CN110904764A - Mix proportion design method of ultrathin wearing layer asphalt mixture - Google Patents
Mix proportion design method of ultrathin wearing layer asphalt mixture Download PDFInfo
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Abstract
The invention discloses a mix proportion design method of an asphalt mixture of an ultrathin wearing layer, and relates to the technical field of road engineering. The method comprises the following steps: s1, setting road performance indexes according to original road surface factors; s2, selecting the raw materials of the ultra-thin wearing layer asphalt mixture to comprise asphalt and mineral aggregate according to the pavement performance index of S1, and S3, determining the gradation of the mineral aggregate; s4, determining the oilstone ratio; s5, preparing an ultra-thin wearing layer asphalt mixture according to the mineral aggregate usage ratio and the oilstone ratio of S3 and S4, and determining whether the pavement performance index in S1 meets the set pavement performance index, namely completing the design of the mix proportion of the ultra-thin wearing layer asphalt mixture. The invention determines the optimal mineral aggregate gradation and the optimal oilstone ratio through high-temperature performance, low-temperature crack resistance and water stability, and can select proper gradation types to be applied to actual engineering according to different functions, grades, pavement design requirements and the like of the original road conditions.
Description
Technical Field
The invention relates to the technical field of road engineering, in particular to a mix proportion design method of an asphalt mixture of an ultrathin wearing layer.
Background
Along with the rapid pavement of expressways in China, road surface layers paved by asphalt mixtures are widely applied due to the characteristics of stable driving, comfort, no dust, small vibration, low noise and the like, asphalt roads generally adopt semi-rigid base asphalt pavement structures, and the asphalt surface layers mainly play a role of functional layers rather than a role of bearing, so that in recent years, along with the improvement of living standard of people, the rapid development of various industries, particularly the rapid development of the transportation industry, and tests on the bearing and the durability of the roads are brought.
At present, in order to enable the road surface to be used for a long time, the noise is low, the drainage is facilitated, the safety is high and the like, an ultrathin wearing layer asphalt mixture is often adopted to improve the function of the road surface, the function recovery and correction of the ultrathin wearing layer asphalt mixture on the road surface are superior to those of a common asphalt mixture, the ultrathin wearing layer asphalt mixture is a durable surface layer, and the ultrathin wearing layer asphalt mixture has good performances of skid resistance, abrasion resistance, rutting resistance and water damage resistance, so that the design of the mixing ratio of the ultrathin wearing layer asphalt mixture directly influences the application value of the ultrathin wearing layer asphalt mixture in road engineering.
Throughout the country and abroad, methods for designing the mix proportion of the ultrathin asphalt wearing layer in the prior art are commonly used, such as a marshall method, a vim method, a Superpave method, a GTM method and the like, but the marshall method is most widely used; according to the technical Specification for constructing asphalt road surfaces of roads (JTG F40-2017) in China, a Marshall method is adopted for designing the mixing ratio of the asphalt mixture; however, due to the use requirements of road surfaces, the conditions of the original road surfaces, traffic volume, weather conditions and the influence of raw materials, people usually adopt other methods to design the mix proportion of the asphalt mixture of the ultra-thin wearing layer on the basis of the existing design method, but still have limitations in the use process, particularly the temperature is low in winter, the road surface is very easy to freeze, the shearing strength between the ultra-thin wearing layers is easy to reduce, the water stability is poor, the crack resistance is weakened, the rutting is easy to loosen and strip, and similarly, the pavement softening phenomenon is enhanced in high-temperature weather, the shearing strength between the ultra-thin wearing layers is also easy to reduce, and the driving safety performance of the ultra-thin wearing layer is influenced.
Disclosure of Invention
The invention provides a mix proportion design method of an asphalt mixture of an ultra-thin wearing layer, which solves the problems that in the prior art, the shearing strength between layers of the ultra-thin wearing layer is reduced, the water stability is poor, the anti-cracking performance is weakened, and the ruts are easy to loosen and peel off due to low temperature or high temperature weather in winter.
