Method for preparing steel slag aggregate with volume coupling stability and excellent road performance

Abstract

The application discloses a preparation method of steel slag aggregate with volume coupling stability and excellent road performance, and solves the problems of volume expansion, poor water damage resistance and poor economy of the steel slag as aggregate in the road engineering application process. The application performs surface modification on the steel slag by a high polymer material, seals the porous structure on the surface of the steel slag, performs acid-base coupling stability on the active components such as calcium oxide of the steel slag, and simultaneously reduces the water absorption and oil-stone ratio of the steel slag aggregate. The steel slag aggregate prepared by the application is used in asphalt mixture, is superior to the asphalt mixture prepared by the ordinary steel slag aggregate, and can meet the road specification requirements. The application can solve the problems of the ordinary steel slag aggregate, such as easy expansion when meeting water and the decrease of the water damage resistance after being added into the asphalt mixture.

Description

Technical Field

[0001] This invention belongs to the field of road materials and relates to a steel slag aggregate, specifically a method for preparing steel slag aggregate with stable volume coupling and excellent road performance. Background Technology

[0002] Steel slag, a waste product generated during the steelmaking process, is a typical urban industrial solid waste. How to comprehensively utilize steel slag has always been an important issue of concern to enterprises and society. Steel slag has a rich array of angular surfaces, possessing strong interlocking force and good internal friction embedding force, making it an excellent road material. Steel slag-mixed asphalt has good pavement load-bearing capacity, and its high bulk density and polishing value provide good anti-skid performance, ensuring comfortable and safe driving. However, steel slag contains active components such as free calcium oxide (f-CaO) and free magnesium oxide (f-MgO), which easily undergo hydration reactions and expand. This volume expansion generates expansion stress, easily leading to internal cracking of the asphalt mixture, resulting in asphalt pavement defects such as rutting and cracking, which is the primary reason limiting its large-scale application. Steel slag has a rich porous structure, preventing it from being fully coated with asphalt, resulting in poor adhesion. Furthermore, its high water absorption rate increases the asphalt-aggregate ratio of the asphalt mixture, reducing the economic efficiency of steel slag asphalt mixtures. When steel slag aggregate is exposed during use, adverse phenomena such as red discoloration of the road surface due to oxidation of the steel slag occur.

[0003] Patent CN113578914A proposes an integrated physicochemical reaction-based method for strengthening the treatment of steel slag, involving two washings and drying of the steel slag. Patent CN116023055A discloses a method for improving the volume stability of steel slag and preparing carbon-sequestrated lightweight aggregates using CO2 under ammonia-mediated modification. Both patents can produce volume-stable steel slag, but they generate secondary pollution such as wastewater, increasing treatment costs. Patent CN113563692A discloses a modifier for improving the stability of steel slag aggregates and its preparation method, which can coat the surface of steel slag with a micron-level thin film that is dense and uniform. The resulting modified steel slag has low water absorption and good volume stability, but this method is costly. Therefore, there is an urgent need to modify steel slag to promote the high-value application of bulk industrial solid waste in road engineering. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a method for preparing steel slag aggregate with stable volume coupling and excellent road performance, so as to overcome the shortcomings of the prior art.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0006] A method for preparing steel slag aggregate with stable volume coupling and excellent road performance is provided, comprising the following steps:

[0007] a. A high melt flow index polymer material, microcrystalline wax, aromatic oil, coupling agent, stearic acid, and calcium powder are mixed in a premixer for a certain period of time in a certain mass ratio, and then reacted in a twin-screw extruder under suitable conditions to obtain a fast-dissolving functional modifier.

[0008] b. Heat ordinary steel slag aggregate in a mixing pot to a certain temperature, then add a certain amount of functional modifier, and mix at that temperature for a suitable time to obtain steel slag aggregate.

[0009] The steel slag aggregate preparation method described above, which features stable volume coupling and excellent road performance, includes high melt flow index polymer materials such as linear low-density polyethylene (LLDPE), ethylene-vinyl acetate copolymer (EVA), and polystyrene (PS) polymers, all with melt flow indices greater than 5 g / 10 min.

