Green high-performance cement-based composite material and preparation thereof

Abstract

The invention belongs to the field of building materials or foundation engineering construction, and particularly relates to a green high-performance cement-based composite material and a preparation method thereof.The green high-performance cement-based composite material with high tensile strength is researched and developed by completely replacing silica sand in an engineering cement-based composite material (ECC) with waste asphalt powder and fine sand, and the green high-performance cement-based composite material with high tensile strength is obtained. The composite material is prepared from the following raw materials: water, coal ash, cement, polyvinyl alcohol fibers, fine sand, waste asphalt mixture (RAP) powder and a water reducing agent. The preparation method comprises the following steps: grinding a waste asphalt mixture into a powder material for later use; soaking polyvinyl alcohol fibers in water for later use; mixing and stirring the cement, the fly ash, the fine sand and the waste asphalt mixture powder; and adding a water reducing agent and part of water into the stirred mixture, stirring, then adding the polyvinyl alcohol fiber and water for later use, and stirring again to obtain the cement-based composite material. A new direction is opened up for efficient utilization of the waste asphalt mixture, and the prepared green high-performance cement-based composite material is suitable for various material fields of civil engineering.

Description

Technical Field

[0001] This invention belongs to the field of building materials or basic engineering construction, and specifically relates to a green high-performance cement-based composite material and its preparation. Background Technology

[0002] In the early 1990s, the University of Michigan successfully developed a high-performance engineered cementitious composite (ECC) with medium fiber volume fraction and random short fiber reinforcement. It uses polyethylene or polyvinyl alcohol fibers as reinforcement and cement paste or special cement mortar as the matrix. Reasonable fiber, matrix, and interface performance parameters were selected using micromechanical, fracture mechanics, and mathematical statistical methods. This new material exhibits pseudo-strain hardening and multi-crack characteristics under tensile and bending loads. The maximum crack width can be controlled within 0-1 mm, effectively preventing the intrusion of harmful external substances and improving the durability of hydraulic structures. However, the silica sand used in this material is expensive and its transportation costs are high, hindering its widespread application.

[0003] Reclaimed asphalt pavement (RAP) is aggregate and granular material separated from the demolition waste of old asphalt pavements. It possesses certain road performance properties. The recycling of asphalt pavements can save significant amounts of asphalt, sand, and other raw materials, reducing project investment while also facilitating waste disposal and environmental protection, thus yielding significant economic, social, and environmental benefits. However, the utilization rate of recycled asphalt in China is currently very low. my country's annual RAP production exceeds 800 million tons, with major and medium-scale highway repair projects alone generating 160 million tons of old asphalt pavement material annually. Only 10% to 20% of recycled asphalt is used in asphalt concrete pavements through mix design, a recycling rate far below the over 90% level in developed countries. The majority of the remaining recycled asphalt is used in the surface layer of low-traffic highways and the subbase or base course of high-grade highways, with some even being stockpiled as waste. Adding reclaimed asphalt pavement to ECC can reduce carbon emissions while simultaneously lowering the elastic modulus of the ECC.

[0004] This research demonstrates the importance of designing and preparing green, high-performance cement-based composite materials through material mix proportions without altering the performance of ECC. This approach achieves high ductility and crack control capabilities in ECC, effectively utilizes solid waste resources, and reduces carbon emissions. This research has significant practical implications and substantial economic value. Summary of the Invention

[0005] Technical Problem: The purpose of this invention is to address the shortcomings and defects in the existing technology, and to provide a green, environmentally friendly, and highly ductile cement-based composite material by using recycled asphalt and fine sand as reinforcing substitutes to replace silica sand. This invention also opens up new avenues for the rational utilization of recycled asphalt and improves its recycling rate.

[0006] Technical solution: In the first aspect, the present invention provides a green high-performance cement-based composite material formulation, comprising the following raw materials in parts by weight: 274 parts water, 559 parts fly ash, 559 parts cement, 201 parts fine sand, 201 parts waste asphalt mixture powder and 10.8 parts water-reducing agent, wherein 2% by volume of polyvinyl alcohol fiber is added to each cubic meter of the cement-based composite material.

