Phosphogypsum light weight high ductility cement-based composite material and preparation method thereof

Abstract

This invention discloses a lightweight, high-ductility cement-based composite material made of phosphogypsum, belonging to the field of building materials technology. The high-ductility cement-based composite material of this invention comprises the following raw materials in parts by weight: 450-600 parts cement, 150-300 parts fly ash, 100-300 parts silica fume, 400-500 parts lightweight phosphogypsum aggregate, 200-300 parts elastic asphalt sand, 12-18 parts composite fiber, 60-90 parts steel fiber, 20-30 parts water-reducing agent, and 170-200 parts water. The preparation method of the elastic asphalt sand includes the following steps: screening waste asphalt concrete to obtain waste asphalt sand; washing the waste asphalt sand with an organic solvent, drying it, soaking it in industrial oil, and drying it to obtain elastic waste asphalt sand; adding the elastic waste asphalt sand to a mixed solution of water, a silane coupling agent, and anhydrous ethanol, reacting, filtering, and drying to obtain the elastic asphalt sand. The lightweight, high-ductility cement-based composite material of the present invention has the advantages of being lightweight, having low shrinkage, high tensile strength, and high impact strength.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, and in particular to a phosphogypsum lightweight high-ductility cement-based composite material and its preparation method. Background Technology

[0002] Nuclear engineering facilities, as critical infrastructure for national security and development, are vulnerable to damage from precision strikes by high-tech weapons, explosions, or earthquakes. Such damage would not only cause enormous losses to national property but also pose environmental risks. Concrete, as the primary structural material in nuclear engineering construction, serves both to shield against radiation and as a vital safety guarantee for nuclear facilities; its mechanical properties are crucial to the safety of the entire nuclear project. Traditional cement-based materials have tensile strengths far lower than compressive strengths. During service, when subjected to bending loads exceeding the material's ultimate tensile strength, structural cracking and failure can occur. Currently, the design strength of radiation-shielding concrete is generally low, mostly not exceeding 60 MPa. Traditional high-ductility cement-based materials only contain organic fibers, which have limited absorption of vibrations under high-strain impact conditions. Therefore, there is an urgent need to develop cement-based materials with high strength, excellent impact resistance, and radiation protection properties to meet the safety protection needs of my country's national defense and civilian nuclear engineering projects.

[0003] During highway maintenance in my country, a large amount of waste pavement is generated, which, after being crushed, yields waste asphalt sand, a valuable impact-resistant material. However, current research on using waste asphalt sand to prepare cement-based materials is limited. Furthermore, phosphogypsum is an industrial waste residue from the sulfuric acid treatment of phosphate rock to produce phosphoric acid. Currently, my country's phosphogypsum stockpile has reached approximately 700 million tons, and is increasing at a rate of about 80 million tons per year. The stockpiling of phosphogypsum not only occupies significant land resources, but the leaching of impurities such as fluorides and free phosphoric acid also causes serious pollution to the surrounding environment and groundwater. These adverse effects have become sensitive issues restricting the sustainable development of the phosphate chemical industry. Currently, the application of phosphogypsum in the construction concrete field suffers from the problem of excessive ettringite formation leading to the destruction of cement-based materials, thus limiting its large-scale application. How to achieve large-scale resource utilization of phosphogypsum is also an urgent problem to be solved. Therefore, it is necessary to invent a lightweight, high-ductility cement-based composite material using waste asphalt sand and phosphogypsum. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a lightweight, high-ductility cement-based composite material made from phosphogypsum and its preparation method. The lightweight, high-ductility cement-based composite material of this invention exhibits high tensile strength and impact strength. Specifically, this is achieved through the following techniques.

[0005] A lightweight, high-ductility cement-based composite material made of phosphogypsum comprises the following raw materials in parts by weight: 450-600 parts cement, 150-300 parts fly ash, 100-300 parts silica fume, 400-500 parts lightweight phosphogypsum aggregate, 200-300 parts elastic asphalt sand, 12-18 parts composite fiber, 60-90 parts steel fiber, 20-30 parts water-reducing agent, and 170-200 parts water.

[0006] The preparation method of elastic asphalt sand includes the following steps:

[0007] Waste asphalt concrete is crushed and screened to obtain waste asphalt sand;

[0008] The waste asphalt sand is washed with organic solvent, dried, then soaked in industrial oil and dried to obtain elastic waste asphalt sand;

[0009] The elastic waste asphalt sand is immersed in a silane coupling agent solution, filtered, and dried to obtain elastic asphalt sand.

[0010] Generally, the waste asphalt concrete of this invention can be obtained from the on-site milling and crushing of an old road, or from the overall excavation of an old road followed by crushing at a mixing plant. Washing the waste asphalt sand with an organic solvent ensures that the solvent fully and evenly coats the surface, eroding and swelling it to remove impurities and loosen the surface for better impact resistance. The washing process does not cause complete dissolution or loss of the asphalt. After washing and drying, the waste asphalt sand is soaked in industrial oil. The oil penetrates the loose asphalt sand, further thickening, elasticizing, and softening the asphalt layer on the surface. After drying to remove excess oil, it is then fully contacted with a silane coupling agent. The silane coupling agent polarizes the asphalt sand surface, creating a good interface between the asphalt sand and the cement-based material, thus forming a rigid and elastic impact-resistant material.

