Metamaterial concrete, preparation method thereof and rigid-flexible composite pavement structure

Abstract

The invention discloses metamaterial concrete, a preparation method thereof and a rigid-flexible composite pavement structure, and belongs to the technical field of road construction. The metamaterial concrete disclosed by the invention is provided with a Cartesian oval line hole, the Cartesian oval line hole is filled with a phase change material, under a two-dimensional Cartesian coordinate system, the expression of the Cartesian oval line is as follows: (x2 + y2) 2 + 2a2 (y2-x2) + a4-b4 =, in the formula, a is 3.76-7.51 mm; and b ranges from 4.19 mm to 8.39 mm. The metamaterial concrete disclosed by the invention has the performance of autonomously regulating and controlling the temperature and also has the characteristic of negative Poisson's ratio, and when the metamaterial concrete is applied to a rigid-flexible composite pavement structure, the compression resistance and the impact resistance of the pavement structure can be enhanced, the overall strength, the toughness and the crack resistance of the pavement can be improved, and finally, the design of a cool pavement is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of road construction, and in particular to a metamaterial concrete and a preparation method thereof, and a rigid-flexible composite pavement structure. Background Art

[0002] At present, most of my country's high-grade highways use asphalt pavement, which is widely popular due to its advantages such as convenient construction and maintenance, comfortable driving, long tire service life and low noise. Among the existing high-performance pavement structures, the rigid-flexible composite pavement structure paves "flexible" asphalt mixture on a "rigid" concrete slab, combining the advantages of cement pavement and asphalt pavement, and has the characteristics of strong bearing capacity, high durability, and excellent road performance. It can improve rutting, anti-skid durability and reflective cracks to a certain extent. However, under heavy traffic conditions, asphalt pavements are prone to rutting, cracks, subsidence, potholes and other diseases, which seriously affect the anti-skid, durability and safety performance of the road. In the high temperature environment in summer, the surface temperature of the asphalt pavement can reach 70℃. The excessively high temperature increases the viscous flow of asphalt, aggravates the occurrence of rutting and other diseases on the pavement, and accelerates the photo-oxidation aging reaction of asphalt, making it brittle and losing its bonding effect, further inducing problems such as pavement cracking. This not only affects the service performance of the pavement, but also aggravates the urban heat island effect, increases urban energy consumption and greenhouse gas emissions, and leads to a vicious cycle.

[0003] The modulus and shear strength of asphalt mixtures are greatly affected by temperature. In high-temperature areas, a slight increase in temperature will lead to a sharp drop in the performance of the mixture. The contact stress between the tire and the road surface will cause loads to be generated, and under the action of repeated loads, rutting and other defects will be formed, affecting driving safety. In addition, the strength of traditional concrete slabs is relatively low. In order to meet high load requirements, it is often necessary to design a larger cross-sectional size, resulting in a high amount of cement materials and heavy weight, which puts higher requirements on the roadbed design and is not conducive to achieving energy conservation, emission reduction, and green and low-carbon goals. At the same time, traditional concrete slabs cannot achieve "autonomous" temperature control, and it is difficult to achieve the effect of a "cool" road surface. Therefore, it is urgent to develop a high-performance asphalt pavement structure that not only meets the requirements of heavy-duty traffic, but also has temperature control capabilities. Summary of the invention

[0004] In view of the deficiencies of the above existing technologies, the present invention provides a metamaterial concrete and a preparation method thereof, and a rigid-flexible composite pavement structure. The metamaterial concrete of the present invention has the performance of autonomous temperature regulation and also has the characteristic of negative Poisson's ratio. When applied to a rigid-flexible composite pavement structure, it can enhance the compression resistance and impact resistance of the pavement structure and improve the overall strength, toughness and crack resistance of the pavement. This is specifically achieved through the following technologies.

[0005] A metamaterial concrete has a Cassini oval hole, and the Cassini oval hole is filled with a phase change material. In a two-dimensional Cartesian coordinate system, the expression of the Cassini oval is:

[0006] (x 2 +y 2 ) 2 +2a 2 (y 2 -x 2 )+a 4 -b 4 =0,

[0007] In the formula, a is 3.76-7.51mm; b is 4.19-8.39mm.

[0008] In the expression of the Cassini oval, a and b are the two control parameters of the Cassini oval. (a,0) and (-a,0) are the two foci of the curve, and b 2 It is the product of the distances from any point on the curve to the two foci.

