An asphalt mixture and a preparation method and application thereof

Abstract

The application discloses asphalt mixture and a preparation method and application thereof. The asphalt mixture comprises 100 parts of base asphalt, 5-15 parts of rock asphalt, 15-40 parts of desulfurized rubber and 1250-3300 parts of mineral aggregate; the ash content of the rock asphalt is less than or equal to 20%; the mineral aggregate comprises aggregate and mineral powder; the aggregate comprises aggregate with a particle size of 0-3 mm, aggregate with a particle size of 3-5 mm, aggregate with a particle size of 5-10 mm and aggregate with a particle size of 10-15 mm; the mass percentage of the aggregate with a particle size of 0-3 mm is 14%-15%; the mass percentage of the aggregate with a particle size of 3-5 mm is 5%-7%; the mass percentage of the aggregate with a particle size of 5-10 mm is 37%-38%; the mass percentage of the aggregate with a particle size of 10-15 mm is 33%-34%; and the mass percentage of the mineral powder in the mineral aggregate is 8.5%-9%. The asphalt mixture preparation method is simple and easy to operate, and the prepared asphalt mixture has good comprehensive performance.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of road engineering asphalt mixture design and production, and relates to an asphalt mixture and a preparation method and application thereof. BACKGROUND

[0002] Asphalt pavement has become the main pavement form of various grades of roads in China due to its driving comfort, short construction period and easy maintenance and repair, etc. However, in the service process, different forms of pavement diseases are often induced due to traffic channelization, overloading and external environment, etc. Therefore, higher requirements are put forward for the road performance and durability of asphalt mixture, which is the main component of asphalt pavement. At present, the effective ways to improve the road performance of asphalt mixture include the following two main modes in addition to selecting high-quality raw materials (high-quality base asphalt and hard-textured aggregate, etc.): 1) modifying the base asphalt or its mixture by adding auxiliary additives (such as polymers, rock asphalt, rubber, high modulus agent, etc.); 2) optimizing process parameters (feeding sequence, mixing time, mixing temperature, etc.). Among them, the method of adding auxiliary additives is the most commonly used.

[0003] At present, the most commonly used base asphalt modifier in China is the polymer modifier represented by styrene-butadiene-styrene triblock copolymer (SBS), which has significant modification effect and relatively mature preparation method, and is widely used in high-grade asphalt pavement in China. However, it also has the shortcomings of high cost and uneven quality, which to some extent limits the popularization of SBS modified asphalt.

[0004] Natural rock asphalt is a kind of asphalt-like substance generated by the long-term oxidation and polymerization process of petroleum under the combined action of pressure, temperature, microorganisms, inorganic contact catalyst and moisture, etc. It is a derivative of petroleum like base asphalt, and the microstructure of the two is very similar, so it has good compatibility. As an excellent base asphalt modifier, rock asphalt can significantly improve the road performance of asphalt mixture such as high-temperature stability, water resistance and aging resistance, reduce the temperature sensitivity of the mixture, and improve the self-healing ability of the internal micro-cracks of the asphalt mixture, so that the asphalt mixture can achieve the road performance comparable to that of SBS modified asphalt mixture, and further improve the durability of the pavement structure (Reference: Mehmet Yilmaz, Muhammed Effects of SBS and different natural asphalts on the properties of bituminous binders and mixtures. Construction and Building Materials 2013, 44, 533-540.) According to the different places of origin, natural rock asphalt can be divided into Buton rock asphalt, Iranian rock asphalt, North American rock asphalt, and domestic Qingchuan rock asphalt and Xinjiang rock asphalt, etc. Buton rock asphalt belongs to high-ash natural rock asphalt, and the asphalt content is only about 20%, and the ash content reaches about 80%, which is often called "asphalt rock". Its modification effect on matrix asphalt is limited. In addition to the weakening effect of hard asphalt components on low-temperature crack resistance, the presence of a large amount of ash will significantly reduce the low-temperature ductility of asphalt binder under external force (see: DENG Xiangming, HUANG Hui, WANG Bin, et al. Modification Mechanism of Asphalt Modified with Rock Asphalt and Styrene-Butadiene Rubber (SBR) [J]. Advances in Civil Engineering, 2021, 2021(11):5533441.1-5533441.9.). Iranian rock asphalt, North American rock asphalt, and Qingchuan rock asphalt all belong to low-ash natural rock asphalt, and the asphalt content is usually more than 80%, and the ash content is less than 20%. The modification effect on matrix asphalt is relatively significant, and the low-ash content alleviates the weakening effect of the above stress concentration phenomenon on low-temperature ductility and reduces the influence of the addition of rock asphalt on the original aggregate gradation. However, due to the low penetration and ductility and high softening point of the asphalt component in low-ash rock asphalt, it is a hard asphalt. The addition of rock asphalt will increase the softening point of matrix asphalt, reduce the penetration and ductility, and increase the asphaltene content of matrix asphalt due to the addition of rock asphalt. Therefore, rock asphalt modified asphalt mixture has certain disadvantages in resisting low-temperature cracking and fatigue cracking.

[0005] Rubber is another common modifier of base asphalt, which can significantly improve the low-temperature crack resistance of base asphalt, but the improvement of high-temperature performance is relatively limited, which forms a complementary relationship with the modification effect of rock asphalt. Although traditional rubber has a certain modification effect on base asphalt, the compatibility of rubber with base asphalt is generally poor. After modification of base asphalt, not only the inherent excellent properties of rubber cannot be fully utilized, but also the modified asphalt has poor storage stability and is prone to segregation. Rubber devulcanization refers to the process of catalyzing the cross-linking bonds of vulcanized rubber by using a specific treatment method, which can promote the mutual fusion of rubber and base asphalt, and not only has better modification effect, but also effectively solves the problem of poor compatibility of ordinary rubber with base asphalt. Therefore, compared with ordinary rubber modified asphalt, devulcanized rubber modified asphalt has more excellent road performance.

