Epoxy resin modified emulsified asphalt micro-surfacing mixture and preparation method thereof

Abstract

The application discloses an epoxy resin modified emulsified asphalt micro-surfacing mixture and a preparation method thereof, and the preparation steps comprise the following steps: gradient heating of base asphalt to 75-90 DEG C, stirring and shearing after adding nano silicon dioxide to obtain activated base asphalt; preparation of water-based epoxy resin emulsion with a solid content of 45-50%, control of the mass ratio of epoxy resin to emulsifier to 8-10:1, and formation of a stable dispersion system with a particle size of less than 1 micron; preheating of mineral aggregate, stirring and adding of activated base asphalt, and continuous stirring; adding of water-based epoxy resin emulsion, and continuous stirring; adding of ethylene amine curing agent, and continuous stirring to ensure uniform dispersion of the curing agent and avoid incomplete local reaction; and finally, adding of cement and water, and continuous stirring to form a uniform micro-surfacing mixture. The raw material system is upgraded and the process is innovated, so that the road performance such as high-temperature stability and low-temperature crack resistance is remarkably improved, and VOCs emission is greatly reduced, and the application is green and environment-friendly.

Description

Technical Field

[0001] This invention belongs to the field of road engineering materials technology, specifically relating to an epoxy resin modified emulsified asphalt micro-surfacing mixture and its preparation method. Background Technology

[0002] In road engineering, micro-surfacing mixtures are the mainstream pavement maintenance materials, and their performance directly determines the service life of roads and driving safety. Traditional emulsified asphalt micro-surfacing has defects such as insufficient bond strength (bond strength at 60℃ < 0.8MPa), high low-temperature cracking threshold (critical temperature > -15℃), and excessive VOC emissions (> 200g / L), making it difficult to meet the requirements of heavy traffic (annual equivalent axle cycles > 1 million times) and extreme climatic environments. Although waterborne epoxy resin modification technology improves the high-temperature stability of the mixture (dynamic stability < 3000 cycles / mm) by forming a three-dimensional network structure (crosslinking density < 0.8 × 10³ mol / cm³), the existing technology still has the following bottlenecks:

[0003] Insufficient interfacial compatibility: Traditional processes do not activate the base asphalt, resulting in an interfacial energy difference of >20mN / m between aggregate, asphalt and resin, and high sensitivity to water damage (freeze-thaw splitting strength ratio TSR <80%).

[0004] The oil-stone ratio optimization is too simplistic: relying solely on the single index of wet wheel wear without considering viscoelastic properties, such as complex modulus G* < 1.0 kPa, can easily lead to high-temperature oil bleeding or low-temperature cracking.

[0005] Environmental and energy-saving limitations: Solvent-based epoxy resin systems have high VOC emissions, and additional drying treatment is required for application on damp substrates, resulting in high resource consumption. In existing technologies, micro-surfacing mixtures prepared with solvent-based epoxy resin systems need to be dried to a moisture content of ≤3% (mass fraction) on damp substrates, and ≤2% in some harsh scenarios, so that the substrate is in a state of "no visible water on the surface and no free water inside" to avoid affecting epoxy curing and bonding.

[0006] Existing research has attempted to improve low-temperature performance through styrene-butadiene rubber (SBR) composite modification, but it cannot simultaneously solve multiple problems such as high-temperature stability, low-temperature crack resistance and VOC emission reduction. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide an epoxy resin modified emulsified asphalt micro-surfacing mixture with excellent road performance and environmental protection performance, and its preparation method, in order to overcome the shortcomings of the prior art.

[0008] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0009] A method for preparing an epoxy resin-modified emulsified asphalt micro-surfacing mixture includes the following steps:

[0010] (1) Activation pretreatment of matrix asphalt: The matrix asphalt is heated in a gradient. First, it is heated to 35℃~50℃ and kept at that temperature. Then, it is heated to 55℃~70℃ and kept at that temperature. Then, it is heated to 75℃~90℃. Nano silica is added and stirred and sheared to obtain activated matrix asphalt.

[0011] (2) Preparation of waterborne epoxy resin emulsion: Waterborne epoxy resin emulsion with a solid content of 45% to 50% was prepared by phase inversion method, and the mass ratio of epoxy resin to emulsifier was controlled to be 8 to 10:1 to form a stable dispersion system with a particle size ≤1μm.

[0012] (3) Synergistic compounding of multiphase system: preheat the mineral aggregate, add the activated matrix asphalt from step (1) while stirring, and continue stirring; add the waterborne epoxy resin emulsion from step (2) and continue stirring; then add the ethyleneamine curing agent and continue stirring to ensure that the curing agent is evenly dispersed and to avoid incomplete local reaction; finally add cement and water and continue stirring to form a uniform micro-surfaced mixture.

[0013] In the above-mentioned method for preparing epoxy resin modified emulsified asphalt micro-surfacing mixture, preferably, in step (1), the nano silica is a nano silica dispersion with a solid content of 15% to 25%, an amount of 0.2% to 0.5% of the mass of the base asphalt, and a particle size of 20 nm to 50 nm.

[0014] In the preferred embodiment of the above-mentioned method for preparing epoxy resin modified emulsified asphalt micro-surfacing mixture, the mass ratio of the base asphalt to the mineral aggregate is 6% to 10%; the mass ratio of the epoxy resin to the mineral aggregate is 4% to 8%; the amount of the curing agent is 15% to 20% of the mass of the epoxy resin; the amount of cement is 2% to 4% of the mass of the mineral aggregate; and the amount of water accounts for 8% to 12% of the total mass of the system.

[0015] In the preferred embodiment of the above-mentioned method for preparing epoxy resin modified emulsified asphalt micro-surfacing mixture, in step (1), the heat preservation time is 20 min to 40 min; the stirring and shearing speed is 1200 r / min to 2000 r / min, and the stirring and shearing time is 20 min to 40 min; during the stirring and shearing process, the nano-silica and the matrix asphalt mixture heat up due to friction, and after shearing, the temperature is gradually reduced to 75℃ to 90℃, with a temperature reduction of 1.5℃ to 2.5℃ in each stage, and a heat preservation time of 5 min to 10 min in each stage.

