CN108484071B - A kind of foamed asphalt in-situ cold recycling mixture and its grading method and application - Google Patents

Abstract

The invention provides a grading method of a foamed asphalt cold in-place recycling mixture, wherein the foamed asphalt cold in-place recycling mixture comprises foamed asphalt, old pavement milling material, aggregate, cement and water; the invention determines the new aggregate mixing amount according to the thickness of the cold-recycling structural layer and the milling thickness of the old pavement, and controls the grading of foamed asphalt, coarse aggregate, fine aggregate, cement and water in the new aggregate, so that the foamed asphalt in-place cold-recycling mixture provided by the invention has excellent pavement performance. Meanwhile, the invention also provides the foamed asphalt in-place cold recycling mixture obtained by the grading method and application of the foamed asphalt in-place cold recycling mixture in the old road maintenance and reconstruction.

Description

A kind of foamed asphalt in-situ cold recycling mixture and its grading method and application

technical field

The invention relates to the technical field of application of traffic civil engineering, in particular to a foamed asphalt in-situ cold recycling mixture and a grading method and application thereof.

Background technique

In-situ cold recycling refers to the use of asphalt recycling equipment to smash old asphalt pavement materials in situ, add new aggregates, mix and compact, and use old pavement materials as the main material for road construction technology. Cold-in-place recycled mixture refers to the mixture including old pavement milled material and new aggregate, and foamed asphalt cold-recycled-in-place mixture refers to the cold-in-place recycled mixture including foamed asphalt.

At present, the design method of in-situ cold recycled mixture in engineering practice is mainly: first determine the density of in-situ cold recycled mixture, and then determine the amount of new aggregate according to this density, and then according to the "Technical Specification for Recycling of Highway Asphalt Pavement" ( The gradation relationship between aggregates in JTGF41-2008) was determined to obtain in-situ cold recycled mixture.

However, the new aggregate content in the above method is determined by experience, which leads to the need to adjust the new aggregate content several times according to the milling thickness and actual compaction thickness of the road surface in the field test section in specific applications. The process is not only complicated, but also It also affects the progress of the project. In addition, the in-situ cold recycled mixture obtained by the above method has unreasonable gradation design between new aggregates, and the road performance of the obtained in-situ cold recycled mixture is uneven, and it is difficult to obtain an in-situ cold recycling mixture with excellent road performance. Cold recycled mix.

SUMMARY OF THE INVENTION

The invention provides a method for grading foamed asphalt in-situ cold-recycled mixture, without repeatedly adjusting the content of new aggregates, and the obtained foamed asphalt in-situ cold-recycled mixture has excellent road performance.

The invention provides a method for grading foamed asphalt cold-recycling-in-situ mixture. In parts by mass, the foamed asphalt is 2-4 parts; the total parts of the old pavement milling material and aggregate are 100 parts, the cement is 0.1-1.5 parts, and the water is 4.5-5.5 parts ;

The kind and consumption of described aggregate are determined according to the value of a in formula I:

a=(Y-1)/Y×100 Formula I;

When a≥35, the aggregate includes coarse aggregate and fine aggregate, the coarse aggregate is (a-20) parts, and the fine aggregate is 20 parts;

When 20<a<35, the aggregate includes coarse aggregate and fine aggregate, the coarse aggregate is 20 parts, and the fine aggregate is (a-20) parts;

When a≤20, the aggregate is coarse aggregate, and the coarse aggregate is a part;

In the formula I, a is the new aggregate content limit coefficient; in the formula I, Y is the new aggregate doping coefficient; the new aggregate doping coefficient is the thickness of the cold regeneration structure layer and the old pavement milling thickness. 0.875 times the ratio.

Preferably, the foamed asphalt in-situ cold recycling mixture further comprises 0.1-3 parts by mass of mineral powder.

Preferably, the mass percentage of powder with a particle size of less than 0.075 mm in the mineral powder is 75% to 100%.

Preferably, the particle size of the coarse aggregate is 15mm˜30mm.