The invention provides a mix proportion design method of an asphalt mixture of an ultra-thin wearing layer, which comprises the following steps:
s1, determining road performance indexes according to original road surface factors; the pavement performance indexes comprise high-temperature performance, low-temperature crack resistance and water stability;
s2, selecting raw materials of the ultra-thin wearing layer asphalt mixture to comprise asphalt and mineral aggregates according to the pavement performance index of S1, wherein the mineral aggregates comprise coarse aggregates, fine aggregates and fillers, and measuring physical performance parameters of the coarse aggregates, the fine aggregates and the fillers respectively;
s3, determining mineral aggregate gradation according to the physical performance parameters of the coarse aggregate, the fine aggregate and the filler in the S2, and determining mineral aggregate mixing proportion according to the mineral aggregate gradation;
s4, determining the total surface area of the mineral aggregate through the mineral aggregate grading in S3, and determining the oilstone ratio by combining the mineral aggregate proportion;
s5, preparing an ultra-thin wearing layer asphalt mixture according to the mineral aggregate gradation and the oilstone ratio respectively determined by S3 and S4, determining whether the pavement performance index in S1 meets the set pavement performance index, and if the pavement performance index in S1 does not meet the set pavement performance index, returning to S3 for redesign; and if the mineral aggregate grading is the optimal grading, S3, and S4, the oilstone ratio is the optimal oilstone ratio, so that the mix proportion design of the ultrathin wearing layer asphalt mixture is completed.
Further, the original road surface factors comprise road grade, climate conditions and traffic load capacity.
Furthermore, the technical indexes of the asphalt, the coarse aggregate, the fine aggregate and the filler all meet the regulations of technical Specifications for road asphalt pavement construction (JTGF 40-2017).
Further, the asphalt is modified asphalt.
Further, the road performance index is tested according to the requirements of road engineering asphalt and asphalt mixture test regulations (JTGE 20-2011).
Compared with the prior art, the invention has the beneficial effects that:
according to the mix proportion design method of the ultra-thin wearing layer asphalt mixture, firstly, the road performance index of the ultra-thin wearing layer asphalt mixture to be paved is set through the road grade, the climate condition, the traffic load and other original road surface factors, the mix proportion design direction of the ultra-thin wearing layer asphalt mixture is determined, and the selection requirement of raw materials is determined. The optimal mineral aggregate gradation and the optimal oilstone ratio are determined through high-temperature performance, low-temperature crack resistance and water stability, and the proper gradation type can be selected and applied to actual engineering according to different functions, grades, pavement design requirements and the like of the original road conditions.
The method comprises the steps of determining and calculating physical performance parameters of selected mineral aggregates comprising coarse aggregates, fine aggregates and fillers, determining the dosage ratio of the fine aggregates by combining the void ratio of the coarse aggregates with the apparent density of the fine aggregates on the basis of determined gradation, determining the dosage ratio of the fillers by combining the void ratio of the fine aggregates with the apparent density of the fillers, determining the oilstone ratio by combining the determined dosage ratios of the coarse aggregates, the fine aggregates and the fillers, determining the apparent density of the mineral aggregates, and finally determining the optimal gradation and the optimal oilstone ratio by mixing the asphalt mixture and performing a performance test. The invention provides a new design idea of the ultra-thin wearing layer asphalt mixture, can fully utilize the utilization rate of the aggregate, and can further try out the optimal mineral aggregate gradation and the optimal oilstone ratio according to different aggregates.
Detailed Description
In order to make the technical solutions of the present invention better understood and enable those skilled in the art to practice the present invention, the following embodiments are further described, but the present invention is not limited to the following embodiments.