[0006] To solve the above three problems: 1) the modification effect of high-ash rock asphalt is poor, not only the hard asphalt component itself weakens the low-temperature crack resistance, but also the presence of a large amount of ash significantly reduces the low-temperature ductility of asphalt binder under external force; 2) the low-ash rock asphalt modified asphalt mixture has insufficient low-temperature cracking and fatigue cracking resistance; 3) the modification effect of ordinary rubber is poor, and the storage stability of the modified asphalt is poor.

[0007] Chinese patent document CN202111029004.9 discloses a kind of nano composite natural rock modified asphalt mixture additive, its main raw material is natural rock asphalt, supplemented by waste tire rubber, polymer, nano diatomite, lignin fiber, nano zinc oxide and other raw materials. The invention relates to a powder-like modified additive of base asphalt, the maximum particle size is less than 1mm, which has complex components, complicated preparation process and strict process requirements, etc., which is not conducive to large-scale application.

[0008] Chinese patent document CN201910852682.1 proposes a modified asphalt material and a preparation method thereof, the base asphalt additive is rock asphalt, KH-550 modified stone powder, epoxy resin and rubber, and the obtained modified asphalt material has excellent high-temperature performance. The modified asphalt binder prepared by the wet process needs to preheat the base asphalt to 180-200℃, which promotes its rapid aging and increases energy consumption. It needs to be cut by a high-speed shear machine at a constant temperature, and the stone powder modification process is complicated.

[0009] Chinese patent document CN202010552945.X discloses an anti-high-temperature wet dry modified asphalt mixture and its preparation method and application. The main additives involved are SBS, rubber oil, stabilizer, rock asphalt, and diatomite. The preparation method of the modified asphalt mixture proposed by the invention is actually a wet process, which needs to prepare modified asphalt in advance, go through processes such as different component feeding, high-speed shearing, and development, and then prepare the modified asphalt mixture, and the rubber material involved is rubber oil.

[0010] Fan et al. used styrene-butadiene rubber (SBR) and Buton rock asphalt (BRA) to compound modify the base asphalt to improve its low-temperature performance. They found that by adding SBR into BRA modified asphalt, the low-temperature performance could be significantly improved while ensuring high-temperature performance. (Fan Xiyan Lu Weiwei, Lv Songtao, et al. Improvement of Low-Temperature Performance of Buton Rock Asphalt Composite Modified Asphalt by Adding Styrene-Butadiene Rubber [J]. Materials, 2019, 12(15): 2358.) Wang Qimin et al. used waste rubber (CR) processed from waste tires, Trinidad Lake natural asphalt (TLA), and Indonesian Buton rock natural asphalt (BRA) to compound modify 70# base asphalt. They found that the anti-aging performance of the composite modified asphalt with 10% CR + 20% BRA was the best, and the improvement effect of the two modifiers could be additive. (Wang Qimin, Wu Wenhua, Li Heng, et al. Anti-aging performance and mechanism of waste rubber / natural asphalt composite modified asphalt [J]. Highway, 2022, 12: 322-329.) The above studies are all focused on the performance of composite modified asphalt binders prepared by wet process, and the rock asphalt involved is high-ash Buton rock asphalt, which has certain limitations in modification effect. The rubber is ordinary rubber, which has poor compatibility with base asphalt.

[0011] Hou found that the dry process composite modification can significantly improve the splitting strength of asphalt mixture and the freeze-thaw splitting strength ratio, and the splitting load deformation of the mixture increases, which improves the brittleness of BRA single modified asphalt mixture.(Hou, J. Rubber and rock asphalt composite dry modified high modulus asphalt mixture test research[J]. Journal of Yancheng Institute of Technology (Natural Science Edition). 2020, 33(04): 5-13.); Wang studied the road performance of Albania rock asphalt and rubber composite modified asphalt and its mixture(wet process), and found that the composite modified asphalt mixture has excellent high temperature stability and water stability, and the low temperature crack resistance is not much different from that of rubber asphalt.(Wang, Y. Albania rock asphalt / rubber composite modified asphalt and its mixture performance research[D]. Guilin: Guangxi University, 2021).

[0012] In summary, among the related literature and patents of rock asphalt and rubber composite modification, there are problems such as complex additive components, complicated preparation process and strict process requirements, and the rubber used is ordinary rubber after simple process treatment of waste tires, which has the defects of poor modification effect and poor storage stability of modified asphalt as described in the foregoing, and the rock asphalt mainly used is Buntun rock asphalt with high ash content and low asphalt content(usually about 20%), and the modification effect is limited by its inherent technical parameters. This problem needs to be solved. SUMMARY

[0013] The technical problem to be solved by the present application is to overcome the defects of the prior art, such as the poor comprehensive performance of single modified asphalt(such as high cost, uneven quality of SBS modified asphalt, poor low temperature performance of rock asphalt modified asphalt, poor compatibility of rubber modified asphalt, and limited improvement of high temperature performance), and the complicated wet modification process of composite modification, and to provide a kind of asphalt mixture and its preparation method and application. The asphalt mixture preparation method of the present application is simple and easy to operate, and the prepared asphalt mixture has low cost and good comprehensive performance, that is, it has good low temperature stability, high temperature stability, water stability and fatigue life.

[0014] During the research and development process, the inventors unexpectedly found that when low-ash rock asphalt and desulfurized rubber are used to dry composite modify the base asphalt, and the specific proportion of each particle size of the aggregate is matched, the low-ash rock asphalt can improve the high temperature performance while the desulfurized rubber can improve the low temperature cracking and fatigue cracking performance of the asphalt mixture, effectively solving the problems of insufficient low temperature performance of rock asphalt modified asphalt mixture and insufficient fusion of ordinary rubber and base asphalt, fully utilizing the excellent properties of the two modifiers, reducing the dependence of base asphalt on excellent modifier polymer SBS, and providing another effective way for the preparation of high-grade road asphalt mixture.

