Toughening design and preparation method of ductile matrix concrete

Abstract

The invention provides a toughening design and a preparation method of ductile matrix concrete, the concrete comprises a ductile matrix and aggregate, and the ductile matrix is selected from a rubber modified fiber reinforced composite material. According to the invention, the fiber reinforced composite material is used as a concrete matrix and is subjected to fracture mechanical modification by adopting rubber, so that a ductile matrix with saturated multi-seam cracking and high-limit tensile strain is obtained. The ductile matrix can cooperate with aggregate to improve the mechanical and physical properties of concrete and effectively disperse microscopic damage under the action of external load, so that the concrete has higher bending toughness and good tensile strength to improve the structural safety and durability. The design idea and method of traditional rubber concrete are fundamentally changed, and the application value of rubber in high-performance building materials can be improved. The method for preparing the concrete is easy and convenient to operate, large-scale production can be achieved by means of existing concrete stirring and production equipment, and the application value is high.

Description

Technical Field

[0001] This application relates to the field of concrete materials. Specifically, this application relates to the toughening design and preparation method of ductile matrix concrete. Background Art

[0002] As the solid material with the largest global consumption, concrete has laid the foundation for the development of modern infrastructure. However, as a brittle material, concrete has the characteristics of high compressive strength but low tensile strength, and is extremely prone to cracking during service. Cracks provide a convenient channel for the intrusion of harmful media, thus accelerating the corrosion of steel bars and the destruction process of the material itself, and seriously reducing its mechanical integrity. Engineering practice shows that most durability problems of concrete structures originate from improper crack control measures and premature cracking of materials, resulting in its actual life often being shorter than the designed life, which limits the sustainable development of the entire life cycle of infrastructure.

[0003] In the current concrete material system, the mesoscopic structure of the material mainly consists of two parts. First, the cementitious material and water form cementitious ability through a series of hydration reactions to provide strength for the material. Second, the aggregates, including coarse aggregates and fine aggregates, are combined in a certain grading manner to play a skeleton role. Aggregates have a positive impact on various technical properties of concrete, such as shrinkage and wear, and reduce the brittleness of concrete through the bridging, deflection, retention, etc. of cracks, making it different from cement paste and showing a special quasi-brittle characteristic.

[0004] However, the degree of improvement in the crack resistance of concrete materials provided by aggregates is very limited, which is difficult to cope with the complex service environment in actual engineering and cannot meet the requirements for the durability of materials and structures. Therefore, how to improve the crack resistance of concrete still needs to be studied at present. Summary of the Invention

[0005] This application aims to solve at least to some extent the technical problems existing in the prior art. For this purpose, this application proposes concrete and its preparation method. This application uses fiber-reinforced composite materials as the concrete matrix, and uses rubber to modify its fracture mechanics to promote multi-crack cracking and obtain a ductile matrix with high ductility. This ductile matrix can cooperate with aggregates to improve the mechanical and physical properties of concrete, effectively disperse micro-damage under external loads, so that the concrete has higher flexural toughness, and at the same time has good tensile strength, improving the structural safety and durability. In addition, the application of rubber to concrete is also beneficial to improving the application value of rubber. The method for preparing concrete in this application is simple to operate and can be mass-produced relying on existing concrete mixing and production equipment, with high application value.

[0006] It should be noted that this application is based on the inventor's discovery and understanding of the following facts and problems:

[0007] In the early stage, the inventors attempted (hereinafter referred to as "prior art") to utilize the good ductility of rubber to improve the brittleness of concrete. The specific operation is as follows: First, dry materials such as rubber particles, cement, and aggregates are dry-mixed, and then the obtained dry-mixed material is mixed with water to make concrete. After testing, although rubber can improve the brittleness of concrete to a certain extent, when adjusting the amount of rubber added, the bending behavior of the concrete is basically similar and no obvious change occurs. This indicates that its toughening effect on concrete is limited. This is because the rubber particles are small in volume and low in elastic modulus, and it is difficult to play a significant crack resistance role during the process of crack initiation and propagation in concrete. In addition, under the condition of a large amount of addition, rubber will cause the tensile strength of concrete to decrease, limiting its scope of application.

