A high-mechanical-performance magnetized rubber concrete and its preparation method

Abstract

This invention discloses a high-mechanical-performance magnetized rubber concrete and its preparation method. The concrete is produced by introducing magnetized rubber particles into the aggregate and curing it using an electric field. Magnetization enhances the interfacial bonding between the rubber particles and the cement matrix, while the electric field guides a more uniform particle distribution and tighter interlocking. This method not only significantly improves the tensile and flexural strength of the concrete, but also enhances its toughness and crack resistance, and achieves the resource utilization of waste rubber. The preparation process of this invention is simple and controllable, and the resulting concrete exhibits excellent comprehensive mechanical properties, showing promising application prospects.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, specifically to a high-mechanical-performance magnetized rubber concrete and its preparation method. Background Technology

[0002] Concrete, as the most important civil engineering material, is widely used in infrastructure construction worldwide. Its core advantages lie in its high compressive strength and good durability. However, the inherent mechanical defects of traditional concrete, such as high brittleness, low tensile strength, and poor toughness, limit its application in structures subjected to dynamic loads, impacts, or bending stresses. These defects can easily lead to brittle failure of structures under stress, affecting safety and service life.

[0003] In the field of building material modification, research on using rubber particles as concrete admixtures has been extensive. The introduction of rubber particles aims to improve the brittleness of concrete and enhance its toughness and impact resistance. However, ordinary rubber particles have smooth and inert surfaces, resulting in weak adhesion to the cement matrix, and the interfacial area easily becomes a stress-weak zone. Numerous studies have shown that while the incorporation of rubber particles improves the toughness of concrete, it usually leads to a significant decrease in key mechanical properties such as compressive strength and flexural strength. This "strength-toughness" contradiction caused by insufficient interfacial bonding is a major technical bottleneck restricting the widespread application of rubber concrete in practical engineering.

[0004] Therefore, how to effectively modify the surface of rubber particles through physical or chemical methods to strengthen their interfacial bonding with cement hydration products, thereby improving the toughness of concrete while maintaining or enhancing its mechanical strength, has become an important research direction in this field. Existing surface treatment technologies (such as alkali treatment and coupling agent coatings) have some effect, but they are often complex processes or have limited improvement effects, failing to fundamentally solve the problem of weak interfaces. Developing an efficient, stable method for modifying rubber particles and strengthening the interface that can be well integrated with concrete preparation processes is of great significance for promoting the development of high-performance rubber concrete. Summary of the Invention

[0005] The present invention aims to overcome the defects of significant loss of mechanical properties in existing rubber concrete technology, and to provide a high-performance magnetized rubber concrete and its preparation method that can not only effectively utilize waste rubber resources, but also maintain or even improve the mechanical properties of concrete.

[0006] To solve the above-mentioned technical problems, the technical solution proposed in this application is as follows:

[0007] This invention provides a high-mechanical-performance magnetized rubber concrete, comprising the following raw materials: cement 350-380 kg / m³ 3 Coarse aggregate 1000-1100 kg / m³3 Fine aggregate 680-860 kg / m³ 3 Improved magnetized rubber granules 15-80 kg / m 3 Water 100-110 kg / m³ 3 and water-reducing agent 4-6 kg / m 3 .

[0008] Furthermore, the volume ratio of the improved magnetized rubber particles to the fine aggregate is less than 0.2.

[0009] Furthermore, the improved magnetized rubber particles have a particle size of less than 1 mm, and their preparation method includes: first, pre-treating the rubber particles by washing and drying with alkaline solution, then immersing the pre-treated rubber particles in a modified solvent containing silane coupling agent and Fe3O4 nanoparticles to attach magnetism to their surface, and finally obtaining them by vacuum drying.

[0010] Furthermore, the cleaning solvent used for alkaline cleaning is a solution containing 1-3% NaOH; the concentration of silane coupling agent in the modified solvent is 1-1.2%, the mass of Fe3O4 nanoparticles is 20-30% of the mass of rubber particles, and the particle size of Fe3O4 nanoparticles is 15-50 nm; the vacuum drying conditions are baking at 80±5℃ for 2 hours.

