阅读说明：本技术 一种改性沥青及其应用 (Modified asphalt and application thereof ) 是由 梁波 张宽宽 石凯 郑健龙 于 2020-08-24 设计创作，主要内容包括：本发明公开了一种改性沥青及其应用。本发明利用冷冻干燥法和氨基硅烷修饰纳米蒙脱土,将其作为单一沥青改性剂添加至沥青中,有效提高了蒙脱土与沥青的分散性和相容性,增强了沥青的内聚力。为进一步增强沥青与酸性集料之间的黏附力,采用氨基硅烷改性酸性集料表面,降低了集料的表面能,提高沥青与集料之间的黏附力。相比基质沥青与花岗岩集料,采用单一氨基硅烷修饰蒙脱土改性沥青与改性集料的双向改性方法,其黏附功提高了13%,剥落功减小23%。沥青经短期老化后,采用双向改性方法,沥青与集料的黏附性能仍有明显改善,其黏附功提高了8%,剥落功减小21%,可有效改善沥青路面的水损害。(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.)

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) 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.

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.

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: