CN111793370B - Salt-tolerant asphalt mixture and preparation method thereof - Google Patents

Salt-tolerant asphalt mixture and preparation method thereof Download PDF

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CN111793370B
CN111793370B CN202010823524.6A CN202010823524A CN111793370B CN 111793370 B CN111793370 B CN 111793370B CN 202010823524 A CN202010823524 A CN 202010823524A CN 111793370 B CN111793370 B CN 111793370B
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asphalt mixture
salt
asphalt
amps
mixture
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CN111793370A (en
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徐亮
郭玉峰
任维锋
王伟
潘承志
郭航
穆长儒
李钊
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Changchun Institute of Applied Chemistry of CAS
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Changchun Institute of Applied Chemistry of CAS
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L95/00—Compositions of bituminous materials, e.g. asphalt, tar, pitch
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F212/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an aromatic carbocyclic ring
    • C08F212/02—Monomers containing only one unsaturated aliphatic radical
    • C08F212/04—Monomers containing only one unsaturated aliphatic radical containing one ring
    • C08F212/06—Hydrocarbons
    • C08F212/08—Styrene
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F220/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride ester, amide, imide or nitrile thereof
    • C08F220/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
    • C08F220/52—Amides or imides
    • C08F220/54—Amides, e.g. N,N-dimethylacrylamide or N-isopropylacrylamide
    • C08F220/58—Amides, e.g. N,N-dimethylacrylamide or N-isopropylacrylamide containing oxygen in addition to the carbonamido oxygen, e.g. N-methylolacrylamide, N-(meth)acryloylmorpholine
    • C08F220/585—Amides, e.g. N,N-dimethylacrylamide or N-isopropylacrylamide containing oxygen in addition to the carbonamido oxygen, e.g. N-methylolacrylamide, N-(meth)acryloylmorpholine and containing other heteroatoms, e.g. 2-acrylamido-2-methylpropane sulfonic acid [AMPS]
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L2205/00—Polymer mixtures characterised by other features
    • C08L2205/03—Polymer mixtures characterised by other features containing three or more polymers in a blend

Abstract

The invention belongs to the technical field of highways and discloses a salt-tolerant asphalt mixture and a preparation method thereof, wherein AMPS is poured into a three-neck flask, N-dimethylformamide is added, and the mixture is stirred and dissolved at room temperature to be in a transparent state; adjusting the constant temperature water bath heating device to a fixed temperature of 85 ℃ to ensure that the reaction mixture and the water tank are heated to 85 ℃ together; adding benzoyl peroxide, dripping styrene, and stirring at constant temperature of 85 ℃ for 5h at constant speed; after the reaction is finished, cooling the reaction to room temperature, and separating the solvent by distillation to obtain an St/AMPS binary polymer; and (3) carrying out dry mixing molding on the SBS modified asphalt mixture and the AMPS polymer to obtain the salt-tolerant asphalt mixture. The invention improves the cohesive force between asphalt and aggregate and the dynamic stability of the asphalt mixture, relieves the decline trend of the pavement performance of the asphalt mixture under the salt freeze-thaw condition, and can be applied to the asphalt pavement in alpine regions.

Description

Salt-tolerant asphalt mixture and preparation method thereof
Technical Field
The invention belongs to the technical field of highways, and particularly relates to a salt-tolerant asphalt mixture and a preparation method thereof.
Background
At present, in the construction of asphalt pavements, the construction is basically mechanical, the efficiency is high, the construction period is short, the comfort level in the driving process of an automobile is excellent, and the maintenance process in the later period is very convenient. In recent years, a large number of modified asphalts have emerged through the use of a series of modifiers, the most prominent of which is rubber-SBS modified asphalt, SBS being a styrene thermoplastic elastomer, a styrene-butadiene-styrene triblock copolymer. The two-phase separation structure can form a space three-dimensional network structure with the asphalt matrix, so that the temperature performance, the tensile property, the elasticity, the cohesive property, the stability and the aging resistance of the mixture of the asphalt matrix are effectively improved, and the two-phase separation structure plays a vital role in improving the service performance and the service quality of a pavement and prolonging the service life of the pavement. Subsequently, new problems are discovered, such as performance influence under the action of freeze-thawing of salt is not reflected.