[0011] Furthermore, the fine aggregate is river sand with a fineness modulus of 2.8; the coarse aggregate is continuously graded crushed stone with a particle size of 5-30 mm; the water-reducing agent is a polycarboxylate high-efficiency water-reducing agent with a water reduction rate of 25%, and its dosage is 1%-2% of the cement mass; the cement is P·O 42.5 silicate cement.

[0012] On the other hand, this application also claims protection for a method for preparing magnetized rubber concrete with high mechanical properties, comprising the following steps:

[0013] (1) Mix the coarse aggregate and fine aggregate together for 1-2 minutes;

[0014] (2) Add cement and stir for 1-2 minutes;

[0015] (3) Add the modified magnetized rubber particles and stir for 1-2 minutes;

[0016] (4) Add about two-thirds water and stir for 1-2 minutes;

[0017] (5) Add about half of the water-reducing agent and stir for 1-2 minutes;

[0018] (6) Add the remaining water and water-reducing agent, stir for 1-2 minutes to obtain concrete mixture;

[0019] (7) Pour the concrete mixture into the mold, vibrate for 40-50 seconds, and then insert a metal guide rod into the mixture;

[0020] (8) Apply a voltage of 5-12V to the metal conductor rod and energize it for 2-3 hours;

[0021] (9) The concrete after being electro-treated is naturally dried and cured according to standard to obtain magnetized rubber concrete with high mechanical properties.

[0022] Furthermore, in step (8), the power supply is a 5-12V DC power supply, and the power-on time is 2-3 hours.

[0023] Furthermore, in step (9), the standard curing conditions are: temperature 20±2℃, relative humidity greater than 95%, and curing time 28-32 days.

[0024] Furthermore, the coarse aggregate is rinsed with water and air-dried naturally until the surface is dry before use.

[0025] Furthermore, the raw material for preparing the improved magnetized rubber particles is obtained by crushing waste tire rubber.

[0026] Compared with the prior art, the present invention achieves the following beneficial technical effects:

[0027] This invention effectively improves the interfacial bonding between rubber and cement matrix by magnetizing and modifying rubber particles and combining them with electric field guidance technology. This allows concrete to maintain significantly improved tensile and flexural strength while retaining good toughness even after rubber incorporation. This technology not only enhances the overall mechanical properties and crack resistance of concrete but also achieves efficient resource utilization of waste rubber. Furthermore, the process is highly controllable and has the potential to form directional reinforcement structures. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 The graph shows a comparison of the cubic compressive strength test results of the high mechanical properties magnetized rubber concrete prepared in Examples 1-5.

[0030] Figure 2 Comparison of splitting tensile strength test results for the high mechanical properties magnetized rubber concrete prepared in Examples 1-5.

[0031] Figure 3The graph shows a comparison of the flexural strength test results of the high mechanical properties magnetized rubber concrete prepared in Examples 1-5.

[0032] Figure 4 The image shows actual photos of the rubber granules used in the preparation process, with a particle size of approximately 20 mesh (0.85 mm).

[0033] Figure 5 This is a scanning electron microscope (SEM) image of the microstructure of high-mechanical-performance magnetized rubber concrete (RC5) after hardening. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] The main raw materials used in this invention include:

[0036] Cement: P·O42.5 grade ordinary Portland cement.

[0037] Coarse aggregate: Continuously graded crushed stone with a particle size of 5-30mm and an apparent density of approximately 2650kg / m³. 3 Rinse with water before use and air dry until the surface is dry.

[0038] Fine aggregate: River sand, fineness modulus of 2.8, apparent density of approximately 2650 kg / m³ 3 .

[0039] Rubber granules: obtained by mechanically crushing and screening waste tires, with a particle size of less than 1mm (e.g., 20 mesh, approximately 0.85mm) and a density of approximately 1200kg / m³. 3 .

[0040] Water-reducing agent: Polycarboxylate-based high-efficiency water-reducing agent with a water reduction rate of approximately 25%.

