Permeable concrete and its preparation method and application

Abstract

The present invention relates to the field of concrete technology, and discloses a permeable concrete, a preparation method thereof, and an application thereof. The raw materials for preparing the permeable concrete of the present invention include: cement, fly ash, fine aggregate, coarse aggregate, water reducer, carbon nanotube-modified carbon fiber, hydrophobically modified hydroxyethyl cellulose, and water; wherein, the particle size of the fine aggregate is 3.5 to 4.75 mm, the particle size of the coarse aggregate is 4.76 to 9.5 mm, and the water-cement ratio of the permeable concrete is 0.2 to 0.25. The present invention designs continuous granular aggregates, and then matches carbon nanotube-modified carbon fiber and hydrophobically modified hydroxyethyl cellulose to prepare permeable concrete that not only has excellent compressive strength (greater than 60 MPa) and water permeability (greater than 4 mm / S), but also has excellent anti-clogging performance. Applying it to road construction can not only reduce the cost of road repair, but also help promote the rapid development of urban road construction.

Description

Technical Field

[0001] The present invention relates to the technical field of concrete, and in particular to permeable concrete and a preparation method and application thereof. Background Art

[0002] Permeable concrete (PC) is a porous concrete composed of cement, coarse aggregate, a small amount or no fine aggregate, admixtures, and water. Its porosity typically ranges from 15% to 35%. Commonly known as sandless concrete, discontinuously graded concrete, porous concrete, or honeycombed concrete, permeable concrete is an engineering material with high water permeability. Compared to traditional concrete, permeable concrete has more pores, allowing rainwater to seep into the ground, cooling the surface. It also releases moisture in hot weather, increasing air humidity and mitigating the urban heat island effect. Therefore, it is widely used in urban road construction.

[0003] In related technologies, permeable concrete pavement has advantages such as reducing rainwater runoff, alleviating urban waterlogging, increasing groundwater, alleviating the heat island effect, and improving skid resistance. However, it also has disadvantages such as low compressive strength, easy clogging, and poor durability. In order to improve these shortcomings, adjusting the water-cement ratio, adding fine aggregate, composite fiber or mineral admixtures (fly ash) have become the main improvement measures. However, in actual applications, it has been found that while improving the mechanical properties of permeable concrete, the permeability of permeable concrete is inevitably reduced. It is difficult to maintain a balance between the mechanical properties and permeability of permeable concrete. Moreover, the residual permeability decreases significantly over time, which increases the cost of road repair and is not conducive to the rapid development of urban road construction.

[0004] Therefore, there is an urgent need to seek a permeable concrete with excellent compressive strength and permeability and good anti-clogging performance, as well as a preparation method and application thereof. Summary of the Invention

[0005] The present invention aims to address at least one of the technical problems existing in the prior art. To this end, the present invention provides a permeable concrete, its preparation method, and its application. The permeable concrete produced using the ingredients of the present invention exhibits excellent compressive strength and permeability, with a compressive strength exceeding 60 MPa and an initial permeability exceeding 4 mm / s. Furthermore, the permeable concrete exhibits excellent anti-clogging properties. After 36 months of natural clogging, its residual permeability remains above 88%, making it suitable for widespread use in urban road construction.

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

[0007] The present invention also provides an application of permeable concrete in preparing building or road materials.

[0008] In a first aspect of the present invention, a permeable concrete is provided, wherein the raw materials for preparing the permeable concrete include the following components:

[0009] Cement, fly ash, fine aggregate, coarse aggregate, water reducing agent, carbon nanotube modified carbon fiber, hydrophobically modified hydroxyethyl cellulose and water;

[0010] The particle size of the fine aggregate is 3.5 to 4.75 mm, the particle size of the coarse aggregate is 4.76 to 9.5 mm, and the water-cement ratio of the permeable concrete is 0.2 to 0.25.

