CN111875975A

CN111875975A - Modified asphalt and application thereof

Info

Publication number: CN111875975A
Application number: CN202010858703.3A
Authority: CN
Inventors: 梁波; 张宽宽; 石凯; 郑健龙
Original assignee: Changsha University of Science and Technology
Current assignee: Changsha University of Science and Technology
Priority date: 2020-08-24
Filing date: 2020-08-24
Publication date: 2020-11-03

Abstract

The invention discloses modified asphalt and application thereof. The invention utilizes the freeze drying method and aminosilane to modify the nano montmorillonite, and adds the nano montmorillonite serving as a single asphalt modifier into the asphalt, thereby effectively improving the dispersibility and compatibility of the montmorillonite and the asphalt and enhancing the cohesive force of the asphalt. In order to further enhance the adhesion between the asphalt and the acidic aggregate, the amino silane is adopted to modify the surface of the acidic aggregate, so that the surface energy of the aggregate is reduced, and the adhesion between the asphalt and the aggregate is improved. Compared with matrix asphalt and granite aggregate, the adhesion work is improved by 13% and the peeling work is reduced by 23% by adopting a bidirectional modification method of modifying montmorillonite modified asphalt and modified aggregate by single aminosilane. After the asphalt is aged for a short time, the adhesion performance of the asphalt and the aggregate is still obviously improved by adopting a bidirectional modification method, the adhesion work is improved by 8 percent, the stripping work is reduced by 21 percent, and the water damage of the asphalt pavement can be effectively improved.

Description

Modified asphalt and application thereof

Technical Field

The invention relates to the technical field of road engineering, in particular to a method for modifying asphalt, and particularly relates to a method for improving the adhesion performance of an interface between the modified asphalt and aggregate.

Background

In the service process of asphalt pavements, various pavement diseases such as water damage can occur, especially in rainy areas in south China. The water damage of asphalt pavement is mainly caused by the decrease of adhesion between asphalt and aggregate. There are two mechanisms of action by which this reduction occurs: firstly, the cohesion of the asphalt is weakened due to insufficient cohesion of the asphalt or the asphalt is aged under the influence of the environment, so that the asphalt mixture is peeled off from the interior of an asphalt phase; secondly, the adhesion between the asphalt and the aggregate is insufficient. Since the aggregate has a greater interaction with water than with the asphalt, the entry of water molecules reduces the interaction between the asphalt film and the aggregate, causing the asphalt film to peel off from the aggregate surface. Therefore, the improvement of the water damage resistance of the asphalt pavement needs to be based on two aspects of enhancing the cohesion of the asphalt and improving the adhesion between the asphalt and the aggregate, so that the pavement performance of the asphalt mixture is effectively improved.

The method for improving the adhesion performance of asphalt and aggregate comprises two aspects of asphalt modification and aggregate modification. In the aspect of asphalt modification, in order to improve the adhesion between the surface of an asphalt material and aggregates and the cohesion of asphalt, modifiers such as rubbers, resins, thermoplastic rubbers, nano materials and the like are usually added into the asphalt, so that the aging resistance of the asphalt can be effectively improved, and the reduction rate of the cohesion of the asphalt can be alleviated. The adhesion between asphalt and aggregate can be enhanced by adding modifiers such as metal saponificates, surfactants, polymeric anti-stripping agents and nano anti-stripping agents to asphalt (Peng C et al. construction and blending Materials,2018,169: 591-600.). If the proper amount of SCA and titanate coupling agent are mixed and added into the asphalt, the adhesion grade between the asphalt and granite can be improved (Progress in Industrial and Civil engineering,2012,204(5): 4115-4118). However, the method has less application due to the defects of environmental pollution, asphalt performance influence and the like.

In the selection aspect of the aggregate, the acid aggregate mainly comprising granite has compact stone quality, hardness, strong wear resistance and good compression mechanical property, but has poor adhesion with asphalt, so the granite needs to be modified. The modified aggregate such as slaked lime, cement and the like is used in the early stage, so that the adhesion between the asphalt and the aggregate is improved. However, cement, lime, etc. only physically adsorb on the surface of acidic stones, and thus have poor effects over a long period of time (King Shao Jun et al, civil construction and environmental engineering, 2010,32(5): 41-46.). SHRP plans to treat aggregate surfaces with cationic antistripping agents. In addition, the surface of the aggregate is modified by using organic metal salt and silane coupling agent, so that the surface energy of the aggregate can be reduced, and the adhesion between the aggregate and the asphalt is improved.

The nano montmorillonite as additive is one of the effective methods for improving the ageing resistance of asphalt. However, the nano montmorillonite is a hydrophilic material and has poor compatibility with asphalt. The freeze drying technology is a novel simple montmorillonite layer expanding method, and can increase the interlayer spacing of nano montmorillonite. The invention firstly utilizes the freeze drying technology to increase the interlayer spacing of the montmorillonite, and then uses the method of modifying the montmorillonite by using aminosilane, thereby effectively increasing the interlayer spacing of the montmorillonite and improving the surface modification capability of the montmorillonite by using aminosilane. The modified montmorillonite prepared by the method is used as a single asphalt modifier and added into asphalt, and can improve the compatibility with the asphalt, increase the cohesion of the asphalt and improve the adhesion between the asphalt and aggregate without adding other modifiers. In order to further enhance the adhesion between asphalt and the acidic aggregate, the amino silane is adopted to modify the surface of the acidic aggregate, so that the surface energy of the aggregate is reduced, the interaction between the acidic aggregate and the asphalt is enhanced, and the adhesion between the asphalt and the aggregate is effectively improved. The modified asphalt is prepared by freeze drying and amino silane secondary modification of nano montmorillonite, and meanwhile, the amino silane modification is adopted to simultaneously modify asphalt and aggregate so as to improve the adhesion property of the aged asphalt and the aggregate.