[0011] In this invention, phosphogypsum lightweight aggregate and composite fibers form a prestressed field within the concrete, thereby improving the mechanical properties of cement-based materials under impact. Due to the expansion of ettringite formed on the surface of the phosphogypsum lightweight aggregate, prestress is generated within the cement-based material along with the blended fibers, significantly enhancing its impact resistance. Compared to traditional high-ductility cement-based materials, the lightweight high-ductility cement-based composite material of this invention exhibits a significantly reduced probability of internal damage under the same impact load. During the cement hydration process, the calcium sulfate in the phosphogypsum lightweight aggregate reacts with the cement to generate ettringite, which has an expansion effect, effectively inhibiting the shrinkage of the cement-based composite material.

[0012] Preferably, the dosage of the silane coupling agent is 1-2% of the mass of the elastic waste asphalt sand.

[0013] Preferably, the sieve mesh size is 1-2.5 mm, and the asphalt content accounts for 10% of the total weight of the waste asphalt sand.

[0014] Preferably, the solvent is water and anhydrous ethanol, and the mass ratio of water, silane coupling agent and anhydrous ethanol is 1:(3-6):(4-7).

[0015] Preferably, the rinsing conditions are: time of 5-8 min and flow rate of 0.2-0.5 ml / s.

[0016] Preferably, the soaking time is 0.5-2 hours.

[0017] Preferably, the soaking time is 1-2 hours.

[0018] Preferably, the silane coupling agent includes at least one of the following types: KH550, A151, or A171.

[0019] Preferably, the organic solvent includes at least one of carbon tetrachloride solution, tetrahydrofuran solution, or acetone solution.

[0020] Preferably, the industrial oil includes at least one of microcrystalline wax oil, white oil, or light lubricating oil.

[0021] Preferably, the method for preparing phosphogypsum lightweight aggregate includes the following steps:

[0022] Phosphogypsum and alkali activator are ground, mixed, and granulated to obtain phosphogypsum aggregate;

[0023] The phosphogypsum aggregate is crushed and sieved to obtain phosphogypsum lightweight sand;

[0024] The phosphogypsum lightweight sand is impregnated in a polymer solution and dried to obtain phosphogypsum lightweight aggregate.

[0025] This invention uses a polymer solution to impregnate phosphogypsum aggregate, which can seal the pores inside the crushed phosphogypsum, solving the problem of excessive ettringite formation causing damage to cement-based materials. At the same time, the adhesive effect of the polymer can be used to bond the micro-cracks inside the crushed phosphogypsum aggregate, thereby improving the strength of phosphogypsum lightweight sand.

[0026] The phosphogypsum lightweight aggregate of this invention has a porous and rough surface with numerous capillary pores. This structure not only improves the bond strength between the aggregate and cement mortar but also gives the phosphogypsum lightweight aggregate a "slow-release water" effect. That is, after soaking in clean water, the phosphogypsum lightweight aggregate becomes pre-wetted aggregate. After concrete molding, it slowly releases internal moisture over time, allowing the concrete to achieve sufficient internal curing, significantly reducing autogenous shrinkage and drying shrinkage. This greatly improves the volume stability of cement-based materials, enhances the density and strength of concrete, extends the service life of buildings, and improves the durability of cement-based composite materials.

[0027] The phosphogypsum lightweight aggregate of the present invention contains a large amount of calcium sulfate dihydrate (CaSO4·2H2O) and a large amount of water of crystallization. Since the water of crystallization structure has a strong inhibitory effect on neutron radiation, the lightweight high ductility cement-based composite material of the present invention can be used as a military-grade impact-resistant and radiation-proof cement-based material.

[0028] More preferably, the mass ratio of phosphogypsum to alkali activator is 10:(8-12).

[0029] More preferably, the alkaline activator is sodium hydroxide and / or water glass.

[0030] More preferably, the polymer solution includes at least one of a polyurethane solution, a sodium polyacrylate solution, or a polyvinyl alcohol solution.

[0031] More preferably, the polymer solution includes at least one of the following: a polyurethane solution with a mass fraction of 10%-50%, a sodium polyacrylate solution with a mass fraction of 0.5%-2%, or a polyvinyl alcohol solution with a mass fraction of 5%-20%.

[0032] More preferably, the soaking time is 0.5-2 hours.

[0033] Preferably, the fly ash is fly ash microspheres with a loss on ignition ≤5.5%, a water requirement ratio ≤90%, and a spherical particle volume fraction ≥92%.

[0034] Preferably, the silica fume contains ≥95% SiO2 by mass and has a specific surface area ≥14500 m². 2 / kg, 28d activity index ≥100%.

[0035] Preferably, the composite fiber comprises polyethylene fiber, polyvinyl alcohol fiber and polyester fiber in a mass ratio of 10:(9-11):(8-12).

[0036] More preferably, the polyethylene fiber has a length of 9-14 mm, a diameter of 0.021-0.050 mm, a tensile strength >3000 MPa, and an elastic modulus >85 GPa.

[0037] More preferably, the polyvinyl alcohol fiber has a length of 5-10 mm, a diameter of 0.01-0.045 mm, a tensile strength >1550 MPa, and an elastic modulus of 40-50 GPa.

[0038] More preferably, the polyester fiber has a length of 12-18 mm, a diameter of 0.02-0.04 mm, a tensile strength of 400-900 MPa, and an elastic modulus ≥4 GPa.