Therefore, there is a need for improvement research on rubber SBS modified asphalt. The use of a large amount of snow melting salt in the snowfall of seasonal freezing zones can accelerate the erosion damage of the rubber SBS composite modified asphalt mixture in the salt solution. Therefore, under such a complicated and severe environment, various road performance indexes improved by the rubber SBS composite modified asphalt mixture have been systematically studied by many scholars, but studies on improving the road performance of the rubber SBS composite modified asphalt mixture under the coupling of high and low temperature changes and erosion of frozen salt have not been made, and intensive studies have yet been made. 2-acrylamide-2-methyl propanesulfonic Acid (AMPS) is a high molecular organic monomer, and has wide application prospect at present, and in the industry, the 2-acrylamide-2-methyl propanesulfonic acid is used as a raw material and is a water-soluble copolymer which is subjected to polymerization reaction with other monomer molecules, is used for oilfield chemicals, and has excellent high temperature resistance, salt resistance and hydrolytic stability. The AMPS product is industrialized and widely applied to asphalt pavements, and the pavement performance of the asphalt mixture is reduced slightly more slowly under the salt freezing and thawing condition. Therefore, it is necessary to study this aspect and provide a corresponding theoretical guidance technology for practical engineering applications.
The problems existing in the prior art are as follows:
1) crystal extension effect of snow melting agent on asphalt pavement interior
As the surrounding environment continues to dry, the water in the snowmelt solution that accumulates in the pores inside the asphalt pavement will gradually evaporate. Salt solution liquid crystal can be produced during the evaporation to certain expansion pressure can take place when the salt solution crystallization melts, the inside space in road surface has been filled gradually in the continuous accumulation of crystal, and the expansion pressure that produces by the crystallization can reduce the adhesion force between pitch and the aggregate, thereby makes bituminous paving's inner structure suffer destruction, and then makes bituminous paving's intensity reduce, thereby has accelerateed bituminous paving disease's production.
When the gaps inside the asphalt pavement are soaked by the salt solution of the snow melting agent, crystallization reaction can occur, and the strength of the asphalt binder is reduced. Although sodium ions lubricate the adhesion between aggregates, they also cause a reduction in the intrusion force and the internal friction angle of the inside thereof due to the entry of a salt solution, thereby causing deterioration in the various surface properties of the asphalt pavement.
2) Emulsification of snow-melting agent on asphalt pavement
When the snow-melting agent is spread on the road surface, the freezing point of the ice and snow is reduced to form a liquid phase, and under the action of vehicle load, the snow-melting salt solution on the road surface can continuously permeate downwards, so that the salt solution is gathered in the asphalt road surface. When the contact range of the solution and the surface of the asphalt material is enlarged, sodium ions in the salt solution react with the asphalt binder and generate a chemical adsorption layer, and the performance of the chemical adsorption layer is extremely unstable. As the water content increases, it will continue to emulsify the asphalt and the sodium ions in the salt solution will react with the alkaline aggregates in the binder to produce a silicate gel. The occurrence of the emulsification reaction and the formation of the silicate gel material have a strong effect of reducing the adhesive strength between the asphalt binder and the aggregate, resulting in insufficient internal cohesive force and the occurrence of detachment and deformation.
When the snow-melting agent is spread on the asphalt pavement, the surface activity of the solution is greater than that of the asphalt, so that the solution after the snow-melting agent melts the ice and snow is more easily adsorbed on the asphalt and the aggregate, the asphalt and the aggregate are separated, and the pavement damage is accelerated. Meanwhile, the salt solution formed when the snow melting agent melts the ice and snow can permeate into the inside of the asphalt pavement to cause the expansion and crystallization of the salt solution inside the asphalt pavement, and more energy is needed during melting, so that the emulsification reaction is further aggravated, the damage of the pavement structure is caused, and particularly, the damage of pore water to the asphalt pavement is caused.
3) Accelerated aging effect of snow melting agent on asphalt pavement
When the snow-melting agent is spread on the road surface, the solution can enable the asphalt road surface to be in a soaking state for a long time, and because a large amount of chloride ions exist in the snow-melting salt solution, the solution can react with the asphalt mastic to promote the rigidity modulus of the asphalt mastic to be continuously increased, so that the ductility of the asphalt binder is reduced, the brittleness of the material is increased, the flexibility of the asphalt mixture and the deformation capacity of the asphalt mixture are reduced, and the aging of the asphalt road surface is further accelerated.