[0010] The method for preparing steel slag aggregate with stable volume coupling and excellent road performance, as described above, wherein the coupling agent is one or more of 3-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, and γ-methacryloyloxypropyltrimethoxysilane.

[0011] As described in the method for preparing steel slag aggregate with stable volume coupling and excellent road performance, the mass ratio of the fast-dissolving functional modifier is as follows: LLDPE 0-50, EVA 10-35, PS 10-15, microcrystalline wax 50-70, aromatic oil 10-30, 3-aminopropyltriethoxysilane 0-8, γ-glycidyl etheroxypropyltrimethoxysilane 0-8, γ-methacryloyloxypropyltrimethoxysilane 0-8, stearic acid 2-5, and calcium powder 3-15.

[0012] As described in the method for preparing steel slag aggregate with stable volume coupling and excellent road performance, the high melt index polymer material, microcrystalline wax, aromatic oil, stearic acid, and calcium powder are mixed in a premixer for 10-20 minutes, and the twin-screw extruder temperature is set to 150-230℃ and the speed is 300-450 rpm.

[0013] As described in the method for preparing steel slag aggregate with stable volume coupling and excellent road performance, the mass ratio of ordinary steel slag aggregate to fast-dissolving functional modifier is 100:(0.5-3).

[0014] As described in the method for preparing steel slag aggregate with stable volume coupling and excellent road performance, ordinary steel slag aggregate is heated to a target temperature of 160-200℃ in a mixing pot, and mixed with an instant functional modifier for 20-50s at a mixing speed of 50-80rpm to obtain steel slag aggregate.

[0015] The beneficial effects of the technical solution of this invention are:

[0016] This invention addresses the challenges of excessive volume expansion and poor road performance of steel slag through surface modification, resulting in steel slag aggregate with stable volume coupling and excellent road performance. Specifically, a fast-dissolving functional modifier is prepared in a twin-screw extruder and then mixed with ordinary steel slag. This process seals the porous structure of the steel slag surface, reducing the water absorption and asphalt-aggregate ratio of the steel slag aggregate. Simultaneously, it improves the adhesion between the steel slag and asphalt materials. The steel slag aggregate prepared by this invention, when used in asphalt mixtures, outperforms asphalt mixtures made from ordinary steel slag aggregates and meets road performance specifications.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] 1. The fast-dissolving functional modifier can surface modify steel slag, seal the porous structure of the steel slag surface, stabilize the active components of steel slag such as calcium oxide through acid-base coupling, reduce the water absorption rate and oil-stone ratio of steel slag aggregate, and solve the problems of easy volume expansion and economic application of ordinary steel slag.

[0019] 2. Compared with the method of neutralizing steel slag with acid and alkali to eliminate active molecules, the method of surface-modified steel slag does not generate secondary wastewater pollution, while improving the adhesion between steel slag and asphalt and improving the road performance of steel slag.

[0020] In summary, this invention has significant performance improvement effects and good economic benefits, and can promote the high-value-added application of steel slag aggregate in road engineering. Detailed Implementation

[0021] The terms “invention” and “the present invention” used in this specification are intended to broadly refer to all subject matter of this specification and any of the following patent claims. Statements containing these terms should not be construed as limiting the subject matter described herein or limiting the meaning or scope of any of the following patent claims. Furthermore, this specification does not attempt to describe or limit the subject matter covered by any specific part, paragraph, statement, or claim of this application. The subject matter should be understood with reference to the entire specification and any of the following claims. The invention may have other embodiments and be practiced or implemented in other ways. Moreover, it should be understood that the wording and terminology used herein are for illustrative purposes and should not be considered limiting. The use of “comprising,” “having,” and “including,” and variations thereof herein, means to include the items listed herein and their equivalents and additional items.

[0022] This invention provides a method for preparing steel slag aggregate with stable volume coupling and excellent road performance, comprising the following steps:

[0023] a. A high melt flow index polymer material, microcrystalline wax, aromatic oil, coupling agent, stearic acid, and calcium powder are mixed in a premixer for a certain period of time in a certain mass ratio, and then reacted in a twin-screw extruder under suitable conditions to obtain a fast-dissolving functional modifier.