[0039] Preferably, the steel fiber is an end-hooked steel fiber with a length of 30-40 mm, a diameter of 0.50-0.60 mm, and a tensile strength >1600 MPa.

[0040] Preferably, the water-reducing agent is a polycarboxylate water-reducing agent with a water reduction rate >30%.

[0041] Preferably, the water is ordinary tap water that meets the requirements of the "Standard for Water Used in Concrete" (JGJ63-2016).

[0042] The preparation method of the above-mentioned lightweight, high-ductility cement-based composite material includes the following steps:

[0043] Lightweight phosphogypsum aggregate is pre-wetted in water until saturated to obtain pre-wetted aggregate;

[0044] The pre-wetted aggregate is mixed with the cement, silica fume, and fly ash, the water-reducing agent and water are added and mixed, and then the composite fiber and steel fiber are added and mixed to obtain the initial cement-based material.

[0045] After the initial cement-based material is molded, vibrated, shaped, and cured, a lightweight, high-ductility cement-based composite material is obtained.

[0046] This invention utilizes pre-wetted phosphogypsum aggregate and elastic asphalt sand as aggregates to prepare a lightweight, high-ductility cement-based composite material with high impact resistance, which can solve the problem of industrial solid waste treatment and is beneficial to environmental protection. By leveraging the internal curing effect of porous phosphogypsum lightweight aggregate, the problem of high shrinkage in cement-based composite materials is mitigated to some extent. Furthermore, it effectively addresses the current scarcity of aggregates commonly used in high-toughness concrete and the problem of large-scale phosphogypsum accumulation, saving resources and energy. The elastic asphalt sand prepared from waste asphalt pavement materials effectively utilizes solid waste. The use of water-reducing agents and fly ash microspheres and other mineral admixtures optimizes the workability of the concrete mixture, improves its density and homogeneity, further reduces shrinkage, and enhances the mechanical properties and volumetric stability of high-toughness concrete. This invention combines the "slow-release water" effect of phosphogypsum lightweight aggregate and pre-wetted aggregate to effectively improve the crack resistance and volumetric stability of cement-based composite materials, while also optimizing the pore structure of concrete and improving its durability.

[0047] Compared with the prior art, the advantages of the present invention are:

[0048] 1. This invention modifies waste asphalt concrete into elastic asphalt sand, which is used as a raw material for cement-based materials. On the one hand, it improves the ability of cement-based materials to absorb and dissipate vibration energy when subjected to impact, effectively solving the problem of insufficient impact resistance of traditional cement-based materials. On the other hand, elastic asphalt sand can also be used as part of fine aggregate, making full use of solid waste and saving energy.

[0049] 2. This invention uses a polymer solution to impregnate lightweight phosphogypsum sand, which can seal the pores inside the crushed phosphogypsum. This ensures that excessive ettringite is not generated, which could damage the cement-based material. Furthermore, the adhesive effect of the polymer helps to bond the micro-cracks inside the crushed lightweight phosphogypsum sand, thus improving its strength. Since phosphogypsum aggregate is lightweight, its incorporation reduces the self-weight of the cement-based material, expanding its application scenarios.

[0050] 3. The lightweight, high-ductility cement-based composite material of the present invention has the advantages of being lightweight, having low shrinkage, high tensile strength, and high impact strength;

[0051] 4. The phosphogypsum lightweight aggregate of the present invention contains a large amount of calcium sulfate dihydrate (CaSO4·2H2O) and a large amount of water of crystallization. Since the water of crystallization structure has a strong inhibitory effect on neutron radiation, the lightweight high ductility cement-based composite material of the present invention can be used as a military-grade impact-resistant and radiation-proof cement-based material.

[0052] 5. This invention enables the utilization of waste asphalt concrete and phosphogypsum, which is beneficial to environmental protection. Detailed Implementation

[0053] To further illustrate the present invention, the technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0054] This invention provides a lightweight, high-ductility cement-based composite material made of phosphogypsum, comprising the following raw materials in parts by weight: 450-600 parts cement, 150-300 parts fly ash, 100-300 parts silica fume, 400-500 parts lightweight phosphogypsum aggregate, 200-300 parts elastic asphalt sand, 12-18 parts composite fiber, 60-90 parts steel fiber, 20-30 parts water-reducing agent, and 170-200 parts water.

[0055] The preparation method of elastic asphalt sand includes the following steps:

[0056] Waste asphalt concrete is crushed and screened to obtain waste asphalt sand;

[0057] The waste asphalt sand is washed with organic solvent, and after the surface of the waste asphalt sand is dried, it is soaked in small molecule industrial oil. After soaking, it is heated at low temperature or air-dried naturally to remove excess oil from the surface of the elastic waste asphalt sand, thus obtaining elastic waste asphalt sand.

[0058] The elastic waste asphalt sand is immersed in a silane coupling agent solution, filtered, and dried to obtain elastic asphalt sand.

[0059] Optionally, the dosage of the silane coupling agent is 1-2% of the mass of the elastic waste bitumen sand.

[0060] Optionally, the sieve size is 1-2.5 mm, and the asphalt content accounts for 10% of the total weight of the waste asphalt sand.

[0061] Optionally, the solvent is water and anhydrous ethanol, and the mass ratio of water, silane coupling agent and anhydrous ethanol is 1:(3-6):(4-7).

