A kind of emulsified asphalt cold recycled mixture with high early strength and preparation method thereof

Abstract

The present invention relates to the technical field of asphalt road materials, and specifically to a high early strength emulsified asphalt cold recycled mixture and a preparation method thereof, wherein the mixture is composed of the following components, by weight: 3.2 to 4.5 parts of emulsified asphalt, 75 to 85 parts of waste asphalt mixture, 5 to 8 parts of new aggregate, 0.5 to 3.0 parts of mineral powder, 0.5 to 2.5 parts of cement, 2.5 to 5 parts of water, and 5 to 35 parts of pretreated steel slag. The present invention also discloses a method for treating the pretreated steel slag and a preparation method of the mixture. The high early strength emulsified asphalt cold recycled mixture of the present invention uses pretreated steel slag to solve the problem that the steel slag expands when exposed to water and affects the road performance of the mixture, and can also consume waste solid and waste steel slag to achieve the purpose of resource recycling, and accelerates the emulsified asphalt demulsification by heating with a microwave transmitter to achieve the purpose of improving the early strength of the mixture.

Description

Technical Field

[0001] The invention relates to the technical field of asphalt road materials, and in particular to an emulsified asphalt cold recycled mixture with high early strength and a preparation method thereof. Background Art

[0002] my country's road construction is accelerating, the road network density is increasing, and the road traffic function is constantly improving. A large number of early-built roads need to be maintained, repaired or rebuilt. The design service life of asphalt pavement is generally 8 to 15 years. From now on, about 10% of asphalt pavement will enter the maintenance or reconstruction cycle every year. According to statistics, my country produces tens of millions of tons of waste asphalt pavement materials every year. In Beijing alone, about 1 million to 1.5 million tons of waste asphalt pavement materials are produced every year. If the waste asphalt pavement materials are abandoned, it will not only occupy a large amount of land, but also cause waste of resources and environmental pollution.

[0003] There are two main technical approaches for the recycling of old asphalt pavement materials: one is the hot recycling technology with the main purpose of restoring the performance of old asphalt, and the other is the cold recycling technology that simply realizes the recycling of old asphalt materials. Cold recycling has strong technical advantages, can be deeply processed, does not require energy consumption to dry the milling materials, has good adaptability to the environment, saves resources, reduces production costs, reduces energy consumption, speeds up construction progress, and protects the ecological environment to the greatest extent.

[0004] However, compared with hot-mix asphalt mixture, the final strength of emulsified asphalt cold recycled mixture requires emulsified asphalt to demulsify and condense, and cement to hydrate, and this process takes a certain amount of time. Under normal conditions, the emulsified asphalt demulsifies slowly. The early strength of the emulsified asphalt mixture after rolling mainly depends on the interlocking effect between aggregates. In addition, the mixture contains more water in the early stage of construction, which affects the bonding effect of asphalt on aggregates, resulting in slow strength formation of asphalt mixture, which seriously affects the time of opening traffic and construction progress. Especially in urban roads, it is often required to open traffic quickly on the same day. At this time, the strength of the emulsified asphalt cold recycled layer has not been fully formed. Under the influence of construction vehicles and temporary traffic, it faces the risk of loose road surface and other hazards. Especially for megacities such as Beijing, it is urgent to solve the current situation of insufficient early strength, slow construction progress, and long-term traffic blocking in the construction of emulsified asphalt cold recycled technology.

[0005] At present, the early strength of emulsified asphalt cold recycled mixture is generally improved by adding early-strength cement or various demulsifiers, water reducers, etc. However, the addition of early-strength cement will increase the project cost on the one hand, and affect the fatigue resistance of the mixture on the other hand. The addition of various demulsifiers, water reducers, etc., on the one hand, has a complicated preparation process and is not suitable for engineering applications, and on the other hand, it will also increase the project cost.