The reasons for the aging of asphalt pavement are many, and are collectively shown in the following conditions: the adsorption force between the asphalt mortar and the aggregate is reduced; under the condition of low temperature for a long time, the ductility of the asphalt material is reduced irreversibly, so that the maximum bending strain is reduced; the accumulated water in the asphalt pavement under natural conditions causes water damage to the asphalt pavement structure under the repeated action of expansion crystallization, high and low temperature circulation alternation and dynamic load. At the same time, slow cracking of the asphalt pavement is caused at low temperatures.
Aiming at the defects of the prior art, the invention adopts the introduction of a salt-tolerant high polymer and SBS modified asphalt mixture for composite modification. When the asphalt pavement is subjected to deicing and snow removal by the snow-melting agent again, the damage of salt freezing and thawing action to the asphalt pavement structure can be properly reduced.
Through the above analysis, the problems and defects of the prior art are as follows:
(1) the performance influence of the existing rubber SBS modified asphalt under the action of salt freeze thawing is not reflected.
(2) The snow melting agent can damage the internal structure of the asphalt pavement under the stretching action of the crystals inside the asphalt pavement, so that the strength of the asphalt pavement is reduced, and the generation of asphalt pavement diseases is accelerated.
(3) The emulsification of the snow melt agent on the asphalt pavement strongly reduces the adhesive strength between the asphalt binder and the aggregate, which results in insufficient internal adhesion and the occurrence of drop and deformation.
(4) The snow melting agent has an accelerated aging effect on the asphalt pavement, so that the ductility of the asphalt binder is reduced, the brittleness of the material is increased, the flexibility of the asphalt mixture and the deformation capacity of the asphalt mixture are reduced, and the aging of the asphalt pavement is further accelerated.
The difficulty in solving the above problems and defects is:
at present, snow melting agents are basically used at home and abroad to remove ice and snow. The snow-melting agent is mainly divided into two types, one type is an organic snow-melting agent, the main component of the snow-melting agent is potassium acetate, the snow-melting agent has quite good snow-melting capability, the pavement structure is basically not damaged, but the snow-melting agent cannot be widely popularized due to the high price; the other is the inorganic snow-melting agent which takes chloride as the main component, has low price and is widely popularized and used, but the large use of the chloride snow-melting agent can not only destroy surface water, soil and vegetation and destroy the balance of ecological environment, but also can generate adverse effect on pavement materials, bridges and culvert structures.
In conclusion, the key difficulty in solving the problems and defects is to combine the analysis and ecological environment protection to reduce the adverse effects of chloride on the pavement structure and ecological environment.
The significance of solving the problems and the defects is as follows:
along with the continuous progress of science, the research is continuous and deep, the novel snow-melting agent is green and environment-friendly, basically has no harm to the road surface, green plants and public facilities, has high snow-melting speed, small adding dosage and low use cost, but the novel snow-melting agent is not developed at present, so chlorine salt can be neutralized and decomposed through physicochemical reaction, the corrosion problem of the traditional product to roads and bridges is solved from the source, and the influence and the damage of the snow-melting agent to the roads and the environment are reduced to the maximum extent. Therefore, the harm of the snow-melting agent can be avoided to a greater extent.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a salt-tolerant asphalt mixture and a preparation method thereof, aiming at searching the influence of an AMPS polymer on the road performance of an SBS modified asphalt mixture.
The invention is realized in such a way that the preparation method of the salt-tolerant asphalt mixture comprises the following steps:
step one, pouring a fixed amount of 103.5g of AMPS into a three-neck flask, adding 250ml of N, N-dimethylformamide as a solvent, and stirring and dissolving at room temperature to be transparent.
Step two, the apparatus for heating with a thermostatic water bath was adjusted to a fixed temperature of 85 ℃ so that the reaction mixture and the water tank were co-heated to 85 ℃.
Step three, adding 1.3g of benzoyl peroxide, dropwise adding 58ml of styrene, and stirring for 5 hours at the constant temperature of 85 ℃.
And step four, after the reaction is finished, cooling the reaction to room temperature, and separating the solvent by distillation to obtain the St/AMPS binary polymer.
And step five, carrying out dry mixing molding on the SBS modified asphalt mixture and the AMPS polymer to obtain the salt-tolerant asphalt mixture.
Further, in the third step, the mixing ratio of the styrene to the AMPS is 1: 1.
Further, the equipment required for AMPS binary polymer synthesis comprises: tesser 27 fourier infrared spectrometer; SYC-15B super constant temperature water bath; d971-60 mixers; 702-40 drum heater.