[0041] Modified magnetization treatment reagents: sodium hydroxide (NaOH), anhydrous ethanol, silane coupling agent (such as KH-550), and nano-iron oxide (Fe3O4) particles (particle size 15-50nm).

[0042] Water: Ordinary tap water.

[0043] The main equipment includes: forced concrete mixer, electronic balance, vibrating table, mold, vacuum drying oven, centrifuge, DC regulated power supply, metal guide rods (such as copper rods or steel rods), etc.

[0044] 1. Preparation of improved magnetized rubber particles

[0045] The preparation of modified magnetized rubber particles is a key pretreatment step for achieving the technical effect of this invention, and the specific implementation is as follows:

[0046] First, weigh a certain amount of raw rubber granules obtained from shredded waste tires and place them in a container filled with a weakly alkaline cleaning solvent. The cleaning solvent is a 1-3% (w / w) NaOH aqueous solution. Stir and wash at room temperature for 10-15 minutes, removing oil, dust, and other impurities from the surface of the rubber granules through mechanical friction and saponification by the alkaline solution. After washing, remove the rubber granules and transfer them to clean water for multiple rinses until the wash water is neutral. Then, dehydrate the washed rubber granules using a centrifuge, and then spread them out to air dry naturally in a ventilated area, or dry them in a low-temperature (e.g., 50°C) oven until there is no obvious moisture on the surface of the granules, obtaining pre-treated clean and dry rubber granules.

[0047] Next, magnetization modification is performed. The modification solvent is prepared by adding the silane coupling agent to anhydrous ethanol and stirring until fully dissolved, controlling the final concentration of the silane coupling agent in the ethanol solution to be 1-1.2% (mass fraction). Then, nano-Fe3O4 particles are added to this solution, with the amount of Fe3O4 added being approximately 20-30% of the mass of the rubber particles to be treated. The nano-Fe3O4 particles are uniformly dispersed in the solution using ultrasonic dispersion or high-speed stirring. The pretreated dried rubber particles are then immersed in the prepared modification solvent, ensuring the solution completely covers the particles. The immersion time can be adjusted according to the particle quantity, typically 30-60 minutes, with appropriate stirring during this period to ensure the modification solvent fully wets the surface of the rubber particles. The silane coupling agent acts as a "bridge," binding one end to the rubber surface and fixing the Fe3O4 nanoparticles at the other end through physical adsorption or encapsulation, thereby giving the rubber particle surface magnetism. After immersion, the rubber particles are removed, and excess solution is drained.

[0048] Finally, drying and curing are performed. The wet, magnetized rubber particles with the modified solvent adhering to their surface are evenly spread on a tray in a vacuum drying oven. The drying temperature is set to 80±5℃, and the particles are baked under vacuum for 2 hours. This process helps the solvent to evaporate completely and allows the silane coupling agent to complete its hydrolysis and condensation reaction, forming a stable modified layer on the surface of the rubber particles and firmly fixing the Fe3O4 nanoparticles. After baking, the heating is turned off, and the temperature inside the drying oven is allowed to cool naturally to room temperature. The particles are then removed, yielding the "modified magnetized rubber particles" described in this invention. These particles have an active surface and are magnetic.

[0049] 2. Preparation of high-mechanical-performance magnetized rubber concrete

[0050] The concrete preparation method of the present invention is described in detail below through specific embodiments. In all embodiments and comparative examples, the amount of cement per cubic meter of concrete is fixed at 360 kg, the amount of water is fixed at 108.88 kg (water-cement ratio approximately 0.30), the amount of water-reducing agent (polycarboxylate superplasticizer) is fixed at 4.14 kg (approximately 1.15% of the cement mass), and the amount of coarse aggregate (crushed stone) is fixed at 1034.63 kg. The parameters that vary are the amounts of fine aggregate (river sand) and modified magnetized rubber particles, wherein the volume ratio of modified magnetized rubber particles to fine aggregate is less than 0.2. The density of river sand is 2650 kg / m³. 3 The density of rubber granules is 1200 kg / m³. 3 Perform mass conversion. The prepared concrete, such as... Figure 4 As shown, Figure 5 This is its electron microscope image.