The embodiment provides a mix proportion design method of an asphalt mixture of an ultra-thin wearing layer, which specifically comprises the following steps:
s1, setting road performance indexes according to original road factors including road grade, climate conditions and traffic load; including high temperature performance, low temperature crack resistance, and water stability, the road performance index was selected according to the rules of the empirical road asphalt pavement construction technical Specification (JTGF40-2017), as shown in Table 1 below,
TABLE 1 road Performance index selected based on the original road surface factors
S2, selecting the raw materials of the ultra-thin wearing layer asphalt mixture to comprise asphalt and mineral aggregates according to the pavement performance index of S1, wherein the mineral aggregates comprise coarse aggregates, fine aggregates and fillers; and respectively measuring physical performance parameters of the coarse aggregate, the fine aggregate and the filler;
as can be seen from Table 1, the road performance index of the heavy-duty traffic road surface of the expressway is analyzed from the set road performance, and according to the requirements of technical Specification for constructing asphalt road surfaces of highways (JTGF40-2017), the selected asphalt has a 60 ℃ dynamic year of not less than 200 and a higher softening point than that of common asphalt, and meanwhile, the selected coarse aggregate has a particle size specification meeting a crushing value of not more than 26% and a firmness of not more than 12%; the firmness of the selected fine aggregate is not less than 12%, therefore, the selection of the raw materials is crucial to the design of the mix proportion of the asphalt mixture of the ultra-thin wearing layer, the asphalt and the mineral aggregate can be effectively and reasonably selected under the requirement of road performance indexes, and the specific index parameters are as follows:
the invention selects high-viscosity high-elasticity modified asphalt, and the engineering technical indexes are shown in table 2;
TABLE 2 technical indexes of high-viscosity high-elasticity modified asphalt
Selecting coarse aggregates and fine aggregates, wherein the engineering technical indexes of the coarse aggregates are shown in table 3, the specifications of the coarse aggregates for the asphalt mixture are shown in table 4, the engineering technical indexes of the fine aggregates are shown in table 5, and the specifications of the fine aggregates for the asphalt mixture are shown in table 6;
TABLE 3 coarse aggregate engineering specifications
TABLE 4 coarse aggregate specification for asphalt mixture
TABLE 5 Fine aggregate engineering specifications
TABLE 6 Fine aggregate Specification for asphalt mixtures
The filler used in the asphalt mixture is tailings obtained by grinding the raw rock in the process of producing machine-made sand by using a dry vertical shaft sand making machine, namely the selected filler, and the quality of the filler meets the requirements of technical Specification for road asphalt pavement construction (JTGF 40-2017).
S3, determining mineral aggregate gradation according to the physical performance parameters of the coarse aggregate, the fine aggregate and the filler in the S2, and setting mineral aggregate mixing proportion according to the mineral aggregate gradation;
according to the regulations of the technical Specification for constructing asphalt road surfaces for highways (JTGF40-2017), the mineral aggregate gradation of the ultra-thin wearing layer adopts discontinuous gradation, the thickness of the ultra-thin wearing layer serving as a road surface is generally 10-20 mm, and the gradation ranges of three groups of mineral aggregates are preliminarily determined according to the mineral aggregates of the mixture of the ultra-thin wearing layer according to the maximum grain size of the project and the specifications of selecting coarse aggregates, fine aggregates and fillers, such as the gradation range of the mixture of the ultra-thin wearing layer shown in the table 7.
TABLE 7 ultra-thin wearing course mixture mineral aggregate gradation range
The mineral aggregate mixture ratio is set according to the mineral aggregate gradation as follows: coarse aggregate: fine aggregate: (iii) filler (55-70): (15-25): (3-7);
s4, determining the total surface area of the mineral aggregate through the mineral aggregate grading in S3, and determining the oilstone ratio by combining the mineral aggregate proportion;
calculating the total surface area A of the mineral aggregate according to the following formula, and determining the initial consumption of asphalt, so as to select the initial oilstone ratio according to the apparent density of the mineral aggregate;
A＝0.41+0.41a+0.82b+1.64c+2.87d+6.14e+12.29f+32.77g(m2/kg)
in the formula: a. b, c, d, e, f and g are respectively expressed by the passing rates of 4.75mm, 2.36mm, 1.18mm, 0.6mm, 0.3mm, 0.15mm and 0.075mm sieve pores.
According to formula PbCalculating the initial asphalt dosage h multiplied by A, wherein the ultrathin wearing layer is selected from high-viscosity high-elasticity modified asphalt, and the thickness of the asphalt film is not less than 10 mu m.
And selecting the initial oilstone ratio to be 4.5-6.5% according to the specification of the selected mixture and the calculated initial asphalt using amount, the total surface area of the mineral aggregate and practical experience.