[0015] The present application provides a kind of asphalt mixture, it includes the following mass fraction of raw materials: 100 parts of base asphalt, 5-15 parts of rock asphalt, 15-40 parts of devulcanized rubber and 1250-3300 parts of mineral aggregate;

[0016] Wherein, the ash content of the rock asphalt is ≤20%;

[0017] Wherein, the mineral aggregate includes aggregate and mineral powder;The aggregate includes: aggregate with particle size of 0-3mm, aggregate with particle size of 3-5mm, aggregate with particle size of 5-10mm and aggregate with particle size of 10-15mm;

[0018] In the mineral aggregate, the mass percentage of the aggregate with particle size of 0-3mm is 14%-15%;The mass percentage of the aggregate with particle size of 3-5mm is 5%-7%;The mass percentage of the aggregate with particle size of 5-10mm is 37%-38%;The mass percentage of the aggregate with particle size of 10-15mm is 33%-34%;

[0019] In the mineral aggregate, the mass percentage of the mineral powder is 8.5%-9%;

[0020] The above percentage indicates the percentage of the mass of each component in the mineral aggregate.

[0021] In the present application, the mass fraction of the rock asphalt is preferably 6-14 parts, more preferably 8-12 parts, for example 9 parts, 10 parts or 11 parts.

[0022] In the present application, the mass fraction of the devulcanized rubber is preferably 18-36 parts, for example 20 parts, 24 parts, 27 parts, 30 parts or 33 parts.

[0023] In the present application, the mass fraction of the mineral aggregate is preferably 1274-2730 parts, more preferably 1365-2275 parts, and further more preferably 1456-1820 parts, for example 1538 parts, 1667 parts or 1818 parts.

[0024] In the present application, the mass percentage of the aggregate in the mineral aggregate is preferably 91%-91.2%, for example 91%.

[0025] In the present application, the mass fraction of the aggregate is preferably 1162-2484 parts, more preferably 1245-2070 parts, and further more preferably 1337-1656 parts, for example 1400 parts, 1517 parts or 1654 parts.

[0026] In the present application, the mass percentage of the aggregate with particle size of 0-3mm in the mineral aggregate is preferably 14.5%-15%, for example 15%.

[0027] In the present application, the mass percentage of the aggregate with a particle size of 3-5 mm in the mineral aggregate is preferably 5%-6%, for example 5%.

[0028] In the present application, the mass percentage of the aggregate with a particle size of 5-10 mm in the mineral aggregate is preferably 37.5%-38%, for example 38%.

[0029] In the present application, the mass percentage of the aggregate with a particle size of 10-15 mm in the mineral aggregate is preferably 33%-33.5%, for example 33%.

[0030] In the present application, the mass percentage of the mineral powder in the mineral aggregate is preferably 8.8%-9%, for example 9%.

[0031] In the present application, the mass percentage of the mineral powder is preferably 112-246 parts, more preferably 120-205 parts, further more preferably 128-164 parts, for example 138 parts, 150 parts or 164 parts.

[0032] In the present application, the particle size specification of the mineral powder in the mineral aggregate can include the following: 100% passing through a 0.6 mm sieve, 90-100% passing through a 0.15 mm sieve and 75-100% passing through a 0.075 mm sieve; preferably including: 100% passing through a 0.6 mm sieve, 98.2% passing through a 0.15 mm sieve and 88.3% passing through a 0.075 mm sieve.

[0033] In a preferred embodiment, the mineral aggregate is composed of aggregate and mineral powder,

[0034] The aggregate includes the following mass percentages of components: the mass percentage of aggregate with a particle size of 0-3 mm is 15%; the mass percentage of aggregate with a particle size of 3-5 mm is 5%; the mass percentage of aggregate with a particle size of 5-10 mm is 38%; the mass percentage of aggregate with a particle size of 10-15 mm is 33%;

[0035] The particle size specification of the mineral powder includes the following: 100% passing through a 0.6 mm sieve, 98.2% passing through a 0.15 mm sieve and 88.3% passing through a 0.075 mm sieve.

[0036] In the present application, the mass percentage of the rock asphalt in the aggregate can be 0.5%-0.8%, preferably 0.6%-0.7%.

[0037] In the present application, the mass percentage of the devulcanized rubber in the aggregate can be 0.5%-2.5%, preferably 1%-2%, for example 1.5%, 1.6% or 1.8%.

[0038] In the present application, the type of base asphalt can be conventional in the art.

[0039] In the present application, the penetration of the base asphalt can be 60-80 / 0.1 mm, for example 71 / 0.1 mm. The penetration refers to the depth of a standard cone (100 gram load) that sinks into a sample kept at 25°C in 5 seconds.

[0040] In the present application, the softening point of the base asphalt can be ≥ 46°C, for example 46-55°C. The softening point refers to the temperature at which a substance softens.

[0041] In the present application, the ductility of the base asphalt can be ≥ 20 cm. The ductility refers to the length of a standard test piece in the shape of an 8, when the asphalt is stretched to break at a temperature of 10°C at a speed of 5 cm per minute.

[0042] In the present application, the base asphalt is preferably No. 50 asphalt and / or No. 70 asphalt.

[0043] In a preferred embodiment, the base asphalt is No. 70 asphalt having a penetration of 60-80 / 0.1 mm, a softening point of ≥ 46°C, and a ductility of ≥ 20 cm.

[0044] In the present application, the ash content of the rock asphalt is preferably ≤ 15%, for example 10% or 7.9%. The ash content indicates the percentage of the mass of the ash relative to the mass of the rock asphalt.

[0045] In the present application, the asphalt content of the rock asphalt is preferably ≥ 80%, preferably 81-95%, for example 91.8%. The asphalt content indicates the percentage of the mass of the asphalt relative to the mass of the rock asphalt.

[0046] In the present application, the softening point of the rock asphalt can be 180-200°C, preferably 182-195°C, for example 185°C.

[0047] In the present application, the density of the rock asphalt can be 1-2 g / cm 3 , preferably 1.05-1.5 g / cm 3 , for example 1.06 g / cm 3 .

[0048] In the present application, the water content of the rock asphalt can be < 1%, preferably < 0.8%, for example < 0.5%. The water content indicates the percentage of the mass of the water relative to the mass of the rock asphalt.