[0011] The permeable concrete according to the embodiment of the present invention has at least the following beneficial effects:

[0012] (1) The permeable concrete of the present invention has excellent compressive strength. On the one hand, the present invention increases the bonding area between the aggregate and the cement paste by reasonably matching fine aggregate and coarse aggregate and optimizing the water-cement ratio, thereby improving the compressive strength. On the other hand, the permeable concrete of the present invention is also matched with carbon nanotube-modified carbon fiber and hydrophobically modified hydroxyethyl cellulose, wherein the carbon nanotube-modified carbon fiber is obtained by chemically grafting carbon nanotubes to the surface of carbon fiber using a coupling agent. The carbon nanotubes can exert the small size effect of microfibers inside the concrete, improve the particle grading, and optimize the microstructure of the matrix. Since the carbon nanotubes have a large specific surface area and chemical activity, it is conducive to forming a gelling system with the carbon nanotube-modified carbon fiber as the core, thereby improving the integrity of the cement hydration product and ultimately achieving the purpose of improving the compressive strength. Hydrophobically modified hydroxyethyl cellulose is a compound that introduces hydrophobic groups into the hydroxyethyl cellulose molecule. Its addition to concrete is conducive to improving the viscosity and fluidity of the material, avoiding excessive accumulation of cement paste, forming a local cementing layer, and helping to improve the cement's wrapping of aggregates, thereby improving the compressive strength.

[0013] (2) The permeable concrete of the present invention has excellent initial permeability and anti-clogging performance. The present invention effectively improves the anti-clogging performance of concrete by rationally combining hydrophobically modified hydroxyethyl cellulose. This is presumably related to the hydrophobic protective film formed by the hydrophobically modified hydroxyethyl cellulose on the cement surface. When the hydrophobically modified hydroxyethyl cellulose is added, the protective effect of the hydrophobic layer slows down the scouring of the cement particle surface, thereby preventing pore clogging.

[0014] Furthermore, the addition of carbon nanotube-modified carbon fibers to the permeable concrete of the present invention also helps improve the durability of the concrete material to a certain extent. Since carbon nanotube-modified carbon fibers are fiber assemblies with a high elastic modulus, they can mitigate larger cracks when the permeable concrete matrix is ​​damaged. This is because when large cracks are transmitted to the carbon nanotube-modified carbon fibers, the carbon nanotubes on their surface increase friction, inducing the formation of more small microcracks. This facilitates the sufficient dissipation of energy during the fracture process, thereby delaying the damage of the permeable concrete and improving its durability.

[0015] In some embodiments of the present invention, the raw materials for preparation include the following components in parts by weight:

[0016]

[0017] In some embodiments of the present invention, the raw materials for preparation include the following components in parts by weight:

[0018]

[0019] In some embodiments of the present invention, the cement is Portland cement, and the strength grade of the Portland cement is 42.5, 42.5R, 52.5 or 52.5R.

[0020] In some embodiments of the present invention, the fine aggregate is selected from at least one of artificial sand, lake sand, mountain sand, and desalinated sea sand. Preferably, the fine aggregate is artificial sand with a particle size of 3.5 to 4.75 mm.

[0021] In some embodiments of the present invention, the coarse aggregate includes crushed stone, preferably having a particle size of 4.76 to 9.5 mm. When the particle size of the coarse aggregate is the same, the permeable concrete prepared with crushed stone has higher compressive strength and flexural strength than that prepared with pebbles.

[0022] In some embodiments of the present invention, the water reducer is selected from at least one of polycarboxylic acid water reducers, naphthalene water reducers, anthracene water reducers, aminosulfonate water reducers, and ligninsulfonate water reducers.

[0023] In some embodiments of the present invention, the water reducer is a polycarboxylic acid water reducer.

[0024] Polycarboxylic acid-based water reducers have long side chains with large molecular weight, which can ionize into highly polar hydroxyl, carboxyl and sulfonic acid groups in aqueous solution. These highly polar groups can be directly adsorbed on the surface of carbon fibers, helping to improve the surface hydrophobicity of carbon fibers, thereby improving the dispersion effect of carbon nanotube-modified carbon fibers and avoiding local accumulation.

[0025] In some embodiments of the present invention, the carbon nanotube-modified carbon fiber is obtained by chemically grafting carbon nanotubes onto the surface of carbon fiber using a coupling agent.

[0026] In some embodiments of the present invention, the coupling agent is selected from hexamethylene diisocyanate and / or 4,4'-methylenebis(phenyl isocyanate).

[0027] In some embodiments of the present invention, the length of the carbon nanotube-modified carbon fiber is 8 to 10 mm.

[0028] In some embodiments of the present invention, the carbon nanotube-modified carbon fiber has a single filament diameter of 7 to 8 μm.