[0051] Example 1: Ordinary reference concrete (NC)

[0052] This example is a comparison sample of ordinary concrete without the addition of rubber particles.

[0053] Raw material usage: Cement 360kg / m³ 3 River sand 855kg / m 3 Crushed stone 1034.63 kg / m³ 3 Water 108.88 kg / m³ 3 Water-reducing agent 4.14 kg / m³ 3 Rubber granules 0kg / m 3 .

[0054] Preparation method:

[0055] Pour the weighed gravel and river sand into a forced mixer and dry mix for about 1.5 minutes to ensure the aggregates are evenly mixed.

[0056] Add cement and continue dry mixing for about 1.5 minutes.

[0057] Pour approximately 72 kg (two-thirds of the total water volume) evenly into the mixer and mix for about 1.5 minutes.

[0058] Sprinkle approximately 2.07 kg (half of the total water-reducing agent) of the water-reducing agent evenly into the mixture and stir for about 1.5 minutes.

[0059] Add the remaining 36.88 kg of water and 2.07 kg of water-reducing agent together, and continue stirring for about 2 minutes until the mixture is uniform and of moderate viscosity, thus obtaining the reference concrete mixture.

[0060] The mixture was placed in two layers into a cubic mold with dimensions of 150mm×150mm×150mm and corresponding flexural and splitting test molds. Each layer was vibrated for about 45 seconds with a vibrator until the surface was covered with slurry and no obvious air bubbles escaped. Over-vibration should be avoided.

[0061] Smooth the surface of the specimen and let it stand at room temperature for 24 hours before demolding.

[0062] Immediately after demolding, the specimens were placed in a standard curing room (temperature 20±2℃, relative humidity >95%) and cured for 28 days to obtain ordinary reference concrete specimens.

[0063] Example 2: Magnetized Rubber Concrete (RC5)

[0064] Raw material usage: Cement 360kg / m³ 3 River sand 812.25 kg / m³ 3 Crushed stone 1034.63 kg / m³ 3 Water 108.88 kg / m³ 3 Water-reducing agent 4.14 kg / m³ 3 Improved magnetized rubber granules 19.36 kg / m 3 .

[0065] Preparation method:

[0066] Pour the weighed gravel and river sand into a forced mixer and dry mix for about 1.5 minutes.

[0067] Add cement and continue dry mixing for about 1.5 minutes.

[0068] Add all the modified magnetized rubber granules and dry mix for about 2 minutes to initially mix the rubber granules and dry materials evenly and avoid clumping.

[0069] Pour in approximately 72 kg of water evenly and stir for about 1.5 minutes.

[0070] Sprinkle approximately 2.07 kg of water-reducing agent evenly into the mixture and stir for about 1.5 minutes.

[0071] Add the remaining 36.88 kg of water and 2.07 kg of water-reducing agent, stir for about 2 minutes to obtain a uniform magnetized rubber concrete mixture.

[0072] Pour the mixture into the mold and vibrate for about 45 seconds. After vibration, immediately insert a copper rod with a diameter of about 5 mm vertically into the center of each side of the mold as a guide rod. The guide rod should be inserted to a depth of about three-quarters of the height of the specimen, with the exposed part used to connect to the power supply.

[0073] Two metal conductor rods were connected to the positive and negative electrodes of a DC regulated power supply, and the output voltage was adjusted to 8V. The concrete specimen was then subjected to energization for 2.5 hours. During this period, the concrete was in the early stage of transitioning from plasticity to hardening. The magnetic rubber particles inside the concrete underwent slight directional movement and redistribution under the influence of the magnetic field or electric force generated by the electric field, making them more tightly integrated with the surrounding cement paste.

[0074] After powering on, disconnect the power supply and carefully remove the metal guide rod (the small hole left behind has negligible impact on macroscopic performance testing). Allow the specimen and mold to air dry naturally at room temperature for 24 hours.

[0075] After demolding, the specimens were moved into a standard curing room and cured for 28 days to obtain RC5 concrete specimens.