[0006] Industrial steel slag has been growing exponentially with the expansion of urban construction and various industries. Large-scale stockpiling not only occupies land, but also pollutes the environment. Using it as a new type of road material in highway construction can achieve efficient resource allocation and effectively save energy, making steel slag no longer a solid waste, but a valuable resource. Summary of the invention

[0007] The purpose of the present invention is to provide an emulsified asphalt cold recycled mixture with high early strength, which can not only absorb industrial solid waste steel slag to achieve the purpose of resource recycling, but also effectively improve the early strength of the emulsified asphalt cold recycled mixture.

[0008] At the same time, the present invention also provides a method for preparing the mixture.

[0009] The mixture adopts the following technical solutions:

[0010] A high early strength emulsified asphalt cold recycled mixture, comprising the following components in parts by weight:

[0011] 3.2-4.5 parts of emulsified asphalt, 75-85 parts of waste asphalt mixture, 5-8 parts of new aggregate, 0.5-3.0 parts of mineral powder, 0.5-2.5 parts of cement, 2.5-5 parts of water, and 5-35 parts of pretreated steel slag.

[0012] Preferred ingredients: 3.2-4.0 parts of emulsified asphalt, 75-80 parts of waste asphalt mixture, 5-8 parts of new aggregate, 0.5-1.0 parts of mineral powder, 0.5-1.2 parts of cement, 3.0-4.0 parts of water, and 15-20 parts of pretreated steel slag.

[0013] The emulsified asphalt is a slow-cracking cationic emulsified asphalt or a slow-cracking cationic modified emulsified asphalt, wherein the slow-cracking cationic modified emulsified asphalt refers to SBS modified or SBR modified, and the residual solid content is ≥62%.

[0014] The waste asphalt mixture is composed of the following parts by weight of waste recycled particles: 62 to 75 parts of particles with a particle size of 0 to 10 mm, and 10 to 20 parts of particles with a particle size of 10 to 25 mm. The sand equivalent of fine milling materials with particles of 0 to 4.75 mm has a great influence on the coating effect of emulsified asphalt and aggregate, and the sand equivalent of fine milling materials with particles of 0 to 4.75 mm is required to be greater than 80%.

[0015] The new aggregate is conventional asphalt mixture aggregate, but is not limited thereto, and has a particle size of 10 to 25 mm.

[0016] The mineral powder is a mineral powder for asphalt mixture, and the content of inorganic substances such as active calcium, silicon, and aluminum is greater than 32%;

[0017] The cement is various types of conventional cement for asphalt mixture;

[0018] The steel slag is electric furnace steel slag or converter steel slag, wherein the calcium oxide content is ≤3%, the magnesium oxide content is 3-10%, the manganese oxide content is 1-3%, the iron content is ≤2%, the water expansion rate is ≤2%, the maximum particle size is ≤31.5mm, and the crushing value is ≤30%.

[0019] The pretreatment method is one of the following two methods: first, completely immerse the steel slag in water for 10 to 24 hours, then take out the steel slag and put it into a 100°C oven for drying or naturally drying to obtain pretreated steel slag. The standard for drying or drying is that the same amount of steel slag is weighed at intervals of 30 minutes, and the mass difference is ≤0.5%. The purpose of this method is to hydrate the calcium oxide, magnesium oxide, etc. in the steel slag before the mixture is mixed, so that the volume of the steel slag is fully expanded, and the volume expansion probability of the steel slag during the mixing process of the mixture is reduced, thereby ensuring the use performance of the mixture; second, cement slurry is added to the steel slag for stirring until the surface of the steel slag is completely covered with the mixed slurry, the weight ratio of the slurry to the steel slag is 1 to 2.5:5 to 7.5, and the pretreated steel slag is obtained. The cement slurry is a mixture of cement, mineral powder and water, and the weight ratio is 1:2-4:4-5. Filling the gaps on the surface of the steel slag with this mixed slurry can reduce the probability of the steel slag contacting water, hinder its expansion, and ensure the use performance of the mixture.

