CN111153632A

CN111153632A - Fine-grain type semi-open graded asphalt mixture and mix proportion design method thereof

Info

Publication number: CN111153632A
Application number: CN202010008337.2A
Authority: CN
Inventors: 侯睿; 陶卓辉
Original assignee: Shanghai Daochun Transportation Technology Co ltd
Current assignee: Shanghai Daochun Transportation Technology Co ltd
Priority date: 2020-01-06
Filing date: 2020-01-06
Publication date: 2020-05-15

Abstract

The invention discloses a fine particle type half-open graded asphalt mixture, which has a design porosity of 10-15% and a paving thickness of only 2.0cm, is particularly suitable for maintenance construction of asphalt pavements, and has the following performance advantages in maintenance construction compared with the existing materials: 1) the anti-skid performance of the plateau pavement is improved, the large gap drainage effect is good, the water mist of the vehicle running in rainy days can be greatly reduced, and the safety of the vehicle running in rainy days is improved; 2) and (3) reducing the noise of the road surface: the mixture is of a large-gap structure, and can partially absorb noise generated by friction between a rolling tire and an asphalt pavement; 3) the paving thickness is 2cm, the influence on the elevation of the original pavement is small, and the curb or the guardrail of the original pavement is not influenced; 4) the porosity is 10-15%, and is relatively smaller than the porosity of 18-22% which is usually designed for drainage pavement, so that the index requirements on stone and modified asphalt in raw materials are correspondingly reduced, and the method is easier to realize in maintenance engineering. The invention also discloses a design method of the mixing proportion of the mixture.

Description

Fine-grain type semi-open graded asphalt mixture and mix proportion design method thereof

Technical Field

The invention relates to a fine-grain type semi-open graded asphalt mixture, belonging to the technical field of asphalt pavement maintenance engineering.

Background

At present, various thin layer overlay technologies are frequently adopted in asphalt pavement maintenance engineering, such as SMA-10 and EAC-10 with a dense grading structure, OGFC-10 and PAC-10 with an open grading structure and the like. The traditional close-graded mixture (such as AC and SMA grades) mostly has a design void ratio of 3-6%, the open-graded mixture (such as OGFC and PAC grades) needs a design void ratio of more than 18%, and the semi-open-graded asphalt macadam mixture AM-10 has a design void ratio of 6-12%, the existing asphalt mixtures have the characteristics that the close-graded (AC and SMA grades) mixture is most easily realized in engineering and has relatively low cost, but the close-graded (AC and SMA grades) mixture is difficult to provide additional road surface functions of skid resistance, drainage and noise reduction for the surface functional layer, the open-graded (OGFC and PAC grades) mixture can provide additional road surface functions of skid resistance, drainage and noise reduction for the surface functional layer, but the requirements on technical indexes of raw materials (stone and asphalt) are very high, the design process of the mixing ratio is complex, and the factors of high cost hinder the large-area popularization and application of the open-graded (OGFC and, the 6-12% of the design porosity of the semi-open-graded (AM-graded) asphalt-macadam mixture is easy to store water in a pavement structure and is difficult to drain, and the pavement has insufficient water damage resistance, so that the asphalt-macadam mixture is rarely applied to engineering.

In summary, it is necessary to develop an asphalt mixture between a dense-graded mixture and an open-graded mixture, which has a lower cost increase than the dense-graded mixture, but can obtain a pavement function similar to the open-graded mixture, and is particularly suitable for application in urban highways, expressways and tunnels, not only can greatly improve the pavement use function, but also has easily available raw materials, reasonable cost and easy large-scale popularization.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a fine-grain type semi-open graded asphalt mixture which has better anti-sliding, drainage and noise reduction performances, smaller paving thickness and lower construction cost.

The invention specifically adopts the following technical scheme to solve the technical problems:

a fine-grained, semi-open-graded asphalt mix whose bulk properties and properties meet the requirements set forth in tables 1 and 2 below, respectively:

TABLE 1 batch volume property requirements

TABLE 2 blend Performance requirements

Performance index	Unit of	Technical requirements	Test method
				Leakage loss of asphalt	％	≤0.1	T0732
Kent castle scatter loss	％	≤12	T0733
				Freeze-thaw split strength ratio	％	≥80	T0729
Degree of dynamic stability	Sub/mm	≥3000	T 0719

Wherein, the bulk density of the test piece is calculated by a volume method.

