Silicon-calcium-based porous material, preparation method thereof and application of silicon-calcium-based porous material as asphalt fume fixing agent

Abstract

The invention discloses a silicon-calcium-based porous material, a preparation method thereof and application of the silicon-calcium-based porous material as an asphalt smoke fixing agent, the silicon-calcium-based porous material is used for adsorbing asphalt smoke at 25-100 DEG C, and the adsorption capacity of the silicon-calcium-based porous material to the asphalt smoke is 7-18 mg / g. The preparation method of the silicon-calcium-based porous material comprises the following steps: mixing alkali liquor, silica fume and lime emulsion, reacting for 50-150 minutes under the stirring condition of 50-150 DEG C to obtain a first substance, and washing and drying the first substance to obtain the silicon-calcium-based porous material. According to the invention, the silicon-calcium-based porous material which adsorbs the asphalt smoke to be saturated is used as the asphalt smoke fixing agent, and the asphalt smoke fixing agent is used as the admixture to prepare the asphalt concrete, so that permanent fixation of the asphalt smoke is realized, and the purpose of treating waste with waste is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of environmentally friendly materials and road engineering, and in particular relates to a calcium-silicon-based porous material, a preparation method thereof, and use thereof as an asphalt fume fixative. Background Art

[0002] Amid the rapid development of national infrastructure, asphalt concrete has been widely used in transportation construction, including highways and municipal roads, due to its excellent performance. However, this process produces a large amount of asphalt fume, which has a complex composition and contains various toxic and hazardous substances such as toluene and polycyclic aromatic hydrocarbons, posing a serious threat to the environment and human health.

[0003] While various methods currently exist for treating asphalt fume, each has its drawbacks. For example, high-temperature combustion and catalytic combustion methods consume large amounts of energy and have high operating costs; low-temperature plasma and photocatalytic oxidation methods have limited effectiveness and may generate secondary pollution. While fixed-bed activated carbon adsorption can reduce fume emissions, its high cost limits its widespread application. Furthermore, asphalt concrete, as a key material, faces challenges not only in fume treatment during production and processing but also in pavement construction. Asphalt pavements are susceptible to high temperatures, heavy loads, and heavy traffic, leading to rutting, which not only threatens driving safety but also shortens the pavement's service life. Furthermore, water damage from rain, ice, and snow can easily penetrate the pavement, reducing the adhesion between the asphalt and aggregate, causing water damage such as loosening and potholes, which severely weakens the pavement's load-bearing capacity and durability. Asphalt pavements are also susceptible to localized cracking due to low-temperature embrittlement in low-temperature environments. To increase the service life of asphalt pavement, researchers have tried to improve the gradation of the mixture, use high-performance modified asphalt, or add fibers, but further exploration of more effective solutions is still needed. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the present invention aims to provide a method for preparing a calcium-silicon-based porous material, which adopts a one-step dynamic hydrothermal synthesis method.

[0005] Another object of the present invention is to provide a calcium-silicon-based porous material obtained by the above preparation method.

[0006] Another object of the present invention is to provide the use of the above-mentioned silicon-calcium-based porous material as an asphalt fume fixative after it is saturated with asphalt fume.

[0007] Another object of the present invention is to provide a method for fixing asphalt smoke.

[0008] The purpose of the present invention is achieved through the following technical solutions.

[0009] A method for preparing a calcium-silicon-based porous material comprises: mixing an alkali solution, microsilica powder and lime emulsion, reacting the mixture under stirring at 50-150° C. for 50-150 min to obtain a first substance, washing the first substance and drying the mixture to obtain the calcium-silicon-based porous material, wherein the alkali solution is an aqueous solution of alkali, the concentration of the alkali in the alkali solution is 5-15wt%, and the ratio of silicon in the microsilica powder to calcium in the lime emulsion is (0.5-1.6):1, and the ratio of the volume fraction of the alkali solution to the mass fraction of the lime emulsion is 100:(68-92). The unit of the volume fraction is mL, and the unit of the mass fraction is g.