[0029] In some embodiments of the present invention, the method for preparing the carbon nanotube-modified carbon fiber specifically comprises the following steps:

[0030] S1, adding a coupling agent, carbon fiber and a catalyst to a solvent, reacting and drying to obtain isocyanate-treated carbon fiber;

[0031] S2. Dispersing the carboxylated multi-walled carbon nanotubes in a solvent, then adding the isocyanate-treated carbon fibers, reacting at 75-85° C., washing with acetone, and drying to obtain the product.

[0032] In some embodiments of the present invention, the solvent comprises N,N-dimethylformamide, and the catalyst comprises dibutyltin dilaurate.

[0033] In some embodiments of the present invention, the coupling agent is an isocyanate coupling agent; preferably, the coupling agent is at least one selected from hexamethylene diisocyanate and / or 4,4'-methylenebis(phenyl isocyanate).

[0034] In some embodiments of the present invention, in step S2, the mass ratio of the carboxylated multi-walled carbon nanotubes to the isocyanated carbon fibers is 1:3 to 8, preferably 1:5.

[0035] A second aspect of the present invention provides a method for preparing the permeable concrete as described in any one of the first aspects, comprising mixing the preparation raw materials.

[0036] The preparation method according to the embodiment of the present invention has at least the following beneficial effects: the preparation method of the permeable concrete of the present invention is simple and suitable for industrial production.

[0037] In some embodiments of the present invention, the preparation method specifically comprises the following steps:

[0038] S11, according to the above parts by weight, mixing the cement, fly ash, carbon nanotube-modified carbon fiber and hydrophobically modified hydroxyethyl cellulose, and then adding a sulfamate water reducer and part of the water, mixing to obtain a primary mixture;

[0039] S12, mixing the fine aggregate, coarse aggregate and the remaining water, adding the primary mix, and stirring until evenly mixed.

[0040] Based on the low water-cement ratio used in the permeable concrete of the present invention, the cement slurry formed by mixing water and cement has a strong adsorption effect on the carbon nanotube-modified carbon fibers, which easily causes the carbon nanotube-modified carbon fibers to cluster in the matrix. Therefore, during the feeding process, the cement, fly ash, carbon nanotube-modified carbon fibers and hydrophobically modified hydroxyethyl cellulose are first mixed, and then the aminosulfonate water reducer and part of the water are added, which helps to improve the dispersion effect.

[0041] A third aspect of the present invention provides use of the permeable concrete according to any one of the first aspects in preparing building or pavement materials.

[0042] 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

[0043] 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.

[0044] The terms "preferably," "more preferably," and the like, used herein refer to embodiments of the present invention that may provide certain benefits under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful, nor is it intended to exclude other embodiments from the scope of the present invention.

[0045] 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.

[0046] In the description of the present invention, the reference term "and / or" includes all and any combinations of one or more of the associated listed items.

[0047] In the description of the present invention, reference to terms such as "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the exemplary expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0048] In the description of the present invention, the silicate cement is ordinary silicate cement with a strength grade of 42.5; the fine aggregate is artificial sand with a particle size of 3.5 to 4.75 mm, and the coarse aggregate is crushed stone with a particle size of 4.76 to 9.5 mm, where the particle size refers to the particle size distribution range; the carbon fiber is purchased from Dongyi Yang (Jinan) New Materials Co., Ltd., wherein the carbon fiber length is 8.5 to 9.5 mm and the monofilament diameter is about 7 μm.

[0049] 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.

[0050] Example 1

[0051] This embodiment provides a permeable concrete and a preparation method thereof, wherein the raw materials for preparing the permeable concrete include the following components by weight:

[0052]

[0053]

[0054] The fine aggregate is manufactured sand with a particle size of 3.5 to 4.75 mm, and the coarse aggregate is crushed stone with a particle size of 4.76 to 9.5 mm. The water-cement ratio is 0.25. The hydrophobically modified hydroxyethyl cellulose is purchased from Ashland, model HE10K, with a viscosity of approximately 9,000 to 16,000 mPa·s (cps). The carbon nanotube-modified carbon fiber is obtained by chemically grafting carbon nanotubes onto the surface of the carbon fiber using a coupling agent. The specific preparation process includes the following steps:

[0055] S1. 30 parts of carbon fibers (purchased from Dongyi Yang (Jinan) New Materials Co., Ltd., wherein the carbon fibers have a length of 8.5 to 9.5 mm and a monofilament diameter of about 7 μm) are dispersed in 80 parts of N,N-dimethylformamide solution, and 5 parts of hexamethylene diisocyanate and 4,4'-methylenebis(phenyl isocyanate) in equal weight ratio are added as coupling agents at 50°C. 0.05 parts of dibutyltin dilaurate are added as a catalyst, and the mixture is stirred at 80°C for 6 to 8 hours, followed by solid-liquid separation, and the solid phase is collected and dried to obtain isocyanated carbon fibers.