Disclosure of Invention

The invention aims to provide a method for modifying asphalt, which comprises the steps of utilizing a freeze-drying technology to layer NMMT, and then adopting aminosilane to modify freeze-dried NMMT to obtain NH₂-MMT, in NH₂-MMT is a single asphalt modifier to prepare modified asphalt.

The invention also aims to provide a method for improving the interface adhesion performance of the modified asphalt and the aggregate, which adopts a method for simultaneously modifying the asphalt and the aggregate to improve the adhesion performance between the asphalt and the aggregate, improve the water stability of the asphalt mixture and prolong the service life of the asphalt pavement.

In order to achieve the purpose, the technical scheme of the invention is as follows:

the modified asphalt is prepared by adding an asphalt modifier into common asphalt.

The preparation method of the asphalt modifier comprises the following steps:

(1) uniformly dispersing montmorillonite in ultrapure water to obtain a suspension; pre-freezing the suspension and drying to obtain freeze-dried montmorillonite;

(2) dispersing the freeze-dried montmorillonite in water, and adjusting the pH value to 4-4.5 to obtain a suspension; and adding aminosilane into the suspension, uniformly stirring at 60-100 ℃, centrifuging, uniformly dispersing the precipitate in ultrapure water, freeze-drying, grinding and sieving to obtain the asphalt modifier.

Preferably, the concentration of the suspension in the step S1 is 0.006g/ml-0.014 g/ml.

More preferably, the concentration of the suspension is 0.010 g/ml.

Montmorillonite is dispersed in ultrapure water to obtain a suspension with low concentration, so as to fully destroy montmorillonite in a dispersion medium.

Common tap water usually contains five impuritiesElectrolyte 1. electrolyte: comprising charged particles, a common cation being H⁺、Na⁺、K⁺、NH₄ ⁺、Mg²⁺、Ca²⁺、Fe³⁺、Cu²⁺、Mn²⁺、Al³⁺Etc.; the anion having F^-、Cl^-、NO₃ ^-、HCO₃ ^-、SO₄ ^2-、PO₄ ^3-、H₂PO₄ ^-、HSiO₃ ^-Etc.; 2. an organic substance; 3. (ii) particulate matter; 4. a microorganism; 5. a dissolved gas comprising: n is a radical of₂、O₂、Cl₂、H₂S、CO、CO₂、CH₄And the like. Wherein, some ions in the common water can generate ion exchange reaction with the montmorillonite layer, which affects the preparation. And organic species in ordinary water may react with aminosilane. Therefore, only ultrapure water can be used in the present invention.

The ultrapure water is used for removing conductive media, undissociated colloid substances and organic matters in water, and the influence of the modified montmorillonite in the preparation process is reduced.

Preferably, the uniform dispersion is mechanical stirring dispersion, and the dispersion rotation speed is 300-800 rpm.

Preferably, the pre-freezing temperature is-15 ℃ to-25 ℃ and the pre-freezing time is 4h to 10h, more preferably, the pre-freezing temperature is-20 ℃ and the pre-freezing time is 6h, and the montmorillonite suspension is fully frozen at the pre-freezing temperature.

Preferably, the drying is vacuum freeze drying.

Preferably, the pH is adjusted to 4 using dilute hydrochloric acid solution.

Under the acidic environment, acidic protons help the silane reagent to form silanol groups (-Si-OH), and catalyze the condensation reaction of the silanol groups and hydroxyl groups on the silicate layer, so that the modification of the silane coupling agent on the montmorillonite is accelerated. Especially, the catalysis effect is most obvious when the pH is about 4.

Preferably, the aminosilane has the general formula: Y-R-Si-X, wherein Y is amino, R is a C3-C8 carbon chain, Si is a Si atom, X is methoxy or ethoxy, and the aminosilane is one or more of KH550, KH540, KH792 or KH 602.

Further preferably, the aminosilane is KH550, and compared with other aminosilanes, KH550 has triethoxy which can enable-OH reaction on the surface of montmorillonite or aggregate to be more sufficient, and compared with methoxy, the hydrolysis speed is slow, the crosslinking reaction is more sufficient, and modification of the surface of a substance can be controlled.

Amino silane: the mass ratio of the montmorillonite is (1-12) to 10, and preferably, the mass ratio of the amino silane: the mass ratio of the montmorillonite is 4: 10.

Preferably, the stirring in step S2 can be performed in a water bath or oil bath environment, the temperature is 80 ℃, and the stirring is performed for 4 hours in the water bath or oil bath environment.

The freeze-drying in the step S2 can effectively increase the surface area of the modified montmorillonite, and the montmorillonite is more fully contacted with the asphalt.

Preferably, the precipitate is washed for a plurality of times after centrifugation, and the used detergent is a mixed solution of absolute ethyl alcohol and ultrapure water, wherein the volume ratio of the absolute ethyl alcohol to the ultrapure water is 1: 1.

Preferably, the addition amount of the asphalt modifier in the asphalt is 2 to 5 percent by weight.