S5, preparing the ultra-thin wearing layer asphalt mixture according to the mineral aggregate gradation and the oilstone ratio respectively determined by S3 and S4, determining whether the pavement performance index in S1 meets the set pavement performance index, if not, returning to S3 for redesign, if so, setting the mineral aggregate gradation as the optimal gradation and setting the oilstone ratio S4 as the optimal oilstone ratio, and thus completing the mix proportion design of the ultra-thin wearing layer asphalt mixture.
The method for designing the mix proportion of the asphalt mixture of the ultra-thin wearing layer is further described below with reference to specific examples.
Example 1
S1, setting the road performance indexes as follows, wherein the road grade of the original road surface in the original place in China is an expressway, the weather conditions are summer hot area and winter cold area, the traffic load is heavy traffic, and the road performance indexes are as follows:
high temperature performance: marshall stability is not less than 6.0 KN; the dynamic stability of the rut test is not less than 2800 times/mm;
low-temperature crack resistance: low temperature bending failure strain no less than 2500;
water stability: the residual Marshall stability ratio is not less than 85%; the freeze-thaw splitting residual strength ratio is not less than 85%; leakage loss is not more than 0.3%; the water immersion flying loss is not more than 20%;
s2, selecting the raw materials of the ultra-thin wearing layer asphalt mixture to comprise asphalt and mineral aggregates according to the pavement performance index of S1, wherein the mineral aggregates comprise coarse aggregates, fine aggregates and fillers; the physical property parameters of coarse aggregate, fine aggregate and filler are respectively measured by the requirements of road engineering asphalt and asphalt mixture test regulations (JTGE 20-2011).
In the embodiment, the high-viscosity high-elasticity modified asphalt is selected, and the engineering technical indexes are shown in the table 1-1.
TABLE 1-1 technical indices of Properties of high-viscosity high-elasticity modified asphalt
| Index (I) | Unit of | Test value |
| Penetration (25 ℃,5s,100g) | 0.1mm | 51 |
| Penetration index PI | / | -0.1 |
| Softening point (R)&B) | ℃ | 80 |
| Dynamic viscosity at 60 DEG C | Pa.s | 400 |
| Ductility at 5 DEG C | cm | 41 |
| Flash point | ℃ | 360 |
| Solubility in water | ％ | 99.8 |
| Elastic recovery (25 ℃ C.) | ％ | 98 |
| Density (15 ℃ C.) | g/cm3 | 1.1 |
| Change in mass | ％ | 0.6 |
| Residual penetration ratio | ％ | 80 |
| Residual ductility (5 ℃ C.) | cm | 31.5 |
In the embodiment, basalt coarse aggregates and basalt machine-made sand fine aggregates are respectively selected, wherein the engineering technical indexes of the coarse aggregates are shown in tables 1-2, the specifications of the coarse aggregates for asphalt mixtures are shown in tables 1-3, the engineering technical indexes of the fine aggregates are shown in tables 1-4, and the specifications of the fine aggregates for asphalt mixtures are shown in tables 1-5.
TABLE 1-2 basalt coarse aggregate engineering technical indexes
TABLE 1-3 coarse aggregate Specifications for asphalt mixtures
TABLE 1-4 basalt machine-made sand fine aggregate engineering technical indexes
| Index (I) | Unit of | Test value |
| Apparent relative density | t/m3 | 2.8 |
| Firmness (>0.3mm part) | ％ | 17 |
| Mud content (content less than 0.075 mm) | ％ | 1 |
| Sand equivalent | ％ | 65 |
| Methylene blue value | g/kg | 10 |
| Angular character (flow time) | s | 38 |
TABLE 1-5 Fine aggregate Specifications for asphalt mixtures
The filler used in the embodiment is tailings obtained by grinding in the process of producing machine-made sand by using a dry vertical shaft sand making machine through basalt, namely the selected filler, and the quality of the filler meets the requirements of technical Specification for road asphalt pavement construction (JTGF 40-2017); the specifications are shown in tables 1-6.
TABLE 1-6 Filler Specification for asphalt mixtures
S3, selecting mineral aggregate gradation according to the physical performance parameters of the coarse aggregate, the fine aggregate and the filler in S2, adopting discontinuous gradation according to the specification of technical Specification for construction of road asphalt pavement (JTGF40-2017), wherein the thickness of the ultra-thin wearing layer serving as the pavement is generally 10-20 mm, and preliminarily determining three groups of mineral aggregate gradation according to the maximum engineering particle size of the mineral aggregate of the ultra-thin wearing layer mixture and the specifications of the selected coarse aggregate, fine aggregate and filler, as shown in tables 1-7.