[0056] S2. Weigh 5 parts of carboxylated multi-walled carbon nanotubes (CNTs-COOH, purchased from Beijing Dekedaojin Technology Co., Ltd., model CNT205, outer diameter 20-30 nm, length about 15 μm, purity ≥98%) and disperse them in 80 parts of N,N-dimethylformamide, then add isocyanate-modified carbon fibers at a mass ratio of 1:5 between carboxylated multi-walled carbon nanotubes and isocyanate-modified carbon fibers, react at 80°C for 36 hours, wash with acetone, and dry to obtain the obtained carbon nanotube-modified carbon fibers having a length of about 8.5-9.5 mm.

[0057] The preparation method of the above-mentioned permeable concrete comprises:

[0058] According to the above weight proportions, silicate cement, fly ash, carbon nanotube-modified carbon fiber and hydrophobically modified hydroxyethyl cellulose are first mixed, and then aminosulfonate water reducer and 50% of water are added and mixed to obtain a primary mixture; then fine aggregate, coarse aggregate and the remaining 50% of water are mixed, added to the primary mixture, and the material can be discharged after stirring evenly.

[0059] Example 2

[0060] This embodiment provides a permeable concrete and a preparation method thereof, wherein the raw materials for preparing the permeable concrete include the following components by weight:

[0061]

[0062] Among them, the fine aggregate is artificial sand with a particle size of 3.5 to 4.75 mm, and the coarse aggregate is crushed stone with a particle size of 4.76 to 9.5 mm; the water-cement ratio is 0.25. The preparation process of carbon nanotube-modified carbon fiber refers to Example 1, and the hydrophobically modified hydroxyethyl cellulose is purchased from Ashland, model HE10K.

[0063] The preparation method of the above-mentioned permeable concrete comprises:

[0064] According to the above weight proportions, silicate cement, fly ash, carbon nanotube-modified carbon fiber and hydrophobically modified hydroxyethyl cellulose are first mixed, and then aminosulfonate water reducer and 50% of water are added and mixed to obtain a primary mixture; then fine aggregate, coarse aggregate and the remaining 50% of water are mixed, added to the primary mixture, and the material can be discharged after stirring evenly.

[0065] Example 3

[0066] This embodiment provides a permeable concrete and a preparation method thereof, wherein the raw materials for preparing the permeable concrete include the following components by weight:

[0067]

[0068]

[0069] The fine aggregate is artificial sand with a particle size of 3.5 to 4.75 mm, and the coarse aggregate is crushed stone with a particle size of 4.76 to 9.5 mm. The water-cement ratio is 0.20. The preparation process of carbon nanotube-modified carbon fiber refers to Example 1. Hydrophobically modified hydroxyethyl cellulose was purchased from Ashland, model HE10K.

[0070] The preparation method of the above-mentioned permeable concrete comprises:

[0071] According to the above weight proportions, silicate cement, fly ash, carbon nanotube-modified carbon fiber and hydrophobically modified hydroxyethyl cellulose are first mixed, and then aminosulfonate water reducer and 50% of water are added and mixed to obtain a primary mixture; then fine aggregate, coarse aggregate and the remaining 50% of water are mixed, added to the primary mixture, and the material can be discharged after stirring evenly.

[0072] Example 4

[0073] This embodiment provides a permeable concrete and a preparation method thereof, wherein the raw materials for preparing the permeable concrete include the following components by weight:

[0074]

[0075] The fine aggregate is artificial sand with a particle size of 3.5 to 4.75 mm, and the coarse aggregate is crushed stone with a particle size of 4.76 to 9.5 mm. The preparation process of carbon nanotube-modified carbon fiber refers to Example 1, and the hydrophobically modified hydroxyethyl cellulose is purchased from Ashland, model HE10K.

