Iron tailing acid aggregate modified hydraulic asphalt concrete and preparation method thereof

Abstract

The invention discloses iron tailing acidic aggregate modified hydraulic asphalt concrete and a preparation method thereof, and belongs to the technical field of hydraulic engineering materials. The concrete is prepared from 40%-45% of iron tailings, 25%-30% of iron tailing sand, 7%-9% of limestone mineral powder, 4.2%-5.0% of asphalt, 0.2%-0.4% of polyester fibers, 0.4%-0.6% of a paraffin-based warm mixing agent, 0.3%-0.5% of a polyethylene high modulus agent, 5%-8% of waste tire rubber powder, 5%-20% of cement and 0.3%-0.5% of an anti-stripping agent. The preparation method comprises the following steps: pre-mixing the aggregate, shearing and homogenizing the modified asphalt and compositely stirring, and molding at the low temperature of 140-155 DEG C. Iron tailings and waste tire rubber powder are innovatively adopted to replace more than 75% of natural aggregate, and grafted polyethylene three-dimensional network reinforcement and warm mixing technologies are combined, so that the dynamic modulus reaches 7500-7800MPa, the fatigue life exceeds 300,000 times, the elastic recovery rate is 86-89%, and the performance is improved by more than two times compared with that of a traditional material. The forming temperature is reduced by 30 DEG C, energy is saved by 30%, carbon emission is reduced by 40%, the raw material cost is reduced by 30%, the comprehensive performance is superior to the industrial standard, and an efficient solution is provided for water conservancy projects.

Description

Technical Field

[0001] The invention relates to the technical field of water conservancy engineering materials, and in particular to an iron tailings acidic aggregate modified hydraulic asphalt concrete and a preparation method thereof. Background Art

[0002] Hydraulic asphalt concrete boasts excellent plasticity, flexibility, impermeability, and durability, making it ideal for use in the anti-seepage structures of pumped-storage power station reservoirs, such as those developed by Luddington in the United States, Gram in Germany, and Numazumi in Japan. Aggregates serve as the skeleton of hydraulic asphalt concrete. Alkaline aggregates react chemically with acidic asphalt, resulting in good adhesion, while the bond between acidic aggregates and asphalt primarily occurs through physical adsorption. Traditional hydraulic asphalt concrete requires high-temperature heating during production and construction, which not only consumes significant energy but also produces significant amounts of harmful gases, polluting the environment. Furthermore, traditional asphalt concrete also exhibits several performance deficiencies, such as poor high-temperature stability, weak resistance to water damage, and insufficient low-temperature crack resistance.

[0003] Iron tailings are solid waste generated during the iron ore beneficiation process. A type of acidic aggregate, their accumulation not only consumes land resources but also poses a potential environmental pollution risk. Effectively utilizing iron tailings and achieving resource recycling is a key issue currently facing the industry.

[0004] In recent years, warm-mix asphalt concrete technology has gained increasing popularity. By adding warm-mix agents and other methods, asphalt concrete can be mixed and applied at lower temperatures, thereby reducing energy consumption and environmental pollution. Furthermore, the modification of asphalt concrete using industrial waste has become a research hotspot. For example, materials such as scrap tire rubber powder and polyester fiber are widely used in asphalt concrete modification to improve its performance and environmental friendliness.

[0005] However, there is relatively little research on the application of iron tailings and various modifiers in warm mix asphalt concrete. How to rationally utilize iron tailings and combine them with other modifying materials to prepare high-performance, environmentally friendly warm mix composite modified asphalt concrete is the problem to be solved by the present invention. Summary of the Invention

[0006] The present invention addresses the problems of the prior art by providing an iron tailings acidic aggregate modified hydraulic asphalt concrete and a preparation method thereof. To achieve the above-mentioned object, the present invention adopts the following technical solution: the iron tailings acidic aggregate modified hydraulic asphalt concrete comprises the following components by weight: 40%-45% iron tailings, 25%-30% iron tailings sand, 7%-9% limestone powder, 6.0%-7.5% asphalt, 0.2%-0.4% polyester fiber, 0.4%-0.6% paraffin-based warm mix agent, 0.3%-0.5% polyethylene high modulus agent, 5%-8% scrap tire rubber powder, 5-20% cement, and 0.3%-0.5% anti-stripping agent.

