Concrete suitable for harsh working conditions and preparation method thereof

Abstract

The present invention discloses a concrete suitable for harsh working conditions and a preparation method thereof. The concrete comprises the following components: cement, gravel, sand, fly ash, a water reducer, expanded clay, nanocellulose, silica, and composite fibers; the composite fibers include graphene oxide-modified glass fibers and modified polyvinyl alcohol fibers; the preparation method of the graphene oxide-modified glass fibers comprises the following steps: soaking the glass fibers in a graphene oxide dispersion for 5-12 minutes and drying them; and the preparation method of the modified polyvinyl alcohol fibers comprises the following steps: forming a polyvinyl acetate film on the surface of the polyvinyl alcohol fibers. The present invention effectively improves the concrete's tolerance to temperature differences, cracking resistance, and mechanical strength through the coordinated use of the various components.

Description

Technical Field

[0001] The present invention relates to the technical field of concrete, and in particular to concrete suitable for harsh working conditions and a preparation method thereof. Background Art

[0002] Most of the common cracks in concrete are surface cracks of varying depths. In the early stages, the temperature inside the concrete rises due to the heat of cement hydration, and the surface temperature is low after demolding. The temperature difference between the inside and the surface forms a very steep temperature gradient, which generates large tensile stress. At this time, the early strength of the concrete is low, the ultimate tensile strength is small, and coupled with poor maintenance, cracks are very likely to form.

[0003] This is especially true in harsh environments, such as high altitudes, where conditions include low pressure, large temperature differences, negative temperatures, strong winds, and dryness. Low pressure can deteriorate the pore structure of concrete, adversely affecting its mechanical properties, durability, and other properties. When subjected to large temperature differences or uneven sunlight, concrete undergoes periodic "expansion and contraction" with temperature changes. Due to concrete's poor thermal conductivity, a large temperature gradient can easily form, causing significant temperature stress. When the ultimate tensile strength of concrete is insufficient to withstand temperature stress, cracks will form, leading to damage to the concrete structure. Furthermore, strong winds and dryness can make it difficult for concrete to replenish moisture from the outside during curing. Consequently, a large amount of internal moisture will be lost, resulting in insufficient cement hydration and shrinkage cracks. Under negative temperature conditions, the moisture in the concrete will freeze and expand, which can also cause cracks in the concrete.

[0004] Therefore, there is an urgent need to provide a concrete suitable for harsh working conditions. Summary of the Invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides a concrete suitable for harsh working conditions.

[0006] The present invention also provides a method for preparing the concrete.

[0007] The present invention also provides application of the above concrete.

[0008] According to a first embodiment of the present invention, a concrete suitable for harsh working conditions includes the following components:

[0009] cement, crushed stone, sand, fly ash, water reducing agent, expanded clay, nanocellulose, silica and composite fibers;

[0010] The composite fiber comprises graphene oxide modified glass fiber and modified polyvinyl alcohol fiber;

[0011] The preparation method of the graphene oxide modified glass fiber comprises the following steps: soaking the glass fiber in a graphene oxide dispersion for 5-12 minutes and drying the glass fiber;

[0012] The preparation method of the modified polyvinyl alcohol fiber comprises the following steps:

[0013] A polyvinyl acetate film is formed on the surface of the polyvinyl alcohol fiber.

[0014] According to some embodiments of the present invention, the severe working conditions include at least one of low pressure, large temperature difference, negative temperature, strong wind and dryness.

[0015] According to some embodiments of the invention, the cement comprises Portland cement.

[0016] According to some embodiments of the present invention, the strength grade of the silicate cement is not less than P.O.42.5.

[0017] The terms "not less than" to greater than or equal to should be understood to include the number.

[0018] According to some embodiments of the present invention, the water reducer includes a polycarboxylate water reducer.

[0019] According to some embodiments of the present invention, in the composite fiber, the added mass ratio of the graphene oxide modified glass fiber and the modified polyvinyl alcohol fiber is (1-3): (1-2).

[0020] According to some embodiments of the present invention, the graphene oxide-modified glass fiber consists of long fibers, short fibers and medium fibers, wherein the mass ratio of the long fibers, the short fibers and the medium fibers is 1:3:2.