[0009] Phase change materials have large latent heat of phase change and excellent heat absorption and heat release properties. The phase change material selected by the present invention can absorb a large amount of heat in a high temperature environment and store the heat energy through phase change, thereby effectively reducing the temperature of the road surface and improving its high temperature stability; at the same time, in a low temperature environment, it can also release the stored heat to prevent the road surface temperature from being too low, which helps to improve the road surface's crack resistance. The metamaterial concrete of the present invention has Cassini oval line holes and negative Poisson's ratio characteristics. The metamaterial concrete prepared together with the phase change material has good strength and toughness, so that the road surface can effectively disperse stress and reduce stress concentration when it is subjected to heavy pressure and impact, thereby significantly improving the road surface's crack resistance and reducing the generation and expansion of cracks.

[0010] Furthermore, the relationship between a and b is b / a>1.

[0011] Furthermore, the Cassini oval holes are arranged on the metamaterial concrete in such a manner that the long axes of two adjacent Cassini oval holes are perpendicular to each other.

[0012] Furthermore, the minimum distance m between two adjacent Cassini oval holes is 14.98-22.49 mm.

[0013] Furthermore, four quarter Cassini oval holes (one at each of the four corners of the cell), two half Cassini oval holes (separated by the long axis of the Cassini oval, located on the left and right sides of the cell), two half Cassini oval holes (separated by the short axis of the Cassini oval, located on the top and bottom sides of the cell) and one complete Cassini oval hole (located in the middle of the cell) constitute a cell (e.g.Figure 4 shown).

[0014] Furthermore, the side length L of the unit cell is 60 mm.

[0015] Furthermore, the phase change material includes at least one of paraffin, polyethylene glycol phase change material, and hydrated salt phase change material.

[0016] The preparation method of the above-mentioned metamaterial concrete comprises the following steps:

[0017] preparing concrete with Cassini oval holes, allowing it to stand, and performing curing to obtain precast concrete;

[0018] The precast concrete is vacuum impregnated with a liquid phase change material, left to stand at room temperature, and excess phase change material is removed to obtain metamaterial concrete.

[0019] Furthermore, an aluminum plate is arranged around the precast concrete to prevent leakage of the phase change material.

[0020] A rigid-flexible composite pavement structure comprises a metamaterial concrete layer, wherein the metamaterial concrete layer is composed of the above-mentioned metamaterial concrete.

[0021] Furthermore, the upper part of the metamaterial concrete layer is an asphalt surface layer.

[0022] Furthermore, the rigid-flexible composite pavement structure is composed of a soil base, a lime soil layer, a cement-stabilized crushed stone base layer, a meta-material concrete layer and an asphalt surface layer from bottom to top.

[0023] The design of the metamaterial concrete of the present invention not only makes the pavement structure have high strength and high toughness, but also maintains excellent performance in temperature changes, greatly extending the service life of the pavement. The metamaterial concrete of the present invention gives full play to the advantages of concrete materials with negative Poisson's ratio characteristics and phase change materials, and provides a new idea for the preparation of a rigid-flexible composite pavement structure that is both strong and durable and adaptable to temperature changes.

[0024] The metamaterial concrete layer of the present invention can reduce the amount of cement while ensuring the strength and durability of the concrete. The water-cement ratio is reduced by using a high-efficiency water reducer and other admixtures. The inventor has done a large number of experiments to confirm that the water-cement ratio is significantly reduced after using the optimized cement content. In the metamaterial concrete layer of the present invention, the phase change material can absorb or release heat. When the ambient temperature changes, the phase change material will undergo a phase change (such as from solid to liquid or vice versa), thereby adjusting the temperature of the concrete. This temperature regulation effect can reduce the stress changes caused by temperature, thereby reducing the risk of cracking of concrete. In addition, when cracks appear, the phase change material can be filled into the cracks through its phase change characteristics to reduce the further expansion of the cracks. The liquid phase change material can penetrate into the cracks and solidify in the subsequent temperature changes to form a stable solid structure, thereby playing a role in blocking the cracks.