[0062] Optionally, the rinsing conditions are: time of 5-8 minutes and flow rate of 0.2-0.5 ml / s.

[0063] Optionally, the soaking time is 0.5-2 hours.

[0064] Optionally, the soaking time is 1-2 hours.

[0065] Optionally, the silane coupling agent includes at least one of the following types: KH550, A151, or A171.

[0066] Optionally, the organic solvent includes at least one of carbon tetrachloride solution, tetrahydrofuran solution, or acetone solution.

[0067] Alternatively, the industrial oil includes at least one of microcrystalline wax oil, white oil, or light lubricating oil.

[0068] Optionally, the preparation method of phosphogypsum lightweight aggregate includes the following steps:

[0069] Phosphogypsum and alkali activator are ground, mixed, and granulated to obtain phosphogypsum aggregate;

[0070] The phosphogypsum aggregate is crushed and sieved to obtain phosphogypsum lightweight sand;

[0071] The phosphogypsum lightweight sand is impregnated in a polymer solution and dried to obtain phosphogypsum lightweight aggregate.

[0072] Further optionally, the mass ratio of phosphogypsum to alkali activator is 10:(8-12).

[0073] Further, optionally, the alkaline activator is sodium hydroxide and / or water glass.

[0074] Further optionally, the polymer solution includes at least one of a polyurethane solution, a sodium polyacrylate solution, or a polyvinyl alcohol solution.

[0075] Further optionally, the polymer solution includes at least one of the following: a polyurethane solution with a mass fraction of 10%-50%, a sodium polyacrylate solution with a mass fraction of 0.5%-2%, or a polyvinyl alcohol solution with a mass fraction of 5%-20%.

[0076] Alternatively, the soaking time may be 0.5-2 hours.

[0077] Optionally, the fly ash is fly ash microspheres with a loss on ignition ≤5.5%, water requirement ratio ≤90%, and spherical particle volume fraction ≥92%.

[0078] Optionally, the silica fume contains ≥95% SiO2 by mass and has a specific surface area ≥14500 m². 2 / kg, 28d activity index ≥100%.

[0079] Optionally, the composite fiber comprises polyethylene fiber, polyvinyl alcohol fiber, and polyester fiber in a mass ratio of 10:(9-11):(8-12). Further optionally, the polyethylene fiber has a length of 9-14 mm, a diameter of 0.021-0.050 mm, a tensile strength >3000 MPa, and an elastic modulus >85 GPa. Further optionally, the polyvinyl alcohol fiber has a length of 5-10 mm, a diameter of 0.01-0.045 mm, a tensile strength >1550 MPa, and an elastic modulus of 40-50 GPa. Further optionally, the polyester fiber has a length of 12-18 mm, a diameter of 0.02-0.04 mm, a tensile strength of 400-900 MPa, and an elastic modulus ≥4 GPa.

[0080] Optionally, the steel fiber is an end-hooked steel fiber with a length of 30-40mm, a diameter of 0.50-0.60mm, and a tensile strength >1600MPa.

[0081] Optionally, the water-reducing agent is a polycarboxylate water-reducing agent with a water reduction rate >30%.

[0082] Optionally, the water is ordinary tap water that meets the requirements of the "Standard for Water Used in Concrete" (JGJ63-2016).

[0083] The preparation method of the above-mentioned lightweight, high-ductility cement-based composite material includes the following steps:

[0084] Lightweight phosphogypsum aggregate is pre-wetted in water until saturated to obtain pre-wetted aggregate;

[0085] The pre-wetted aggregate is mixed with the cement, silica fume, and fly ash, the water-reducing agent and water are added and mixed, and then the composite fiber and steel fiber are added and mixed to obtain the initial cement-based material.

[0086] After the initial cement-based material is molded, vibrated, shaped, and cured, a lightweight, high-ductility cement-based composite material is obtained.

[0087] Optionally, the pre-wetting time shall not be less than 5 hours.

[0088] The technical solution 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0089] In the following examples and comparative examples, the cement used was 52.5 grade ordinary Portland cement, which was sourced from Huaxin Cement Co., Ltd.

[0090] In the following examples and comparative examples, the fly ash used was fly ash microspheres. The fly ash microspheres all met the requirements of loss on ignition ≤ 5.5%, water requirement ratio ≤ 90%, and spherical particle volume fraction ≥ 92%, and were sourced from Tianjin Zhucheng Materials Co., Ltd.

[0091] In the following examples and comparative examples, the silica fume used was the same, and the silica fume all met the requirements of SiO2 mass content ≥95% and specific surface area ≥14500 m². 2 / kg, 28d activity index ≥100%, sourced from Sika (China) Co., Ltd.

[0092] In the following examples and comparative examples, the polyethylene fibers used in the composite fibers all meet the following requirements: length 9-14 mm, diameter 0.021-0.050 mm, tensile strength greater than 3000 MPa, and elastic modulus greater than 85 GPa. They are sourced from Wuhan Xintu Engineering New Materials Technology Co., Ltd.

[0093] In the following examples and comparative examples, the polyvinyl alcohol fibers used in the composite fibers all meet the following requirements: length 5-10 mm, diameter 0.01-0.045 mm, tensile strength greater than 1550 MPa, and elastic modulus 40-50 GPa. The fibers are sourced from Wuhan Xintu Engineering New Materials Technology Co., Ltd.