Preferably, the particle size of the fine aggregate is less than 2.36 mm.

Preferably, the strength grade of the cement is 32.5 or 42.5.

Preferably, the cement is ordinary Portland cement, slag Portland cement or pozzolanic Portland cement.

The present invention provides the foamed asphalt in-situ cold recycled mixture obtained by the grading method described in the above technical solution, including foamed asphalt, old pavement milling material, aggregate, cement and water.

The present invention also provides the application of the foamed asphalt cold-recycled mixture obtained by the grading method described in the above technical scheme as a paving material in the maintenance and reconstruction of old roads.

The invention directly determines the doping amount of the new aggregate according to the thickness of the old pavement milling and the thickness of the cold regenerated structural layer, and avoids that when the new aggregate doping amount is determined empirically in the prior art, due to the milling thickness of the old pavement and the cold regenerated structural layer The thickness is different, so it is necessary to continuously adjust the amount of new aggregates. In addition, the present invention confirms the composition of the new aggregate according to the thickness of the old pavement milled and the thickness of the cold recycled structural layer, and strictly controls the consumption of the foamed asphalt, the old pavement milled material, aggregate, cement and water, which is conducive to making the foam The cold-in-situ recycled asphalt mixture forms a skeleton structure, and when the in-situ cold-recycled mixture includes fine aggregates, the fine aggregates are filled in the skeleton structure, so that the foamed asphalt in-situ cold-recycled mixture provided by the present invention has the following characteristics: Excellent road performance. As shown in the examples of this application, the foamed asphalt in-situ cold recycling mixture provided by the present invention has excellent road performance, and the foamed asphalt in-situ cold recycling mixture provided by the present invention has a Marshall stability of 14.79-16.72kN, The dry splitting strength at 15℃ is 0.68～0.78MPa, the residual stability is 84.2%～92.3%, the freeze-thaw splitting strength ratio is 72.3%～76.5%, and the dynamic stability is 3321.9～4423.2 times/mm.

Detailed ways

The present invention provides a method for grading foamed asphalt in-situ cold-recycled mixture, wherein the foamed asphalt in-situ cold-recycled mixture comprises foamed asphalt, old pavement milling material, aggregate, cement and water, in parts by mass , the foamed asphalt is 2-4 parts, the total parts of the old pavement milling material and aggregate is 100 parts, the cement is 1.5 parts, and the water is 4.5-5.5 parts;

The kind and consumption of described aggregate are determined according to the value of a in formula I:

a=(Y-1)/Y×100 Formula I;

When a≥35, the aggregate includes coarse aggregate and fine aggregate, the coarse aggregate is (a-20) parts, and the fine aggregate is 20 parts;

When 20<a<35, the aggregate includes coarse aggregate and fine aggregate, the coarse aggregate is 20 parts, and the fine aggregate is (a-20) parts;

When a≤20, the aggregate is coarse aggregate, and the coarse aggregate is a part;

In the formula I, a is the new aggregate content limit coefficient; in the formula I, Y is the new aggregate doping coefficient; the new aggregate doping coefficient is the thickness of the cold regeneration structure layer and the old pavement milling thickness. 0.875 times the ratio.

In the present invention, in parts by mass, the in-situ cold recycling foamed asphalt mixture comprises 2-4 parts of foamed asphalt, preferably 2.5-3.5 parts, more preferably 3.0 parts. In the present invention, the expansion ratio of the foamed asphalt is preferably ≥10%, more preferably ≥15%. In the present invention, the half-life of the foamed asphalt is preferably ≥8s, more preferably ≥10s. In the present invention, the foamed asphalt preferably meets the technical standards of "DB13/T 2513-2017 Technical Guidelines for Cold Recycling of Foamed Asphalt on Highway Asphalt Pavements".