TABLE 1-7 three-group mineral aggregate gradation of ultra-thin wearing layer mixture
The mineral aggregate mixture ratio is set according to the mineral aggregate gradation as follows: coarse aggregate: fine aggregate: filler 66: 20: 5
S4, determining the total surface area of the mineral aggregate through the mineral aggregate grading in S3, and determining the oilstone ratio through the total surface area of the mineral aggregate;
calculating the total surface area A of the mineral aggregate according to the following formula, and determining the initial consumption of asphalt, so as to select the initial oilstone ratio according to the apparent density of the mineral aggregate;
A＝0.41+0.41a+0.82b+1.64c+2.87d+6.14e+12.29f+32.77g(m2/kg)
in the formula: a. b, c, d, e, f and g are respectively expressed by the passing rates of 4.75mm, 2.36mm, 1.18mm, 0.6mm, 0.3mm, 0.15mm and 0.075mm sieve pores.
According to formula PbCalculating the initial asphalt dosage h multiplied by A, wherein the ultrathin wearing layer is selected from high-viscosity high-elasticity modified asphalt, and the thickness of the asphalt film is not less than 10 mu m.
Selecting three initial oilstone ratios of 4.5%, 5.5% and 6.5% according to the specification of the selected mixture and the calculated initial asphalt dosage, the total surface area of the mineral aggregate and practical experience;
s5, preparing the ultra-thin wearing layer asphalt mixture according to the mineral aggregate gradation and the oilstone ratio respectively determined by S3 and S4, determining whether the pavement performance index in S1 meets the set pavement performance index, if not, returning to S3 for redesign, if so, determining that the mineral aggregate gradation is the optimal gradation and the oilstone ratio S4 is the optimal oilstone ratio, namely, completing the mix proportion design of the ultra-thin wearing layer asphalt mixture, and the following tables 1-8 meet the analysis of the pavement performance index.
Tables 1-8 road Performance test analysis
Example 2
S1, setting the road performance indexes as follows, wherein the road grade of the original road surface in a certain place in southwest of China is a first-grade road, the weather conditions are summer hot area and winter cold, the traffic load is heavy traffic, and the road performance indexes are as follows:
high temperature performance: marshall stability not less than 5.5 KN; the dynamic stability of the rut test is not less than 2400 times/mm;
low-temperature crack resistance: low temperature bending failure strain no less than 2500;
water stability: the residual Marshall stability ratio is not less than 80%; the ratio of the freeze-thaw splitting residual strength is not less than 80%; leakage loss is not more than 0.3%; the water immersion flying loss is not more than 20%;
s2, selecting the raw materials of the ultra-thin wearing layer asphalt mixture to comprise asphalt and mineral aggregates according to the pavement performance index of S1, wherein the mineral aggregates comprise coarse aggregates, fine aggregates and fillers; the physical property parameters of coarse aggregate, fine aggregate and filler are respectively measured by the requirements of road engineering asphalt and asphalt mixture test regulations (JTGE 20-2011).
In the present example, a high-viscosity high-elasticity modified asphalt is selected, and the engineering technical index is shown in table 2-1.
TABLE 2-1 technical indexes of high-viscosity high-elasticity modified asphalt
| Index (I) | Unit of | Test value |
| Penetration (25 ℃,5s,100g) | 0.1mm | 51 |
| Penetration index PI | / | -0.1 |
| Softening point (R)&B) | ℃ | 80 |
| Dynamic viscosity at 60 DEG C | Pa.s | 400 |
| Ductility at 5 DEG C | cm | 41 |
| Flash point | ℃ | 360 |
| Solubility in water | ％ | 99.8 |
| Elastic recovery (25 ℃ C.) | ％ | 98 |
| Density (15 ℃ C.) | g/cm3 | 1.1 |
| Change in mass | ％ | 0.6 |
| Residual penetration ratio | ％ | 80 |
| Residual ductility (5 ℃ C.) | cm | 31.5 |
In the present example, diabase coarse aggregate and diabase machine-made sand fine aggregate are selected, wherein the engineering technical indexes of the coarse aggregate are shown in table 2-2, the specifications of the coarse aggregate for asphalt mixture are shown in table 2-3, the engineering technical indexes of the fine aggregate are shown in table 2-4, and the specifications of the fine aggregate for asphalt mixture are shown in table 2-5.