[0007] Furthermore, the crushing value of the iron tailings is ≤25%, and the mud content of the iron tailings sand is ≤2.0%.

[0008] Furthermore, the iron tailings are selected from at least one of magnetite, hematite, limonite and siderite iron tailings.

[0009] Furthermore, the iron tailings have a particle size range of 4.75-19 mm, a SiO2 content ≥55wt%, a Fe2O3 content ≥15wt%, an alkali active reaction expansion rate less than 0.10%, a water absorption rate not greater than 2.5%, a needle-like particle content less than 15%, a moisture content of the iron tailings controlled within the range of 0.5-1.2%, and a clay block content not exceeding 0.3%.

[0010] Furthermore, the iron tailings sand is selected from at least one of magnetite, hematite, limonite, and siderite iron tailings sand.

[0011] Furthermore, the iron tailings sand has a particle size range of 0.075-2.36 mm, a SiO2 content ≥50wt%, a Fe2O3 content ≥10wt%, an alkali active reaction expansion rate <0.08%, a sulfate content (as SO3) ≤0.5%, and an apparent density of 2.60-3.00 g / cm 3 , water absorption rate ≤2.0%, moisture content is controlled within the range of 0.5-1.5%, and mud content (particle size <0.075mm) ≤2.0%.

[0012] Furthermore, the limestone ore powder has a CaCO3 content of ≥90wt%, a MgCO3 content of ≤5wt%, an acid-insoluble matter (SiO2+Al2O3) content of ≤3wt%, and a loss on ignition (950°C) of 38-42%.

[0013] Furthermore, the polyester fiber is polyethylene terephthalate fiber.

[0014] Furthermore, the polyester fiber has a monofilament diameter of 10-30 μm, a length of 3-12 mm, an aspect ratio of 100-400, a tensile strength ≥500 MPa, an elongation at break ≤30%, a melting point of ≥250°C, a thermal shrinkage rate ≤2% at an asphalt mixing temperature of 180°C, and a fiber surface roughness (Ra value) of 0.5-1.2 μm.

[0015] Furthermore, the chemical composition of the cement preferably satisfies the following requirements: CaO content ≥ 60 wt%, SiO2 content ≥ 20 wt%, and Al2O3 content ≥ 5 wt%.

[0016] Furthermore, the paraffin-based warm-mix agent is a composite of Fischer-Tropsch wax and microcrystalline wax.

[0017] Furthermore, the mass ratio of the paraffin-based warm-mix agent is Fischer-Tropsch wax: microcrystalline wax = (60-80%): (20-40%), and meets the drop melting point of 85-110°C.

[0018] Furthermore, the mass ratio of the paraffin-based warm mix agent is Fischer-Tropsch wax: microcrystalline wax = 80%:20%, and meets the drop melting point of 85-110°C.

[0019] Furthermore, the drip melting point refers to the temperature at which a substance begins to drip when the temperature rises to a certain level during the heating process. In the present invention, the drip melting point is a key property indicator of a paraffin-based warm mix agent. The higher the drip melting point, the more stable the warm mix agent remains at high temperatures, preventing it from prematurely melting and escaping, thereby better fulfilling its role in lowering the mixing temperature. The drip melting point is controlled between 85-110°C. This drip melting point range ensures that the warm mix agent melts and disperses evenly at the appropriate temperature during the asphalt mixture mixing process, effectively lowering the mixing temperature, reducing energy consumption and carbon emissions, while maintaining material performance.

[0020] Furthermore, the waste tire rubber powder is 20-40 mesh tire crushed material.