[0025] Compared with the prior art, the present invention is beneficial in that:

[0026] 1. The present invention proposes a rigid-flexible composite pavement structure based on metamaterials, which uses metamaterial concrete as the base material, combines Cassini oval holes, and optimizes the concrete material mix ratio to change the microstructure of the concrete material, reduce the water-cement ratio, and thus improve its density and uniformity; this optimization not only enhances the strength and toughness of the material, but also improves its durability, shrinkage and creep, crack self-healing, and low-carbon environmental protection performance; through these improvements, the performance of the pavement structure in all aspects has been significantly improved, further improving its overall quality and service life;

[0027] 2. The present invention proposes a rigid-flexible composite pavement structure based on metamaterials, including the metamaterial concrete of the present invention, whose unique structure enables it to shrink laterally when under pressure, and has a significant negative Poisson's ratio, thereby enhancing the compression resistance and impact resistance of the metamaterial concrete, thereby improving the overall strength and toughness of the pavement; in addition, this design enables the pavement to more effectively disperse stress and reduce stress concentration when subjected to heavy pressure and impact, thereby significantly improving the pavement's crack resistance and reducing the generation and expansion of cracks;

[0028] 3. The present invention uses phase change materials, which have a large latent heat of phase change. For example, paraffin phase change materials will undergo a phase change in a high temperature environment, melting from a solid state to a liquid state, absorbing the heat flow from the metamaterial concrete and entering the pavement structure, while its own temperature remains almost unchanged. This process effectively reduces the heating rate and high temperature peak of the asphalt pavement during high temperature periods. When the temperature drops, the phase change material releases the stored heat and conducts the heat from the metamaterial concrete to the outside world, thereby regulating the pavement temperature. This regulation mechanism significantly reduces the diseases of asphalt pavements under high temperature conditions, such as rutting and aging and brittleness of asphalt. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A schematic diagram of the Cassini oval aperture of the present invention;

[0030] Figure 2 A schematic diagram of the metamaterial concrete of the present invention;

[0031] Figure 3 A schematic diagram of a rigid-flexible composite pavement structure based on metamaterial concrete according to the present invention;

[0032] Figure 4 Schematic diagram of a unit cell of metamaterial concrete;

[0033] Figure 5 It is a three-dimensional structural diagram of the concrete rubber mold of the present invention;

[0034] Figure 6 It is a three-dimensional structural diagram of the concrete mold of the present invention;

[0035] Figure 7 It is a three-dimensional structural diagram of the metamaterial concrete of the present invention;

[0036] In the figure: 1. Concrete; 2. Phase change material; 3. Soil base; 4. Lime soil layer; 5. Cement-stabilized gravel base layer; 6. Super material concrete layer; 7. Asphalt surface layer. DETAILED DESCRIPTION

[0037] In order to further illustrate the present invention, the technical solution provided by the present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments, but they should not be understood as limiting the protection scope of the present invention.

[0038] like Figure 1 As shown. The Cassini oval hole, in the two-dimensional Cartesian coordinate system, the expression of the Cassini oval is (x 2 +y 2 ) 2 +2a 2 (y 2 -x 2 )+a 4 -b 4 = 0, which can be specifically described as the trajectory of a moving point P(x, y) in the plane whose product of distances to two fixed points F1(a, 0) and F2(-a, 0) is a constant. Among them, a and b are two important control parameters of the Cassini oval. A peanut-shaped hole is constructed by regulating L (the side length of the unit cell), m (the minimum distance between adjacent holes), and b / a>1 (shape control parameter). Figure 4As shown, in the present invention, the unit cell includes four quarter Cassini oval holes (respectively at the four corners of the unit cell), two half Cassini oval holes (separated by the long axis of the Cassini oval, respectively located on the left and right sides of the unit cell), two half Cassini oval holes (separated by the short axis of the Cassini oval, respectively located on the upper and lower sides of the unit cell) and a complete Cassini oval hole (located in the middle of the unit cell).

[0039] In some examples of the present invention, a is 3.76-7.51 mm; b is 4.19-8.39 mm.

[0040] In some examples of the present invention, b / a>1.

[0041] In some examples of the present invention, the minimum distance m between two adjacent Cassini oval holes may be 14.98-22.49 mm.

[0042] In some examples of the present invention, the side length L of the unit cell may be 60 mm.

[0043] In some examples of the present invention, the porosity of the metamaterial concrete structure can be further adjusted by changing the size of the Cassini oval line holes, thereby controlling the filling amount of the phase change material.

[0044] In some examples of the present invention, the phase change material may include at least one of paraffin, polyethylene glycol phase change material, and hydrated salt phase change material.

[0045] In some examples of the present invention, the phase change material may be paraffin wax, which has the characteristics of wide phase change temperature, high energy storage density, strong energy storage capacity, no supercooling phenomenon, and also has the advantages of wide raw material sources and low price, which helps to reduce costs and improve economic efficiency.