[0021] According to some embodiments of the present invention, the length of the short fibers is 5-10 mm, the length of the medium fibers is 10-15 mm, and the length of the long fibers is 15-20 mm.

[0022] According to some embodiments of the present invention, the content of graphene oxide in the graphene oxide dispersion is 3-5 mg / mL.

[0023] According to some embodiments of the present invention, the method for preparing the modified polyvinyl alcohol fiber may include the following steps:

[0024] The modified polyvinyl alcohol fiber is obtained by placing the polyvinyl alcohol fiber in an aqueous solution containing polyvinyl acetate emulsion, subjecting the fiber to ultrasonic treatment, and baking the solution.

[0025] According to some embodiments of the present invention, the mass ratio of the polyvinyl alcohol fiber to the polyvinyl acetate emulsion is 1:8-12.

[0026] According to some embodiments of the present invention, the length of the polyvinyl alcohol fiber is 7 mm-9 mm.

[0027] According to some embodiments of the present invention, the diameter of the polyvinyl alcohol fiber is 25 μm-35 μm.

[0028] According to some embodiments of the present invention, the pH of the polyvinyl acetate emulsion is 4-5.

[0029] According to some embodiments of the present invention, the ultrasonic treatment is performed with an ultrasonic power of 40 kW to 60 kW.

[0030] According to some embodiments of the present invention, the ultrasonic treatment time is 10 min-20 min.

[0031] According to some embodiments of the present invention, the baking temperature is 35°C-45°C.

[0032] According to some embodiments of the present invention, the baking time is 3 hours to 5 hours.

[0033] According to some embodiments of the present invention, the method for preparing the modified polyvinyl alcohol fiber further includes a third water washing treatment after baking.

[0034] According to some embodiments of the present invention, the concrete comprises, by weight:

[0035] 80-120 parts of cement, 100-140 parts of crushed stone, 110-140 parts of sand, 4-8 parts of fly ash, 0.1-1 part of water reducer, 8-12 parts of expanded clay, 2-6 parts of nanocellulose, 1-5 parts of silica and 3-8 parts of composite fiber.

[0036] According to some embodiments of the present invention, the concrete comprises, by weight:

[0037] 90-110 parts of cement, 110-130 parts of crushed stone, 120-140 parts of sand, 5-7 parts of fly ash, 0.4-0.6 parts of water reducer, 9-11 parts of expanded clay, 3-5 parts of nanocellulose, 2-4 parts of silica and 4-6 parts of composite fiber.

[0038] The method for preparing the above-mentioned concrete according to the second embodiment of the present invention comprises the following steps: mixing the components.

[0039] In some embodiments of the present invention, the method for preparing concrete specifically comprises the following steps:

[0040] S1. Mixing cement, fly ash, sand, crushed stone and expanded clay to obtain a first mixture;

[0041] S2, adding a water reducer and part of the water to the first mixture to obtain a second mixture;

[0042] S3. Adding nanocellulose, silicon dioxide, composite fiber and remaining water into the second mixture, and mixing to obtain concrete.

[0043] The application of the above concrete or the concrete prepared by the above preparation method in the field of construction according to the third aspect of the present invention.

[0044] According to some embodiments of the present invention, there are at least the following beneficial effects:

[0045] 1. The present invention increases the ductility and self-healing properties of concrete by adding expansive clay to the raw materials. When the concrete is affected by temperature changes, the expansive clay changes its volume by absorbing and releasing water, thereby alleviating the stress inside the concrete and ensuring the integrity and stability of the concrete.

[0046] 2. The present invention adds nanocellulose, silica and composite fibers to the raw materials. Nanocellulose is a nano-scale fiber material with high tensile strength and toughness. It can form a network structure in concrete, repair microcracks to a certain extent, and enhance the crack resistance and ductility of concrete. Silica can fill the micro cracks in concrete, help improve the density and mechanical properties of concrete, and also improve the thermal stability of concrete.

[0047] The modified polyvinyl alcohol fiber in the composite fiber forms a layer of polyvinyl acetate film with weak acidity on the surface, which can increase the fiber's antioxidant and water resistance, thereby extending the service life of the fiber, helping to reduce cracking and oxidation reactions in concrete, and improving the durability of concrete. In addition, the polyvinyl acetate film itself has certain flexibility and adhesion, and can be tightly combined with concrete particles to enhance the overall performance of concrete. Especially in an environment with large temperature differences, the temperature changes inside the concrete will cause corresponding contraction and expansion, which can easily lead to cracking or damage of the concrete. The flexibility of the polyvinyl acetate film can relieve stress concentration inside the concrete and reduce the occurrence of cracking.