[0049] In the present application, the rock asphalt is preferably one or more of North American rock asphalt, Iranian rock asphalt, and Qingchuan rock asphalt, for example North American rock asphalt.

[0050] In a preferred embodiment, the rock asphalt is North American rock asphalt having an ash content of 7.9%, a bitumen content of 91.8%, a softening point of 185°C, a density of 1.06 g / cm 3 , a water content of <0.5%.

[0051] In the present invention, the devulcanized rubber can be conventional in the art.

[0052] In the present invention, the devulcanized rubber can have a particle size of 30-50 mesh, such as 40 mesh.

[0053] In the present invention, the devulcanized rubber can have a sol content of >50%, preferably 58%-65%, such as 62.1%.

[0054] In the present invention, the devulcanized rubber can have a Mooney viscosity of <40%, preferably 25%-35%, such as 29.5%.

[0055] In a preferred embodiment, the devulcanized rubber has a particle size of 40 mesh, a sol content of 62.1%, and a Mooney viscosity of 29.5%.

[0056] In the present invention, the aggregate and the mineral powder should meet the requirements of the Technical Specification for Construction of Highway Asphalt Pavement (JTGF40-2004).

[0057] In the present invention, the aggregate generally refers to particulate loose material used for preparing concrete or mortar, such as fine aggregate and / or coarse aggregate. The fine aggregate is preferably limestone. The coarse aggregate is preferably limestone and / or basalt. In the field of asphalt mixture, the fine aggregate generally refers to aggregate having a particle size of <2.36 mm. The coarse aggregate generally refers to aggregate having a particle size of >2.36 mm.

[0058] In the present invention, the particle size of the aggregate can be determined by the scenario in which the asphalt mixture is used, such as when the asphalt mixture is used in the upper layer of the pavement, the particle size of the aggregate is generally ≤13.2 mm. When the asphalt mixture is used in the middle layer of the pavement, the maximum nominal particle size of the aggregate is generally ≤19 mm. When the asphalt mixture is used in the lower layer of the pavement, the maximum nominal particle size of the aggregate is generally ≤26.5 mm.

[0059] In the present invention, the type of the mineral powder can be conventional in the art, preferably limestone mineral powder.

[0060] In the present invention, the gradation type of the asphalt mixture can be conventional in the art, preferably SMA or AC. When the gradation type of the asphalt mixture is SMA, the raw materials of the asphalt mixture should further include fibers.

[0061] In the present invention, the type of the fibers can be conventional in the art, preferably lignin fibers or polyester fibers.

[0062] wherein the mass of the fibres is preferably 0.3% of the mass of the mineral aggregate.

[0063] In the present application, the asphalt mixture can have a void content of 3-4%, for example 3.5%.

[0064] In a preferred embodiment, the asphalt mixture comprises the following mass proportions of raw materials: 100 parts of base asphalt, 10 parts of rock asphalt, 18 parts of devulcanized rubber and 1818 parts of mineral aggregate, the base asphalt being 70# asphalt, the rock asphalt being North American rock asphalt having an ash content of 7.9%, and the mineral aggregate consisting of 1654 parts of aggregate and 164 parts of mineral powder.

[0065] In a preferred embodiment, the asphalt mixture comprises the following mass proportions of raw materials: 100 parts of base asphalt, 10 parts of rock asphalt, 27 parts of devulcanized rubber and 1818 parts of mineral aggregate, the base asphalt being 70# asphalt, the rock asphalt being North American rock asphalt having an ash content of 7.9%, and the mineral aggregate consisting of 1654 parts of aggregate and 164 parts of mineral powder.

[0066] In a preferred embodiment, the asphalt mixture comprises the following mass proportions of raw materials: 100 parts of base asphalt, 10 parts of rock asphalt, 36 parts of devulcanized rubber and 1818 parts of mineral aggregate, the base asphalt being 70# asphalt, the rock asphalt being North American rock asphalt having an ash content of 7.9%, and the mineral aggregate consisting of 1654 parts of aggregate and 164 parts of mineral powder.

[0067] In a preferred embodiment, the asphalt mixture comprises the following mass proportions of raw materials: 100 parts of base asphalt, 10 parts of rock asphalt, 27 parts of devulcanized rubber and 1667 parts of mineral aggregate, the base asphalt being 70# asphalt, the rock asphalt being North American rock asphalt having an ash content of 7.9%, and the mineral aggregate consisting of 1517 parts of aggregate and 150 parts of mineral powder.

[0068] In a preferred embodiment, the asphalt mixture comprises the following mass proportions of raw materials: 100 parts of base asphalt, 10 parts of rock asphalt, 27 parts of devulcanized rubber and 1667 parts of mineral aggregate, the base asphalt being 70# asphalt, the rock asphalt being North American rock asphalt having an ash content of 7.9%, and the mineral aggregate consisting of 1538 parts of aggregate and 138 parts of mineral powder.

[0069] The present application also provides a method for preparing the asphalt mixture as described above, which is achieved by any one of the following methods:

[0070] Method one: the base asphalt, the aggregate, the rock asphalt, the devulcanized rubber and the mineral powder are mixed and developed, and that is all;

[0071] The second way is that the base pitch, the rock pitch and the devulcanized rubber are mixed and sheared to obtain a modified pitch, and the modified pitch, the aggregate and the mineral powder are mixed and developed.

[0072] In the first way, the mixing can be a conventional operation in the art other than shearing mixing. The mixing is generally accompanied by stirring. The stirring time can be 20-50 s, for example 30 s or 45 s. The stirring temperature can be 150-170℃, for example 160℃.

[0073] In the first way, the developing conditions can be conventional in the art, and the developing temperature can be 160-170℃, for example 170℃. The developing time can be conventional in the art, for example 0.5-2 h, for example 1 h.

[0074] In the first way, the preparation method of the pitch mixture preferably comprises the following steps: the preheated base pitch and the aggregate are mixed for the first time, and then mixed with the rock pitch for the second time, and then mixed with the devulcanized rubber for the third time, and then mixed with the mineral powder for the fourth time, and then developed.