Preferably, the asphalt used in the fine-grain semi-open-graded asphalt mixture is high-performance modified asphalt meeting the technical indexes listed in the following table 3:

TABLE 3 technical index requirements for high-Performance modified asphalts

Preferably, the coarse aggregate used by the fine-grain type semi-open graded asphalt mixture is basalt or diabase macadam with the specification range of 5-10mm, and meets the quality technical requirements listed in the following table 4:

TABLE 4 technical requirements for the quality of coarse aggregates for bituminous mixtures

Detecting items	Technical standard	Detection method
			Stone crush value (%)	≤20	T 0316
Los Angeles abrasion loss (%)	≤28	T 0317
			Apparent density (t/m)³)	≥2.70	T 0304
Water absorption (%)	≤2.0	T 0304
			Adhesion to asphalt	Grade 5	T 0616
Firmness (%)	≤12	T 0314
			Content of needle-like pellets (blend (%)	≤10	T 0312
Washing method<0.075mm particle content (%)	≤1	T 0310

。

Preferably, the fine aggregate used in the fine-grained semi-open-graded asphalt mixture is limestone machine-made sand which meets the requirements listed in the following tables 5 and 6 in specification and quality respectively:

TABLE 5 Fine aggregate Specification

TABLE 6 Fine aggregate quality specifications

Quality standard	Technical requirements	Detection method
			Apparent relative density	≥2.60	T 0328
Firmness (> 0.3mm fraction) (%)	≤12	T 0340
			Sand equivalent (%)	≥60	T 0334
Angular (flow time)(s)	≥30	T 0345

。

Preferably, the porosity of the fine-grain type semi-open-graded asphalt mixture is 10% -15%, and the paving thickness is 2.0 cm.

The mix proportion design method of the fine-grain semi-open-graded asphalt mixture in any technical scheme comprises the following steps:

step 1, selecting 0-3mm fine aggregate, 5-10mm coarse aggregate and qualified mineral powder, and determining the optimal gradation;

step 2, calculating the initial asphalt dosage P corresponding to the optimal gradation according to the expected minimum thickness DA of the asphalt oil film being 9.0 mu m_a；

Step 3, according to the initial asphalt dosage P_aAnd is greater than P_aThe at least two asphalt dosages are molded into a plurality of corresponding groups of test pieces by rotary compaction, and each group comprises at least two test pieces with the same formula;

step 4, measuring volume property parameters of each group of test pieces according to the requirements of table 1, and taking the average value of the asphalt dosage closest to the target void ratio of 12.5% and the minimum asphalt dosage meeting all volume property requirements as the optimal asphalt dosage;

and 5, preparing the fine-grain type semi-open graded asphalt mixture according to the determined optimal grading and optimal asphalt using amount, verifying whether the fine-grain type semi-open graded asphalt mixture meets the performance requirements of the table 2, if so, determining the current optimal grading and optimal asphalt using amount to be the final mixing ratio, and if not, finely adjusting the current optimal grading and/or optimal asphalt using amount until the performance requirements of the table 2 are completely met.

Preferably, the diameter of the molded test piece formed by rotary compaction is 100mm, the unit pressure of rotary compaction is 600Kpa, and the number of times of rotary compaction is 100.

Preferably, said greater than P_aAt least two asphalts including P_a+0.2 and P_a+0.4 of the two bitumens.