[0010] In the above technical solution, the lime emulsion is obtained by mixing quicklime and water and stirring at 50-100°C for 30-120 minutes, wherein the ratio of quicklime to water used to prepare the lime emulsion is 1:(3-10) by mass.

[0011] In the above technical solution, the lime emulsion is first sieved through a 100-mesh standard sieve before being mixed with the alkali solution and the microsilica powder.

[0012] In the above technical solution, the stirring speed is 100~500 r / min.

[0013] In the above technical solution, the washing adopts water at 20-100°C, and the mass of the water used for washing is 10-50 times the sum of the mass of microsilica powder and quicklime.

[0014] In the above technical solution, the base is sodium hydroxide (NaOH) or potassium hydroxide (KOH).

[0015] The silicon-calcium based porous material obtained by the above preparation method.

[0016] A method for fixing asphalt smoke comprises: allowing the calcium-silicon-based porous material to adsorb asphalt smoke at 25-100° C., wherein the adsorption capacity of the calcium-silicon-based porous material for asphalt smoke (at saturated adsorption) is 7-18 mg / g.

[0017] In the above technical solution, the specific surface area of ​​the calcium silicon-based porous material is 100-220 m 2 / g.

[0018] The above-mentioned silicon-calcium-based porous material is used as an asphalt smoke fixative after being saturated with asphalt smoke.

[0019] An asphalt concrete comprises an asphalt fume fixative, wherein the asphalt fume fixative is a calcium-silicon-based porous material capable of absorbing asphalt fume to saturation.

[0020] In the above technical solution, the content of the asphalt fume fixative in the asphalt concrete is 1-6 vol%.

[0021] In the above technical solution, the maximum flexural tensile strain of the asphalt concrete is 967~1207 με, the flexural stiffness modulus is 0.008~0.0102 MPa, and the 48h stability is 7.26~9.86 KN.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. The present invention uses a calcium-silicon-based porous material that absorbs asphalt fume to saturation as an asphalt fume fixative, and uses the asphalt fume fixative as an admixture to prepare asphalt concrete, thereby achieving permanent fixation of asphalt fume and achieving the purpose of treating waste with waste.

[0024] 2. This invention uses industrial solid waste materials (including silicon-containing microsilica fume and calcium-containing quicklime) to prepare a silica-calcium-based porous material for asphalt fume adsorption. The silica-calcium-based porous material adsorbs the asphalt fume to saturation, forming an asphalt fume fixative. This asphalt fume fixative not only effectively controls asphalt fume but can also be used as an admixture in the preparation of asphalt concrete, improving its low-temperature and water stability. Furthermore, this invention provides a novel, efficient, and environmentally friendly method for asphalt fume control and asphalt concrete production. This method achieves high-value utilization of industrial solid waste, in line with the requirements of a circular economy. It effectively addresses the dual challenges of environmental protection and resource utilization, promoting sustainable development in the road engineering sector. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is the specific surface area of ​​the calcium-silicon-based porous material prepared in Examples 1 to 5;

[0026] Figure 2 a is the X-ray diffraction spectrum of the silicon-calcium based porous materials prepared in Example 3 and Examples 6 to 9, Figure 2 b is the X-ray diffraction spectrum of the silicon-calcium based porous materials prepared in Example 7 and Examples 10 to 13;

[0027] Figure 3 This is the N2 adsorption-desorption curve of the calcium-silicon-based porous material prepared in Example 19;

[0028] Figure 4 The pore size distribution of the calcium-silicon-based porous material prepared in Example 19;

[0029] Figure 5 This is the infrared spectrum of the calcium-silicon-based porous material prepared in Example 19;

[0030] Figure 6 is the microscopic morphology of silicon-calcium based porous materials, among which, Figure 6 a~d are the microscopic morphologies of the silicon-calcium-based porous material prepared in Example 19 at different magnifications;

[0031] Figure 7 a is the removal rate of toluene in Examples 22 to 25, Figure 7 b is the linear relationship between T °C and adsorption capacity in Examples 22 to 25. DETAILED DESCRIPTION

[0032] The technical solution of the present invention is further described below with reference to specific embodiments.