The invention also provides a method for improving the adhesive property of the interface between the modified asphalt and the aggregate by using the modified asphalt, which comprises the following steps:

A. preparing modified aggregate: according to the amino silane: anhydrous ethanol: preparing a solution by using ultrapure water (1-3) and a mass ratio of 20:2, adjusting the pH value of the solution to 8-10, hydrolyzing for 8 hours at 60 ℃ to obtain silane hydrolysate, soaking aggregate in the silane hydrolysate for 30 min-1.5 hours, taking out, drying, heating and curing to obtain modified aggregate;

B. preparing a mixture: the modified aggregate and the modified asphalt are uniformly mixed.

Preferably, the aggregates in step a include fine aggregates, coarse aggregates and reclaimed aggregates.

Further preferably, the aggregate in step a comprises basalt, limestone, diabase, granite, quartzite and sandstone.

Preferably, in the step A, the drying temperature is 30-50 ℃, the time is 30min, the curing time is 130-150 ℃, and the time is 2 h.

Preferably, the grading of the modified aggregate is AC13 aggregate grading, and the oilstone ratio of the modified asphalt to the modified aggregate is 3.5-5.5%.

For the prepared modified asphalt and modified aggregate, the invention evaluates the adhesion grade of the asphalt and the aggregate by a water boiling method of T0616-1993 according to the test protocol of highway engineering asphalt and asphalt mixture. And (3) quantitatively analyzing the adhesion performance between the asphalt and the aggregate by adopting a seat drop method based on a surface energy theory.

The invention is further explained below:

the modified nano montmorillonite (NH) secondarily modified by freeze drying technology and aminosilane₂MMT), which is different from the prior quaternary ammonium salt, aminosilane which are modified singly or montmorillonite modified by combining the quaternary ammonium salt and the aminosilane. As shown in fig. 1, in fig. 1(a), NMMT processed by the freeze-drying technique not only can maintain the layer expanding or stripping effect of modified montmorillonite, but also can help to further expand the interlayer spacing of montmorillonite, and is easy for silane molecules to enter the interlayer; meanwhile, the method has almost no loss to the sample; then preparing the surface-NH-containing lyophilized NMMT by using aminosilane for secondary modification₂And stripped NH₂-MMT. The modification rate of aminosilane on montmorillonite is not influenced, but the lyophilized montmorillonite is more beneficial to entering lamella modification due to larger interlayer spacing, the quantity of aminosilane modified on montmorillonite is more, meanwhile, silane molecules can generate self-polymerization between montmorillonite layers, the interlayer spacing of lyophilized montmorillonite is more obviously increased, polymer or asphalt molecules enter the montmorillonite layers, a stable nano composite material is generated, and the cohesion of asphalt is improved. In addition, the NH prepared according to the invention₂-MMT-a is a modified montmorillonite which converts montmorillonite from hydrophilic to lipophilic. Due to NH₂The MMT has stronger lipophilicity, improves the compatibility of the nano montmorillonite and the asphalt and increases the cohesive force of the asphalt. Meanwhile, the asphalt molecules can enter easily due to larger interlayer spacing, and the montmorillonite has stronger barrier property under the action of heat, oxygen and ultraviolet lightThe volatilization of light components in the asphalt can be effectively reduced, the ageing resistance of the asphalt is improved, and the reduction speed of the cohesive force in the asphalt phase is reduced.

In FIG. 1(B), the interlayer spacing can be increased by modifying montmorillonite with quaternary ammonium salt, and then nano montmorillonite modified with aminosilane for the second time is utilized, the modification effect is not increased obviously, the increase range of the interlayer spacing of montmorillonite is small, and aminosilane can perform ion exchange with pre-existing quaternary ammonium salt surface active molecules, but too much organosilane (Soo-Ling Bee et al compositions Part B: Engineering,2017,110:83-95) can not be introduced into the interlayer spacing of montmorillonite.

On the other hand, the invention utilizes amino silane to modify aggregate to obtain the aggregate with-NH on the surface₂Modified aggregate of the terminal organic layer. One end of aminosilane is hydrolyzed and condensed to generate silanetriol, and Si-OH bonds in the silanetriol can perform condensation reaction with carboxyl on the surface of the aggregate to form an organic layer on the surface of the aggregate. -NH in organic layer₂The adhesive agent reacts with groups in the asphalt, so that the adhesive force between the aggregate and the asphalt is effectively improved, and the durability of the asphalt pavement is enhanced.

The invention modifies asphalt and aggregate simultaneously to improve the cohesive force of asphalt and the adhesive force between aggregate and asphalt, thereby improving the adhesive property between asphalt and aggregate, and the synergistic action mechanism of the asphalt and the aggregate is as follows: modifying asphalt by utilizing freezing and amino silane modified nano montmorillonite, and modified NH₂-NH of the surface of MMT₂Can react with carboxylic acid or alcohol in the asphalt and can also react with-OH generated by the hydrolytic condensation of aminosilane on the modified aggregate; not only enhances the interaction between the montmorillonite and the asphalt and improves the cohesion of the asphalt, but also promotes the interaction between the aggregate and the asphalt. On the contrary, the amino silane modified aggregate is subjected to-NH₂Not only reacts with carboxylic acids or alcohols in the asphalt, but also reacts with NH₂-OH reaction on MMT enhancing NH₂The MMT and the asphalt improve the adhesion between the asphalt and the modified aggregate. Therefore, the synergistic effect of the two effectively improves the water damage resistance of the asphalt pavement.