[0007] Preferably, the green high-performance cement-based composite material, the waste asphalt mixture powder preparation method is as follows: [8] the recycled block waste asphalt mixture is manually crushed to obtain RAP coarse aggregate.

[0008] RAP coarse aggregate is placed in an ore crushing ball mill for fine crushing to obtain RAP fine aggregate.

[0009] RAP fine aggregate is screened to obtain waste asphalt mixture powder.

[0010] The asphalt content in the block-shaped waste asphalt mixture is 5% to 7%.

[0011] The RAP coarse aggregate has a particle size of 5-8 mm.

[0012] Preferably, in the green high-performance cement-based composite material, the waste asphalt mixture powder has a mesh size of 30 to 300 mesh.

[0013] Preferably, the green high-performance cement-based composite material uses ordinary tap water, which meets the requirements of the "Standard for Water Used in Concrete" JGJ63.

[0014] Preferably, the green high-performance cement-based composite material uses P.0.42.5 cement as the cement.

[0015] Preferably, in the green high-performance cement-based composite material, the fly ash is secondary fly ash with a water requirement ratio ≤98%, loss on ignition ≤5%, and fineness (45μm square mesh sieve) ≤20%.

[0016] Preferably, in the green high-performance cement-based composite material, the fine sand is continuously graded and has a fineness modulus of 1.6-2.2.

[0017] Preferably, in the green high-performance cement-based composite material, the water-reducing agent is a polycarboxylate-type water-reducing agent with a water reduction rate of ≥30%.

[0018] Preferably, in the green high-performance cement-based composite material, the polyvinyl alcohol fiber has a tensile strength of 1620 MPa, an elastic modulus of 42.8 GPa, a diameter of 39 μm, a length of 8 mm, and a volume usage of 2%.

[0019] Secondly, the present invention also provides a method for preparing the aforementioned green high-performance cement-based composite material, characterized by comprising the following steps:

[0020] S1. After ball milling the waste asphalt mixture for 5-10 minutes, obtain the powder material for later use;

[0021] S2. First, use a damp cloth to fully moisten the mixing blades and mold of the mixer. Weigh out 559 parts of cement, 559 parts of fly ash, 201 parts of fine sand, 201 parts of RAP powder, 10.8 parts of water-reducing agent, 26 parts of polyvinyl alcohol fiber, and 274 parts of water according to the mass ratio. Soak the polyvinyl alcohol fiber in water for later use.

[0022] S3. Pour cement, fly ash, fine sand, water-reducing agent and RAP powder into a planetary mixer and mix at 100 rpm for 2 minutes. Slowly add water from the fiber and increase the mixer speed to 166 rpm. Mix for 3 minutes until the cement-based slurry is uniform. Then disperse the prepared polyvinyl alcohol fiber and mix at the same speed for 4-5 minutes to prepare a green high-performance cement-based composite material.

[0023] S4. The mixed slurry is cured to obtain a green, high-performance cement-based composite material. In this invention, the preferred curing conditions include: room temperature, a temperature of 17–23°C, and a curing time of 1–3 days.

[0024] The beneficial effects of this invention are as follows: the preparation method of this invention is simple, which can effectively reduce the production cost of ECC, further reduce carbon emissions caused by cement production, improve environmental benefits, make full use of the characteristics of RAP to turn waste into treasure, explore a new way of "treating waste with waste and turning waste into treasure", and play a positive role in promoting the comprehensive utilization of waste asphalt mixture. Attached Figure Description

[0025] Figure 1 A physical image of RAP.