[0094] In the following examples and comparative examples, the polyester fibers used in the composite fibers all meet the following requirements: length 12-18mm, diameter 0.02-0.04mm, tensile strength 400-900MPa, and elastic modulus not less than 4GPa. They are sourced from Wuhan Xintu Engineering New Materials Technology Co., Ltd.

[0095] In the following examples and comparative examples, all steel fibers used are end-hooked steel fibers with a length of 35 mm, a diameter of 0.55 mm, and a tensile strength of 1600 MPa, sourced from Wuhan Xintu Engineering New Materials Technology Co., Ltd.

[0096] In the following examples and comparative examples, the water-reducing agents used are all polycarboxylate superplasticizers with a water reduction rate greater than 30%, sourced from Subote New Material Co., Ltd.

[0097] The phosphogypsum of the present invention is not particularly limited, and any phosphogypsum known to those skilled in the art can be used.

[0098] In the following examples and comparative examples, the phosphogypsum was sourced from a phosphogypsum stockpile in Yichang, Hubei Province; the waste asphalt concrete was recycled from milled asphalt concrete used for the surface layer of a first-class highway (9.5 years of service).

[0099] In the following examples and comparative examples, the water used was ordinary tap water, which met the requirements of the "Standard for Water Used in Concrete" (JGJ63-2016).

[0100] Example 1

[0101] This embodiment provides a phosphogypsum lightweight high-ductility cement-based composite material, comprising the following raw materials in parts by weight: 600 parts cement, 150 parts fly ash, 190 parts silica fume, 500 parts phosphogypsum lightweight aggregate, 200 parts elastic asphalt sand, 12 parts composite fiber, 90 parts hooked steel fiber, 20 parts water-reducing agent, and 200 parts water.

[0102] Among them, the weight ratio of polyethylene fiber, polyvinyl alcohol fiber and polyester fiber in the composite fiber is 100:90:110.

[0103] The method for preparing phosphogypsum lightweight aggregate in this embodiment includes the following steps:

[0104] S1. Phosphogypsum and sodium hydroxide are ground and mixed at a mass ratio of 100:80. The mixture is then granulated using a power scraper disc pelletizer at a 50° inclination angle and a rotation speed of 30 r / min. The pelletizer is cured at room temperature for 24 hours to obtain phosphogypsum aggregate with a particle size of 2-4 mm and a density of 875 kg / m³. 3 The cylinder compressive strength is 8.5 MPa;

[0105] S2. The phosphogypsum aggregate from step S1 is crushed by a vertical shaft impact crusher with a rotation speed of 1000 r / min and a feed rate of 50 kg / s. After screening by a screening machine, phosphogypsum lightweight sand is obtained with a particle size of less than 2.36 mm and a fineness modulus of 2.5-2.7.

[0106] S3. The phosphogypsum lightweight sand from step S2 is immersed in a 35wt% polyurethane solution for 1.5 hours, then air-dried to remove excess solution from the surface of the phosphogypsum lightweight sand, thus obtaining phosphogypsum lightweight aggregate.

[0107] The preparation method of elastic asphalt sand in this embodiment includes the following steps:

[0108] P1. Waste asphalt concrete is screened to obtain waste asphalt sand with a particle size range of 1.18-2.36mm and an asphalt content of 10%.

[0109] P2. Use 100% carbon tetrachloride solution to quickly rinse the surface of the waste asphalt sand in step P1 for 8 minutes at a flow rate of 0.2 mL / s, dry it, then soak it in microcrystalline paraffin oil for 1.5 hours and air dry it naturally to obtain elastic waste asphalt sand.

[0110] P3. Prepare two types of silane coupling agents, KH550 and A171, with a total dosage of 1% of the mass of the elastic waste asphalt sand. The mass ratio of the two types of silane coupling agents is 1:1. Then, prepare a mixed solution with a mass ratio of deionized water:silane coupling agent:anhydrous ethanol of 10:50:40. Add the elastic waste asphalt sand from step P2, hydrolyze for 2 hours, filter, and heat to dry to obtain the elastic asphalt sand.

[0111] The preparation method of the lightweight, high-ductility cement-based composite material in this embodiment includes the following steps:

[0112] A1: Immerse the phosphogypsum lightweight aggregate in water for 7 hours to pre-wet it and obtain pre-wetted aggregate;

[0113] A2: Mix the pre-wetted aggregate from step A1 with cement, silica fume, fly ash, and elastic asphalt sand for 3 minutes, then add water and water-reducing agent and mix for 3 minutes, and finally add composite fiber and hooked steel fiber and continue mixing for 3 minutes to obtain the initial cement-based material.

[0114] A3: After molding, vibrating and shaping the initial cement-based material in step A2, cover the surface with an impermeable film for film curing, then remove the mold and place it in a standard curing environment for 28 days to obtain a lightweight and high-ductility cement-based composite material.

[0115] Example 2

[0116] This embodiment provides a phosphogypsum lightweight high-ductility cement-based composite material, comprising the following raw materials in parts by weight: 450 parts cement, 300 parts fly ash, 100 parts silica fume, 450 parts phosphogypsum lightweight aggregate, 250 parts elastic asphalt sand, 15 parts composite fiber, 75 parts hooked steel fiber, 30 parts water-reducing agent, and 170 parts water.