Preferably, the optimal gradation is determined within the gradation range shown in table 7 below:

TABLE 7 mixture gradation design Range

Size of square hole sieve	Percent by weight of key sieve pores
		13.2mm	100
9.5mm	80-100
		4.75mm	20-30
2.36mm	18-28
		1.18mm	10-22
0.6mm	6-16
		0.3mm	5-12
0.15mm	5-10
		0.075mm	4-6

。

Compared with the prior art, the technical scheme of the invention has the following beneficial effects:

the fine grain type semi-open graded asphalt mixture (called SOGFC-10 herein) provided by the invention has the design void ratio of 10-15%, and the paving thickness is only 2.0cm, so that the fine grain type semi-open graded asphalt mixture is particularly suitable for being used in maintenance construction of asphalt pavements, can endow the original asphalt pavements with more use functions while maintaining construction, and has the following performance advantages in maintenance construction compared with the existing materials:

1) the anti-skid performance of the plateau pavement is improved, the large gap drainage effect is good, the water mist of the vehicle running in rainy days can be greatly reduced, and the safety of the vehicle running in rainy days is improved;

2) and (3) reducing the noise of the road surface: the mixture is of a large-gap structure, and can partially absorb noise generated by friction between a rolling tire and an asphalt pavement;

3) the paving thickness is 2cm, the influence on the elevation of the original pavement is small, and the curb or the guardrail of the original pavement is not influenced;

4) the porosity is 10-15%, and is relatively smaller than the porosity of 18-22% which is usually designed for drainage pavement, so that the index requirements on stone and modified asphalt in raw materials are correspondingly reduced, and the method is easier to realize in maintenance engineering.

Detailed Description

Aiming at the defects of the existing material in the maintenance construction of the asphalt pavement, the invention provides a fine grain type semi-open graded asphalt mixture SOGFC-10, which has the design porosity of 10-15% and the paving thickness of only 2.0cm, is particularly suitable for the maintenance construction of the asphalt pavement, and can endow the original asphalt pavement with more use functions while maintaining construction.

For the public to understand, the following is a detailed description of the technical solution of the present invention:

(1) SOGFC-10 mixture performance index

The volume property requirements of the compacted test piece of the SOGFC-10 mixture are shown in Table 1, and the pavement performance requirements of the SOGFC-10 mixture are shown in Table 2.

For the asphalt mixture with large porosity, the durability of the mixture can be ensured only by enough oil film thickness, so that the minimum thickness of the asphalt oil film of the SOGFC-10 mixture is 9.0 mu m.

TABLE 1 volume property requirements for SOGFC-10 blends

Note that: the bulk density of the test piece is calculated by a volume method

TABLE 2 SOGFC-10 blend Performance requirements

(2) Technical requirements of raw materials

1) High-performance modified asphalt

The SOGFC-10 asphalt concrete adopts high-performance modified asphalt suitable for traffic and climate characteristics, and the preferred technical indexes of the high-performance asphalt are shown in the following table 3.

TABLE 3 technical index requirements for high-Performance modified asphalts

2) Coarse aggregate

Hard, clean and non-weathered particles and near-cubic particle basalt or diabase macadam made of stone are adopted, and the specification range of the coarse aggregate is preferably 5-10 mm. The crushed stones rolled by the impact crusher are strictly controlled in the content of elongated flat particles to ensure the quality of the coarse aggregate. The coarse aggregate technical requirements are shown in table 4.

TABLE 4 technical requirements for the quality of coarse aggregates for SOGFC-10 asphalt mixtures

2) Fine aggregate

The fine aggregate of the SOGFC-10 asphalt mixture is preferably limestone machine-made sand, the fine aggregate is required to be hard, clean, dry, weatherproof, free of impurities and provided with proper gradation, the machine-made sand is manufactured by a special sand making machine, and the gradation meets the requirement of S16. The preferred specifications and quality requirements are shown in tables 5 and 6, respectively.

TABLE 5 Fine aggregate (machine-made Sand) Specification

TABLE 6 Fine aggregate quality specifications

Quality standard	Technical requirements	Detection method
			Apparent relative densityDegree of rotation	≥2.60	T 0328
Firmness (> 0.3mm fraction) (%)	≤12	T 0340
			Sand equivalent (%)	≥60	T 0334
Angular (flow time)(s)	≥30	T 0345

(3) Range of grading design

To facilitate the actual construction operation, the inventors have determined the range of the design gradation of the SOGFC-10 asphalt mixture through a number of experiments, as shown in Table 7.