[0020] The present invention also provides a method for preparing the above-mentioned emulsified asphalt cold recycled mixture with high early strength, comprising the following steps:

[0021] (1) The waste asphalt mixture, new aggregate, mineral powder, cement, and pre-treated steel slag in the above-mentioned weight parts are fully stirred, and water is added to fully stir and mix for 40 to 60 seconds;

[0022] (2) adding emulsified asphalt to the mixture in step (1) and stirring thoroughly for 60s to 90s;

[0023] (3) The mixture in step (2) is treated with a microwave transmitter for 5 to 15 minutes to obtain an emulsified asphalt cold recycled mixture with high early strength.

[0024] The microwave transmitter is a closed device with unlimited size and an output power of 500-2000W.

[0025] The beneficial effects of the present invention are as follows: adding solid waste steel slag can not only achieve the purpose of recycling waste resources, but also utilize the metal elements contained therein to improve the effect of microwave heating to accelerate the demulsification of emulsified asphalt, improve the early strength of the emulsified asphalt cold recycled mixture, and improve the mechanical properties of the mixture; in this method, the steel slag has been pretreated, which can effectively avoid the problem of steel slag swelling in water during use and affecting road performance. The emulsified asphalt cold recycled mixture prepared by this method, after microwave emission treatment, the splitting strength of the formed mixture specimen can reach more than 0.5MPa without curing, which is higher than the strength of the conventionally cured emulsified asphalt cold recycled mixture. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail in the following specific implementation modes.

[0027] Example 1

[0028] A high early strength emulsified asphalt cold recycled mixture, the raw materials of which include the following components: 3.5 parts of emulsified asphalt, 78 parts of waste asphalt mixture, 6 parts of new aggregate, 0.5 parts of mineral powder, 0.5 parts of cement, 3.2 parts of water, and 15 parts of pretreated steel slag, wherein the emulsified asphalt is a cationic slow-cracking emulsified asphalt, the waste asphalt mixture is composed of the following parts by weight of waste particles, 68 parts of particles with a particle size of 0-10 mm, of which the fine milling sand equivalent of 0-4.75 mm particles is 85%, 13 parts of particles with a particle size of 10-25 mm, the steel slag is ordinary converter steel slag, and the pretreatment step is to completely immerse the steel slag in water for 12 hours, then fish out the steel slag and put it into a 100°C oven for drying to obtain the pretreated steel slag.

[0029] The method for preparing the above-mentioned high early strength emulsified asphalt cold recycled mixture comprises the following steps:

[0030] (1) The above-mentioned waste asphalt mixture, new aggregate, mineral powder, cement, and pre-treated steel slag are fully stirred, and water is added to mix them for 45 seconds;

[0031] (2) adding emulsified asphalt to the mixture in step (1) and mixing thoroughly for 60 seconds;

[0032] (3) The mixture in step (2) is treated with a microwave emitter for 5 minutes to obtain an emulsified asphalt cold recycled mixture with high early strength.

[0033] The output power of the above microwave transmitter is 800W.

[0034] Example 2

[0035] A high early strength emulsified asphalt cold recycled mixture, the raw materials of which include the following components: 3.8 parts of emulsified asphalt, 80 parts of waste asphalt mixture, 5 parts of new aggregate, 0.5 parts of mineral powder, 1.0 parts of cement, 3.5 parts of water, and 20 parts of pretreated steel slag, wherein the emulsified asphalt is a cationic slow-cracking emulsified asphalt, the waste asphalt mixture is composed of the following parts by weight of waste particles, 70 parts of particles with a particle size of 0 to 10 mm, of which the fine milling sand equivalent of 0 to 4.75 mm particles is 83%, 18 parts of particles with a particle size of 10 to 25 mm, the steel slag is ordinary electric furnace steel slag, and the pretreatment step is to completely immerse the steel slag in water for 15 hours, then fish out the steel slag and dry it naturally to obtain the pretreated steel slag.