[0076] Example 3: Magnetized rubber concrete (RC10)

[0077] Raw material usage: Cement 360kg / m³ 3 River sand 769.5 kg / m 3 Crushed stone 1034.63 kg / m³ 3 Water 108.88 kg / m³ 3 Water-reducing agent 4.14 kg / m³ 3 Improved magnetized rubber granules 38.72 kg / m 3 .

[0078] The preparation method is the same as in Example 2, except that the raw material ratio is different and the electrostatic treatment conditions are the same.

[0079] Example 4: Magnetized rubber concrete (RC15)

[0080] Raw material usage: Cement 360kg / m³ 3 River sand 726.75 kg / m³ 3 Crushed stone 1034.63 kg / m³ 3 Water 108.88 kg / m³ 3 Water-reducing agent 4.14 kg / m³ 3 Improved magnetized rubber granules 58.08 kg / m 3 .

[0081] The preparation method is the same as in Example 2, except that the raw material ratio is different and the electrostatic treatment conditions are the same.

[0082] Example 5: Magnetized rubber concrete (RC20)

[0083] Raw material usage: Cement 360kg / m³ 3 River sand 684 kg / m 3 Crushed stone 1034.63 kg / m³ 3Water 108.88 kg / m³ 3 Water-reducing agent 4.14 kg / m³ 3 Improved magnetized rubber granules 77.43 kg / m 3 .

[0084] The preparation method is the same as in Example 2, except that the raw material ratio is different and the electrostatic treatment conditions are the same.

[0085] Performance Testing and Analysis

[0086] Concrete specimens from Examples 1-5, cured for 28 days, were tested for cubic compressive strength, splitting tensile strength, and flexural strength according to the "Standard for Test Methods of Mechanical Properties of Ordinary Concrete". The test results are summarized in the table below:

[0087]

[0088] Combination Figure 1-3 From the intensity change curve, the following conclusions can be drawn:

[0089] Cube compressive strength: The compressive strength of RC5 concrete reached 41.10 MPa, which is about 15.4% higher than that of the benchmark NC concrete (35.62 MPa). This indicates that the appropriate amount (5% volume replacement rate in this experiment) of incorporating fine rubber particles that have undergone magnetization modification and electric field treatment not only did not reduce the concrete strength, but also played a reinforcing role. The reinforcing mechanism may include: 1. Fine magnetized rubber particles smaller than 1 mm effectively fill some of the micropores and initial defects in the interface transition zone between cement paste and aggregate, improving the density of concrete; 2. Under the action of an electric field, the magnetic rubber particles are more evenly distributed, and the physical interlocking and chemical bonding with the cement matrix are strengthened, making the load transfer within the matrix more uniform and reducing local stress concentration. When the rubber content increased to 10% (RC10), 15% (RC15), and 20% (RC20), the compressive strength decreased to 32.07 MPa, 23.49 MPa, and 14.76 MPa, respectively, representing reductions of 9.96%, 34.05%, and 58.56% compared to the baseline NC. The reason for the strength decrease is that, despite modification, the elastic modulus and compressive strength of the rubber particles themselves are still far lower than those of the replaced river sand. Excessive rubber particles introduce more weak points into the concrete. Under load, cracks readily initiate and rapidly propagate at the interface between these rubber particles and the matrix, leading to accelerated overall concrete failure. Figure 5 The SEM images (RC5 sample) also show that even in the best-performing RC5, there are still a few microcracks at the interface between the rubber particles and the cement stone matrix, and the density of the interface area needs to be further improved.

[0090] Splitting tensile strength and flexural strength: The splitting tensile strength of RC5 concrete is 3.85 MPa, a significant increase of 30.07% compared to NC (2.96 MPa); its flexural strength is 3.56 MPa, an increase of 23.75% compared to NC (2.88 MPa). This is mainly attributed to the high elasticity of the rubber particles. When subjected to tensile or flexural stress, the rubber particles, uniformly distributed in the matrix, can absorb and disperse some energy through their own elastic deformation, delaying the propagation of microcracks, thereby improving the toughness and crack resistance of the concrete. As the rubber content continues to increase (RC10-RC20), excessive rubber-matrix weak interfaces become the dominant factor, leading to a decrease in tensile and flexural properties, but the decrease is less than that of compressive strength. For example, the flexural strength of RC20 (2.57 MPa) is still close to the level of NC, demonstrating a certain ability to retain toughness.