[0024] b. Heat ordinary steel slag aggregate in a mixing pot to a certain temperature, then add a certain amount of functional modifier, and mix at that temperature for a suitable time to obtain steel slag aggregate.

[0025] In a preferred embodiment, the high melt flow index polymeric material includes linear low-density polyethylene (LLDPE), ethylene-vinyl acetate copolymer (EVA), and polystyrene (PS) polymeric materials, all with a melt flow index greater than 5 g / 10 min. The coupling agent is one or more of 3-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, and γ-methacryloyloxypropyltrimethoxysilane.

[0026] The mass ratio of the fast-dissolving functional modifier is as follows: LLDPE 0-50, EVA 10-35, PS 10-15, microcrystalline wax 50-70, aromatic oil 10-30, 3-aminopropyltriethoxysilane 0-8, γ-glycidyl etheroxypropyltrimethoxysilane 0-8, γ-methacryloyloxypropyltrimethoxysilane 0-8, stearic acid 2-5, and calcium powder 3-15.

[0027] High melt flow index polymers, microcrystalline wax, aromatic oil, stearic acid, and calcium powder are mixed in a premixer for 10-20 minutes. The twin-screw extruder temperature is set to 150-230℃, and the speed is 300-450 rpm. The mass ratio of ordinary steel slag aggregate to readily soluble functional modifier is 100:(0.5-3). The ordinary steel slag aggregate is heated in a mixing pot to a target temperature of 160-200℃, and mixed with the readily soluble functional modifier for 20-50 seconds at a mixing speed of 50-80 rpm to obtain steel slag aggregate.

[0028] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0029] Example 1

[0030] (1) Mix 500g of LLDPE, 350g of EVA, 150g of PS, 50g of microcrystalline wax, 30g of aromatic oil, 50g of 3-aminopropyltriethoxysilane, 3g of stearic acid, and 30g of calcium powder in a premixer for 15min, and then react in a twin-screw extruder at 190℃ and 450rpm for 15min to obtain a fast-dissolving functional modifier.

[0031] (2) Heat 2000g of ordinary steel slag aggregate with a diameter of 5-10mm in a mixing pot to 190℃, then add 50g of functional modifier and carry out the process at this temperature for 45s to obtain steel slag aggregate with stable volume coupling and excellent road performance.

[0032] The prepared steel slag aggregate was tested for water absorption and asphalt adhesion grade. Then, it was used to replace 5-10mm basalt aggregate in SMA-13 ​​asphalt mixture to prepare Marshall specimens, and the volume expansion and road performance of the specimens were tested.

[0033] Example 2

[0034] (1) Mix 350g of LLDPE, 500g of EVA, 150g of PS, 60g of microcrystalline wax, 30g of aromatic oil, 60g of γ-glycidyl etheroxypropyltrimethoxysilane, 5g of stearic acid, and 25g of calcium powder in a premixer for 15min, and then react in a twin-screw extruder at 190℃ and 450rpm for 15min to obtain an instant functional modifier;

[0035] (2) Heat 2000g of ordinary steel slag aggregate with a diameter of 5-10mm in a mixing pot to 190℃, then add 60g of functional modifier and carry out the process at this temperature for 80s to obtain steel slag aggregate with stable volume coupling and excellent road performance.

[0036] The prepared steel slag aggregate was tested for water absorption and asphalt adhesion grade. Then, it was used to replace 5-10mm basalt aggregate in SMA-13 ​​asphalt mixture to prepare Marshall specimens, and the volume expansion and road performance of the specimens were tested.

[0037] Example 3

[0038] (1) Mix 450g of LLDPE, 400g of EVA, 120g of PS, 50g of microcrystalline wax, 30g of aromatic oil, 50g of γ-methacryloyloxypropyltrimethoxysilane, 2g of stearic acid, and 20g of calcium powder in a premixer for 15min, and then react in a twin-screw extruder at 150℃ and 450rpm for 20min to obtain a fast-dissolving functional modifier.

[0039] (2) Heat 2000g of ordinary steel slag aggregate with a diameter of 5-10mm in a mixing pot to 160℃, then add 40g of functional modifier and carry out the process at this temperature for 45s to obtain steel slag aggregate with stable volume coupling and excellent road performance.