[0008] In view of this, the inventors incorporated fibers into the cement matrix to obtain a fiber-reinforced composite material, and then incorporated rubber particles to conduct fracture mechanics modification on it to obtain a ductile matrix. Then, the ductile matrix is mixed with aggregates to make concrete. When the concrete is damaged, the hydrophobic property of the rubber particles is utilized to play the role of artificial defects, inducing the matrix to generate more saturated and uniform multi-crack cracking. While in the prior art, the rubber particles were simply mixed with other materials, and the role played by the rubber was to passively respond to the initiation and propagation of cracks, expecting to absorb mechanical energy through the self-elastic deformation of the rubber particles. At the same time, in the prior art, to balance the deformation energy absorption effect of the rubber particles and the strength reduction effect on the concrete, a trial-and-error method was used to determine the rubber content in the concrete. It can be seen that there is an essential difference between the prior art and the use of rubber particles in this application to "induce multi-crack cracking in the matrix". By inducing multi-crack cracking in the matrix, the cracks are avoided from concentrating on a main crack but are dispersed into multiple tiny cracks, thereby dispersing the macroscopic deformation borne by the material. The strain borne by each micro-crack is relatively small, and the opening speed of a single crack will also slow down, thus playing a role in inhibiting the propagation of the main crack, which is manifested as a multi-crack kinking and retention phenomenon in concrete, and can effectively improve the fracture energy of the concrete and improve the behavior of the softening section. The deformation ability of the matrix helps to reduce the tendency of stress or strain concentration, enabling the material to adapt to the externally applied deformation at the mesoscopic and microscopic levels while maintaining good mechanical and geometric integrity and providing sufficient remaining bearing capacity. At the same time, the toughening effect provided by the multi-crack kinking and retention of the matrix is significantly greater than the toughening effect provided by the self-deformation of the rubber particles, promoting the toughening efficiency of the rubber particles on the concrete material.

[0009] In addition, by introducing fibers, a bridging effect on cracks is achieved. After the rubber particles promote matrix cracking, the cracks can be effectively controlled by the fibers on the fracture surface, enabling new cracks to be induced at other positions before the material cracks. This requires the bridging effect of the fibers to cooperate with the matrix cracking process promoted by rubber modification. Moreover, as an embedded body, the aggregate delays crack development through mechanisms such as crack deflection and bridging while providing the framework of the material. Under the combined action of the three, the actual crack path is longer and effectively dispersed into multiple fine cracks, increasing the flexural toughness by at least 40% to 230%. Under the same damage conditions, the damage mode of the concrete of this application has a more significant non-linear characteristic, and the influence degrees of the mortar-aggregate interface defects and the main crack surface expansion on the material performance are relatively reduced.

[0010] In traditional rubber concrete, the process of improving the material toughness by rubber particles is usually accompanied by a reduction in material strength. This is because the toughening mechanism of rubber particles in traditional concrete mainly relies on the deformation of the rubber itself. Therefore, to improve toughness, it is necessary to increase the content of rubber particles to enhance the energy absorption capacity of the concrete. Since the strength and elastic modulus of the rubber itself are significantly lower than those of other components in the concrete (such as aggregates, cement matrix, etc.), excessive incorporation of rubber will lead to a decrease in the material density, and the rubber itself does not have the ability of gelling, and its interfacial bonding with the concrete is weak, which is prone to induce cracking under tensile stress, resulting in a significant decrease in the strength of traditional concrete. Different from traditional inventions, this application utilizes the characteristics of the low strength of the rubber itself and the insufficient bonding with the cement matrix, turning this weakness into the advantage of promoting multi-crack cracking of the composite ductile matrix, thereby increasing the ultimate tensile strain of the matrix, improving the crack width, and enhancing the material toughness. This design concept no longer pursues the effect of improving toughness by increasing the rubber content, but by coordinating the effects of fiber bridging and rubber-induced cracking, improving the matrix ductility, and then enhancing the toughness of the concrete. Therefore, this application can use a smaller rubber content to achieve the technical effect of significant toughening, thereby improving the toughening efficiency of rubber in concrete and alleviating the risk of material strength loss. In addition, the strain hardening characteristic of the ductile matrix also provides favorable conditions for strength improvement.

[0011] To this end, in one aspect of this application, a kind of concrete is proposed. According to the embodiments of this application, the concrete includes: a ductile matrix and aggregates, and the ductile matrix is selected from rubber-modified fiber-reinforced composites.