The invention also aims to provide a salt-tolerant asphalt mixture prepared by the preparation method of the salt-tolerant asphalt mixture. (without specific proportions, the optimum oilstone ratio should be determined by Marshall's experiment for each component of the mix from batch to batch, and the amount of each component used is determined by the optimum oilstone ratio. the amount of the St/AMPS biopolymer used as the admixture is 1% of the mass of the test block, wherein the amount of the admixture is a value set by a large literature summary.
By combining all the technical schemes, the invention has the advantages and positive effects that: the invention provides a salt-tolerant asphalt mixture and a preparation method thereof, which starts from the raw materials of the asphalt mixture, introduces St (styrene)/AMPS binary polymer with salt resistance, high temperature resistance and shear resistance to compositely modify SBS modified asphalt mixture to prepare SA-13 rubber SBS modified asphalt mixture, and respectively analyzes and compares the characteristics of the AC-13 and SA-13 rubber SBS modified asphalt mixtures under the salt solution freeze-thaw condition: the dynamic stability, the freeze-thaw split tensile strength ratio, the bending failure strain and the fatigue times are studied, and the reasons for changing the road performance of the AC-13 and SA-13 rubber SBS modified asphalt mixture are studied, wherein the reasons include: high temperature stability, low temperature crack resistance, water stability and fatigue durability.
(1) In physical properties, the brittleness of the St/AMPS polymer at a low temperature below zero causes the binding power of the asphalt mixture at a low temperature to be reduced, and the bending failure strain of the SA-13 asphalt mixture is reduced; the St/AMPS polymer has a melting point of 220 ℃, and after being mixed with the asphalt mixture, the temperature sensitivity of the St/AMPS polymer is reduced, and the binding power between asphalt and aggregate is improved, so that the dynamic stability of the asphalt mixture is improved, and the St/AMPS polymer can be applied to asphalt pavements in alpine regions.
(2) In terms of chemical properties, due to the introduction of the sulfonate functional group, the sulfonate functional group is an amphiphilic functional group (hydrophilic and oleophilic), free asphalt is adsorbed, so that the binding power of the asphalt mixture is increased, a hydration structure body is generated after the sulfonate functional group is combined with water molecules, a micelle polymer is formed on the surface of aggregate, the reaction of sodium ions and alkali aggregate is effectively prevented to a certain extent, the reduction of the binding power between the asphalt mixtures is relieved, the moisture in the gaps of the asphalt mixture is reduced, the energy required by the asphalt mixture during freeze-thaw expansion is reduced, and the reduction rate of various road performances of the asphalt mixture under the salt freeze-thaw action is reduced.
(3) With the increase of the salt solution concentration from 0% to 4%, the dynamic stability, the bending failure strain, the freeze-thaw splitting tensile strength and the fatigue times of the SA-13 asphalt mixture are all better than those of the AC-13 when 5 freeze-thaw cycles are fixed. The data analysis shows that the reduction rate of the dynamic stability of the SA-13 asphalt mixture is 10.95 percent lower than that of the AC-13 asphalt mixture under the same condition; the reduction rate of the bending failure strain is 14.70 percent lower than that of AC-13; the freezing-thawing splitting tensile strength is 2.71 percent lower than the reduction rate of AC-13; the fatigue number decreased at a rate 9.9% lower than that of AC-13.
Technical effect or experimental effect of comparison. The method comprises the following steps:
the melting point of the AMPS/St polymer is higher than that of SBS modified asphalt, and after the AMPS/St polymer and the SBS modified asphalt are mixed, the temperature sensitivity of the AMPS/St polymer is reduced, and the viscosity of the asphalt is increased; as for the introduction of the sulfonate functional group, the high-temperature performance of the SA-13 asphalt mixture is superior to that of AC-13 due to the fact that the salt resistance of the asphalt mixture is improved from the material per se.
In the aspect of low-temperature crack resistance, due to the addition of the AMPS/St binary polymer, the flexibility of the mixture is reduced, so that the bending-tensile strain resistance of the mixture at the low temperature below zero is reduced, but due to the introduction of a sulfonate functional group, the salt resistance of the asphalt mixture is greatly improved, and in comparison, under the salt freeze-thaw damage, the bending-tensile damage strain of SA-13 is larger than that of AC-13.