[0036] The method for preparing the above-mentioned high early strength emulsified asphalt cold recycled mixture comprises the following steps:

[0037] (1) The above-mentioned waste asphalt mixture, new aggregate, mineral powder, cement, and pre-treated steel slag are fully stirred, and water is added to mix them for 40 seconds;

[0038] (2) adding emulsified asphalt to the mixture in step (1) and mixing thoroughly for 60 seconds;

[0039] (3) The mixture in step (2) is treated with a microwave emitter for 5 minutes to obtain an emulsified asphalt cold recycled mixture with high early strength.

[0040] The output power of the above microwave transmitter is 1200W.

[0041] Example 3

[0042] A high early strength emulsified asphalt cold recycled mixture, the raw materials of which include the following components: 4.0 parts of emulsified asphalt, 76 parts of waste asphalt mixture, 8 parts of new aggregate, 0.8 parts of mineral powder, 0.5 parts of cement, 3.8 parts of water, and 18 parts of pretreated steel slag, wherein the emulsified asphalt is a cationic slow-cracking emulsified asphalt, the waste asphalt mixture is composed of the following parts by weight of waste particles, 72 parts of particles with a particle size of 0-10 mm, wherein the fine milling sand equivalent of particles with a particle size of 0-4.75 mm is 86%, 12 parts of particles with a particle size of 10-25 mm, the steel slag is ordinary converter steel slag, the pretreatment step is to add cement slurry to the steel slag for stirring, the weight ratio of cement slurry to steel slag is 1.5:5, until the surface of the steel slag is completely covered with the mixed slurry to obtain the pretreated steel slag; the cement slurry is a mixture of cement, mineral powder and water, and the weight ratio is 1:3:4.5.

[0043] The method for preparing the above-mentioned high early strength emulsified asphalt cold recycled mixture comprises the following steps:

[0044] (1) The above-mentioned waste asphalt mixture, new aggregate, mineral powder, cement, and pre-treated steel slag are fully stirred, and water is added to mix them for 40 seconds;

[0045] (2) adding emulsified asphalt to the mixture in step (1) and mixing thoroughly for 60 seconds;

[0046] (3) The mixture in step (2) is treated with a microwave emitter for 5 minutes to obtain an emulsified asphalt cold recycled mixture with high early strength.

[0047] The above microwave transmitter has an output power of 1000W.

[0048] Comparative Example 1

[0049] A high early strength emulsified asphalt cold recycled mixture, whose raw materials include the following components: 4.0 parts of emulsified asphalt, 76 parts of waste asphalt mixture, 8 parts of new aggregate, 0.8 parts of mineral powder, 0.5 parts of cement, 3.8 parts of water, and 18 parts of steel slag, wherein the emulsified asphalt is cationic slow-cracking emulsified asphalt, and the waste asphalt mixture is composed of the following waste particles in parts by weight: 72 parts of particles with a particle size of 0 to 10 mm, of which the fine milling sand equivalent of particles with a particle size of 0 to 4.75 mm is 86%, and 12 parts of particles with a particle size of 10 to 25 mm are used. The steel slag is ordinary converter slag without pretreatment.

[0050] The method for preparing the above-mentioned high early strength emulsified asphalt cold recycled mixture comprises the following steps:

[0051] (1) The above-mentioned waste asphalt mixture, new aggregate, mineral powder, cement, and steel slag are fully stirred, and water is added to mix them for 40 seconds;

[0052] (2) adding emulsified asphalt to the mixture in step (1) and mixing thoroughly for 60 seconds;

[0053] (3) The mixture in step (2) is treated with a microwave emitter for 5 minutes to obtain an emulsified asphalt cold recycled mixture with high early strength.

[0054] The above microwave transmitter has an output power of 1000W.