[0016] In the preferred method for preparing the epoxy resin modified emulsified asphalt micro-surfacing mixture, step (2) involves mixing epoxy resin with an emulsifier and emulsifying at a rotation speed of 2000 r / min to 2500 r / min for 15 min to 25 min.

[0017] In the above-mentioned method for preparing epoxy resin modified emulsified asphalt micro-surfacing mixture, preferably, in step (3), the mineral aggregate is preheated to a temperature of 135℃~145℃, the stirring speed is 1800r / min~2200r / min, and the total stirring time from the addition of activated matrix asphalt does not exceed 5min.

[0018] In the above-mentioned method for preparing epoxy resin modified emulsified asphalt micro-surfacing mixture, preferably, the mineral aggregate is basalt mineral aggregate with angularity ≥45%, crushing value ≤28%, and gradation conforming to AC-13C, MS-2, MS-3 or MS-4 standards.

[0019] The base asphalt is a cationic slow-cracking emulsified asphalt with a solid content ≥62% and a charge density of 120mV~150mV;

[0020] The epoxy resin is a bisphenol A type epoxy resin with an epoxy equivalent of 180 g / mol to 200 g / mol.

[0021] The curing agent is an ethyleneamine addition-type curing agent with an amine value of 300 mgKOH / g to 350 mgKOH / g;

[0022] The cement is aluminate cement.

[0023] The preferred method for preparing epoxy resin-modified emulsified asphalt micro-surfacing mixtures involves establishing a dual-index evaluation model of abrasion amount and complex modulus G* by measuring the wet wheel abrasion and dynamic shear rheology of the micro-surfacing mixture specimens to determine the optimal asphalt-aggregate ratio. The load for the wet wheel abrasion test is 1.22 kg. cm -2 The wear rate was 500 revolutions, and the dynamic shear rheological test temperature was 64℃ with a frequency of 10 rad / s. It was found that when the wear rate is ≤400 g / m³, the wear rate is suitable for the following conditions: 2 Furthermore, the complex modulus G* ≥ 1.2 kPa corresponds to the optimal oilstone ratio.

[0024] In the above-mentioned method for preparing epoxy resin modified emulsified asphalt micro-surfacing mixture, preferably, the optimal asphalt-aggregate ratio is 6.5% to 8.5%, and the density error of the micro-surfacing mixture specimen is ≤1.5%, so as to ensure that the repeatability accuracy of the test data meets the requirements of ASTM D6933 standard.

[0025] The above-mentioned method for preparing epoxy resin modified emulsified asphalt micro-surfacing mixture preferably involves verifying the road performance of the micro-surfacing mixture prepared with the optimal asphalt-aggregate ratio through a three-level performance evaluation. The evaluation indicators for the three-level performance are: stiffness modulus ≤ 300 MPa, freeze-thaw splitting strength ratio ≥ 85%, and accelerated loading abrasion loss ≤ 120 g / m. 2 .

[0026] In the above-mentioned method for preparing epoxy resin modified emulsified asphalt micro-surfacing mixture, preferably, the construction temperature range of the micro-surfacing mixture is 5℃~35℃, and the open traffic time is ≤4h.

[0027] As a general technical concept, the present invention also provides an epoxy resin modified emulsified asphalt micro-surfacing mixture prepared by the above-described preparation method.

[0028] The cationic slow-cracking emulsified asphalt used in this invention has a further preferred solid content of 62% to 65%.

[0029] The bisphenol A type epoxy resin used in this invention has a more preferred solid content of 48% to 50%.

[0030] The aqueous epoxy resin emulsion prepared by this invention has high storage stability and a separation rate of <5% / 30d.

[0031] This invention uses aluminate cement, which can increase the early strength (24h compressive strength) of the mixture to over 3.5MPa.

[0032] Compared with the prior art, the advantages of the present invention are as follows:

[0033] (1) The preparation method of epoxy resin modified emulsified asphalt micro-surfacing mixture of the present invention addresses the problems of poor interfacial compatibility, crude asphalt-aggregate ratio design, and insufficient environmental performance in the prior art. The present invention provides a preparation method of epoxy resin modified emulsified asphalt micro-surfacing mixture, which significantly improves road performance and environmental protection through raw material system upgrade and process innovation, mainly achieving the following performance improvements:

[0034] (a) High-temperature stability (dynamic stability at 60℃ ≥ 5000 cycles / mm) improved by 150%;

[0035] (b) Low-temperature crack resistance (critical cracking temperature ≤ -25℃) decreases by 10℃;

[0036] (c) VOCs emissions (<50g / L) are reduced by 75% compared to traditional processes.

[0037] The method of this invention uses nano-silica to perform gradient temperature-activated pretreatment on the base asphalt, which reduces the interfacial activation energy between the mineral aggregate and the base asphalt by 15% to 20%, increases the interfacial bond strength of the aggregate-asphalt by 30% (pull-out strength ≥ 1.2 MPa), and increases the water stability (freeze-thaw splitting strength ratio TSR) to over 85%.

[0038] The method of this invention uses a water-based epoxy resin system to prepare a micro-surfacing mixture with VOCs < 50 g / L, which reduces emissions by more than 75% compared to solvent-based epoxy processes. It can be directly applied to damp pavements with a moisture content ≤ 8%, reducing pretreatment energy consumption by 18%. It has significant effects in emission reduction, environmental protection, energy saving, and consumption reduction. Furthermore, the construction temperature range is widened to 5℃-35℃, and the traffic opening time is ≤ 4 hours, meeting the rapid construction needs of emergency repair projects.

[0039] (2) The method of the present invention uses ethyleneamine curing agent to reduce the activation energy of the reaction with waterborne epoxy resin emulsion to 45kJ / mol-55kJ / mol, which is more than 29% lower than that of traditional amine curing (reaction activation energy of about 78kJ / mol), and can significantly increase the reaction rate (about 40%), forming a high-density three-dimensional network structure (crosslinking density 1.2×10). -3 (mol / cm³), restricting the movement of asphalt molecules, further optimizing and ensuring the dynamic stability of the micro-surfaced mixture at 60℃ is ≥5000 times / mm, improving high-temperature stability by about 150%, and significantly improving high-temperature rutting resistance; achieving complete curing within 72 hours in humid environments, and the low-temperature critical cracking temperature of the mixture is ≤-25℃, which is 10℃ lower than the traditional process.