[0048] The graphene oxide-modified glass fiber in the composite fiber can effectively inhibit the occurrence of concrete cracking by increasing the toughness and tensile strength of concrete. Furthermore, graphene oxide itself has excellent mechanical properties and a high specific surface area. After modification on the surface of the glass fiber, it can form a uniformly dispersed lubricating layer, which better disperses and transmits stress within the concrete, thereby reducing the occurrence and expansion of cracks. Furthermore, the graphene oxide-modified glass fiber can form a heat conduction channel in the concrete, improving the thermal conductivity of the concrete, thereby reducing thermal stress caused by temperature differences and reducing the risk of temperature cracking in the concrete. Furthermore, the high electrical conductivity of graphene oxide also helps to evenly distribute the temperature within the concrete, reducing local temperature differences and further improving the concrete's resistance to temperature differences.

[0049] 3. The solution of the present invention effectively improves the temperature difference tolerance, crack resistance and mechanical strength of concrete through the coordinated use of various components.

[0050] Other features and advantages of the present invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the present invention. DETAILED DESCRIPTION

[0051] The following will clearly and completely describe the concept and technical effects of the present invention in conjunction with the embodiments to fully understand the purpose, features and effects of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0052] If the specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or those recommended by the manufacturer. All reagents or instruments used, if the manufacturer is not specified, are commercially available conventional products.

[0053] In the description of the present invention, if there are descriptions of first, second, third, etc., they are only used to distinguish technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0054] In the description of the present invention, the terms "comprises" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or apparatus that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to the process, method, product or apparatus.

[0055] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between such minimum and maximum values. Further, when a range refers to an integer, every integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe a feature or characteristic, the ranges can be combined. In other words, unless otherwise indicated, all ranges disclosed herein are understood to include any and all subranges subsumed therein.

[0056] "Prepared from" is synonymous with "comprising." As used herein, the terms "comprising," "including," "having," "containing," or any other variations thereof, are intended to cover a non-exclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises the listed elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, process, method, article, or apparatus.

[0057] The conjunction "consisting of" excludes any unspecified element, step, or component. If used in a claim, this phrase renders the claim closed, excluding materials other than those described, except for conventional impurities associated therewith. When the phrase "consisting of" appears in a clause of the body of a claim, rather than immediately following the subject matter, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0058] "Parts by mass" refers to the basic unit of measurement used to express the mass ratio of multiple components. One part can represent any unit of mass, such as 1g or 2.689g. If we say that the mass of component A is a parts and the mass of component B is b parts, this means the ratio of the mass of component A to the mass of component B is a:b. Alternatively, we could say that the mass of component A is aK and the mass of component B is bK (K is an arbitrary number representing a multiplication factor). It's important to note that, unlike parts by mass, the sum of the mass of all components is not limited to 100 parts.

[0059] Unless otherwise specified, "about" in the present invention means that the allowable error is within ±5%.

[0060] "And / or" is used to indicate that one or both of the stated situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0061] In the embodiments of this application, unless otherwise specified,

[0062] P.O42.5 ordinary Portland cement was purchased from Yiyang Conch Cement;

[0063] Sand: fineness modulus is 2.5, apparent density is 2.65g / cm3 Natural river sand;

[0064] Crushed stone: diameter 20mm, crushing index 15%, water absorption 5%, apparent density 2590kg / m 3 of gravel;

[0065] Fly ash: first-grade fly ash, purchased from Jining Hengzhi New Building Materials Co., Ltd.

[0066] Polycarboxylate water reducer: Point-TS1 polycarboxylate water reducer, purchased from Fujian Kezhijie New Materials Co., Ltd.

[0067] Example 1

[0068] This example provides a concrete suitable for harsh working conditions. The raw material composition is as follows by weight:

[0069]

[0070] The composite fiber includes graphene oxide modified glass fiber and modified polyvinyl alcohol fiber, and the added mass ratio of the graphene oxide modified glass fiber to the modified polyvinyl alcohol fiber is 2:1.