[0076] The preparation method of the above-mentioned permeable concrete comprises:

[0077] According to the above weight proportions, silicate cement, fly ash, carbon nanotube-modified carbon fiber and hydrophobically modified hydroxyethyl cellulose are first mixed, and then aminosulfonate water reducer and 50% of water are added and mixed to obtain a primary mixture; then fine aggregate, coarse aggregate and the remaining 50% of water are mixed, added to the primary mixture, and the material can be discharged after stirring evenly.

[0078] Example 5

[0079] This embodiment provides a permeable concrete and a preparation method thereof, wherein the raw materials for preparing the permeable concrete include the following components by weight:

[0080]

[0081] The fine aggregate is artificial sand with a particle size of 3.5 to 4.75 mm, and the coarse aggregate is crushed stone with a particle size of 4.76 to 9.5 mm. The preparation process of carbon nanotube-modified carbon fiber refers to Example 1, and the hydrophobically modified hydroxyethyl cellulose is purchased from Ashland, model HE10K.

[0082] The preparation method of the above-mentioned permeable concrete comprises:

[0083] According to the above weight proportions, silicate cement, fly ash, carbon nanotube-modified carbon fiber and hydrophobically modified hydroxyethyl cellulose are first mixed, and then aminosulfonate water reducer and 50% of water are added and mixed to obtain a primary mixture; then fine aggregate, coarse aggregate and the remaining 50% of water are mixed, added to the primary mixture, and the material can be discharged after stirring evenly.

[0084] Comparative Example 1

[0085] This comparative example provides a permeable concrete and a preparation method thereof. The difference between the comparative example and Example 1 is that the carbon fibers are not modified with carbon nanotubes, and the rest are the same. The permeable concrete is prepared from the following raw materials, calculated by weight:

[0086]

[0087] The fine aggregate is artificial sand with a particle size of 3.5 to 4.75 mm, and the coarse aggregate is crushed stone with a particle size of 4.76 to 9.5 mm. The carbon fiber length is about 8.5 to 9.5 mm, and the hydrophobically modified hydroxyethyl cellulose was purchased from Ashland, model HE10K.

[0088] The preparation method of the above-mentioned permeable concrete comprises:

[0089] According to the above weight proportions, first mix the silicate cement, fly ash, carbon fiber and hydrophobically modified hydroxyethyl cellulose, then add the aminosulfonate water reducer and 50% of water, mix to obtain a primary mix; then mix the fine aggregate, coarse aggregate and the remaining 50% of water, add the primary mix, stir evenly and then discharge.

[0090] Comparative Example 2

[0091] This comparative example provides a permeable concrete and a preparation method thereof, which differs from Example 1 in that no carbon nanotube-modified carbon fibers are added, and the rest are the same. The permeable concrete is prepared from the following raw materials, calculated by weight:

[0092]

[0093] The fine aggregate is artificial sand with a particle size of 3.5 to 4.75 mm, and the coarse aggregate is crushed stone with a particle size of 4.76 to 9.5 mm. The hydrophobically modified hydroxyethyl cellulose was purchased from Ashland, model HE10K.

[0094] The preparation method of the above-mentioned permeable concrete comprises:

[0095] According to the above weight proportions, first mix the Portland cement, fly ash and hydrophobically modified hydroxyethyl cellulose, then add the aminosulfonate water reducer and 50% of water, mix to obtain a primary mix; then mix the fine aggregate, coarse aggregate and the remaining 50% of water, add the primary mix, stir evenly and then discharge.

[0096] Comparative Example 3

[0097] This comparative example provides a permeable concrete and a preparation method thereof. The difference between the comparative example and Example 1 is that the carbon nanotube-modified carbon fibers are replaced with carboxylated multi-walled carbon nanotubes and carbon fibers, and the remaining components are the same. The permeable concrete is prepared from the following raw materials, calculated by weight:

[0098]

[0099] The fine aggregate is artificial sand with a particle size of 3.5 to 4.75 mm, and the coarse aggregate is crushed stone with a particle size of 4.76 to 9.5 mm; the carbon fiber was purchased from Dongyi Yang (Jinan) New Materials Co., Ltd., with a length of about 8.5 to 9.5 mm; the carboxylated multi-walled carbon nanotubes were purchased from Beijing Dekedaojin Technology Co., Ltd., model CNT205, with an outer diameter of 20 to 30 nm, a length of about 15 μm, and a purity of ≥98%; the hydrophobically modified hydroxyethyl cellulose was purchased from Ashland, model HE10K.