In the present invention, the preparation method of the foamed asphalt is preferably obtained by foaming the base asphalt. In the present invention, the foaming method of the base asphalt preferably includes the following steps: mixing the base asphalt and water, and foaming under heating conditions. In the present invention, the heating temperature is preferably 140 to 160°C, more preferably 145 to 155°C, and more preferably 150 to 152°C. In the present invention, the mass ratio of the base asphalt and water is preferably 100:1.5-2.5, more preferably 100:2.8-2.3, more preferably 100:2-2.1. In the present invention, the base asphalt is preferably 70# base asphalt or 90# base asphalt. In the present invention, the foamed asphalt having the expansion ratio and half-life meeting the above-mentioned requirements is preferably prepared by the above-mentioned foaming.

In the present invention, the foamed asphalt serves to bond each component raw material into a whole, to increase the strength and enhance the ability of the pavement to resist traffic damage, and to make the pavement stable.

In the present invention, based on the mass parts of the foamed asphalt, the total parts of the old road milling material and aggregate are 100 parts, and the mass parts of the aggregate are determined according to the value of a in formula I:

a=(Y-1)/Y×100 Formula I;

When a≥35, the aggregate includes coarse aggregate and fine aggregate, the coarse aggregate is (a-20) parts, and the fine aggregate is 20 parts;

When 20<a<35, the aggregate includes coarse aggregate and fine aggregate, the coarse aggregate is 20 parts, and the fine aggregate is (a-20) parts;

When a≤20, the aggregate is coarse aggregate, and the coarse aggregate is a part;

In the formula I, a is the new aggregate content limit coefficient; in the formula I, Y is the new aggregate doping coefficient; the new aggregate doping coefficient is the thickness of the cold regeneration structure layer and the old pavement milling thickness. 0.875 times the ratio.

In the present invention, the milled thickness of the old pavement is preferably 10-15 cm; the thickness of the cold recycled structural layer is preferably 15-20 cm.

In the present invention, the thickness of the cold regeneration structure layer is the thickness of the target pavement.

In the present invention, the in-situ cold recycled foamed asphalt mixture includes used pavement milled material. In the present invention, the old pavement milling material is the waste material obtained after the pavement to be repaired is milled. The present invention has no special requirements on the milling method of the road surface to be repaired, and it is sufficient to adopt what is known to those skilled in the art.

In the present invention, the cold-in-place regeneration mix includes coarse aggregate. In the present invention, the particle size of the coarse aggregate is preferably 15 mm to 30 mm, more preferably 18 to 28 mm, and more preferably 20 to 25 mm; the apparent relative density of the coarse aggregate is preferably ≥ 2.6, more preferably ≥ 3.0. In the present invention, the content of needle-shaped coarse aggregate in the coarse aggregate is preferably ≤ 20%, more preferably ≤ 15%; the crush value of the coarse aggregate is preferably ≤ 26%, more preferably ≤ 25%. In the present invention, the coarse aggregate preferably meets the technical requirements for coarse aggregate in "Technical Specification for Recycling of Highway Asphalt Pavement" (JTG F40-2004). In the present invention, the coarse aggregates mainly play the role of skeleton in the in-situ cold regeneration mixture.

In the present invention, when the in-situ cold regeneration mixture includes fine aggregates, the particle size of the fine aggregates is preferably <2.36 mm; the apparent relative density of the fine aggregates is preferably ≥ 2.5, more preferably ≥ 3.0; the sand equivalent of the fine aggregate is preferably ≥ 60%, more preferably ≥ 65%; the firmness of the fine aggregate > 0.3mm aggregate is ≥ 12%, more preferably ≥ 15%; the firmness The optimal performance refers to the performance of the sand sample being soaked and dried in saturated sodium sulfate solution for many times and subjected to the crystallization pressure of sodium sulfate without significant damage or strength reduction. In the present invention, "the firmness of the fine aggregate > 0.3 mm in aggregate size > 12%" means that the portion of the fine aggregate with particle size > 0.3 mm meets the firmness test in the firmness test The required mass percentage is ≥12%; the angularity of the fine aggregate is ≥30s, more preferably ≥35s; the angularity of the fine aggregate preferably refers to: measuring a certain volume of the fine aggregate all pass the standard funnel required The flow time of , is called the angularity of fine aggregate, and is represented by s. In the present invention, the "angularity of the fine aggregate ≥ 30s" means that the flow time required for all the fine aggregate to pass through the standard funnel is ≥ 30s. In the present invention, the fine aggregate preferably meets the technical requirements for fine aggregate in "Technical Specification for Recycling of Highway Asphalt Pavement" (JTG F40-2004). In the present invention, the fine aggregates mainly play a filling role in the cold-in-place recycled mixture.

