CN107572896B - A Design Method of AC-20 Modified Asphalt Mixture Based on Pavement Performance - Google Patents

Abstract

The invention belongs to the technical field of road engineering, in particular to an AC-20 modified asphalt mixture design method based on road performance. According to the characteristics of climate, traffic and materials in Northeast China, through a large number of road performance tests, using fractal theory to establish asphalt mixture road performance prediction model and gradation inspection prediction model; referring to the requirements in the current specifications, put forward the asphalt pavement in Northeast China The fractal dimension of asphalt mixture aggregate gradation and the range of coarse and fine aggregate fractal dimension that meet the road performance requirements; select the corresponding fractal dimension as the design parameter within the proposed range, and deduce the ore through the fractal dimension Through the pass rate of each sieve hole, the road performance test of asphalt mixture is carried out through the established road performance prediction model, and the gradation skeleton test is carried out by using the gradation test prediction model. Finally, the asphalt mixture meeting the prediction performance requirements is tested and verified. , and then get a good gradation that meets the performance requirements.

Description

A Design Method of AC-20 Modified Asphalt Mixture Based on Pavement Performance

technical field

The invention belongs to the technical field of road engineering, in particular to an AC-20 modified asphalt mixture design method based on road performance.

Background technique

For a long time, the mix design method of asphalt mixture has been the research focus of road researchers and builders. At present, most countries in the world adopt the Marshall method to design asphalt mixture, and my country is no exception. However, after many years of engineering practice, people have gradually realized that there are many shortcomings in the Marshall test method, such as the difference between the test piece forming and the actual construction process, the test piece forming method cannot simulate the driving compaction, and cannot reflect, optimize and predict the road surface. Performance, etc. Although all the indicators of the Marshall test meet the requirements of the specification, the road performance is poor and the rutting and other diseases are serious.

Contents of the invention

In view of the above-mentioned technical problems, the present invention provides a design method of AC-20 modified asphalt mixture based on road performance, which links the design method of asphalt mixture with road performance, and reduces unnecessary tests by optimizing the design quantity.

Technical scheme of the present invention is:

A design method of AC-20 modified asphalt mixture based on road performance, the process of the design method is as follows:

(1) Through the high temperature, low temperature and water stability test research on AC-20 modified asphalt mixture, the fractal structure model of asphalt mixture and its aggregate internal voids was established by using fractal theory, and the fractal structure for characterizing the mixture and its aggregate voids was proposed Based on the characteristic parameters, the road performance prediction model and gradation inspection prediction model of AC-20 modified asphalt mixture are established;

(2) Within the scope of the fractal dimension of asphalt mixture aggregate gradation and the fractal dimension of coarse aggregate and fine aggregate that meet the road performance requirements, select the corresponding fractal dimension as the design parameter, and deduce it through the fractal dimension The passing rate of each sieve hole of the mineral material is used to test the road performance of the asphalt mixture through the road performance prediction model established, and the gradation skeleton inspection is carried out using the gradation test prediction model, and finally the asphalt mixture that meets the prediction performance requirements is tested Verification, and then get a good gradation that meets the performance requirements.

The described AC-20 modified asphalt mixture design method based on road performance specifically comprises the following steps:

(1) Select the fractal dimension

The ranges of fractal dimensions D, D _C and D _f for the gradation of AC-20 modified asphalt mixture to meet road performance requirements are:

The fractal dimension of high temperature stability D=2.4535～2.5835, D _C ＝2.3988～2.6229, D _f ＝2.3127～2.5468;

The fractal dimension of low-temperature crack resistance D=2.3388～2.5835, D _C ＝2.3048～2.5171, D _f ＝2.3734～2.5870;

The fractal dimension of water stability D=2.4171～2.5993, D _C ＝2.4080～2.6102, D _f ＝2.3420～2.5669;

The fractal dimension of comprehensive performance D=2.4535～2.5835, D _C ＝2.4080～2.5171, D _f ＝2.3734～2.5468;

(2) Calculate the pass rate of mineral materials

Substituting the selected fractal dimension value into formula (1-1) and formula (1-2):

When r∈(PCS,NMPS),

When r ∈ (0.075, PCS),

In the formula, PCS is the boundary point size of coarse and fine aggregates, mm; NMPS is the nominal maximum particle size, mm; r is the particle size of the aggregate particle, expressed in sieve size, mm; r _min is the aggregate particle size Minimum particle size, mm; D is the fractal dimension of aggregate particle size distribution, that is, the aggregate gradation fractal dimension; Dc is the aggregate particle size gradation fractal dimension in the range of NMPS-PCS, that is is the fractal dimension of coarse aggregate; D _f is the fractal dimension of aggregate particle size distribution within the range of PCS ~ 0.075mm, that is, the fractal dimension of fine aggregate; P ₀ is the passing rate at the nominal maximum particle size NMPS ; P(PCS) is the size passing rate of the boundary point of coarse and fine aggregates; P(r) is the passing rate at the aggregate particle size r;