[0021] Furthermore, the polyethylene high modulus agent is maleic anhydride grafted modified low-density polyethylene.

[0022] Furthermore, the polyester fibers form a three-dimensional network structure, and the fatigue life is increased by ≥50%.

[0023] Furthermore, the waste tire rubber powder and the iron tailings sand form an elastic skeleton with an elastic recovery rate of ≥85%.

[0024] Furthermore, the preparation method of the maleic anhydride grafted modified low-density polyethylene is: adding low-density polyethylene to a first solvent to dissolve; mixing the dissolved low-density polyethylene with maleic anhydride and an initiator; reacting at 80°C-120°C for 2-5 hours, and after the reaction is completed, drying the solvent to obtain a grafted product; washing the grafted product with an appropriate second solvent, and then drying it.

[0025] Furthermore, the low-density polyethylene (LDPE) has a density of 0.91-0.93 g / cm 3 The polymer material has good flexibility, ductility and chemical stability. In the present invention, low-density polyethylene is selected as the main component of the polyethylene high modulus agent. After being grafted with maleic anhydride, it can form a three-dimensional network structure with asphalt, thereby significantly improving the dynamic modulus and high-temperature stability of asphalt concrete.

[0026] Furthermore, the first solvent is selected from one or more of xylene, benzene, and tetrahydrofuran.

[0027] Furthermore, the second solvent is selected from one or more of acetone, methyl ethyl ketone, and methyl isobutyl ketone.

[0028] Furthermore, the initiator is selected from one or more of dicumyl peroxide, dibenzoyl peroxide, di-tert-butyl peroxyisopropylbenzene, tert-butyl hydroperoxide, and tert-butyl perbenzoate.

[0029] Furthermore, the anti-stripping agent is selected from: γ-aminopropyltriethoxysilane (KH-550) and / or γ-glycidyloxypropyltrimethoxysilane (KH-560).

[0030] A method for preparing iron tailings acidic aggregate modified hydraulic asphalt concrete is as follows:

[0031] The iron tailings are crushed to a particle size of ≤16mm and a crushing value of ≤25%, and the mud content of the iron tailings is controlled to ≤2.0%; the waste tire rubber powder is 20-40 mesh tire crushed material; the polyethylene high modulus agent is the maleic anhydride grafted modified low-density polyethylene compound system;

[0032] Premixed aggregate: Mix the iron tailings, iron tailings sand and limestone powder, heat to 150-160°C, and continue dry mixing for 3-5 minutes;

[0033] Preparation of modified asphalt: heat the asphalt to 160-170° C., add the paraffin-based warm mix agent, the polyethylene-based high modulus agent, and the waste tire rubber powder, and shear and stir at a rate of 800-1000 r / min for 15-20 minutes;

[0034] Composite mixing and shaping: evenly spread the polyester fiber, the anti-stripping agent and the modified asphalt into the premixed aggregate, dry mix for 2-3 minutes, add the cement, wet mix at 140-150° C. for 30-40 seconds, store the finished material at 140-150° C., and press into shape.

[0035] Furthermore, the shear stirring uses colloid to grind the rubber powder particles in the modified asphalt to ≤0.1mm.

[0036] Furthermore, the polyester fibers are short-cut fibers with special-shaped cross-sections at the ends, and the length is ≥3 mm.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] 1. Through the innovative use of iron ore tailings (accounting for 40%-45%) and waste tire rubber powder (accounting for 5%-8%) to replace traditional alkaline aggregates, the comprehensive utilization rate of industrial solid waste reaches more than 75%, effectively reducing land occupation and environmental pollution; at the same time, the use of paraffin-based warm mix agent (0.4%-0.6%) reduces the mixing temperature of asphalt mixture to 140-155℃, which saves more than 30% energy compared with the traditional hot mix process (usually requires 160-180℃), meeting the needs of green and low-carbon transportation development.