In the present invention, based on the mass parts of the foamed asphalt, the foamed asphalt cold-in-situ recycling mixture includes 0.1-1.5 parts of cement, preferably 0.5-1.5 parts, more preferably 1.0-1.3 parts. In the present invention, the strength grade of the cement is preferably 32.5 or 42.5; the cement is preferably ordinary Portland cement, slag Portland cement or pozzolanic Portland cement; the initial setting time of the cement is preferably ≥3h , more preferably ≥3.5h; the final setting time of the cement is preferably ≥6h, further preferably ≥6.5h. In the present invention, the appearance of the cement is free of agglomerates. In the present invention, the cement preferably meets the technical requirements for cement in "Technical Specification for Recycling of Highway Asphalt Pavement" (JTG F40-2004). In the present invention, part of the cement will absorb water and undergo a hydration reaction, and the hydration product fills the tiny pores between the foamed asphalt cold recycled mixture to promote the foamed asphalt cold recycled mixture to form a uniform, pore-closed compact whole , which improves the road performance of the foamed asphalt cold recycled mixture; the other part of the cement plays the role of active mineral powder and chemically adsorbs with the asphalt to form a mechanical structural film, which greatly improves the adhesion between the cement and the asphalt.

In the present invention, based on the mass parts of the foamed asphalt, the foamed asphalt cold-in-situ recycling mixture includes 4.5-5.5 parts of water, preferably 4.6-5.4 parts, more preferably 4.8-5.1 parts, more preferably 5.0 servings.

By controlling the foamed asphalt, old pavement milling material, coarse aggregate, fine aggregate, cement and water within the above ranges, the present invention facilitates the formation of a skeleton structure for the in-situ cold recycled mixture, and the fine aggregate is filled in the In the skeleton structure, the in-situ cold regeneration mixture provided by the present invention has excellent road performance. Moreover, the present invention establishes the relationship between the new aggregate content and the thickness of the old pavement milled and the thickness of the cold recycled structural layer, so that when the new aggregate content is determined empirically in the prior art, due to the milled thickness of the old pavement and the thickness of the cold recycled structure, the The thickness of the structural layer is different, so it is necessary to continuously adjust the amount of new aggregates.

In the present invention, based on the mass parts of the foamed asphalt, the foamed asphalt cold-in-situ recycling mixture preferably further comprises 0.1-3 parts of mineral powder, more preferably 0.5-3 parts, more preferably 1.0-2.5 parts parts, more preferably 1.5 to 2.0 parts.

In the present invention, the mass percentage content of the powder with a particle size of less than 0.075mm in the mineral powder is preferably 75%-100%, more preferably 80%-95%, more preferably 85-90%; the The apparent density of the mineral powder is preferably ≥2.5t/m ³ , more preferably ≥3.0t/m ³ ; the hydrophilic coefficient of the mineral powder is preferably <1.0, more preferably <0.8; the moisture content of the mineral powder is preferably less than or equal to 1.0 %, more preferably ≤ 0.8%. In the present invention, the mineral powder preferably meets the technical requirements of "JTG F40-2004" for mineral powder. In the present invention, the mineral powder preferably includes limestone or magmatic rock. In the present invention, the mineral powder is beneficial to further improve the road performance of the in-situ cold recycled mixture.

The present invention provides the foamed asphalt in-situ cold recycled mixture obtained by the grading method described in the above technical solution, including foamed asphalt, old pavement milling material, aggregate, cement and water; preferably, it also includes mineral powder.