[0026] Figure 2 fine-grained RAP image

[0027] Figure 3 Image of a green high-performance cement-based composite slurry

[0028] Figure 4 Comparison of tensile strength of green ECC with different RAP replacement rates

[0029] Figure 5 Comparison chart of green ECC compressive strength with different RAP replacement rates Detailed Implementation

[0030] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0031] Example 1

[0032] A method for preparing a green, high-performance cement-based composite material includes the following steps:

[0033] S1. After ball milling the waste asphalt mixture for 5-10 minutes, obtain the powder material for later use;

[0034] S2. First, use a damp cloth to fully wet the mixing blades of the mixer and the mold. Apply release agent to the mold. Weigh out 559 parts of cement, 559 parts of fly ash, 402 parts of fine sand, 0 parts of RAP powder, 10.8 parts of water-reducing agent, 26 parts of polyvinyl alcohol fiber, and 274 parts of water according to the mass ratio. Soak the polyvinyl alcohol fiber in water for later use.

[0035] S3. Pour cement, fly ash, fine sand, water-reducing agent and RAP powder into a planetary mixer and mix at 100 rpm for 2 minutes. Slowly add water from the fiber and increase the mixer speed to 166 rpm. Mix for 3 minutes until the cement-based slurry is uniform. Then disperse the prepared polyvinyl alcohol fiber and mix at the same speed for 4-5 minutes to prepare a green high-performance cement-based composite material.

[0036] S4. The mixed slurry is cured to obtain a green high-performance cement-based composite material. In this invention, the preferred curing conditions include: room temperature, a temperature of 17-23°C, and a time of 1-3 days.

[0037] Performance testing:

[0038] Referring to the "Standard for Test Methods of Performance of Ordinary Concrete Mixtures" (GBT50080-2016) and "Recommendations for Design and Construction of High Performance Fiber Reinforced Cement Composites with Multiple Fine Cracks" (HPFRCC), the physical and mechanical properties of the obtained concrete were tested. The results showed that the average compressive strength at 28 days was 37.21 MPa; the average ultimate tensile strength was 3.28 MPa, the corresponding tensile strain was 4.73%, and the average self-weight was 2016.8 kg / m³. 3 .

[0039] Example 2

[0040] A method for preparing a green, high-performance cement-based composite material includes the following steps:

[0041] S1. After ball milling the waste asphalt mixture for 5-10 minutes, obtain the powder material for later use;

[0042] S2. First, thoroughly wet the mixing blades of the mixer and the mold with a damp cloth. Apply release agent to the mold. Weigh out 559 parts cement, 559 parts fly ash, 301.5 parts fine sand, 100.5 parts RAP powder, 10.8 parts water-reducing agent, 26 parts polyvinyl alcohol fiber, and 274 parts water according to the mass ratio. Soak the polyvinyl alcohol fiber in water for later use.

[0043] S3. Pour cement, fly ash, fine sand, water-reducing agent and RAP powder into a planetary mixer and mix at 100 rpm for 2 minutes. Slowly add water from the fiber and increase the mixer speed to 166 rpm. Mix for 3 minutes until the cement-based slurry is uniform. Then disperse the prepared polyvinyl alcohol fiber and mix at the same speed for 4-5 minutes to prepare ECC material.

[0044] S4. The mixed slurry is cured to obtain a green high-performance cement-based composite material. In this invention, the preferred curing conditions include: room temperature, a temperature of 17-23°C, and a time of 1-3 days.

[0045] Performance testing:

[0046] The physical and mechanical properties of the obtained concrete were tested according to the test method in Example 1. The results showed that the average compressive strength after 28 days was 39.73 MPa; the average ultimate tensile strength was 3.85 MPa, the corresponding tensile strain was 4.82%, and the average self-weight was 2002.1 kg / m³. 3 .

[0047] Example 3

[0048] A method for preparing a green, high-performance cement-based composite material includes the following steps:

[0049] S1. After ball milling the waste asphalt mixture for 5-10 minutes, obtain the powder material for later use;

[0050] S2. First, use a damp cloth to fully wet the mixing blades of the mixer and the mold. Apply a release agent to the mold. Weigh out 559 parts of cement, 559 parts of fly ash, 201 parts of fine sand, 201 parts of RAP powder, 10.8 parts of water-reducing agent, 26 parts of polyvinyl alcohol fiber, and 274 parts of water according to the mass ratio. Soak the polyvinyl alcohol fiber in water for later use.