[0012] In this application, a fiber-reinforced composite material is used as the concrete matrix, and rubber is used to modify its fracture mechanics to obtain a ductile matrix with high ductility. This ductile matrix can act synergistically with the aggregate to improve the mechanical and physical properties of the concrete, effectively disperse micro-damage under external loads, so that the concrete has higher flexural toughness, and at the same time has good tensile strength, improving the structural safety and durability. In addition, this application fundamentally changes the design ideas and methods of traditional rubber concrete, which is beneficial to enhancing the application value of rubber in high-performance building materials.

[0013] According to an embodiment of the present application, the concrete may further have the following additional technical features:

[0014] According to an embodiment of the present application, the ultimate tensile strain of the ductile matrix is 3% - 15%, preferably 3% - 7%; and / or, the fracture toughness of the ductile matrix does not exceed 0.6 MPa·m 1 / 2 .

[0015] According to an embodiment of the present application, the ductile matrix includes rubber particles and fiber cement composite materials; the average particle size D of the rubber particles 50 is not greater than 1 mm, preferably 30 μm - 500 μm; the mass ratio of the rubber particles in the ductile matrix is 1% - 6%.

[0016] According to an embodiment of the present application, the fiber-reinforced composite material contains polymer fibers and a cement matrix; the polymer fibers include at least one of polypropylene, polyethylene, polyvinyl alcohol, and polyethylene terephthalate; the maximum volume ratio of the polymer fibers in the ductile matrix is 2 vol%, preferably 1.0 - 2.0 vol%; the cement matrix includes cement and mineral admixtures, the cement includes at least one of ordinary Portland cement, composite Portland cement, sulfoaluminate cement, aluminate cement, alkali-activated cement, and carbonate cement; the mineral admixtures include at least one of fly ash, slag, steel slag, limestone powder, and metakaolin; the mass ratio of the mineral admixtures to the cement is not less than 1.0, preferably 1 - 4.

[0017] According to an embodiment of the present application, the volume ratio of the ductile matrix to the aggregate is at least 3:7, preferably 4:6 - 5:5.

[0018] According to an embodiment of the present application, the aggregate is continuously graded aggregate and / or single-sized aggregate, the maximum particle size of the continuously graded aggregate is 4.75 mm - 20 mm, and the particle size D of the single-sized aggregate 50 is 4.75 mm - 2 mm.

[0019] According to an embodiment of the present application, the initial cracking strength of the ductile matrix is 1.0 MPa to 5.0 MPa, the ultimate tensile strength is 3.0 MPa to 9.0 MPa, and the ratio of the two is at most 1.0; the remaining energy of the ductile matrix to the crack tip toughness in the cement matrix is at least 1.2, preferably 40 to 60.

[0020] In another aspect of the present application, the present application provides a method for preparing the aforementioned concrete. According to an embodiment of the present application, the method includes: mixing the ductile matrix and the aggregate to obtain the concrete.

[0021] According to an embodiment of the present application, the method for preparing the ductile matrix includes: first mixing the cement matrix, rubber and polymer fibers, and then mixing the obtained mixture with water and optional additives to obtain the ductile matrix; mixing the ductile matrix with the aggregate to obtain the concrete.

[0022] Additional aspects and advantages of the present application will be given in part in the following description, become apparent in part from the following description, or be learned through the practice of the present application. Description of the Drawings

[0023] The above and / or additional aspects and advantages of the present application will become apparent and be readily understood from the description of the embodiments in conjunction with the following drawings, where:

[0024] Figure 1 Shows a physical diagram of a typical crack form in the rubber-modified ductile matrix concrete of the present application;

[0025] Figure 2 Shows a physical diagram of a typical crack form in traditional (rubber) concrete. Detailed Description of the Embodiments

[0026] The embodiments of the present application will be described in detail below. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as a limitation of the present application.

[0027] It should be noted that the terms "first" and "second" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. Further, in the description of the present application, unless otherwise specified, the meaning of "plurality" is two or more.

[0028] The endpoints and any values within the ranges disclosed herein are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be considered to be specifically disclosed herein.

[0029] As used herein, the term "comprising" or "including" is an open-ended expression, meaning it includes the content specified in this application but does not exclude other aspects.

[0030] This application provides concrete and its preparation method, which will be described in detail below respectively.

[0031] Concrete

[0032] In one aspect of this application, this application provides a kind of concrete. According to the embodiments of this application, the concrete includes: a ductile matrix and aggregates, and the ductile matrix is selected from rubber-modified fiber-reinforced composites.