In the aspect of water stability, a sulfonate functional group (-SO3-) in the SA-13 asphalt mixture has very excellent hydrophilic capacity, and in the process of soaking in a salt solution, a hydrated combination body is formed between-SO 3-and water inside the SA-13 asphalt mixture to generate micelle aggregates which are adhered to the surfaces of the aggregates, SO that the existence of water molecules in aggregate gaps is reduced, sodium ions are effectively prevented from reacting with alkali aggregates in the mixture, the reduction of the internal binding power of the asphalt mixture is effectively relieved, and the structure of the asphalt mixture is not easy to damage.
In terms of fatigue durability, after the AMPS/St binary polymer is introduced, the fatigue durability of the SBS modified asphalt mixture is improved in terms of the structure and chemical properties of the material, and an effective theoretical basis is provided for further quantitative research in the future.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments of the present application will be briefly described below, and it is obvious that the drawings described below are only some embodiments of the present application, and it is obvious for those skilled in the art that other drawings can be obtained from the drawings without creative efforts.
Fig. 1 is a flow chart of a preparation method of a salt-tolerant asphalt mixture provided by an embodiment of the invention.
FIG. 2 is a schematic diagram of the synthetic principle of a salt-tolerant St/AMPS binary polymer provided by an embodiment of the present invention.
FIG. 3 is a graph showing the curves of the yield and the viscosity reduction rate with the addition of St according to the example of the present invention.
FIG. 4 is a schematic diagram of a t/AMPS binary polymer preparation method provided by an embodiment of the invention.
FIG. 5 is a graph showing the variation of the dynamic stability with salt concentration according to the embodiment of the present invention.
FIG. 6 is a graph of the change in breaking bending strain of AC-13 and SA-13 provided by an embodiment of the present invention.
FIG. 7 is a graph of the tensile strength ratio of the freeze-thaw split test provided by an example of the present invention as the concentration of the salt solution increases.
FIG. 8 is a graph showing the variation of the fatigue counts of AC-13 and SA-13 according to the embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Aiming at the problems in the prior art, the invention provides a salt-tolerant asphalt mixture and a preparation method thereof, and the invention is described in detail below with reference to the accompanying drawings.
As shown in fig. 1, the preparation method of the salt-tolerant asphalt mixture provided by the embodiment of the invention comprises the following steps:
s101, pouring a fixed amount of AMPS of 103.5g into a three-neck flask, adding 250ml of N, N-dimethylformamide as a solvent, and stirring and dissolving at room temperature until the mixture is transparent.
S102, the thermostatic waterbath heating device is adjusted to a fixed temperature of 85 ℃ so that the reaction mixture and the water tank are heated to 85 ℃ together.
S103, adding 1.3g of benzoyl peroxide, dropwise adding 58ml of styrene, and stirring for 5 hours at the constant temperature of 85 ℃.
And S104, after the reaction is finished, cooling the reaction to room temperature, and separating the solvent by distillation to obtain the St/AMPS binary polymer.
And S105, carrying out dry mixing molding on the SBS modified asphalt mixture and the AMPS polymer to obtain the salt-tolerant asphalt mixture.
The invention is further described below in conjunction with the interpretation of terms.
The pavement performance of the asphalt mixture is reduced under the salt freezing and thawing action and the decline trend is reduced.
The invention provides a salt-tolerant asphalt mixture prepared by using the preparation method of the salt-tolerant asphalt mixture.
The present invention will be further described with reference to the following examples.
Examples
(1) SBS is a styrene thermoplastic elastomer, and is a styrene-butadiene-styrene triblock copolymer. The two-phase separation structure enables the asphalt matrix to form a spatial three-dimensional network structure, so that the temperature performance, the tensile property, the elasticity, the cohesive property, the stability and the aging resistance of the mixture of the asphalt are effectively improved, but the performance influence under the action of salt freezing and thawing is not reflected. The invention introduces a salt-tolerant high-molecular monomer material AMPS for improving the road performance of SBS modified asphalt mixture under the action of salt freeze thawing.
Salt-tolerant sulfonic acid group (-SO) is introduced into SBS modified asphalt3-) the specific embodiment is to aggregate the SBS modified asphalt mix with the AMPS by determining the optimum oilstone ratioThe mixture is formed by dry mixing. If the road performance is improved, it can be assumed that the modification occurs in the following three ways: sulfonation modification; chain rigidity modification; and (4) modifying hydrophobic association.
The main reason for the sulfonation modification is due to the sulfonate group (-SO)3-) strong hydration ability, salt tolerance and heat resistance, then sulfonate (-SO) is synthesized by chemical method3-) is introduced into the macromolecular chain of the original chemical material by addition, and is a widely applied modification method at present.