[0040] (3) This invention develops a method for preparing epoxy resin modified emulsified asphalt based on nano-activated interface-chemical kinetic compounding-dual index optimization of asphalt-aggregate ratio, which is the key to breaking through the bottleneck of existing technology. The dual index asphalt-aggregate ratio optimization model of this invention reduces the design error by 20% compared with the traditional single index. The micro-surfacing mixture of this invention has been verified by physical engineering. Under heavy traffic conditions (design axle load of 100kN), its service life is extended by 3 to 5 years compared with the traditional micro-surfacing. It is suitable for preventive maintenance of highways, urban road overlays and road construction in ecologically sensitive areas, and has significant engineering application value and green economic benefits. Detailed Implementation

[0041] The present invention will be further described below in conjunction with the specification and specific preferred embodiments, but this does not limit the scope of protection of the present invention. In the following embodiments of the present invention, unless otherwise specified, the materials and reagents used are commercially available, and the equipment used is conventional equipment. Among them, basalt aggregate: manufactured by Shandong Zhanfei Building Materials Co., Ltd., with angularity 45%–55%, crushing value 22%–28%, and particle size divided into three grades (0–2.36mm, 2.36mm–4.75mm, and 4.75mm–9.5mm). Cationic slow-cracking emulsified asphalt: manufactured by Shanghai Songli New Material Technology Co., Ltd., model SL-MK530 (cationic slow-cracking type). Bisphenol A type epoxy resin: manufactured by Yangzi BASF Co., Ltd., model YX-828. Ethyleneamine addition-type curing agent: manufactured by Jinan Century Tongda Chemical Co., Ltd. (agent for Yangzi BASF products), model Yangzi Amix1000. Nano silica dispersion: manufactured by Zhejiang Nami New Material Co., Ltd., model NM-SiO2-20. Emulsifier: Manufacturer: Guangzhou Shuangjian Trading Co., Ltd.; Model: DS-802 (cationic). Aluminate cement: Manufacturer: Shandong Aluminum Co., Ltd.; Model: CA-50.

[0042] Example 1

[0043] This invention discloses a method for preparing epoxy resin-modified emulsified asphalt micro-surfacing mixture, comprising the following steps:

[0044] (1) Pretreatment of matrix asphalt activation: Take 72g of cationic slow-crack emulsified asphalt and put it into a heating container. The temperature is controlled according to the gradient heating process: keep it at 40℃ for 30min, 60℃ for 30min, and 80℃ for 30min. When the temperature reaches 80℃, add 1.08g of nano silica dispersion, start the high-speed shear machine, and shear at 1500r / min for 30min. After shearing, the temperature is gradually reduced to 80℃ for later use (the interfacial energy of the activated asphalt is reduced by 15%).

[0045] Frictional heat generated during high-speed shearing leads to a temperature increase, necessitating a gradient cooling process to return to 80°C. This embodiment employs gradient cooling instead of direct cooling to avoid material defects caused by sudden temperature changes. In this embodiment, the gradient cooling is 85°C → 83°C → 81°C → 80°C, with each stage held for 5-10 minutes. This ensures a uniform temperature change within the asphalt, eliminates thermal stress, and guarantees the physical stability of the asphalt.

[0046] (2) Preparation of waterborne epoxy resin emulsion: Take 40g of bisphenol A type epoxy resin, add 4.44g of emulsifier, pour into a high-speed emulsifier, set the emulsification speed to 2200r / min, the emulsification temperature to 25℃, and continue emulsification for 20min to obtain a stable waterborne epoxy resin emulsion with a particle size of 0.8μm~1.0μm and a solid content of 48% (storage stratification rate <5% / 30d).

[0047] (3) Synergistic compounding of multiphase system: Add 1000g of basalt aggregate to the mixing pot, preheat to 140℃, start the mixer at 2000r / min, add the activated matrix asphalt from step (1), and stir for 1min; slowly add the waterborne epoxy resin emulsion from step (2), and continue stirring for 1min; then add 6.4g of ethyleneamine curing agent, and stir for 2min to ensure uniform dispersion of the curing agent and avoid incomplete local reaction. Finally, add 20g of aluminate cement and 99.5g of deionized water, and stir for 1min to form a uniform micro-surfacing mixture (the total stirring time from the addition of the activated matrix asphalt should not exceed 5min to prevent premature curing).

[0048] Among them, basalt aggregate adopts AC-13C gradation, divided into three grades: 0-2.36mm, 2.36-4.75mm, and 4.75-9.5mm, with angularity of 45%, crushing value of 28%, and a dosage of 1000g.

[0049] Cationic slow-cracking emulsified asphalt: solid content 62%, charge density 130mV, calculated based on an asphalt-aggregate ratio of 7.2%, dosage is 72g;

[0050] Bisphenol A type epoxy resin: epoxy equivalent 180-200g / mol, solid content 48%, dosage 40g, which is 4% of the mass of basalt aggregate;

[0051] Emulsifier (used to prepare waterborne epoxy resin emulsion): suitable for bisphenol A type epoxy resin, calculated at a mass ratio of epoxy resin to emulsifier of 9:1, the amount is 4.44g;

[0052] Ethyleneamine addition-type curing agent: amine value 320 mg KOH / g, dosage 6.4 g, which is 16% of the epoxy resin mass;

[0053] Nano-silica dispersion: particle size 30-50nm, solid content 20%, dosage 1.08g, which is 0.3% of the mass of the base asphalt;

[0054] Aluminate cement: dosage is 20g, which is 2% of the mass of basalt aggregate;

[0055] Deionized water: accounts for 8% of the total mass of the system, and the amount used is 99.5g. The total mass of the system includes the sum of the masses of all raw materials, reagents and water.