[0100] The preparation method of the above-mentioned permeable concrete comprises:

[0101] According to the above weight proportions, silicate cement, fly ash, carbon fiber, carboxylated multi-walled carbon nanotubes and hydrophobically modified hydroxyethyl cellulose are first mixed, and then aminosulfonate water reducer and 50% of water are added and mixed to obtain a primary mixture; then fine aggregate, coarse aggregate and the remaining 50% of water are mixed, added to the primary mixture, and the material can be discharged after stirring evenly.

[0102] Comparative Example 4

[0103] This comparative example provides a permeable concrete and a preparation method thereof, which differs from Example 1 in that the hydroxyethyl cellulose is not hydrophobically modified, and the rest of the ingredients are the same. The permeable concrete is prepared from the following raw materials, calculated by weight:

[0104]

[0105] The fine aggregate is artificial sand with a particle size of 3.5 to 4.75 mm, and the coarse aggregate is crushed stone with a particle size of 4.76 to 9.5 mm. The preparation method of carbon nanotube-modified carbon fiber refers to Example 1. Hydroxyethyl cellulose was purchased from Ashland, model PLUS 330.

[0106] The preparation method of the above-mentioned permeable concrete comprises:

[0107] According to the above weight proportions, first mix the silicate cement, fly ash, carbon nanotube-modified carbon fiber and hydroxyethyl cellulose, then add aminosulfonate water reducer and 50% of water, mix to obtain a primary mixture; then mix the fine aggregate, coarse aggregate and the remaining 50% of water, add the primary mixture, stir evenly and then discharge.

[0108] Comparative Example 5

[0109] This comparative example provides a permeable concrete and a preparation method thereof, which differs from Example 1 in that no hydrophobically modified hydroxyethyl cellulose is added, and the rest is the same. The permeable concrete is prepared from the following raw materials, calculated by weight:

[0110]

[0111]

[0112] The fine aggregate is artificial sand with a particle size of 3.5 to 4.75 mm, and the coarse aggregate is crushed stone with a particle size of 4.76 to 9.5 mm. The preparation method of carbon nanotube-modified carbon fiber refers to Example 1.

[0113] The preparation method of the above-mentioned permeable concrete comprises:

[0114] According to the above weight proportions, first mix the silicate cement, fly ash and carbon nanotube modified carbon fiber, then add aminosulfonate water reducer and 50% of water, mix to obtain a primary mixture; then mix the fine aggregate, coarse aggregate and the remaining 50% of water, add the primary mixture, stir evenly and then discharge.

[0115] Comparative Example 6

[0116] This comparative example provides a permeable concrete and a preparation method thereof, which differs from Example 1 in that no fine aggregate is added, and the rest is the same. The permeable concrete is prepared from the following raw materials, calculated by weight:

[0117]

[0118] The coarse aggregate is crushed stone with a particle size of 4.76 to 9.5 mm. The preparation process of carbon nanotube-modified carbon fibers is similar to that of Example 1. Hydrophobically modified hydroxyethyl cellulose was purchased from Ashland, model number HE10K.

[0119] The preparation method of the above-mentioned permeable concrete comprises:

[0120] According to the above weight proportions, first mix the silicate cement, fly ash, carbon nanotube-modified carbon fiber and hydrophobically modified hydroxyethyl cellulose, then add aminosulfonate water reducer and 50% of water, mix to obtain a primary mixture; then mix the coarse aggregate and the remaining 50% of water, add the primary mixture, stir evenly and then discharge.

[0121] Test Example 1: Compressive Strength

[0122] This test example tests the compressive strength of the permeable concrete of Examples 1 to 5 and Comparative Examples 1 to 6. The specific method is as follows: First, refer to the preparation method of Example 1 to mix the raw materials for permeable concrete evenly, then make a 20cm×20cm×20cm sample, and finally refer to JTG 3420-2020 "Test Procedures for Cement and Cement Concrete in Highway Engineering" Section 5.2 Summary "T 0553-2005 Cement Concrete Compressive Strength Test Method" to test the 28d compressive strength (MPa) of permeable concrete. Three replicates are performed in each group, and the average value is taken. The higher the compressive strength, the better the compressive performance. The compressive strength test results are shown in Table 1.