In the present invention, the foamed asphalt, the old road milling material, aggregate, cement and cement are preferably mixed according to the mass fractions of the foamed asphalt, the old pavement milling material, aggregate, cement and water according to the above technical solution, and the foamed asphalt is obtained. Ground-cooled recycled mix. The present invention does not have any special requirements on the mixing mode, and it is sufficient to use those well-known to those skilled in the art.

The present invention also provides the application of the foamed asphalt cold-recycled mixture obtained by the grading method described in the above technical scheme as a paving material in the maintenance and reconstruction of old roads.

In the present invention, the pavement to be repaired and reconstructed is preferably milled, and the obtained waste material is used as the old pavement milling material in the in-situ cold recycling mixture; the foamed asphalt in-situ cold recycling mixture is laid after milling Or on unmilled subgrades. The present invention has no special requirements on the laying method, and a laying method well known to those skilled in the art can be adopted. The invention uses the milling material of the road surface to be repaired and reconstructed as the raw material of the foamed asphalt in-situ cold recycling mixture, and directly determines the doping amount of different types of new aggregates according to the milling thickness of the old road surface and the thickness of the cold recycling structure layer, so as to avoid the current situation. In the prior art, when the content of new aggregates is determined through experience, due to the difference in the thickness of the old pavement milling and the thickness of the cold recycled structural layer, it is necessary to continuously adjust the content of new aggregates and simplify the way of pavement reconstruction.

The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention.

Example 1

Taking the milling thickness of the old pavement as 10cm and the design thickness of the cold recycled structural layer as 18cm as an example, the new aggregate content coefficient Y is obtained by calculation, and the new aggregate content coefficient is 1.575. Then determine the mass fraction of coarse aggregate and fine aggregate by formula (Y-1)/Y×100. It can be seen from the calculation that (Y-1)/Y×100=36.5>35, and then it can be obtained that the mass fraction of fine aggregate is 20 parts, the mass fraction of coarse aggregate is 16.5 parts, and the old road milling material is 63.5 parts. 1.5 parts by mass of cement, 2.5 parts by mass of foamed asphalt, and 5.1 parts by mass of water. The particle size of the coarse aggregate is 15-30 mm, the apparent relative density of the coarse aggregate is 2.6, the needle flake content of the coarse aggregate is 20%, and the crushing value of the coarse aggregate is 26%; The apparent relative density is 2.5, the sand equivalent of the fine aggregate is 60%, the firmness of the fine aggregate > 0.3mm is 12%, the angularity of the fine aggregate is 30s; the strength grade of the cement is 32.5 , the initial setting time of cement is 3h, the final setting time is 6h, and the appearance of cement has no agglomeration.

Example 2

Taking the milling thickness of the old pavement as 12cm and the design thickness of the cold recycled structural layer as 18cm as an example, the new aggregate content coefficient Y is obtained by calculation, and the new aggregate content coefficient is 1.3125. Then determine the mass fraction of coarse aggregate and fine aggregate by formula (Y-1)/Y×100. By calculation, it can be seen that (Y-1)/Y×100=24<35, and then it can be obtained that the mass fraction of coarse aggregate is 20, the mass fraction of fine aggregate is 4, and the old road milling material is 76. In addition, adding 1.5 parts by mass of cement, 2.0 parts by mass of foamed asphalt, and 4.5 parts by mass of water. The particle size of the coarse aggregate is 15-30 mm, the apparent relative density of the coarse aggregate is 2.7, the needle-like content of the coarse aggregate is 18%, and the crushing value of the coarse aggregate is 25%; The apparent relative density is 2.6, the sand equivalent of the fine aggregate is 62%, the firmness of the fine aggregate > 0.3mm is 15%, the angularity of the fine aggregate is 32s; the strength grade of the cement is 42.5 , the initial setting time of cement is 4h, the final setting time is 7h, and the appearance of cement has no agglomeration.