[0117] Among them, the weight ratio of polyethylene fiber, polyvinyl alcohol fiber and polyester fiber in the composite fiber is 100:90:120.

[0118] The method for preparing phosphogypsum lightweight aggregate in this embodiment includes the following steps:

[0119] S1. Phosphogypsum and water glass (modulus n = 1.5) are mixed at a mass ratio of 100:100, and then granulated using a power scraper disc pelletizer. The pelletizer is tilted at 60° and rotated at 40 r / min. After curing at room temperature for 24 hours, phosphogypsum aggregate with a particle size of 2-4 mm and a density of 875 kg / m³ is obtained. 3 The cylinder compressive strength is 8.5 MPa;

[0120] S2. The phosphogypsum aggregate from step S1 is crushed by a vertical shaft impact crusher with a rotation speed of 1300 r / min and a feed rate of 50 kg / s. After screening by a screening machine, phosphogypsum lightweight sand is obtained with a particle size of less than 2.36 mm and a fineness modulus of 2.5-2.7.

[0121] S3. The phosphogypsum lightweight sand from step S2 is immersed in a 1.5wt% sodium polyacrylate solution for 1 hour, then air-dried to remove excess solution from the surface of the phosphogypsum lightweight sand, thus obtaining phosphogypsum lightweight aggregate.

[0122] The preparation method of elastic asphalt sand in this embodiment includes the following steps:

[0123] P1. Waste asphalt concrete is screened to obtain waste asphalt sand with a particle size range of 1.18-2.36mm and an asphalt content of 10%.

[0124] P2. Use a 100% tetrahydrofuran solution to quickly rinse the surface of the waste asphalt sand from step P1 for 6 minutes at a flow rate of 0.4 mL / s. Dry it, then soak it in white oil for 1 hour and air dry it naturally to obtain elastic waste asphalt sand.

[0125] P3. Prepare A151 type silane coupling agent with a dosage of 1.5% of the mass of elastic waste asphalt sand; then prepare a mixed solution with a mass ratio of deionized water: silane coupling agent: anhydrous ethanol of 10:60:70, add the elastic waste asphalt sand from step P2, hydrolyze for 1.5 hours, filter, heat and dry to obtain the elastic asphalt sand.

[0126] The preparation method of the lightweight, high-ductility cement-based composite material in this embodiment includes the following steps:

[0127] A1: Immerse the phosphogypsum lightweight aggregate in water for 5 hours to pre-wet it and obtain pre-wetted aggregate;

[0128] A2: Mix the pre-wetted aggregate from step A1 with cement, silica fume, fly ash, and elastic asphalt sand for 3 minutes, then add water and water-reducing agent and mix for 3 minutes, and finally add composite fiber and hooked steel fiber and continue mixing for 3 minutes to obtain the initial cement-based material.

[0129] A3: After molding, vibrating and shaping the initial cement-based material in step A2, cover the surface with an impermeable film for film curing, then remove the mold and place it in a standard curing environment for 28 days to obtain a lightweight and high-ductility cement-based composite material.

[0130] Example 3

[0131] This embodiment provides a phosphogypsum lightweight high-ductility cement-based composite material, comprising the following raw materials in parts by weight: 490 parts cement, 150 parts fly ash, 300 parts silica fume, 400 parts phosphogypsum lightweight aggregate, 300 parts elastic asphalt sand, 18 parts composite fiber, 60 parts hooked steel fiber, 20 parts water-reducing agent, and 200 parts water.

[0132] Among them, the weight ratio of polyethylene fiber, polyvinyl alcohol fiber and polyester fiber in the composite fiber is 100:110:80.

[0133] The method for preparing phosphogypsum lightweight aggregate in this embodiment includes the following steps:

[0134] S1. Phosphogypsum and water glass (modulus n = 1.5) are mixed at a mass ratio of 100:120, and then granulated using a power scraper disc pelletizer. The pelletizer is tilted at 70° and rotated at 50 r / min. The mixture is then cured at room temperature for 24 hours to obtain phosphogypsum aggregate with a particle size of 2-4 mm and a density of 875 kg / m³. 3 The cylinder compressive strength is 8.5 MPa;

[0135] S2. The phosphogypsum aggregate from step S1 is crushed by a vertical shaft impact crusher with a rotation speed of 1500 r / min and a feed rate of 70 kg / s. After screening by a screening machine, phosphogypsum lightweight sand is obtained with a particle size of less than 2.36 mm and a fineness modulus of 2.5-2.7.

[0136] S3. The phosphogypsum lightweight sand from step S2 is immersed in a 15wt% polyvinyl alcohol solution for 2 hours, then air-dried to remove excess solution from the surface of the phosphogypsum lightweight sand, thus obtaining phosphogypsum lightweight aggregate.

[0137] The preparation method of elastic asphalt sand in this embodiment includes the following steps:

[0138] P1. Waste asphalt concrete is screened to obtain waste asphalt sand with a particle size range of 1.18-2.36mm and an asphalt content of 10%.

[0139] P2. Use a 70% acetone solution to quickly rinse the surface of the waste asphalt sand from step P1 for 5 minutes at a flow rate of 0.5 mL / s. Dry it, then soak it in light lubricating oil for 2 hours and air dry it naturally to obtain elastic waste asphalt sand.