[0075] When the raw materials of the pitch mixture further contain fibers, the fibers are added in the fourth mixing.

[0076] The preheating temperature can be 150-170℃, for example 160℃. The preheating time can be 1-3 h, for example 2 h.

[0077] The first mixing temperature can be 150-170℃, for example 160℃. The first mixing time can be 20-40 s, for example 30 s.

[0078] The second mixing temperature can be 150-170℃, for example 160℃. The second mixing time can be 20-40 s, for example 30 s.

[0079] The third mixing temperature can be 150-170℃, for example 160℃. The third mixing time can be 20-40 s, for example 30 s.

[0080] The fourth mixing temperature can be 150-170℃, for example 160℃. The fourth mixing time can be 20-50 s, for example 45 s.

[0081] In the second way, the mixing can be shearing mixing. The shearing speed can be 10000-140000 ppm, for example 12000 ppm.

[0082] In the present application, in the second aspect, the developing condition can be conventional in the art, and the developing temperature can be 160-170℃, for example 170℃. The developing time can be conventional in the art, for example 0.5-2h, for example 1h.

[0083] In the present application, in the second aspect, the asphalt mixture preparation method preferably comprises the following steps: mixing the preheated base asphalt and the rock asphalt for the first time, heating, first shearing, mixing the modified asphalt and the aggregate for the third time, and mixing the modified asphalt and the mineral powder for the fourth time.

[0084] When the raw materials of the asphalt mixture further contain fibers, the fibers are added in the fourth mixing.

[0085] The preheating temperature of the base asphalt can be 150-170℃, for example 160℃. The preheating time can be 1-3h, for example 2h.

[0086] The first mixing temperature can be 150-170℃, for example 160℃. The first mixing time can be 20-40s, for example 30s.

[0087] The heating temperature can be 160-180℃, for example 175℃.

[0088] The first shearing speed can be 10000-14000ppm, for example 12000ppm. The first shearing time can be 20-40min, for example 30min.

[0089] The second mixing temperature can be 150-170℃, for example 175℃.

[0090] The second shearing speed can be 10000-14000ppm, for example 12000ppm. The second shearing time can be 20-50min, for example 45min.

[0091] The preheating temperature of the modified asphalt can be 150-180℃, for example 175℃.

[0092] The third mixing temperature can be 150-180℃, for example 175℃. The third mixing time can be 20-40s, for example 30s.

[0093] The fourth mixing temperature can be 150-170℃, for example 175℃. The fourth mixing time can be 20-50s, for example 45s.

[0094] The application further provides application of the asphalt mixture in the field of road engineering.

[0095] On the basis of common knowledge in the art, the above-mentioned preferred conditions can be combined arbitrarily, thereby obtaining various preferred examples of the application.

[0096] The reagents and raw materials used in the application are commercially available.

[0097] The positive progress effect of the application is that:

[0098] The matrix asphalt, rock asphalt with ash content of ≤20%, devulcanized rubber and aggregate and mineral powder meeting specific particle sizes are mixed in specific mass fractions to obtain the asphalt mixture. The asphalt mixture of the application fully plays the modification effect of low-ash rock asphalt and devulcanized rubber, and forms a complementary relationship. The asphalt mixture of the application has a low cost. The asphalt mixture can be prepared by dry modification, and the preparation method is simple and easy to operate.

[0099] The asphalt mixture has a good comprehensive performance, that is, has good low-temperature stability, high-temperature stability, water stability and fatigue life, and comprehensively improves the road performance of the asphalt mixture, provides another effective way for the preparation of high-performance asphalt mixture, consumes a certain amount of waste tires, reduces the dependence of high-quality matrix asphalt modifier on polymer SBS, has significant economic and environmental benefits. BRIEF DESCRIPTION OF DRAWINGS

[0100] Figure 1 The grading curve of the mineral aggregate used in Examples 1-9 and Comparative Examples 1-5. DETAILED DESCRIPTION

[0101] The application will be further described below by way of examples, but the application is not limited in the scope of the examples. The experimental methods not specified in the following examples are selected according to conventional methods and conditions, or according to the instructions of the commodity.

[0102] All the raw materials in the examples and comparative examples of the application can be obtained by commercial purchase.

[0103] The matrix asphalt is purchased from Shanghai Chengjianri Special Asphalt Co., Ltd., and its type is 70# asphalt, the penetration is 60-80 / 0.1mm, the softening point is ≥46℃, and the ductility is ≥20cm.

[0104] The rock asphalt used in Examples 1-9 and Comparative Examples 1-4 is North American rock asphalt, which is purchased from Qingdao Meilian Energy Co., Ltd.; the rock asphalt used in Comparative Example 5 is Buton rock asphalt, which is purchased from Anhui Zhongying Natural Rock Asphalt Technology Co., Ltd., and the main parameters of the two are shown in Table 1:

[0105] Table 1

[0106] Technical parameters North American rock asphalt Buton rock asphalt Place of origin Uintah Basin, eastern Utah, northern USA Buton Island, Indonesia Color Black powder Black-brown powder Rock asphalt class Class I Class II Asphalt content 91.8％ 18.1％ Density 1.06 g / cm 3 ]] 1.80 g / cm 3 ]]> Moisture content <0.5％ <0.2％ Softening point 185℃ — Ash content 7.9％ 81.8％

[0107] In the formula, the desulfurized rubber is purchased from Liyang Ruipu New Material Co., Ltd., the particle size is 40 mesh, the sol content is 62.1%, and the Mooney viscosity is 29.5%.

[0108] In the formula, the SBS is purchased from Shanghai Chengjian Rili Special Asphalt Co., Ltd.

[0109] In the formula, the aggregate is limestone fine aggregate (particle size specification is 0-3 mm) and basalt coarse aggregate (particle size specification is 3-5 mm, 5-10 mm and 10-15 mm), the limestone fine aggregate is purchased from Wuxi Meizhui Best Building Material Co., Ltd., and the basalt coarse aggregate is purchased from Lingshou County Yandeng Mineral Product Processing Factory.