Example 3

Taking the milling thickness of the old pavement as 13cm and the design thickness of the cold recycled structural layer as 18cm as an example, the new aggregate content coefficient Y is obtained by calculation, and the new aggregate content coefficient is 1.21. Then determine the mass fraction of coarse aggregate and fine aggregate by formula (Y-1)/Y×100. It can be seen from the calculation that (Y-1)/Y×100=17<20, and then it can be obtained that the mass fraction of fine aggregate is 0, the mass fraction of coarse aggregate is 17, and the old road milling material is 83. 1.5 parts by mass of cement, 3 parts by mass of mineral powder, 3.0 parts by mass of foamed asphalt, and 5.5 parts by mass of water. The particle size of the coarse aggregate is 15-30 mm, the apparent relative density of the coarse aggregate is 2.8, the needle-like content of the coarse aggregate is 15%, and the crushing value of the coarse aggregate is 23%; The apparent relative density is 2.8, the sand equivalent of the fine aggregate is 65%, the firmness of the fine aggregate > 0.3mm is 18%, the angularity of the fine aggregate is 35s; the strength grade of the cement is 42.5 , the initial setting time of the cement is 5h, the final setting time is 8h, and the appearance of the cement has no aggregate agglomeration.

Example 4

The experiment was carried out according to the method of Example 1, except that the amount of foamed asphalt was 3.5 parts by mass.

Example 5

The experiment was carried out according to the method of Example 1, except that the amount of foamed asphalt was 4.0 parts by mass.

Comparative Example 1

The experiment was carried out according to the method of Example 1, except that the amount of water used was 4.0 parts by mass.

Comparative Example 2

The experiment was carried out according to the method of Example 1, except that the amount of water used was 6.0 parts by mass.

The road performance of the foamed asphalt in-situ cold recycled mixture obtained in Example 1 was tested, and the test results were shown in Table 1:

Table 1 Road performance of the foamed asphalt in-situ cold recycled mixture obtained in Example 1

Measured project 40℃MS(kN) 15℃R_T(MPa) MS₀(%) TSR(%) DS(times/mm) Measured value 16.72 0.78 92.3 76.5 4423.2 skills requirement ≥14 ≥0.65 ≥85 ≥70 ≥3000

The road performance of the foamed bitumen obtained in Example 2 is tested in situ cold recycling mixture, and the test results are as shown in Table 2:

Table 2 Road performance of the foamed asphalt in-situ cold recycled mixture obtained in Example 2

The road performance of the foamed bitumen obtained in Example 3 is tested in situ cold recycling mixture, and the test results are as shown in Table 3:

Table 3 Road performance of the foamed asphalt in-situ cold recycled mixture obtained in Example 3

Measured project 40℃MS(kN) 15℃R_T(MPa) MS₀(%) TSR(%) DS(times/mm) Measured value 14.79 0.68 84.2 72.3 3321.9 skills requirement ≥14 ≥0.65 ≥75 ≥70 ≥3000

In Tables 1 to 3, 40°C MS refers to: Marshall stability at 40°C; 15°C _RT refers to: dry splitting strength at 15°C; MS ₀ refers to: residual stability; TSR refers to Yes: freeze-thaw splitting strength ratio; DS refers to: dynamic stability.

In the present invention, all indicators of the 40°C MS, 15°C RT , MS ₀ , TSR and DS are tested according to "Asphalt and Asphalt Mixture Test Regulations" (JTG E- _20-2011 ).

Dry and wet splitting strength tests were performed on the foamed asphalt mixtures prepared in Example 1, Example 4 and Example 5. The test results are shown in Table 4.

Table 4 Dry and wet splitting strength of Example 1, Example 4 and Example 5

Mechanical index Example 1 Example 4 Example 5 15℃R_T(MPa) 0.78 0.72 0.68 R_Tw(MPa) 0.71 0.68 0.65

In Table 4, 15°C RT _. refers to dry splitting strength; _RTW refers to: wet splitting strength at 25°C. It can be seen from Table 4 that the in-situ cold recycled foamed asphalt mixture provided by the present invention has higher dry splitting strength and wet splitting strength, and has better mechanical properties.