[0033] The raw materials used in the following examples are as follows: Microsilica fume was sourced from Inner Mongolia Junzheng Energy Chemical Co., Ltd. The particle size distribution of the microsilica fume ranged from 0.38 to 75 μm, with a median diameter (D50) of 8.839 μm. 83.76 wt% of the microsilica fume had a particle size distribution between 5 and 45 μm. The specific surface area of ​​the microsilica fume was 16.47 m 2 / g, and the average pore diameter is 15.98 nm.

[0034] Quicklime was sourced from Inner Mongolia Junzheng Energy Chemical Co., Ltd. The quicklime particle size distribution ranged from 0.38 to 75 μm, with a median diameter (D50) of 10.83 μm. 80.50 wt% of the quicklime had a particle size distribution between 5 and 75 μm. The specific surface area of ​​the quicklime was 1.73 m 2 / g, average pore diameter 1.38 nm.

[0035] Sodium hydroxide was purchased from Tianjin Yongsheng Fine Chemical Co., Ltd. (analytical grade).

[0036] Aggregates of 10-20 mm, 5-10 mm, and 3-5 mm are limestone, and aggregates of 0-3 mm are manufactured sand.

[0037] The instrument information in the following examples is as follows: Gas chromatograph: GC-2014C, Shimadzu (China) Co., Ltd.

[0038] In the following examples, a method for preparing lime emulsion includes stirring (digesting) quicklime and distilled water at 80°C and 300 rpm for 60 minutes to obtain a lime emulsion, wherein the ratio of quicklime to distilled water is 1:5 by mass. The lime emulsion is sieved through a 100-mesh standard sieve to remove large particles of impurities before use.

[0039] Examples 1 to 21

[0040] A method for preparing a calcium-silicon-based porous material comprises: adding an alkali solution, microsilica powder, and lime emulsion into a reactor, reacting for B min (at a stirring speed of Cr / min) under stirring conditions at A°C to obtain a first substance, filtering the first substance with 80°C water (i.e., washing, the mass of the water used for filtration being 20 times the sum of the masses of the microsilica powder and quicklime), and drying in a 105°C oven for 120 min to obtain the calcium-silica-based porous material, wherein, in terms of the amount of the substances, the ratio of silicon in the microsilica powder to calcium in the lime emulsion (i.e., the silicon-calcium molar ratio) is X, the ratio of the volume fraction of the alkali solution to the mass fraction of the lime emulsion is Y, the unit of the volume fraction is mL, and the unit of the mass fraction is g.

[0041] The alkali solution is a sodium hydroxide (NaOH) aqueous solution, and the concentration of NaOH in the sodium hydroxide aqueous solution is D wt %. A, B, C, D, X, and Y are shown in Table 1.

[0042] Table 1

[0043] The specific surface areas of the calcium-silicon-based porous materials prepared in Examples 1 to 21 are shown in Table 2.

[0044] Table 2

[0045] Figure 1 is the specific surface area of ​​the calcium silicon-based porous material prepared in Examples 1 to 5. Figure 1 As can be seen from Table 2, based on the multi-factor collaborative optimization experiment, the optimal process parameters for the hydrothermal synthesis of calcium-silicon-based porous materials are determined as follows: silicon-calcium molar ratio of 1.4:1, stirring time of 80 min, stirring temperature of 90 °C, alkali concentration in the alkali solution of 11wt%, and stirring speed of 300 r / min. At this time, the specific surface area of ​​the calcium-silicon-based porous material reaches 217 m² / g.