(3) Predict road performance

After scheme comparison and selection, the road performance prediction model of AC-20 modified asphalt mixture is as follows:

High temperature stability prediction model, DS=3206.5+16056.8D-2605.5D _c -14025.4D _f , regression coefficient 0.9370;

Prediction model of low temperature crack resistance, ε _B ＝-524.3-2779.6D+2999.9Dc+1210.9D _f , regression coefficient 0.9446;

Prediction model of water stability, DSR=-1.2919+0.3012D+0.3414D _c +0.2462D _f , regression coefficient 0.9417;

Among them, DS is the dynamic stability, ε _B is the failure strain, and DSR is the dynamic stability ratio;

According to the established road performance prediction model, the high temperature stability, low temperature crack resistance and water stability of AC-20 modified asphalt mixture are predicted; in the prediction model, the fractal dimensions D, D _c and D _f are used to calculate The predicted value of each index; if the road performance requirements are not met, reselect the fractal dimension within the recommended range until the predicted results meet the road performance requirements;

(4) Grading inspection

According to the correlation prediction model established between the fractal volume parameter and the fractal dimension, the gradation test is carried out. The prediction model is as follows:

Coarse aggregate fractal volume void ratio V _co =-1.5783-0.4599D _c +1.2698D _f , regression parameter R ² =0.9439;

Fractal volume of fine aggregate in coarse aggregate V _f =-1.0892+0.6795D _c -0.1456D _f , regression parameter R ² =0.9741;

V _co ≥ V _f , 1.1394D _c -1.4154D _f ≤ 0.4891;

The fractal dimensions of coarse and fine aggregates that meet the road performance requirements are substituted into the coarse aggregate fractal void ratio V _co and the fractal volume V _f of fine aggregate in the coarse aggregate prediction model for prediction and testing; when coarse When the fractal void ratio V _co of the aggregate is greater than the fractal volume V _f of the fine aggregate in the coarse aggregate, the coarse aggregate can form an effective skeleton; if no skeleton is formed, adjust the fractal dimension until a skeleton is formed;

(5) Test inspection

For the gradation that meets the above steps, the high temperature stability, low temperature performance and water stability road performance of the asphalt mixture are tested; if all meet the requirements, the designed gradation is qualified; if the requirements are not met, follow the above method steps Redesign the gradation until the requirements are met.

Advantage of the present invention and beneficial effect are as follows:

1. In view of the shortcomings of the current standard asphalt mixture design method in my country - Marshall design method, combined with the characteristics of climate, traffic and materials in Northeast China, on the basis of domestic and foreign research results and practical experience, the AC-20 modified asphalt mixture High, low temperature and water stability tests were carried out, the fractal structure model of asphalt mixture and its aggregate internal voids was established by using fractal theory, the parameters characterizing the fractal characteristics of the mixture and its aggregate voids were proposed, and the AC-20 modified asphalt was established. Mixture grading test predictive model.

2. The present invention establishes the relationship between AC-20 modified asphalt mixture and its aggregate void fractal characteristic parameters, aggregate gradation fractal dimension and volume index, high temperature stability, low temperature crack resistance, water stability and other evaluation indicators , A prediction model for road performance of AC-20 modified asphalt mixture suitable for Northeast China was established.

3. The present invention proposes an asphalt mixture design method based on pavement performance in Northeast China, which connects the design method of asphalt mixture with road performance, realizes optimization in the calculation process of asphalt mixture gradation design, and saves time and manpower , material and financial resources, has important research significance.

Detailed ways

The present invention will be described in detail below in conjunction with the examples.

Example 1

In this embodiment, the AC-20 modified asphalt mixture design method based on road performance specifically includes the following steps:

1. Select the fractal dimension

As shown in Table 1, the ranges of fractal dimensions D, D _C and D _f of the proposed AC-20 modified asphalt mixture gradation are comprehensive ranges derived on the premise of satisfying road performance. Takes a value within the range of dimensions.

