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1、Low noise asphalt pavement Keywords: low noise; Asphalt pavement; Mix; Mix designAbstract: In order to study low noise asphalt pavement mixture gradation design method, using the aggregate gradation design and optimum asphalt content as low noise asphalt pavement mix design two major design index, a
2、dopt the token method to determine aggregate gradation design, by the means of the theoretical calculation, flow test and asphalt drop test analysis, to determine the asphalt .The best mixture asphalt content. The results show that the token method get mixture voids and target void ratio has a good
3、linear correlation, the flow test method to determine the optimum asphalt content of asphalt mixture, more accords with the practice of engineering and easy to generalize. Low noise asphalt mixture due to different from ordinary asphalt mixture, so cant use ordinary asphalt mixture design method to
4、study. Asphalt mix design, including aggregate gradation design and optimum asphalt content determine two content, and In China there is no mature experience. The design method, it is the study of the main problems need to be solved.Introduction:In recent ten years, thanks to the government increase
5、d the transportation infrastructure construction force and active investment policy, Chinas rapid development of highway construction, especially the main national highway construction has made great progress, road network is the total size and overall technical level have increased greatly. By the
6、end of 2000, the national highway mileage understanding 167. 980000 kilometers, of which grade highway 131. 590000 kilometers,The national road network density up to 17. 5 km/hundred square kilometers. The rapid development of highway construction, increase transport capacity, promote regional econo
7、mic rapid development speed, but also to the surrounding environment caused by a certain degree of pollution damage, traffic noise is one of the major pollution.Traffic noise as a kind of noise pollution, the residents of the interference in many countries has more than other forms of noise pollutio
8、n.In France, 80% of those surveyed think noise pollution in daily life the biggest cause of interference, half of which people think that traffic noise is the main noise source. Similarly, in Beijing a survey also showed that the traffic noise pollution complaints accounted for more than 55% of the
9、total noise complaints. The traffic noise pollution economic loss is difficult to accurately measure, in 1996 the European commission, says a report from the European Union countries home every year because of the loss caused by traffic noise estimates of GDP 0. 2% 2%.In China, with the rapid develo
10、pment of national economy, the appearance of a large number of new passenger and cargo traffic volume, the domestic various operating vehicles and private car society has doubled to 1990 as an example is 632. 980000 quantity, to 1999 increase to 1986. 820000 quantity. The amount of car number multip
11、lied, plus the road mileage increase, level enhancement and the improvement of the roads, certainly will bring road traffic of rapid growth, if not take effective measures, will cause the deterioration of the road noise pollution. In urban road traffic noise as an example, according to the China env
12、ironmental conditions bulletin of the data, the urban road traffic noise pollution in 2000 compared with 1999 shows ascendant trend, table 1-1 is the national 200 key city traffic noise level.Table 1-1 in 1999 and 2000, national key urban traffic noise monitoring results comparisonyearpollution leve
13、lHeavy pollution（%）Moderate pollution（%）Light pollution（%）Good（%）19995. 28. 527. 35920008. 922. 453. 315. 4In general speaking, the key urban road traffic noise pollution in mild basic state, individual main line both sides even overweight strict heavy. Beijings fourth ring road (highway standard) a
14、s an example, 2001 years of noise test results show that the average noise between day for 74. 3 77. 6 dB (A) between, night for 73. 8 77 dB (A) between. Much more than national standard day room 70 dB (A), night 55 dB (A) between the highest limit.Source to distant spread, acoustic energy with diff
15、usion distance increases; decay rate and the shape of the wave front. However, if there is a source close to the surface, it would happen, and then the surface of the sound wave reflection appear additional sound diffusion. This kind of additional sound diffusion effect in the automobile tire noise
16、diffusion process is very outstanding. When close to the source of the reflecting surface is porous structure, additional sound diffusion effect will occur in the table surface. At this time, the distance to receive the sound pressure level is direct diffusion acoustic and reflection of the sound wa