TABLE 2-2 diabase coarse aggregate engineering technical indexes
TABLE 2-3 coarse aggregate specification for asphalt mixtures
TABLE 2-4 technical indexes of diabase machine-made sand fine aggregate engineering
| Index (I) | Unit of | Test value |
| Apparent relative density | t/m3 | 2.7 |
| Firmness (>0.3mm part) | ％ | 18 |
| Mud content (content less than 0.075 mm) | ％ | 1.3 |
| Sand equivalent | ％ | 66 |
| Methylene blue value | g/kg | 10 |
| Angular character (flow time) | s | 37 |
TABLE 2-5 Fine aggregate Specifications for asphalt mixtures
The filler used in the embodiment is tailings obtained by grinding in the process of producing machine-made sand by using a dry vertical shaft sand making machine through diabase, namely the selected filler, and the quality of the filler meets the requirements of technical Specification for road asphalt pavement construction (JTGF 40-2017); the specifications are shown in tables 2-6.
TABLE 2-6 Filler Specification for asphalt mixtures
S3, selecting mineral aggregate gradation according to the physical performance parameters of the coarse aggregate, the fine aggregate and the filler in S2, adopting discontinuous gradation according to the specification of technical Specification for construction of road asphalt pavement (JTGF40-2017), wherein the thickness of the ultra-thin wearing layer serving as the pavement is generally 10-20 mm, and preliminarily determining three groups of mineral aggregate gradation according to the maximum engineering particle size of the mineral aggregate of the ultra-thin wearing layer mixture and the specifications of the selected coarse aggregate, fine aggregate and filler, as shown in tables 2-7.
TABLE 2-7 three-group mineral aggregate gradation of ultra-thin wearing layer mixture
The mineral aggregate mixture ratio is set according to the mineral aggregate gradation as follows: coarse aggregate: fine aggregate: filler 55: 15: 3
S4, determining the total surface area of the mineral aggregate through the mineral aggregate grading in S3, and determining the oilstone ratio through the total surface area of the mineral aggregate;
calculating the total surface area A of the mineral aggregate according to the following formula, and determining the initial consumption of asphalt, so as to select the initial oilstone ratio according to the apparent density of the mineral aggregate;
A＝0.41+0.41a+0.82b+1.64c+2.87d+6.14e+12.29f+32.77g(m2/kg)
in the formula: a. b, c, d, e, f and g are respectively expressed by the passing rates of 4.75mm, 2.36mm, 1.18mm, 0.6mm, 0.3mm, 0.15mm and 0.075mm sieve pores.
According to formula PbCalculating the initial asphalt consumption, wherein the ultra-thin wearing layer is high-viscosity high-elasticity modified asphalt, and the thickness of the selected asphalt film is not less than 10 mu m;
selecting three initial oilstone ratios of 4.5%, 5.5% and 6.5% according to the specification of the selected mixture and the calculated initial asphalt dosage, the total surface area of the mineral aggregate and practical experience;
s5, preparing the ultra-thin wearing layer asphalt mixture according to the mineral aggregate gradation and the oilstone ratio respectively determined by S3 and S4, determining whether the pavement performance index in S1 meets the set pavement performance index, if not, returning to S3 for redesign, if so, determining that the mineral aggregate gradation is the optimal gradation and the oilstone ratio S4 is the optimal oilstone ratio, namely, completing the mix proportion design of the ultra-thin wearing layer asphalt mixture, and the following tables 2-8 meet the analysis of the pavement performance index.