[0091] In summary, this invention, through an innovative dual technology of "magnetization modification + electric field guidance," effectively improves the interfacial properties between rubber particles and the cement matrix. This allows the magnetized rubber concrete prepared at low dosages (e.g., 5% volume replacement rate) to achieve a comprehensive improvement in mechanical properties (especially tensile and flexural strength), while also offering good environmental benefits. The optimal dosage can be selected and optimized within the range of 0-20% based on the different strength and toughness requirements of the project.

[0092] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high-mechanical-performance magnetized rubber concrete, characterized in that, The following raw materials are included in the preparation: cement 350-380 kg / m³ 3 Coarse aggregate 1000-1100 kg / m³ 3 Fine aggregate 680-860 kg / m³ 3 Improved magnetized rubber granules 15-80 kg / m 3 Water 100-110 kg / m³ 3 and water-reducing agent 4-6 kg / m 3 The modified magnetized rubber particles have a particle size of less than 1 mm, and their preparation method includes: first, pre-treating the rubber particles by washing and drying with alkaline solution; then, immersing the pre-treated rubber particles in a modified solvent containing silane coupling agent and Fe3O4 nanoparticles to make their surface magnetic; then, inserting a metal conductor rod into the mixture, applying a 5-12V DC current for 2-3 hours, and finally obtaining the product by vacuum drying.

2. The high-mechanical-performance magnetized rubber concrete according to claim 1, characterized in that, The volume ratio of the modified magnetized rubber particles to the fine aggregate is less than 0.

2.

3. The high-mechanical-performance magnetized rubber concrete according to claim 2, characterized in that, The cleaning solvent used for alkaline cleaning is a solution containing 1-3% NaOH; the concentration of silane coupling agent in the modified solvent is 1-1.2%; the mass of the Fe3O4 nanoparticles is 20-30% of the mass of the rubber particles; and the particle size of the Fe3O4 nanoparticles is 15-50 nm; the vacuum drying conditions are baking at 80±5℃ for 2 hours.

4. The high-mechanical-performance magnetized rubber concrete according to claim 1, characterized in that, The fine aggregate is river sand with a fineness modulus of 2.8; the coarse aggregate is continuously graded crushed stone with a particle size of 5-30 mm; the water-reducing agent is a polycarboxylate high-efficiency water-reducing agent with a water reduction rate of 25%, and its dosage is 1%-2% of the cement mass; the cement is P·O 42.5 silicate cement.

5. A method for preparing high-mechanical-performance magnetized rubber concrete as described in any one of claims 1-4, characterized in that, Includes the following steps: (1) Mix the coarse aggregate and fine aggregate together for 1-2 minutes; (2) Add cement and stir for 1-2 minutes; (3) Add the modified magnetized rubber particles and stir for 1-2 minutes; (4) Add about two-thirds water and stir for 1-2 minutes; (5) Add about half of the water-reducing agent and stir for 1-2 minutes; (6) Add the remaining water and water-reducing agent, stir for 1-2 minutes to obtain concrete mixture; (7) The concrete mixture is poured into the mold and vibrated for 40-50 seconds, and then a metal guide rod is inserted into the mixture; (8) Apply a voltage of 5-12V to the metal conductor rod and energize it for 2-3 hours; (9) The concrete after being electro-treated is naturally dried and cured according to standard conditions to obtain the high mechanical properties magnetized rubber concrete.

6. The preparation method according to claim 5, characterized in that, In step (9), the standard curing conditions are: temperature 20±2℃, relative humidity greater than 95%, and curing time 28-32 days.

7. The preparation method according to claim 5, characterized in that, The coarse aggregate is rinsed with water and air-dried naturally until the surface is dry before use.

8. The preparation method according to claim 5, characterized in that, The raw material for preparing the improved magnetized rubber particles is obtained by crushing waste tire rubber.

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