The invention has the following advantages:

(1) compared with the physical modification of the surface of the montmorillonite layer by physical actions such as adsorption, cation/anion exchange and the like, the NH prepared by the method₂The MMT is a chemically modified surface, and the modification effect is good. The freeze-dried montmorillonite increases the interlayer distance and is beneficial to silane molecules to enter, meanwhile, the silane molecules are subjected to self polymerization between the montmorillonite layers, and the interlayer distance of the montmorillonite is further increased, so that polymer or asphalt molecules enter the montmorillonite layers to generate the stable nano composite material.

(2) NH prepared by the invention₂-MMT-a is a modified montmorillonite which converts montmorillonite from hydrophilic to lipophilic. Due to NH₂The MMT has stronger lipophilicity, and improves the compatibility of the nano montmorillonite and the asphalt. Meanwhile, asphalt molecules can enter easily due to larger interlayer spacing, volatilization of light components in asphalt is effectively reduced due to stronger barrier property of montmorillonite under the action of heat, oxygen and ultraviolet light, the anti-aging property of the asphalt is improved, and the reduction speed of the cohesive force in an asphalt phase is reduced.

(3) The amino silane is used for modifying the aggregate surface, so that the surface energy of the aggregate is reduced, and an organic layer is formed on the aggregate surface. -NH in organic layer₂The adhesive agent reacts with the groups in the asphalt to effectively improve the adhesive force between the aggregate and the asphalt.

In a word, compared with the prior art that the adhesion between asphalt and aggregate is improved by modified asphalt or modified aggregate, the asphalt with strong cohesion and the aminosilane organic layer aggregate with strong adhesion on the surface can obviously improve the adhesion between asphalt and aggregate under hot, oxygen, light and water environments, improve the water stability of asphalt mixture and prolong the service life of asphalt pavement. The method has comprehensive research system and good modification effect, and has important significance for improving the water damage of the asphalt pavement.

Drawings

FIG. 1 is a mechanism diagram of the present invention and the quaternary ammonium salt modifier and amino silane compound modified montmorillonite; wherein, the diagram (a) is the mechanism diagram of the montmorillonite modified by freeze drying and aminosilane twice, and (b) is the mechanism diagram of the montmorillonite modified by the compound of quaternary ammonium salt modifier and aminosilane.

FIG. 2 shows NMMT, aminosilane KH-550: NH with NMMT mass ratio of 1:10₂-MMT₁And aminosilane KH-550: NH with NMMT mass ratio of 2:10₂-MMT₂And aminosilane KH-550: NH with NMMT mass ratio of 4:10₂-MMT₄And aminosilane KH-550: NH with NMMT mass ratio of 6:10₂-MMT₆And aminosilane KH-550: NH with NMMT mass ratio of 8:10₂-MMT₈And aminosilane KH-550: NH with NMMT mass ratio of 12:10₂-MMT₁₂Comparing the results of the X-ray diffraction test.

FIG. 3 shows NMMT and NH₂-MMT₄The comparative scanning electron microscope test chart.

FIG. 4 shows NMMT and NH₂-MMT₄X-ray photoelectron spectroscopy test contrast.

FIG. 5 shows granite (Gr) and NMMT/SBS modified asphalt (NMMT/SBS-A-RTFO) after short-term aging and NH after short-term aging₂-MMT₄SBS modified asphalt (NH)₂-MMT₄SBS-A-RTFO) is subjected to boiling test.

FIG. 6 shows Gr and the mass ratio of aminosilane: anhydrous ethanol: scanning electron microscopy (sem) tests of granite (Gr-2-1h) soaked for 1h in a solution of ultrapure water 2:20: 2.

FIG. 7 is a comparison graph of X-ray photoelectron spectroscopy tests of Gr and Gr-2-1 h.

FIG. 8 shows Gr-2-1h and NMMT modified asphalt (NMMT-A) and NH₂-MMT₄Modified asphalt (NH)₂-MMT₄-a) physical comparison after boiling test.

Detailed Description

The invention is further described below with reference to specific preferred embodiments, without thereby limiting the scope of protection of the invention.

The freeze drying technique and the preparation example of the aminosilane modified montmorillonite are as follows:

example 1

Uniformly dispersing 10g of NMMT in 1000ml of ultrapure water at a high speed (the concentration of the NMMT is 0.01g/ml), mechanically stirring at 500rpm, standing, removing lower-layer particles, and taking an upper-layer suspension; pre-freezing the montmorillonite suspension at-20 deg.C for 6h to fully freeze the suspension; and (4) carrying out vacuum freeze drying on the pre-frozen montmorillonite suspension to obtain the freeze-dried NMMT.

10g of lyophilized NMMT was added to 200mL of ultrapure water, and stirred at room temperature for 1 hour to sufficiently destroy clay species in the dispersion medium. And adjusting the pH value of the suspension to 4-4.5 by using a dilute hydrochloric acid solution, and continuously stirring for 1 h. Respectively mixing the following raw materials in parts by weight: adding KH550 into the suspension at NMMT mass ratio of 1:10, 2:10, 4:10, 6:10, 8:10, 12:10, and stirring the suspension in water bath at 80 deg.C for 4 hr. And taking out the suspension, centrifuging, and performing multiple times of ultrasonic treatment and washing by using a mixed solution of absolute ethyl alcohol and ultrapure water to remove unreacted aminosilane KH-550. Then, the precipitate was uniformly dispersed in ultrapure water, frozen and lyophilized. Finally, grinding by using a ball mill, sieving by using a 200-mesh sieve, and respectively mixing the components according to the weight ratio of aminosilane KH 550: NMMT mass ratio to obtain NH₂-MMT₁、NH₂-MMT₂、NH₂-MMT₄、NH₂-MMT₆、NH₂-MMT₈、NH₂-MMT₁₂。

The same experimental conditions are adopted, and aminosilane KH-540 modified montmorillonite is selected according to the mass ratio of aminosilane KH-550: the mass ratio of NMMT is 4:10, and NH is obtained by modification₂-MMT_4-540"has an interlayer spacing of 1.76 nm.