Tables 2-8 road Performance test data
Example 3
S1, setting the road performance indexes as follows, wherein the original road grade of the southeast of China is a first-grade road, the weather conditions are summer inflammatory hot areas and winter cold areas, the traffic capacity is medium-light traffic, and the road performance indexes are as follows:
high temperature performance: marshall stability not less than 5.5 KN; the dynamic stability of the rut test is not less than 2400 times/mm;
low-temperature crack resistance: low temperature bending failure strain of not less than 2000;
water stability: the residual Marshall stability ratio is not less than 80%; the ratio of the freeze-thaw splitting residual strength is not less than 80%; leakage loss is not more than 0.3%; the water immersion flying loss is not more than 20%;
s2, selecting the raw materials of the ultra-thin wearing layer asphalt mixture to comprise asphalt and mineral aggregates according to the pavement performance index of S1, wherein the mineral aggregates comprise coarse aggregates, fine aggregates and fillers; the physical property parameters of coarse aggregate, fine aggregate and filler are respectively measured by the requirements of road engineering asphalt and asphalt mixture test regulations (JTGE 20-2011).
In the present example, a high-viscosity high-elasticity modified asphalt is selected, and the engineering technical index is shown in table 3-1.
TABLE 3-1 technical indices of high-viscosity high-elasticity modified asphalt Properties
In the embodiment, limestone coarse aggregates and limestone machine-made sand fine aggregates are respectively selected, wherein the technical indexes of coarse aggregate engineering are shown in a table 3-2, the specifications of coarse aggregates for asphalt mixtures are shown in a table 3-3, the technical indexes of fine aggregate engineering are shown in a table 3-4, and the specifications of fine aggregates for asphalt mixtures are shown in a table 3-5.
TABLE 3-2 limestone coarse aggregate engineering technical indexes
TABLE 3-3 coarse aggregate Specifications for asphalt mixtures
TABLE 3-4 technical indexes of fine aggregate engineering for limestone machine-made sand
| Index (I) | Unit of | Test value |
| Apparent relative density | t/m3 | 2.8 |
| Firmness (>0.3mm part) | ％ | 20 |
| Mud content (content less than 0.075 mm) | ％ | 2.0 |
| Sand equivalent | ％ | 70 |
| Methylene blue value | g/kg | 15 |
| Angular character (flow time) | s | 35 |
TABLE 3-5 Fine aggregate Specifications for asphalt mixtures
The filler used in the embodiment is tailings obtained by grinding in the process of producing machine-made sand by using a dry vertical shaft sand making machine through limestone, namely the selected filler, and the quality of the filler meets the requirements of technical Specification for road asphalt pavement construction (JTGF 40-2017); the specifications are shown in tables 3-6.
TABLE 3-6 Filler Specification for asphalt mixtures
S3, selecting mineral aggregate gradation according to the physical performance parameters of the coarse aggregate, the fine aggregate and the filler in S2, adopting discontinuous gradation according to the specification of technical Specification for construction of road asphalt pavement (JTGF40-2017), wherein the thickness of the ultra-thin wearing layer serving as the pavement is generally 10-20 mm, and preliminarily determining three groups of mineral aggregate gradation according to the maximum engineering particle size of the mineral aggregate of the ultra-thin wearing layer mixture and the specifications of the selected coarse aggregate, fine aggregate and filler, as shown in tables 3-7.
TABLE 3-7 three-group mineral aggregate gradation of ultra-thin wearing layer mixture
The mineral aggregate mixture ratio is set according to the mineral aggregate gradation as follows: coarse aggregate: fine aggregate: 70 parts of filler: 25: 7
S4, determining the total surface area of the mineral aggregate through the mineral aggregate grading in S3, and determining the oilstone ratio through the total surface area of the mineral aggregate;
calculating the total surface area A of the mineral aggregate according to the following formula, and determining the initial consumption of asphalt, so as to select the initial oilstone ratio according to the apparent density of the mineral aggregate;
A＝0.41+0.41a+0.82b+1.64c+2.87d+6.14e+12.29f+32.77g(m2/kg)
in the formula: a. b, c, d, e, f and g are respectively expressed by the passing rates of 4.75mm, 2.36mm, 1.18mm, 0.6mm, 0.3mm, 0.15mm and 0.075mm sieve pores.