[0051] S3. Pour cement, fly ash, fine sand, water-reducing agent and RAP powder into a planetary mixer and mix at 100 rpm for 2 minutes. Slowly add water from the fiber and increase the mixer speed to 166 rpm. Mix for 3 minutes until the cement-based slurry is uniform. Then disperse the prepared polyvinyl alcohol fiber and mix at the same speed for 4-5 minutes to prepare ECC material.

[0052] S4. The mixed slurry is cured to obtain a green high-performance cement-based composite material. In this invention, the preferred curing conditions include: room temperature, a temperature of 17-23°C, and a time of 1-3 days.

[0053] Performance testing:

[0054] The physical and mechanical properties of the obtained concrete were tested according to the test method in Example 1. The results showed that the average compressive strength after 28 days was 42.74 MPa; the average ultimate tensile strength was 4.32 MPa, the corresponding tensile strain was 5.04%, and the average self-weight was 2085.3 kg / m³. 3 .

[0055] Example 4

[0056] A method for preparing a green, high-performance cement-based composite material includes the following steps:

[0057] S1. After ball milling the waste asphalt mixture for 5-10 minutes, obtain the powder material for later use;

[0058] S2. First, thoroughly wet the mixing blades of the mixer and the mold with a damp cloth. Apply release agent to the mold. Weigh out 559 parts cement, 559 parts fly ash, 160.8 parts fine sand, 241.2 parts RAP powder, 10.8 parts water-reducing agent, 26 parts polyvinyl alcohol fiber, and 274 parts water according to the mass ratio. Soak the polyvinyl alcohol fiber in water for later use.

[0059] S3. Pour cement, fly ash, fine sand, water-reducing agent and RAP powder into a planetary mixer and mix at 100 rpm for 2 minutes. Slowly add water from the fiber and increase the mixer speed to 166 rpm. Mix for 3 minutes until the cement-based slurry is uniform. Then disperse the prepared polyvinyl alcohol fiber and mix at the same speed for 4-5 minutes to prepare ECC material.

[0060] S4. The mixed slurry is cured to obtain a green high-performance cement-based composite material. In this invention, the preferred curing conditions include: room temperature, a temperature of 17-23°C, and a time of 1-3 days.

[0061] Performance testing:

[0062] The physical and mechanical properties of the obtained concrete were tested according to the test method in Example 1. The results showed that the average compressive strength after 28 days was 46.63 MPa; the average ultimate tensile strength was 4.70 MPa, the corresponding tensile strain was 3.21%, and the average self-weight was 2059.2 kg / m³. 3 .

[0063] Example 5

[0064] A method for preparing a green, high-performance cement-based composite material includes the following steps:

[0065] S1. After ball milling the waste asphalt mixture for 5-10 minutes, obtain the powder material for later use;

[0066] S2. First, use a damp cloth to fully wet the mixing blades of the mixer and the mold. Apply release agent to the mold. Weigh out 559 parts of cement, 559 parts of fly ash, 0 parts of fine sand, 402 parts of RAP powder, 10.8 parts of water-reducing agent, 26 parts of polyvinyl alcohol fiber, and 274 parts of water according to the mass ratio. Soak the polyvinyl alcohol fiber in water for later use.

[0067] S3. Pour cement, fly ash, fine sand, water-reducing agent and RAP powder into a planetary mixer and mix at 100 rpm for 2 minutes. Slowly add water from the fiber and increase the mixer speed to 166 rpm. Mix for 3 minutes until the cement-based slurry is uniform. Then disperse the prepared polyvinyl alcohol fiber and mix at the same speed for 4-5 minutes to prepare ECC material.

[0068] S4. The mixed slurry is cured to obtain a green high-performance cement-based composite material. In this invention, the preferred curing conditions include: room temperature, a temperature of 17-23°C, and a time of 1-3 days.