[0123] Table 1: Compressive strength test results

[0124] - Compressive strength Example 1 65.2MPa Example 2 67.8MPa Example 3 62.4MPa Example 4 63.7MPa Example 5 69.5MPa Comparative Example 1 54.0MPa Comparative Example 2 45.7MPa Comparative Example 3 62.1MPa Comparative Example 4 61.8MPa Comparative Example 5 59.3MPa Comparative Example 6 42.7MPa

[0125] The test results show that the concrete material prepared using the permeable concrete formula of the present invention has excellent compressive strength of more than 62.4 MPa. Compared with Example 1, when carbon nanotube-modified carbon fibers and hydrophobically modified hydroxyethyl cellulose are added and a polycarboxylic acid-based water reducer is used, the compressive strength is as high as 69.5 MPa, which is 6.4% higher than that of aminosulfonate water reducer. It is speculated that this is related to the water-reducing and dispersion-promoting effects. The polycarboxylic acid-based water reducer has a long side chain with a large molecular weight and can ionize strong polar groups such as hydroxyl, carboxyl and sulfonic acid groups in aqueous solution. These strong polar groups can be directly adsorbed on the surface of the carbon nanotube-modified carbon fibers, which helps to improve the surface hydrophobicity of the carbon nanotube-modified carbon fibers. At the same time, it also increases the mutual repulsion between the carbon nanotube-modified carbon fibers, thereby improving the dispersion.

[0126] Compared with Example 1, the carbon fibers in Comparative Example 1 were not modified, and Comparative Example 2 did not add carbon nanotube-modified carbon fibers. The results showed that their compressive strength decreased by 17.18% and 29.9%, respectively, indicating that carbon nanotube-modified carbon fibers can significantly improve the compressive strength of permeable concrete materials. In Comparative Example 3, the carbon nanotubes and carbon fibers were not coupled, and their compressive strength decreased. This is presumably related to changes in the overall structure of the matrix. Typically, carbon fibers have a smooth surface and few active groups, resulting in poor adhesion to the matrix. After modification with carbon nanotubes, their surface roughness increases, which helps improve their contact with cement and thus improves the overall compressive strength.

[0127] Compared with Example 1, the hydroxyethyl cellulose in Comparative Example 4 was not modified, and Comparative Example 5 did not add hydrophobically modified hydroxyethyl cellulose. The results showed that the compressive strength also showed varying degrees of decline, indicating that the addition of hydrophobically modified hydroxyethyl cellulose can also improve the compressive strength to a certain extent. Comparative Example 6 did not add fine aggregate, and the results showed a significant decrease in compressive strength. This is presumably related to the decrease in stress between aggregates. Fine aggregate can effectively fill the gaps left by larger aggregates, reducing the internal voids of permeable concrete, thereby increasing the degree of interlocking between aggregates. This allows for effective stress transfer between aggregates, resulting in a more stable structure, greater cohesiveness of the cementitious material, and greater compressive strength.

[0128] Test Example 2: Water Permeability and Blockage Test

[0129] This test example tests the anti-clogging performance of the permeable concrete of Examples 1 to 5 and Comparative Examples 1 to 6. The specific method is as follows:

[0130] (1) Initial water permeability coefficient test: First, refer to the preparation method of Example 1 to mix the raw materials for permeable concrete evenly, and then make 15 cm × 15 cm × 5 cm samples, with 5 pieces in each group. Finally, refer to JTG 3420-2020 "Test Procedures for Cement and Cement Concrete in Highway Engineering" Section 5.5 Summary on "T0586-2020 Cement Concrete Water Permeability Coefficient Test Method". The test uses 20°C water temperature as the standard temperature. The larger the water permeability coefficient of the sample, the better the water permeability of the product.

[0131] (2) Residual Permeability Test: Permeable concrete blocks were used as road blocks. After 36 months of exposure to traffic, weather, and natural conditions, the residual permeability was tested and the residual permeability was calculated. The test results are shown in Table 3.

[0132] Table 2: Anti-clogging performance test results

[0133]

[0134]

[0135] From the above results, it can be seen that the permeable concrete material prepared by the present invention has a good permeability coefficient, and the initial permeability coefficient is above 4.65 mm / s. When prepared using the formula of Example 1, its initial permeability coefficient can reach 4.82 mm / s, and after 36 months of natural clogging, its residual permeability is maintained at above 90.66%, indicating that the permeable concrete material of the present invention has an excellent anti-clogging effect, can reduce the degree of material scouring, and has good durability.