FIG. 2 shows NMMT and NH₂-MMT₁、NH₂-MMT₂、NH₂-MMT₄、NH₂-MMT₆、NH₂-MMT₈And NH₂-MMT₁₂Comparing the results of the X-ray diffraction test. The interlayer spacing of NMMT before modification was 1.25 nm. Modified by amino silane KH-550, NH₂-MMT₁Has an interlayer spacing of 1.52nm, NH₂-MMT₂The interlayer spacing of (1) is 1.55nm, and the growth difference Delta 1 is 0.03 nm; NH (NH)₂-MMT₄Has an interlayer spacing of 1.88nm with NH₂-MMT₂The difference Δ 2 in the increase in interlayer spacing of 0.33 nm; NH (NH)₂-MMT₆Has an interlayer spacing of 1.94nm with NH₂-MMT₄The difference Δ 3 in the increase in the interlayer distance of (a) is 0.06 nm; NH (NH)₂-MMT₈Has an interlayer spacing of 1.98nm with NH₂-MMT₆The difference Δ 4 in the increase in interlayer spacing of 0.04 nm; NH (NH)₂-MMT₁₂Has an interlayer spacing of 2.10nm with NH₂-MMT₈The difference Δ 5 in the increase in interlayer distance of (2) was 0.12 nm. From NH₂-MMT₂To NH₂-MMT₄The difference Delta 2 of the increase of the interlayer spacing of (2) is maximum compared with NH₂-MMT₂The interlayer spacing is increased by 21.3%, the interlayer spacing is increased fastest, and therefore, NH is preferred in subsequent performance tests₂-MMT₄And (6) performing performance test.

FIG. 3 shows NMMT and NH₂-MMT₄The comparative scanning electron microscope test chart. Before modification, the surface of NMMT is smooth, the lamellar structure is compact, and no curling phenomenon exists. Modified by amino silane KH-550, NH₂-MMT₄The lamellar structure of the montmorillonite is loose, and the lamellar structure has a rolled-up phenomenon due to the peeled montmorillonite lamellar.

In the attached drawings, the (a) and (b) are respectively NMMT and NH₂-MMT₄X-ray photoelectron spectroscopy test contrast. Comparing the atomic percentages of the elements in (a) and (b), NH was observed after modification of the aminosilane KH-550 with NMMT₂-MMT₄The contents of Al and Si elements on the surface are both reduced, and the content of C, N element is both increased. The content of the N element is increased from 0.94% to 7.16%, and the comparison with an XPS spectrogram shows that the peak intensity corresponding to the N element has a remarkable enhancement trend.

The adhesion properties of modified asphalt to unmodified aggregate are as follows:

example 2

(1) Using NH prepared in example 1₂-MMT₄Heating 100 parts of asphalt to 160-180 ℃, and adopting a melt blending method to mix 3 parts of NMMT or NH₂-MMT₄Adding into molten asphalt several times, and shearing at 5000r/min for 120min to make NMMT or NH₂-MMT₄Is well dispersed in the asphalt in a molten state. Then developing for 90min at the stirring speed of 600r/min to obtain NMMT-A and NH₂-MMT₄-A。

(2) Selecting Gr aggregate with the particle size of 13.2mm-19mm, ultrasonically cleaning the surface by water, and drying for 9-10h at 100 ℃ until the mass is not changed any more.

(3) NMMT-A, NH was evaluated according to the water boiling method of T0616-1993 in the test protocols for road engineering asphalt and asphalt mixtures₂-MMT₄-adhesion rating of a to Gr aggregates.

The boiling method test result shows that, as shown in fig. 5(a), after the Gr aggregate is wrapped in the NMMT-A, the asphalt film on the surface of the aggregate is partially peeled off and basically kept on the surface of the aggregate, the peeling area percentage is less than 30%, and the adhesion grade is judged to be 3 grade. Gr aggregate in NH, FIG. 5(b)₂-MMT₄After the coating in the step A, a small amount of the asphalt film is locally moved by water, the thickness is not uniform, the stripping area percentage is less than 10 percent, and the adhesion grade is judged to be 4 grade.

Comparative example 1

The difference from example 2 is that:

a single 100 parts of Base bitumen (Base-A) were subjected to the procedure of example 2.

The boiling method test result shows that after Gr aggregate is wrapped in Base-A, the asphalt film on the surface of the aggregate partially falls off and is partially retained on the surface of the aggregate, the stripping area percentage is more than 30 percent, and the adhesion grade is judged to be 2 grade.

In order to further quantitatively analyze the adhesion performance of asphalt and aggregate, the contact angle test of the asphalt and the aggregate is carried out by a seat drop method based on the surface free energy theory, and the test steps are as follows:

(a) and (4) cutting and polishing the Gr aggregate to obtain a smooth and flat surface. Washing with clear water, and finally putting into a 105 ℃ oven for fully drying.

(b) Clean glass sheets were immersed in Base-A at 140 ℃ and taken out to cool to room temperature.

(c) The contact angles of distilled water, formamide and glycerol at Base-A, Gr, as measured by a contact angle tester, are shown in Table 1.