Table 1 The fractal dimension range of AC-20 modified asphalt mixture meeting road performance requirements

skills requirement D. D_c D_f High temperature stability/60℃ 2.4535～2.5835 2.3988～2.6229 2.3127～2.5468 Low temperature crack resistance/-10℃ 2.3388～2.5835 2.3048～2.5171 2.3734～2.5870 water stability 2.4171～2.5993 2.4080～2.6102 2.3420～2.5669 Comprehensive performance 2.4535～2.5835 2.4080～2.5171 2.3734～2.5468

2. Calculate the pass rate of mineral materials

Substituting the selected fractal dimension value into formula (1-1) and formula (1-2)

When r∈(PCS,NMPS),

When r ∈ (0.075, PCS),

In the formula, PCS (primary control sieve between coarse and fine aggregate) is the boundary point size of coarse and fine aggregates, mm; NMPS (normal maximum particle sieve) is the nominal maximum particle size, mm; r is the aggregate particle size , expressed in sieve size, mm; r _min is the minimum particle size of aggregate particles, mm; D is the fractal dimension of aggregate particle size distribution, referred to as aggregate gradation fractal dimension; Dc is aggregate The fractal dimension of particle size distribution within the range of NMPS to PCS is the fractal dimension of coarse aggregate; _Df is the fractal dimension of aggregate particle size distribution within the range of PCS to 0.075mm, which is the fine aggregate Fractal dimension; P ₀ is the passing rate at the nominal maximum particle size NMPS; P(PCS) is the passing rate at the boundary point of coarse and fine aggregates; P(r) is the passing rate at the aggregate particle size r.

3. Predict road performance

After comparison and selection of multiple schemes, the road performance prediction model of AC-20 modified asphalt mixture is recommended, as shown in Table 2.

Table 2 Prediction model of AC-20 modified asphalt mixture road performance

Among them, DS is the dynamic stability, ε _B is the failure strain, and DSR is the dynamic stability ratio.

The high temperature, low temperature and water stability performance of AC-20 modified asphalt mixture are predicted by the pavement performance prediction model established in Table 2. In the prediction model, it is necessary to calculate the predicted value of each index through the fractal dimensions D, D _c , and D _f . If the road performance requirements are not met, reselect the fractal dimension within the recommended range until the predicted results meet the road performance requirements.

4. Grading test

According to the research results, the gradation test is carried out according to the established correlation model between the fractal volume parameters and the fractal dimension. The fractal dimensions of coarse and fine aggregates that meet road performance requirements are substituted into the coarse aggregate fractal void ratio V _co and the fractal volume V _f of fine aggregate in the coarse aggregate prediction model for prediction and testing. When the fractal porosity V _co of the coarse aggregate is greater than the fractal volume V _f of the fine aggregate in the coarse aggregate, the coarse aggregate can form an effective skeleton. If no skeleton is formed, adjust the fractal dimension until a skeleton is formed. The AC-20 modified asphalt mixture gradation test prediction model is shown in Table 3.

Table 3 AC-20 modified asphalt mixture gradation test prediction model

5. Test inspection

For the gradation that meets the above steps, the road performance tests such as high temperature stability, low temperature performance and water stability of the asphalt mixture are carried out. If all meet the requirements, the designed gradation is qualified. If the requirements are not met, find out the reason and make corrections in time, or redesign the gradation according to the above method steps until the requirements are met.

The results of the examples show that the present invention proposes the asphalt mixture aggregate gradation fractal dimension that is widely used in the asphalt pavement in the northeast region to meet the road performance requirements according to the characteristics of climate, traffic and materials in the northeast region and with reference to the requirements in the current norms and the range of fractal dimensions of coarse and fine aggregates; select the corresponding fractal dimension as the design parameter within the proposed range, deduce the passing rate of each sieve hole of the mineral material through the fractal dimension, and use the road performance prediction model established The pavement performance of asphalt mixture is predicted, and the gradation skeleton inspection is carried out using the gradation inspection prediction model. Finally, the asphalt mixture that meets the road performance requirements is tested and verified, and then a good gradation that meets the performance requirements is obtained. Thereby optimizing the design and reducing the unnecessary amount of experiments.

Claims (1)

1. a kind of AC-20 modified asphalt mixture design method based on pavement performance, which is characterized in that the mistake of the design method Journey is as follows:

(1) it is studied by carrying out high temperature, low temperature and water stability testing to AC-20 modified asphalt mixture, utilizes fractal theory The shape-division model of asphalt and its internal voids that gather materials is established, proposes that characterization mixture and its aggregate void divide shape special The parameter of sign establishes AC-20 modified asphalt mixture pavement performance prediction model and gradation verification prediction model；