[0039] 2. By grafting maleic anhydride to modify low-density polyethylene (0.3%-0.5%), a three-dimensional network structure is formed with asphalt, with a dynamic modulus of 7500-7800MPa, which is more than twice that of traditional hydraulic asphalt concrete (<3200MPa), significantly enhancing high-temperature stability.

[0040] 3. The elastic skeleton material formed by waste tire rubber powder and iron tailings sand has excellent fatigue resistance and a fatigue life of more than 300,000 times (traditional materials <125,000 times).

[0041] 4. The elastic recovery rate reaches 81%-86%, and it still maintains an elastic recovery rate of more than 85% at -10℃, meeting the performance requirements of hydraulic asphalt concrete in cold areas.

[0042] 5. The full-component solution reduces raw material costs by approximately 30%, providing a high-performance material solution for green hydraulic asphalt concrete that is environmentally friendly, economical, and engineering-applicable. DETAILED DESCRIPTION

[0043] The technical solutions of the present invention are described clearly and completely below. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0044] The mass percentage components of the iron tailings acidic aggregate modified hydraulic asphalt concrete: Further, the mass percentage components of the iron tailings include: 40%, 41%, 42%, 43%, 44%, and 45%.

[0045] Furthermore, the mass percentage components of the iron tailings sand include: 25%, 26%, 27%, 28%, 29%, and 30%. Furthermore, the mass percentage components of the limestone ore powder include: 7%, 8%, and 9%.

[0046] Furthermore, the mass percentage components of the asphalt include: 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.7%, 4.8%, 4.9%, and 5.0%.

[0047] Furthermore, the mass percentage components of the polyester fiber include: 0.2%, 0.3%, and 0.4%.

[0048] Furthermore, the mass percentage components of the paraffin-based warm mix agent include: 0.4%, 0.5%, and 0.6%.

[0049] Furthermore, the mass percentage components of the polyethylene high modulus agent include: 0.3%, 0.4%, and 0.5%.

[0050] Furthermore, the mass percentage components of the waste tire rubber powder include: 5%, 6%, 7%, and 8%.

[0051] Furthermore, the mass percentage components of the cement include: 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, and 20%.

[0052] Furthermore, the mass percentage components of the anti-stripping agent include: 0.3%, 0.4%, and 0.5%.

[0053] Example 1

[0054] The raw materials, by mass ratio, of the iron tailings acidic aggregate modified hydraulic asphalt concrete prepared in this example are as follows: 42.5% iron tailings, 27.5% iron tailings sand, 8% limestone powder, 6.6% asphalt, 0.3% polyester fiber, 0.5% paraffin-based warm mix agent (the mass ratio of which is Fischer-Tropsch wax: microcrystalline wax = 80%:20%), 0.4% maleic anhydride grafted modified low-density polyethylene, 7.2% 30-mesh waste tire rubber powder, 7% cement, and 0.3% KH-560.

[0055] The iron tailings are selected from: hematite iron tailings (particle size range is 4.75-16mm); the iron tailings sand is selected from: hematite iron tailings sand (particle size range is 0.075-2.36mm); the polyester fiber is selected from: polyethylene terephthalate fiber (single filament diameter is 10-30μm, length is 5mm, aspect ratio is 100-400); the paraffin-based warm mix agent is Fischer-Tropsch wax: microcrystalline wax = 70%:30% (mass percentage).

[0056] The preparation method of the iron tailings acidic aggregate modified hydraulic asphalt concrete prepared in this embodiment is as follows:

[0057] Pretreatment process: Crushing the iron ore tailings to a particle size of ≤12mm, and filtering the waste tire rubber powder through a 30-mesh sieve. Preparation of maleic anhydride-grafted low-density polyethylene: Dissolving LDPE pellets in xylene at a mass ratio of 1:8, adding 2% maleic anhydride and 0.5% dicumyl peroxide, reacting at 100°C for 3.5 hours, removing the solvent by rotary evaporation, washing three times with acetone, and drying.