[0110] In the formula, the mineral powder in Examples 1-9 and Comparative Examples 1-5 is limestone mineral powder, the particle size specification is (100% of 0.6 mm sieve hole passing rate, 98.2% of 0.15 mm sieve hole passing rate, and 88.3% of 0.075 mm sieve hole passing rate), and the mineral powder is purchased from Quzhou Shangfang Building Material Co., Ltd.

[0111] In the formula, the fiber is lignin fiber, and is purchased from Taian Anfeng New Material Technology Co., Ltd.

[0112] In the formula, the SMA-13 type asphalt mixture is used in the examples and comparative examples of the application.

[0113] In the examples and comparative examples of the application, the particle size of each aggregate is determined by the following steps:

[0114] According to the Technical Specification for Construction of Highway Asphalt Pavement (JTG F40-2004), the Aggregate Test Rules for Highway Engineering (JTG E41-2005) and the Test Rules for Asphalt and Asphalt Mixture for Highway Engineering (JTG E20-2011), the SMA-13 asphalt mixture mixture ratio is designed according to the following steps based on the Marshall design method, the mineral aggregate gradation and the optimum oil stone ratio are determined, and the target air void is controlled at 3%-4%.

[0115] 1. Sieving and density test

[0116] According to the Aggregate Test Rules for Highway Engineering (JTG E41-2005), the sieving and density test is performed on each aggregate and mineral powder, as shown in Tables 2 and 3.

[0117] Table 2 Sieving test results of aggregate and mineral powder

[0118]

[0119] Table 3 Density test results of aggregate and mineral powder

[0120]

[0121] 2. Selecting initial gradation and asphalt-aggregate ratio

[0122] According to the screening results of each set of aggregate and mineral powder, the initial gradation is determined by the conventional method in the art (adjusting according to the lower limit, upper limit and median value of the gradation, respectively).

[0123] 3. Marshall test

[0124] The Marshall test is performed according to the “Standard Test Methods of Bituminous Pitch and Asphalt Mixture for Highway Engineering” (JTG E20-2011), and the volume parameters (interstitial volume of aggregate VMA, coarse aggregate skeleton interstitial volume VCA mix , asphalt saturation VFA and maximum theoretical density γ t , bulk density γ f , porosity vv) under different gradations and asphalt-aggregate ratios are measured.

[0125] If the volume parameters corresponding to the target porosity vv meet the requirements of the “Technical Specification for Construction of Highway Asphalt Pavement” (JTG F40-2004), the asphalt-aggregate ratio is preliminarily determined as the optimal asphalt-aggregate ratio, and step 4 is performed. Otherwise, step 2 is repeated.

[0126] 4. Performance verification

[0127] The performance of the optimal asphalt-aggregate ratio and aggregate gradation preliminarily determined in step 2 is verified according to the “Standard Test Methods of Bituminous Pitch and Asphalt Mixture for Highway Engineering” (JTG E20-2011), mainly including: stability MS and flow value LS (T 0709-2011), Schellenberg asphalt leakage test (T 0732-2011), Kentaur flying test (T 0733-2011), rutting test (T0719-2011), low-temperature beam test (T0715-2011) and freeze-thaw splitting test (T 0729-2000) and the like.

[0128] 5. Determining the aggregate gradation and the optimal asphalt-aggregate ratio

[0129] The performance test results in step 4 should meet the “Technical Specification for Construction of Highway Asphalt Pavement” (JTG F40-2004), and the aggregate gradation with the best performance and the corresponding asphalt-aggregate ratio are selected as the final determined aggregate gradation and the optimal asphalt-aggregate ratio.

[0130] 6. Incorporating rock asphalt and desulfurized rubber powder

[0131] On the basis of the mix proportion determined in step 5, rock asphalt and desulfurized rubber powder are incorporated in proportion, and the relevant volume parameters and performance indicators are verified, and the asphalt-aggregate ratio is adjusted (if necessary) as appropriate to make the volume parameters meet the requirements.

[0132] The grading curve determined by the above steps is shown in FIG. 1. Figure 1 The determined oil aggregate ratio is 5.5±0.5%, oil aggregate ratio = mass of base asphalt / total mass of (aggregate + mineral powder) x 100%.

[0133] Examples 1-5 and Comparative Examples 1-5

[0134] The aggregate and mass percentage used in Examples 1-5 and Comparative Examples 1-5 are shown in Table 4 below.

[0135] Table 4

[0136]

[0137]

[0138] The component composition of the asphalt mixture in Examples 1-5 and Comparative Examples 1-5 is shown in Table 5 below.

[0139] Table 5

[0140]

[0141]

[0142] The preparation method of the asphalt mixture in Examples 1-3, Examples 6-9, and Comparative Examples 1-5 includes the following steps:

[0143] The base asphalt is preheated for 2h to 160℃, first stirred and mixed with aggregate at 160℃ for 30s, second stirred and mixed with rock asphalt (or SBS) at 160℃ for 30s, third stirred and mixed with desulfurized rubber at 160℃ for 30s, fourth stirred and mixed with mineral powder and fiber at 160℃ for 45s, and finally developed at 170℃ for 1h.

[0144] The preparation method of the asphalt mixture in Example 4 includes the following steps:

[0145] The base asphalt is preheated for 2h to 160℃, first stirred and mixed with rock asphalt at 160℃ for 30s, and heated to 175℃, and then high-speed sheared at 12000rpm for 30min, and desulfurized rubber is added, and high-speed sheared at 12000rpm at 175℃ for 45min to obtain the modified asphalt.

[0146] The modified asphalt is preheated to 175℃, stirred and mixed with aggregate for 30s, stirred and mixed with mineral powder and fiber for 45s, and finally developed at 170℃ for 1h.

[0147] The preparation method of the asphalt mixture in Example 5 includes the following steps:

[0148] The base asphalt is preheated for 2 h to 160°C, first stirred mixed with aggregate at 160°C for 30 s, second stirred mixed with devulcanized rubber at 160°C for 30 s, third stirred mixed with rock asphalt at 160°C for 30 s, fourth stirred mixed with mineral powder and fiber at 160°C for 45 s, and finally constant temperature development at 170°C for 1 h.