[0033] This application uses fiber-reinforced composites as the concrete matrix and modifies its fracture mechanics with rubber to obtain a ductile matrix with high ductility. This ductile matrix can cooperate with aggregates to improve the mechanical and physical properties of concrete, effectively disperse micro-damage under external loads, so that the concrete has higher flexural toughness, and at the same time has good tensile strength, improving the structural safety and durability. In addition, this application fundamentally changes the design concept and method of traditional rubber concrete, which is beneficial to enhancing the application value of rubber in high-performance building materials.

[0034] According to the embodiments of this application, the ultimate tensile strain of the ductile matrix is 3% - 15%, such as 3 - 4%, 4 - 5%, 5 - 6%, 6 - 7%, 7 - 8%, 8 - 9%, 9 - 10%, 10 - 11%, 11 - 12%, 12 - 13%, 13 - 14%, 14 - 15%, preferably 3% - 7%. Thus, it can effectively improve the flexural toughness of concrete without sacrificing too much tensile strength, and to a certain extent, it improves the tensile strength, achieving a good balance between the two mechanical properties. It can not only maintain a high load-bearing capacity but also effectively disperse stress and delay crack propagation through the multi-crack cracking mechanism, thereby significantly improving the energy absorption capacity and durability. However, if the ultimate tensile strain is too large, although the ductility is enhanced, the reduction in tensile strength is relatively large and the energy absorption efficiency decreases; conversely, if the ultimate tensile strain is too small, the material shows relatively high brittleness, reduced flexural toughness, and weakened energy absorption capacity.

[0035] According to the embodiments of this application, the fracture toughness of the ductile matrix does not exceed 0.6 MPa·m1 / 2 , such as <0.1 MPa·m 1 / 2 , 0.1 - 0.2 MPa·m 1 / 2 , 0.2 - 0.3 MPa·m 1 / 2 , 0.3 - 0.4 MPa·m 1 / 2 , 0.4 - 0.5 MPa·m 1 / 2 , 0.5 - 0.6 MPa·m 1 / 2 . Thus, it is possible to effectively improve the flexural toughness of concrete without sacrificing too much of the tensile strength, and to improve the tensile strength to a certain extent, achieving a good balance between the two mechanical properties. It can not only maintain a high load-bearing capacity, but also effectively disperse stress and delay crack propagation through the multi-crack cracking mechanism, thereby significantly improving the energy absorption capacity and durability. If the fracture toughness is higher than the above range, the number of cracks in the ductile matrix will be significantly reduced, leading to a significant decrease in ductility.

[0036] According to an embodiment of the present application, the ductile matrix includes rubber particles and fiber cement composite material; the average particle size D of the rubber particles 50 is not greater than 1 mm, preferably 30 μm - 500 μm; the mass ratio of the rubber particles in the ductile matrix is 1% - 6%, such as 1% - 2%, 2% - 3%, 4% - 5%, 5% - 6%. The particulate matter in the above fiber-reinforced composite material meets the above particle size. After being uniformly mixed, the obtained ductile matrix has a certain fluidity and viscosity, can exhibit a gelling property, and after being modified by rubber, has adjustable fracture mechanical properties. Rubber particles that meet the above particle size conditions can effectively promote the cracking of the cement matrix and play a role in evenly arranging micro-defects.

[0037] According to an embodiment of the present application, the fiber-reinforced composite material contains polymer fibers and a cement matrix; the polymer fibers include at least one of polypropylene, polyethylene, polyvinyl alcohol, and polyethylene terephthalate; the maximum volume ratio of the polymer fibers in the ductile matrix is 2 vol%, preferably 1.0 - 2.0 vol%; the cement matrix includes cement and mineral admixtures, the cement includes at least one of ordinary Portland cement, composite Portland cement, sulfoaluminate cement, aluminate cement, alkali-activated cement, and carbonate cement; the mineral admixtures include at least one of fly ash, slag, steel slag, limestone powder, and metakaolin, and the mass ratio of the mineral admixtures to the cement is not less than 1.0, preferably 1 - 4. Polymer fibers and a cement matrix that meet the above conditions can produce an effective crack bridging effect after the rubber promotes cracking, so that the bearing capacity of the ductile matrix does not change in the cracked state, providing conditions for the initiation and development of more cracks.