Example 3

(1) Heating 100 parts of asphalt to 160-180 deg.C, and mining3 portions of NMMT or NH are mixed by a melt blending method₂-MMT₄Adding into molten asphalt several times, and shearing at 5000r/min for 120min to make NMMT or NH₂-MMT₄Is well dispersed in the asphalt in a molten state. Then the mixture is developed for 90min at the stirring speed of 600r/min to obtain NMMT-A, NH₂-MMT₄-A. Respectively carrying out rotary film heating tests on the two asphalts according to road engineering asphalt and asphalt mixture test procedures JTG E20-2011 to obtain NMMT-A-RTFO and NH₂-MMT₄-A-RTFO。

(3) NMMT-A-RTFO and NH are evaluated according to the water boiling method of T0616-1993 in the test procedures for road engineering asphalt and asphalt mixtures₂-MMT₄-adhesion rating of a-RTFO to Gr aggregates.

The boiling method test result shows that after the Gr aggregate is wrapped in the NMMT-A-RTFO, the asphalt membrane on the surface of the aggregate partially falls off and is partially retained on the surface of the aggregate, the stripping area percentage is more than 30 percent, and the adhesion grade is judged to be grade 2. Gr aggregate in NH₂-MMT₄After the A-RTFO is wrapped, the asphalt membrane on the surface of the aggregate is partially peeled off and basically remained on the surface of the aggregate, the peeling area percentage is less than 30 percent, and the adhesion grade is judged to be 3 grade.

Comparative example 2

The difference from example 3 is that:

a single 100 parts of Base bitumen (Base-A) were subjected to the procedure described in example 3.

The boiling method test result shows that after Gr aggregate is wrapped in the Base-A-RTFO, the asphalt membrane is completely moved by water, the aggregate is basically naked, and the adhesion grade is judged to be grade 1.

(b) Clean glass sheets were immersed in Base-A-RTFO at 140 deg.C and removed to cool to room temperature.

(d) Contact angles of distilled water, formamide and glycerol at Base-A-RTFO, Gr, as measured by a contact angle tester, are shown in Table 1.

Examples of adhesion properties of the base asphalt to the modified aggregate are as follows:

example 4

(1) Selecting granite (Gr) aggregate with the particle size of 13.2-19 mm, ultrasonically cleaning the surface of the granite (Gr) aggregate with water, and drying the granite (Gr) aggregate at 100 ℃ for 9-10 hours until the mass of the granite (Gr) aggregate does not change.

(2) Gamma-aminopropyltriethoxysilane (KH-550) was used: anhydrous ethanol: preparing a solution by using ultrapure water in a mass ratio of 1:20:2, adjusting the pH value of the solution to 8-10 by using a hydrochloric acid solution, stirring the solution for 8 hours in a water bath at 60 ℃ to obtain a KH-550 hydrolysis solution, soaking Gr aggregate in the KH-550 hydrolysis solution for reaction for 30 minutes, drying the Gr aggregate at 40 ℃ for 30 minutes, heating the Gr aggregate at 140 ℃ for 2 hours, and cooling the Gr aggregate to room temperature to obtain modified granite (Gr-1-30 min).

(3) According to the method T0616-1993 in the test procedure of asphalt and asphalt mixture for highway engineering, the adhesion grade of Gr-1-30min aggregate and Base-A is evaluated.

The water boiling method test result shows that the asphalt film on the aggregate surface falls off after the Gr-1-30min is modified, the asphalt film is partially remained on the aggregate surface, the stripping area percentage is more than 30%, and the adhesion grade is judged to be 2 grade.

(b) And (3) performing the same operation as the step (2) on the dried partial aggregate to obtain Gr-1-30min aggregate.

(c) Clean glass sheets were immersed in Base-A at 140 ℃ and taken out to cool to room temperature.

(d) The contact angles of distilled water, formamide and glycerin at Base-A, Gr-1-30min as measured by a contact angle tester are shown in Table 1.

Example 5

The preparation procedure is as in example 4, except that:

the adopted granite modification solution is aminosilane KH-550: anhydrous ethanol: the ultrapure water is prepared according to the mass ratio of 2:20:2, and the prepared modified granite is Gr-2-30 min.

The water boiling method test result shows that a small part of the asphalt membrane on the aggregate surface falls off after the Gr-2-30min is modified, the asphalt membrane is basically kept on the aggregate surface, the stripping area percentage is less than 30%, and the adhesion grade is judged to be grade 3.

The contact angles of distilled water, formamide and glycerin at Base-A, Gr-2-30min as measured by a contact angle tester are shown in Table 1.

Example 6

The preparation procedure is as in example 4, except that:

the adopted granite modification solution is aminosilane KH-550: anhydrous ethanol: the preparation method comprises the following steps of preparing ultrapure water according to the mass ratio of 2:20:2, soaking Gr aggregate in KH-550 hydrolysis solution for 1h, and preparing Gr-2-1h modified granite.

The water boiling method test result shows that on the surface of the modified Gr-2-1h aggregate, a small part of an asphalt film moves by water, the thickness is not uniform, the stripping area percentage is less than 10%, and the adhesion grade is judged to be 4 grade.

The contact angles of distilled water, formamide and glycerol at Base-A, Gr-2-1h as measured by a contact angle tester are shown in Table 1.

FIG. 6 is a comparative graph of the scanning electron microscopy tests on Gr and Gr-2-1 h. Before modification, Gr has rough and uneven surface and has concave-convex shape. After being modified by amino silane KH-550, the surface of Gr-2-1h becomes smoother and presents a layer of uniform and flat organic film.