[0136] Compared to Example 1, the carbon fibers in Comparative Example 1 were not modified, and Comparative Example 2 did not add carbon nanotube-modified carbon fibers. While the initial permeability coefficient was similar to that of Example 1, the residual permeability decreased significantly over time, presumably due to a decrease in compressive strength. Permeable concrete materials with low compressive strength have relatively loose cement particles, which can easily lead to erosion of particulate matter. Furthermore, in Comparative Example 3, the carbon nanotubes and carbon fibers were not coupled, and the results showed a decrease in residual permeability, presumably due to the hydrophilicity and low compressive strength of the carboxylated multi-walled carbon nanotubes.

[0137] Compared with Example 1, the hydroxyethyl cellulose in Comparative Example 4 was not modified, and Comparative Example 5 did not add hydrophobically modified hydroxyethyl cellulose, showing that its residual water permeability was significantly reduced, only about 74%, which is presumably related to the poor scour resistance of the permeable concrete material. For example, in Comparative Example 4, unmodified hydroxyethyl cellulose was used. Usually, hydroxyethyl cellulose molecular chains carry a large number of hydroxyl groups, which makes it very easy to form intermolecular hydrogen bonds with water molecules in solution, making it have excellent hydrophilicity. In the process of preparing permeable concrete, although the excellent hydrophilicity can improve the wrapping effect of cement on aggregate, it is not conducive to resisting rainwater scouring. After hydrophobic modification, it helps to form a loose protective film on the surface of cement particles, slowing down the scouring of the cement particle surface, thereby preventing blockage.

[0138] In summary, the present invention provides a permeable concrete, a preparation method thereof, and an application thereof. The permeable concrete effectively improves the compressive strength and water permeability coefficient of the permeable concrete by rationally combining raw materials such as cement, fly ash, aggregate, water reducer, carbon nanotube-modified carbon fiber, and hydrophobically modified hydroxyethyl cellulose. At the same time, the permeable concrete material obtained has excellent anti-clogging effect, can avoid being affected by excessive erosion by rainwater and affecting durability, and can be widely used in urban road construction.

[0139] While the embodiments of the present invention have been described in detail above, the present invention is not limited to the embodiments described above. Various modifications may be made within the scope of knowledge possessed by a person skilled in the art without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof may be combined with one another unless there is a conflict.

Claims

1. A permeable concrete, characterized in that: The raw materials for preparation include the following components in parts by weight: 80-120 parts of cement, 10-15 parts of fly ash, 75-150 parts of fine aggregate, 300-500 parts of coarse aggregate, 5-10 parts of water reducer, 5-10 parts of carbon nanotube modified carbon fiber, 2-8 parts of hydrophobically modified hydroxyethyl cellulose and 16-30 parts of water; The particle size of the fine aggregate is 3.5 to 4.75 mm, the particle size of the coarse aggregate is 4.76 to 9.5 mm, and the water-cement ratio of the permeable concrete is 0.2 to 0.

25. The carbon nanotube-modified carbon fiber is obtained by chemically grafting carbon nanotubes onto the surface of the carbon fiber using a coupling agent, and the coupling agent is hexamethylene diisocyanate and / or 4,4'-methylenebis(phenyl isocyanate).

2. The permeable concrete according to claim 1, characterized in that The cement is silicate cement, and the strength grade of the silicate cement is 42.5, 42.5R, 52.5 or 52.5R.

3. The permeable concrete according to claim 1, characterized in that The fine aggregate is selected from at least one of artificial sand, lake sand, mountain sand, and desalinated sea sand; and / or the coarse aggregate includes crushed stone.

4. The permeable concrete according to claim 1, characterized in that The water reducer is selected from at least one of polycarboxylic acid water reducers, naphthalene water reducers, anthracene water reducers, aminosulfonate water reducers, and ligninsulfonate water reducers.

5. The permeable concrete according to claim 4, characterized in that: The water reducer is a polycarboxylic acid water reducer.

6. The permeable concrete according to claim 1, characterized in that: The length of the carbon nanotube-modified carbon fiber is 8 to 10 mm; and / or the diameter of the single fiber of the carbon nanotube-modified carbon fiber is 7 to 8 μm.

7. A method for preparing permeable concrete according to any one of claims 1 to 6, characterized in that: The preparation method comprises mixing the raw materials.

8. Use of the permeable concrete according to any one of claims 1 to 6 in the preparation of building or pavement materials.

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