The main principle of chain rigidity modification is that AMPS can be subjected to copolymerization or grafting reaction with a rigid molecular chain containing a benzene ring structure or a cyclic structure. Attempts to reduce the flexibility of polymer chains and to properly harden macromolecular chains are important ways to improve heat resistance, salt resistance, and especially shear resistance. In some polymer patents, it is pointed out that the introduction of benzene rings and some cyclic structures into rigid macromolecular chains by some chemical methods is very effective in increasing the rigidity of the macromolecular chains.
The main principle of the hydrophobic association modification is that alkyl hydrophobic groups in some hydrophobic long chains are introduced into hydrophilic macromolecular chains by a chemical method, on the premise that the overall water solubility of the hydrophobic long chains is not changed, the repulsive force between the obtained polymer and charged ions in the molecule in a salt solution is reduced, the main chain of the macromolecule is bent, and the viscosity is reduced. However, the salt ion has hydrophobic paraffin, and its association is small, so that the salt tolerance of the polymer can be improved, mainly because the hydrophobic association can prevent the rapid reduction of viscosity. According to the relevant scientific conclusions, the factors favoring the hydrophobic association reaction are: the temperature is raised; an electrolyte is added.
(2) St/AMPS binary Polymer Synthesis conditions are preferred
(2.1) principle of Synthesis and raw Material apparatus
Styrene, N-dimethylformamide, benzoyl peroxide and AMPS. Their abbreviations St, DMF, BPO and AMPS, respectively, are used for short in the following expressions. Tesser 27 fourier infrared spectrometer; SYC-15B super constant temperature water bath; d971-60 mixers; 702-40 drum heaters, etc. The synthesis principle of the salt-tolerant St/AMPS binary polymer is shown in figure 2.
(2.2) monomer ratio
In the experiment, the polymerization temperature is determined to be 85 ℃ according to relevant literature reference, the BPO addition amount is 1.0 percent, and the polymerization time is 4 h. The optimum ratio is determined by gradually changing the amount of styrene. The polymer yield and viscosity reduction as a function of styrene content were investigated. The results are shown in fig. 3. It can be seen from the figure that the product yield increases to nearly two thirds, tending to flatten out, since it self-polymerizes as the styrene concentration increases. The viscosity reduction rate of the product first increased to 75.9% and then rapidly decreased, mainly because the high temperature resistance of the copolymer was improved during the addition of styrene. This property plays a significant role in maintaining the tack-reducing properties of the copolymer at high temperatures. However, when the amount of St introduced is too large or too fast, the solubility and viscosity of the polymer are lowered, thereby affecting its properties. The final St to AMPS mix ratio was 1:1 as determined by chemical analysis.
(2.3) preparation method of St/AMPS binary Polymer
Pouring a fixed amount of 103.5g of AMPS into a three-neck flask, adding 250ml of DMF as a solvent, stirring and dissolving at room temperature to be transparent, then adjusting a constant-temperature water bath heating device to a fixed temperature of 85 ℃, so that the reaction mixture and a water tank are heated to 85 ℃, then adding 1.3g of BPO, dropwise adding 58ml of styrene, stirring at a constant temperature of 85 ℃ for 5 hours, cooling the reaction to room temperature after the reaction is finished, and separating the solvent by distillation to obtain a target product. The preparation method is shown in figure 4.
(3) Key improvement point created by the invention
With the increase of the salt solution concentration from 0% to 4%, the dynamic stability, the bending failure strain, the freeze-thaw splitting tensile strength and the fatigue times of the SA-13 asphalt mixture are all better than those of the AC-13 when 5 freeze-thaw cycles are fixed. The data analysis shows that the reduction rate of the dynamic stability of the SA-13 asphalt mixture is 10.95 percent lower than that of the AC-13 asphalt mixture under the same condition; the reduction rate of the bending failure strain is 14.70 percent lower than that of AC-13; the freezing-thawing splitting tensile strength is 2.71 percent lower than the reduction rate of AC-13; the fatigue number decreased at a rate 9.9% lower than that of AC-13.
The invention is further described below in connection with specific experiments.
(1) High temperature stability
And finishing the test piece manufacturing and performance testing according to the method specified by the regulations. The rut test results are shown in Table 1, and the dynamic stability changes of AC-13 and SA-13 are shown in FIG. 5. The test results show that:
1) after rutting tests are carried out on the AC-13 modified asphalt mixture and the SA-13 modified asphalt mixture, the dynamic stability of the obtained modified asphalt mixture meets the standard requirement and is not less than 2400 times/mm.