[0071] The preparation method of graphene oxide modified glass fiber is as follows:

[0072] (1) Weigh graphene oxide and disperse it (using ultrasonic dispersion for 30 min) in water. The added mass volume ratio of graphene oxide to water is 4 mg / mL to obtain a graphene oxide dispersion.

[0073] (2) Glass fibers (composed of long fibers, short fibers, and medium fibers, wherein the mass ratio of the long fibers, short fibers, and medium fibers is 1:3:2, the length of the short fibers is 5-10 mm, the length of the medium fibers is 10-15 mm, and the length of the long fibers is 15-20 mm) are immersed in a graphene oxide dispersion for 10 min and dried at 105°C to obtain graphene oxide-modified glass fibers.

[0074] The preparation method of modified polyvinyl alcohol fiber is as follows:

[0075] 1 g of polyvinyl alcohol fiber (about 8 mm in length and about 31 μm in average diameter) was immersed in 100 mL of an aqueous solution containing 10 g of polyvinyl acetate emulsion, stirred, and ultrasonically treated (50 kW) for 15 min. The polyvinyl alcohol fiber was taken out, baked at 40°C for 4 h, and then washed with clean water to obtain modified polyvinyl alcohol fiber.

[0076] This example also provides a method for preparing the above-mentioned concrete suitable for harsh working conditions, and the steps are as follows:

[0077] S1. Put cement, fly ash, sand, gravel and expanded clay into a concrete mixer and dry mix for about 15 seconds to obtain a first mixture;

[0078] S2. The weighed water reducer and water (about 70% of the amount) are put into a mixer and mixed with the first mixture for about 40 seconds until the concrete is fully fluidized. Nanocellulose, silica, and composite fibers are then added. The container containing the water reducer is rinsed with the remaining water. The rinse water is poured into the mixer and stirred again for 5 minutes to fully mix. Finally, the mixed concrete is formed and cured according to the test standard for the corresponding performance to obtain a concrete sample.

[0079] Example 2

[0080] This example provides a concrete suitable for harsh working conditions. The raw material composition is as follows by weight:

[0081]

[0082] The composite fiber includes graphene oxide modified glass fiber and modified polyvinyl alcohol fiber, and the added mass ratio of the graphene oxide modified glass fiber to the modified polyvinyl alcohol fiber is 2:1.

[0083] The preparation method is the same as that in Example 1.

[0084] Example 3

[0085] This example provides a concrete suitable for harsh working conditions. The raw material composition is as follows by weight:

[0086]

[0087] The composite fiber includes graphene oxide modified glass fiber and modified polyvinyl alcohol fiber, and the added mass ratio of the graphene oxide modified glass fiber to the modified polyvinyl alcohol fiber is 1:2.

[0088] The preparation method is the same as that in Example 1.

[0089] Comparative Example 1

[0090] This example provides a concrete suitable for harsh working conditions. The raw material composition is as follows by weight:

[0091]

[0092] The composite fiber includes graphene oxide modified glass fiber and modified polyvinyl alcohol fiber, and the added mass ratio of the graphene oxide modified glass fiber to the modified polyvinyl alcohol fiber is 2:1.

[0093] The preparation method is the same as that in Example 1.

[0094] Comparative Example 2

[0095] This example provides a concrete suitable for harsh working conditions. The raw material composition is as follows by weight:

[0096]

[0097] The composite fiber includes graphene oxide modified glass fiber and modified polyvinyl alcohol fiber, and the added mass ratio of the graphene oxide modified glass fiber to the modified polyvinyl alcohol fiber is 2:1.

[0098] The preparation method is the same as that in Example 1.

[0099] Comparative Example 3

[0100] This example provides a concrete suitable for harsh working conditions. The raw material composition is as follows by weight:

[0101]

[0102] The preparation method is the same as that in Example 1.

[0103] Comparative Example 4

[0104] This example provides a concrete suitable for harsh working conditions. The raw material composition is as follows by weight:

[0105]

[0106]

[0107] The preparation method is the same as that in Example 1.