[0038] According to an embodiment of the present application, the volume ratio of the ductile matrix to the aggregate is at least 3:7, preferably 4:6 to 5:5. When the ratio is lower than this range, the actual ductility of the matrix in the aggregate gaps will be reduced, resulting in a weakened toughening effect; when the ratio is higher than this range, the excessive matrix composition leads to increased costs and enhances the segregation between the ductile matrix and the aggregate, increasing the construction difficulty.

[0039] According to an embodiment of the present application, the aggregate is a continuously graded aggregate and / or a single-graded aggregate. The maximum particle size of the continuously graded aggregate is 4.75 mm to 20 mm, such as one or several of 4.75 - 6 mm, 6 - 8 mm, 8 - 10 mm, 10 - 12 mm, 12 - 14 mm, 14 - 15 mm, 15 - 16 mm, 16 - 18 mm, 18 - 20 mm; the particle size D 50 of the single-graded aggregate is 4.75 mm to 20 mm, such as 4.75 - 6 mm, 6 - 8 mm, 8 - 10 mm, 10 - 12 mm, 12 - 14 mm, 14 - 15 mm, 15 - 16 mm, 16 - 18 mm, 18 - 20 mm. Aggregates that meet the above particle sizes will effectively control the deformation risks such as chemical shrinkage and dry shrinkage of the ductile matrix and control the material cost. When the aggregate particle size is higher than the above range, the risk of segregation and the construction difficulty will increase; when the aggregate particle size is lower than the above range, shrinkage and wear will increase.

[0040] In this article, the term "continuously graded aggregate" refers to an aggregate whose particle size range covers multiple particle sizes from the smallest particle size to the largest particle size, and the "single-graded aggregate" refers to an aggregate with a single particle size grade, and the sizes of all aggregate particles are basically the same.

[0041] According to an embodiment of the present application, the initial cracking strength of the ductile matrix is 1.0 MPa to 5.0 MPa, the ultimate tensile strength is 3.0 MPa to 9.0 MPa, and the ratio of the two is at most 1.0; the remaining energy of the ductile matrix to the crack tip toughness in the cement matrix is at least 1.2, preferably 40 - 60. A ductile matrix that meets the above conditions can effectively develop multiple crack openings at the aggregate gaps under the action of an external tensile stress to adapt to the applied deformation and release internal stress. During the concrete crack propagation process, multiple crack kinks and retentions can be developed on the main crack surface, significantly enhancing the energy absorption capacity during the crack propagation process, thereby achieving the toughness improvement of the concrete material.

[0042] It should be noted that to ensure that the ductile matrix has a certain fluidity and viscosity, chemical admixtures such as water reducers and thickeners as well as nano-particles can be included to improve the rheological properties and ensure the uniform distribution of the aggregate in the matrix.

[0043] Method for preparing concrete

[0044] In another aspect of the present application, a method for preparing the aforementioned concrete is proposed. According to an embodiment of the present application, the method includes: mixing the ductile matrix and the aggregate to obtain the concrete. Thus, the concrete prepared by the method of the present application has high flexural toughness, good tensile strength at the same time, improving the structural safety and durability. In addition, the application of rubber to concrete is also conducive to enhancing the application value of rubber. The method for preparing concrete in the present application is simple to operate, and can be mass-produced relying on existing concrete mixing and production equipment, with high application value.

[0045] According to an embodiment of the present application, the preparation method of the ductile matrix includes: first mixing the cement matrix, rubber and polymer fibers, and then mixing the obtained mixture with water and optional admixtures to obtain the ductile matrix; mixing the ductile matrix with the aggregate to obtain the concrete. This process takes the matrix tensile strain as the design index to guide the selection of rubber content and particle size. In contrast, the preparation process of traditional rubber concrete includes: mixing cement, aggregate and rubber, then mixing the obtained concrete with water, and then obtaining parameters such as rubber content through the mechanical test feedback of the concrete and based on the empirical trial-and-error method. Compared with this, the present application uses the matrix tensile strain as the basis for rubber design, which can improve the utilization efficiency and toughening efficiency of rubber, and increase the flexural toughness of concrete by at least 40% - 230%.

[0046] During the preparation and production process, it can rely on standard mixing station equipment, and one or several of planetary, gravity, and high-speed paddle mixers can be used, without special equipment.