[0069] Performance testing:

[0070] The physical and mechanical properties of the obtained concrete were tested according to the test method in Example 1. The results showed that the average compressive strength at 28 days was 39.53 MPa; the average ultimate tensile strength was 4.54 MPa, the corresponding tensile strain was 2.81%, and the average self-weight was 2021.2 kg / m³. 3 .

[0071] The test results above show that the present invention provides a waste asphalt mixture to replace fine sand and develops a new type of green engineering cement-based composite material. Compared with the control group, the material prepared in Example 3 has a slightly increased self-weight, a 15% increase in compressive strength, a 14% increase in ultimate tensile strength, and a larger ultimate tensile strain, exhibiting stronger ductility and stability. It makes full use of waste asphalt mixture to reduce the increasing environmental damage caused by solid waste and provides a new green material for complex engineering projects.

[0072] Contents not described in detail in this specification are existing technologies known to those skilled in the art. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A green high performance cementitious composite material and its preparation, characterized in that the raw materials include, by weight parts: Water 274 parts, fly ash 559 parts, cement 559 parts, fine sand 201 parts, waste asphalt mixture powder 201 parts, and water reducing agent 10.8 parts, and 2% polyvinyl alcohol fiber by volume is added to each cubic meter of the cement-based composite material.

2. Green high performance cementitious composite material according to claim 1, characterized in that, Raw materials include, by weight: water 274 parts, fly ash 559 parts, cement 559 parts, fine sand 201 parts, waste asphalt mixture powder 201 parts, and water reducing agent 10.8 parts, and 2% polyvinyl alcohol fiber by volume is added to each cubic meter of the cement-based composite material.

3. The green high-performance cementitious composite material of claim 1, wherein, The waste asphalt mixture powder preparation method is: The recovered block-shaped waste asphalt mixture is manually coarsely crushed to obtain RAP coarse aggregate. The RAP coarse aggregate is placed in an ore crushing ball mill for fine crushing to obtain RAP fine aggregate. The RAP fine aggregate is screened to obtain waste asphalt mixture powder.

4. The green high-performance cementitious composite material of claim 3, wherein, The asphalt content in the block-shaped waste asphalt mixture is 5% to 7%.

5. The green high performance cementitious composite material of claim 3, wherein, The RAP coarse aggregate particle size is 5 to 8 mm.

6. The green high-performance cementitious composite material of claim 3, wherein, The waste asphalt mixture powder mesh size is 30 to 300 mesh.

7. The green high-performance cementitious composite material of claim 1, wherein, The water is tap water.

8. The green high-performance cementitious composite material of claim 1, wherein, The cement is P.0.42.5 cement.

9. The green high-performance cementitious composite material of claim 1, wherein, The fly ash is secondary fly ash.

10. The green high-performance cementitious composite material of claim 1, wherein, The fine sand is continuously graded fine sand with a fineness modulus of 1.6 to 2.

2.

11. The green high-performance cementitious composite material of claim 1, wherein, The water reducing agent has a water-reducing rate of greater than or equal to 30%.

12. The green high-performance cementitious composite material of claim 1, wherein, The tensile strength of the polyvinyl alcohol fiber is 1620 MPa, the elastic modulus is 42.8 GPa, the diameter is 39 μm, the length is 8 mm, and the volume usage is 2%.

13. A method of producing a high performance, cementitious composite material as claimed in any one of claims 1 to 12, characterised in that, The method comprises the following steps: grinding waste asphalt mixture into powder material for standby; soaking polyvinyl alcohol fiber in water for standby; mixing and stirring cement, fly ash, fine sand, and waste asphalt mixture powder; adding water reducing agent and part of water to the stirred mixture and stirring, then adding standby polyvinyl alcohol fiber and water, and stirring again to obtain the cement-based composite material. The method comprises the following steps: grinding waste asphalt mixture into powder material for standby; soaking polyvinyl alcohol fiber in water for standby; mixing and stirring cement, fly ash, fine sand, and waste asphalt mixture powder; adding water reducing agent and part of water to the stirred mixture and stirring, then adding standby polyvinyl alcohol fiber and water, and stirring again to obtain the cement-based composite material.

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