[0056] (4) Specimen preparation

[0057] The micro-surfacing mixture obtained in step (3) was poured into a Φ150mm×50mm mold, placed in a rotary compactor, and compacted to a pressure of 600kPa and a rotation count of 100 times (the density error of the specimen is ≤1.5%). After molding, it was placed in a curing chamber at 20℃ and 60% humidity for 24 hours, and then transferred to a standard curing room (20±2℃ and 95% humidity) for 7 days.

[0058] (5) Verification and performance testing of dual-index oil-stone ratio

[0059] According to the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering", the wet tire wear (WTAT, load 1.22 kg) was tested as follows: cm -2 Wear at 500 rpm and dynamic shear rheology (DSR, 64℃, frequency 10 rad / s) confirmed a wear rate of 310 g / m. 2 The complex modulus G* = 2.7 kPa meets the dual requirements (wear loss ≤ 400 g / m²). 2 And the complex modulus G* ≥ 1.2 kPa).

[0060] The following routine performance tests were conducted, such as high temperature performance: dynamic stability at 60℃ (rutting test); low temperature performance: bending failure strain at -10℃ (BBR test), low temperature strain; water stability: freeze-thaw splitting strength ratio (TSR); abrasion resistance: wet wheel abrasion loss (WTAT), accelerated loading abrasion test (AAMT), etc. The results are detailed in Table 1.

[0061] Example 2

[0062] This invention discloses a method for preparing epoxy resin-modified emulsified asphalt micro-surfacing mixture. The raw materials and process steps are basically the same as in Example 1, except that the epoxy resin content and the amounts of the matching curing agent and emulsifier are adjusted to verify the effect of increasing the epoxy resin content on the performance of the micro-surfacing mixture, as detailed below:

[0063] Epoxy resin dosage: 50g, which is 5% of the mass of basalt aggregate;

[0064] Curing agent dosage: 8g, which is 16% of the epoxy resin mass;

[0065] Emulsifier dosage: 5.56g, the mass ratio of epoxy resin to emulsifier is 9:1;

[0066] Asphalt-aggregate ratio (mass percentage of asphalt to aggregate): 7.5%, cationic slow-cracking emulsified asphalt dosage is 75g;

[0067] Other parameters and product performance tests are the same as in Example 1.

[0068] Example 3

[0069] This invention discloses a method for preparing epoxy resin-modified emulsified asphalt micro-surfacing mixture. The raw materials and process steps are basically the same as in Example 1, except that multi-parameter synergistic optimization is performed to determine the formulation with the optimal comprehensive performance of the micro-surfacing mixture, as detailed below:

[0070] Epoxy resin dosage: 60g, which is 6% of the mass of basalt aggregate;

[0071] Curing agent dosage: 10.8g, which is 18% of the epoxy resin mass;

[0072] Aluminate cement dosage: 30g, which is 3% of the mass of basalt aggregate;

[0073] Oil-aggregate ratio: 7.8%, cationic slow-cracking emulsified asphalt dosage: 78g;

[0074] Deionized water dosage: 117.4g, accounting for 9% of the total system mass;

[0075] Other parameters and product performance tests are the same as in Example 1.

[0076] Example 4

[0077] This invention discloses a method for preparing epoxy resin-modified emulsified asphalt micro-surfacing mixture. The raw materials and process steps are basically the same as in Example 1, except that multi-parameter synergistic optimization is performed, continuing the dosage optimization trend of Example 3, to verify the high-temperature performance limit under high epoxy content, as detailed below:

[0078] Epoxy resin dosage: 70g, which is 7% of the mass of basalt aggregate;

[0079] Curing agent dosage: 13.3g, which is 19% of the epoxy resin mass;

[0080] Aluminate cement dosage: 30g, which is 3% of the mass of basalt aggregate;

[0081] Asphalt-aggregate ratio: 8.0%, cationic slow-cracking emulsified asphalt dosage: 80g;

[0082] Deionized water dosage: 133.6g, accounting for 10% of the total system mass;

[0083] Other parameters and product performance tests are the same as in Example 1.

[0084] Example 5

[0085] An epoxy resin-modified emulsified asphalt micro-surfacing mixture uses the same raw materials as in Example 1, but with the difference that multi-parameter synergistic optimization was performed, continuing the dosage optimization trend of Example 3, to verify the performance stability of the upper limit of the formulation, as detailed below:

[0086] Epoxy resin dosage: 80g, which is 8% of the mass of basalt aggregate;

[0087] Curing agent dosage: 16g, which is 20% of the epoxy resin mass;

[0088] Aluminate cement dosage: 40g, which is 4% of the mass of basalt aggregate;

[0089] Oil-aggregate ratio: 8.3%, cationic slow-cracking emulsified asphalt dosage: 83g;

[0090] Deionized water dosage: 136.6g, accounting for 10% of the total system mass;

[0091] Other parameters and product performance tests are the same as in Example 1.

[0092] Example 6

[0093] An epoxy resin modified emulsified asphalt micro-surfacing mixture is provided. The raw materials and dosages are basically the same as those in Example 3. The only difference is that the aggregate gradation is replaced to verify the anti-skid and water tightness performance of the fine gradation.

[0094] The basalt aggregate used in this implementation has the following gradation: MS-2, nominal maximum particle size 4.75mm, with a gradation ratio of 60% for 0-2.36mm and 40% for 2.36-4.75mm.

[0095] Example 7

[0096] An epoxy resin modified emulsified asphalt micro-surfacing mixture is provided. The raw materials and dosages are basically the same as those in Example 3. The only difference is that the aggregate gradation is replaced to verify the comprehensive performance of the medium-coarse gradation.

[0097] The basalt aggregate used in this implementation has the following gradation: MS-3, nominal maximum particle size 9.5mm, with the following proportions: 0-2.36mm accounting for 40%, 2.36-4.75mm accounting for 30%, and 4.75-9.5mm accounting for 30%.