[0046] Figure 2 a is the X-ray diffraction spectrum of the silicon-calcium based porous materials prepared in Example 3 and Examples 6 to 9, Figure 2 b is the X-ray diffraction spectrum of the silicon-calcium based porous materials prepared in Example 7 and Examples 10 to 13; Figure 2 The a shows that in Examples 7, 8, 3, and 9, as the reaction time increases, the diffraction peak near 29° becomes sharper and narrower, and the product crystallinity increases, resulting in a decrease in specific surface area. Specifically, mullite and xonotlite appear in the X-ray diffraction spectra of Examples 8, 3, and 9. Although the X-ray diffraction spectrum of Example 6 lacks characteristic peaks of calcium hydroxide (i.e., no residual calcium hydroxide), the CSH gel does not form clusters or pore structures, resulting in a low specific surface area for the silicon-calcium-based porous material prepared in Example 6. Figure 2 Figure b shows that in Example 10, the dissolution rate of microsilica fume is low, and unreacted calcium hydroxide remains, filling or coating the CSH gel, resulting in a low specific surface area. In Examples 11, 7, 12, and 13, as the temperature increases, the reaction accelerates, the CSH content in the product decreases, mullite and xonotlite increase, and the crystallinity increases, causing the product to transition from amorphous to crystalline, further reducing the specific surface area. This is consistent with the data in Table 2. At the same time, impurities and crystal factors cause some weak peaks to be missing or offset.

[0047] Figure 3 This is the N2 adsorption-desorption curve of the calcium-silicon-based porous material prepared in Example 19. Figure 4 The pore size distribution of the calcium silicon-based porous material prepared in Example 19 is: Figure 5 This is the infrared spectrum of the calcium-silicon-based porous material prepared in Example 19. Figure 3~Figure 4 It can be seen that the silicon-calcium based porous material prepared in Example 19 has a meso-micro dual-pore structure, and its N2 adsorption-desorption curve has type IV and H3 hysteresis loops, confirming that the silicon-calcium based porous material is formed by the accumulation of flaky particles to form slit pores (mesopores of 3-10 nm, main peak of 3.6037 nm) and micropores of 0.6-0.9 nm (main peak of 0.70 nm), with a specific surface area of ​​217 m² / g (mesopore volume of 0.689 mL / g, micropore volume of 0.087 mL / g). The silicon-calcium based porous material prepared in Example 19 forms a three-dimensional network porous structure. Figure 5 The infrared spectrum analysis showed that the silicon-calcium based porous material prepared in Example 19 contained Si-OH bonds (3452 cm -1 )、SiO3 2- (981cm -1 ) and CO3 2- (1489 cm -1 ) active sites, and adsorbed water (3300-3500 cm -1 ) and crystal water (1653cm -1 The synergistic effect of the multi-level pores and surface functional groups of the calcium silicate-based porous material enables it to have a high asphalt fume adsorption capacity. The slit pore structure can effectively capture large molecular volatiles, while the micropores enhance the adsorption stability of small molecules.

[0048] Figure 6 is the microscopic morphology of silicon-calcium based porous materials, among which, Figure 6 a~d are the microscopic morphologies of the silicon-calcium-based porous material prepared in Example 19 at 1k, 5k, 10k and 30k respectively. Figure 6 a and Figure 6 b shows a three-dimensional honeycomb multi-level pore structure, with a loosely interwoven nanosheet network on the surface; Figure 6 c and Figure 6 The d further confirms that its pores are composed of wedge-shaped slits formed by the accumulation of semi-curled layered particles, with disordered interconnected mesopores and micropores within. This multi-scale pore structure synergistically endows the material with excellent adsorption properties: the honeycomb surface rapidly captures asphalt smoke molecules, while the interlayer wedge-shaped pores enhance the fixation stability of organic volatiles through capillary action.

[0049] Examples 22 to 25

[0050] The adsorption performance of calcium-silicon-based porous materials was evaluated using an adsorption evaluation system. The system consists of a toluene saturated vapor generator, a mass flow controller, a gas mixer, a fixed-bed adsorption reactor, and a gas chromatography online detection device. The gas inlet of the gas mixer is connected to the mass flow controller via a pipeline, and the gas outlet of the gas mixer is connected to the gas inlet of the fixed-bed adsorption reactor via a pipeline. The gas chromatography online detection device is connected to the gas outlet of the fixed-bed adsorption reactor via a pipeline to monitor the concentration of the gas flowing out of the fixed-bed adsorption reactor in real time. The mass flow controller controls the flow rates of toluene vapor, oxygen, and carrier gas (nitrogen) to simulate asphalt flue gas.