[0055] Comparative Example 2

[0056] A high early strength emulsified asphalt cold recycled mixture, the raw materials of which include the following components: 4.0 parts of emulsified asphalt, 76 parts of waste asphalt mixture, 8 parts of new aggregate, 0.8 parts of mineral powder, 0.5 parts of cement, 3.8 parts of water, and 18 parts of pretreated steel slag, wherein the emulsified asphalt is a cationic slow-cracking emulsified asphalt, the waste asphalt mixture is composed of the following parts by weight of waste particles, 72 parts of particles with a particle size of 0-10 mm, wherein the fine milling sand equivalent of particles with a particle size of 0-4.75 mm is 86%, 12 parts of particles with a particle size of 10-25 mm, the steel slag is ordinary converter steel slag, the pretreatment step is to add cement slurry to the steel slag for stirring, the weight ratio of cement slurry to steel slag is 1.5:5, until the surface of the steel slag is completely covered with the mixed slurry to obtain the pretreated steel slag; the cement slurry is a mixture of cement, mineral powder and water, and the weight ratio is 1:3:4.5.

[0057] The method for preparing the above-mentioned high early strength emulsified asphalt cold recycled mixture comprises the following steps:

[0058] (1) The above-mentioned waste asphalt mixture, new aggregate, mineral powder, cement, and pre-treated steel slag are fully stirred, and water is added to mix them for 40 seconds;

[0059] (2) Add emulsified asphalt to the mixture in step (1) and mix thoroughly for 60 seconds to obtain an emulsified asphalt cold recycled mixture with high early strength.

[0060] Comparative Example 3

[0061] A high early strength emulsified asphalt cold recycled mixture, whose raw materials include the following components: 4.0 parts of emulsified asphalt, 76 parts of waste asphalt mixture, 8 parts of new aggregate, 0.8 parts of mineral powder, 0.5 parts of cement, 3.8 parts of water, and 18 parts of steel slag, wherein the emulsified asphalt is a cationic slow-cracking emulsified asphalt, and the waste asphalt mixture is composed of the following waste particles in parts by weight: 72 parts of particles with a particle size of 0 to 10 mm, of which the fine milling sand equivalent of particles with a particle size of 0 to 4.75 mm is 86%, 12 parts of particles with a particle size of 10 to 25 mm, and the steel slag is ordinary converter slag.

[0062] The method for preparing the above-mentioned high early strength emulsified asphalt cold recycled mixture comprises the following steps:

[0063] (1) The above-mentioned waste asphalt mixture, new aggregate, mineral powder, cement, and steel slag are fully stirred, and water is added to mix them for 40 seconds;

[0064] (2) Add emulsified asphalt to the mixture in step (1) and mix thoroughly for 60 seconds to obtain an emulsified asphalt cold recycled mixture with high early strength.

[0065] Performance Verification:

[0066] The prepared mixture was divided into two parts. One part was formed into rutting specimens according to the test method of "Highway Engineering Asphalt and Asphalt Mixture Test Procedure" T0703-2011. Without curing, the rutting test was carried out at room temperature with reference to the test method of "Highway Engineering Asphalt and Asphalt Mixture Test Procedure" T 0719-2011 to verify the anti-rutting performance of the emulsified asphalt cold recycled pavement at around 5 am, when the construction was completed and traffic was immediately opened. The other part of the mixture was formed into Marshall specimens according to the molding conditions in my country's recycling technical specifications. This test adopted the double-sided compaction 75 times in one molding method, and the splitting strength test was carried out directly without curing to simulate the early strength of the cold recycled mixture.

[0067] Table 1 Test results of anti-rutting performance of emulsified asphalt cold recycled mixture under uninterrupted traffic conditions

[0068]

[0069] Table 2 Summary of early strength values ​​of emulsified asphalt mixture

[0070]

[0071] With reference to the Technical Specifications for Asphalt Pavement Construction of Highway Engineering, the dynamic stability requirement is >1000 times. It can be seen from the three embodiments in Table 1 that the rutting resistance of the emulsified asphalt cold recycled mixture that is opened to traffic immediately after paving fully meets the requirements, the rutting depth is small, and will not affect the paving of the structural layer above the emulsified asphalt cold recycled layer, and the early splitting strength is much greater than the specification requirements. In addition, according to the comparison with the three comparative examples, the road performance of the mixture with pretreated steel slag and microwave treatment is better.