[0046] The present invention provides an exemplary method for preparing metamaterial concrete, comprising the following steps:

[0047] S1. Using a mold to prepare concrete with Cassini oval holes, leaving it to stand and curing it, to obtain precast concrete;

[0048] S2. Vacuum-immerse the prefabricated concrete of step S1 into the liquid phase change material, leave it to stand at room temperature, remove the excess phase change material, and obtain metamaterial concrete.

[0049] In the preparation method of the present invention, the phase change material needs to submerge the precast concrete and fill up the pores of the precast concrete.

[0050] In some examples of the present invention, the standing time in step S1 may be no less than 24 hours.

[0051] In some examples of the present invention, the curing in step S1 may be a standard curing of 28 days.

[0052] In some examples of the present invention, the standing time in step S2 may be no less than 2 hours.

[0053] In some examples of the present invention, an aluminum plate may be further arranged around the precast concrete to prevent leakage of the phase change material.

[0054] The present invention also provides an exemplary rigid-flexible composite pavement structure, which comprises, from bottom to top, a soil base, a lime soil layer, a cement-stabilized crushed stone base layer, a meta-material concrete layer and an asphalt surface layer.

[0055] The technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0056] In the following specific embodiments, the preparation method of metamaterial concrete includes the following steps:

[0057] S1. Confirm the Cassini oval expression of the Cassini oval hole of the metamaterial concrete and design the mold (such as Figure 5 As shown), then use a 3D printer to print the designed mold, perform structural inspection and screening, and obtain a concrete mold;

[0058] S2, pour the silicone rubber into the concrete mold in step S1, solidify and shape, and demould after 24 hours to obtain a concrete rubber mold (such as Figure 6 As shown), continue to pour concrete, vibrate for 40 seconds to ensure the compactness of the concrete, cover with plastic wrap to reduce moisture loss, let stand for 24 hours, and after curing for 28 days, obtain precast concrete;

[0059] S3. The precast concrete in step S2 is placed in a container of suitable size, an aluminum plate is arranged around the precast concrete, and then liquid paraffin is vacuum impregnated into the container, the vacuum is maintained for 1 minute to remove bubbles, and then the container is allowed to stand at room temperature for 2 hours, and excess paraffin is removed to obtain metamaterial concrete.

[0060] Example 1

[0061] like Figure 2 As shown, in this embodiment, the Cassini oval holes on the precast concrete prepared in step S2 are arranged vertically to each other.

[0062] The expression of the Cassini oval is: (x 2 +y 2 )2 +2a 2 (y 2 -x 2 )+a 4 -b 4 =0.

[0063] Among them, a=3.76mm; b=4.19mm; m=22.49mm; L=60mm.

[0064] The three-dimensional structure diagram of the metamaterial concrete of the present invention is as follows Figure 7 shown.

[0065] Example 2

[0066] like Figure 2 As shown, in this embodiment, the Cassini oval holes on the precast concrete prepared in step S2 are arranged vertically to each other.

[0067] The expression of the Cassini oval is: (x 2 +y 2 ) 2 +2a 2 (y 2 -x 2 )+a 4 -b 4 =0.

[0068] Among them, a=5.31mm; b=5.94mm; m=19.38mm; L=60mm.

[0069] Example 3

[0070] like Figure 2 As shown, in this embodiment, the Cassini oval holes on the precast concrete prepared in step S2 are arranged vertically to each other.

[0071] The expression of the Cassini oval is: (x 2 +y 2 ) 2 +2a 2 (y 2 -x 2 )+a 4 -b 4 =0.

[0072] Among them, a=6.50mm; b=7.27mm; m=16.99mm; L=60mm.

[0073] Example 4

[0074] In this embodiment, the Cassini oval holes on the precast concrete prepared in step S2 are arranged in parallel in rows.

[0075] The expression of the Cassini oval is: (x 2 +y 2 ) 2 +2a 2 (y 2 -x 2 )+a 4 -b 4 =0.

[0076] Among them, a=7.51mm; b=8.39mm; m=14.98mm; L=60mm.

[0077] Comparative Example 1

[0078] like Figure 2 As shown, in this comparative example, the Cassini oval holes on the precast concrete prepared in step S2 are arranged perpendicular to each other.

[0079] The expression of the Cassini oval is: (x 2 +y 2 ) 2 +2a 2 (y 2 -x 2 )+a 4 -b 4 =0.

[0080] Among them, a=4.74mm; b=4.74mm; m=23.29mm; L=60mm.