2) Under the standard, the dynamic stability of the SA-13 asphalt mixture is greater than that of AC-13. This is because the St/AMPS polymers introduced have good temperature resistance, the melting point of which is 220 ℃. In the process of mixing the asphalt mixture, the temperature sensitivity of the part combined with the asphalt is reduced, the viscosity of the asphalt is increased, the higher the viscous resistance of the asphalt mixture is, the stronger the shear-resistant deformation capability is, and the better the high-temperature rutting resistance capability of the asphalt is.
3) The tendency of the dynamic stability of the SA-13 asphalt mixture to be reduced is far less than that of AC-13 under the condition of the same salt concentration. This is because in the SA asphalt mixture, there is also a sulfonate functional group (-SO3-), which has very excellent hydrophilic ability. In the process of soaking in the salt solution, a hydration combined body is generated inside, micelle aggregates are generated and adhered to the surfaces of the aggregates, the existence of water molecules in aggregate gaps is reduced, sodium ions are effectively prevented from reacting with alkali aggregates in the mixture, the reduction of the internal binding power of the asphalt mixture is effectively relieved, and the asphalt mixture structure is not easy to damage.
In conclusion, the melting point of the AMPS/St polymer is higher than that of SBS modified asphalt, and after the AMPS/St polymer and the SBS modified asphalt are mixed, the temperature sensitivity is reduced, and the viscosity of the asphalt is increased; as for the introduction of the sulfonate functional group, the high-temperature performance of the SA-13 asphalt mixture is superior to that of AC-13 due to the fact that the salt resistance of the asphalt mixture is improved from the material per se.
TABLE 1 Rut test dynamic stability record details for each set of test pieces
Figure BDA0002635353190000111
(2) Low temperature cracking resistance
The test temperature is: -10 ℃, loading rate: 50 mm/min, and the span of both ends is 200 mm. And (4) carrying out a low-temperature crack resistance test on the trabecular test piece of the asphalt binder. The flexural strain at failure results are shown in Table 2, and the flexural strain at failure for AC-13 and SA-13 is shown in FIG. 6. The test results show that:
1) under the standard, the failure strain of the SA-13 asphalt mixture is smaller than that of the AC-13 asphalt mixture, and the main reason is that the St/AMPS polymer has certain brittleness at low temperature below zero, the adhesive force between asphalt mixtures is slightly reduced, and the failure strain of the asphalt mixture is lower than that of the AC-13 asphalt mixture. But still meets the specifications.
2) When the concentration of the salt in the snow melting is 0%, the descending rate of the two asphalt mixtures of SA-13 and AC-13 is not greatly different, but when the concentration of the salt is 4%, the descending rate of the bending failure strain of SA-13 is gentler than that of AC-13, and finally is better than that of AC-13.
In conclusion, the flexibility of the mixture is reduced by adding the AMPS/St binary polymer, so that the bending tensile strain resistance of the mixture at the low temperature below zero is reduced, but the salt tolerance of the asphalt mixture is greatly improved due to the introduction of the sulfonate functional group, and in comparison, the bending tensile failure strain of SA-13 is larger than that of AC-13 under the freeze-thaw failure of salt.
TABLE 2 details of the low temperature bending failure strain recording for each set of test pieces
Figure BDA0002635353190000121
(3) Stability to water
And finishing the test piece manufacturing and performance testing according to the method specified by the regulations. The results of the freeze-thaw split tensile ratios are shown in Table 3, and the changes in the freeze-thaw split tensile ratios for AC-13 and SA-13 are shown in FIG. 7. The test results show that:
1) when the concentration of the snowmelt salt solution is 0%, the TSR value of the SA-13 and AC-13 asphalt mixture is reduced to a certain extent after 5 times of freeze-thaw cycle, but the change rate of the SA-13 asphalt mixture is reduced on the whole;
2) when the salt concentration is 4%, the TRS value of the SA-13 asphalt mixture is reduced at a rate lower than the TSR value of the AC-13 asphalt mixture;
in conclusion, the sulfonate functional group (-SO3-) in the SA-13 asphalt mixture has very excellent hydrophilic capacity, and in the soaking of a salt solution, the-SO 3-and water are hydrated and combined in the asphalt mixture to form micelle aggregates which are adhered to the surfaces of the aggregates, SO that the existence of water molecules in aggregate gaps is reduced, the reaction of sodium ions and alkali aggregates in the asphalt mixture is effectively prevented, the reduction of the internal binding force of the asphalt mixture is effectively relieved, and the structure of the asphalt mixture is not easy to damage.