[0149] Comparative Examples 6-7

[0150] The components and mass percentages of the mineral aggregates used in Comparative Examples 6-7 are shown in Table 6 below:

[0151] Table 6

[0152]

[0153] The gradation values of the mineral aggregates used in Comparative Examples 6-7 are shown in Table 7 below:

[0154] Table 7

[0155]

[0156] Since the volume parameters of the aggregate and mineral powder used in Comparative Example 6 and Comparative Example 7 do not meet the requirements of the specification, the subsequent asphalt mixture experiments cannot be continued.

[0157] Effect Example 1

[0158] The volume parameters (interstitial porosity of mineral aggregate VMA, coarse aggregate skeleton interstitial porosity VCAmix, asphalt saturation VFA, maximum theoretical density γt, bulk density γf, porosity vv, etc.) of the mineral aggregates used in Examples 1-9 and Comparative Examples 1-5, and the mineral aggregates used in Comparative Examples 6-7, are tested, and the test results are shown in Table 8.

[0159] Table 8

[0160]

[0161]

[0162] Effect Example 2

[0163] The mineral aggregate used in Examples 1-9 and Comparative Examples 1-5 was subjected to performance verification, mainly including: stability MS and flow value LS (T 0709-2011), Schellenberg asphalt leakage test (T 0732-2011), Kentaur flying test (T 0733-2011), rutting test (T 0719-2011), low-temperature beam test (T 0715-2011), and freeze-thaw splitting test (T 0729-2000), etc. The results are shown in Table 9.

[0164] Table 9

[0165] Regulation provision Measured values of the mineral aggregates of Examples 1-9 and Comparative Examples 1-5 Stability MS ≥ 5.5 Kn 8.2 Kn Flow value LS 2-5 mm 3.5 mm Serenberg asphalt bleeding test ≤0.2％ 0.09％ Kentucky flying stone test ≤20％ 10.8％ Rutting test ≥ 3000 cycles mm -1 ]] 4851 times • mm -1 ]] Low-temperature beam test ≥ 2800 με 3015.2 με Freeze-thaw splitting test ≥80％ 91.2％

[0166] Example 3

[0167] The asphalt mixtures of Examples 1-9 and Comparative Examples 1-5 were subjected to tests of high-temperature stability, low-temperature stability, water stability, and fatigue life. The test standards and results are shown in Table 10.

[0168] Table 10

[0169]

[0170]

[0171] As can be seen from Table 10, in Examples 1-9, the asphalt mixtures were significantly improved in individual road performance by the complex modification of low-ash rock asphalt and desulfurized rubber on the base asphalt.

[0172] Compared with Example 4 of wet modification, Example 1 adopted dry complex modification, which was more simple and convenient. In terms of high- and low-temperature stability, Example 4 of wet modification was slightly better than Example 1 of dry modification, while the water stability and fatigue life of Example 1 of dry modification were significantly better than Example 4 of wet modification.

[0173] As can be seen from Comparative Example 1, Example 2, and Example 3, the high-temperature stability tended to decrease with the increase of the amount of desulfurized rubber, while the water stability was on the contrary. The anti-low-temperature cracking and anti-fatigue cracking performance both tended to first increase and then decrease with the increase of the amount of desulfurized rubber.

[0174] Compared with Examples 1 and 3, when the amount of desulfurized rubber in Example 2 was appropriate, the high- and low-temperature stability of the obtained asphalt mixture was basically comparable to that of Comparative Example 1 (SBS modified asphalt mixture), and the water stability and fatigue life could surpass those of Comparative Example 1 (SBS modified asphalt mixture).

[0175] Compared with Example 1 and Example 5, the feeding sequence of rock asphalt and desulfurized rubber powder had little effect on the road performance of the modified asphalt mixture. Overall, the feeding sequence of rock asphalt before desulfurized rubber powder was better.

[0176] Compared with Example 2, when the oil-stone ratio in Example 6 and Example 7 is higher, i.e. the amount of aggregate and mineral powder is reduced under the same amount of base asphalt, the performances of the asphalt mixture are slightly decreased.

[0177] Compared with Example 2, when the amount of rock asphalt in Example 8 is less, the high-temperature, water stability and fatigue resistance of the asphalt mixture are slightly decreased, and the low-temperature performance is slightly increased.

[0178] Compared with Example 2, when the amount of rock asphalt in Example 9 is more, the low-temperature stability and fatigue resistance of the asphalt mixture are slightly decreased, and the high-temperature and water stability are slightly increased.

[0179] Compared with Example 1, when no devulcanized rubber is added in Comparative Example 3, the high-temperature and low-temperature performances are poor.

[0180] Compared with Example 6, when no rock asphalt is added in Comparative Example 4, the performances are poor.

[0181] Compared with Example 1, when the Buton rock asphalt with high ash content is used in Comparative Example 5, the performances are poor.

[0182] In summary, when the low-ash rock asphalt content is 10% of the mass of the base asphalt, the devulcanized rubber content is 27% of the mass of the base asphalt, and the low-ash asphalt and the devulcanized rubber are used to prepare the composite modified asphalt mixture by the dry process, the comprehensive performance of the asphalt mixture is optimal, the process is simple and operable, and the application prospect is broad.

Claims

1. An asphalt mixture, characterized in that, It comprises raw materials in mass fractions as follows: 100 parts of base pitch, 5-15 parts of rock asphalt, 27-36 parts of devulcanized rubber and 1250-3300 parts of mineral aggregate; The ash content of the rock asphalt is ≤20%; The mineral aggregate comprises aggregate and mineral powder; the aggregate comprises aggregate with a particle size of 0-3 mm, aggregate with a particle size of 3-5 mm, aggregate with a particle size of 5-10 mm and aggregate with a particle size of 10-15 mm; In the mineral aggregate, the mass percentage of the aggregate with a particle size of 0-3 mm is 14%-15%; the mass percentage of the aggregate with a particle size of 3-5 mm is 5%-7%; the mass percentage of the aggregate with a particle size of 5-10 mm is 37%-38%; and the mass percentage of the aggregate with a particle size of 10-15 mm is 33%-34%; In the mineral aggregate, the mass percentage of the mineral powder is 8.5%-9%; The asphalt mixture is prepared by the following method: The preheated base pitch and the aggregate are mixed for the first time, then mixed with the rock asphalt for the second time, then mixed with the devulcanized rubber for the third time, and then mixed with the mineral powder for the fourth time, and developed; The first mixing time is 20-40 s; The second mixing time is 20-40 s; The third mixing time is 20-40 s; The fourth mixing time is 20-40 s.