[0098] Example 8

[0099] An epoxy resin modified emulsified asphalt micro-surfacing mixture is provided. The raw materials and dosages are basically the same as those in Example 3. The only difference is that the aggregate gradation is replaced and the asphalt-aggregate ratio is adjusted to 8.0% (to match the coarse gradation) to verify the high anti-skid performance of the coarse gradation.

[0100] The basalt aggregate used in this implementation has the following gradation: MS-4, nominal maximum particle size 13.2mm, with the following proportions: 0-2.36mm accounting for 30%, 2.36-4.75mm accounting for 30%, and 4.75-13.2mm accounting for 40%.

[0101] Example 9

[0102] An epoxy resin modified emulsified asphalt micro-surfacing mixture is provided. The raw materials and dosages are basically the same as those in Example 3. The only difference is that the pretreatment process is enhanced to adapt to humid environments.

[0103] Environmental conditions for this implementation: substrate moisture content 8% (damp condition);

[0104] The pretreatment process implemented in this case involves increasing the dosage of nano-silica dispersion to 0.5% of the matrix asphalt mass, increasing the shear speed to 2000 r / min, and extending the activation time to 40 min.

[0105] Example 10

[0106] An epoxy resin modified emulsified asphalt micro-surfacing mixture is provided. The raw materials and dosages are basically the same as those in Example 3. The only difference is that the pretreatment temperature and initial curing temperature and duration are adjusted to adapt to low-temperature construction.

[0107] Environmental conditions for this implementation: Construction temperature 5℃ (cold regions);

[0108] The process adjustments implemented in this case are as follows: the gradient temperature increase of the base asphalt is changed to 50℃→70℃→90℃ (to adapt to low-temperature activation), the initial temperature of the specimen is controlled at 15℃, and the curing time is extended to 48h. That is, after molding, it is placed in a curing box at 15℃ and 60% humidity for 48h, and then transferred to a standard curing room (20±2℃, 95% humidity) for 7d.

[0109] The formulation parameters and performance test results of Examples 1-10 are shown in Tables 1 to 3 below. Among them, Examples 1 to 5 mainly focused on optimizing the epoxy resin content, and the results are shown in Table 1.

[0110] Table 1 - Formulation parameters and performance test results of Examples 1 to 5

[0111]

[0112] As shown in Table 1, the epoxy resin content is 6%-8%, which results in the best overall performance in terms of high-temperature stability and low-temperature crack resistance.

[0113] Examples 1-5 use epoxy resin content as the independent variable and curing agent content, cement content, and asphalt-aggregate ratio as dependent variables. These values ​​increase accordingly with increasing epoxy resin content. If the cement content and asphalt-aggregate ratio remain constant, the product performance data will be adversely affected, thus failing to reflect the impact of changes in epoxy resin content on product performance. Specifically:

[0114] (1) Increased cement content: synergistic effect of hydration and strength in epoxy system

[0115] To adapt to the hydration and strength of the epoxy system, the cement content is appropriately increased along with the epoxy resin content. Epoxy resin is a rigid modifier, and increasing its content slightly increases the brittleness of the mixture. Therefore, the cement (hydration cementitious material) needs to be increased simultaneously: on the one hand, to replenish the hydration products (ettringite, CSH gel) to fill the micropores after epoxy cross-linking, improving density; on the other hand, to alleviate the brittleness of the epoxy through the flexible hydration film of the cement, preventing low-temperature cracking. In this invention, the epoxy resin content is increased from 4% to 8%, and the cement content from 2% to 4%, representing a synergistic design of "rigid modification + flexible compensation."

[0116] (2) Increased oil-stone ratio: ensures coating and bonding of multiphase systems

[0117] Increasing the epoxy content will increase the overall viscosity of the mixture, requiring more activated matrix asphalt. Therefore, the asphalt-aggregate ratio is increased from 7.2% to 8.3% accordingly: firstly, to reduce the viscosity of the system, allowing the asphalt-epoxy emulsion to evenly coat the aggregate surface (avoiding "drying and clumping"); secondly, to supplement the bonding properties of the asphalt, balance the rigidity of the epoxy, and ensure that the mixture has both high-temperature rutting resistance and low-temperature crack resistance.

[0118] Examples 6 to 8 mainly focused on optimizing the gradation of mineral aggregates, and the results are shown in Table 2:

[0119] Table 2 - Formulation parameters and performance test results of Examples 6 to 8

[0120]

[0121] As shown in Table 2, MS-3 gradation has both excellent anti-skid performance (slip value) and water tightness (permeability coefficient), making it suitable for high-grade roads.

[0122] Examples 9 and 10 mainly improve the adaptability of micro-surfaced mixtures to special environments by changing the pretreatment process conditions and curing conditions.

[0123] Table 3 - Formulation parameters and performance test results of Examples 9 and 10

[0124]

[0125] A comparison of the data in Table 3 and Table 2 shows that nano-activation pretreatment can significantly improve adaptability to humid environments, and gradient heating process can improve low-temperature construction performance.

[0126] Comparing Examples 7 and 9, Example 7, applied to a conventional substrate, had a traffic open time of 4.5 hours and a WTAT of 330 g / m² after freeze-thaw cycles. Example 9, applied to a damp substrate, significantly improved the adhesion stability of the damp substrate by increasing the amount of nano-silica dispersion, increasing the shear speed, and extending the shear time, reducing the traffic open time to 3.5 hours and achieving a WTAT of 310 g / m² after freeze-thaw cycles. The water stability after freeze-thaw cycles still met the standards. Here, water stability was evaluated using the freeze-thaw splitting strength ratio (TSR) and wet wheel abrasion (WTAT) after freeze-thaw cycles, with the standards being TSR ≥ 85% and WTAT ≤ 400 g / m², respectively. Considering the traffic open time and WTAT values ​​after freeze-thaw cycles, Example 9 performed slightly better on a damp substrate than Example 7 on a conventional substrate, indicating that the reinforced matrix asphalt pretreatment process has strong adaptability to damp substrates.