FIG. 7(a) and (b) are comparative graphs of X-ray photoelectron spectroscopy test of Gr and Gr-2-1h, respectively. Comparing the atomic number percentages of the elements in (a) and (b), the contents of Al, Si and C elements on the surface of Gr-2-1h are all reduced after modification of the amino silane KH-550, and the content of N element is increased from 7.7% to 12.15%. And compared with an XPS spectrogram, the peak intensity corresponding to the N element on the surface of Gr-2-1h has obvious enhancement tendency after modification.

Examples of adhesion properties of modified asphalt to modified aggregate are as follows:

example 7

(1) Heating 100 parts of asphalt to 160-180 ℃, and adopting a melt blending method to mix 3 parts of NMMT or NH₂-MMT₄Adding into molten asphalt several times, and shearing at 5000r/min for 120min to make NMMT or NH₂-MMT₄Is well dispersed in the asphalt in a molten state. Then the mixture is developed for 90min at the stirring speed of 600r/min to obtain NMMT-A, NH₂-MMT₄-A。

(3) Adopting amino silane KH-550: anhydrous ethanol: preparing a solution by using ultrapure water in a mass ratio of 2:20:2, adjusting the pH value of the solution to 8-10 by using a hydrochloric acid solution, stirring the solution in a water bath at 60 ℃ for 8 hours to obtain a KH-550 hydrolysis solution, soaking Gr aggregates in the KH-550 hydrolysis solution for reacting for 1 hour respectively, drying the Gr aggregates at 40 ℃ for 30min, heating the Gr aggregates at 140 ℃ for 2 hours, and cooling the Gr aggregates to room temperature to obtain Gr-2-1h aggregates.

(4) NMMT-A, NH was evaluated according to the method T0616-1993 in the test protocols for road engineering asphalt and asphalt mixtures₂-MMT₄-adhesion rating of A to Gr-2-1h aggregates.

The boiling method test result shows that after Gr-2-1h is wrapped in NMMT-A, as shown in figure 8(a), a small part of the asphalt film moves by water, the thickness is not uniform, the stripping area percentage is less than 10%, and the adhesion grade is judged to be 4 grade. In FIG. 8(b), Gr-2-1h is at NH₂-MMT₄After coating in the step A, the asphalt film is completely preserved, the stripping area percentage is close to 0, and the adhesion grade is judged to be 5 grade.

(a) clean glass sheets were immersed in NMMT-A, NH at 140 deg.C₂-MMT₄And (A), taking out and cooling to room temperature.

(b) Measuring the content of distilled water, formamide and glycerol in NMMT-A, NH by using a contact angle tester₂-MMT₄The contact angles on-A and Gr-2-1h are shown in Table 1.

Example 8

The procedure is as in example 7, except that:

NMMT-A, NH prepared in example 7 was used₂-MMT₄A, respectively carrying out NMMT-A, NH on road engineering asphalt and asphalt mixture test procedures JTG E20-2011₂-MMT₄the-A is subjected to a rotary thin film heating test to obtain NMMT-A-RTFO and NH₂-MMT₄-A-RTFO。

The boiling method test result shows that after Gr-2-1h aggregate is wrapped in NMMT-A-RTFO, a small part of asphalt membrane on the surface of the aggregate falls off and is basically kept on the surface of stone, the stripping area percentage is less than 30 percent, and the adhesion grade is judged to be 3 grade. Gr-2-1h in NH₂After being wrapped in MMT-A-RTFO, the asphalt membrane is completely preserved, the stripping area percentage is close to 0, and the adhesion grade is judged to be 5 grade.

Measuring the contents of distilled water, formamide and glycerol in NMMT-A-RTFO and NH by using a contact angle tester₂-MMT₄The contact angles on A-RTFO, Gr-2-1h are shown in Table 1.

TABLE 1 contact Angle of asphalt and aggregate (Unit: °)

Note: gr: unmodified granite. Gr-1-30 min: the granite comprises the following components in percentage by mass: anhydrous ethanol: the immersion time in the solution of ultrapure water at a ratio of 1:20:2 was 30 min. Gr-2-30 min: the granite comprises the following components in percentage by mass: anhydrous ethanol: the immersion time in the solution of ultrapure water at a ratio of 2:20:2 was 30 min.Gr-2-1 h: the mass ratio of amino silane: anhydrous ethanol: the immersion time in the ultrapure water solution was 1:20:2, 1 h. Base-A: a base asphalt. NMMT-A: 3% NMMT + Base-A. NH (NH)₂-MMT₄-A：3％NH₂-MMT₄+ Base-A. RTFO: representing a short term aging test for asphalt.

From the surface energy theory, work of adhesion and work of exfoliation of the asphalt with the aggregate in each example were calculated as shown in table 2.

