solids content of 30% to the cement concrete mixture in an amount of at least 2% by weight of the cement for replacement or at least 2.5% by weight of the cement for addition; and
curing the concrete composition.