[0047] It should be noted that the characteristics and advantages described above for the concrete also apply to the method for preparing the concrete, and will not be elaborated here.

[0048] The solution of the present application will be explained below in conjunction with embodiments. Those skilled in the art will understand that the following embodiments are only used to illustrate the present application and should not be regarded as limiting the scope of the present application. For those not specified in the embodiments regarding specific technologies or conditions, they shall be carried out according to the technologies or conditions described in the literature in the field or according to the product specifications. For reagents or instruments not specified for the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0049] Example 1

[0050] 1. Mix rubber particles, dry materials, and polymer fibers (polyvinyl alcohol), and add water (the mass ratio of cement to water is 1:0.79) to make a ductile matrix.

[0051] Among them, the dry material components include cement, fly ash, and quartz sand. The cement is ordinary Portland cement with a grade of 42.5, D 50is 12μm, fly ash D 50 is 11μm, quartz sand D 50 is 75μm, and the mass ratio of cement, fly ash, and quartz sand is 1:2.2:1.16. The average particle size D of the rubber particles 50 is 110μm, the mass ratio of rubber particles to cement is 0.09, and the volume fraction of polymer fibers in the ductile matrix is 2%.

[0052] The ultimate tensile strain of the ductile matrix is 5.01%, and the fracture toughness is 0.4 MPa·m 1 / 2 .

[0053] The detection method of the ultimate tensile strain is as follows:

[0054] Prepare the ductile matrix sample into a dumbbell shape, conduct a direct tensile test on a tensile testing machine at a loading rate of 0.5 mm / min, use two displacement gauges to measure the deformation of the middle section simultaneously, and record the stress data simultaneously. The test standards and specific dimensions of the samples can refer to the recommended specifications of the Japan Society of Civil Engineers, JSCERecommendations for Design andConstruction of High Performance Fiber Reinforced Cement Composites withMultiple Fine Cracks.2008:Tokyo. The fracture toughness is detected with reference to the ASTM E399 standard.

[0055] 2. Mix the ductile matrix and aggregates (crushed stones, single-sized grading) in a volume ratio of 4:6 to make concrete. Among them, the aggregates are of single-sized grading, the maximum particle size is 20 mm, and the minimum particle size is 4.75 mm.

[0056] Example 2

[0057] Prepare the concrete according to the method of Example 1, except that in step 1, adjust the mass ratio of rubber particles to cement to 0.23. The ultimate tensile strain of the prepared ductile matrix is 5.66%, and the fracture toughness is 0.3 MPa·m 1 / 2 .

[0058] Comparative Example 1

[0059] Prepare the concrete according to the method of Example 1, except that the steps are as follows: Mix cement, fly ash, quartz sand, and aggregates, add water to obtain traditional concrete, and then add fibers to the traditional concrete to obtain traditional fiber concrete.

[0060] Comparative Example 2

[0061] Prepare concrete according to the method of Example 1, except that Step 1 is as follows: Mix cement, fly ash, quartz sand, and rubber particles, and after adding water, obtain a ductile matrix. Among them, the mass ratio of cement, fly ash, quartz sand, and rubber particles is 1:2.2:1.16:0.09.

[0062] The ultimate tensile strain of the above ductile matrix is about 0.009%, and the fracture toughness is 0.5 MPa·m 1 / 2 .

[0063] Comparative Example 3

[0064] Prepare concrete according to the method of Example 1, except that the steps are as follows:

[0065] Mix rubber particles, dry materials, aggregates, and polymer fibers evenly, and further mix with water to obtain rubber concrete. The ultimate tensile strain of the above matrix is about 0.010%, and the fracture toughness is 0.5 MPa·m 1 / 2 .

[0066] Comparative Example 4

[0067] Prepare concrete according to the method of Example 1, except that it does not contain rubber and polymer fibers. After mixing the aggregates and dry materials evenly, mix with water to obtain ordinary concrete. The ultimate tensile strain of the above mortar is about 0.010%, and the fracture toughness is 0.5 MPa·m 1 / 2 .

[0068] Test Example

[0069] Detect the flexural toughness and strength of the concrete prepared in Examples 1-2 and Comparative Examples 1-4 respectively. The specific detection steps are as follows: Use an MTS testing machine to conduct tests under the condition of a four-point bending method and a loading rate of 0.1 mm / min. Use a displacement meter to measure the mid-span deflection on both sides of the sample in real time and obtain the load-deflection curve. Calculate the flexural toughness and flexural strength using the ASTM C1609 method.