TABLE 7 SOGFC-10 mixture gradation design Range

(4) Mix proportion design method

In order to accurately and efficiently complete the mix proportion design of the semi-open graded SOGFC-10 asphalt mixture and achieve the expected volume property and mixture performance, the design method can refer to the following mix proportion design flow and method:

the SOGFC-10 test piece is molded by rotary compaction, the diameter of the molded test piece is 100mm, the unit pressure of a rotary compactor is 600Kpa, the number of rotary compaction times is set to be 100,

1) selecting two grades of aggregates meeting the specification requirements, namely 0-3mm fine aggregates, 5-10mm coarse aggregates and qualified mineral powder, adjusting the mixing amount of the aggregates and the mineral powder according to the SOGFC-10 grading range in the table 7, and directly determining the optimal grading composition;

2) initial asphalt dosage P_aThe calculation is carried out according to the expected minimum thickness DA of the asphalt oil film being 9.0 μm: the specific surface area coefficient in the technical Specification for constructing asphalt road surfaces for roads (JTG F40-2004) is adopted for calculationThe formula 1 and the formula 2 for calculating the effective thickness of the asphalt film can reversely calculate the initial asphalt dosage P corresponding to the optimal gradation_a(％)；

SA＝Σ(P_i×FA_I) (formula 1)

In the formula: SA-specific surface area of aggregate, m²/kg

P_i-percent passage of various particle sizes%

FA_iSurface area factor for aggregates of various particle sizes, as listed in Table 8

DA-effective thickness of asphalt film, μm

P_be-effective bitumen content%

γ_b-relative density of bitumen (25 ℃/25 ℃), dimensionless

Note: the surface area coefficient FA of aggregates with the size larger than 4.75mm in various mixed materials with the nominal maximum particle size is 0.0041, and is calculated once, and the part of FA below 4.75mm_iAs exemplified in table 8.

TABLE 8 surface area coefficient of aggregate

Mesh size(mm)	19	16	13.2	9.5	4.75	2.36	1.18	0.6	0.3	0.15	0.075
												Surface area coefficient FA_i	0.0041	－	－	－	0.0041	0.0082	0.0164	0.0287	0.0614	0.1229	0.3277

3) The optimal asphalt dosage is not less than the asphalt dosage P corresponding to the minimum oil film thickness_aSo 3 groups of predicted asphalt dosages (P) are selected_a，P_a+0.2，P_a+0.4), forming test pieces by adopting a rotary compaction instrument, forming 3 groups of test pieces under the designed compaction times, and forming 2 test pieces with the same formula by using the asphalt in each group;

4) the method comprises the steps of measuring the void ratio of a test piece by a volume method in technical Specification for Highway asphalt pavement construction (JTG F40-2004), synthesizing the requirements of volume properties (void ratio VV, asphalt saturation VFA and mineral aggregate clearance ratio VMA) and the requirement of oil film thickness (shown in Table 1) of 3 groups of test pieces by a calculation method for maximum theoretical density, setting the asphalt dosage closest to the target void ratio of 12.5% as OAC1, setting the minimum asphalt dosage meeting the requirements of all volume properties as OAC2, and determining the optimum asphalt dosage OAC as (OAC1+ OAC 2)/2;

5) forming the SOGFC-10 mixture by adopting the optimal gradation and the optimal asphalt dosage and carrying out pavement performance verification: the asphalt leakage test is used for testing whether the asphalt dosage meets the requirement of the maximum asphalt dosage, the freeze-thaw splitting test and the Kentberg flooding flying test are used for testing the water damage resistance of the asphalt mixture, and the rutting test is used for testing the high-temperature deformation resistance of the mixture, as required in Table 2. If any one of the properties is not satisfactory, the gradation and the amount of asphalt should be readjusted to perform the test until the required performance index is satisfied.

In order to facilitate understanding of the public, the technical scheme and the technical effect of the invention are further explained and verified by an engineering embodiment as follows:

in the working example, 5-10mm coarse aggregate, 0-3mm fine aggregate and mineral powder are adopted, the screening of each grade of mineral aggregate is shown in table 9, the grading composition and the synthetic grading passing rate of each grade of mineral aggregate are shown in tables 10 and 11, and the detection index of the modified asphalt is shown in table 12.