[0140] P3. Prepare A171 type silane coupling agent at a dosage of 2% of the mass of elastic waste asphalt sand; then prepare a mixed solution according to the mass ratio of deionized water: silane coupling agent: anhydrous ethanol of 10:30:60, add the elastic waste asphalt sand from step P2, hydrolyze for 1 hour, filter, heat and dry to obtain the elastic asphalt sand.

[0141] The preparation method of the lightweight, high-ductility cement-based composite material in this embodiment includes the following steps:

[0142] A1: Immerse the phosphogypsum lightweight aggregate in water for 8 hours to pre-wet it and obtain pre-wetted aggregate;

[0143] A2: Mix the pre-wetted aggregate from step A1 with cement, silica fume, fly ash, and elastic asphalt sand for 3 minutes, then add water and water-reducing agent and mix for 3 minutes, and finally add composite fiber and hooked steel fiber and continue mixing for 3 minutes to obtain the initial cement-based material.

[0144] A3: After molding, vibrating and shaping the initial cement-based material in step A2, cover the surface with an impermeable film for film curing, then remove the mold and place it in a standard curing environment for 28 days to obtain a lightweight and high-ductility cement-based composite material.

[0145] Comparative Example 1

[0146] This comparative example is basically the same as Example 1, except that the elastic asphalt sand is replaced by an equal amount of waste asphalt sand. The preparation method of waste asphalt sand includes the following steps: waste asphalt concrete is screened to obtain waste asphalt sand with a particle size range of 1.18-2.36 mm and an asphalt content of 10%.

[0147] That is, the waste asphalt sand in this comparative example was not modified.

[0148] Comparative Example 2

[0149] This comparative example is basically the same as Example 1, except that the preparation method of the elastic asphalt sand includes the following steps:

[0150] P1. Waste asphalt concrete is screened to obtain waste asphalt sand with a particle size range of 1.18-2.36mm and an asphalt content of 10%.

[0151] P2. Use 100% carbon tetrachloride solution to quickly rinse the surface of the waste asphalt sand in step P1 for 8 minutes at a flow rate of 0.2 mL / s, then dry to obtain elastic waste asphalt sand.

[0152] P3. Prepare two types of silane coupling agents, KH550 and A171, with a total dosage of 1% of the mass of the elastic waste asphalt sand. The mass ratio of the two types of silane coupling agents is 1:1. Then, prepare a mixed solution with a mass ratio of deionized water:silane coupling agent:anhydrous ethanol of 10:50:40. Add the elastic waste asphalt sand from step P2, hydrolyze for 2 hours, filter, and heat to dry to obtain the elastic asphalt sand.

[0153] That is, the elastic asphalt sand in this comparative example was not soaked in microcrystalline paraffin oil.

[0154] Comparative Example 3

[0155] This comparative example is basically the same as Example 1, except that the preparation method of the elastic asphalt sand includes the following steps:

[0156] P1. Waste asphalt concrete is screened to obtain waste asphalt sand with a particle size range of 1.18-2.36mm and an asphalt content of 10%.

[0157] P2. Soak the waste asphalt sand from step P1 in microcrystalline wax oil for 1.5 hours and air dry naturally to obtain elastic waste asphalt sand.

[0158] P3. Prepare two types of silane coupling agents, KH550 and A171, with a total dosage of 1% of the mass of the elastic waste asphalt sand. The mass ratio of the two types of silane coupling agents is 1:1. Then, prepare a mixed solution with a mass ratio of deionized water:silane coupling agent:anhydrous ethanol of 10:50:40. Add the elastic waste asphalt sand from step P2, hydrolyze for 2 hours, filter, and heat to dry to obtain the elastic asphalt sand.

[0159] That is, the elastic asphalt sand in this comparative example was not washed with carbon tetrachloride solution.

[0160] Comparative Example 4

[0161] This comparative example is basically the same as Example 1, except that the preparation method of the elastic asphalt sand includes the following steps:

[0162] P1. Waste asphalt concrete is screened to obtain waste asphalt sand with a particle size range of 1.18-2.36mm and an asphalt content of 10%.

[0163] P2. Use a 100% carbon tetrachloride solution to quickly rinse the surface of the waste asphalt sand from step P1 for 8 minutes at a flow rate of 0.2 mL / s. Dry the sand and then soak it in microcrystalline paraffin oil for 1.5 hours. Allow it to air dry naturally to obtain the elastic asphalt sand.

[0164] That is, the elastic asphalt sand in this comparative example was not treated with silane coupling agent.

[0165] Comparative Example 5

[0166] This comparative example is basically the same as Example 1, except that the phosphogypsum lightweight aggregate is replaced with an equal amount of phosphogypsum lightweight sand. The preparation method of the phosphogypsum lightweight sand includes the following steps:

[0167] S1. Phosphogypsum and sodium hydroxide are mixed at a mass ratio of 100:80 and then granulated using a power scraper disc pelletizer. The pelletizer is tilted at 50° and rotated at 30 r / min to obtain phosphogypsum aggregate with a particle size of 2-4 mm and a density of 875 kg / m³. 3 The cylinder compressive strength is 8.5 MPa;

[0168] S2. The phosphogypsum aggregate from step S1 is crushed by a vertical shaft impact crusher with a rotation speed of 1000 r / min and a feed rate of 50 kg / s. After screening by a screening machine, phosphogypsum lightweight sand is obtained with a particle size of less than 2.36 mm and a fineness modulus of 2.5-2.7.