17、ve superposition effect. When the acoustic constitute the main part of the phase difference for 180 degrees occurs when the destruction of the sound wave interference, synthetic pressure decline. Tire noise in the reflection surface diffusion, damage interference occurred in high frequency sound wav
18、es part. This is because the tire noise source close to the surface (usually less than road 5 cm), sound waves and acoustic reflection of the phase difference is small, damage interference will only be possible in small wavelength acoustic (i.e., more than 8000 Hertz high frequency noise). However,
19、tire noise in pore surface diffusion propagation, due to the additional phase change, damage in low frequency interference (general for 800 1000 hz) acoustic part occurred. And this part of the sound wave is the tire noise is the main component of energy. In addition, the pore of the pavement struct
20、ure also can absorb part of the tire noise. Comprehensive the above discusses, car tire noise source mainly includes two kinds of working mechanism: 1) tire and road surface in contact closed air compression and suck out; 2) road table bump make tires produce vibration. Tire noise is spread in the r
21、eflection of sound waves superposition and damage mechanism of interference, etc.Design of the basic conditionsFunctional prerequisiteLow noise asphalt pavement, with other pavement type differences, its has a sound absorption property and water permeability and other special functions. In addition,
22、 the use of mix in addition to should have a specific target function outside, still have to meet the requirements of the durability, which means the functionality and durability, and at the same time depends on the gap mixture, so in order to ensure functionality and durability are to reach the req
23、uired standard, must be carefully selected mixing of voids.The asphalt amount, mixture of void fraction and the functional and durable sex relation model as shown in figure 1 shows. From the chart that the void fraction and the functional and durable sex relationship is instead, but there are both s
24、atisfied range. In the mix fit than design, first make sure the common voids range is very important, note meaning common range by the lower limit of functional, limit the durability of the decision. About function sex, mainly is the sound absorption properties and water permeability, etc.; Durabili
25、ty, basically be the deformation resistance and abrasion performance and mechanical properties.Practical necessary conditionsLow noise asphalt mixture, with ordinary asphalt mixture phase comparison, in resistance to peel resistance and durability is bad, which requires the voids in the meet functio
26、nal and resistance to long sex at the same time, other performance should not have practical problems.In order to get practical mixture, control the amount of asphalt add how much, is very important. In the permitted gap rate range and do not produce wrapping covering bad and flush phenomenon at the
27、 same time, to mix applied forces, get as much as possible to ensure the stability of the aggregate qualitative between cohesive force. In this way the adding amount of decision asphalt is quite necessary.Asphalt quantity to be added, void ratio and the relationship between the cohesive force betwee
28、n aggregate, as shown in figure 2 shows. When the amount of asphalt in the A1, asphalt, aggregate wrapped by the completely between bonding force extreme low. With the increase of adding amount of asphalt, asphalt, aggregate wrapped overlying become good between cohesive force is getting higher, but
29、 a smaller voids, when achieved in A2, due to the asphalt surplus, to generate flush phenomenon at the same time, the aggregate between cohesive force is also constantly decrease until doesnt work so far.Thus it can be seen, low noise asphalt mixture asphalt in addition quantity, it is graph physica
30、l line represents A1 - A2 range. But in order to ensure the stability of the mixture, it is necessary to set that aggregate it can improve the cohesive force between the asphalt adding amount of A3. Therefore, it is considered that the adding amount of asphalt in A3 - A2 range, can get practical mix
31、ture character. The lower limit of the aggregate between cohesive force, and upper limit of the produce flush now like to determine the threshold quantity. It is concluded that in low noise design of asphalt mixture, the first set must be set at the same time satisfy the functional and durability of
32、 the void fraction, and then determine can guarantee the voidage of aggregate gradation, and press the aggregate gradation determine the adding amount of asphalt.Design methodexternal factors setTo mix with the design, in addition to internal factors should be considered mixture outside, also want t
33、o consider the use place weather conditions, traffic and road width, etc. Cases such as cold snow area and hope to get abrasion resistance road area, it is necessary to consider reduce gap or use high cohesive force of the asphalt. In addition, low noise asphalt pavement due to the gap caused by blo