[0127] Compared to Example 7, which showed some performance degradation in cold environments, Example 10, by increasing the gradient heating temperature of the base asphalt pretreatment, reducing the initial curing temperature, and extending the curing time, can enhance the low-temperature crack resistance and early strength of the micro-surfaced mixture in cold regions, meeting the winter construction requirements with a 4.0-hour traffic opening time. Here, the low-temperature crack resistance is evaluated using the critical cracking temperature and 5℃ construction strength as the core indicators, and the -10℃ low-temperature strain (BBR flexural failure strain) as an auxiliary indicator. The standards are a critical cracking temperature ≤ -25℃ and a low-temperature strain ≥ 2800με, respectively. Example 10 not only meets these standards but also outperforms Example 7 in terms of traffic opening time, critical cracking temperature, and 5℃ construction strength.

[0128] As can be seen from Examples 9 and 10, by controlling the pretreatment process conditions and curing conditions, the micro-surfacing mixture prepared by the present invention can be directly applied to wet pavements with a moisture content of ≤8%, and can be applied in a construction temperature range of 5℃-35℃ with a traffic opening time of ≤4h, meeting the rapid construction needs of emergency repair projects.

[0129] Comparative Example 1

[0130] A method for preparing a conventional micro-surfacing mixture, compared with Example 1, uses an anhydrous epoxy resin emulsion and the base asphalt does not undergo activation pretreatment. The preparation steps include:

[0131] (1) Base asphalt insulation for later use

[0132] Take 75g of cationic slow-cracking emulsified asphalt and place it in an 80℃ constant temperature container for later use.

[0133] (2) Traditional compounding of feedstocks:

[0134] Add 1000g of basalt aggregate to the mixing pot, preheat to 140℃, start the mixer at 2000r / min; pour in the heat-insulated cationic slow-cracking emulsified asphalt, and continue mixing for 2 minutes to ensure that the aggregate and asphalt are initially coated.

[0135] Add 20g of aluminate cement and 95.2g of deionized water, and continue stirring for 1 minute to form a uniform traditional micro-surfacing mixture (total stirring time 3 minutes, without any modified components).

[0136] Among them, basalt aggregate adopts AC-13C gradation, divided into three grades: 0-2.36mm, 2.36-4.75mm, and 4.75-9.5mm, with angularity of 45%, crushing value of 28%, and dosage of 1000g.

[0137] Cationic slow-cracking emulsified asphalt: solid content 62%, charge density 130mV, calculated based on an asphalt-aggregate ratio of 7.5%, dosage 75g;

[0138] Aluminate cement: 2% of the basalt aggregate mass, 20g in dosage;

[0139] Deionized water: accounts for 8% of the total mass of the system. The total mass of the system is 1000g + 75g + 20g + 95.2g = 1190.2g, corresponding to a water consumption of approximately 95.2g.

[0140] The specimen preparation and performance testing were the same as in Example 1, and the results are shown in Table 4.

[0141] Comparative Example 2

[0142] A method for preparing a conventional micro-surfacing mixture, compared with Example 1, uses a solvent-based epoxy resin system instead of an aqueous epoxy resin emulsion, and the base asphalt does not undergo activation pretreatment. The preparation steps include:

[0143] (1) Base asphalt insulation for later use

[0144] Take 78g of cationic slow-cracking emulsified asphalt and place it in an 80℃ constant temperature container for later use.

[0145] (2) Preparation of solvent-based epoxy system (replacing waterborne epoxy resin emulsion)

[0146] Take 50g of solvent-based bisphenol A epoxy resin, add 15g of xylene solvent, place in a mixing container, and stir at 1500r / min for 5min at 25℃. Dilute the epoxy resin to a viscosity ≤500mPa. s, to facilitate subsequent mixing;

[0147] Add 15g of amine curing agent to epoxy resin at a mass ratio of 10:3, and continue stirring for 3 minutes to obtain a solvent-based epoxy-curing agent mixture (to be used within 30 minutes to avoid solvent evaporation affecting performance).

[0148] (3) Mixture compounding

[0149] Add 1000g of basalt aggregate to the mixing pot, preheat to 140℃, start the mixer at 2000r / min; pour in the heat-insulated emulsified asphalt, stir for 1min to allow the aggregate to initially coat the asphalt; slowly pour in the prepared solvent-based epoxy-curing agent mixture, stir continuously for 2min to ensure uniform dispersion of the solvent and epoxy system and avoid local residues; add 20g of aluminate cement and 102.4g of deionized water, stir for 1min to form a solvent-based epoxy modified micro-surfacing mixture.

[0150] (4) Specimen preparation

[0151] Pour the mixture into a Φ150mm×50mm mold and compact it using a rotary compactor (pressure 600kPa, rotation 100 times). After molding, place it in a well-ventilated curing environment (20℃, humidity 60%) for 24 hours (to eliminate VOCs generated by solvent evaporation), and then transfer it to a standard curing room for 7 days.

[0152] Among them, basalt aggregate: AC-13C gradation, angularity 45%, crushing value 28%, dosage 1000g;

[0153] Cationic slow-cracking emulsified asphalt: solid content 62%, charge density 130mV, calculated based on an asphalt-aggregate ratio of 7.8%, dosage 78g;

[0154] Solvent-based bisphenol A type epoxy resin: epoxy equivalent 180-200g / mol, it is an emulsified solvent-based resin, accounting for 5% of the mass of basalt aggregate, with a dosage of 50g;

[0155] Amine curing agent: Conventional aliphatic amine curing agent (non-ethyleneamine type), mixed at 30% of epoxy resin mass, dosage 15g;

[0156] Xylene solvent: analytical grade, used to dilute epoxy resin, at a ratio of 30% of epoxy resin mass, with a dosage of 15g.

[0157] Aluminate cement: 2% of the mass of basalt aggregate, 20g;

[0158] Deionized water accounts for 8% of the total mass of the system. The total mass of the system is 1000g + 78g + 50g + 15g + 15g + 20g + 102.4g = 1280.4g, corresponding to a water consumption of approximately 102.4g.

[0159] The performance test was the same as in Example 1, and the results are shown in Table 4.