Claims

1. A high early strength emulsified asphalt cold recycled mixture, comprising the following components in parts by weight: 3.2-4.5 parts of emulsified asphalt, 75-85 parts of waste asphalt mixture, 5-8 parts of new aggregate, 0.5-3.0 parts of mineral powder, 0.5-2.5 parts of cement, 2.5-5 parts of water, and 5-35 parts of pre-treated steel slag; the steel slag is electric furnace steel slag or converter steel slag, wherein the calcium oxide content is ≤3%, the magnesium oxide content is 3-10%, the manganese oxide content is 1-3%, the iron content is ≤2%, the water expansion rate is ≤2%, the maximum particle size is ≤31.5mm, and the crushing value is ≤30%; The pretreatment method of the steel slag is to completely immerse the steel slag in water for 10 to 24 hours, then fish out the steel slag and dry it to obtain pretreated steel slag; or add cement slurry to the steel slag and stir it until the surface of the steel slag is completely covered with the mixed slurry to obtain pretreated steel slag; the weight ratio of the cement slurry to the steel slag is 1 to 2.5:5 to 7.5, and the cement slurry is a mixture of cement, mineral powder and water, and the weight ratio is 1:2-4:4-5; The method for preparing the high early strength emulsified asphalt cold recycled mixture comprises the following steps: (1) Fully stir the waste asphalt mixture, new aggregate, mineral powder, cement, and pre-treated steel slag in the above-mentioned weight parts, add water and fully mix for 40 to 60 seconds; (2) Add emulsified asphalt to the mixture in step (1) and mix thoroughly for 60s to 90s; (3) The mixture in step (2) is treated with a microwave transmitter for 5 to 15 minutes to obtain an emulsified asphalt cold recycled mixture with high early strength.

2. According to the emulsified asphalt cold recycled mixture of claim 1, the emulsified asphalt is a slow-cracking cationic emulsified asphalt or a slow-cracking cationic modified emulsified asphalt, wherein the modification in the slow-cracking cationic modified emulsified asphalt is SBS modification or SBR modification, and the residual solid content is ≥62%.

3. According to the emulsified asphalt cold recycled mixture of claim 1, the waste asphalt mixture is composed of the following waste particles in parts by weight: 62 to 75 parts of particles with a particle size of 0 to 10 mm, wherein the fine milling sand equivalent of particles with a particle size of 0 to 4.75 mm is greater than 80%, and 10 to 20 parts of particles with a particle size of 10 to 25 mm.

4. According to the emulsified asphalt cold recycled mixture according to claim 1, the new aggregate is conventional asphalt mixture aggregate with a particle size of 10 to 25 mm.

5. According to the emulsified asphalt cold recycled mixture of claim 1, the mineral powder is mineral powder for asphalt mixture, and the content of total inorganic matter of active calcium, silicon and aluminum is greater than 32%.

6. According to the emulsified asphalt cold recycled mixture according to claim 1, the pretreatment method of the steel slag is to completely immerse the steel slag in water for 10 to 24 hours, then take out the steel slag and put it into a 100°C oven for drying or naturally dry it to obtain pretreated steel slag. The standard for drying or drying is that the same amount of steel slag is weighed at intervals of 30 minutes, and the mass difference is ≤0.5%.

7. According to the emulsified asphalt cold recycled mixture of claim 1, the weight ratio of cement, mineral powder and water in the cement slurry is 1:3:4.

5.

8. The emulsified asphalt cold recycled mixture according to claim 1 comprises the following components in parts by weight: 3.2-4.0 parts of emulsified asphalt, 75-80 parts of waste asphalt mixture, 5-8 parts of new aggregate, 0.5-1.0 parts of mineral powder, 0.5-1.2 parts of cement, 3.0-4.0 parts of water, and 15-20 parts of pretreated steel slag.

9. According to the emulsified asphalt cold recycled mixture of claim 1, the microwave transmitter is a closed device with an output power of 500~2000W.

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