(2) in bituminous mixture aggregate gradation fractal dimension and coarse aggregate, the fine aggregate fractal dimension for meeting pavement performance requirement In the range of, it selects corresponding fractal dimension as design parameter, the percent of pass of each sieve pore of mineral aggregate is derived by fractal dimension, lead to It crosses the pavement performance prediction model established and carries out Asphalt Mixture Performance inspection, carry out grade using gradation verification prediction model It is examined with skeleton, verification experimental verification finally is carried out to the asphalt for meeting estimated performance requirement, and then obtain meeting performance and want The good gradation asked；

The AC-20 modified asphalt mixture design method based on pavement performance, specifically comprises the following steps:

(1) fractal dimension is chosen

AC-20 modified asphalt mixture gradation meets the fractal dimension D of pavement performance requirement, D_CAnd D_fRange are as follows:

Fractal dimension D=2.4535~2.5835, D of high-temperature stability_C=2.3988~2.6229, D_f=2.3127~ 2.5468；

Fractal dimension D=2.3388~2.5835, D of low-temperature cracking-resistance_C=2.3048~2.5171, D_f=2.3734~ 2.5870；

Fractal dimension D=2.4171~2.5993, D of water stability_C=2.4080~2.6102, D_f=2.3420~2.5669；

Fractal dimension D=2.4535~2.5835, D of comprehensive performance_C=2.4080~2.5171, D_f=2.3734~2.5468；

(2) mineral aggregate percent of pass is calculated

By the values of fractal dimension chosen, formula (1-1) and formula (1-2) are substituted into:

As r ∈ (PCS, NMPS),

When r ∈ (0.075, PCS),

In formula, PCS is the boundary spot size that thickness is gathered materials, mm；NMPS is nominal maximum particle diameter size, mm；R is aggregate particle grain Diameter size is indicated, mm with screen size size；r_minFor aggregate particle minimum grain size size, mm；D is aggregate particle partial size The fractal dimension of distribution, as aggregate grading fractal dimension；Dc is aggregate particle partial size grade partition shape within the scope of NMPS~PCS Dimension, as coarse aggregate fractal dimension；D_fFor aggregate particle partial size within the scope of PCS~0.075mm gradation fractal dimension, as Fine aggregate fractal dimension；P₀For the percent of pass at nominal maximum particle diameter NMPS；P (PCS) is that cut-off point of the coarse and fine aggregate size passes through Rate；P (r) is the percent of pass at aggregate particle partial size r；

(3) pavement performance is predicted

By scheme comparison, the AC-20 modified asphalt mixture pavement performance prediction model of use is as follows:

The prediction model of high-temperature stability, DS=3206.5+16056.8D-2605.5D_c-14025.4D_f, regression coefficient 0.9370；

The prediction model of low-temperature cracking-resistance, ε_B=-524.3-2779.6D+2999.9Dc+1210.9D_f, regression coefficient 0.9446；

The prediction model of water stability, DSR=-1.2919+0.3012D+0.3414D_c+0.2462D_f, regression coefficient 0.9417；

Wherein, DS is dynamic stability, ε_BFor failure strain, DSR is dynamic stability ratio；

High-temperature stability, low-temperature cracking-resistance according to the pavement performance prediction model established to AC-20 modified asphalt mixture It can be carried out prediction with water stability；In prediction model, pass through fractal dimension D, D_c、D_fCalculate each index predicted value；If be unsatisfactory for Pavement performance requirement, chooses fractal dimension, until prediction result is all satisfied pavement performance requirement again in recommended range；

(4) gradation verification

Gradation verification is carried out by the related prediction model between the fractal product parameter established and fractal dimension, prediction model is such as Under:

Coarse aggregate fractal accumulates voidage V_co=-1.5783-0.4599D_c+1.2698D_f, regression parameter R²=0.9439；

Fractal product V of the fine aggregate in coarse aggregate_f=-1.0892+0.6795D_c-0.1456D_f, regression parameter R²=0.9741；

V_co≥V_f, 1.1394D_c-1.4154D_f≤0.4891；

The thick of the gradation of pavement performance requirement will be met, fine aggregate fractal dimension substitutes into coarse aggregate point shape voidage V_coAnd fine aggregate Fractal product V in coarse aggregate_fPrediction model is predicted and is examined；Divide shape voidage V when coarse aggregate_coGreater than fine aggregate Fractal product V in coarse aggregate_fWhen, coarse aggregate is capable of forming effective skeleton；Such as not formed skeleton, fractal dimension is adjusted, Until forming skeleton；

(5) experimental examination

To the gradation for meeting above-mentioned steps, the high-temperature stability, cryogenic property and water stability road property of asphalt are carried out It can examine；It is such as all satisfied requirement, then the gradation designed is qualification；It is such as unsatisfactory for requiring, redesigns grade by aforementioned method steps Match, until meeting the requirements.