34、cked function decline, in addition to the outside and air void and also affected by temperature, through the vehicle number and use the viscosity of the asphalt the influence of factors. So must take to understand these factors, in the design of reflected.Voids target range analysisSet the goal of v
35、oids, must to void fraction and acoustic resistance and abrasion resistanceThe relationship between serious consideration. Asphalt mixture asphalt by factors other than adjustment empty gap rate is very difficult, but to low noise asphalt mixture with aggregate, from the pressure.Real characteristic
36、s related to the problem, the adding amount of asphalt to adjust voids andNot quite ideal. So it is necessary to take do target voids, set in a van .Within the circumference, the void fraction range of floor, ceiling respectively by functional and durability .Sure is 15% and 20%. In actual use, cons
37、ider the external factors , need to set the goal of 2% 3% floating range.Aggregate gradation selected researchIn order to meet the design with the basic principle of the two conditions, the selection of aggregate gradation. Must be very important. Because of the aggregate compaction characteristic,
38、the coarse aggregate size and shape. Shape and asphalt properties influence, in the practical work in expectation by compaction and simple test. Test methods for sure. This paper aggregate design method as is shown in table 1, according to the token method get mixture. The void fraction and target v
39、oid fraction has good linear relation. Thus it can be seen,taken method to get the coarse and fine aggregate ratio rough value, basic meet the low noise asphalt. Mix goal voids.According to the above method used to determine this topic mixture aggregate proportion see table 2The determination of the
40、 optimum asphalt additives due to the low noise asphalt mixture with large porosity, therefore, according to the Marshall test method to determine the optimum asphalt content will be difficult. And in order to take comparison, foreign and reference in this research report, combined with Chinas concr
41、ete feeling condition, decided mainly by three methods, namely:待添加的隐藏文字内容2First, the theoretical calculation of the optimum asphalt content, Marshall stability check method; Second, flow test the optimum asphalt content method; Third, asphalt drop test the optimum asphalt content method (also called
42、 Los Angeles Cephas).(1) theory to calculate the best dosage of asphalt, Marshall stability check method. Asphalt Dosage Pa for:(2) Pa = 1/48.8 * d * AGeneral film thickness take 8 10 or so. Due to the low noise asphalt mixture hole gap rate is bigger, by air, water and sunlight erosion is more seri
43、ous, and asphalt aging will be to speed up, the film thickness take 9 . To calculate the three kinds of distribution in the asphalt content (see table 3). According to the calculation of the asphalt content in the laboratory to try mixing, with the naked eye judgment asphalt content is appropriate,
44、and to adjust, then forming Marshall test, determine the porosity, and Marshall stability, flow value for check. A combination of the test results, and finally to determine the optimum asphalt content.Table 3Asphalt dosage calculation and adjustment(2) flow test the optimum asphalt content method. F
45、rom the diagram 3 can see, three kinds of distribution in the optimum asphalt content are 3. 5%. Considering China low-noise asphalt mixture has just started, there can be no many experience for reference, so with this topic research situation, the best use of asphalt quantity and the Marshall stabi
46、lity check.(3) asphalt drop test the optimum asphalt content (i.e., Los Angeles method). fromCan be seen in figure 4, 3 kinds of distribution in the optimum asphalt content each are not identical, all fell in 3. 5% 4. Between 5%.Test methods of the ratio analysisThe contrast of test methodThrough th
47、e determination of low noise asphalt mixture optimum asphalt content of the three test partyA comparative analysis of the method, we can find:(1) the theoretical calculation, the Marshall test check method. The advantage is calculation comparison simple, test verification and engineering and technic
48、al personnel familiar with the Marshall method, easy implementation, but the theoretical calculation and actual situation there are difference, main may be due to set material surface area calculation and actual production to have the deviation, and in the actual try mixing adjusted the process need
49、 experienced personnel decision, subjective factors is bigger, and low noise asphalt mixture research in China has just begun, and experienced personnel is not much, even experienced engineering and technical personnel, may also be due to human factors that do notthe optimum asphalt content with test results, so go against comparison and application.(2) flow test method. The advantage is simple, easy to test operatio