[0108] Test example

[0109] The concrete suitable for harsh working conditions of Examples 1-3 and Comparative Examples 1-5 was molded in a mold with a size of 10 cm × 10 cm × 10 cm. Three curing environments were set, including a standard environment, a low pressure and low humidity environment, and a low pressure and low humidity environment with a large temperature difference, as shown in Table 1. The concrete was cured for 28 days and tested for its compressive strength and splitting tensile strength. The surface of each group of samples was observed to see if there were any cracks, and the length of the cracks was recorded. The compressive strength and splitting compressive strength were tested in accordance with GB / T50081-2002 "Test Method for Mechanical Properties of Ordinary Concrete". The difference between the blank control group concrete and the examples and comparative examples is that no expansive clay, polycarboxylate water-reducing agent, nanocellulose, silica and composite fiber were added. The experiment was repeated 3 times and the average value was taken.

[0110] Table 1

[0111]

[0112] Table 2

[0113]

[0114]

[0115] Table 3

[0116]

[0117]

[0118] The results are shown in Tables 2 and 3. It can be seen from Tables 2 and 3 that the concretes prepared in Examples 1-3 did not crack under low pressure and large temperature difference environments, while Comparative Examples 1-4 and the blank control group all had cracks to varying degrees. The results show that the concrete prepared by the scheme of the present invention has excellent compressive strength and crack resistance under low pressure and large temperature difference environments.

[0119] The embodiments of the present invention are described in detail above in conjunction with the embodiments, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge scope of ordinary technicians in the relevant technical field without departing from the purpose of the present invention.

Claims

1. A concrete suitable for harsh working conditions, characterized in that: Includes the following components: cement, crushed stone, sand, fly ash, water reducing agent, expanded clay, nanocellulose, silica and composite fibers; The composite fiber comprises graphene oxide modified glass fiber and modified polyvinyl alcohol fiber; The preparation method of the graphene oxide modified glass fiber comprises the following steps: soaking the glass fiber in a graphene oxide dispersion for 5-12 minutes and drying the glass fiber; The preparation method of the modified polyvinyl alcohol fiber comprises the following steps: A polyvinyl acetate film is formed on the surface of the polyvinyl alcohol fiber.

2. The concrete according to claim 1, characterized in that The water reducer includes a polycarboxylate water reducer.

3. The concrete according to claim 1, characterized in that In the composite fiber, the added mass ratio of graphene oxide modified glass fiber and modified polyvinyl alcohol fiber is (1-3): (1-2).

4. The concrete according to claim 1, characterized in that The graphene oxide modified glass fiber consists of long fibers, short fibers and medium fibers, wherein the mass ratio of the long fibers, the short fibers and the medium fibers is 1:3:

2.

5. The concrete according to claim 4, characterized in that The length of the short fibers is 5-10 mm, the length of the medium fibers is 10-15 mm, and the length of the long fibers is 15-20 mm.

6. The concrete according to claim 1, characterized in that In the graphene oxide dispersion, the content of graphene oxide is 3-5 mg / mL.

7. The concrete according to claim 1, characterized in that The preparation method of the modified polyvinyl alcohol fiber comprises the following steps: The modified polyvinyl alcohol fiber is obtained by placing the polyvinyl alcohol fiber in an aqueous solution containing polyvinyl acetate emulsion, subjecting the fiber to ultrasonic treatment, and baking the solution.

8. The concrete according to claim 7, characterized in that The mass ratio of the polyvinyl alcohol fiber to the polyvinyl acetate emulsion is 1:8-12.

9. The concrete according to claim 1, characterized in that The concrete comprises, by weight: 80-120 parts of cement, 100-140 parts of crushed stone, 110-140 parts of sand, 4-8 parts of fly ash, 0.1-1 part of water reducer, 8-12 parts of expanded clay, 2-6 parts of nanocellulose, 1-5 parts of silica and 3-8 parts of composite fiber.

10. The concrete according to claim 9, characterized in that The concrete comprises, by weight: 90-110 parts of cement, 110-130 parts of crushed stone, 120-140 parts of sand, 5-7 parts of fly ash, 0.4-0.6 parts of water reducer, 9-11 parts of expanded clay, 3-5 parts of nanocellulose, 2-4 parts of silica and 4-6 parts of composite fiber.

11. The method for preparing concrete according to any one of claims 1 to 10, characterized in that: The following steps are involved: Just mix the components.

12. Use of the concrete according to any one of claims 1 to 10 or the concrete prepared by the preparation method according to claim 11 in the field of construction.

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