[0160] Comparative Example 3

[0161] A method for preparing a conventional micro-surfacing mixture, compared with Example 3, differs mainly in that it uses unactivated asphalt instead of activated pretreated matrix asphalt. The specific preparation steps include:

[0162] (1) Cationic slow-cracking emulsified asphalt for insulation and standby

[0163] Take 78g of cationic slow-cracking emulsified asphalt and place it directly into a heating container to heat to 80℃ and keep it warm for later use.

[0164] (2) The preparation of the waterborne epoxy resin emulsion is the same as in Example 1.

[0165] (3) Multiphase system compounding, the same as in Example 1.

[0166] Among them, the basalt aggregate is AC-13C graded, with angularity of 45%, crushing value of 28%, and dosage of 1000g.

[0167] Cationic slow-cracking emulsified asphalt: solid content 62%, charge density 130mV, calculated based on an asphalt-aggregate ratio of 7.8%, dosage 78g;

[0168] Bisphenol A type epoxy resin: epoxy equivalent 180-200g / mol, solid content 48%, which is 6% of the mass of basalt aggregate, dosage 60g;

[0169] Ethyleneamine addition curing agent: amine value 320mgKOH / g, dosage 10.8g based on 18% of epoxy resin mass;

[0170] Aluminate cement: 3% of the mass of basalt aggregate, 30g in dosage;

[0171] Emulsifier (used in the preparation of waterborne epoxy resin emulsion): 6.7g based on a mass ratio of epoxy resin to emulsifier of 9:1.

[0172] Deionized water: accounts for 9% of the total mass of the system. The total mass of the system is 1000g + 78g + 60g + 10.8g + 30g + 6.7g + 117.3g = 1302.8g, corresponding to a water consumption of approximately 117.3g.

[0173] The specimen preparation and performance testing were the same as in Example 1, and the results are shown in Table 4.

[0174] Table 4 - Formulation parameters and performance test results of the comparative examples

[0175]

[0176] A comparison of the data in Table 4 and Table 1 shows that, compared with Comparative Example 1, Example 3 of the present invention improves high-temperature performance by 170% with dynamic stability at 60℃ as the evaluation index, and improves low-temperature strain by 33% with low-temperature strain at -10℃ as the evaluation index.

[0177] Compared with the solvent-based system in Comparative Example 2, the aqueous system in Example 3 has significantly improved environmental friendliness (VOCs < 50 g / L vs 180 g / L).

[0178] In Example 3, the micro-surfaced mixture prepared after pretreatment of the base asphalt showed a 7% improvement in water stability compared to the micro-surfaced mixture prepared without pretreatment in Comparative Example 3, using the freeze-thaw splitting strength ratio (TSR%) as the evaluation index.

[0179] In traditional processes, improving water stability from "acceptable" (TSR=85%) to "excellent" (TSR≥90%) typically requires a combination of adding anti-stripping agents and increasing the amount of binder. This not only increases costs by 10%-15% but may also lead to high-temperature performance degradation (a 5%-8% decrease in dynamic stability). However, Example 3 achieves a 7% improvement through process optimization without compromising other properties (dynamic stability and low-temperature strain remain optimal). This "low-cost, synergistic performance improvement" is extremely rare in the field.

[0180] Key process parameter verification

[0181] Effect of nano-silica pretreatment: Scanning electron microscopy (SEM) was used to observe the interfacial microstructure. The thickness of the asphalt-aggregate interface transition zone in Example 3 reached 30 μm–50 μm, significantly enhanced compared to the 15 μm–25 μm thickness in Comparative Example 3. This demonstrates that nano-silica pretreatment can construct a "strongly bonded, high-density" interfacial layer, simultaneously improving the bonding strength, water stability, and durability of the micro-surfaced mixture at the microscopic level.

[0182] Curing reaction kinetics: Differential scanning calorimetry (DSC) was used to test the curing reaction activation energy of Example 4, which was 52 kJ / mol, a decrease of 33% compared with the conventional amine curing of Comparative Example 2 (78 kJ / mol), and the reaction rate was increased by 40%.

[0183] Determining the optimal oil-stone ratio

[0184] The optimal oil-aggregate ratio of 7.8% is derived based on the "wet wheel wear (WTAT) + dynamic shear rheology (DSR) dual-index optimization model" of this invention. The core is determined by using Example 3 (MS-3 gradation, waterborne epoxy system) as a benchmark, through a closed-loop process of "gradient setting → dual index testing → threshold matching", while verifying its rationality by comparing with the traditional single index method.

[0185] Based on the data of DSR complex shear modulus and DSR phase angle δ in Examples 1 to 5, it can be seen that...

[0186] (1) With an asphalt-aggregate ratio of 7.8%, WTAT = 270 g / m² (≤300 g / m²) and G* = 3.2 kPa (≥2.8 kPa) meet the basic requirements for water stability and rutting resistance, and exclude the 7.2% that does not meet the standards;

[0187] (2) The WTAT of the standard asphalt-aggregate ratios of 7.5%, 7.8%, 8.0%, 8.3%, and 7.8% is the minimum value of the whole gradient (270g / m², which is 8.5% lower than that of the asphalt-aggregate ratio of 7.5%), the G* of DSR is the maximum value of the whole gradient (3.2kPa, which is 6.7% higher than that of the asphalt-aggregate ratio of 7.5%), and the phase angle δ is the smallest (38°, which is the strongest in terms of resistance to deformation).

[0188] (3) The asphalt-aggregate ratios of 8.0% and 8.3% are higher (the amount of base asphalt used increases), but WTAT and G* decrease instead, which is neither economical nor efficient. Therefore, 7.8% is the optimal ratio.

[0189] To verify the rationality of 7.8%, a comparison with the traditional single-index method (measuring only WTAT) was added: the single-index method also measured the minimum WTAT value (310 g / m²) at an oil-stone ratio of 7.8%. Since Comparative Example 2 is a solvent-based epoxy system, the absolute value of WTAT is higher than that of Example 3. However, the failure to measure DSR resulted in a shortcoming in high-temperature performance (dynamic stability of only 4200 cycles / mm, far lower than the 5680 cycles / mm of Example 3).