[0051] The toluene vapor flow rate, oxygen flow rate, and carrier gas (nitrogen) flow rate in the toluene saturation vapor generator were regulated by mass flow controllers. The oxygen, nitrogen, and toluene vapors were then introduced into a gas mixer. When the toluene concentration at the outlet of the gas mixer reached 100 mg / m³ and the oxygen content reached 15% and stabilized, the valve at the gas inlet of the fixed-bed adsorption reactor was opened, and the mixed gas in the gas mixer was controlled to pass through the fixed-bed adsorption reactor at a rate of 150 mL / min. The fixed-bed adsorption reactor was loaded with 0.1 g of adsorbent. The temperature (adsorption temperature) of the fixed-bed adsorption reactor was controlled to T°C by an external heating device. The mixed gas entered the fixed-bed adsorption reactor and fully contacted the adsorbent, causing a dynamic adsorption reaction. When the toluene characteristic peak area detected by gas chromatography stabilized (the gas chromatography results showed that the fluctuation range of the toluene characteristic peak area for three consecutive measurements was less than 5%), the adsorption was determined to be saturated, and the mixture was purged with nitrogen to complete the adsorption performance evaluation. T°C = one of 25°C, 50°C, 75°C, and 100°C. The adsorbent was the calcium-silicon-based porous material prepared in Example 19.

[0052] The above adsorption performance evaluation was conducted under the conditions of 15% oxygen content and 100 mg / m 3The adsorption capacity of the calcium-silicon-based porous material at saturated adsorption of simulated asphalt fume is Q mg / g (the calcium-silicon-based porous material acts as an asphalt fume fixative when adsorbing asphalt fume to saturation). The adsorption capacity, Q, is calculated as: Q = (mass of the calcium-silicon-based porous material at saturated adsorption - mass of the calcium-silicon-based porous material without adsorption) / mass of the calcium-silicon-based porous material without adsorption. The adsorption capacity at T°C is shown in Table 3.

[0053] Table 3

[0054] At T ° C, the toluene concentration detected in the gas outflow from the fixed bed adsorption reactor was measured every 5 min by (C t / C0)*100% to calculate the removal rate, where C0 is the toluene concentration at the outlet of the gas mixer (100 mg / m³), C t The toluene concentration detected in the outlet gas of the fixed bed adsorption reactor at different times. The removal rate from the 5th minute to the 160th minute is as follows: Figure 7 As shown in a, Figure 7 It can be seen from a that there are obvious differences in the removal rate of toluene by the adsorbent at different adsorption temperatures. The adsorption capacity of the adsorbent for toluene at adsorption temperatures of 25°C, 50°C, 75°C, and 100°C are 17.18 mg / g, 12.84 mg / g, 10.85 mg / g, and 7.76 mg / g, respectively. Figure 7 b is the linear relationship between T ° C and adsorption capacity. Figure 7 Figure b shows that the adsorption capacity shows a significant decline as the adsorption temperature increases from 25°C to 100°C. There is a significant negative correlation between adsorption temperature and adsorption capacity (R² = 0.9789), indicating that the adsorption process is thermodynamically controlled. Increased temperature leads to a dual inhibitory effect, resulting in decreased adsorption site activity and increased molecular kinetic energy.

[0055] Examples 26-28

[0056] Asphalt concrete was prepared using an asphalt fume fixative as an admixture. The preparation of the asphalt concrete was carried out in accordance with the "Testing Procedures for Aggregates in Highway Engineering (JTG E42-2005)." The asphalt concrete included: 10-20 mm aggregate, 5-10 mm aggregate, 3-5 mm aggregate, 0-3 mm aggregate, and the asphalt fume fixative. The ratio of 10-20 mm aggregate, 5-10 mm aggregate, 3-5 mm aggregate, 0-3 mm aggregate, and the asphalt fume fixative, by volume, was Z. The asphalt fume fixative was prepared in Example 22. The Z value is shown in Table 4.