[0070] The results are shown in the following table.

[0071] Table 1: Test Results

[0072]

[0073] It can be seen that in Examples 1 and 2, the ductile matrix concrete obtained by rubber modification has higher flexural toughness and strength than the rubber concretes with the same composition in Comparative Examples 2 and 3 but designed by traditional methods. Among them, the flexural toughness improvement rate is 41.9% - 153.4%, and the flexural strength improvement rate is 18.0% - 24.0%. The enhancement and toughening effects come from the multi-crack cracking of the matrix promoted by rubber and the improvement of ductility. The phenomenon of multiple kinking and retention of the main cracks caused by the multi-crack cracking of the ductile matrix can be seen in Appendix Figure 1 . At the same time, compared with the traditional fiber concrete in Comparative Example 1 ( Figure 2 ), the flexural toughness and strength of the ductile matrix concrete after rubber modification are increased by 22.6% - 117.4% and 1.3% - 13.3% respectively, indicating that the collaborative design of rubber and ductile matrix can effectively improve the flexural toughness of concrete without significantly losing the flexural strength. In contrast, for the traditional ordinary concrete in Comparative Example 4, both the flexural toughness and strength are significantly reduced. Even if the dosage of rubber particles is adjusted, there is no significant change in the flexural toughness and strength. The above results show that the combination of rubber and ductile matrix is beneficial to improving the utilization efficiency of rubber in concrete, thereby promoting a significant improvement in the toughness of concrete.

[0074] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present application. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present application.

Claims

1. A kind of concrete, characterized in that, Comprising: A ductile matrix and aggregates, wherein the ductile matrix is selected from rubber-modified fiber-reinforced composites.

2. The concrete according to claim 1, characterized in that, The ultimate tensile strain of the ductile matrix is 3% - 15%, preferably 3% - 7%; The fracture toughness of the ductile matrix does not exceed 0.6 MPa·m 1 / 2 .

3. The concrete according to claim 1 or 2, characterized in that, The ductile matrix comprises rubber particles and a fiber cement composite; The average particle size D of the rubber particles 50 is not greater than 1 mm, preferably 30 μm to 500 μm; The mass proportion of the rubber particles in the ductile matrix is 1% - 6%.

4. The concrete according to claim 1 or 2, characterized in that, The fiber-reinforced composite contains polymer fibers and a cement matrix; The polymer fibers include at least one of polypropylene, polyethylene, polyvinyl alcohol, and polyethylene terephthalate; The maximum volume proportion of the polymer fibers in the ductile matrix is 2 vol%, preferably 1.0 - 2.0 vol%; The cement matrix comprises cement and mineral admixtures, the cement includes at least one of ordinary Portland cement, composite Portland cement, sulfoaluminate cement, aluminate cement, alkali-activated cement, and carbonate cement; the mineral admixtures include at least one of fly ash, slag, steel slag, limestone powder, and metakaolin; the mass ratio of the mineral admixtures to the cement is not less than 1.0, preferably 1 - 4.

5. The concrete according to claim 1, characterized in that, The volume ratio of the ductile matrix to the aggregates is at least 3:7, preferably 4:6 - 5:

5.

6. The concrete according to claim 1 or 5, characterized in that, The aggregate is continuously graded aggregate and / or single-graded aggregate. The maximum particle size of the continuously graded aggregate is 4.75 mm to 20 mm, and the particle size D 50 of the single-graded aggregate is 4.75 mm to 20 mm.

7. The concrete according to claim 4, wherein The initial cracking strength of the ductile matrix is 1.0 MPa - 5.0 MPa, the ultimate tensile strength is 3.0 MPa - 9.0 MPa, and the ratio of the two is at most 1.0; The ratio of the remaining energy of the ductile matrix to the crack tip toughness in the cement matrix is at least 1.2, preferably 40 - 60.

8. A method for preparing the concrete according to any one of claims 1 to 7, characterized in that, Comprising: Mixing the ductile matrix and the aggregates to obtain the concrete.

9. The method according to claim 8, wherein Comprising: First, mix the cement matrix, rubber, and polymer fibers, and then mix the resulting mixture with water and optional admixtures to obtain the ductile matrix; Mix the ductile matrix with the aggregates to obtain the concrete.

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