According to formula PbCalculating the initial asphalt consumption, wherein the ultra-thin wearing layer is high-viscosity high-elasticity modified asphalt, and the thickness of the selected asphalt film is not less than 10 mu m;
selecting three initial oilstone ratios of 4.5%, 5.5% and 6.5% according to the specification of the selected mixture and the calculated initial asphalt dosage, the total surface area of the mineral aggregate and practical experience;
s5, preparing the ultra-thin wearing layer asphalt mixture according to the mineral aggregate gradation and the oilstone ratio respectively determined by S3 and S4, determining whether the pavement performance index in S1 meets the set pavement performance index, if not, returning to S3 for redesign, if so, setting the mineral aggregate gradation as the optimal gradation and setting the oilstone ratio S4 as the optimal oilstone ratio, and thus completing the mix proportion design of the ultra-thin wearing layer asphalt mixture; the following tables 3-8 satisfy the analysis of the road performance indicators.
Tables 3-8 road Performance test data
The mix proportion of the ultra-thin wearing layer asphalt mixture is designed by the mix proportion design method of the ultra-thin wearing layer asphalt mixture respectively provided by the embodiments 1 to 3, and the pavement performance index of the ultra-thin wearing layer asphalt mixture to be paved is set according to the road grade, the climate condition, the traffic load and other original road surface factors, so that the mix proportion design direction of the ultra-thin wearing layer asphalt mixture is determined, and the selection requirement of raw materials is determined.
The optimal mineral aggregate gradation and the optimal oilstone ratio range are determined to be 4.5-6.5% through high-temperature performance, low-temperature crack resistance and water stability, and the appropriate gradation type can be selected and applied to actual engineering according to different functions, grades, pavement design requirements and the like of the original road condition.
In addition, the embodiment 1-3 select representative aggregates, select different coarse and fine aggregates according to different original road surface factors, can make full use of the utilization rate of the aggregates, and can further try out the optimal mineral aggregate gradation and the optimal oilstone ratio according to different aggregates.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.
Claims (5)
1. A mix proportion design method of an asphalt mixture of an ultrathin wearing layer is characterized by comprising the following steps:
s1, determining road performance indexes according to original road surface factors; the pavement performance indexes comprise high-temperature performance, low-temperature crack resistance and water stability;
s2, selecting raw materials of the ultra-thin wearing layer asphalt mixture to comprise asphalt and mineral aggregates according to the pavement performance index of S1, wherein the mineral aggregates comprise coarse aggregates, fine aggregates and fillers, and measuring physical performance parameters of the coarse aggregates, the fine aggregates and the fillers respectively;
s3, determining mineral aggregate gradation according to the physical performance parameters of the coarse aggregate, the fine aggregate and the filler in the S2, and determining mineral aggregate mixing proportion according to the mineral aggregate gradation;
s4, determining the total surface area of the mineral aggregate through the mineral aggregate grading in S3, and determining the oilstone ratio by combining the mineral aggregate mixing ratio;
s5, preparing an ultra-thin wearing layer asphalt mixture according to the mineral aggregate gradation and the oilstone ratio respectively determined by S3 and S4, determining whether the pavement performance index in S1 meets the set pavement performance index, and if the pavement performance index in S1 does not meet the set pavement performance index, returning to S3 for redesign; and if the mineral aggregate grading is the optimal grading, S3, and S4, the oilstone ratio is the optimal oilstone ratio, so that the mix proportion design of the ultrathin wearing layer asphalt mixture is completed.
2. The method for designing the mix proportion of the asphalt mixture for the ultra-thin wearing layer according to claim 1, wherein the original pavement factors include road grade, climate conditions, and traffic load.
3. The mix proportion design method of the ultra-thin wearing layer asphalt mixture as claimed in claim 1, wherein the technical indexes of the asphalt, the coarse aggregate, the fine aggregate and the filler are all in accordance with the specification of technical Specification for road asphalt pavement construction (JTGF 40-2017).
4. The method for designing the mix proportion of the asphalt mixture for the ultra-thin wearing layer according to claim 1, wherein the asphalt is modified asphalt.
5. The method for designing the mix proportion of the asphalt mixture for the ultra-thin wearing layer according to claim 1, wherein the road performance index is tested according to the test specification for road engineering asphalt and asphalt mixture (JTG E20-2011).
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| CN114330008A (en) * | 2021-12-31 | 2022-04-12 | 河北省交通规划设计研究院有限公司 | Low-freezing-point ultra-thin wearing layer grading range determination method applied to road surface |
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