[0190] For example, in Example 3, the optimal oil-stone ratio of 7.8% was determined according to the dual index method. Although the oil-stone ratio of Comparative Example 2 was also 7.8%, it only met the single index method. Compared with Comparative Example 2, Example 3 improved dynamic stability by 35% and low-temperature strain by 16%.

[0191] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention, or modify them into equivalent embodiments, without departing from the spirit and technical essence of the invention. Therefore, any simple modifications, equivalent substitutions, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the content of the present invention, shall still fall within the scope of protection of the present invention.

Claims

1. A method for preparing an epoxy resin-modified emulsified asphalt micro-surfacing mixture, characterized in that, Includes the following steps: (1) Activation pretreatment of matrix asphalt: The matrix asphalt is heated in a gradient. First, it is heated to 35℃~50℃ and kept at that temperature. Then, it is heated to 55℃~70℃ and kept at that temperature. Then, it is heated to 75℃~90℃. Nano silica is added and stirred and sheared to obtain activated matrix asphalt. (2) Preparation of waterborne epoxy resin emulsion: Waterborne epoxy resin emulsion with a solid content of 45% to 50% was prepared by phase inversion method, and the mass ratio of epoxy resin to emulsifier was controlled to be 8 to 10:1 to form a stable dispersion system with a particle size ≤1μm. (3) Synergistic compounding of multiphase system: preheat the mineral aggregate, add the activated matrix asphalt from step (1) while stirring, and continue stirring; add the waterborne epoxy resin emulsion from step (2) and continue stirring; then add the ethyleneamine curing agent and continue stirring to ensure that the curing agent is evenly dispersed and to avoid incomplete local reaction; finally add cement and water and continue stirring to form a uniform micro-surfaced mixture.

2. The method for preparing epoxy resin modified emulsified asphalt micro-surfacing mixture according to claim 1, characterized in that, The nano-silica is a nano-silica dispersion with a solid content of 15%–25%, and is used at a rate of 0.2%–0.5% of the mass of the base asphalt, with a particle size of 20nm–50nm; the mass ratio of the base asphalt to the mineral aggregate is 6%–10%; the mass ratio of the epoxy resin to the mineral aggregate is 4%–8%; the amount of the curing agent is 15%–20% of the mass of the epoxy resin; the amount of cement is 2%–4% of the mass of the mineral aggregate; and the amount of water accounts for 8%–12% of the total mass of the system.

3. The method for preparing epoxy resin modified emulsified asphalt micro-surfacing mixture according to claim 1, characterized in that, In step (1), the heat preservation time is 20 min to 40 min; the stirring and shearing speed is 1200 r / min to 2000 r / min, and the stirring and shearing time is 20 min to 40 min; during the stirring and shearing process, the nano silica and the matrix asphalt mixture heat up due to friction, and after shearing, the temperature is gradually reduced to 75℃ to 90℃, with a temperature reduction of 1.5℃ to 2.5℃ in each stage, and the heat preservation time is 5 min to 10 min in each stage.

4. The method for preparing epoxy resin modified emulsified asphalt micro-surfacing mixture according to claim 1, characterized in that, In step (2), the phase inversion method involves mixing epoxy resin with an emulsifier and emulsifying it at a speed of 2000 r / min to 2500 r / min for 15 min to 25 min. In step (3), the mineral aggregate is preheated to a temperature of 135℃~145℃, the stirring speed is 1800r / min~2200r / min, and the total stirring time from the addition of the activated matrix asphalt does not exceed 5min.

5. The method for preparing epoxy resin modified emulsified asphalt micro-surfacing mixture according to claim 1, characterized in that, The mineral aggregate is basalt mineral aggregate with angularity ≥45%, crushing value ≤28%, and gradation conforming to AC-13C, MS-2, MS-3 or MS-4 standards. The base asphalt is a cationic slow-cracking emulsified asphalt with a solid content ≥62% and a charge density of 120mV~150mV; The epoxy resin is a bisphenol A type epoxy resin with an epoxy equivalent of 180 g / mol to 200 g / mol. The curing agent is an ethyleneamine addition-type curing agent with an amine value of 300 mgKOH / g to 350 mgKOH / g; The cement is aluminate cement.

6. The method for preparing epoxy resin modified emulsified asphalt micro-surfacing mixture according to claim 1, characterized in that, By measuring the wet wheel abrasion and dynamic shear rheology of micro-surfaced mixture specimens, a dual-index evaluation model of abrasion amount and complex modulus G* was established to determine the optimal asphalt-aggregate ratio. The load for the wet wheel abrasion test was 1.22 kg. cm -2 The wear rate was 500 revolutions, and the dynamic shear rheological test temperature was 64℃ with a frequency of 10 rad / s. It was found that when the wear rate is ≤400 g / m³, the wear rate is suitable for the following conditions: 2 Furthermore, the complex modulus G* ≥ 1.2 kPa corresponds to the optimal oilstone ratio.

7. The method for preparing the epoxy resin modified emulsified asphalt micro-surfacing mixture according to claim 6, characterized in that, The optimal oilstone ratio is 6.5% to 8.5%, and the density error of the micro-surfaced mixture specimen is ≤1.5% to ensure that the repeatability accuracy of the test data meets the requirements of ASTM D6933 standard.

8. The method for preparing epoxy resin modified emulsified asphalt micro-surfacing mixture according to claim 6, characterized in that, The road performance of the micro-surfaced mixture prepared with the optimal asphalt-aggregate ratio was verified through a three-level performance evaluation. The evaluation indicators for the three-level performance were stiffness modulus ≤300MPa, freeze-thaw splitting strength ratio ≥85%, and accelerated loading abrasion loss ≤120g / m. 2 .

9. The method for preparing epoxy resin modified emulsified asphalt micro-surfacing mixture according to any one of claims 1 to 8, characterized in that, The construction temperature range of the micro-surfacing mixture is 5℃~35℃, and the opening time for traffic is ≤4h.

10. An epoxy resin modified emulsified asphalt micro-surfacing mixture prepared by the preparation method according to any one of claims 1 to 9.

Images