[0040] The prepared steel slag aggregate was tested for water absorption and asphalt adhesion grade. Then, it was used to replace 5-10mm basalt aggregate in SMA-13 ​​asphalt mixture to prepare Marshall specimens, and the volume expansion and road performance of the specimens were tested.

[0041] Comparative Example 1

[0042] Untreated ordinary steel slag aggregate was tested for water absorption and asphalt adhesion grade. Then, Marshall specimens were prepared by replacing 5-10mm basalt aggregate in SMA-13 ​​asphalt mixture, and the volume expansion and road performance of the specimens were tested.

[0043] As shown in Table 1, compared to Comparative Example 1, the water absorption rate of the surface-modified steel slag in Examples 1-3 was reduced to below 50% of the ordinary level, and the adhesion grade with asphalt was improved by one grade. These results indicate that fast-dissolving functional modifiers with different formulations can effectively seal the porous structure of the steel slag surface, reduce the water absorption rate of the steel slag aggregate, and improve the adhesion between steel slag and asphalt materials.

[0044] Table 1. Performance indicators of steel slag from different embodiments

[0045]

[0046] Table 2. Performance Indicators of Steel Slag Asphalt Mixtures from Different Examples

[0047]

[0048] As shown in Table 2, tests on steel slag asphalt mixtures from different examples demonstrate that the asphalt-aggregate ratio of surface-modified steel slag asphalt mixtures is reduced, improving their economic efficiency. The surface-modified steel slag asphalt mixtures also exhibit improved residual stability and freeze-thaw splitting strength ratio. Furthermore, surface-modified steel slag asphalt mixtures demonstrate good volume stability and excellent road performance.

[0049] The above are merely preferred embodiments of the present invention and are not intended to limit the implementation methods and scope of protection of the present invention. Those skilled in the art should recognize that any equivalent substitutions and obvious changes made using the present invention specification should be included within the scope of protection of the present invention.

Claims

1. A method for preparing steel slag aggregate with stable volume coupling and excellent road performance, characterized in that, Includes the following steps: a. A high melt flow index polymer material, microcrystalline wax, aromatic oil, coupling agent, stearic acid, and calcium powder are mixed in a premixer for a certain period of time in a certain mass ratio, and then reacted in a twin-screw extruder under suitable conditions to obtain a fast-dissolving functional modifier. The high melt flow index polymer material includes linear low-density polyethylene (LLDPE), ethylene-vinyl acetate copolymer (EVA), and polystyrene (PS) polymer materials, all with a melt flow index greater than 5 g / 10 min. The coupling agent is one or more of 3-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, and γ-methacryloyloxypropyltrimethoxysilane. The mass ratio of the fast-dissolving functional modifier is: LLDPE 0-50, EVA... 10-35, PS 10-15, microcrystalline wax 50-70, aromatic oil 10-30, 3-aminopropyltriethoxysilane 0-8, γ-glycidyl etheroxypropyltrimethoxysilane 0-8, γ-methacryloyloxypropyltrimethoxysilane 0-8, stearic acid 2-5, calcium powder 3-15; b. Heat ordinary steel slag aggregate in a mixing pot to a certain temperature, then add a certain amount of functional modifier, and mix at that temperature for a suitable time to obtain steel slag aggregate.

2. The method for preparing steel slag aggregate with stable volume coupling and excellent road performance according to claim 1, characterized in that, The high melt flow index polymer material, microcrystalline wax, aromatic oil, stearic acid, and calcium powder are mixed in a premixer for 10-20 minutes, and the twin-screw extruder temperature is set to 150-230℃ and the speed is 300-450rpm.

3. The method for preparing steel slag aggregate with stable volume coupling and excellent road performance according to claim 1, characterized in that, The mass ratio of ordinary steel slag aggregate to quick-dissolving functional modifier is 100:(0.5-3).

4. The method for preparing steel slag aggregate with stable volume coupling and excellent road performance according to claim 1, characterized in that, Ordinary steel slag aggregate is heated in a mixing pot to a target temperature of 160-200℃, and mixed with an instant functional modifier for 20-50 seconds at a mixing speed of 50-80 rpm to obtain steel slag aggregate.

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