The dry density test was carried out on the foamed bitumen in-situ cold recycled mixture prepared in Example 1, Comparative Example 1 and Comparative Example 2. The test results are shown in Table 5.

Table 5 Dry density of Example 1, Comparative Example 1 and Comparative Example 2

Example 1 Comparative Example 3 Comparative Example 4 Dry density ρ_max(g/cm³) 2.151 2.133 2.100

It can be seen from Table 5 that the foamed asphalt cold-recycled-in-situ mixture provided by the present invention has a larger dry density, which can reach 2.151 g/cm ³ .

It can be seen from the above test results that the foamed asphalt in-situ cold recycling mixture provided by the present invention has excellent road performance, and the foamed asphalt in-situ cold recycling mixture provided by the present invention has a Marshall stability of 14.79 ~ 16.72kN, 15 ℃ The dry splitting strength is 0.68-0.78MPa, the residual stability is 84.2%-92.3%, the freeze-thaw splitting strength ratio is 72.3%-76.5%, and the dynamic stability is 3321.9-4423.2 times/mm. In addition, the present invention effectively improves the dry and wet splitting strength of the prepared foamed asphalt in-situ cold recycling mixture by controlling the amount of foamed asphalt to be 2-4 parts; the present invention controls the amount of water to be 4.5-5.5 The dry density of the prepared foamed asphalt cold-in-situ recycling mixture is effectively improved. Road performance of foamed asphalt cold-in-place recycled mixtures.

The above are only the preferred embodiments of the present invention. It should be pointed out that for those skilled in the art, without departing from the principles of the present invention, several improvements and modifications can be made. It should be regarded as the protection scope of the present invention.

Claims (9)

1. A grading method of a foamed asphalt cold-in-place recycling mixture comprises the following steps of (by mass), 2-4 parts of foamed asphalt, an old pavement milling material, aggregate, cement and water; the total parts of the used road milling material and the aggregate are 100 parts, the cement is 0.1-1.5 parts, and the water is 4.5-5.5 parts;

the category and the dosage of the aggregate are determined according to the value of a in the formula I:

a ═ Y-1)/yx 100 formula I;

when a is more than or equal to 35, the aggregate comprises coarse aggregate and fine aggregate, wherein the coarse aggregate accounts for (a-20) parts, and the fine aggregate accounts for 20 parts;

when 20 < a <35, the aggregates include coarse aggregates and fine aggregates, the coarse aggregates are 20 parts, the fine aggregates are (a-20) parts;

when a is less than or equal to 20, the aggregate is coarse aggregate, and the coarse aggregate is a parts;

a in the formula I is a new aggregate mixing amount limit coefficient; y in the formula I is a new aggregate doping coefficient; the doping coefficient of the new aggregate is 0.875 time of the ratio of the thickness of the cold recycling structure layer to the milling thickness of the old pavement.

2. The grading method according to claim 1, wherein the foamed asphalt in-place cold recycling mixture further comprises 0.1-3 parts by mass of mineral powder.

3. The grading method according to claim 2, wherein the mass percentage of the powder with the particle size of less than 0.075mm in the ore powder is 75-100%.

4. A grading process according to claim 1, characterized in that the coarse aggregate has a particle size of 15-30 mm.

5. A grading process according to claim 1, characterized in that the fine aggregate has a particle size < 2.36 mm.

6. A grading process according to claim 1, characterized in that the cement has a strength grade of 32.5 or 42.5.

7. A grading process according to claim 1 or 6, wherein the cement is Portland portland cement, slag portland cement or pozzolanic portland cement.

8. The foamed asphalt cold in place recycling mixture obtained by the grading method of any one of claims 1 to 7, comprising foamed asphalt, old road milling material, aggregate, cement and water.

9. Use of the foamed asphalt cold in place recycling mix according to claim 8 as a paving material in old road repair and reconstruction.