[0081] Application Examples

[0082] The metamaterial concrete of Examples 1-4 and Comparative Example 1 were respectively applied to a rigid-flexible composite pavement structure. The rigid-flexible composite pavement structure comprises, from bottom to top, a soil base, a lime soil layer, a cement-stabilized crushed stone base layer, a metamaterial concrete layer, and an asphalt surface layer. Figure 3 As shown, the rigid-flexible composite pavement structures of Examples 1-4 and Comparative Example 1 all include, from bottom to top, a soil base, a lime soil layer, a cement-stabilized crushed stone base layer, a metamaterial concrete layer and an asphalt surface layer.

[0083] Temperature sensors are embedded in the interior and surface of the rigid-flexible composite pavement structures of Examples 1-4 and Comparative Example 1, respectively. Then, the rigid-flexible composite pavements of Examples 1-4 and Comparative Example 1 are placed at 70°C to monitor the temperature change of the pavement in real time. In the present invention, the temperature of traditional pavement materials and the time when cracks first appear are used as reference objects, and the temperature reduction values, peak temperature delay time and first crack delay time of Examples 1-4 and Comparative Example 1 are tested. The test results are shown in Table 1 below. Traditional pavement materials include soil base, lime soil layer, cement stabilized macadam base layer and asphalt concrete layer from bottom to top.

[0084] The rigid-flexible composite pavements of Examples 1-4 and Comparative Example 1 were subjected to fatigue tests to simulate the behavior of the pavement structure under long-term repeated loads. The test results are shown in Table 1 below.

[0085] Table 1 Test results of Examples 1-4 and Comparative Example 1

[0086] Group Temperature drop (℃) Peak temperature delay time (h) Delay time to first crack (h) Example 1 0.8 0.08 0.01 Example 2 1.5 0.13 0.05 Example 3 2.2 0.18 0.1 Example 4 3.2 0.21 0.13 Comparative Example 1 0.6 0.05 0.007

[0087] By comparing with traditional pavement materials, it was found that the temperature of the rigid-flexible composite pavement using the metamaterial concrete of the present invention was about 3.2°C lower than that of ordinary pavement, and the peak temperature delay time was about 0.21h. At the same time, fatigue tests were carried out on the metamaterial concrete to simulate the behavior of the pavement structure under long-term repeated loads. The test results show that the metamaterial concrete exhibits significantly higher fatigue life under the same stress conditions, and the time of the first crack appearance is significantly delayed. These results demonstrate the significant role of the addition of phase change materials in improving the cooling effect and crack resistance of the pavement.

[0088] The above specific embodiments describe the implementation of the present invention in detail, but the present invention is not limited to the specific details in the above embodiments. Within the scope of the claims and technical concept of the present invention, the technical solution of the present invention can be modified and changed in many simple ways, and these simple modifications all belong to the protection scope of the present invention.

Claims

1. A metamaterial concrete, characterized in that: The metamaterial concrete has a Cassini oval hole, and the Cassini oval hole is filled with a phase change material. In a two-dimensional Cartesian coordinate system, the expression of the Cassini oval is: (x 2 +y 2 ) 2 +2a 2 (y 2 -x 2 )+a 4 -b 4 =0, In the formula, a is 3.76-7.51mm; b is 4.19-8.39mm.

2. The metamaterial concrete according to claim 1, characterized in that: b / a>1.

3. The metamaterial concrete according to claim 1, characterized in that: The Cassini oval holes are arranged on the metamaterial concrete in such a manner that the long axes of two adjacent Cassini oval holes are perpendicular to each other.

4. The metamaterial concrete according to claim 3, characterized in that: The minimum distance m between two adjacent Cassini oval apertures is 14.98-22.49 mm.

5. The metamaterial concrete according to claim 1, characterized in that: A unit cell consists of four quarter Cassini oval holes, two half Cassini oval holes separated by the major axis of the Cassini oval, two half Cassini oval holes separated by the minor axis of the Cassini oval, and one complete Cassini oval hole.

6. The metamaterial concrete according to claim 1, characterized in that: The phase change material includes at least one of paraffin, polyethylene glycol, and hydrated salt phase change materials.

7. The method for preparing the metamaterial concrete according to any one of claims 1 to 6, characterized in that: The following steps are involved: preparing concrete with Cassini oval holes, allowing it to stand, and performing curing to obtain precast concrete; The precast concrete is vacuum impregnated with a liquid phase change material, left to stand at room temperature, and excess phase change material is removed to obtain metamaterial concrete.

8. A rigid-flexible composite pavement structure, characterized in that: It comprises a metamaterial concrete layer, wherein the metamaterial concrete layer is composed of the metamaterial concrete according to any one of claims 1 to 5.

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