[0169] That is, the phosphogypsum lightweight sand in this comparative example was not impregnated with polyurethane solution.

[0170] Comparative Example 6

[0171] This comparative example is basically the same as Example 1, except that the microcrystalline wax oil is replaced with an equal amount of heavy crude oil.

[0172] Comparative Example 7

[0173] This comparative example is basically the same as Example 1, except that the phosphogypsum lightweight aggregate is replaced with an equal amount of manufactured sand.

[0174] Test case

[0175] The properties of the high-ductility cement-based composite materials in Examples 1-3 and Comparative Examples 1-2 were tested according to the "Standard for Testing and Evaluation of Concrete Strength" (GB / T50107-2013) and the "Standard for Test Methods of Long-Term Performance and Durability of Ordinary Concrete" (GB / T50082-2009). The test results are shown in Table 1 below.

[0176] Table 1 Performance tests of high-ductility cement-based composite materials in Examples 1-3 and Comparative Examples 1-2

[0177]

[0178] As shown in Table 1, the tensile strength and impact strength of the high-ductility cement-based composite materials in Examples 1-3 are significantly improved compared to Comparative Examples 1-6, while the apparent density and shrinkage rate are significantly improved compared to Comparative Example 7. This indicates that the high-ductility cement-based composite material of the present invention has the advantages of being lightweight, having low shrinkage, and possessing high tensile and impact strength, and can be applied to various large-scale engineering projects. The high-ductility cement-based composite material of the present invention not only improves the toughness of concrete itself, but also provides new ideas for the curing of phosphogypsum and the modification of waste asphalt sand, thus having significant economic and environmental benefits.

[0179] Compared with Example 1, the cement-based material of Example 1 showed significantly better performance in all aspects. This may be because the treatment of waste asphalt sand with heavy crude oil (macromolecule industrial oil) does not make the waste asphalt sand softer or more elastic, resulting in poor performance of the cement-based material.

[0180] Comparing Comparative Examples 1-6 with Example 1, it can be seen that changing the treatment method of waste asphalt sand or phosphogypsum does not yield the high ductility cement-based composite material of the present invention. This indicates that waste asphalt sand and phosphogypsum treated by the method of the present invention, when used as aggregates for cement-based materials, can effectively improve the tensile strength and impact resistance of the high ductility cement-based composite material.

[0181] The above detailed embodiments describe the implementation of the present invention; however, the present invention is not limited to the specific details described in the above embodiments. Within the scope of the claims and technical concept of the present invention, various simple modifications and changes can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

Claims

1. A phosphogypsum lightweight high-ductility cement-based composite material, characterized by, The raw materials include the following parts by weight: 450-600 parts cement, 150-300 parts fly ash, 100-300 parts silica fume, 400-500 parts phosphogypsum lightweight aggregate, 200-300 parts elastic asphalt sand, 12-18 parts composite fiber, 60-90 parts steel fiber, 20-30 parts water-reducing agent, and 170-200 parts water. The method for preparing the elastic asphalt sand includes the following steps: Waste asphalt concrete is crushed and screened to obtain waste asphalt sand; The waste asphalt sand is washed with organic solvent, dried, then soaked in industrial oil and dried to obtain elastic waste asphalt sand; The elastic waste asphalt sand is immersed in a silane coupling agent solution, filtered, and dried to obtain the elastic asphalt sand. The method for preparing the phosphogypsum lightweight aggregate includes the following steps: Phosphogypsum and alkali activator are ground, mixed, granulated, crushed and sieved to obtain phosphogypsum lightweight sand. The phosphogypsum lightweight sand is impregnated in a polymer solution and dried to obtain the phosphogypsum lightweight aggregate. The polymer solution includes at least one of polyurethane solution, sodium polyacrylate solution, and polyvinyl alcohol solution.

2. The phosphogypsum lightweight high ductility cement-based composite material according to claim 1, characterized in that, The organic solvent includes at least one of carbon tetrachloride, tetrahydrofuran, and acetone.

3. The phosphogypsum lightweight high-ductility cement-based composite material according to claim 1, characterized in that, The industrial oil includes at least one of microcrystalline wax oil, white oil, and light lubricating oil.

4. The phosphogypsum lightweight high-ductility cement-based composite material according to claim 1, characterized in that, The dosage of the silane coupling agent is 1-2% of the mass of the elastic waste asphalt sand.

5. The phosphogypsum lightweight high-ductility cement-based composite material according to claim 1, characterized in that, The mass ratio of the phosphogypsum to the alkali activator is 10:(8-12).

6. The phosphogypsum lightweight high-ductility cement-based composite material according to claim 1, characterized in that, The soaking time is 0.5-2 hours.

7. The phosphogypsum lightweight high-ductility cement-based composite material according to claim 1, characterized in that, The composite fiber comprises polyethylene fiber, polyvinyl alcohol fiber and polyester fiber in a mass ratio of 10:(9-11):(8-12).

8. The method for preparing the phosphogypsum lightweight high-ductility cement-based composite material according to any one of claims 1-7, characterized in that, Includes the following steps: The lightweight aggregate of phosphogypsum pre-wetted with water is mixed with other raw materials of the lightweight high-ductility cement-based composite material.

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