2. The asphalt mixture of claim 1, wherein, The raw materials of the asphalt mixture satisfy one or more of the following conditions: (1) the mass fraction of the rock asphalt is 6-14 parts, preferably 8-12 parts, for example 9 parts, 10 parts or 11 parts; (2) the mass fraction of the devulcanized rubber is 20 parts, 24 parts, 27 parts, 30 parts or 33 parts; (3) the mass fraction of the mineral aggregate is 1274-2730 parts, preferably 1365-2275 parts, more preferably 1456-1820 parts, for example 1538 parts, 1667 parts or 1818 parts; (4) in the mineral aggregate, the mass percentage of the mineral powder is 8.8%-9%, for example 9%; (5) the mass ratio of the rock asphalt to the aggregate is 0.5%-0.8%, preferably 0.6%-0.7%; and (6) the mass ratio of the devulcanized rubber to the aggregate is 0.5%-2.5%, preferably 1%-2%, for example 1.5%, 1.6% or 1.8%.

3. The asphalt mixture of claim 1, wherein, The mass fractions of the raw materials of the asphalt mixture satisfy the following conditions (1) and / or (2): (1) the mass fraction of the aggregate is 1162-2484 parts, preferably 1245-2070 parts, more preferably 1337-1656 parts, for example 1400 parts, 1517 parts or 1654 parts; (2) the mass fraction of the mineral powder is 112-246 parts, preferably 120-205 parts, more preferably 128-164 parts, for example 138 parts, 150 parts or 164 parts.

4. The asphalt mixture of claim 1, wherein, The raw materials of the asphalt mixture satisfy one or more of the following conditions: (1) in the mineral aggregate, the mass percentage of the aggregate with a particle size of 0-3 mm is 14.5%-15%, for example 15%; (2) the mass percentage of aggregate with particle size of 3-5 mm in the mineral aggregate is 5%-6%, for example, 5%; (3) the mass percentage of aggregate with particle size of 5-10 mm in the mineral aggregate is 37.5%-38%, for example, 38%; (4) the mass percentage of aggregate with particle size of 10-15 mm in the mineral aggregate is 33%-33.5%, for example, 33%; and (5) the particle size specification of the mineral powder in the mineral aggregate includes the following: 0.6 mm sieve pass rate of 100%, 0.15 mm sieve pass rate of 90-100%, and 0.075 mm sieve pass rate of 75-100%; preferably, 0.6 mm sieve pass rate of 100%, 0.15 mm sieve pass rate of 98.2%, and 0.075 mm sieve pass rate of 88.3%.

5. The asphalt mixture of claim 1, wherein, The raw materials of the asphalt mixture satisfy one or more of the following conditions: (1) the penetration of the base asphalt is 60-80 / 0.1 mm, for example, 71 / 0.1 mm; (2) the softening point of the base asphalt is ≥46℃, for example, 46-55℃; (3) the ductility of the base asphalt is ≥20 cm; (4) the ash content of the rock asphalt is ≤15%, for example, 10% or 7.9%; (5) the asphalt content of the rock asphalt is ≥80%, preferably, 81%-95%, for example, 91.8%; (6) the softening point of the rock asphalt is 180-200℃, preferably, 182-195℃, for example, 185℃; (7) the rock asphalt has a density of 1-2 g / cm 3 , preferably 1.05-1.5 g / cm 3 , for example 1.06 g / cm 3 ; (8) the water content of the rock asphalt is <1%, preferably, <0.8%, for example, <0.5%; (9) the particle size of the devulcanized rubber is 30-50 mesh, for example, 40 mesh; (10) the sol content of the devulcanized rubber is >50%, preferably, 58%-65%, for example, 62.1%; (11) the Mooney viscosity of the devulcanized rubber is <40%, preferably, 25%-35%, for example, 29.5%; (12) the aggregate is fine aggregate and / or coarse aggregate; the fine aggregate is preferably limestone; the coarse aggregate is preferably limestone and / or basalt; the fine aggregate means aggregate with particle size <2.36 mm; the coarse aggregate means aggregate with particle size >2.36 mm; and (13) the mineral powder is limestone mineral powder.

6. The asphalt mixture of claim 1, wherein, The asphalt mixture satisfies the following conditions (1) and / or (2): (1) the gradation type of the asphalt mixture is SMA or AC; wherein, when the gradation type of the asphalt mixture is SMA, the raw materials of the asphalt mixture further include fibers; the type of the fibers is preferably lignin fibers or polyester fibers; the mass of the fibers is preferably 0.3% of the mass of the mineral aggregate; (2) the void ratio of the asphalt mixture is 3%-4%, for example, 3.5%.

7. A method of producing an asphalt mixture as claimed in any one of claims 1-6, characterized in that, This is achieved by the following method: the preheated base asphalt and aggregate are mixed for the first time, then mixed with the rock asphalt for the second time, then mixed with the devulcanized rubber for the third time, and then mixed with the mineral powder for the fourth time, and developed; the time of the first mixing is 20-40 s; the second mixing time is 20-40 seconds; the third mixing time is 20-40 seconds; the fourth mixing time is 20-40 seconds.

8. The method for producing an asphalt mixture according to claim 7, wherein when the raw materials of the asphalt mixture further contain fibers, the fibers are added at the fourth mixing.

9. Use of the asphalt mixture according to any one of claims 1 to 6 in the field of road construction.

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