[0057] Table 4

[0058] The asphalt concrete prepared in Examples 26-28 was subjected to low-temperature stability and water stability tests. Low-temperature stability (testing temperature: -10°C) and water stability (immersion in 60°C water for 48 hours) were conducted in accordance with the "Testing Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20-2011). The results are shown in Table 5. As shown in Table 5, the addition of asphalt fume fixative increased the maximum flexural strain and decreased the flexural modulus, effectively suppressing transverse cracking. Water stability tests showed that at a 4% addition of asphalt fume fixative, the 48-hour stability reached 9.86 kN. This is attributed to the alkaline components in the asphalt fume fixative forming a hydrated cementing product with the asphalt, enhancing the interfacial debonding resistance. Overall, a 4% addition of asphalt fume fixative can simultaneously improve the low-temperature and water stability of asphalt concrete.

[0059] Table 5

[0060] The asphalt concretes prepared in Examples 27 and 28 were subjected to high-temperature stability testing (at 60°C) in accordance with the "Testing Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20-2011). The dynamic stability (dynamic stability as an indicator of high-temperature stability) of the asphalt concrete prepared in Example 27 was 1630 times / mm, and that of the asphalt concrete prepared in Example 28 was 1585 times / mm. The dynamic stability of the asphalt concretes prepared in Examples 27 and 28 exceeded the national standard requirement of 800 times / mm. In summary, asphalt concrete prepared with the addition of an asphalt fume fixative exhibits both high-temperature and low-temperature stability, as well as water stability.

[0061] The present invention achieves effective treatment of asphalt fume and improvement of asphalt concrete performance through high-value utilization of industrial solid waste, providing a new solution for the sustainable development of the asphalt concrete industry.

[0062] The above is an exemplary description of the present invention. It should be noted that, without departing from the core of the present invention, any simple deformation, modification or other equivalent replacement that can be made by other skilled in the art without expending creative labor falls within the scope of protection of the present invention.

Claims

1. A method for preparing a calcium-silicon-based porous material, characterized in that: include: Alkali solution, microsilica powder and lime emulsion are mixed, reacted under stirring conditions at 50-150° C. for 50-150 min to obtain a first substance, and the first substance is washed and dried to obtain a silicon-calcium based porous material, wherein the alkali solution is an aqueous solution of alkali, the concentration of alkali in the alkali solution is 5-15wt%, and the ratio of silicon in the microsilica powder to calcium in the lime emulsion is (0.5-1.6):1 based on the amount of substance, and the ratio of the volume fraction of the alkali solution to the mass fraction of the lime emulsion is 100:(68-92), the unit of the volume fraction is mL, and the unit of the mass fraction is g.

2. The preparation method according to claim 1, characterized in that The base is sodium hydroxide or potassium hydroxide.

3. The preparation method according to claim 1, characterized in that The lime emulsion is obtained by mixing quicklime and water and stirring at 50-100° C. for 30-120 min, wherein the ratio of quicklime to water used in preparing the lime emulsion is 1:(3-10) by mass.

4. The calcium-silicon-based porous material obtained by the preparation method according to any one of claims 1 to 3.

5. A method for fixing asphalt smoke, characterized in that: include: The calcium-silicon-based porous material according to claim 4 is used to adsorb asphalt fume at 25-100° C., and the adsorption capacity of the calcium-silicon-based porous material for asphalt fume is 7-18 mg / g.

6. The asphalt fume fixing method according to claim 5, characterized in that: The specific surface area of ​​the calcium silicate-based porous material is 100-220 m 2 / g.

7. Use of the calcium-silicon-based porous material as claimed in claim 4 as an asphalt fume fixative after saturation with asphalt fume.

8. An asphalt concrete, characterized in that: include: Asphalt fume fixing agent, the asphalt fume fixing agent is the calcium silicon-based porous material according to claim 4 that adsorbs asphalt fume to adsorption saturation.

9. The asphalt concrete according to claim 8, characterized in that The content of asphalt fume fixative in asphalt concrete is 1~6vol%.

10. The asphalt concrete according to claim 8, characterized in that The maximum flexural tensile strain of the asphalt concrete is 967~1207 με, the flexural stiffness modulus is 0.008~0.0102 MPa, and the 48h stability is 7.26~9.86 KN.

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