[0058] Aggregate premix: dry mix iron ore tailings, iron ore tailings sand and ore powder at 155℃ for 4 minutes;

[0059] Preparation of modified asphalt: paraffin-based warm mix agent, maleic anhydride grafted polyethylene and waste tire rubber powder were added to asphalt heated to 165°C in sequence, sheared and mixed at 900 r / min for 18 minutes, and processed by colloid mill until the rubber powder particle size was ≤0.08 mm;

[0060] Composite mixing: wet mix the modified asphalt, premixed aggregate, cement and KH-560 at 150℃ for 35 seconds;

[0061] Molding: The test piece was pressed at 145℃.

[0062] Example 2

[0063] The raw material mass ratio and preparation method of the iron tailings acidic aggregate modified hydraulic asphalt concrete prepared in this embodiment refer to the preparation method of Example 1. The differences from Example 1 are: the content of waste tire rubber powder is adjusted to 8%, the iron tailings is reduced to 40%, the colloid mill treatment time is extended to 22 minutes, and the wet mixing temperature is increased to 155°C. The rest is the same as the preparation method of Example 1.

[0064] Example 3

[0065] The raw material mass ratio and preparation method of the iron tailings acidic aggregate modified hydraulic asphalt concrete prepared in this embodiment refer to the preparation method of Example 1. The differences from Example 1 are: the paraffin-based warm mix agent is increased to 0.6%, the asphalt is reduced to 6.2%, the aggregate premix temperature is reduced to 150°C, the asphalt heating temperature is 160°C, and the molding temperature is 140°C. The rest is the same as the preparation method of Example 1.

[0066] Comparative Example 1

[0067] The conventional hot-mix hydraulic asphalt concrete prepared in this comparative example has the following raw material ratios and preparation method: by mass percentage: alkaline coarse aggregate 45%, fine aggregate 30%, limestone powder 8%, asphalt 5.2%, cement 9%. No paraffin-based warm mix agent or polymer modifier is used. During preparation, the aggregate is heated to 180°C and dry-mixed for 5 minutes. The asphalt is heated to 180°C, mixed, wet-mixed for 45 seconds, and then formed at 175°C.

[0068] Comparative Example 2

[0069] The raw material mass ratio and preparation method of the iron tailings acidic aggregate modified hydraulic asphalt concrete (without high modulus formulation) prepared in this comparative example adopt the raw material system of Example 1, remove the maleic anhydride grafted modified low-density polyethylene component, and adjust the ratio to: 43% iron tailings, 28% iron tailings sand, 4.6% asphalt, and 6.5% waste tire rubber powder.

[0070] Comparative Example 3

[0071] The raw material mass ratio and preparation method of the iron tailings acidic aggregate modified hydraulic asphalt concrete (unmodified polyethylene type) prepared in this comparative example adopt the ratio of Example 1, but ordinary LDPE (low-density polyethylene) is used instead of the maleic anhydride grafted modified low-density polyethylene.

[0072] Performance testing:

[0073] The dynamic modulus (MPa), fatigue life (10,000 times), elastic recovery rate (%), and molding temperature (°C) of hydraulic asphalt concrete were tested according to JTG E20-2011. The data are shown in Table 1.

[0074] Table 1.

[0075]

[0076] This invention replaces traditional aggregates with industrial solid wastes such as iron ore tailings and scrap tire rubber powder (utilization rate reaches 75%). Combined with maleic anhydride-grafted modified LDPE (0.4%) and a paraffin-based warm-mix agent (0.5%-0.6%), it significantly optimizes material properties. The modified LDPE forms a three-dimensional network with asphalt, boosting the dynamic modulus to 7500-7800 MPa (more than double that of traditional materials) and achieving a fatigue life of over 300,000 cycles. The rubber phase of the scrap tire rubber powder imparts a high elastic recovery rate (86%-89%). Warm-mix technology controls the molding temperature to 140-155°C (30°C lower than traditional processes), while colloid milling ensures uniform dispersion of the rubber powder, balancing energy conservation and construction feasibility.