TABLE 2 work of adhesion and work of exfoliation of bitumen to aggregate (unit: mJ/m)²)

The adhesion work only represents the magnitude of the adhesion force of asphalt and aggregate in a dry and anhydrous state, and the peeling work represents the interaction process of three systems of water-aggregate-asphalt in the presence of water. Table 2 shows that the adhesion work of the modified aggregate to asphalt is greater than that of the unmodified aggregate, and the exfoliation work of the modified aggregate is less than that of the unmodified aggregate, which indicates that the adhesion between asphalt and aggregate is significantly improved after the aggregate is modified by the aminosilane solution. Comparing example 4 and example 5, it is seen that increasing the concentration of the aminosilane solution at a given soaking time further improves the adhesion of the asphalt to the aggregate. Comparing example 5 and example 6, it is known that the work of adhesion to asphalt increases and the work of exfoliation decreases with increasing the time of infiltration of the aggregate at a given concentration of aminosilane solution, indicating that increasing the time of infiltration reduces the degree of exfoliation of asphalt from the aggregate in the presence of water. From example 7, NMMT-A, NH compares Base-A to Gr aggregate₂-MMT₄The adhesion work of the-A and the Gr-2-1h aggregate is greatly increased, the peeling work is obviously reduced, and particularly NH is adopted₂-MMT₄The double modification method of the aggregate of-A and Gr-2-1h has the advantages that the adhesion work is improved by 13 percent, the peeling work is reduced by 23 percent, and the adhesion of asphalt and the aggregate is effectively improved.

As can be seen from Table 2, the work of adhesion to the aggregate decreased and the work of exfoliation increased after a short period of aging, indicating that the aged asphalt decreased the work of adhesion to the aggregateAdhesiveness. From example 8, NH₂-MMT₄The adhesion work between the-A-RTFO and the aggregate is greater than the NMMT-A-RTFO, the mut mutexfoliation work is less than the NMMT-A-RTFO, indicating NH₂-MMT₄The adhesion between the-a-RTFO and the aggregate is better than that of NMMT-a-RTFO. NH in comparison with comparative example 2₂-MMT₄A is aged for a short period, but NH is used₂-MMT₄The double modification method of the-A-RTFO and the Gr-2-1h aggregate still obviously improves the adhesion between the asphalt and the aggregate, improves the adhesion work by 8 percent and reduces the peeling work by 21 percent. Indicating NH modified by aminosilane₂-MMT₄The anti-aging property of the asphalt is obviously improved, the reduction of the cohesion of the asphalt is reduced, and the adhesion property of the asphalt and the aggregate is effectively improved.

As described above, NMMT modified with aminosilane has a large amount of-NH on the surface₂The compatibility of the modified asphalt with asphalt is enhanced, and the modified asphalt prepared by using the modified asphalt as a single modifier can effectively improve the cohesion of the asphalt without adding other modifiers. The surface of the aggregate modified by the amino silane solution also forms an amino silane organic layer with stronger adhesion, so that the adhesion between the asphalt and the aggregate interface in a wet environment and a high-temperature environment is enhanced. In addition, increasing the solution concentration or the soaking time further improves the adhesion of the asphalt to the aggregate interface. The method not only can effectively improve the adhesion performance of the unaged asphalt and the aggregate, but also can obviously improve the adhesion performance of the asphalt aged for a short time and the aggregate.

The above description is only a preferred embodiment of the present application, and is not intended to limit the present application in any way, and those skilled in the art should understand that they can make various changes and modifications within the technical scope of the present application without departing from the scope of the present application, and all changes and modifications should be interpreted as equivalent to the above description.

Claims

1. The modified asphalt is characterized in that the modified asphalt is prepared by adding an asphalt modifier into asphalt;

the preparation method of the asphalt modifier comprises the following steps:

(1) uniformly dispersing montmorillonite in ultrapure water to obtain a suspension; pre-freezing the suspension, and then carrying out vacuum freeze drying to obtain freeze-dried montmorillonite;

2. The modified asphalt of claim 1, wherein the concentration of the suspension in step S1 is 0.006g/ml to 0.014 g/ml.

3. The modified asphalt of claim 1, wherein the aminosilane has the general formula: Y-R-Si-X, wherein Y is amino, R is a C3-C8 carbon chain, Si is Si atom, and X is methoxy or ethoxy.

4. The modified asphalt of claim 3, wherein the aminosilane is one or more of KH550, KH540, KH792 or KH 602; preferably, the aminosilane is KH 550.

5. Modified bitumen according to any of claims 1 to 4, characterised in that the molar ratio of aminosilane: the mass ratio of the montmorillonite is (1-12) to 10; preferably, the amino silane: the mass ratio of the montmorillonite is 4: 10.

6. The modified asphalt of claim 1, wherein the precipitate is washed several times after centrifugation, and the detergent used is a mixed solution of absolute ethanol and ultrapure water.

7. The modified asphalt of claim 1, wherein the asphalt modifier is added to the asphalt in an amount of 2-5% by weight.

8. A method of improving the adhesion of the modified asphalt of any one of claims 1-7 to aggregate at the interface, comprising the steps of:

A. preparing modified aggregate: according to the amino silane: anhydrous ethanol: preparing a solution by using ultrapure water = (1-3): a mass ratio of 20:2, adjusting the pH value of the solution to 8-10, hydrolyzing for 8h at 60 ℃ to obtain silane hydrolysate, soaking aggregate in the silane hydrolysate for 30 min-1.5 h, taking out, drying, heating and curing to obtain modified aggregate;

B. preparing a mixture: mixing the modified aggregate with the modified asphalt.

9. The method according to claim 8, wherein the aggregates in step a comprise fine aggregates, coarse aggregates and reclaimed aggregates; preferably, the aggregate in step a comprises basalt, limestone, diabase, granite, quartzite and sandstone; further preferably, the modified aggregate grading is AC13 aggregate grading, and the oilstone ratio of the modified asphalt to the modified aggregate is 3.5-5.5%.

10. The method according to claim 8, wherein the drying temperature in step A is 30-50 ℃ for 30min, and the heating and curing temperature is 130-150 ℃ for 2 h.