TABLE 3 Freeze-thaw cleavage tensile strength of each group of test pieces is detailed in the test record
Figure BDA0002635353190000131
(3) Fatigue durability
Mixing according to a standard Marshall test piece preparation process, filling the uniformly mixed mixture into a shear compaction test mold, and then forming by using an Italy Cools/IPC PReSBOX shear compaction instrument. Trabecular size after cutting: 380mm by 65mm by 50mm, and fatigue test was carried out by using Cooper multifunction start servo tester. The results of the number of fatigue times are shown in Table 4, and the change in the number of fatigue times of AC-13 and SA-13 is shown in FIG. 8. The test results show that:
under the standard, the fatigue times of the SA-13 asphalt mixture are more than that of AC-13. In a physical state, at room temperature, the AMPS/St binary polymer has high viscosity, strong toughness and good shear resistance; chemically, the sulfonate functional group (-SO3-) is an amphiphilic group, and has hydrophilicity and lipophilicity. It can absorb free asphalt in asphalt mixture to increase the adhesion in asphalt mixture and thus raise its fatigue durability. The test results are shown in fig. 8, and it can be seen that:
1) when the concentration of the snow melting salt is 0%, the fatigue times are reduced, but the reduction rate of the fatigue times of the AC-13 asphalt mixture tends to be faster, and the opposite is true for SA-13.
2) When the salt concentration is 4%, the fatigue frequency of the SA-13 asphalt mixture is reduced at a slower rate than that of the AC-13 asphalt mixture. In the soaking of the salt solution, a hydration combination type is generated inside a sulfonic acid group (-SO3-) to generate micelle aggregates which are adhered to the surfaces of the aggregates, SO that the existence of water molecules in the aggregate gaps is reduced, and the reaction between sodium ions and alkali aggregates in the mixture is effectively prevented, thereby effectively relieving the reduction of the internal binding power of the asphalt mixture and causing the fatigue times of the asphalt mixture to be slowly reduced.
In conclusion, after the AMPS/St binary polymer is introduced, the fatigue durability of the SBS modified asphalt mixture is improved on the structure and chemical properties of the material, and an effective theoretical basis is provided for further quantitative research in the future.
TABLE 4 fatigue times for each set of test pieces
Figure BDA0002635353190000141
The above description is only for the purpose of illustrating the present invention and the appended claims are not to be construed as limiting the scope of the invention, which is intended to cover all modifications, equivalents and improvements that are within the spirit and scope of the invention as defined by the appended claims.

Claims (4)

1. The preparation method of the salt-tolerant asphalt mixture is characterized by comprising the following steps of:
pouring AMPS into a three-neck flask, adding N, N-dimethylformamide as a solvent, and stirring and dissolving at room temperature to be in a transparent state;
heating a constant-temperature water bath heating device to heat the reaction mixture and a water tank together;
step three, adding benzoyl peroxide, dropwise adding styrene, and stirring at constant temperature; the mass ratio of the styrene to the AMPS is 1: 1;
step four, after the reaction is finished, cooling the reaction to room temperature, and separating the solvent by distillation to obtain an St/AMPS binary polymer;
step five, dry-mixing and molding the SBS modified asphalt mixture and the AMPS polymer to obtain the salt-tolerant asphalt mixture;
the second step specifically comprises heating the thermostatic waterbath heating device to a fixed temperature of 85 ℃ so that the reaction mixture and the water tank are heated to 85 ℃ together.
2. The preparation method of the salt-tolerant asphalt mixture according to claim 1, wherein in the third step, the mixture is stirred for 5 hours at a constant temperature of 85 ℃.
3. The method of claim 1, wherein the instrumentation required for AMPS binary polymer synthesis comprises: tesser 27 fourier infrared spectrometer; SYC-15B super constant temperature water bath; d971-60 mixers; 702-40 drum heater.
4. A salt-tolerant asphalt mixture prepared by the preparation method of the salt-tolerant asphalt mixture according to any one of claims 1 to 3.
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CN109337394A (en) * 2018-10-19 2019-02-15 湖北津泰环保科技有限公司 A kind of preparation method of the rubber powder modified asphalt of highly anti-fatigue cracking resistance
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