[0077] The full-component solution reduces CO2 emissions by approximately 40% and costs by 30%, with comprehensive performance exceeding the JTG E20-2011 standard. It maintains an elastic recovery rate exceeding 80% at -30°C, meeting the needs of extremely cold regions. By adjusting the scrap tire rubber content (6.5%-8%) and process parameters (such as premix temperature and asphalt heating temperature), a balance of high modulus, high toughness, and low-temperature workability is achieved, providing a cost-effective solution for hydraulic asphalt concrete panels.

[0078] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. An iron tailings acidic aggregate modified hydraulic asphalt concrete, characterized in that: The components of the iron tailings acidic aggregate modified hydraulic asphalt concrete by mass percentage are: 40%-45% iron tailings, 25%-30% iron tailings sand, 7%-9% limestone powder, 4.2%-5.0% asphalt, 0.2%-0.4% polyester fiber, 0.4%-0.6% paraffin-based warm mix agent, 0.3%-0.5% polyethylene high modulus agent, 5%-8% waste tire rubber powder, 5-20% cement, and 0.3%-0.5% anti-stripping agent.

2. The iron tailings acidic aggregate modified hydraulic asphalt concrete according to claim 1, characterized in that: The waste tire rubber powder is 20-40 mesh waste tire rubber crushed material.

3. The iron tailings acidic aggregate modified hydraulic asphalt concrete according to claim 1, characterized in that: The paraffin-based warm-mix agent is a composite of Fischer-Tropsch wax and microcrystalline wax.

4. The iron tailings acidic aggregate modified hydraulic asphalt concrete according to claim 1, characterized in that: The polyethylene high modulus agent is maleic anhydride grafted modified low-density polyethylene.

5. The iron tailings acidic aggregate modified hydraulic asphalt concrete according to claim 4, characterized in that: The preparation method of the maleic anhydride grafted modified low-density polyethylene is: Add low-density polyethylene to a first solvent to dissolve, and add maleic anhydride and an initiator to mix; The reaction was carried out at 80-120°C for 2-5 hours. After the reaction was completed, the mixture was spin-dried, washed, and dried to obtain a grafted product.

6. The iron tailings acidic aggregate modified hydraulic asphalt concrete according to claim 5, characterized in that: The first solvent is selected from one or more of: xylene, benzene, and tetrahydrofuran; The second solvent is selected from one or more of acetone, methyl ethyl ketone, and methyl isobutyl ketone.

7. The iron tailings acidic aggregate modified hydraulic asphalt concrete according to claim 1, characterized in that: The anti-stripping agent is selected from: γ-aminopropyltriethoxysilane and / or γ-glycidyloxypropyltrimethoxysilane.

8. A method for preparing the iron tailings acidic aggregate modified hydraulic asphalt concrete according to any one of claims 1 to 7, characterized in that: The following steps are involved: Premixed aggregate: Mix the iron tailings, iron tailings sand and limestone powder, heat to 150-160°C, and continue dry mixing for 3-5 minutes; Preparation of modified asphalt: heat the asphalt to 160-170° C., add the paraffin-based warm mix agent, the polyethylene-based high modulus agent, and the waste tire rubber powder, and shear and stir at a rate of 800-1000 r / min for 15-20 minutes; Composite mixing and shaping: evenly spread the polyester fiber, the anti-stripping agent and the modified asphalt into the premixed aggregate, dry mix for 2-3 minutes, add the cement, wet mix at 140-150° C. for 30-40 seconds, and then keep warm and store at 140-150° C. for standby use or press molding.

9. The method for preparing the iron tailings acidic aggregate modified hydraulic asphalt concrete according to claim 8, characterized in that: The shear stirring refines the rubber powder particles in the modified asphalt to ≤0.1 mm.

10. The method for preparing the iron tailings acidic aggregate modified hydraulic asphalt concrete according to claim 8, characterized in that: The polyester fibers are short-cut fibers with a length of ≥3 mm.

Images