TABLE 9 aggregate screening results

TABLE 10 design grading of each grade

TABLE 11 SOGFC-10 mixture design grading

TABLE 12 high Performance modified asphalt specification requirements

The sum SA of the specific surface areas of the synthetic grades was calculated to be 4.38m according to Table 13²Kg, the initial asphalt dosage P corresponding to the expected minimum asphalt oil film thickness of 9 mu m can be calculated reversely according to the formula 2_a4.7 percent, the dosages of the selected 3 groups of asphalts are respectively 4.7 percent, 4.9 percent and 5.1 percent, 3 groups of rotary compaction test pieces are formed, and the volume property indexes of the 3 groups of mixtures are detected as shown in table 14.

TABLE 13 surface area coefficient of aggregate

TABLE 14 bulk Properties of the blends at different bitumen loadings

According to the data in table 14, the asphalt dosage OAC1 closest to the target void ratio of 12.5% is determined to be 4.9%, the minimum asphalt content OAC2 satisfying all the volume property requirements is determined to be 4.7%, so that the optimum asphalt dosage OAC is determined to be (4.9+4.7)/2 to 4.8%, test pieces of 4.8% of optimum asphalt dosage are formed, the volume index is detected to be shown in table 15, the mixture performance is detected to be shown in table 16, the volume property requirements and the road performance requirements are both satisfied, and the design requirements of the mix proportion are completed.

TABLE 15 volume Properties of SOGFC-10 blends

TABLE 16 properties of SOGFC-10 blends

Index (I)	Unit of	Test results	Technical index	Test method
					Leakage loss of asphalt	％	0.07	≤0.1	T0732
Kent castle scatter loss	％	8.2	≤12	T0733
					Freeze-thaw split strength ratio	％	85.2	>80	T0729
Degree of dynamic stability	Sub/mm	4120	>3000	T 0719

。

Claims

1. A fine-grained semi-open-graded asphalt mixture characterized by the fact that it satisfies the requirements set forth in tables 1 and 2 below, respectively, in terms of volume properties and properties:

TABLE 1 batch volume property requirements

TABLE 2 blend Performance requirements

Wherein, the bulk density of the test piece is calculated by a volume method.

2. The fine-grained semi-open-graded asphalt mixture according to claim 1, wherein the asphalt used is a high-performance modified asphalt satisfying the technical criteria listed in table 3 below:

TABLE 3 technical index requirements for high-Performance modified asphalts

3. The fine-grained semi-open graded asphalt mixture according to claim 1, wherein the coarse aggregate used is basalt or diabase macadam with specification ranging from 5mm to 10mm, and meets the quality technical requirements listed in the following table 4:

。

4. The fine-grained semi-open graded asphalt mixture according to claim 1, wherein the fine aggregate used is limestone machine sand meeting the requirements of the following tables 5 and 6 in terms of specification and quality, respectively:

TABLE 5 Fine aggregate Specification

TABLE 6 Fine aggregate quality specifications

。

5. The fine-grained semi-open graded asphalt mixture according to claim 1, wherein the porosity is 10-15% and the paving thickness is 2.0 cm.

6. The mix proportion design method of the fine-grained semi-open-graded asphalt mixture according to any one of claims 1 to 5, comprising the following steps:

7. The method for designing the mixing ratio of the fine-grained semi-open-graded asphalt mixture according to claim 6, wherein the diameter of the molded test piece formed by rotary compaction is 100mm, the unit pressure of rotary compaction is 600Kpa, and the number of times of rotary compaction is 100.

8. As claimed in claim 6The mix proportion design method of the fine grain type semi-open graded asphalt mixture is characterized in that the proportion is more than P_aAt least two asphalts including P_a+0.2 and P_a+0.4 of the two bitumens.

9. The method for designing the mix ratio of a fine-grained semi-open-graded asphalt mixture according to claim 6, wherein the optimum gradation is determined within the gradation range shown in the following Table 7:

TABLE 7 mixture gradation design Range

。